CN101171212A

CN101171212A - Processes for the isomerization of paraffins of 5 and 6 carbon atoms with methylcyclopentane recovery

Info

Publication number: CN101171212A
Application number: CNA2006800158339A
Authority: CN
Inventors: D·J·谢克特尔勒; L·H·赖斯
Original assignee: Universal Oil Products Co
Current assignee: Honeywell UOP LLC; Universal Oil Products Co
Priority date: 2005-03-11
Filing date: 2006-03-10
Publication date: 2008-04-30
Also published as: AU2006223160A1; WO2006099287A1; EP1856015A4; KR20070106591A; RU2007137666A; AU2006223160B2; CA2601211C; BRPI0608728A2; RU2364583C2; KR100945406B1; CA2601211A1; EP1856015A1

Abstract

In an isomerization process where the isomerization effluent (108) is fractionated in a deisohexanizer (116) to provide an overhead (118) containing dimethylbutanes and a higher boiling fraction (122) containing normal hexane, the higher boiling is contacted with a selectively permeable membrane (124) to provide a retentate containing methylcyclopentane (128). If desired, the normal hexane-containing permeate can be recycled for isomerization. The preferred membranes are sieving membranes having a C6 Permeate Flow Index of at least 0.01 and a C6 Permeate Flow Ratio of at least 1.25:1.

Description

Methylcyclopentane reclaims the isomerization method that has the paraffinic hydrocarbons of 5 and 6 carbon atoms down

Background technology

The isomerization that the present invention relates to have the paraffinic hydrocarbons of 5 and 6 carbon atoms is improved one's methods, thereby the isomerization product that for example provides research octane number (RON) to improve is used for calling in gasoline pool, particularly uses the aforesaid method that takes off the isohexane tower.

The method that is used for the paraffinic hydrocarbons that isomerization of paraffinic hydrocarbons one-tenth is more highly branched obtains broad practice.The industrial isomerization method of particularly important is used for improving branching, contains 4-8 carbon atom, the especially octane value of the refiner streams of the paraffinic hydrocarbons of 5 and 6 carbon atoms thereby improve.Usually with this isomerization product and refinery's reformer effluent blend so that the blended gasoline mixture with required research octane number (RON) (RON) to be provided.

Isomerization process is carried out to thermodynamic(al)equilibrium.Therefore, it is low that isomerization product still contains octane value, thereby reduce the n-paraffin of the octane value of this isomerization product.If appropriate high-octane rating blend materials flow such as alkylide and reformer effluent are available, and need then there be these n-paraffin in the tolerable isomerization product than low octane rating as 85 and the gasoline of 87RON.

Under the situation of RON isomerization product of having relatively high expectations, by separation of normal paraffins from isomerization product and make them be circulated to isomerization reactor to improve isomerization method.Thereby, the n-paraffin that reduces octane value is removed from isomerization product, and they increase the feeding part of the more highly branched paraffinic hydrocarbons that changes into expectation to returning of isomerization reactor.

Be used for using for disclosed fractionation by adsorption among the US 4,717,784 and 4,804,802 for example and distillatory from the main method of isomerization product separation of normal paraffins.The isomerization method of the most frequently used circulation n-paraffin uses and takes off the isohexane tower.Taking off the isohexane tower is one or more distillation towers, obtains comprising branching C therein ₆Paraffinic hydrocarbons such as dimethylbutane (2,2-dimethylbutane and 2, the 3-dimethylbutane) and more the overhead product of light constituent is as isomerization product, for example be used for blended gasoline, and will comprise the component of normal hexane and similar boiling point such as methylpentane (2-methylpentane and 3-methylpentane) and the side line materials flow of methylcyclopentane and be circulated to isomerization reactor.The problem of taking off the isohexane tower is to comprise the low Skellysolve A of RON value than low-boiling products stream.

Utilize fractionation by adsorption rather than take off the isohexane tower to make it possible to remove Skellysolve A, providing thus often is the motor spirit of the high RON of 91-93.

Also proposed to separate branched paraffin and linear alkanes, but film still has to seek actual commercial applications.US 5,069, and 794 disclose the microporous membrane that contains the crystalline molecular sieve material.The 11st capable reaching discloses may using of this film thereafter on the 8th hurdle, comprises separating of linear alkanes and branched paraffin.Referring to US 6,090,289, it discloses can be as the laminated composites that contains molecular sieve of film in addition.Can use among may the separating of this film in that the row beginning of the 13rd hurdle the 6th is disclosed, comprise separating of branched paraffin and n-paraffin.US 6,156, and 950 and 6,338,791 have discussed and can be applied to branched paraffin and the isolating permeation sepn technology of n-paraffin, and have described some separation scheme relevant with isomerization.U. S. application 2003/0196931 discloses the two-stage isomerization method of the hydrocarbon charging upgrading that is used to make 4-12 carbon atom.

Recently, Bourney etc. disclose the method for producing stop bracket gasoline in WO 2005/049766, and it removes Skellysolve A with film especially from the isomerization materials flow that derives from the overhead product that takes off the isohexane tower.Come the cleaning fluid of the side stream of autospasy isohexane tower as this membrane permeate side.Penetrant and cleaning fluidic mixture are circulated to isomerization reactor.In the computer simulation of the use of MFI film, the embodiment 1 of this publication shows on based on aluminum oxide: the film surface-area of always removing 500 square metres of the Skellysolve A needs of 95 quality % in the overhead product of autospasy isohexane column distillation tower.Under the flow velocity (75000kg/hr has 20.6 quality % Skellysolve As) of permeator charging, the flux of used Skellysolve A appears as 0.01 mol/m in this simulation under 300 ℃ ²The s level.The RON that removes the product of Skellysolve A is said to be 91.0.

The side stream that uses such as Bourney come autospasy isohexane tower makes valuable high-octane rating compound such as methylpentane and methylcyclopentane loop back isomerization reactor as the cleaning fluid of membrane sepn.In table 1, the concentration of record methylcyclopentanes such as Bourney is 9.7 quality %.There is not methylcyclopentane in the product stream.In addition, the cleaning materials flow comprises 4.5 quality % and is circulated to 2 of isomerization reactor equally, the 3-dimethylbutane.Because isomerization reaction distributes isomer towards balance, therefore with regard to RON, their per passes are just sacrificed the yield of high RON fuel.

The use of zeolite membrane is considered to separate the appropriate technology of linear molecule.Referring to for example the 0008th and 0032 section.US 6,818, and 333 disclose thin zeolite membrane, it is said that it has at least 610 ^-7Mol/m ²The normal butane rate of permeation of sPa and normal butane are to the selection rate of Trimethylmethane at least 250.

The variation of environment and fuel efficiency rules has profound influence to the demand of more high-octane isomerization product.For example, the requirement that reduces benzene content in gasoline makes and must improve the octane value of isomerization product, and will require " one way (once-through) " isomerization process to be modified into to make n-paraffin separate and be circulated to the technology of isomerization reactor.Even the technology that may require existing use to take off the isohexane tower provides the isomerization product of octane value rising.

Therefore, seek method viable economically and simple to operate is taken off isohexane top of tower overhead product with raising octane value.

For following argumentation the of the present invention, define following film properties.

Micropore

Micropore and microporosity are meant that effective diameter is the hole of 0.3-2 nanometer.

Mesopore

Mesopore and mesoporosity are meant that effective diameter is the hole of 2-50 nanometer.

Macropore

Macropore and macroporosity are meant the hole of effective diameter greater than 50 nanometers.

Nano particle

Nano particle is the principal dimension particle of 100 nanometers at the most.

Molecular sieve

Molecular sieve is to have micro porous material, and can be unbodied, part is unbodied or crystallization, can be zeolite, polymkeric substance, metal, pottery or carbon.

