WO2020219313A1

WO2020219313A1 - Modified zeolitic catalysts for improved conversion of paraffins by naphtha reforming

Info

Publication number: WO2020219313A1
Application number: PCT/US2020/028271
Authority: WO
Inventors: William J. KNAEBLE; Brandon J. O'NEILL; William R. GUNTHER
Original assignee: Exxonmobil Research And Engineering Company
Priority date: 2019-04-26
Filing date: 2020-04-15
Publication date: 2020-10-29

Abstract

This application relates to methods and systems for the conversion of a hydrocarbon feedstock, in particular, naphtha feedstock, into a hydrocarbon product stream containing a high yield of high-octane gasoline and/or chemicals products (e.g., benzene, toluene, and xylene). The conversion may be carried out by using a modified zeolitic catalyst, prepared by treating a precursor zeolite acid and/or steam to modify the bulk and/or framework silica-to-alumina ratio. A modified zeolite may then be used to convert a hydrocarbon stream by contacting a hydrocarbon feed stream with the modified zeolitic catalyst under conditions effective to convert the hydrocarbon feed stream to a hydrocarbon product stream comprising one or more of a gasoline fraction, benzene, toluene, xylene, and blends thereof. Also provided herein are systems for using a modified zeolitic catalyst for converting hydrocarbons.

Description

MODIFIED ZEOLITIC CATALYSTS FOR IMPROVED CONVERSION OF

PARAFFINS BY NAPHTHA REFORMING

BACKGROUND

[0001] This application relates to methods and systems for the conversion of hydrocarbon feedstocks, in particular, naphtha feedstocks, into product streams containing a high yield of high- octane gasoline and chemicals products (e.g., benzene, toluene, and xylenes). In particular, the modified zeolitic catalysts disclosed herein may be tailored to enhance dehydrocyclization of paraffins, thus more effectively reforming paraffinic feeds than conventional reforming catalysts.

[0002] Naphtha reforming has been an important refining process for decades, generating hydrogen, chemicals feedstock (benzene, toluene, xylenes, which are also known as BTX), and high-octane gasoline. A typical naphtha feedstock will contain paraffins, olefins, naphthenes, aromatics, and isomers thereof. To reform a typical naphtha feedstock into gasoline and/or BTX, a reforming catalyst converts these molecules into aromatic hydrocarbons. Gasoline may additionally include isoparaffins; however, isoparaffins contribute much less than aromatics to the octane number of gasoline and do not contribute to BTX yield at all. A gasoline fraction derives even less contribution to its octane rating from paraffins and naphthenes.

[0003] To carry out the necessary reforming reactions, reforming catalysts typically include a metal (e.g., platinum) to dehydrogenate and an acid function to dehydrocyclize. However, the paraffin dehydrocyclization reaction to generate aromatic hydrocarbons is not particularly favored by conventional reforming catalysts and conversion is often slow and/or incomplete.

[0004] Metal-doped chlorided alumina is the most common reforming catalyst; however, chlorided alumina has its limitations. For example, chlorided alumina catalysts tend to favor paraffin isomerization at the expense of paraffin dehydrocyclization, which is undesirable since isoparaffins do not contribute to the octane number of a gasoline product. Metal-doped chlorided alumina, however, is good at dehydrogenation. Therefore, feedstocks best suited for chlorided alumina catalysts are typically limited to those having a low paraffin content and a higher naphthene content and aromatic content.

[0005] Chlorided alumina catalysts may also be negatively affected by chemical impurities in a feedstock. For example, basic nitrogen in a feedstock will react with the chloride in a chlorided alumina catalyst, effectively stripping the catalyst of its acidity (and activity), but also forming a compound (chloramine) that is corrosive to the reforming system. Finally, but not least importantly, chlorided alumina catalysts are susceptible to deactivation by coking, particularly under operating conditions most suited to forming a high-octane product stream. As coke accumulates, it blocks active sites that catalyze reforming reactions, leading to reduced product yields.

[0006] To overcome some of these limitations, zeolitic catalysts have been investigated for their use in reforming, though in a limited manner. Advantageously, zeolitic catalysts may be modified to resist coking and, due to their permanent acid functionality, do not require the addition of chloride to the system. However, much of the catalytic activity in zeolitic catalysts takes place in the pores of the zeolite. Thus, the selectivity and activity of the catalyst are highly dependent on the mass diffusion of the hydrocarbons from the feedstock into and out of the pores of the catalyst. Larger molecules are difficult to convert, as their size excludes them from entering the pore. Consequently, zeolitic catalysts (e.g., Pt/Re zeolites) are best suited for reforming feedstocks that are limited to smaller hydrocarbons that easily diffuse in and out of the pores of the zeolite. However, smaller hydrocarbons, such as C1-C5 hydrocarbons, are also not desirable in a feedstock, as these are not readily converted to aromatics. Thus, presently, the preferred feedstock for a zeolitic catalyst is generally limited to C6-C7 feedstock (as opposed to a full-range C4-C12 feedstock). A C6-C7 feedstock, in turn, produces a hydrocarbon product stream limited to primarily benzene and toluene products.

[0007] What is needed is a reforming system that can effectively convert full-range (C4-C12) hydrocarbon feedstocks with widely varying dispositions, in particular, having a significant paraffinic fraction, into a hydrocarbon product stream characterized by a high octane number and/or having high chemicals yield.

SUMMARY

[0008] This application relates to methods and systems for the conversion of hydrocarbon feedstocks, in particular, naphtha feedstocks, into hydrocarbon product streams containing a high yield of high-octane gasoline and chemicals products (e.g., benzene, toluene, and xylenes). In particular, the modified zeolitic catalysts disclosed herein may be modified to enhance dehydrocyclization of paraffins, thus more effectively reforming paraffinic feeds when compared to conventional reforming catalysts

[0009] Provided herein are methods that include a method for converting hydrocarbons comprising: treating a precursor zeolite having a bulk silica-to-alumina ratio and a framework silica-to-alumina ratio with one or more of acid, steam, and a combination thereof under conditions effective to increase one or more of the bulk silica-to-alumina ratio and framework silica-to- alumina ratio to at least about 40: 1 to prepare a modified zeolite; and contacting the modified zeolite with a transition metal to form a modified zeolitic catalyst having enhanced dehydrocyclization activity as compared to the precursor zeolite. [0010] Also provided herein is a method of preparing a modified zeolitic catalyst comprising: doping a precursor zeolite with a Group 1 metal cation, a Group 2 metal cation, or a combination thereof, to form a metal-doped zeolite; treating the metal-doped zeolite with one of the following: acid, steam, and a combination thereof, to form a modified zeolite; and contacting the modified zeolite with a transition metal to form a modified zeolitic catalyst having enhanced dehydrocyclization activity. In some embodiments, a modified zeolite may then be used to convert a hydrocarbon feedstream by contacting a hydrocarbon feed stream with the modified zeolitic catalyst under conditions effective to convert the hydrocarbon feed stream to a hydrocarbon product stream comprising one or more of a gasoline fraction, benzene, toluene, xylene, and blends thereof.

[0011] Also provided herein are systems for converting hydrocarbons including a system comprising: a hydrocarbon feed stream inlet configured and arranged to receive a hydrocarbon feed stream; at least one reactor comprising at least one catalyst bed, the catalyst bed comprising at least one modified zeolitic catalyst, wherein the modified zeolitic catalyst comprises a transition metal and a modified zeolite characterized by one or more of the following: a bulk silica-to-alumina ratio of at least about 40: 1 and a framework silica-to-alumina ratio of at least about 40:1; and a hydrocarbon product stream outlet configured and arranged to receive a hydrocarbon product stream.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The following figures are included to illustrate certain aspects of the embodiments, and should not be viewed as exclusive embodiments. The subject matter disclosed is capable of considerable modifications, alterations, combinations, and equivalents in form and function, as will occur to those skilled in the art and having the benefit of this disclosure.

[0013] FIG. 1 depicts an example of a system described herein for converting a hydrocarbon feed stream.

[0014] FIG. 2 provides an example IR spectra of absorbed pyridine on one embodiment of a steamed modified zeolitic catalysts and several embodiments of modified zeolitic catalysts doped with a Group 1 or Group 2 metal cation, as discussed below in the Examples.

[0015] FIG. 3 provides data illustrating improved aromatic yield under equivalent LPG yield when using a modified zeolitic catalyst as described herein compared to a Pt/Re chlorided alumina catalyst, as discussed below in the Examples.

[0016] FIG. 4 provides data illustrating improved C5+ fraction yield under equivalent C5+ fraction RON when using a modified zeolitic catalyst as described herein compared to a Pt/Re chlorided alumina catalyst, as discussed below in the Examples. [0017] FIG. 5 provides data illustrating improved aromatics yield under equivalent C5+ fraction RON when using a modified zeolitic catalyst as described herein compared to a Pt/Re chlorided alumina catalyst, as discussed below in the Examples.

[0018] FIG. 6 provides data illustrating improved BTX yield under equivalent C5+ fraction RON when using a modified zeolitic catalyst as described herein as compared to a Pt/Re chlorided alumina catalyst, as discussed below in the Examples.

[0019] FIG. 7 provides data illustrating improved A6-A8 yield under equivalent C5+ fraction RON using a modified zeolitic catalyst as described herein compared to a Pt/Re chlorided alumina catalyst, as discussed below in the Examples.

[0020] FIG. 8 provides data illustrating the effect of length of steam treating of a precursor zeolite on C5+ fraction yield under equivalent C5+ fraction RON, as discussed below in the Examples.

[0021] FIG. 9 provides data illustrating the effect of length of steam treating of a precursor zeolite on C5 + G, cyclic hydrocarbon yield under equivalent C5+ fraction RON, as discussed below in the Examples.

[0022] FIG. 10 provides data illustrating decreased C1-C4 fraction yield when a modified zeolitic catalyst comprises a Group 1 or Group 2 metal cation as compared to a modified zeolitic catalyst absent a Group 1 or Group 2 metal cation, as discussed below in the Examples.

[0023] FIG. 11 provides data illustrating increased aromatic yield (toluene in an n-heptane feed) when a modified zeolitic catalyst comprises a Group 1 or Group 2 metal cation as compared to a modified zeolitic catalyst absent a Group 1 or Group 2 metal cation, as discussed below in the Examples.

[0024] FIG. 12 provides data illustrating increased C5 + Ce cyclic hydrocarbon yield under equivalent C5+ fraction RON when a modified zeolitic catalyst comprises a Group 1 or Group 2 metal cation as compared to a modified zeolitic catalyst absent a Group 1 or Group 2 metal cation, as discussed below in the Examples.

[0025] FIG. 13 provides data illustrating increased C5 + G, cyclic hydrocarbon yield under equivalent C 1-C4 fraction yield when a modified zeolitic catalyst comprises magnesium as compared to a modified zeolitic catalyst absent magnesium, as discussed below in the Examples.

[0026] FIG. 14 provides data illustrating a modified zeolitic catalyst’s resistance to coking compared to a Pt/Re chlorided catalyst, as discussed below in the Examples.

[0027] FIG. 15 provides data illustrating a modified zeolitic catalyst’s resistance to coking compared to a Pt/Re chlorided catalyst, as discussed below in the Examples.

[0028] FIG. 16 provides data illustrating the resistance of a modified zeolitic catalyst, as described herein, to deactivation at more severe operating conditions (215 psig (1480 kPa), thiHC ratio = 2.5: 1) as compared to a Pt/Re chlorided alumina catalyst, as discussed below in the Examples.

[0029] FIG. 17 provides data illustrating improved product stream RON resulting from using a modified zeolitic catalyst, as described herein, under more severe operating conditions (150 psig (1030 kPa), FhiHC ratio = 1.5:1), as discussed below in the Examples.

[0030] FIG. 18 provides data illustrating improved C5+ fraction yield resulting from using a modified zeolitic catalyst, as described herein, under more severe operating conditions (150 psig (1030 kPa), H2:HC ratio = 1.5:1), as discussed below in the Examples.

[0031] FIG. 19 provides data illustrating improved BTX yield resulting from using a modified zeolitic catalyst under decreased reactor pressure, as discussed below in the Examples.

[0032] FIG. 20 provides data illustrating improved BTX yield resulting from using a modified zeolitic catalyst under various H2:HC feed ratios, as discussed below in the Examples.

[0033] FIG. 21 provides data illustrating decreased ethylbenzene yield under equivalent C5+ fraction RON using a modified zeolitic catalyst as described herein compared to a Pt/Re chlorided alumina catalyst, as discussed below in the Examples.

DETAILED DESCRIPTION

[0034] This application relates to methods and systems for the conversion of hydrocarbon feedstocks, in particular, naphtha feedstocks, into hydrocarbon product streams containing a high yield of high-octane gasoline and chemicals products (e.g., benzene, toluene, and xylene). In particular, the modified zeolitic catalysts disclosed herein may be modified to enhance dehydrocyclization of paraffins, thus more effectively reforming paraffinic feeds when compared to conventional reforming catalysts.

[0035] To facilitate an understanding of the present invention, a number of terms and phrases are defined below and in the following text.

[0036] For purposes of this disclosure and the claims hereto, the numbering scheme for the Periodic Table Groups is according to the IUPAC Periodic Table of Elements (Dec 1, 2018).

[0037] As used in the present disclosure and claims, the singular forms“a,”“an,” and“the” include plural forms unless the context clearly dictates otherwise.

[0038] The term“and/or” as used in a phrase such as“A and/or B” herein is intended to include “A and B”,“A or B”,“A”, and“B”.

[0039] Alpha value is an approximate indication of the catalytic cracking activity of a catalyst compared to a standard catalyst and gives the relative rate constant (rate of normal hexane conversion per volume of catalyst per unit time). It is based on the activity of silica- alumina cracking catalyst having an alpha value of 1 (Rate Constant = 0.016 s ¹). The alpha test is described in U.S. Pat. No. 3,354,078; in the Journal of Catalysis, 4, 527 (1965); 6, 278 (1966); and 61, 395 (1980), each incorporated herein by reference with respect to its disclosure of how to carry out the alpha test. The experimental conditions of the test used herein include a constant temperature of 1000°F (537.8°C) and a variable flow rate as described in detail in the Journal of Catalysis, 61, 395 (1965). The effluent product stream may be analyzed by vapor chromatography.