Sieve membrane

Sieve membrane is the composite membrane that contains continuous or discrete selective separation medium, and this separating medium comprises the molecular sieve barrier.Barrier is to flow to the structure that exists in this film for selective resistance baffle body.In the successive sieve membrane, molecular sieve itself forms the successive layers of attempting not to be with defective.The successive barrier can comprise other material, as has the situation of mixed substrate membrane containing nano-grade molecular sieve.Discontinuous sieve membrane is the discontinuous set zoarium of molecular sieve barrier, wherein exists between the particle of molecular sieve or zone at interval or the space.These intervals or space can comprise or fill other solid material.This sieve particle or zone are described barrier.Can be by the separation that sieve membrane is realized based on the spatial property of component to be separated.Other factors also may influence infiltration.A kind of factor is that component and molecular screen material have or not adsorptivity.Another factor is the interaction of component to be separated in the microporous molecular sieve structure.For example, for some zeolite molecular sieves, in the hole molecule for example the existence of normal hexane hinder the 2-methylpentane and enter this hole and can surpass obstruction another normal hexane molecule.Therefore, only appear for not providing separating of n-paraffin and branched paraffin a large amount of optionally zeolites in fact can provide bigger separation selectivity from the viewpoint of molecular size.

C ₆Permeate flow index

The rate of permeation of sieve membrane, promptly given component often change along with the variation of condition such as temperature and pressure (absolute and differential pressure) by the speed of this film of given thickness.Thereby, for example,, can record different infiltration rates comprising that all other parameter constants of pressure reduction, the absolute pressure of permeate side are under the situation of 1000kPa and this pressure is under the situation of 5000kPa.Therefore, use C in this article ₆Permeate flow index is described sieve membrane.By measuring normal hexane (preferably at least 95 quality % normal hexanes) pure basically under 1000kPa retentate side absolute pressure and 100kPa permeate side absolute pressure at about 150 ℃ of C that determine given film down through the speed (mol/second) of film ₆Permeate flow index.C ₆The infiltration rate of every square metre of retentate side surface-area of permeate flow index reflection, but do not carry out stdn with thickness.Therefore, the C of given film ₆Permeate flow index is a unit with the mol normal hexane that every square metre of retention side form of per second surface-area is permeated.

C ₆The permeate flow ratio

The C of given sieve membrane ₆The permeate flow ratio is C ₆Permeate flow index (normal hexane) and i-C ₆The ratio of permeate flow index is wherein pressed and C ₆The mode that permeate flow index is identical but be to use pure basically dimethylbutane (no matter 2,2-dimethylbutane and 2, the distribution between the 3-dimethylbutane) (preferably at least 95 quality % dimethylbutanes) to determine i-C ₆Permeate flow index.

Summary of the invention

By the present invention, the isomerization method that is used to improve the paraffinic feed octane value that contains 5 and 6 carbon atoms is improved, wherein this method provides the more lower boiling cut of dimethylbutane and the cut that contains normal hexane of higher of containing with taking off the isohexane tower.According to the present invention, film is used for from the component of the cut recovery higher octane that contains normal hexane of higher, as methylcyclopentane and dimethylbutane.The component of these higher octane can be used for blended motor fuel.Because only part isomerization effluent experience film is handled,, improve the economic feasibility of using film thus so can reduce required film surface-area.

Preferably, will be used for isomerization from the penetrant circulation that contains normal hexane to small part of membrane sepn.Because the concentration height in the penetrant in the concentration ratio higher cut of normal hexane, the normal hexane of the circulation same amount of therefore comparing does not still have the benefit of membrane sepn, and the round-robin volume is reduced.The ability that the inventive method reduces to be circulated to the volume of isomerization reactor can provide some advantages.For example, reduce the circulation volume and make that the charging of isomerization reactor can increase under the given transformation efficiency, thereby improve the processing power of isomerization reactor.In addition, by reducing otherwise can be circulated to the higher octane component of isomerization reactor such as the amount of methylcyclopentane and dimethylbutane, the equilibrium property of isomerization reaction makes the per unit raw material can produce more higher octane product.

The wide aspect of the inventive method comprises:

A. comprising under the isomerisation conditions that isomerization catalyst exists, isomerization comprises the raw material of the paraffinic hydrocarbons with 5 and 6 carbon atoms, wherein the raw material of at least 15 quality % is a linear alkanes, thereby but provides and contain linear alkanes concentration less than the isomerization effluent in the described raw material

B. be distilled to small part, preferred at least 90 quality %, most preferably whole basically isomerization effluent with provide contain dimethylbutane and more light paraffins than low boiler cut, and comprise normal hexane, methylpentane, dimethylbutane and methylcyclopentane contain the normal hexane cut

C. make to small part, preferred at least 90 quality %, most preferably whole basically normal hexane cuts that contain from step b contact under the condition that comprises enough film surface-area and described both sides differential pressure of membrane with the retentate side of selectively permeable membrane, thereby the retention fraction that provides methylcyclopentane and dimethylbutane concentration to improve, and the penetrant fraction that normal hexane and the raising of methylpentane concentration are provided in the permeate side of described film, described penetrant fraction comprises at least 75, preferred at least 90 quality % contact with described film contain normal hexane contained in the normal hexane cut and

D. shift out described retention fraction from step c.

With preferably to small part, more preferably at least 90 quality %, most preferably the penetrant fraction of whole basically step c is circulated to step a.

Comprise in the described penetrant fraction preferred at least 25, more preferably at least 30 quality % contact with described film contain methylpentane contained in the normal hexane materials flow.In many cases, in total penetrant the concentration of normal hexane less than 90 quality %, for example 25-90, as 40-80 quality %.Aspect some of the inventive method, the retention fraction that is shifted out greater than 10, for example 15-50 quality % contact with described film contain the normal hexane cut.Thereby, be circulated to the isomerized volume ratio of step a and do not experiencing in the same sampling technology the described membrane sepn little except containing the normal hexane cut.

The retention fraction of steps d comprises the methylcyclopentane of a great deal of, thereby has the octane value that makes us attracting.Often at least 50, the methylcyclopentane that contains in the normal hexane cut that contacts with described film of preferred at least 80 quality % is retained in the described retention fraction.

Because boiling point is approaching, monomethyl pentane and dimethylbutane separation difficulty are taken off the isohexane tower thus and are not only used a large amount of distilling trays, 80 blocks of column plates often, and use big backflow material and charge proportion, for example 2: 1 to 3: 1.Therefore, take off the suitable reboiler heat of operational requirement of isohexane tower.The method of the application of the invention, the described dimethylbutane that contains the considerable part that comprises in the normal hexane cut is retained in the retention fraction, is used for motor spirit and is in harmonious proportion pond (motor fuel pool) thereby reclaim with methylcyclopentane.The distillation procedure of preferred steps b will make the described normal hexane cut that contains comprise dimethylbutane, its content for example at least 2, the dimethylbutane for comprising in the isomerization effluent of 5-30 quality % from step a sometimes.The preferred described dimethylbutane that comprises in the normal hexane cut that contains of at least 30, more preferably at least 70 quality % is retained in the retention fraction.Thereby, the retention that shifts out can be used as in motor spirit or the adding mediation pond so that motor spirit to be provided.Therefore,, can reduce reflux ratio, reduce 10-50% sometimes for the existing isohexane tower that takes off, thus not only energy-conservation but also do not have immoderation to lose the octane value of product.

Preferred described film is C ₆Permeate flow index is at least 0.01, more preferably at least 0.02 and C ₆Permeate flow is than being at least 1.25: 1, more preferably at least 1.3: 1 and the sieve membrane of 1.35: 1 to 5: 1 or 6: 1 often.

The invention still further relates to the device that is fit to carry out the inventive method.Aspect wide, device of the present invention be used to comprise have 5 and 6 paraffinic hydrocarbonss between the carbon atom the raw material isomerization so that the device of gasoline fraction to be provided, it comprises:

A. the isomerization reactor (106) that is adapted at entering the mouth and receives raw material and have outlet,

B. dehexanizing column (116), it has the inlet that is communicated with the outlet fluid of isomerization reactor (106), be fit to through pipeline (118) shift out than low boiler cut than lower boiling outlet, the outlet that side stream is provided and higher outlet; With

C. membrane separation apparatus (124), it has the permeate side that feeding side inlet that the outlet fluid of side stream is communicated with is provided, exports with the feeding side that is communicated with than pipeline (118) fluid of lower boiling outlet from dehexanizing column (116) and is communicated with the inlet fluid of isomerization reactor (106) with dehexanizing column (116) and exports.

Brief Description Of Drawings

Fig. 1 is the diagram according to method of the present invention of using stabilizer tower before taking off the isohexane tower.

Detailed Description Of The Invention

Isomerization

Any suitable paraffinic feed that contains can be used for method of the present invention. Feed naphtha Be commonly used for the raw material of isomerization process. Feed naphtha comprises alkane, cycloalkane and aromatic compounds, And can comprise a small amount of alkene in the gasoline boiling range. Operable raw material comprise straight-run naphtha, Natural gasoline, synthetic naphtha, thermal gasoline, catalytically cracked gasoline, part reformed naphtha or next Raffinate from the aromatic compounds extraction. Described raw material is made of full boiling range naphtha basically, perhaps In 0-230 ℃ boiling range. Usually this raw material is that initial boiling point is that 10-65 ℃ and final boiling point are 75-110 ℃ light naphthar; Preferred final boiling point is less than 95 ℃.

Feed naphtha generally comprises a small amount of sulphur compound, amounts to less than 10/1000000ths in element Mass parts (mppm). Preferably by contaminated raw material by conventional pre-treatment step such as hydrotreatment, Hydrofinishing or hydrodesulfurization make impurity for example sulfur-containing compound, nitrogen-containing compound and oxygenatedchemicals branch Do not change into the H that can separate with hydrocarbon by fractionation₂S、NH ₃And H₂O, thus this naphtha made Raw material. The preferred employing of this conversion comprises inorganic oxide carrier and is selected from periodic table VIB (IUPAC 6) and the catalyst known in the art of VIII (IUPAC 9-10) family's metal. Water can be by filling When alkali plays the effect that weakens acidity of catalyst, sulphur is by making platinosis make the temporary transient inactivation of catalyst. Raw material hydrotreatment mentioned above has reduced the oxygenate of generation water usually, and makes the sulphur compound deactivation To suitable level, generally do not need other approach such as adsorption system from hydrocarbon flow, to remove desulfuration and water. Within the scope of the invention, this optional pre-treatment step is included in the inventive method combination.

The key component of preferred feedstock is that each molecule has 4-8 carbon atom (C₄-C ₈), C particularly₅-C ₆Cycloalkane and acyclic alkane, the aromatic hydrocarbons of small amount and alkene also can exist. Usually, C₇More the concentration of restructuring branch is less than 20 quality % of raw material, C₄More the concentration of light component is less than former The material 20, preferably less than 10 quality %. C in the preferred feedstock₅With C₆The mass ratio of component is 1: 10-1: 1.

Although the total content of ring-type hydro carbons in raw material is not particularly limited, raw material generally comprises 2-40 quality % comprises the ring-type component of cycloalkane and aromatic compounds. Contained in the feed naphtha Although aromatic compounds generally amount to less than alkane and cycloalkane, can account for the 2-20 of total amount Quality %, more generally 5-10 quality %. Benzene usually randomly with toluene and the above-mentioned boiling range of small amount Interior more higher boiling aromatic compounds consists of the main aromatic compounds composition of preferred feedstock together.

Generally speaking, the raw material that is used for the inventive method comprises at least 15, often from 40, preferably extremely Few 50 quality % are to basically whole linear alkanes. For feed naphtha, linear alkanes Amount normally reaches 50, for example 50 to 90 quality % at least. Non-linear alkane in the described raw material The mass ratio of hydrocarbon and linear alkanes is often less than 1: 1, for example 0.1: 1 to 0.95: 1. Non-linear alkane Hydrocarbon comprises acyclic alkane and replacement or the unsubstituted cycloalkane of branching. Other component such as aromatics chemical combination Thing and olefin(e) compound also may reside in the above-mentioned raw materials.

Described raw material is delivered to one or more isomerization zone. In the present invention with aspect the n-hexane recycle, Usually raw material was mixed before entering isomerization zone with recycle, but the words that need can be single Solely introduce. In any situation, whole chargings of isomerization zone are called as in this article isomerization and advance Material. Can provide recycle with one or more strands of materials flows. Discuss such as the back, described recycle comprises Linear alkanes. The concentration of isomerization charging neutral line alkane not only depends on raw material neutral line alkane The concentration of hydrocarbon, and depend on the relative consumption of concentration in the recycle and recycle and raw material, its Can be in wide region. Usually, the isomerization charging have at least 30, for example 35-90, preferred 40-70 The linear alkanes concentration of quality %, and the mol ratio of non-linear alkane and linear alkanes is 0.2: 1-1.5: 1, be 0.4 sometimes: 1-1.2: 1.

In isomerization zone, but preferably in the presence of the hydrogen of limited positive number consumption, make the isomerization charging Stand to comprise the isomerisation conditions of isomerization catalyst existence, such as US 4,804,803 and 5,326,296 Described in, both incorporate by reference this paper into. It is reversible that the isomerization of alkane is considered to usually First order reaction. Thereby, to compare with the isomerization charging, the isomerization reaction effluent comprises big concentration Non-linear alkane and than the linear alkanes of small concentration. In a preferred embodiment of the invention, different The structure condition is enough to make in the isomerization charging at least 20, the normal paraffin hydrocarbons isomery of preferred 30-60 quality % Change. Usually, isomerisation conditions is for the C that exists in the isomerization charging₆Alkane realization at least 70, The balance of preferred at least 75, for example 75-97%. In many cases, isomerization reaction effluent tool Have at least 2: 1, preferred 2.5-4: 1 non-linear alkane and the mass ratio of linear alkanes.

Isomerization catalyst is also non-key for the wide aspect of the inventive method, any suitable isomerization Catalyst can be used. The isomerization catalyst that is fit to comprises that the use chloride is to keep looking for acid Acidic catalyst and the sulfated catalyst of property. Isomerization catalyst can be unbodied, for example Based on amorphous alumina, or zeolite. Zeolite catalyst still comprises amorphous binding agent usually. This catalyst can comprise Sulfated zirconia and platinum, such as US 5,036, and 035 and European application 0 666 Described in 109 A1, or in the platinum group metal on the aluminium oxide of chlorination, such as US 5,705,730 Hes 6,214, described in 764. Another suitable catalyst is at US 5,922, obtains describing in 639. US 6,818,589 disclosed catalyst comprise IVB (IUPAC 4) family metal oxide or hydroxide At least the of the wolframic acid carrier of (preferential oxidation zirconium or zirconium hydroxide), lanthanide series and/or yttrium component One component, and at least second component of platinum group metal component. These documents about carbon monoxide-olefin polymeric, This paper is all incorporated in the instruction of isomerization operating condition and technology into.

Contact in the isomerization zone can utilize catalyst in fixed bed system, moving bed system, fluidisation Realize in the bed system or with batch operation. Preferred fixed bed system. Can make reactant with up, The mode of descending or Radial Flow and the bench grafting of catalyst granules touch. Reactant is connecing with catalyst granules Can be in when tactile in liquid phase, liquid-vapour mixing phase or the gas phase, to mainly being liquid-phase operation application the present invention Obtain excellent result. Isomerization zone can be in single-reactor or is independent at two or more In the reactor, have adequate measures between these reactors to guarantee the entrance maintenance in each district Required isomerisation temperature. Preferred two or more reactors in turn are so that can be by single The control of individual temperature of reactor improves isomerization, and the part that can carry out catalyst is changed and do not had Need technology to stop.