[0040] Collidine uptake can be determined as the micromoles of collidine absorbed per gram of sample that is dried under nitrogen flow at 200°C for 60 minutes on a Thermogravimetric Analyzer (Model Q5000), manufactured by TA Instruments, New Castle, Delaware). After drying the sample, the collidine can be sparged over the sample. The collidine uptake can then be calculated from the following formula: (weight of sample after sparging with collidine - weight of dried sample x 10⁶ ÷ (molecular weight of collidine x weight of dried sample). As used herein, “collidine uptake” refers to an uptake calculated after sparging the sample for 60 minutes at a collidine partial pressure of 3 torr (~ 400 kPa).

[0041] As used herein, and unless otherwise specified, the term“hydrocarbon” means a class of compounds containing hydrogen bound to carbon, and encompasses saturated hydrocarbons, unsaturated hydrocarbons, and mixtures thereof, including mixtures of hydrocarbons having different values of n.

[0042] As used herein, and unless otherwise specified, the term“Cn” means hydrocarbon(s) having n carbon atom(s) per molecule, wherein n is a positive integer. As used herein, and unless otherwise specified, the term“Cn+” refers to a hydrocarbon composition defined by hydrocarbons having“n” or more carbon atoms, where“n” is an integer greater than 0. This includes paraffins, olefins, cyclic hydrocarbons, and aromatics and isomers thereof. Similarly, the term“Cn-” refers to a hydrocarbon composition defined by hydrocarbons having“n” or fewer carbon atoms, wherein “n” is an integer greater than 0. This includes paraffins, olefins, cyclic hydrocarbons, aromatics, and isomers thereof.

[0043] As used herein, and unless otherwise specified, the term“Cn” means hydrocarbon(s) having n carbon atom(s) per molecule, wherein n is a positive integer. As used herein, and unless otherwise specified, the term“Cn+” refers to a hydrocarbon composition defined by hydrocarbons having“n” or more carbon atoms, where“n” is an integer greater than 0. This includes paraffins, olefins, cyclic hydrocarbons, and aromatics and isomers thereof. Similarly, the term“Cn-” refers to a hydrocarbon composition defined by hydrocarbons having“n” or fewer carbon atoms, wherein “n” is an integer greater than 0. This includes paraffins, olefins, cyclic hydrocarbons, aromatics, and isomers thereof.

[0044] As used herein, and unless otherwise specified, liquid petroleum gas (“LPG”) refers to a hydrocarbon composition, for example, a fraction of the hydrocarbon product stream, comprising propane and butane (including n-butane and iso-butane).

[0045] As used herein, and unless otherwise specified, the term “aromatic” refers to unsaturated cyclic hydrocarbons having a delocalized conjugated p system and having from six to thirty carbon atoms (e.g., aromatic C6-C30 hydrocarbon). Examples of suitable aromatics include, but are not limited to benzene, toluene, xylenes, mesitylene, ethylbenzenes, cumene, naphthalene, methylnaphthalene, dimethylnaphthalenes, ethylnaphthalenes, acenaphthalene, anthracene, phenanthrene, tetraphene, naphthacene, benzanthracenes, fluoranthrene, pyrene, chrysene, triphenylene, and the like, and combinations thereof. Additionally, an aromatic may comprise one or more heteroatoms. Examples of heteroatoms include, but are not limited to, nitrogen, oxygen, and/or sulfur. Aromatics with one or more heteroatom include, but are not limited to thiophene, benzothiophene, oxazole, thiazole and the like, and combinations thereof. An aromatic may comprise monocyclic, bicyclic, tricyclic, and/or polycyclic rings (in any embodiment, at least monocyclic rings, only monocyclic and bicyclic rings, or only monocyclic rings) and may be fused rings. As used herein, the plural use of“xylenes” and grammatical variations thereof is used to convey that the xylene may be any isomer of xylene, including m-xylene, o-xylene, p-xylene, or any blend thereof.

[0046] As used herein“An” where n is an integer, refers to an aromatic hydrocarbon comprising“n” number of carbons in the aromatic ring. For example, an A8 fraction includes all aromatics having eight carbons in the aromatic ring structure. Likewise, A6 refers to aromatic hydrocarbon having six carbons in the aromatic ring structure.

[0047] As used herein, the term“olefin,” alternatively referred to as“alkene,” and grammatical derivatives thereof, refers to an unsaturated hydrocarbon chain of two to about twelve carbon atoms in length containing at least one carbon-to-carbon double bond. An olefin may be straight chain or branched chain. Non-limiting examples include ethylene, propylene, butylene, and pentene. “Olefin” is intended to embrace all structural isomeric forms of olefins.

[0048] As used herein, and unless otherwise specified, the term“paraffin,” alternatively referred to as“alkane,” and grammatical derivatives thereof, refers to a saturated hydrocarbon chain of one to about thirty carbon atoms in length, such as, but not limited to methane, ethane, propane and butane. A paraffin may be straight-chain, cyclic or branched-chain.“Paraffin” is intended to embrace all structural isomeric forms of paraffins. The term“acyclic paraffin” refers to straight-chain or branched-chain paraffins. The term“isoparaffin” refers to branched-chain paraffins and the term“n-paraffm” or“normal paraffin” refers to straight-chain paraffins.

[0049] As used herein, the term“full-range naphtha” and grammatical derivatives thereof, refers to a middle boiling range hydrocarbon fraction or fractions, typically including three or more hydrocarbons (e.g., between four and twelve carbon atoms), which are major components of gasoline, and having a boiling range characterized by a T5-T95 range of 10°C to 232°C, where T5 defines the temperature at which 5% of the hydrocarbon composition boils and T95 defines the temperature at which 95% of the hydrocarbon composition boils. Boiling range may be determined by simulated distillation (“SimDis”) according to ASTM D2887-18. Full-range naphtha comprises “light” naphtha and“heavy” naphtha. Light naphtha is a lighter fraction of full-range naphtha having a T95 boiling point less than about 90°C. The fraction of full-range naphtha having a T5 boiling point greater than about 90°C is considered heavy naphtha. Unless otherwise specified, full-range naphtha refers to a composition comprising both heavy and light naphtha.

[0050] Unless otherwise specified,“naphtha,” (and grammatical variations thereof) refers to a composition that falls within the boiling point range boundaries of full-range naphtha and may have the same T5-T95 range as full-range naphtha or may have different T5 and/or T95 temperatures than full-range naphtha. Naphtha may comprise full-range naphtha, light naphtha, heavy naphtha, or any other contemplated fraction defined by a subset of hydrocarbons having, for example, a defined T5 and/or T95 temperature, a defined molecular weight range, a defined number of hydrocarbons, and the like. Naphtha may include paraffins, olefins, naphthenes, and/or aromatics.

[0051] As used herein,“feedstock” and“feed” (and grammatical derivatives thereof) are used interchangeably and both refer to a composition that is fed into a reforming reactor. A feedstock may optionally have been pre-treated to modify its disposition.

[0052] As used herein,“reactor,” and grammatical derivatives thereof, refers to a vessel comprising one or more catalyst beds. A reactor inlet refers to a conduit that conveys a hydrocarbon stream to that reactor. Unless specified otherwise, all reactor temperatures refer to an equivalent isothermal (El) temperature. Experiments in the Examples are performed in an isothermal reactor having a defined inlet temperature. Commercial reactors, however, are typically adiabatic and reactor temperature is controlled in a different manner. In adiabatic reactors, a temperature profiled may be specified that results in an average temperature across the entire reactor equivalent to a specified isothermal reactor temperature.

[0053] As used herein, the term“straight run naphtha” (also termed“virgin naphtha”) refers to petroleum naphtha obtained directly from fractional distillation. As used herein, the term“fluid catalytic cracker (FCC) naphtha” refers to naphtha produced by the well-known process of fluid catalytic cracking. The term“FCC naphtha” is intended to encompass one or more of light cut naphtha (LCN), intermediate cut naphtha (ICN), and heavy cut naphtha (HCN). As used herein, the term“coker naphtha” refers to naphtha produced by the well-known process of coking in one or more coker units or cokers. Coker naphtha generally includes more sulfur and/or nitrogen than straight run naphtha. As used herein, the term“delayed coker naphtha” refers to naphtha produced by the well-known process of delayed coking. As used herein, the term“fluid coker naphtha” refers to naphtha produced by the well-known process of fluid coking. As used herein, the term “hydrocrackate” refers to a naphtha cut of a hydrocracker byproduct. As used herein, the term “hydrotreated naphtha” refers to naphtha produced by the well-known process of hydrotreating. As used herein, the term“steam cracker naphtha (SCN)” refers to naphtha produced by the well- known process of steam cracking.

[0054] A common method for characterizing the octane rating of a composition is to use Research Octane Number (RON). As used herein, “octane rating” and “RON” are used interchangeably, and both refer to the RON of the C5+ fraction of a hydrocarbon product stream. Although various methods are available for determining RON, in the claims below, references to Research Octane Number (RON) correspond to RON determined as described in Ghosh, P. et al. (2006)“Development of Detailed Gasoline Composition-Based Octane Model,” Ind. Eng. Chem. Res., 45(1), pp 337-345. As used herein,“high octane” is meant to describe a hydrocarbon composition having a RON of at least about 80, at least about 85, at least about 90, at least about 95, at least about 99, or about 100; or in a range of about 80 to about 100, about 90 to about 100, or about 95 to about 100. RON is used herein, particularly in the Examples, as a surrogate for conversion. In any reforming reaction, a higher RON can be achieved by pushing the reaction forward with more severe operating conditions or longer run times. However, in doing so, the yield of desirable products in a hydrocarbon product stream is sacrificed. Thus, advantages are realized here in the simultaneous production of a hydrocarbon product stream having a high yield of desirable products (e.g., C5+ hydrocarbons, aromatics) and that desirable fraction having a high octane-rating (RON).

[0055] The relative paraffin, aromatic, and naphthene content of a hydrocarbon feedstock may be described by its N+2A value, which is the naphthene content (wt. %) plus twice the aromatic content (wt. %). A higher N+2A value will have more naphthenes and aromatics where as a lower N+2A number will have more paraffins.

[0056] As used herein, the term“conditions effective to” refers to conditions to which a hydrocarbon feed stream may be subjected that results in a hydrocarbon product stream having a desired yield and/or octane rating. Conditions may include temperature, pressure, reaction time, and the like, which are conditions known to those of ordinary skill in the art with benefit of this disclosure.

[0057] Advantages of the modified zeolitic catalysts described herein are apparent in an increased yield of desired products or product fractions in a hydrocarbon product stream derived from a modified zeolitic catalyst. As used herein, and unless otherwise specified,“percent yield” or“yield” is the total weight of the specified product divided by the total weight of the hydrocarbon feed stream and converted to a percent.

[0058] As used herein, the term“coke,” and grammatical derivatives thereof, refers to carbonaceous material that deposits on the surface, including within the pores, of a catalyst (e.g., a modified zeolitic catalyst). Formation of coke on a catalyst’s surface decreases the availability of active sites for the reforming reactions to take place. Thus, as coke builds up over time, the quality of a resulting hydrocarbon product stream may decrease. Measures of hydrocarbon product stream quality (e.g., octane rating, yield) are used herein as an indirect measure of coke formation on a modified zeolitic catalyst.

[0059] Unless otherwise indicated, all numbers expressing quantities of ingredients, properties such as molecular weight, reaction conditions, and so forth used in the present specification and associated claims are to be understood as being modified in all instances by the term“about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the desired properties sought to be obtained by the embodiments of the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claim, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

[0060] One or more illustrative embodiments incorporating the invention embodiments described herein are presented herein. Not all features of a physical implementation are described or shown in this application for the sake of clarity. It is understood that in the development of a physical embodiment incorporating the embodiments of the present invention, numerous implementation-specific decisions must be made to achieve the developer's goals, such as compliance with system-related, business-related, government-related and other constraints, which vary by implementation and from time to time. While a developer’s efforts might be time- consuming, such efforts would be, nevertheless, a routine undertaking for those of ordinary skill in the art and having benefit of this disclosure.

[0061] While compositions and methods are described herein in terms of“comprising” various components or steps, the compositions and methods may also“consist essentially of’ or“consist of’ the various components and steps.

Methods and Systems for Converting Hydrocarbons

[0062] Methods and systems for converting hydrocarbons are provided herein that utilize one or more modified zeolitic catalysts to convert a hydrocarbon feed stream to a hydrocarbon product stream. Advantageously, and surprisingly, the dehydrocyclization activity of zeolitic catalyst may be tuned by adjusting its framework and/or bulk silica-to-alumina ratio. For example, by increasing a zeolite’s framework and bulk silica-to-alumina ratio, a modified zeolitic catalyst having selectivity for dehydrocyclization over other various reforming reactions (e.g., isomerization, cracking) may be formed. Further, a modified zeolitic catalyst prepared as disclosed herein may display reduced cracking activity when compared to a conventional reforming catalyst. By using the systems and methods disclosed herein, a hydrocarbon feed stream comprising paraffins (which are typically viewed as undesirable) may be converted to highly valued products by minimizing unwanted cracking and isomerization reactions.

[0063] Provided herein are methods that include a method for converting hydrocarbons comprising: treating a precursor zeolite having a bulk silica-to-alumina ratio and a framework silica-to-alumina ratio with one or more of acid, steam, and a combination thereof under conditions effective to increase one or more of the bulk silica-to-alumina ratio and framework silica-to- alumina ratio to at least about 40:1 to prepare a modified zeolite; and contacting the modified zeolite with a transition metal to form a modified zeolitic catalyst having enhanced dehydrocyclization activity as compared to the precursor zeolite.