Isomerisation conditions in the isomerization zone comprises and is generally 40-250 ℃ temperature of reactor. Usually excellent Select lower reaction temperature, to be conducive to the highest the putting down of high-octane highly branched isoparaffin concentration The weighing apparatus mixture, and make charging cracking to lighter hydrocarbon reach minimum. In the present invention preferred 100-200 ℃ temperature. The reactor operating pressure is generally 100kPa-10MPa (definitely), and is excellent Select 0.5-4MPa (definitely). Liquid hourly space velocity (LHSV) per hour be every volume of catalyst 0.2-25 volume can The charging of isomerization hydrocarbon, preferred 0.5-15hr^-1。

Hydrogen mixes or belongs to eventually this charging so that 0.01-20, preferred to be provided with the isomerization charging of isomerization zone 0.05-5 hydrogen and the mol ratio of hydrocarbon charging. Hydrogen can provide from the technology outside or pass through fully The hydrogen that is circulated to charging from the isomerization reactor effluent after separating replenishes. Light hydrocarbons and few Amount inert substance such as nitrogen and argon may be present in the hydrogen. Should be with water from the hydrogen by the outside supply of technology Remove in the gas, preferably remove by adsorption system as known in the art. In preferred embodiment In, the mol ratio of hydrogen and hydrocarbon is equal to or less than 0.05 in the reactor effluent, has generally avoided hydrogen Gas is circulated to the needs of charging from reactor effluent.

Particularly be used for making the isomerization reaction effluent in the isomerized situation at the catalyst through chlorination Contact to remove any chloride component with adsorbent, as at US 5,705, disclosed in 730.

Distillation separates with film

Make the isomerization reaction effluent experience one or more lock out operation, improve so that octane number to be provided Product fraction, and randomly remove other component is such as hydrogen, lower alkane and particularly with regard to warp The catalyst of chlorination is removed halogen compounds.

In the isomerization method that usually carries out, in liquid phase, carry out isomerization, and also isomerization is anti-Answer effluent to deliver to the product separation device, obtain therein containing the gaseous overhead of hydrogen and lower alkane Distillate. Can make this at least part of hydrogen be circulated to isomerization reactor, to provide at least part of The needed hydrogen of isomerization. Liquid tower bed material is delivered to distilling apparatus (taking off the isohexane tower), to carry For the cut that contains n-hexane than low boiler cut and higher that contains dimethylbutane. The most normally, Make take off that the isohexane tower is fit to be provided as the side line materials flow contain the n-hexane materials flow, and provide and contain normal heptane The tower bottoms stream. Taking off the isohexane tower can be packed tower or plate column, and usually at 50-500kPa Move under the top pressure of (gauge pressure) and 75-170 ℃ the bottom temp.

Come the composition than low boiler cut of autospasy isohexane tower to depend on any sepn process that the operation of this device and design and isomerization effluent are stood.For example, comprise light component such as C if deliver to the materials flow of taking off the isohexane tower ₁-C ₄Compound then can make and take off the isohexane tower and be fit to provide the overhead fraction that comprises these light component, and contain C ₅The C of compound and branching ₆The side stream of compound, particularly dimethylbutane.Usually should contain 20-60 quality % dimethylbutane than low boiler cut; 10-40 quality % Skellysolve A and 20-60 quality % iso-pentane and butane.According to the operation of taking off the isohexane tower, can also comprise a great deal of than low boiler cut, as the methylpentane of at least 10 quality %.Except than the lower boiling materials flow, take off the isohexane tower and can also be fit to provide C ₅The materials flow of enrichment.

The normal hexane cut that contains of described higher also comprises methylpentane and methylcyclopentane.As previously mentioned, method of the present invention makes takes off the isohexane tower and operates more economically, causes containing the dimethylbutane of bigger concentration in the normal hexane cut.The described cut that contains normal hexane often comprises 2-10 quality % dimethylbutane; 5-50 quality % Skellysolve A; 20-60 quality % methylpentane and 5-25 quality % methylcyclopentane.Usually, take off the isohexane tower and will be designed to provide the side line that comprises methylpentane, methylcyclopentane, normal hexane, dimethylbutane and hexanaphthene materials flow, and comprise hexanaphthene and C ₇The tower bottoms stream of+hydrocarbon.If contain the cut of normal hexane is the tower bottom distillate that takes off the isohexane tower, and then this cut also comprises these heavier hydrocarbon.

As mentioned above, the ability that reclaims dimethylbutane the normal hexane cut that contains from higher makes distillation to carry out with lower reflux ratio.Used reflux ratio depends on the character of tower charging and the design of tower, thereby can be a wide range of changes, and for example the quality based on reflux material and charging is 1.5: 1-2.5: 1.

Make to small part, preferred at least 50, more preferably at least 80 quality % to whole basically normal hexane cut that contains that comes autospasy isohexane tower and contact with the retentate side of selective membrane, thereby the retention fraction of the isomerization reaction effluent of total linear paraffinic hydrocarbons concentration reduction is provided, and the penetrant fraction of total linear paraffinic hydrocarbons concentration raising is provided in the permeate side of this film.Described penetrant fraction comprises the normal hexane of at least 75 quality %, the normal hexane in preferred at least 75 quality % and the cut that described film contacts.Described retention preferably comprises the methylcyclopentane that at least 50, more preferably at least 80 quality % comprise to whole and the cut that described film contacts basically.Of the present invention preferred aspect, described film makes at least 25, the methylpentane that comprises in the normal hexane cut that contains that contacts with this film of for example 30-90 quality % sees through.

In order under suitable infiltration rate, to realize required separation, keep the pressure drop of these film both sides.Described film can be any adequate types that comprises diffusion barrier and sieve membrane, can be made of inorganic, organic or matrix material.For diffusion barrier, motivating force is the partial pressure difference between retentate side and the permeate side.In sieve membrane, absolute pressure drop becomes the important component of the motivating force that is independent of dividing potential drop or concentration.Preferred film is C ₆Permeate flow index is at least 0.01 and C ₆Permeate flow is than the sieve membrane that is at least 1.25: 1.This is discussed below sieve membrane in more detail.

In membrane sepn, pressure drop is 0.1-10, preferred 0.2-2MPa often.In fact, contain the normal hexane cut and contact with the retentate side of described film and do not have additional compression, thereby make cost of capital and running cost minimum.The temperature section of membrane sepn depends on the character of this film and the temperature of this cut.Thereby for the film that contains polymkeric substance, temperature should be hanged down is enough to make film strength can not be subjected to unsuitable disadvantageous effect.In most of the cases, separation temperature is the temperature of taking off isohexane tower cut.Often this temperature is 25 ℃-150 ℃.Thereby the condition of membrane sepn can provide liquid phase or gas phase or mixed phase in this film retentate side.No matter the fluidic thing of retentate side phase how, penetrant can be a gas.If the fluid of this film retentate side is a liquid phase, penetrant can be liquid phase, gas phase or mixed phase.

Any suitable selectively permeable membrane can be used for method and apparatus of the present invention.Preferred film is a sieve membrane.The film that is used for the inventive method is characterised in that to have high-throughput, promptly has at least 0.01 C ₆Permeate flow index.Described film can be any suitable form, and as tubular fibre, sheet material etc., it can be assemblied in the separating unit, as bunchy tubular fibre or flat board or screw winding sheet like membrane (spiral wound sheet membranes).The physical Design of film makes the pressure drop of these film both sides can be enough to provide the flux of expectation in the time of should be in being assembled to separating unit.For hollow-fibre membrane, high-tension side (retentate side) common outside at this tubular fibre.The moving phase of penetrant can be also stream, adverse current or cross-flow for the fluid flow of this film retentate side.

Enough film surface-area are provided, make under steady state conditions at least 75, contained normal hexane is included in the described penetrant in the cut that comes autospasy isohexane tower of preferred at least 80 and more preferably at least 90 quality %.The concentration of normal hexane depends on the selection rate of film.Although described film can have highly selective and the penetrant that comprises 99 quality % or more normal hexanes is provided, favourable embodiment of the present invention can realize under the penetrant than low-purity.The normal hexane concentration of total penetrant is less than 90 quality % in these embodiments, for example 25-90, as 40-80 quality %.Remaining effluent is methylpentane and some methylcyclopentanes and the dimethylbutane that pass described film normally.

Preferred high-throughput sieve membrane sees through the part branched paraffin.Relative infiltration rate depends on the molecular configuration of these paraffinic hydrocarbonss.Compare with pentamethylene with dimethylbutane, methylpentane is easier to pass described film.

The penetrant of preferred near small part is circulated to isomerization steps.This penetrant is included in the linear alkanes that will stand isomerisation conditions in the isomerization steps process.

Sieve membrane

Preferred sieve membrane can be all kinds, molecular sieve for example, the pottery, metal, polymkeric substance or the carbon film that contain the hole, or composite membrane, it has highly porous polymkeric substance, metal, molecular sieve, pottery or carbon support and micro porous thin screening layer or barrier (molecular sieve), as zeolite, polymkeric substance, metal, pottery or carbon.

Film can be continuous or discrete.Discontinuous film comprises the aggregate of the micropore barrier that particle size is little, and continuous film comprises successive micropore barrier layer.Film can be formed by single-material, and perhaps they can be the mixtures that comprises micropore barrier and carrier and optional other structure.When preparing thin continuous barrier layer, along with the stratified thickness of sieve reduces, the difficulty that obtains the zero defect layer increases.Because method of the present invention does not need highly selective, therefore described film can comprise less defective.Usually continuous film is made by deposition on meso/macroporous structure or growth successive micropore barrier thin layer.The discontinuous set zoarium of the micropore barrier of nano-scale makes it possible to obtain very little infiltration thickness, but has the possibility of bypass.Discontinuous film adopts the meso/macroporous structure that combines with the micropore barrier.

The example of zeolite barrier comprises small pore molecular sieve, as SAPO-34, DDR, AlPO-14, AlPO-17, AlPO-18, AlPO-34, SSZ-62, SSZ-13, zeolite 3A, zeolite 4A, zeolite 5A, zeolite KFI, H-ZK-5, LTA, UZM-9, UZM-13, ERS-12, CDS-1, phillipsite, MCM-65 and MCM-47; Medium pore molecular sieve is as hydrophobic silicalite (silicalite), SAPO-31, MFI, BEA and MEL; Large pore molecular sieve is as FAU, OFF, NaX, NaY, CaY, 13X and zeolite L; And mesoporous molecular sieve, as MCM-41 and SBA-15.The molecular sieve of many types can get with colloidal state (nano-sized particles) form, as A, X, L, OFF, MFI and SAPO-34.Zeolite can through or can be without metal exchange.

The screening materials of other type comprises the carbon sieve; Polymkeric substance, as PIM (intrinsic micro porous polymkeric substance) as following disclosed: McKeown etc., Chem.Commun., 2780 (2002); McKeown etc., Chem.Eur.J., 11:2610 (2005); Budd etc., J.Mater.Chem., 13:2721 (2003); Budd etc., Adv.Mater., 16:456 (2004) and Budd etc., Chem.Commun., 230 (2004); Wherein introduce the polymkeric substance of porosity as poly-(oxyalkylene), Polyvinylpyrolidone (PVP) by pore former; Ring-type organic substrate such as cyclodextrin, calixarene, crown ether and near-spherical pothole compound (spherands); Micropore metal-organic backbone such as MOF-5 (or IRMOF-1); Micro porous glass, pottery and shape have wherein been introduced.

In composite membrane, use meso/macroporous structure.This meso/macroporous structure plays one or more effects according to film type.It can be the carrier of membrane complex, and it can be the integral part that forms the micropore barrier, it can be micropore barrier place thereon or structure wherein.This meso/macroporous structure can be continuous or discrete, thereby this mesopore/macroporosity can be by the passage of described meso/macroporous structure material or form between the particle that forms this meso/macroporous structure.The AccuSep of the latter's example for getting from Pall Corp. ^TMThe inorganic filter film, it has the zirconia layer on Lacunaris metal carrier, and wherein zirconium white is the spherocrystal form.

It is 2-500, preferred 10-250, the more preferably passage or the hole of 20-200 nanometer that meso/macroporous structure preferably defines diameter, and has high-throughput.In a more preferred embodiment, the C of meso/macroporous structure ₆Permeate flow index is at least 1, and most preferably at least 10, be at least 1000 sometimes.This meso/macroporous structure can be an isotropy or anisotropic.Meso/macroporous structure can be straight relatively or tortuous.

Meso/macroporous structure can be by inorganic, organic or blended is inorganic and organic materials constitutes.The type of separation condition and formed meso/macroporous structure is depended in the selection of material.The material of meso/macroporous structure can be identical or different with the material of molecular sieve.The example that vesicular structure is formed comprises metal, aluminum oxide such as Alpha-alumina, gama-alumina and transition alumina, molecular sieve, pottery, glass, polymkeric substance and carbon.In preferred embodiments, the defective in the repairing base material before barrier or barrier precursor are provided.In another embodiment, base material can be handled with the part plugging hole with silicon sol, and promotes the deposition of barrier or barrier precursor.This silicon oxide particle still provides enough space to allow high flow (flux rate) between their gap.Another technology is with allowing that high-throughput still stops up silicon rubber or other polymer-coated carrier of defective in carrier or the barrier.

If meso/macroporous structure does not so work, film can comprise the porous support that is used for meso/macroporous structure.Usually based on intensity, the tolerance and the porosity of expection separation condition are selected this porous support.

The AccuSep that can get from Pall Corp. ^TMThe meso/macroporous structure particularly advantageous of inorganic filter film and similar type because this meso/macroporous structure can be thinner, avoids growing excessively thick molecular sieve thus.In addition, zirconium white makes it become the preferred meso/macroporous structure of these type sieve membranes for precursor solution that forms zeolite and the synthetic relative inertia that is with calcination condition.

By at least a high-throughput of realizing in the following technology: at first, use than n-paraffin by required bigger hole; Secondly, use as thin as a wafer contain the hole layer.In the micropore barrier, use micropore big, that selectivity is lower to realize to realize enough separation under the high-throughout situation.The hole of this class film often has greater than the average pore diameter of 5.0  (length and width average), 5.0 to 7.0 or 8  for example.Preferably, this structure has less than 1.25: 1, for example 1.2: 1-1: 1 long-width ratio (length is than width).For the film that contains molecular sieve, exemplary structure is USY, ZSM-12, SSZ-35, SSZ-44, VPI-8 and cancrinite.In some cases, the permeable molecule in the micropore can help to improve selectivity.For example, the positive structure hydrocarbon in the hole can make speed that branched hydrocarbon can enter this hole and another positive structure hydrocarbon phase than and reduce.

In continuous or discontinuous film, use extremely thin micropore barrier also can realize high-throughput.Need, this micropore barrier can be selected from the screening structure with micropore, and it is impermeable basically for the structure division of attempting to be retained in retentate side.Generally speaking, the hole of this class film has the average pore diameter of 5.5 , for example 4.5-5.4  at the most.The long-width ratio in the hole of these films can change by wide region, is generally 1.5: 1-1: 1.For the film that contains molecular sieve, exemplary structure is ZSM-5, hydrophobic silicalite, ALPO-11, ALPO-31, ferrierite, ZSM-11, ZSM-57, ZSM-23, MCM-22, NU-87, UZM-9 and CaA.

The film that comprises micropore barrier discontinuous set zoarium is characterised in that this barrier has the principal dimension less than 100 nanometers, and this micropore barrier combines with the meso/macroporous structure that defines fluid flow bore, wherein the barrier location made and hinders the hole that fluid flows through this meso/macroporous structure.When no matter whether the molecular sieve barrier be positioned on this structure with the meso/macroporous structure bonding or wherein the time, it promptly " combines " with this structure.Therefore, the sieve particle of nano-scale or island (island) is as the barrier of described film.Discontinuous micropore barrier location is made that hindering fluid flows through the fluid flowing passage that is defined by meso/macroporous structure.Barrier can stop up at least in part meso/macroporous structure fluid flowing passage opening and/or in this fluid flowing passage.Owing to form the particle of micropore barrier discontinuous set zoarium or the small size on island, so no matter discontinuity how, all can realize certain separation selectivity.