[0064] Also provided herein is a method of preparing a modified zeolitic catalyst comprising: doping a precursor zeolite with a Group 1 metal cation, a Group 2 metal cation, or a combination thereof, to form a metal-doped zeolite; treating the metal-doped zeolite with one of the following: acid, steam, and a combination thereof, to form a modified zeolite; and contacting the modified zeolite with a transition metal to form a modified zeolitic catalyst having enhanced dehydrocyclization activity.

[0065] A modified zeolite may then be used to convert a hydrocarbon stream by contacting a hydrocarbon feed stream with the modified zeolitic catalyst under conditions effective to convert the hydrocarbon feed stream to a hydrocarbon product stream comprising one or more of a gasoline fraction, benzene, toluene, xylene, and blends thereof.

[0066] Also provided herein are systems for converting hydrocarbons including a system comprising: a hydrocarbon feed stream inlet configured and arranged to receive a hydrocarbon feed stream; at least one reactor comprising at least one catalyst bed, the catalyst bed comprising at least one modified zeolitic catalyst, wherein the modified zeolitic catalyst comprises a transition metal and a modified zeolite characterized by one or more of the following: a bulk silica-to-alumina ratio of at least about 40: 1 and a framework silica-to-alumina ratio of at least about 40:1; and a hydrocarbon product stream outlet configured and arranged to receive a hydrocarbon product stream.

Modified Zeolitic Catalysts for Use in the Disclosed Methods and Systems

[0067] The modified zeolitic catalysts for use in the methods and systems described herein includes a modified zeolite and at least one transition metal.

[0068] A modified zeolitic catalyst as disclosed herein may be prepared from a zeolite, herein referred to as a“precursor zeolite” or a“zeolite.” As used herein,“precursor zeolite,”“zeolite,” or “zeolitic” (and grammatical variations thereof) are defined to refer to a crystalline material having a porous framework structure built from tetrahedral atoms connected by bridging oxygen atoms. A precursor zeolite is modified to produce a modified zeolite as described herein, which is subsequently converted to a modified zeolitic catalyst disclosed herein. Thus, the modified zeolites are precursor zeolites that have been treated in such a way that the one or more of the bulk silica- to-alumina ratio and framework silica-to-alumina ratio is increased relative to the precursor zeolite bulk silica-to-alumina ratio and framework silica-to-alumina ratio.

[0069] Examples of known zeolite frameworks are given in the“Atlas of Zeolite Frameworks” published on behalf of the Structure Commission of the International Zeolite Association”, 6^th revised edition, Ch. Baerlocher, L.B. McCusker, D.H. Olson, eds., Elsevier, New York (2007) and the corresponding web site, http://www.iza-structure.org/databases, each which is incorporated by reference herein with respect to its disclosure of zeolitic frameworks and methods for their preparation. Under this definition, a zeolite can refer to aluminosilicates having a zeolitic framework type as well as crystalline structures containing oxides of heteroatoms different from silicon and aluminum. Such heteroatoms can include any heteroatom generally known to be suitable for inclusion in a zeolitic framework, such as gallium, boron, germanium, phosphorus, zinc, antimony, tin, and/or other transition metals that can substitute for silicon and/or aluminum in a zeolitic framework. A zeolite may be referred to by the number of tetrahedral atoms (exclusive of oxygen atoms) that define pore openings in the zeolite. For example, a precursor zeolite may be an 8-member ring zeolite, a 10-member ring zeolite, or a 12-member ring zeolite. Preferably, a precursor zeolite is a 12-member ring zeolite. A precursor zeolite may be a three-dimensional zeolite. Examples of suitable precursor zeolites include zeolites having a FAU, LTL, BEA, MAZ, MTW, MEI, MOR, or EMT-FAU intermediate framework structure. Examples of suitable precursor zeolites having an FAU framework structure include, but are not limited to, USY (or dehydrated USY), Na-X (or dehydrated Na-X), LZ-210, Li-LSX, zeolite X, and zeolite Y. Examples of suitable precursor zeolites having an LTL framework structure include, but are not limited to, zeolite L, gallosillicate L, LZ-212 and perlialite. Examples of suitable precursor zeolites having a BEA framework structure include, but are not limited, to Beta, Al-rich Beta, CIT-6, and pure silica Beta. Examples of suitable precursor zeolites having an MAZ framework structure include, but are not limited to, mazzite, LZ-202, and ZSM-4. Examples of suitable precursor zeolites having an MTW framework structure include, but are not limited to, ZSM-12, CZH-5, NU-13, TPZ-12, Theta-3, and VS-12. Examples of suitable precursor zeolites having an MEI framework structure include, but are not limited to, ZSM-18 and ECR-40. Examples of suitable precursor zeolites having an MOR framework structure include, but are not limited to, Ca-Q, LZ-211, mordenite, and Na-D. Examples of suitable precursor zeolites having an EMT-FAU intermediate structure include, but are not limited to, CSZ-1, ECR-30, ECR-32, ZSM-20, and ZSM-3. A precursor zeolite may be a zeolite L, zeolite Y, or USY. A person of ordinary skill in the art knows how to make the aforementioned frameworks.

[0070] Zeolites, being an aluminosilicate material, have a framework sibca-to-alumina ratio and bulk sibca-to-alumina ratio. As used herein,“bulk silica-to-alumina ratio” refers to the sibca- to-alumina ratio of a zeolite inclusive of alumina within and outside the framework (extra framework alumina). As used herein,“framework sibca-to-alumina ratio” refers to the sibca-to- alumina ratio of a zeolite of tetrahedrally coordinated alumina within the framework and exclusive of alumina outside the framework (extra-framework alumina, which is typically octahedrally coordinated). The bulk silica-to-alumina ratio, framework silica-to-alumina ratio, and extra framework metal oxide content, unless otherwise indicated, are measured on a modified zeolitic catalyst (defined below) after all modifications, for example, after steaming, silicone selectivation, and/or acid/base washing of a precursor zeolite. Framework silica-to-alumina ratio may be measured by solid state NMR. Bulk silica-to alumina ratio may be measured by any elemental analysis technique, for example, inductively coupled plasma atomic emission spectroscopy or inductively coupled plasma mass spectrometry.

[0071] Processes for producing modified zeolites include, for example, steaming a precursor zeolite. In such processes, a precursor zeolite may be steamed in an atmosphere comprising steam at a temperature of about 750°F (398.9°C) to about 3000°F (1649°C), about 1000°F (537.8°C) to about 2000°F (1093°C), or about 1500°F (815.6°C) to about 1800°F (982.2°C). The atmosphere can include as little as about 1 vol. % water and up to about 100 vol. % water. A precursor zeolite can be exposed to steam for any convenient period of time, such as about 10 minutes to about 48 hours. In particularly useful examples, a precursor zeolite is steamed for about 1 hour to about 5 hours at a temperature of about 1500°F (815.6°C) to about 1800°F (982.2°C), which includes about 1500°F (815.6°C), about 1600°F (871.1°C), about 1700°F (926.7°C), and about 1800°F (982.2°C).

[0072] A precursor zeolite may be steamed multiple times, if desired, to produce a modified zeolite. If steamed multiple times, each steam treatment can occur with other steps performed between steam treatments, for example, acid washing. Typical acid leaching conditions can include using a suitable acid, such oxalic acid, citric acid, or nitric acid, in concentrations ranging from about 0.1 molar up to about 10 molar, preferably about 1 molar, at a temperature ranging from about 20°C up to about 100°C.

[0073] Advantageously, a modified zeolitic catalyst may favor paraffin dehydrocyclization over other reforming reactions such as, but not limited to, isomerization, cracking, and dealkylation. Enhanced selectivity for paraffin dehydrocyclization may be imparted to a modified zeolitic catalyst by adjusting the framework and/or bulk silica-to-alumina ratio of the precursor zeolite from which the modified zeolitic catalyst is derived. A modified zeolite suitable for preparing a modified zeolitic catalyst may have a high bulk silica-to-alumina ratio, for example, at least about 40: 1 ( e.g ., about 40: 1 to about 10000: 1), at least about 80: 1 ( e.g ., about 80: 1 to about 10000: 1), at least about 350: 1 (e.g., about 350: 1 to about 10000: 1), or at least about 400: 1 (e.g., about 400: 1 to about 10000: 1). A modified zeolite may have a high framework silica-to-alumina ratio, for example, at least about 80: 1 (e.g. , about 80: 1 to about 20000: 1), at least about 500: 1 (e.g. , about 500: 1 to about 20000: 1), or at least about 2000:1 (e.g., about 2000:1 to about 20000: 1). Preferably, a modified zeolite has a framework silica-to-alumina ratio of at least about 500: 1 or about 2000: 1.

[0074] A modified zeolite may be treated with a source of one or more transition metals to form a modified zeolitic catalyst described herein. A modified zeolitic catalyst may include at least about 0.01 wt. %, at least about 0.05 wt. %, at least about 0.25 wt. %, at least about 1 wt. %, at least about 2.5 wt. %, at least about 5 wt. %, at least about 10 wt. %, or in a range from about 0.01 wt. % to about 10 wt. %, about 0.01 wt. % to about 5.0 wt. %, 0.01 wt. % to 2.5 wt. %, about 0.01 wt. % to about 1 wt. %, about 0.01 wt. % to about 0.25 wt. %, about 0.01 wt. % to about 0.05 wt. %, about 0.05 wt. % to about 10 wt. %, about 0.05 wt. % to about 5.0 wt. %, about 0.05 wt. % to about 2.5 wt. %, about 0.05 wt. % to about 1 wt. %, about 0.05 wt. % to about 0.25 wt. %, about 0.25 wt. % to 10 wt. %, about 0.25 wt. % to about 5 wt. %, about 0.25 wt. % to about 1 wt. %, about 1 wt. % to about 10 wt. %, about 1 wt. % to about 5 wt. %, about 1 wt. % to about 2.5 wt. %, about 2.5 wt. % to about 10 wt. %, about 2.5 wt. % to about 5 wt. %, or about 5 wt. % to about 10 wt. % transition metal, based on the total weight of the modified zeolitic catalyst. For example, a modified zeolitic catalyst may include about 0.9 wt. % of a transition metal. The transition metal may be a Group 10 transition metal, for example, nickel (Ni), palladium (Pd), platinum (Pt), or a combination thereof. Suitable sources of platinum include, but are not limited to, tetraamine platinum (II) nitrate, tetraamine platinum hydroxide, chloroplatinic acid, and the like. Typical methods for incorporation of a metal include impregnation (such as by incipient wetness), ion exchange, deposition by precipitation, and any other convenient method for depositing a metal.

[0075] Optionally, a modified zeolitic catalyst may include one or more Group 1 metals and/or Group 2 metals. For example, a modified zeolite or modified zeolitic catalyst may include, based on total weight of the modified zeolitic catalyst, about 0.005 wt. % to about 10 wt. %, about 0.005 wt. % to about 5 wt. %, about 0.005 wt. % to about 1 wt. %, about 0.005 wt. % to about 0.5 wt. %, about 0.005 wt. % to about 0.01 wt. %, about 0.01 wt. % to about 10 wt. %, about 0.01 wt. % to about 5 wt. %, about 0.01 wt. % to about 1 wt. %, about 0.01 wt. % to about 0.5 wt. %, about 0.5 wt. % to about 10 wt. %, about 0.5 wt. % to about 5 wt. %, about 0.5 wt. % to about 1 wt. %, about 1 wt. % to about 10 wt. %, about 1 wt. % to about 5 wt. %, or about 5 wt. % to about 10 wt. % of a Group 1 or Group 2 metal. The Group 1 metal may be lithium (Li), sodium (Na), potassium (K), rubidium (Rb), or cesium (Ce). The Group 2 metal may be beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), or barium (Ba). For example, a modified zeolitic catalyst may comprise from about 0.05 wt. % to about 0.25 wt. % magnesium. This may be carried out by any method known in the art, for example, ion exchange, Muller addition, impregnation, or the like. A Group 1 metal and/or Group 2 metal may be doped onto a precursor zeolite to form a metal-doped zeolite or onto a modified zeolite, either of which may be further converted into a zeolitic catalyst precursor, then into a modified zeolitic catalyst.

[0076] Optionally, a modified zeolite, a metal-doped zeolite, or zeolitic catalyst precursor may be combined with a support or binder material (both are referred to as a“binder” herein) to form a modified zeolitic catalyst. A modified zeolitic catalyst may include from about 1 wt. % to about

10 wt. %, about 1 wt. % to about 20 wt. %, about 1 wt. % to about 30 wt. %, about 1 wt. % to about

40 wt. %, about 1 wt. % to about 50 wt. %, about 1 wt. % to about 60 wt. %, about 1 wt. % to about

70 wt. %, about 1 wt. % to about 80 wt. %, about 1 wt. % to about 90 wt. %, about 1 wt. % to about

99 wt. %, about 10 wt. % to about 20 wt. %, about 10 wt. % to about 30 wt. %, about 10 wt. % to about 40 wt. %, about 10 wt. % to about 50 wt. %, about 10 wt. % to about 60 wt. %, about 10 wt. % to about 70 wt. %, about 10 wt. % to about 80 wt. %, about 10 wt. % to about 90 wt. %, about 10 wt. % to about 99 wt. %, about 20 wt. % to about 30 wt. %, about 20 wt. % to about 40 wt. %, about 20 wt. % to about 50 wt. %, about 20 wt. % to about 60 wt. %, about 20 wt. % to about 70 wt. %, about 20 wt. % to about 80 wt. %, about 20 wt. % to about 90 wt. %, about 20 wt. % to about 99 wt. %, about 30 wt. % to about 40 wt. %, about 30 wt. % to about 50 wt. %, about 30 wt. % to about 60 wt. %, about 30 wt. % to about 70 wt. %, about 30 wt. % to about 80 wt. %, about 30 wt. % to about 90 wt. %, about 30 wt. % to about 99 wt. %, about 40 wt. % to about 50 wt. %, about 40 wt. % to about 60 wt. %, about 40 wt. % to about 70 wt. %, about 40 wt. % to about 80 wt. %, about 40 wt. % to about 90 wt. %, about 40 wt. % to about 99 wt. %, about 50 wt. % to about 60 wt. %, about 50 wt. % to about 70 wt. %, about 50 wt. % to about 80 wt. %, about 50 wt. % to about 90 wt. %, about 50 wt. % to about 99 wt. %, about 60 wt. % to about 70 wt. %, about 60 wt. % to about 80 wt. %, about 60 wt. % to about 90 wt. %, about 60 wt. % to about 99 wt. %, about 70 wt. % to about 80 wt. %, about 70 wt. % to about 90 wt. %, about 70 wt. % to about 99 wt. %, about 80 wt. % to about 90 wt. %, about 80 wt. % to about 99 wt. %, or about 90 wt. % to about 99 wt. % binder based on total weight of the modified zeolitic catalyst. A suitable modified zeolite-to-binder ratio may be about 10: 1, about 4: 1, about 2: 1, about 1 : 1, about 1 :2, about 1:4, or about 1: 10.