In the component of selecting sieve membrane, can take into account the size of sieve particle and the size and the configuration of the mesopore/macropore in configuration and the meso/macroporous structure usually.Under the situation of more spherical sieve particle such as hydrophobic silicalite, the preferred meso/macroporous structure of selecting to have near the hole of identical effective diameter.By this way, if sieve particle is arranged in the hole of this meso/macroporous structure or part is arranged in wherein, it can provide minimum bypass void space.Because they can be overlapping and void space is few or do not have void space, therefore there are greater flexibility in small pieces and erose sieve particle.In some cases, the combination of molecular sieve configurations may be an ideal.For example, spherical molecular sieve can be introduced in the hole of meso/macroporous structure, be introduced less more tabular sieve particle subsequently.This complementary action is that ball serves as the carrier of plate-like particles and plate-like particles is overlapping to reduce bypass.Though molecular sieve may be different compositions, thereby has different pore sizes and configuration, benefit is to have improved separation, and does not have unsuitable seepage loss.

Under the situation of using zeolite molecular sieve, obtaining little particle is important for obtain high-throughput in discontinuous micropore barrier.For many zeolites, principal dimension can be used less than the seed grain of 100 nanometers.Most of molecular sieves utilize organic formwork to make, and this organic formwork must be removed to provide near cage.Usually finishing this through calcining removes.Discuss as the back, can when the molecular sieve that contains template is arranged in macropore, calcine, so that avoid inappropriate gathering by the number of restriction adjacent particles simply.Another technology of zeolite granular accumulative is for example used aminoalkyl group trialkoxy silane, aminoalkyl group alkyl-dialkoxysilanes or aminoalkyl group dialkyl group organoalkoxysilane for making zeolite surface silanization (silate) during avoiding calcining.Required silanization amount depends on the size and the composition thereof of zeolite and is used for the incinerating condition.Usually, every gram zeolite uses the silane of 0.1-10 mmole.

For so that on mesopore/macropore carrier or sieve particle wherein is provided, there are multiple technologies in the mode that small part is stopped up mesopore in the carrier or macropore.Used particular technology will depend in the size of the mesopore/macropore in the size of sieve particle and configuration, the meso/macroporous structure and configuration and this meso/macroporous structure or the molecular sieve of expectation on it is arranged.

Particularly molecular sieve is arranged on the meso/macroporous structure surface stopping up to the situation of the opening in small part hole, can be with molecular sieve solution or wetting this meso/macroporous structure of suspension of nano-scale.The concentration of molecular sieve should be enough low in the suspension, makes that the molecular sieve layer of dry back gained can be not blocked up.Advantageously, this meso/macroporous structure both sides keep slight at least pressure drop during being coated with, thereby make and exist motivating force that molecular sieve is guided in the meso/macroporous structure in any not blocked hole.Common described suspension is waterborne suspension, yet can advantageously use the suspension in alcohols and other relative inertness liquid, and concentration is 2-30, for example 5-20 quality %.Utilizing under the situation of pressure reduction, this pressure reduction is generally 10-200kPa.Can use one or more molecular sieve coatings, carry out drying between the preferred coatings.Dry carried out 1-50 hour under in the temperature that raises usually as 30 ℃-150 ℃.Can use vacuum to help drying., for example can help in some cases molecular sieve is fixed on the meso/macroporous structure when the molecular sieve at zeolite at 450 ℃-600 ℃ temperature lower calcination.Calcining can also be played and make sieve particle assemble the effect that reduces space and void size thus.Certainly, calcining is for wide aspect of the present invention and inessential, for example has only in template and stays under the situation in the micropore just needs.

Be positioned at the discontinuous set zoarium of nano-sized molecular sieve under the situation of outside, hole of meso/macroporous structure, it may be desired making and be bonded to this body structure surface to the small part particle.This can finish with several different methods.For example, this body structure surface can by hydroxyl or that zeolite molecular sieve is reactive other structure division be functionalized.For polymeric molecular sieves, can use with this polymkeric substance on functional moiety reaction, make functionalisation of surfaces as the structure division of addition or condensation.For other application, these technology are as known in the art.

Under the sieve particle of the near small part of expectation is combined in situation in the hole of meso/macroporous structure, can use similar technology of preparing.Sieve particle should have suitable size to enter this mesopore/macropore.Can utilize pressure reduction that the barrier particle is introduced in the hole, perhaps can utilize ultrasonication to help the barrier particle and enter in the hole of mesopore/macropore carrier.The degree of depth of sieve particle in the hole of meso/macroporous structure should be not too large so that immoderation ground reduce infiltration.Often remove the molecular sieve of any surface deposition by for example washing.

Need, thereby can make zeolite molecular sieve growth in situ in the hole of meso/macroporous structure that discontinuous film is provided.Should synthetic can between other structure such as meso/macroporous structure or other particle, provide discrete particle or island.

Use the example of other granules preparation zeolite molecular sieve discontinuous film to be included in the meso/macroporous structure or silicon oxide is provided on it, it can have the particle size of 5-20 nanometer.Silicon oxide is owing to lip-deep activity hydroxy serves as the nucleation site that zeolite forms precursor solution, and zeolite layer can be grown on the silicon oxide particle and between them.

Material except that silicon oxide particle can be used as the nucleation site, comprises the seed crystal of other molecular sieve or identical zeolite.The functionalisation of surfaces that can make meso/macroporous structure is to provide the selectivity position of zeolite growth.Some zeolites have spontaneous nucleation character, thereby can use under the situation that does not have the nucleation site.The example of these zeolites is FAU and MFI.In these cases, may be desirably in before the precursor solution contact meso/macroporous structure time that makes precursor solution under the zeolite formation condition, keep enough zeolite growths to begin.

For example, a kind of method of formation barrier layer is that body fluid before the zeolite molecular sieve is placed on the meso/macroporous structure.Make the crystallization under the hydrothermal crystallization condition of this precursor, wash this film then, and heating is to remove residual organic matter.This molecular screen material is mainly stayed in the hole of porous substrate and is stopped up this hole.

Molecular sieve can have any suitable element combinations so that required pore structure to be provided.With aluminium, silicon, boron, gallium, tin, titanium, germanium, phosphorus and oxygen as the structural unit of molecular sieve, described molecular sieve such as silica-alumina molecular sieve, comprise zeolite; Hydrophobic silicalite; AlPO; SAPO and boron-silicate.Precursor comprises that usually as oxide compound or phosphatic above-mentioned element and water and organic structure agent, described organic structure agent is polar organic compound normally, as TPAOH.Can also use other auxiliary agent, as amine, ethers and alcohols.The mass ratio of polar organic compound and structural unit material generally is 0.1-0.5, and depends on used specific structure unit.In order to prepare the thin molecular sieve layer in film, general preferred this precursor solution is rich in water.For example, for the silica-alumina molecular sieve, the mol ratio of water and silicon oxide should be at least 20: 1, and for aluminophosphate molecular sieve, mol ratio should be every moles, of aluminum per mole of titanium metal at least 20 mole of water.

Crystallization condition is often 100-1000, often under the 200-500kPa absolute pressure 80 ℃-250 ℃.Crystallization time is limited, makes can not form blocked up molecular sieve layer.Usually, crystallization time less than 50, for example 10-40 hour.Preferred this time is enough to form crystal, forms 200 nanometers, required time of for example 5-50 nano molecular sieve layer but be shorter than.Crystallization can be finished in autoclave.In some cases, microwave heating is finished crystallization in the short period of time.Wash film then with water, then calcine to remove any organism down at 350-550 ℃.