[0077] Examples of suitable binders include other zeolites, other inorganic materials such as clays and metal oxides such as alumina, silica, silica-alumina, titania, zirconia, Group 1 metal oxides, Group 2 metal oxides, and combinations thereof. Clays may be kaolin, bentonite, and montmorillonite and may be sourced commercially. They may be blended with other materials such as silicates. Other suitable binders may include binary porous matrix materials (such as silica- magnesia, silica-thoria, silica-zirconia, silica-beryllia and silica-titania), and ternary materials (such as silica-alumina-magnesia, silica-alumina-thoria and silica-alumina-zirconia). One or more binders may be used in a modified zeolitic catalyst described herein, for example, silica and alumina may be used in combination. Preferably, however, the binder is silica.

[0078] Optionally, one or more promoters may be present in a modified zeolitic catalyst described herein. For example, a modified zeolitic catalyst may include at least about 0.005 wt. % to about 10 wt. %, about 0.005 wt. % to about 5 wt. %, about 0.005 wt. % to about 1 wt. %, about 0.005 wt. % to about 0.5 wt. %, about 0.005 wt. % to about 0.01 wt. %, about 0.01 wt. % to about 10 wt. %, about 0.01 wt. % to about 5 wt. %, about 0.01 wt. % to about 1 wt. %, about 0.01 wt. % to about 0.5 wt. %, about 0.5 wt. % to about 10 wt. %, about 0.5 wt. % to about 5 wt. %, about 0.5 wt. % to about 1 wt. %, about 1 wt. % to about 10 wt. %, about 1 wt. % to about 5 wt. %, or about 5 wt. % to about 10 wt. % of a promoter based on total weight of the modified zeolitic catalyst. The promoter may be a Group 3 metal, a Group 4 metal, a Group 5 metal, a Group 6 metal, a Group 7 metal, a Group 8 metal, a Group 9 metal, a Group 10 metal, a Group 11 metal, a Group 13 metal, and a Group 14 metal. Examples of promoters include, but are not limited to, scandium (Sc), tin (Sn), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), palladium (Pd), gallium (Ga), iridium (Ir), indium (In), germanium (Ge), rhodium (Rh), ruthenium (Ru), and copper (Cu). Promoters may be incorporated from about 0.005 wt. % to about 15 wt. % by any method well known in the art, for example, impregnation, Muller addition, ion exchange, and the like.

[0079] Optionally, the modified zeolite in a modified zeolitic catalyst may be present at least partly in hydrogen form. This can readily be achieved, for example, by ion exchange to convert the modified zeolite to the ammonium form, followed by calcination in air or an inert atmosphere at a temperature from about 400°C to about 1000°C to convert the ammonium form to the active hydrogen form. If an organic structure-directing agent is used in the synthesis of a zeolite, additional calcination may be desirable to remove the organic structure-directing agent.

[0080] Optionally, a modified zeolitic catalyst may include one or more selectivating agents to introduce diffusional limitations to a modified zeolitic catalyst. Silicone selectivation can be performed with any suitable silicone oil or from an organic silica source such as tetraethyl orthosilicate (TEOS). As used herein, a selectivating agent refers to an agent that prevents unwanted activity derived from sites on the modified zeolite’s external surface.

[0081] A zeolitic catalyst precursor may be calcined, reduced (e.g., in Eh) and/or sulfided by methods well known in the art to yield a modified zeolitic catalyst. Sulfidation can be performed by any convenient method, such as gas phase sulfidation or liquid phase sulfidation.

[0082] As used herein, modified zeolitic catalyst, and grammatical variations thereof, refers to a catalyst prepared from a precursor zeolite or a metal-doped zeolite by adjusting the acidity of a precursor zeolite or metal-doped zeolite to form a modified zeolite. A precursor zeolite’s, and likewise, a metal-doped zeolite’s acidity is multi-faceted, and may be indicated by one or more of its alpha value, collidine uptake, Bronsted acid site density, ratio of Bronsted-to-Lewis acid sites, and ammonia adsorption/desorption. Structurally, these properties may be influenced by one or more of the framework silica-to-alumina ratio, bulk silica-to-alumina ratio, and the presence of Group 1 and Group 2 metals, among others. As used herein, a modified zeolitic catalyst may have an acidity, as measured by alpha value, of less than about 2 or less than about 1, for example, in a range of about 0 to about 3, about 0 to about 2, or about 0 to about 1. A modified zeolitic catalyst may have an acidity, as measured by collidine uptake, of, less than about 2 pmol/g, less than about 3 pmol/g, less about 10 pmol/g, less than about 15 pmol/g, less than 20 pmol/g, less than about 25 pmol/g, less than about 30 pmol/g, less than about 35 pmol/g less, or than about 40 pmol/g; ranges include about 0 pmol/g to about 2 pmol/g, about 0 pmol/g to about 3 pmol/g, about 0 pmol/g to about 5 pmol/g, about 0 pmol/g to about 10 pmol/g, about 0 pmol/g to about 15 pmol/g, about 0 pmol/g to about 20 pmol/g, about 0 pmol/g to about 25 pmol/g, about 0 pmol/g to about 30 pmol/g, about 0 pmol/g to about 35 pmol/g, and about 0 pmol/g to about 40 pmol/g. Preferably, a modified zeolitic catalyst has a collidine uptake of less than about 2 pmol/g.

[0083] Advantageously, a modified zeolitic catalyst as described herein may be resistant to the formation of carbonaceous material (i.e.. coke) on the surface of modified zeolitic catalyst. While not wishing to be bound by theory, coke resistance is believed to be due to the three-dimensional zeolitic structure, which makes it more difficult for coke to form when compared to conventional reforming catalysts.

[0084] Example embodiments of modified zeolitic catalysts suitable for use in the methods and systems described herein include:

• aUSY precursor zeolite (with an alpha of2.2 and a collidine uptake of l0.9 pmol/g) extruded with silica at a ratio of 80:20, steam-treated for 1 hour at 1500°F (815.6°C), impregnated with 0.9% Pt; 0.05 wt. % Mg added;

• a USY precursor zeolite (with an alpha of 12 and a collidine uptake of 99.6 pmol/g) extruded with silica at a ratio of 80:20, steam-treated for 5 hours at 1500°F (815.6°C) + 0.9 wt. % Pt, impregnated with 0.9% Pt; 0.21 wt. % Mg added;

• a USY precursor zeolite (with an alpha of 12 and a collidine uptake of 99.6 pmol/g) extruded with silica at a ratio of 80:20, steam-treated for 5 hours at 1500°F (815.6°C) + 0.9 wt. % Pt, impregnated with 0.9% Pt;

• aUSY precursor zeolite (with an alpha of2.2 and a collidine uptake of l0.9 pmol/g) extruded with silica at a ratio of 80:20, steam-treated for 1 hour at 1500°F (815.6°C), impregnated with 0.9% Pt; 0.025 wt. % Mg added;

• aUSY precursor zeolite (with an alpha of2.2 and a collidine uptake of l0.9 pmol/g) extruded with silica at aratio of 80:20, steam-treated for 1 hour at 1500°F (815.6°C), impregnated with 0.9% Pt; and

• aUSY precursor zeolite (with an alpha of2.2 and a collidine uptake of l0.9 pmol/g) extruded with silica at a ratio of 80:20, steam-treated for 1 hour at 1700°F (926.7°C), impregnated with 0.9% Pt.

Methods and Systems of Converting Hydrocarbons

[0085] Methods and systems are provided herein that utilize at least one modified zeolitic catalyst for converting a hydrocarbon feed stream to a hydrocarbon product stream. A hydrocarbon feed stream may be contacted with a modified zeolitic catalyst comprising a modified zeolite, a transition metal, and optionally a binder under conditions effective to convert the hydrocarbon feed stream to a hydrocarbon product stream comprising high-octane gasoline, xylenes, toluene, benzene, or any blend thereof. The methods described herein may further comprise providing hydrogen to one or more reactors in which the contacting is carried out.

Systems for Converting Hydrocarbons

[0086] A system for performing the above-described method is also provided herein. A system may include, but is not limited to, a hydrocarbon feed stream, a hydrocarbon product stream, and at least one reactor in which the hydrocarbon feed stream may be contacted with one or more of the modified zeolitic catalysts as described herein under conditions effective to convert the hydrocarbon feed stream to the hydrocarbon product stream. The at least one reactor has a hydrocarbon feed inlet constructed and arranged to receive the hydrocarbon feed stream and a hydrocarbon product outlet constructed and arranged to provide the hydrocarbon product stream. A system for converting a hydrocarbon feed stream may be part of a reforming unit. In any embodiment, a reforming unit may be further capable of regenerating a modified zeolitic catalyst. For example, the reforming unit may be a cyclic reforming unit or a semi-regenerative reforming unit.

[0087] One embodiment of a reforming system suitable for the methods disclosed herein is shown in FIG. 1. The reforming system 100 includes a pre-treatment stage 102, a post-treatment separator 104, a heater 106, a reactor 108, a separation stage 110, and a compressor 112 for compressing a hydrogen stream 111. A hydrocarbon feed stream 101 may be conveyed to a pre treatment stage 102 to modify the disposition of the hydrocarbon feed stream 101 for compatibility with downstream processes. For example, the pre-treatment stage 102 may modify the sulfur content, nitrogen content, and/or remove water from the hydrocarbon feed stream 101.

[0088] The pre-treatment stage effluent 103 comprising a treated hydrocarbon feed stream may then be conveyed to a post-treatment separator 104 to isolate the treated hydrocarbon feed stream from a waste stream 116; the waste stream may include water, ammonia, hydrogen sulfide, and/or the like. The post-treatment separator effluent 107 comprising a treated hydrocarbon feed stream may then be conveyed together with hydrogen joining from the recycled compressed hydrogen stream 113 to a heater 106 to warm the hydrocarbon feed stream. The heated hydrocarbon feed stream 107 may then be conveyed to a reactor 108. The reactor 108 comprises at least one catalyst bed 120. The at least one catalyst bed 120 in reactor 108 comprises at least one modified zeolitic catalyst as described herein. After being conveyed through the reactor 108, the reactor effluent 109 comprising a hydrocarbon product stream may be conveyed to a separation stage 110, which isolates valuable fractions of the hydrocarbon product stream. The separation stage 110 may include one or more separation processes, each of which may be, for example, extraction, distillation, membrane separation, aromatic/saturate separation, or any combination thereof. [0089] For example, hydrogen 111 may be isolated from the hydrocarbon product stream. The hydrocarbon product stream may be separated into two or more fractions 114, 115, including, but not limited to, a C4- fraction, an LPG fraction, a C5+ fraction, a C7+ fraction, an aromatic fraction, or any combination thereof. Optionally, an aromatics fraction may be further separated to isolate one or more of benzene, toluene, xylenes, or heavier aromatics. In another example, a C5+ fraction may be separated to isolate low vapor pressure, high-octane gasoline. The hydrogen 111 may be collected for commercial sale or may be recycled back to the system, passing through a compressor 112 and joining the hydrocarbon feed stream at any location upstream of the reactor 108. For example, FIG. 1 depicts a recycled compressed hydrogen stream 113 joining the post-treatment separator effluent 107. Alternatively, the recycled compressed hydrogen stream 113 may be reintroduced into the system with the hydrocarbon feed stream 101, the post-treatment effluent 103, or with heated hydrocarbon feed stream 107. It may also be fed directly into the reactor 108. In any embodiment, the recycled compressed hydrogen stream 113 may not be entirely derived from recycled hydrogen. For example, the recycled compressed hydrogen stream 113 may be supplemented with hydrogen from another source (e.g, commercially available hydrogen or hydrogen from another reforming unit).

[0090] In any embodiment, the pre-treatment stage 102 may not be present. In such embodiments, the hydrocarbon feed stream 101, together with a hydrogen stream 113, may be directly conveyed to the heater 106 then to the reactor 108. In any embodiment, a reactor may contain multiple catalyst beds, for example, in a stacked bed configuration. In any embodiment, a reforming system may comprise two or more reactors, each comprising one or more catalyst beds. In such cases, the system may include one or more conduits to fluidly connect the two or more reactors to each other. A conduit connecting two reactors may further comprise a heater.

Hydrocarbon Feed Streams

[0091] The methods and systems described herein may be suitable for converting a hydrocarbon feed stream comprising naphtha feedstock, a fraction thereof (e.g., light naphtha, heavy naphtha), or a feedstock comprising C6-C8 hydrocarbons. A suitable hydrocarbon feed stream may have a boiling range characterized by a T5-T95 range of about 10°C to about 232°C. Examples of suitable full-range naphtha (or naphtha fractions) include hydrotreated naphtha, fluid catalytic cracker (FCC) naphtha, straight run naphtha, coker naphtha, delayed coker naphtha, fluid coker naphtha, and any blend thereof. A hydrocarbon feed stream comprising G,-G hydrocarbons may include C6-C8 paraffins, G,-G naphthenes, G,-Cs aromatics, or combinations thereof.