For some zeolite molecular sieve materials, preparation is less than the particle difficulty of 100 nanometers especially.And even use seed crystal, particle size may be greater than desired.Another embodiment for preparing discontinuous barrier film for principal dimension less than the open base area between the particle (substrate particles) of 100 nanometers in synthetic zeolite.Therefore, the principal dimension of micropore barrier can be less than 100 nanometers.Substrate particles is served as the nucleation site that zeolite forms, thereby is selected from and has the material that makes zeolite growth nucleation ability.The example of this class material is that silicon oxide, particularly principal dimension are the silicon oxide of 5-50 nanometer and principal dimension other zeolite less than 100 nanometers.Thermal silica (fumed silica) is used as substrate particles for preparation AlPO micropore barrier particularly suitable.

Zeolite the growth on the substrate particles can occur in this substrate particles is used to form membrane complex before or after.

Advantageously, when the synthetic liquid of guiding passed through mixture, zeolite was grown on substrate particles.This technology helps to guarantee that this growth is not to carry out as the layer on the particle top, but carries out in gap between particles.Pressure drop is carried out along with zeolite growth and is increased, and pressure drop can be as the indication that forms suitable zeolite.

Can in meso/macroporous structure, sieve by synthetic polymer molecule.A kind of method of synthetic little polymeric molecular sieves is: make nano particle and/or meso/macroporous structure functionalized with the group that can be for example reacts by condensation or addition reaction and oligopolymer.For example, this functional group can provide hydroxyl, amino, acid anhydrides, dianhydride, aldehyde, amido acid (amic acid), carboxyl, acid amides, nitrile or the ethylene linkage structure division that carries out addition or condensation reaction with the reactive structure division of oligopolymer.The oligopolymer that is fit to can have 30,000 to 500,000 or bigger molecular weight, and can be following reactive oligomers: polysulfones; Comprise poly-(vinylbenzene) that contains cinnamic multipolymer; Cellulose polymer compound and multipolymer; Polymeric amide; Polyimide; Polyethers; Urethane; Polyester; Vinylformic acid and methacrylic polymer and multipolymer; Polysulphide; Polyolefine, particularly vinyl polymer and multipolymer; Polyene propyl group material; Poly-(benzoglyoxaline); Poly-phosphine piperazine; Polyhydrazide; Polycarbodiides or the like.

No matter be inorganic or the organic molecule sieve, its original position is synthetic can be under the condition that is fit to.When being included in reactant solution such as precursor solution or oligomer solution guiding by meso/macroporous structure, preferred technology synthesizes.This technology provides reactant solution is caused the benefit that does not have in the blocked space, and the degree of restriction molecule sieve growth, in case because molecular sieve with mesopore or big hole plug, does not just have fresh reactant can enter this reaction site.

Molecular sieve on the polymer support film or polymer support itself also can be in vacuum oven pyrolysis with the preparation carbon film.For this film that contains molecular sieve, the pore structure of carbon support preferably has enough diameters so that the resistance minimum of fluid flow, and this molecular sieve structure can be carried out separation simultaneously.Pyrolysis temperature depends on the character of polymer support, and below the temperature of inappropriate reduction porosity.The example of polymer support comprises polyimide, polyacrylonitrile, polycarbonate, polyetherketone, polyethersulfone and polysulfones, and before pyrolysis, carrier has the hole or the opening of 2-100, preferred 20-50 nanometer.

Can prepare continuous film by any suitable technology.Usually, the thickness of micropore barrier deposit on meso/macroporous structure with the micropore barrier or time length of growing relevant.The micropore barrier can (effectively bore dia be 100-10 by reducing ultra-filtration membrane (effectively bore dia is the 1-100 nanometer) or microfiltration membrane, 000 nanometer) hole size forms, and for example inner or preferred organic or inorganic coating to the close access portal of small part reduces by channel surface.Sedimentary material is used for hole on the carrier or opening part are decreased to the required screening of permission and do not have the inappropriate size that reduces the diameter of carrier residue pore structure.But the example of the sedimentary material of gas phase comprises silane, to xylylene (paraxylylene), alkylene imine and oxyalkylene.Another technology that reduces hole dimension is a deposit coke layer on meso/macroporous structure.For example, but the gas of carbonization as methane, ethane, ethene or acetylene can with as described in structure contact being enough to cause under the elevated temperature of coking.Preferred porous support is that hole size is the ultra-filtration membrane of 1-80, preferred 2-50 nanometer.

For the zeolite continuous film, a kind of technology of preparing comprises that the surface that makes meso/macroporous structure contacts with the molecular sieve precursor, and makes the molecular sieve growth be enough to obtain the time of required film thickness.Aforesaid method can be used for synthesis of molecular sieve.In some cases, for example may expect that mesopore/macropore with paraffin blockage plug carrier is in case defervescence stone hypertrophy in those holes.Can remove dewax subsequently.

Multiple technologies can be used for strengthening the selectivity of high flux membrane.Exist many technology to eliminate defective in continuous film or the discontinuous film.Because described film does not need to show high C for many application ₆The permeate flow ratio is so any technology that increases the mobile resistance by described defective all can play the effect that improves film properties.For example, no matter how this film is made, the silicon sol seal coat can be used for stopping up space opening or the remaining macropore of carrier between the molecular sieve crystal.

Another technology of stopping up macropore is that the side at barrier layer provides the not big reactive molecule of porous barrier micropore, and provides linking agent at opposite side.Bigger defective and in a way smaller defect become and be full of this big reactive molecule, and by crosslinked fixing.Can remove unreacted macromolecular components and unreacted linking agent then.Described macromole can be oligopolymer or big molecule.

For discontinuous film, can be between the particle of micropore barrier or island and between micropore barrier and the meso/macroporous structure to the small part space, provide solid.

Improving optionally a kind of current techique of sieve membrane is that adjacent sieve particle is assembled to reduce or to eliminate between the particle basically and the space between the wall of the pore structure in particle and the meso/macroporous structure.Because particle is a nano-scale, and the number of adjacent particle can be less relatively, still keeps the permeate flow speed of target so can assemble.For thermoplastic polymeric molecular sieves, to such an extent as to can assemble take place but can too highly not lose its microvoid structure or its provides the temperature of the ability of the mesopore of required obstruction meso/macroporous structure or macropore to assemble by being heated to.Assemble and also can finish by the calcined zeolite molecular sieve.Calcining often makes little zeolite granular assemble, and has not particularly both had silanization also not handle the particle of assembling tendency to reduce.Calcining temperature and time length are depended on the character of zeolite molecular sieve.Usually adopt 450 ℃-650 ℃ temperature to carry out 2-20 hour.

With regard to those particles in the lip-deep sieve particle of meso/macroporous structure and this structure hole, can use aggregation technique.Most preferably, when sieve particle is positioned at the mesopore of meso/macroporous structure or macropore, adopt and assemble, so that the principal dimension of aggregate is less than 200, preferably less than 100 nanometers.Can there be pressure reduction in gathering or have in the film both sides to be carried out under the pressure reduction.Preferably utilize pressure reduction to help to reduce the space that fluid can be crossed molecular sieve through its bypass.

Defining another kind of current techique under the situation of space at the discontinuous set zoarium of barrier is to be stopped up at least in part to the small part space by wherein solid material.Preferably, this solid material is polymkeric substance or inorganic materials.Solid material can be stayed in the space simply, and perhaps it can adhere to or bonding with molecular sieve or meso/macroporous structure.Solid material can be particle or oligopolymer, and it can be pre-formed introduces in the space then, perhaps can original position form.

On the one hand, solid material provides " mortar (mortar) " for micropore barrier particle.Mortar normally can stand the suitable polymeric material of separation condition.Typical polymers comprises polysulfones; Comprise poly-(vinylbenzene) that contains cinnamic multipolymer; Cellulose polymer compound and multipolymer; Polymeric amide; Polyimide; Polyethers; Urethane; Polyester; Vinylformic acid and methacrylic polymer and multipolymer; Polysulphide; Polyolefine, particularly vinyl polymer and multipolymer; Polyene propyl group material; Poly-(benzoglyoxaline); Poly-phosphine piperazine; Polyhydrazide; Polycarbodiides or the like.Preferred polymkeric substance is to have those of porosity, as PIM (referring to WO 2005/012397) and the polymkeric substance of introducing porosity by pore former.It can be 0.3 or the hole of bigger, preferred at least 1 nanometer that these polymkeric substance have principal dimension, therefore allows direction of flow barrier particle and flows away from the barrier particle.