[0092] Advantageously, the modified zeolitic catalysts as described herein are believed to be efficient at catalyzing the conversion of paraffins to naphthenes and aromatics. Thus, a modified zeolitic catalyst may be particularly advantaged for converting hydrocarbon feed streams with a high paraffin content and/or a low N+2A value. A hydrocarbon feed stream may comprise C4-C12 paraffins, for example, butane, pentane, hexane, heptane, and/or octane. A hydrocarbon feed stream may comprise at least about 30 wt. %, at least about 45 wt. %, at least about 50 wt. %, at least about 60 wt. %, at least about 70 wt. %, at least about 80 wt. %, at least about 90 wt. %, at least about 95 wt. %, at least about 99 wt. % or about 100 wt. %; or in a range of about 45 wt. % to about 100 wt. %, about 50 wt. % to about 100 wt. %, about 60 wt. % to about 100 wt. %, about 70 wt. % to about 100 wt. %, about 90 wt. % to about 100 wt. % or about 95 wt. % to about 100 wt. % C4-C12 paraffins, based on total weight of the hydrocarbon feed stream. A hydrocarbon feed stream may be characterized by an N+2A value of less than about 90 (i.e.. about 0 to about 90), less than about 80 (i.e., about 0 to about 80), less than about 70 (i.e., about 0 to about 70), less than about 60 (i.e., about 0 to about 60), less than about 50 (i.e., about 0 to about 50), or less than about 40 (i.e., about 0 to about 40).

[0093] Alternatively, the majority of a suitable hydrocarbon feed stream may comprise a Ce- C8 hydrocarbons, for example, hexane, heptane, and/or octane. A hydrocarbon feed stream may comprise at least about 60 wt. %, at least about 70 wt. %, at least about 80 wt. %, at least about 90 wt. %, at least about 95 wt. %, at least about 99 wt. % or about 100 wt. %; or in a range of about 45 wt. % to about 100 wt. %, about 50 wt. % to about 100 wt. %, about 60 wt. % to about 100 wt. %, about 70 wt. % to about 100 wt. %, about 90 wt. % to about 100 wt. % or about 95 wt. % to about 100 wt. % C6-C8 hydrocarbons, based on total weight of the G,-Cs hydrocarbon feed stream. In any embodiment, a hydrocarbon feed stream may comprise a majority (e.g., about 50 wt. % to about 100 wt. %, about 75 wt. % to about 100 wt. %, or about 90 wt. % to about 100 wt. %) C6-C8 paraffins or may comprise all G,-Cs paraffins (e.g., greater than about 99 wt. % or about 100 wt. %). In any embodiment, a hydrocarbon feed stream may comprise a majority (e.g., about 50 wt. % to about 100 wt. %, about 75 wt. % to about 100 wt. %, or about 90 wt. % to about 100 wt. %) hexane or may comprise all hexane (e.g., greater than about 99 wt. % or about 100 wt. %). In any embodiment, a hydrocarbon feed stream may comprise a majority (e.g., about 50 wt. % to about 100 wt. %, about 75 wt. % to about 100 wt. %, or about 90 wt. % to about 100 wt. %) heptane or may comprise all heptane (e.g., greater than about 99 wt. % or about 100 wt. %).

[0094] The modified zeolitic catalyst may be resistant to the presence of nitrogen. For example, a modified zeolitic catalyst may be contacted with a hydrocarbon feed containing up to 1000 ppm basic nitrogen without significant detrimental effects to the modified zeolitic catalyst’s activity. In addition to being resistant to nitrogen, a modified zeolitic catalyst as described herein may also be tolerant of sulfur in a hydrocarbon feed stream, particularly when rhenium is absent from said modified zeolitic catalyst. Whereas the presence of sulfur in a hydrocarbon feed stream typically drives down product stream yield when using a chlorided alumina catalyst, a modified zeolitic catalyst as disclosed herein does not suffer the same effects. For example, a modified zeolitic catalyst may be compatible with a feedstock having no measurable sulfur content to about 10 ppm sulfur, including about 0.5 ppm to about 10 ppm, about 1 ppm to about 10 ppm, and about 1.5 ppm to about 10 ppm.

[0095] Thus, a modified zeolitic catalyst may provide particular advantages to cyclic reforming units and semi-regenerative reforming units as these types of units typically require more frequent offline catalyst regeneration than (more expensive) reforming units such as continuous catalyst regeneration reforming units.

Reactors

[0096] In the methods and systems described herein, a hydrocarbon feed stream may be contacted with one or more modified zeolitic catalysts as described herein under conditions effective to convert the hydrocarbon feed stream to a hydrocarbon product stream. The contacting may be performed in one or more reactors, each comprising at least one catalyst bed. At least one of catalyst beds includes a modified zeolitic catalyst as described herein. The one or more catalyst beds may be fixed beds or moving beds. The one or more catalyst beds may be contained within a single reactor or may be in separate reactors.

[0097] The reaction conditions for converting a hydrocarbon feed stream to a hydrocarbon product stream may be any suitable conditions known in the art. For example, the one or more reactors may each, independently, be held at a pressure of about 15 psig (103 kPa) to about 1500 psig (10340 kPa) and/or an Fhihydrocarbon ratio (FkiHC ratio) of about 0.1 : 1 to about 10: 1. The combined one or more reactors may have a weight hourly space velocity (WHSV) of about 0.1 hours ¹ to about 15 hours ¹. The one or more reactors may each, independently, be held at an El temperature of about 400°C to about 750°C. For example, a reactor may be held at an El temperature of about 500°C, a pressure of about 350 psig (2410 kPa), a WHSV of about 0.1 hours ¹ to about 15 hours ¹, and/or an H2:HC ratio of about 5: 1.

[0098] As noted above, a modified zeolitic catalyst may be resistant to coking. Thus, a modified zeolitic catalyst may be subjected to the more severe conditions that favor high yield and high-octane gasoline production. For example, a reactor may be operated at one or more of the following conditions: an El temperature of about 500°C or greater, a pressure of about 150 psig (1030 kPa) to about 215 psig (1480 kPa), an H2:HC ratio of less than 2 about 5: 1 ( e.g ., about 1.5: 1), and a WHSV of about 2.5 hours ¹ or less (e.g., about 1 hour ¹). In a chlorided alumina catalyst, conditions such as these would exacerbate coke formation and reduce product yield. Hydrocarbon Product Streams

[0099] When a hydrocarbon feed stream comprises naphtha (or a fraction thereof), the hydrocarbon product stream derived therefrom may comprise, consist essentially of, or consist of aromatic and isoparaffmic hydrocarbons (i.e.. upgraded naphtha). A hydrocarbon product stream or fractions thereof (e.g., the C5+ fraction) may be characterized by a higher octane number than the hydrocarbon feed stream from which it is derived. For example, the C5+ fraction of a hydrocarbon product stream may be characterized by an octane number of at least about 80, at least about 85, at least about 90, at least about 95, at least about 99, or about 100; or in a range of about 80 to about 100, about 90 to about 100 or about 95 to about 100. A hydrocarbon product stream or fractions thereof may be further blended with other streams, such as a gasoline source.

[0100] When a hydrocarbon feed stream comprises C4-C12 hydrocarbons, the hydrocarbon product stream derived therefrom may comprise C4-C12 aromatics. A hydrocarbon product stream may include at least about 30 wt. %, at least about 50 wt. %, at least about 70 wt. %, at least about 90 wt. %, at least about 99 wt. % or about 100 wt. %; or in a range of about 30 wt. % to about 100 wt. %, about 50 wt. % to about 100 wt. %, about 70 wt. % to about 100 wt. %, about 30 wt. % to about 90 wt. % or about 50 wt. % to about 70 wt. % C4-C12 aromatics.

[0101] When a hydrocarbon feed stream comprises CVCs hydrocarbons, the hydrocarbon product stream derived therefrom may comprise C6-C8 aromatics. A hydrocarbon product stream may include at least about 30 wt. %, at least about 50 wt. %, at least about 70 wt. %, at least about 90 wt. %, at least about 99 wt. % or about 100 wt. %; or in a range of about 30 wt. % to about 100 wt. %, about 50 wt. % to about 100 wt. %, about 70 wt. % to about 100 wt. %, about 30 wt. % to about 90 wt. % or about 50 wt. % to about 70 wt. % C6-C8 aromatics. A hydrocarbon product stream may comprise a majority (e.g., about 50 wt. % to about 100 wt. %, about 75 wt. % to about 100 wt. %, or about 90 wt. % to about 100 wt. %) benzene or may comprise all benzene (e.g., greater than about 99 wt. % or about 100 wt. %). Alternatively, a hydrocarbon product stream may comprise a majority (e.g., about 50 wt. % to about 100 wt. %, about 75 wt. % to about 100 wt. %, or about 90 wt. % to about 100 wt. %) toluene or may comprise substantially all toluene (e.g., greater than about 99 wt. % or about 100 wt. %). Alternatively, a hydrocarbon product stream may comprise a majority (e.g., about 50 wt. % to about 100 wt. %, about 75 wt. % to about 100 wt. %, or about 90 wt. % to about 100 wt. %) Cs aromatics (e.g., ethylbenzene, xylenes) or may comprise substantially all Cs aromatics (e.g., greater than about 99 wt. % or about 100 wt. %).

[0102] Further, whereas chlorided alumina catalysts produce C9+ aromatics, which have limited commercial value compared to C6-Cs aromatics, a modified zeolitic catalyst as described herein tends to yield more valuable G,-s aromatics. [0103] Selectivity for paraffin dehydrocyclization may be realized through the use of modified zeolitic catalysts described herein to reform a hydrocarbon feed stream (e.g, a naphtha stream). The selectivity for paraffin dehydrocyclization, however, may not be apparent until sufficient conversion of a hydrocarbon feed stream, for example, after naphthenic contents of the hydrocarbon feed stream are sufficiently converted to aromatics, at which point the conversion of paraffins into aromatics will dominate as a reforming reaction. When compared to product streams yielded from chlorided alumina, the modified zeolitic catalysts described herein may yield a higher C5+ fraction at the same octane number due to the increased selectivity for paraffin dehydrocyclization.

Example Embodiments

[0104] One nonlimiting example embodiment is a method for converting hydrocarbons comprising: providing a modified zeolitic catalyst comprising a modified zeolite, a transition metal, and optionally a binder; and contacting a hydrocarbon feed stream comprising full-range naphtha or a fraction thereof and at least about 30 wt. % paraffins with the modified zeolitic catalyst under conditions effective to convert the hydrocarbon feed stream to a hydrocarbon product stream that comprises at least one product selected from the group consisting of high octane gasoline, xylenes, toluene, and benzene, wherein when the hydrocarbon product stream has a RON of about 95 the C5+ yield is at least about 80 wt. %. Optionally, the embodiment may further include one or more of the following: Element 1 : the method, wherein the hydrocarbon feed stream comprises naphtha; Element 2: the method as in claim 1, wherein the hydrocarbon feed stream comprises hydrotreated naphtha, virgin naphtha, intermediate cracked naphtha, fluid catalytic cracker naphtha, straight run naphtha, coker naphtha, delayed coker naphtha, steam cracker naphtha, fluid coker naphtha, hydrocrackate, or any blend thereof; Element 3: the method wherein the hydrocarbon feed stream comprises at least about 45 wt. % paraffins; Element 4: the method wherein the hydrocarbon feed stream has an N+2A value of less than about 90; Element 5: the method wherein the hydrocarbon feed stream has an N+2A value of less than about 75; Element 6: the method wherein the modified zeolite is characterized by one or more of a bulk silica-to- alumina ratio of about 80: 1 or greater and a framework silica-to-alumina ratio of about 80: 1 or greater; Element 7: the method wherein the modified zeolite is characterized by a bulk silica-to- alumina ratio greater than about 400: 1; Element 8: the method wherein the modified zeolite is characterized by a framework silica-to-alumina ratio of about 80: 1 or greater; Element 9: the method wherein the modified zeolite is characterized by a framework silica-to-alumina ratio of greater than about 500: 1 ; Element 10: the method wherein the modified zeolite is characterized by a framework silica-to-alumina ratio of about 2000: 1 or greater; Element 11: the method wherein the modified zeolitic catalyst is characterized by an alpha value of less than about 3; Element 12: the method wherein the modified zeolitic catalyst is characterized by an alpha value of less than about 2; Element 13: the method wherein the modified zeolite comprises a 12-member ring zeolite or a three-dimensional 12-member ring zeolite; Element 14: the method wherein the modified zeolite comprises a framework classified by IZA code FAU or BEA; Element 15: the method wherein the modified zeolite comprises a USY zeolite; Element 16: the method wherein the modified zeolite comprises an L, Beta, or USY zeolite; Element 17: the method wherein the modified zeolitic catalyst comprises about 0.05 wt. % to about 10 wt. % transition metal, the transition metal comprising one or more of the following elements: platinum, nickel, and palladium; Element 18: the method wherein the modified zeolitic catalyst comprises at least one promoter in the amount of about 0.01 wt. % to about 10 wt. %, the promoter selected from the group consisting of Sn, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Re, Ga, Ir, In, Rh, Zn, Na, K, Ca, Ba, Be, Mg, and Sr; Element 19: the method wherein the binder comprises silica; Element 20: the method wherein the modified zeolitic catalyst further comprises a Group 1 or Group 2 metal cation; Element 21 : Element 20 + the method wherein the metal cation comprises one or more of the following elements: magnesium, calcium, barium, sodium, and potassium; Element 22: the method wherein the conditions comprise a pressure of about 35 psig (240 kPa) to about 350 psig (2410 kPa) and an FUHC ratio of about 0.5: 1 to about 10: 1; Element 23: the method wherein the conditions comprise an El temperature of at least about 450°C, a pressure of at least about 215 psig (1480 kPa), aWHSV of at least about 5 hours ¹, and an FUHC ratio of at least about 2.5:1; Element 24: the method wherein the conditions comprise an El temperature of at least about 500°C, a pressure of not more than about 215 psig (1480 kPa), a WHSV of not more than about 5 hours ¹, and an FUHC ratio of not more than about 2.5: 1; Element 25: the method wherein the rate of the decrease in octane number of the hydrocarbon product stream over run time is not more than about 1 per 150 hours; Element 26: the method wherein the method is carried out in a fixed-bed reactor; Element 27: the method wherein the yield of aromatics in the hydrocarbon product stream is at least about 50 wt. %; Element 28: the method wherein when the RON of the hydrocarbon product stream is at least 94, the molar ratio of ethylbenzene to the A8 fraction is not more than about 0.15; Element 29: the method wherein when the RON of the C5+ fraction of the hydrocarbon product stream is about 97, the yield of aromatics is at least about 46 wt. %; Element 30: the method wherein the yield of benzene, toluene, and xylenes is at least about 35 wt. %. Examples of combinations include, but are not limited to, Element 1 in combination with one or more of Elements 3-30; Element 2 in combination with one or more of Elements 3-30; Element 3 in combination with one or more of Elements 4-30; Element 4 in combination with one or more of Elements 5-30; Element 5 in combination with one or more of Elements 6-30; Element 6 in combination with one or more of Elements 7-30; Element 7 in combination with one or more of Elements 8-30; Element 8 in combination with one or more of Elements 9-30; Element 9 in combination with one or more of Elements 10-30; Element 10 in combination with one or more of Elements 11-30; Element 11 in combination with one or more of Elements 12-30; Element 11 in combination with one or more of Elements 12-30; Element 12 in combination with one or more of Elements 13-30; Element 13 in combination with one or more of Elements 14-30; Element 14 in combination with one or more of Elements 15-30; Element 15 in combination with one or more of Elements 16-30; Element 16 in combination with one or more of Elements 17-30; Element 17 in combination with one or more of Elements 18-30; Element 18 in combination with one or more of Elements 19-30; Element 19 in combination with one or more of Elements 20-30; Element 20 (and optionally Element 21) in combination with one or more of Elements 22-30; Element 22 in combination with one or more of Elements 23-30; Element 23 in combination with one or more of Elements 24-30; Element 24 in combination with one or more of Elements 25-30; Element 25 in combination with one or more of Elements 26-30; Element 26 in combination with one or more of Elements 27-30; Element 27 in combination with one or more of Elements 28-30; Element 28 in combination with one or more of Elements 29-30; Element 29 in combination with Element 30; Element 1 in combination with Element 5; Element 1 in combination with Elements 5 and 6; Element 1 in combination with Elements 5, 6, and 9; Element 1 in combination with Elements 5, 6, and 10; Element 1 in combination with Elements 10 and 12; Element 1 in combination with Elements 10, 12, and 15; and Element 1 in combination with Elements 10, 12, 15, and 24.

[0105] Another nonlimiting example embodiment is a method for converting hydrocarbons comprising: providing a modified zeolitic catalyst comprising a modified zeolite, a transition metal, and optionally a binder; and contacting a hydrocarbon feed stream comprising at least about 90 wt. % C6-C8 hydrocarbons and at least about 30 wt. % paraffins with the modified zeolitic catalyst under conditions effective to convert the hydrocarbon feed stream to a hydrocarbon product stream that comprises at least one product selected from the group consisting of xylenes, toluene, and benzene, wherein the ratio of aromatics yield (wt. %) to LPG yield (wt. %) is at least about 1. Optionally, the embodiment may further include one or more of the following: Elements 3-27 and Element 30. Examples of combinations of Elements include, but are not limited to, Element 10 in combination with Element 15 and Element 10 in combination with Elements 15 and 24.

[0106] Another nonlimiting example embodiment is a method of preparing a modified zeolitic catalyst having enhanced dehydrocyclization activity comprising treating a precursor zeolite with a Group 1 or Group 2 metal cation to form a modified zeolite; and converting the modified zeolite into a modified zeolitic catalyst. Optionally, the embodiment may further include one or more of the following: Element 31 : the method wherein the metal cation is selected from the group consisting of magnesium, calcium, barium, sodium, potassium, or combinations thereof; Element 32: the method wherein the metal cation is divalent.

[0107] Another nonlimiting example embodiment is a system for converting hydrocarbons, wherein the system comprises: a hydrocarbon feed stream having a paraffin content of at least about 30 wt. %; a hydrocarbon product stream, wherein the hydrocarbon product stream comprises at least one product selected from the group consisting of high octane gasoline, xylene, toluene, and benzene; at least one reactor operated under conditions effective to convert the hydrocarbon feed stream to the hydrocarbon product stream, wherein the reactor comprises a modified zeolitic catalyst; a hydrocarbon feed inlet constructed and arranged to receive the hydrocarbon feed stream; and a hydrocarbon product outlet constructed and arranged to provide the hydrocarbon product stream, wherein when the hydrocarbon product stream has RON of about 95, the C5+ yield is at least about 80 wt. %. Optionally, the embodiment may further include one or more of the following: Element 33: the system wherein the hydrocarbon feed stream is characterized by an N+2A value of less than about 90; Element 34: the system wherein the hydrocarbon feed stream has an N+2A value of less than 90; Element 35: the system wherein the hydrocarbon feed stream has an N+2A value of less than about 75; Element 36: the system wherein the modified zeolitic catalyst has a bulk silica-to-alumina ratio of about 40: 1 or greater; Element 37: the system wherein the modified zeolitic catalyst has a bulk silica-to-alumina ratio of greater than about 400: 1; Element 38: the system wherein the modified zeolitic catalyst has a framework silica-to-alumina ratio of about 80: 1 or greater; Element 39: the system wherein the modified zeolitic catalyst has a framework silica- to-alumina ratio of greater than about 500: 1 ; Element 40: the system wherein the modified zeolitic catalyst has a framework silica-to-alumina ratio of about 2000: 1 or greater; Element 41 : the system wherein the modified zeolitic catalyst having an alpha value of less than about 10; Element 42: the system wherein the modified zeolitic catalyst having an alpha value of less than about 3; Element 43: the system wherein the modified zeolitic catalyst having an alpha value of less than about 2; Element 44: the system wherein the modified zeolitic catalyst comprises a 12-member ring zeolite; Element 45: the system wherein the modified zeolitic catalyst comprises a three-dimensional 12- member ring zeolite; Element 46: the system wherein the modified zeolitic catalyst comprises a framework classified by IZA code FAU or BEA; Element 47: the system wherein the modified zeolitic catalyst comprises a USY zeolite; Element 48: the system wherein the modified zeolitic catalyst comprises an L, Beta, or USY zeolite; Element 49: the system wherein the modified zeolitic catalyst comprises about 0.05 wt. % to about 10 wt. % transition metal; Element 50: the system wherein the transition metal comprises platinum, nickel, or palladium; Element 51: the system wherein the modified zeolitic catalyst comprises at least one promoter in the amount of about 0.01 wt. % to about 10 wt. % selected from the group consisting of Sn, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Re, Ga, Ir, In, Rh, Zn, Na, K, Ca, Ba, Be, Mg, and Sr; Element 52: the system wherein the binder comprises silica; Element 53: the system wherein the modified zeolitic catalyst further comprises a Group 1 or Group 2 metal cation; Element 54: the system wherein the Group 1 or Group 2 metal cation is selected from the group consisting of magnesium, calcium, barium, sodium, potassium, and combinations thereof; Element 55: the system wherein the hydrocarbon feed stream comprises full-range naphtha; Element 56: the system wherein the hydrocarbon feed stream comprises hydrotreated naphtha, virgin naphtha, intermediate cracked naphtha, fluid catalytic cracker naphtha, straight run naphtha, coker naphtha, delayed coker naphtha, steam cracker naphtha, fluid coker naphtha, hydrocrackate, or any blend thereof; Element 57: the system wherein the conditions comprise a pressure of about 35 psig (240 kPa) to about 350 psig (2410 kPa) and an H2:HC ratio of about 0.5: 1 to about 10: 1; Element 58: the system wherein the conditions comprise an El temperature of at least about 450°C, a pressure of at least about 215 psig (1480 kPa), aWHSV of at least about 5 hours ¹, and an H2:HC ratio of at least about 2.5:1; Element 59: the system wherein the conditions comprise an El temperature of at least about 500°C, a pressure of not more than about 215 psig (1480 kPa), a WHSV of not more than about 5 hours ¹, and an H2:HC ratio of not more than about 2.5: 1; Element 60: the system wherein the reactor is a fixed-bed reactor; Element 61 : the system wherein the yield of aromatics in the hydrocarbon product stream is at least about 50 wt. %; Element 62: the system wherein when the RON of the hydrocarbon product stream is at least 94, the molar ratio of ethylbenzene to the A8 fraction is not more than about 0.15; Element 63: the system wherein when the RON of the C5+ fraction of the hydrocarbon product stream is about 97, the yield of aromatics is at least about 46 wt. %; Element 64: the system wherein the yield of benzene, toluene, and xylenes is at least about 35 wt. %; Element 65: the system wherein the modified zeolite is characterized by a bulk silica-to-alumina ratio of greater than about 80: 1; Element 66: the system wherein the modified zeolitic catalyst is characterized by a collidine uptake of less than about 3 pg/mol. Examples of combinations include, but are not limited to, Element 31 in combination with one or more of Elements 32-66; Element 32 in combination with one or more of Elements 33-66; Element 33 in combination with one or more of Elements 34-66; Element 34 in combination with one or more of Elements 35-66; Element 35 in combination with one or more of Elements 36-66; Element 36 in combination with one or more of Elements 37-66; Element 37 in combination with one or more of Elements 38-66; Element 38 in combination with one or more of Elements 39-66; Element 39 in combination with one or more of Elements 40-66; Element 40 in combination with one or more of Elements 41-66; Element 41 in combination with one or more of Elements 42-66; Element 42 in combination with one or more of Elements 43-66; Element 43 in combination with one or more of Elements 44-66; Element 44 in combination with one or more of Elements 45-66; Element 45 in combination with one or more of Elements 46-66; Element 46 in combination with one or more of Elements 47-66; Element 47 in combination with one or more of Elements 48-66; Element 48 in combination with one or more of Elements 49-66; Element 49 in combination with one or more of Elements 50-66; Element 50 in combination with one or more of Elements 51-66; Element 51 in combination with one or more of Elements 52-66; Element 52 in combination with one or more of Elements 53-66; Element 53 in combination with one or more of Elements 54-66; Element 54 in combination with one or more of elements 55-66; Element 55 in combination with one or more of elements 56-66; Element 56 in combination with one or more of elements 57-66; Element 57 in combination with one or more of elements 58-66; Element 58 in combination with one or more of elements 59-66; Element 59 in combination with one or more of elements 60-66; Element 60 in combination with one or more of elements 61-66; Element 61 in combination with one or more of elements 62-66; Element 62 in combination with one or more of elements 63-66; Element 63 in combination with one or more of Elements 64- 66; Element 64 in combination with one or more of Elements 65- 66; Element 65 in combination with Element 66; Element 40 in combination with Element 37; Element 40 in combination with Element 37 and 43; Element 40 in combination with Elements 37, 43, and 66; Element 47 in combination with Elements 43 and 66; Element 55 in combination with Element 60; and Element 55 in combination with Element 47 and 60.

[0108] Another nonlimiting example embodiment includes a method of preparing a modified zeolitic catalyst comprising: treating a precursor zeolite having a bulk silica-to-alumina ratio and a framework silica-to-alumina ratio with one or more of acid, steam, and a combination thereof under conditions effective to increase one or more of the bulk silica-to-alumina ratio and framework silica-to-alumina ratio to at least about 80: 1 to prepare a modified zeolite; and contacting the modified zeolite with a transition metal to form a modified zeolitic catalyst having enhanced dehydrocyclization activity as compared to the precursor zeolite. Optionally, the embodiment may include one or more of the following elements: Element 67: the method wherein treating comprises steaming at a temperature of between about 750°F (398.9°C) to about 3000°F (1649°C) for a period of about 1 hour to about 5 hours; Element 68: the method wherein the bulk silica-to-alumina ratio of the modified zeolite is at least about 400: 1; Element 69: the method wherein treating comprises steaming at a temperature of between about 1500°F (815.6°C) to about 3000°F (1649°C) for a period of about 1 hour to about 5 hours; Element 70: the method wherein the framework silica-to-alumina ratio of the modified zeolite is at least about 2000: 1; Element 71 : the method wherein the precursor zeolite is one or more of a 12-member ring zeolite, a 12-member ring three-dimensional zeolite, a zeolite having an FAU or BEA intermediate framework structure, a Beta zeolite, a Y zeolite, an L zeolite, an USY zeolite, and combinations thereof; Element 72: the method wherein the precursor zeolite is a USY zeolite; Element 73: the method wherein the modified zeolitic catalyst is characterized by an alpha value of not more than about 3; Element 74: the method wherein the modified zeolitic catalyst is characterized by a collidine uptake of not more than about 10 pg/mol; Element 75: the method further comprising: contacting a hydrocarbon feed stream with the modified zeolitic catalyst under conditions effective to convert the hydrocarbon feed stream to a hydrocarbon product stream comprising one or more of a gasoline fraction, benzene, toluene, xylene, and blends thereof; Element 76: Element 75 and wherein the hydrocarbon feed stream comprises one or more of full-range naphtha, hydrotreated naphtha, virgin naphtha, intermediate cracked naphtha, fluid catalytic cracker naphtha, straight run naphtha, coker naphtha, delayed coker naphtha, steam cracker naphtha, fluid coker naphtha, hydrocrackate, and blends thereof; Element 76: Element 75 and wherein the hydrocarbon feed stream comprises at least about 90 wt. % CVCx hydrocarbons; Element 77: Element 75 and wherein the hydrocarbon feed stream comprises at least about 30 wt. % paraffins; Element 78: Element 75 and wherein the hydrocarbon feed stream comprises at least about 45 wt. % paraffins; Element 79: Element 75 and wherein the conditions effective to comprise one or more of the following conditions: a reactor El temperature of at least about 450°C, a reactor WHSV of at least about 5 hours ¹, a EUEIC ratio of at least about 2.5: 1, a reactor pressure of about 215 psig (1480 kPa), or any combination thereof; Element 80: Element 75 and wherein the conditions comprise one or more of the following conditions: an El temperature of at least about 500°C, a pressure of not more than about 215 psig (1480 kPa), a WHSV of not more than about 5 hours ¹, and an H2:HC ratio of not more than about 2.5: 1; Element 81 : Element 77 and wherein the hydrocarbon product stream comprises a ratio of ethylbenzene to hydrocarbons comprising an aromatic ring with eight carbon atoms (A8 fraction) of not more than about 0.15.; Element 82: Element 77 and wherein the hydrocarbon product stream comprises at least about 46 wt. % aromatic hydrocarbons; Element 83: Element 77 and wherein product stream comprises at least about 80 wt. % of a C5+ fraction; Element 84: the method wherein the transition metal comprises at least one of the following: platinum, palladium, and nickel. Combinations of Elements include, but are not limited to, Element 67 in combination with one or more of Elements 68-84; Element 68 in combination with one or more of Elements 69-84; Element 69 in combination with one or more of Elements 70-84; Element 70 in combination with one or more of Elements 71-84; Element 71 in combination with one or more of Elements 72-84; Element 72 in combination with one or more of Elements 73-84; Element 73 in combination with one or more of Elements 74-84; Element 74 in combination with one or more of Elements 75-84; Element 75 in combination with one or more of Elements 76-84; Element 76 in combination with Element 75 and one or more of Elements 77-84; Element 77 in combination with Element 75 one or more of Elements 78-84; Element 78 in combination with Element 75 and one or more of Elements 79- 84; Element 79 in combination with Element 75 and one or more of Elements 81-84; Element 80 in combination with Element 75 and one or more of Elements 81-84; Element 81 in combination with Element 75 one or more of Elements 82-84; Element 82 in combination with Element 75 and one or more of Elements 83-84; and Element 83 in combination with Element 84.

[0109] Another nonlimiting example embodiment includes a method of preparing a modified zeolitic catalyst comprising: doping a precursor zeolite with a Group 1 metal cation, a Group 2 metal cation, or a combination thereof, to form a metal-doped zeolite; treating the metal-doped zeolite with one of the following: acid, steam, and a combination thereof, to form a modified zeolite to form a modified zeolite having one or more of a bulk silica-to-alumina ratio of at least about 80: 1 and a framework silica-to-alumina ratio to at least about 80: 1; and contacting the modified zeolite with a transition metal to form a modified zeolitic catalyst having enhanced dehydrocyclization activity. Optionally the embodiment may include one or more of the following elements: any of Elements 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, Element 85: the method wherein the step of treating occurs before the stop of doping; and Element 86: the method wherein the Group 1 or Group 2 metal cations comprises one or more of the following elements: sodium, barium, magnesium, calcium, and potassium. Combinations of Elements include, but are not limited to, Element 67 in combination with one or more of Elements 68-86; Element 68 in combination with one or more of Elements 69-86; Element 69 in combination with one or more of Elements 70-86; Element 70 in combination with one or more of Elements 71- 86; Element 71 in combination with one or more of Elements 72-86; Element 72 in combination with one or more of Elements 73-86; Element 73 in combination with one or more of Elements 74- 86; Element 74 in combination with one or more of Elements 75-86; Element 75 in combination with one or more of Elements 76-86; Element 76 in combination with Element 75 and one or more of Elements 77-86; Element 77 in combination with Element 75 one or more of Elements 78-86; Element 78 in combination with Element 75 and one or more of Elements 79-86; Element 79 in combination with Element 75 and one or more of Elements 81-86; Element 80 in combination with Element 75 and one or more of Elements 81-86; Element 81 in combination with Element 75 one or more of Elements 82-86; Element 82 in combination with Element 75 and one or more of Elements 83-86; Element 83 in combination with one or more of Elements 84-86; Element 84 in combination with one or more of Elements 85-86; and Element 85 in combination with Element 86

[0110] Another nonlimiting example embodiment includes a system comprising: a hydrocarbon feed stream inlet configured and arranged to receive a hydrocarbon feed stream; at least one reactor comprising at least one catalyst bed, the catalyst bed comprising at least one modified zeolitic catalyst, wherein the modified zeolitic catalyst comprises a transition metal and a modified zeolite characterized by one or more of the following: a bulk silica-to-alumina ratio of at least about 40: 1 and a framework silica-to-alumina ratio of at least about 40: 1 ; and a hydrocarbon product stream outlet configured and arranged to receive a hydrocarbon product stream. Optionally, the embodiment may include one or more of the following elements: Element 87 : the system wherein the modified zeolitic catalyst further comprises a Group 1 or Group 2 metal cation; Element 88: the system wherein the catalyst bed is a fixed bed; Element 89: the system wherein the modified zeolite is characterized by one or both of a bulk silica-to-alumina ratio of at least about 80: 1 and a framework silica-to-alumina ratio of at least about 80: 1; Element 90: the system wherein the modified zeolite is characterized by a bulk silica-to-alumina ratio of greater than about 400: 1; Element 91: the system wherein the modified zeolite is characterized by a framework silica-to-alumina ratio of greater than about 500: 1 ; and Element 92: the system wherein the modified zeolite is characterized by a framework silica-to-alumina ratio of greater than about 2000: 1. Combinations of Elements include, but are not limited to, Element 87 in combination with one or more of Elements 88-92; Element 88 in combination with one or more of Elements 89-92; Element 89 in combination with one or more of Elements 90-92; Element 90 in combination with one or more of Elements 91-92; and Element 91 in combination with Element 92.To facilitate a better understanding of the embodiments of the present invention, the following examples of preferred or representative embodiments are given. In no way should the following examples be read to limit, or to define, the scope of the invention.

EXAMPLES

Example 1: Preparation of Catalysts.

Steamed Modified Zeolitic Catalysts

[0111] A USY precursor zeolite having a bulk silica-to-alumina ratio of at least 60 is extruded with a silica binder at a ratio of 80:20 (zeolite to binder) and then steamed at a temperature of 1500°F (815.6°C) to 1800°F (982.2°C) (982.2°C) for 1 hour to 5 hours and/or acid washed to reduce acidity and achieve the desired bulk and framework silica-to-alumina ratios and/or acidity. After steaming and/or acid washing, the zeolitic catalyst precursor is impregnated with 0.9% platinum, reduced in H2 then sulfided in 10 wt. % H2S.

Modified Zeolitic Catalysts with a Group 1 or Group 2 Metal

[0112] A USY zeolite precursor having a bulk silica-to-alumina ratio of at least 60 is extruded with a silica binder at a ratio of 80:20 (zeolite to binder) the optionally steamed at about 1500°F (815.6°C) to about 1800°F (982.2°C) for about 1 hour to about 5 hours and/or acid washed to reduce acidity. A Group 1 or a Group 2 metal is then introduced by impregnation. Specific examples of useful Group 1 and Group 2 metals include magnesium, calcium, barium, potassium, and sodium. The zeolitic catalyst precursor is then reduced in Fh then sulfided in 10 wt. % FhS. Pt/Re Chlorided Alumina Catalysts

[0113] Pt/Re chlorided alumina catalysts are prepared by loading 1 wt. % chlorine onto extruded Pt/Re on high density aluminum oxide followed by reducing in Fh and sulfiding in 10 wt. % H2S.

Example 2: Properties of Several Embodiments of Modified Zeolitic Catalysts

[0114] Data herein will be provided for different modified zeolitic catalysts prepared by a variety of methods. The precursor zeolite, referred to as USY A or USY B, has properties as shown in Table 1 below. Table 1 also reports the effects on alpha value and collidine uptake after extruding each with 80:20 zeolite:silica followed by steaming for 1 hour at either 1500°F (815.6°C) or 1700°F.°F (926.7°C).

Table 1

[0115] FIG. 2 shows IR spectra of absorbed pyridine on several embodiments of modified zeolitic catalysts prepared as follows:

• USY B steamed for 1 hour at 1500°F (815.6°C)

• USY B + 0.2 wt. % Na

• USY B + 0.21 wt. % Mg

[0116] While not wishing to be bound by theory, the bigger peak at 1550 cm ¹ for the modified zeolitic catalyst comprising magnesium may indicate increased Bronsted acid activity.

Example 3: The Experimental Hydrocarbon Feed Stream

[0117] To illustrate the activity of a modified zeolitic catalyst, a hydrocarbon feed stream having naphtha range boiling fraction is conveyed through a catalyst bed having a modified zeolitic catalyst prepared as described in Example 1. The hydrocarbon feed stream is n-heptane or a feedstock having the properties disclosed in Table 2 below.

Table 2

[0118] The feedstock as described in Table 2 is pre-treated by passing it through molecular sieve material to remove water and, if needed, through a sulfur adsorbent to adjust sulfur content to about 0.6 ppm.

Example 4: Reactor Conditions

[0119] All catalysts are tested either in an isothermal 16-channel fixed bed unit (< 1 cc catalyst) or in a fixed-bed isothermal microunit (1-5 cc catalyst). The reactor is operated at an inlet temperature of between 450°C and 525°C, a pressure of 125 psig (861 kPa) to 350 psig (2410 kPa), a EhiHC ratio of 1.25: 1 to 5: 1, and a WHSV of 1 hour ¹ to 15 hours ¹. In the following examples, specific reactor operating conditions within these ranges are indicated.

Example 5: Characterizing Hydrocarbon Product Stream/s

[0120] Hydrocarbon product streams are analyzed by gas chromatography. Octane is calculated according to the model described by Ghosh, P. et al. (2006)“Development of Detailed Gasoline Composition-Based Octane Model.” Ind. Eng. Chem. Res., 45(1), pp. 337-345, which is hereby incorporated by reference with respect to its disclosure of determining octane rating (and RON) from data obtained from gas chromatography analyses.

Example 6: Improved Aromatic Yield

[0121] FIG. 3 illustrates data related to the effect of a modified zeolitic catalyst on aromatic yield (wt. %) in a hydrocarbon product stream. It appears that, at equivalent LPG yield, a higher aromatics yield is derived from a modified zeolitic catalyst than a Pt/Re chlorided alumina catalyst. The modified zeolitic catalyst is prepared from a USY A precursor zeolite, extruded with silica at a zeolite: silica ratio of 80:20, steamed for 1 hour at 1500°F (815.6°C), then impregnated with 0.9 wt. % Pt. The hydrocarbon feed stream is n-heptane. The reactor is operated at an inlet temperature of 500°C, a pressure of 350 psig (2410 kPa), and an H2:HC ratio of 5: 1. The WHSV is varied to vary yield on both axes.

Example 7: High Yield, High Octane

[0122] FIG. 4 illustrates data related to the effect of a modified zeolitic catalyst on the C5+ fraction yield (wt. %) of a hydrocarbon product stream. It appears that when the RON of the C5+ fraction is greater than 93 (which is the most industrially relevant), at equivalent C5+ fraction RON, a higher C5+ fraction yield is derived from a modified zeolitic catalyst. The modified zeolitic catalyst is prepared from a USY A precursor zeolite, extruded with silica at a zeolite: silica ratio of 80:20, steamed for 1 hour at 1500°F (815.6°C), then impregnated with 0.9 wt. % Pt. The hydrocarbon feed stream is naphtha as described in Table 2 but having a sulfur content of 1.5 ppm. Reactor operating conditions are the same as described in Example 6.

[0123] As noted in this disclosure, when converting a hydrocarbon feed stream that contains naphthenes, paraffm-to-aromatic conversion by a modified zeolitic catalyst may not initially recognizable, as conversion of naphthenes to aromatics equilibrates fast and may overwhelm the dehydrogenation reactions. However, once naphthenes are converted to aromatics, the selectivity advantages of the paraffm-to-aromatic conversion become predominant. This can be seen in FIG. 4, where at low conversion (octane number), the C5+ fraction yield appears to be higher for the Pt/Re chlorided alumina; however, at high conversion, the selectivity of a modified zeolitic catalyst for converting paraffins to aromatics dominates, and for the same conversion, a higher C5+ fraction yield is observed. This is because while the modified zeolitic catalyst is converting paraffins to aromatics to increase octane number while maintaining C5+ fraction yield, a Pt/Re chlorided alumina catalyst is increasing octane rating through hydrocracking (forming a C1-C4 fraction), decreasing C5+ fraction yield. FIG. 5 illustrates the same trend with respect to aromatic yield (same feedstock/reactor conditions as FIG. 4) and FIG. 6 illustrates the same trend with respect to BTX yield (same feedstock/reactor conditions as FIG. 4). At high conversion, a modified zeolitic catalyst appears to yield a greater aromatic and BTX yield than a Pt/Re chlorided alumina catalyst. Similarly, FIG. 7 (same feedstock/reactor conditions as FIG. 4) reports A6-A8 yield versus product stream octane. At high conversion, a modified zeolitic catalyst appears to yield a greater A6-A8 yield.

[0124] FIG. 8 illustrates data related to enhancing this effect that, to a point, with increased steaming. Three modified zeolitic catalysts prepared from a USY A precursor zeolite extruded with silica at a zeolite: silica ratio of 80:20 then steamed at 1500°F (815.6°C) for 1, 2, or 5 hours before impregnating with 0.9 wt. % Pt are used as reforming catalysts. Reactor conditions are the same as in FIG. 4 and the feedstock is as described in Table 2. Notably, steaming for 5 hours appears to be beneficial only until a certain product stream conversion is reached (RON ~ 91). Similarly, FIG. 9 (same feedstock/reactor conditions as FIG. 4) reports the Cri and G, cyclic hydrocarbon yield for the same three modified zeolitic catalysts shown in FIG. 7.

Example 8: Non-Acidic Metal Cations Decrease Cracking

[0125] FIG. 10 illustrates data related to the effect of impregnating a modified zeolite or a zeolitic catalyst precursor with a Group 1 or Group 2 metal cation on the C1-C4 fraction yield. The modified zeolitic catalysts depicted in FIG. 10 are prepared from a USY B precursor zeolite, extruded with silica at a 80:20 zeolite: silica ratio, steamed for 1 hour at 1500°F (815.6°C), then impregnated with 0.9% Pt (filled points without labels). A second set of modified zeolitic catalysts are prepared from USY B zeolite precursors extruded with silica at a 80:20 zeolite: silica ratio, not steamed, then impregnated with a Group 1 or Group 2 metal cation (open points, metal cation labeled) and 0.9 wt. % Pt. The hydrocarbon feed stream is n-heptane and the reactor is operated at the conditions described in Example 6. Notably, the modified zeolitic catalysts containing Group 1 or Group 2 metal cations produce a hydrocarbon product stream with a lower C4- yield, indicating a modified zeolitic precursor having a Group 1 or Group 2 metal may exhibit reduced cracking activity. In fact, FIG. 11 data related to an increased yield of toluene in the hydrocarbon product stream for several of the modified zeolitic catalyst identified in FIG. 10 above, thus indicating that the reduced cracking activity coincides with an increased selectivity for dehydrocyclization. Example 9: Selectivity for Dehydrocyclization

[0126] FIG. 12 data related to improved C5 and Ce cyclic hydrocarbon yield when using a modified zeolitic catalyst impregnated with magnesium. Four example modified zeolitic catalyst are prepared as follows (each precursor zeolite is extruded with silica at an 80:20 zeolite: silica ratio, and, after steaming, impregnated with 0.9 wt. % Pt):

• USY A, steamed 1 hour at 1500°F (815.6°C), 0.05 wt. % Mg added;

• USY B, steamed 5 hours at 1500°F (815.6°C), 0.21 wt. % Mg added;

• USY A, steamed 1 hour at 1500°F (815.6°C), 0.025 wt. % Mg added;

• USY A, steamed 1 hour at 1500°F (815.6°C).

[0127] Reactor operating conditions are the same as in Example 6. The hydrocarbon feed stream is naphtha as described in Table 2. Notably, at equivalent C5+ fraction RON, the Mg- impregnated modified zeolitic catalysts have a loading-dependent increased yield of cyclic hydrocarbons, indicating that the cation increases the selectivity for dehydrocyclization. FIG. 13 confirms this, plotting cyclic hydrocarbon yield from the same experiment in FIG. 12 against the corresponding C1-C4 yield, illustrating a decreased selectivity for cracking.

Example 10: Resistance to Coking

[0128] The modified zeolitic catalysts disclosed herein may be resistant to coking, thus allowing for longer intervals before needing regenerating which may optionally be traded for reactor conditions that favor formation of high-octane gasoline and/or high BTX yield. FIG. 14 reports the decrease in product stream C5+ fraction octane with respect to run time (TOS) for a modified zeolitic catalyst (closed points/dotted line) and a Pt/Re chlorided alumina catalyst (open points/dashed line). The modified zeolitic catalyst is prepared from a USY A precursor zeolite steamed for 1 hour at 1500°F (815.6°C). The reactor is operated at an inlet temperature of 500°C, a pressure of 350 psig (2410 kPa), an FUHC ratio of 5: 1, and a WHSV of 10 hours ¹. The hydrocarbon feed stream is naphtha as reported in Table 2, but having a sulfur content of 1.5 ppm. The octane rating of the hydrocarbon product stream derived from the modified zeolitic catalyst declines at a slower rate than the octane rating of the hydrocarbon product stream derived from the Pt/Re chlorided alumina catalyst. FIG. 15 illustrates data related to the same trend using a modified zeolitic catalyst prepared by steam treating a USY B precursor zeolite for 5 hours at 1500°F (815.6°C). The hydrocarbon feed stream and operating conditions of the reactor are the same as in FIG. 14. At the end of the run in FIG. 15, the accumulated coke on the modified zeolitic catalyst is 2.1 wt. %, whereas the chlorided alumina catalyst accumulates 6.6 wt. % coke.

Example 11: Compatibility with Severe Reaction Conditions

[0129] The resistance to coking may allow for more severe reactor conditions that favor formation of a hydrocarbon product stream having a higher octane. FIG. 16 illustrates a smaller decrease in product stream octane with respect to run time (TOS) for a low acid modified zeolitic catalyst (dotted line) as compared to a Pt/Re chlorided alumina catalyst (dashed line). Reactor conditions include an inlet temperature of 500°C, a pressure of 215 psig (1480 kPa), an FUHC ratio of 2.5: l, and a WHSV of 1.5 hour ¹. FIG. 17 and 18 plot hydrocarbon product stream octane and C5+ yield, respectively, as a function of run time (TOS) for a modified zeolitic catalyst prepared from a USY A precursor zeolite extruded with silica at an 80:20 zeolite: silica ratio, steamed for 1 hour at 1500°F (815.6°C), and impregnated with 0.9% Pt and a Pt/Re chlorided alumina catalyst (dashed line). Initial reaction conditions (left of the vertical line) are as follows:

• Pt/Re chlorided alumina: 522°C, 215 psig (1480 kPa), FUHC ratio = 2.5: 1, and 1.0 hour ¹ LHSV (liquid hourly space velocity); • Modified zeolitic catalyst: 500°C, 215 psig (1480 kPa), fkiHC ratio = 2.5: 1, and 1.0 hour ¹ LHSV.

[0130] The hydrocarbon feed stream is naphtha as described in Table 2 having a sulfur content of 0.5 ppm. At and left of the vertical line, reactor operating conditions are as follows:

• Pt/Re chlorided alumina: 522°C, 215 psig (1480 kPa), H2:HC ratio = 2.5: 1, and 1.0 hour ¹ LHSV (unchanged);

• Modified zeolitic catalyst: 500°C, 150 psig (1030 kPa), H2:HC ratio = 1.5: 1, and 1.0 hour ¹ LHSV.

[0131] FIG. 17 shows data related to more severe conditions that favor the higher octane rating, a modified zeolitic catalyst exhibits a similar rate of declined octane. In FIG. 18, the more severe conditions to the left of the vertical line (same initial and changed reactor conditions as FIG. 17) drastically increase the C5+ yield compared to a Pt/Re chlorided alumina catalyst. In FIG. 19, the effect of decreasing the reactor pressure on the BTX yield is illustrated for a Pt/Re chlorided alumina catalyst and a modified zeolitic catalyst prepared from a USY A precursor zeolite steamed for 1 hour at 1500°F (815.6°C). The reactor is operated at an inlet temperature of 500°C, an H2:HC ratio of 5: 1 and a WHSV of 3 hours ¹. The hydrocarbon feed stream is naphtha as described in Table 2, but having a sulfur content of 1.5 ppm. In FIG. 20, the effect of decreasing the H2:HC ratio on the A8 yield is illustrated for a Pt/Re chlorided alumina catalyst and a modified zeolitic catalyst prepared from a USY A precursor zeolite steamed for 1 hour at 1500°F (815.6°C). The reactor is operated at an inlet temperature of 500°C, 350 psig 2410 kPa), and a WHSV of 3 hours f The hydrocarbon feed stream is naphtha as described in Table 2.

Example 12: Decreased Ethylbenzene

[0132] Ethylbenzene is particularly undesirable when the aromatics fraction of the hydrocarbon product stream is processed for para-xylene production since these two hydrocarbons are difficult to separate. The modified zeolitic catalysts described herein result in a decreased ethylbenzene yield. For example, FIG. 21 reports the ratio (weight or molar) of ethylbenzene to the A8 fraction in the hydrocarbon product stream as a function of the octane of the hydrocarbon product stream. The two example modified zeolitic catalysts depicted in FIG. 21 are prepared as follows (each precursor zeolite is extruded with silica at an 80:20 zeolite: silica ratio, and, after steaming, impregnated with 0.9 wt. % Pt):

• USY A, steamed 1 hour at 1500°F (815.6°C);

• USY B, steamed 5 hours at 1500°F (815.6°C).

[0133] Reactor operating conditions include an inlet temperature of 500°C, an H2:HC ratio of 5.5: 1, a pressure of 350 psig (2410 kPa), and a WHSV of 1 hour ¹, 2 hours ¹, or 5 hours ¹. The hydrocarbon feed stream is naphtha as described in Table 2.

[0134] Therefore, the present invention is well adapted to attain the ends and advantages mentioned as well as those that are inherent therein. The particular embodiments disclosed above are illustrative only, as the present invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular illustrative embodiments disclosed above may be altered, combined, or modified and all such variations are considered within the scope and spirit of the present invention. The invention illustratively disclosed herein suitably may be practiced in the absence of any element that is not specifically disclosed herein and/or any optional element disclosed herein. All numbers and ranges disclosed above may vary by some amount. Whenever a numerical range with a lower limit and an upper limit is disclosed, any number and any included range falling within the range is specifically disclosed.

Claims

CLAIMS: The invention claimed is:

1. A method of preparing a modified zeolitic catalyst comprising:

treating a precursor zeolite having a bulk silica-to-alumina ratio and a framework silica-to- alumina ratio with one or more of acid, steam, and a combination thereof under conditions effective to prepare a modified zeolite having one or more of a bulk silica-to-alumina ratio of at least about 80: 1 and a framework silica-to-alumina ratio to at least about 80: 1 ; and

contacting the modified zeolite with a transition metal to form a modified zeolitic catalyst having enhanced dehydrocyclization activity as compared to the precursor zeolite.

2. A method of preparing a modified zeolitic catalyst comprising:

doping a precursor zeolite with a Group 1 metal cation, a Group 2 metal cation, or a combination thereof, to form a metal-doped zeolite;

treating the metal-doped zeolite with one of the following: acid, steam, and a combination thereof, to form a modified zeolite having one or more of a bulk silica-to-alumina ratio of at least about 80: 1 and a framework silica-to-alumina ratio to at least about 80: 1 ; and

contacting the modified zeolite with a transition metal to form a modified zeolitic catalyst having enhanced dehydrocyclization activity.

3. The method as in claim 2, wherein the step of treating occurs before the stop of doping.

4. The method as in any one of the preceding claims, wherein treating comprises steaming at a temperature of between about 750°F (398.9°C) to about 3000°F (1649°C) for a period of about 1 hour to about 5 hours.

5. The method as in any one of the preceding claims, wherein the bulk silica-to-alumina ratio of the modified zeolite is at least about 400: 1.

6. The method as in any one of the preceding claims, wherein the precursor zeolite is one or more of a 12-member ring zeolite, a 12-member ring three-dimensional zeolite, a zeolite having an FAU or BEA intermediate framework structure, a Beta zeolite, a Y zeolite, an L zeolite, an USY zeolite, and combinations thereof.

7. The method as in any one of the preceding claims, wherein the modified zeolitic catalyst is characterized by an alpha value of not more than about 3.

8. The method as in any one of the preceding claims, wherein the modified zeolitic catalyst is characterized by a collidine uptake of not more than about 10 pg/mol.

9. The method as in any one of claims 2-8, wherein the Group 1 or Group 2 metal cations comprises one or more of the following elements: sodium, barium, magnesium, calcium, and potassium.

10. The method as in any one of the preceding claims, further comprising:

contacting a hydrocarbon feed stream with the modified zeolitic catalyst under conditions effective to convert the hydrocarbon feed stream to a hydrocarbon product stream comprising one or more of a gasoline fraction, benzene, toluene, xylene, and blends thereof.

11. The method of claim 10, wherein the hydrocarbon feed stream comprises one or more of full-range naphtha, hydrotreated naphtha, virgin naphtha, intermediate cracked naphtha, fluid catalytic cracker naphtha, straight run naphtha, coker naphtha, delayed coker naphtha, steam cracker naphtha, fluid coker naphtha, hydrocrackate, and blends thereof.

12. The method of claim 10, wherein the hydrocarbon feed stream comprises at least about 90 wt. % C6-C8 hydrocarbons.

13. The method as in any of claims 10-12, wherein the hydrocarbon feed stream comprises at least about 30 wt. % paraffins.

14. The method as in any of claims 10-13, wherein the hydrocarbon feed stream is characterized by a N+2A value of less than about 90.

15. The method as in any of claims 10-14, wherein the conditions effective to comprise one or more of the following conditions: a reactor El temperature of at least about 450°C, a reactor WHSV of at least about 5 hours ¹, a H2:HC ratio of at least about 2.5: 1, a reactor pressure of about 215 psig (1480 kPa), or any combination thereof.

16. The method as in any one of claims 10-15, wherein the hydrocarbon product stream comprises a ratio of ethylbenzene to hydrocarbons comprising an aromatic ring with eight carbon atoms (A8 fraction) of not more than about 0.15.

17. The method as in any one of claims 10-13 or 16, wherein the hydrocarbon product stream comprises at least about 46 wt. % aromatic hydrocarbons, wherein the hydrocarbon product stream comprises at least about 80 wt. % of a C5+ fraction, or a combination thereof.

18. The method as in any one of claims 1-17, wherein the transition metal comprises at least one of the following: platinum, palladium, and nickel.

19. A system comprising:

a hydrocarbon feed stream inlet configured and arranged to receive a hydrocarbon feed stream;

at least one reactor comprising at least one catalyst bed, the catalyst bed comprising at least one modified zeolitic catalyst, wherein the modified zeolitic catalyst comprises a transition metal and a modified zeolite characterized by one or more of the following: a bulk silica-to-alumina ratio of at least about 40: 1 and a framework silica-to-alumina ratio of at least about 40: 1 ;

and a hydrocarbon product stream outlet configured and arranged to receive a hydrocarbon product stream,

wherein the modified zeobtic catalyst further comprises a Group 1 or Group 2 metal cation, wherein the catalyst bed is a fixed bed, and

wherein the modified zeolite is characterized by one or both of a bulk silica-to-alumina ratio of at least about 80: 1 and a framework silica-to-alumina ratio of at least about 80: 1.