Will not be encapsulated in the mortar by all particles.The mean thickness of screed preferably is no more than the particulate principal dimension often less than 100 nanometers.If use too many mortar, may cause the blended membrane structure, and make the inappropriate deterioration of flux.Therefore, the mass ratio of barrier particle and mortar often 1: 2-100: 1, preferred 3: 1-30: 1.

Mortar and particle for example can be mixed in slurry, arrange in conjunction with microvoid structure then, perhaps can behind particle deposition, provide.Polymkeric substance can contain the original position formation of barrier particulate zone.The barrier particle can be inertia to polymerization, perhaps can have the avtive spot of fixed polymer.For example, can be with combining with polymkeric substance or the bonded reactive group makes particle functionalized with the polymerization (for example by above-mentioned condensation or addition mechanism) of monomer experience.

One big misgivings are that mortar stops up the micropore of molecular sieve.Under the situation of highly porous polymkeric substance such as PIM, can alleviate the influence of any obstruction.Be used for the amount of polymkeric substance of mortar and molecular weight thereof and configuration and often will make that existing polymkeric substance is not enough to seal all sieve particles.The mass ratio of polymkeric substance and molecular sieve often is 0.01: 1-0.3: 1.The weight-average molecular weight of polymkeric substance is 20 sometimes, 000-500, and 000, preferred 30,000-300,000.

Mortar can be the material except that polymkeric substance.For example, be under the situation of zeolite at molecular sieve, four-oxyl silicon can react with zeolite, and can form silicon oxide skeleton or agglomerate between sieve particle by hydrolysis.Usually use the four rare-oxyl silicon aqueous solution to guarantee distribution, for example contain 0.5-25 quality % four-oxyl silicon.Also can be used as the crosslink sites of organic polymer with the silicon functionalized zeolite of four-oxyls, particularly contain and to form the functional group of covalent linkage such as those polymkeric substance of hydroxyl, amino, acid anhydrides, dianhydride, aldehyde or amic acid group with the organosilicon hydrocarbon oxide.In addition, can identical or different zeolite be grown between zeolite granular and zeolite granular and meso/macroporous structure with above-described technology.

The another kind of method that reduces bypass is to contain the particle that uses two or more sizes in the barrier layer in formation.For example, be the ball of 60 nanometers if micropore barrier particle generally is the nominal principal dimension, then the zone between the particle can quite greatly and can provide bypass.Compatible particle can hinder fluid flow on the adding configuration in these zones, thereby causes more most fluid to be directed to the barrier particle with selective separation.Barrier particulate configuration depends on used barrier particulate type.Principal dimension has predetermined configuration less than the micro-pore zeolite sieve particle of 100 nanometers equally owing to its crystalline structure.Some zeolites often have the configuration of small pieces type, and other zeolite such as AlPO-14 have club shaped structure.Similarly, polymkeric substance, pottery, glass and carbon molecular sieve particles can have the configuration that is not easy to change.Therefore, the configuration of open base area can change by wide region between the particle.

Sometimes, select particle compatible on the configuration to realize stopping up to small part of described zone.Thereby for spherical barrier particle, compatible particle may be desired on the bar-shaped or much smaller configuration.Intended size and operational condition, compatible particle can have any suitable composition on the configuration.Particle can be polymkeric substance, comprise oligopolymer; Carbon; And inorganics such as thermal silica, zeolite, aluminum oxide etc.

Accompanying drawing describes in detail

With reference to Fig. 1, the raw material that will contain linear alkanes is delivered to isomerization unit through pipeline 102.Provide hydrogen through pipeline 104.Isomerization reactor 106 is delivered in the materials flow of this merging.Effluent from isomerization reactor 106 is directed at stabilizer tower 110 through pipeline 108.In stabilizer tower 110, light component shifts out through pipeline 112 as overhead product.This light component can be used to comprise any suitable purpose of fuel value.Deliver to by pipeline 114 from the tower bottoms stream of stabilizer tower 110 and to take off isohexane tower 116.Provide overhead product from taking off isohexane tower 116 through pipeline 118.Come the tower bottoms stream of autospasy isohexane tower 116 to shift out through pipeline 120.Come the side line materials flow that contains normal hexane of autospasy isohexane tower 116 to deliver to the retentate side of membrane separation apparatus 124 through pipeline 122.Shift out the less materials flow of linear alkanes concentration from separator 124 through pipeline 128.This materials flow comprises the methylcyclopentane that concentration improves.As shown in the figure, the overhead product in pipeline 128 guiding retention fractions and the pipeline 118 merges.Penetrant level lease making pipeline 126 is circulated to isomerization reactor 106.

Claims

1. thereby the isomerization raw material that comprises the paraffinic hydrocarbons with 5 and 6 carbon atoms provides the method for the isomerization product that comprises the isomerization paraffinic hydrocarbons, and wherein the raw material of at least 15 quality % is a linear alkanes, and described method comprises:

But contain linear alkanes concentration less than the isomerization effluent in the described raw material thereby a. under comprising the isomerisation conditions that isomerization catalyst exists, the raw material isomerization provided,

B. be distilled to the described isomerization effluent of small part, with provide contain dimethylbutane and more light paraffins than low boiler cut, and the higher that comprises normal hexane, methylpentane, dimethylbutane and methylcyclopentane contains the normal hexane cut,

C. make to the normal hexane cut that contains of small part and under the condition that comprises enough film surface-area and described both sides differential pressure of membrane, contact with the retentate side of selectively permeable membrane from step b, thereby the retention fraction of sideing stream that provides methylcyclopentane and dimethylbutane concentration to improve, and provide the penetrant fraction of normal hexane and the raising of methylpentane concentration in the permeate side of described film, described penetrant fraction comprise at least 75 quality % contact with described film contain normal hexane contained in the normal hexane cut and

D. shift out described retention fraction from step c.

2. the process of claim 1 wherein that the penetrant level of near small part step c is distributed to step a.

3. the method for claim 2, wherein the materials flow that comprises normal hexane of step b is the side line materials flow, and the distillation of step b provides and comprises C ₇The tower bottoms stream of hydrocarbon.

4. the method for claim 3, the concentration of normal hexane is less than 90 quality % in the wherein said penetrant fraction.

5. the method for claim 4, the methylpentane that contains at least 30 quality % in the normal hexane cut that wherein contacts described sieve membrane retentate side is delivered to the permeate side of described film, and the dimethylbutane that contains at least 70 quality % in the normal hexane cut that contacts described sieve membrane retentate side is retained in the retentate side of described film.

6. the method for claim 5, the wherein said normal hexane cut that contains comprises methylcyclopentane, and methylcyclopentane is included in the described retention fraction.

7. the method for claim 5, the wherein said dimethylbutane that contains in the described isomerization effluent that the normal hexane cut comprises 5-30 quality %.

8. the process of claim 1 wherein that described film is C ₆Permeate flow index is at least 0.01 and C ₆Permeate flow is than the sieve membrane that is at least 1.25: 1.

9. the method for claim 8, wherein said sieve membrane has the average pore diameter of 5.0-7.0 .

10. the method for claim 8, wherein said sieve membrane has the average pore diameter of 4.5-5.4 .

11. the method for claim 8, wherein said sieve membrane comprises ZSM-5 or hydrophobic silicalite.

12. the process of claim 1 wherein the described contained dimethylbutane in the described isomerization effluent that the normal hexane cut comprises at least 2 quality % that contains.

13. the process of claim 1 wherein and describedly comprise iso-pentane than low boiler cut.

14. the method for claim 12, wherein said is overhead fraction than low boiler cut.

15. one kind be used to comprise have 5 and 6 paraffinic hydrocarbonss between the carbon atom the raw material isomerization so that the device of gasoline fraction to be provided, it comprises: