FR2738244A1 - Hydro-isomerising straight and/or slightly branched long chain hydrocarbon(s) - Google Patents

Abstract

The selective hydro-isomerisation process for cpds. having at least one alkane chain contg. more than 10 C, comprises contacting with a catalyst comprising at least one hydro-dehydrogenating element and a molecular sieve. The latter component has a porous lattice, mono- or bi-dimensional, in which the accessible pore openings are 10 O atoms in width, and the bridge-width between the pores is less than 0.70 mm. This catalyst, when submitted to the standard n-heptadecane isomerisation test, gives (for a 95% conversion) a selectivity in isomerised prods. of at least 70%.

Description

The present invention relates to a process for the selective hydroisomerization of paraffins, linear and / or slightly branched, long (more than 10 carbon atoms), in particular for converting, in good yield, fillers having high pour points into at least one cup having a low pour point and a high viscosity index.

Prior art
High quality lubricants are of paramount importance for the operation of modern machines, automobiles, and trucks. However, the amount of paraffins directly from petroleum, untreated, and having the proper properties to constitute good lubricants is very small compared to the increasing demand in this sector.

The treatment of heavy petroleum fractions with high levels of linear or weakly branched paraffins is necessary in order to obtain base oils of good quality and with the best possible yields, by a dewaxing operation which aims to eliminate linear or very weak paraffins. little connected, charges that will then be used as base oils or as kerosene or jet fuel.

Indeed, high molecular weight paraffins which are linear or very weakly branched and which are present in oils or in kerosene or jet fuel lead to high pour points and thus to freezing phenomena for low temperature applications. . In order to decrease the pour point values, these linear paraffins which are not or very slightly connected must be completely or partially eliminated.

This dewaxing operation can be carried out by extraction with solvents such as propane or methyl ethyl ketone, which is called propane or methyl ethyl ketone (MEK) dewaxing.

However, these techniques are expensive, time consuming and not always easy to implement.

Catalytic dewaxing thus denominated as opposed to solvent dewaxing is more economical and makes it possible to obtain products having the desired physicochemical properties.

This is achieved by selectively cracking the longer linear paraffinic chains which leads to the formation of lower molecular weight compounds, a portion of which can be removed by distillation.

Given their selectivity of form zeolites are among the most used dewaxing catalysts. The idea that prevails in their use is that there are zeolitic structures whose pore openings are such that they allow the entry into their microporosity linear paraffins long or very little branched but excluding branched paraffins, naphthenes and aromatics. This phenomenon thus leads to selective cracking of linear or very poorly branched paraffins.

Zeolite catalysts having intermediate pore sizes such as ZSM-5, ZSM-11, ZSM-12, ZSM-22,
ZSM-23, ZSM-35 and ZSM-38 have been described for use in catalytic cracking dewaxing processes.

The processes using these zeolites allow the dewaxing by cracking of feeds containing amounts of linear or very poorly branched paraffins of less than 50% by weight. However, for feeds containing higher amounts of these compounds it has been found that their cracking leads to the formation of large amounts of lower molecular weight products, such as butane, propane, ethane, and methane, which significantly reduces the yield. in sought after products.

To overcome these drawbacks, the applicant has focused its research efforts on the development of catalysts (preferably not
ZSM) allowing isomerization of these compounds.

Many patents exist in this field, for example, patent WO 92/01657 describes and claims a charge dewaxing process with isomerization reaction in the presence of a Group VIII metal, a hydrogen pressure of between 100 KPa and 21000 KPa and a catalyst whose pore opening is between 0.48 nm and 0.71 nm and whose crystallite size is less than 0.5 Clam. This catalyst leads to improved performances in terms of yield compared to the catalysts of the prior art.

Object of the invention
The subject of the invention is a process for the selective hydroisomerisation of compounds having at least one n-alkane chain with more than 10 carbon atoms, in which the said compound to be treated is brought into contact with a catalyst comprising at least one molecular sieve. having a porous mono or two-dimensional network, whose accessible pore openings are delimited by at least 10 oxygen atoms, and the so-called bridge width distance between said pores being less than 0.70 nm, and said catalyst subjected to the standard test isomerization of n-heptadecane has, for a conversion of 95%, a selectivity of isomerized products of at least 70%.

Advantageously, this process makes it possible to convert a feedstock having a high pour point into a mixture having a lower pour point and a higher viscosity index.

The feedstock comprises, inter alia, linear and / or weakly branched paraffins having at least 10 carbon atoms, preferably from 15 to 50 carbon atoms and advantageously from 15 to 40 carbon atoms.

The process comprises the use of a catalyst comprising at least one molecular sieve having at least one type of pores whose opening is delimited by 10 oxygen atoms and which are the largest accessible pores present in the structure. The porous network of the zeolite is mono or two-dimensional, and preferably one-dimensional.

The bridge width between two pore openings (at least 10 oxygen atoms), as defined above, is less than 0.70 nm (1 name = 10-9 m), preferably between 0.50 nm and 0.68 nm, even more preferably between 0.52 nm and 0.65 nm. Preferably, the crystallite sizes are less than 2 μm (1 μm), advantageously less than 1 μm and preferably 0.4 μm.

The catalyst is further characterized in that for a conversion of the order of 95% by weight of n-heptadecane (n-C17) it leads to a selectivity to isomerized products greater than or equal to 70% and preferably from minus 80%, under the conditions of a standard isomerization test of n-C17 (TSI) which will be defined below. The isomerized products generally contain between about 65 and 80% by weight of mono-branched products and between about 20 and 35% by weight of multi-branched products, essentially bibranchs. Monobranched products are understood to mean linear paraffins comprising a single methyl group, and by bibranched products linear paraffins comprising 2 methyl groups which are not borne on the same carbon atom. By extension we define the multibranched. The hydroisomerization is thus selective.

On the other hand, the catalyst comprises at least one hydrodehydrogenating function, for example a Group VIII metal, and the reaction is carried out under the conditions described below.

The Applicant has in fact surprisingly discovered that one of the determining factors for obtaining high selectivities in isomerized products is the use of molecular sieves, characterized in that the opening of the largest pores is delimited by 10 oxygen atoms, the bridge width must be less than 0.70 nm, preferably between 0.50 nm and 0.68 nm, preferably between 0.52 nm and 0.65 nm.

This last point in particular is in contradiction with what is claimed in the patents previously cited in the prior art such as WO 92/01657 which claims a range of pore size for obtaining good yields of isomerized products.

The bridge width measurement is performed using a graphic design and molecular modeling tool such as Hyperchem or
Biosym, which make it possible to construct the surface of the molecular sieves in question and, taking into account the ionic rays of the elements present in the frame of the sieve, to measure the bridge width.

The use of such molecular sieves according to the invention under the conditions described above allows, in particular, the production of low pour point and high viscosity index products with good yields.

Detailed description of the invention
The molecular sieves according to the invention which can be used for the isomerization reactions of linear or slightly branched paraffinic hydrocarbons are zeolites, crystallized aluminosilicates such as Theta-1, NU-10, NU-23, EU-13, the report
If / AI is the one that is best for the desired application. Among the zeolites according to the invention also include zeolite NU-87 which has pore boundaries delimited by 10 and 12 oxygen atoms but whose accessibility to these is through pore openings with 10 oxygen atoms. The zeolite derivatives previously described having at least one heteroatom in the zeolite network and such that B, Fe, Ga, Zn are also included in the terms of the invention.

It has been observed that the catalysts according to the invention are characterized by a catalytic test called the standard isomerization test (TSI) of pure n-heptadecane which is carried out under a partial pressure of 150 kPa of hydrogen and a partial pressure of n-C17 of 0.5 kPa, ie a total pressure of 150.5 kPa in a fixed bed and with a constant n-C17 flow rate of 15.4 ml / h and a catalyst mass of 0.5 g.

The reaction is carried out in downflow. The conversion rate is set by the temperature at which the reaction takes place. The catalyst subjected to said test consists of pure zeolite and 0.5% by weight of platinum.

The screen generally contains at least one hydrodehydrogenating element, for example at least one Group VIII metal, preferably at least one metal selected from the group consisting of Pt or
Pd, which is introduced into the molecular sieve, for example by dry impregnation, by ion exchange or any other method known to those skilled in the art.

The metal content thus introduced, expressed in% by weight relative to the mass of molecular sieve engaged, is generally less than 5%, preferably less than 1% and generally of the order of 0.5% by weight. Under these conditions, a molecular sieve according to the invention must lead, for an n-C17 conversion rate of the order of 95% by weight (the conversion rate is regulated by the temperature), to a selectivity to isomerized products greater than or equal to equal to 70% by weight and preferably at least 80% by weight.

The isomerization selectivity of the standard isomerization test of n-C17 (TSln-C17) is defined as follows:
Selectivity Isomerization (%) =
mass of Cl 7 isomerized products (monobranched + multiblinded) in the recipe x 100 mass of products isomerized at C 7 in the recipe + mass of products C t 17- in the recipe at a conversion of n-C17 of the order of 95 %.

The C17- products are the compounds which have less than 17 carbon atoms, whatever their degree of branching.

In the case of the treatment of a real charge, the molecular sieve according to the invention is previously shaped. According to a first variant, the molecular sieve may be subjected to the deposition of at least one metal of the Vlil group, preferably chosen from the group formed by platinum and palladium, and shaped by any technique known to those skilled in the art. . It may in particular be mixed with a generally amorphous matrix, for example with a moist alumina gel powder. The mixture is then shaped, for example by extrusion through a die. The molecular sieve content of the mixture thus obtained is generally between 0.5 and 99.9% and advantageously between 10 and 90% by weight relative to the mixture (molecular sieve + matrix).

In the remainder of the text, the term "carrier" will be used to refer to the mixture of molecular sieve + matrix.

The shaping can be carried out with other matrices than alumina, such as, for example, magnesia, amorphous silica-aluminas, natural clays (kaolin, bentonite, sepiolite, attapulgite) and by other techniques than extrusion, such as pelletizing or coating.

The hydrogenating metal group VII I, preferably Pt and / or Pd, can also be deposited on the support by any method known to those skilled in the art and allowing the deposition of the metal on the molecular sieve. It is possible to use the competitive cation exchange technique in which the competitor is preferably ammonium nitrate, the competition ratio being at least about 20 and advantageously about 30 to 200. In the case of platinum or palladium, a platinum tetramine complex or palladium tetramine complex is usually used: these will then be deposited almost entirely on the molecular sieve.

This cation exchange technique can also be used to directly deposit the metal on the molecular sieve powder before it is mixed with a matrix.

The deposition of the Group VIII metal (or metals) is generally followed by calcining in air or oxygen, usually between 300 and 600 ° C for 0.5 to 10 hours, preferably between 350 ° C and 550 ° C. for 1 to 4 hours, then reduction in hydrogen, generally at 300 to 600 ° C for 1 to 10 hours; preferably it will operate between 350 "and 5500C for 2 to 5 hours.

Platinum and / or palladium can also be deposited, either directly on the molecular sieve or on the aluminum binder, before or after the shaping step, by carrying out anionic exchange with hexachloroplatinic acid, hexachloropalladic acid and / or palladium chloride in the presence of a competing agent, for example hydrochloric acid. In general after platinum and / or palladium deposition, the catalyst is as previously calcined and then reduced in hydrogen as indicated above.

The fillers which can be treated according to the process according to the invention are advantageously fractions having relatively high pour points whose value is to be reduced.

The process according to the invention can be used to treat various feeds ranging from relatively light fractions such as kerosenes and jet fuels to fillers having higher boiling points such as middle distillates, vacuum residues, gasols, middle distillates from FCC (LCO and HCO) and hydrocracking residues.

The charge to be treated is in most cases a C10 + cup of initial boiling point greater than about 175 ° C, or a cup
C20 + boiling above 315 ° C, and preferably a boiling heavy cut of at least 380 ° C. The process according to the invention is particularly suitable for treating paraffinic distillates such as middle distillates which include gas oils, kerosenes, jet fuels and any other fractions whose pour point and viscosity must be adapted to fit within the scope of the invention. specifications
The fillers which can be treated according to the process of the invention may contain paraffins, olefins, naphthenes, aromatics and also heterocycles and with a significant proportion of high molecular weight n-paraffins and very poorly branched paraffins as well. high molecular weight.

 The reaction can be conducted in such a way that the rate of cracking reactions remains low enough to make the process economically viable.

Typical fillers which can be advantageously treated according to the invention generally have a pour point above 0 ° C and more commonly above 15 ° C. The products resulting from the treatment according to the process have pour points less than 0 C and preferably less than about -10 C.

These fillers have contents of n-paraffins, (n-alkanes) with more than 10 carbon atoms, high molecular weight and paraffins, with more than 10 carbon atoms, very few branches also of high molecular weight, greater than 30% and up to about 90%, and in some cases even greater than 90% weight. The process is particularly advantageous when this proportion is at least 60% by weight.

Examples of other fillers that can be treated according to the invention and that are non-limiting in nature are the bases for lubricating oils, synthetic paraffins from the Fischer-Tropsch process, polyalphaolefins with a high pour point, synthetic oils. etc. The process can also be applied to other compounds containing an n-alkane chain as defined above, for example n-alkylcycloalkane compounds, or comprising at least one aromatic group.

The operating conditions in which the hydroisomerization is carried out according to the process of the invention are the following: the reaction temperature is between 170 and 500 ° C. and preferably between 180 and 450 ° C., the pressure is between 1 and 250 bar and preferably between 10 and 200 bar, the hourly space velocity (vvh expressed as the volume of feed injected per unit volume of catalyst per hour) is between about 0.05 and about 100 and preferably between about 0.1 and about 30 h-1.

The contact between the feedstock and the catalyst is carried out in the presence of hydrogen. The level of hydrogen used and expressed in liter of hydrogen per liter of feed is between 50 and about 2000 liter of hydrogen per liter of feedstock and preferably between 100 and 1500 liter of hydrogen per liter of feedstock.

The feedstock to be treated preferably has a nitrogen compound content of less than about 200 ppm by weight and preferably less than 100 ppm by weight. The sulfur content is less than 1000 ppm by weight
preferably less than 500 ppm and even more preferably less than 200 ppm by weight. The metal content of the filler, such as Ni or V, is extremely low, ie less than 50 ppm by weight, preferably less than 10 ppm by weight and even more preferably less than 2 ppm by weight.

The compounds obtained by said process according to the invention are essentially mono-branched, dibranched and multibranched with methyl groups. For example, in the case of a feed consisting of pure n-heptadecane (n-C17), methylhexadecane compounds, predominantly 2-methylhexadecane, and 2,7-dibranched compounds were selectively obtained; 2,8; 2.9; 2,10- and 2,11-dimethylpentadecane. All isomerized products represent more than 70% by weight of the products obtained at a conversion of 95% by weight. It is observed that the isomeric carbon atoms are separated by a distance at least equal to the bridge width.

The examples which follow illustrate the invention without, however, limiting its scope. They are given for a charge consisting of n-heptadecane (standard isomerization test, TSI).

Example 1 Catalyst C1 in Accordance with the Invention
The raw material used is an NU-10 zeolite in H form, which has a global Si / Al ratio of about 30, a pore opening delimited by 10 oxygen atoms and a bridge width, ie a distance between two pore openings of 0.55 nm. The crystallites of zeolite NU-10 are in the form of needles whose length is less than 1 μm and the section is between 0.1 and 0.4 μm.

The NU-10 zeolite is then dry impregnated with a solution of [Pt (NH 3) 4] Cl 2 so as to obtain, after a calcination and reduction step at 45 ° C., a Pt content of 0.5% by weight of platinum on the zeolite.

Then, 0.5 g of this zeolite loaded with platinum, pelleted (200-300 Am particle size fraction), are introduced into a fixed-bed reactor.

The standard isomerization test (TSI) of n-heptadecane is then carried out under a partial pressure of 150 kPa of hydrogen and a partial pressure of n-C17 of 0.5 kPa, ie a total pressure of 150.5 kPa in bed. fixed and with a constant n-C17 flow rate of 15.4 ml / h and a catalyst mass of 0.5 g downflow. The conversion rate is adjusted by the temperature at which the reaction takes place.

The temperature required in this example to reach 95% conversion weight of n-C17 is 1900C. At this temperature, the selectivity for isoménsés products is 93% by weight. The latter is defined as follows:
Selectivity Isomerization (%) =
mass of Ci 7 isomers (mono-branched + multi-branched) in the recipe mass of isomerised products in C "in the recene + mass of products C - in the recipe
Example 2 Catalyst C2 Not in Accordance with the Invention
The raw material used is a USY zeolite in H form, which has a global Si / Al ratio of approximately 5, a pore opening delimited by 12 oxygen atoms and a bridge width, ie a distance between two pore openings, greater than 0.7 nm.

The zeolite USY-H is then dry-impregnated with a solution of [Pt (NH 3) 4] Cl 2 so as to obtain, after the calcination and reduction steps at 450 ° C., a Pt content of 0.5% by weight. platinum on the zeolite.

Then, 0.5 g of this zeolite loaded with platinum, pelleted (200-300 clam size fraction), are introduced into a fixed-bed reactor.

The standard isomerization test (TSI) of n-heptadecane is then carried out under a partial pressure of 150 kPa of hydrogen and a partial pressure of n-C17 of 0.5 KPa, ie a total pressure of 150.5 kPa in bed. fixed and with a constant n-C17 flow rate of 15.4 ml / h and a catalyst mass of 0.5 g downflow. The conversion rate is adjusted by the temperature at which the reaction takes place.

The temperature required in this example to reach 95% conversion of n-C17 is 220 ° C. At this temperature, the selectivity for isomerized products is only 16% in this case. Example 1

This standard isomerization test is therefore a means for selecting the catalysts.

Example 3: according to the invention
The zeolite used in this example is the same NU-10 zeolite as that used in Example 1.

The zeolite is kneaded with SB3 type alumina supplied by Condéa. The kneaded paste is then extruded through a die having a diameter of 1.2 mm. The extrudates are then calcined at 500 ° C. for 2 hours in air and then dry impregnated with a solution of platinum tetramine chloride [Pt (NH 3) 4] Cl 2, and finally calcined in air at 550 ° C. The platinum content of the final catalyst C3 thus obtained is 0.7% by weight and the zeolite content, expressed relative to the total weight of the catalyst, is 60% by weight.

Evaluation of the catalyst C3 in hydroisomerization of a hydrocracking residue from a vacuum distillate.

The characteristics of this load are as follows

<tb> Content <SEP> in <SEP> sulfur <SEP> (ppm <SEP> weight) <SEP> 1 <SEP> 2 <SEP>
<tb> Content <SEP> in <SEP> nitrogen <SEP>(<SEP> m <SEP> oids <SEP> 2 <SEP>
<tb><SEP> PP <SEP> P
<tb> Flow <SEP> Point <SEP>("C)<SEP> +30
<tb> Initial <SEP> Point <SEP> 104
<tb><SEP> 5% <SEP> 325
<tb> 10% <SEP> 385
<tb><SEP> 50% <SEP> 452
<tb><SEP> 90% <SEP> 520
<tb><SEP> 95% <SEP> 536
<tb><SEP> Last <SEP> Point <SEP> 573
<Tb>
The catalyst whose preparation is described is then used to prepare a base oil by hydroisomerization of the charge described above.

The catalyst is reduced beforehand in hydrogen at 450 ° C. before the in situ catalytic test in the reactor, this reduction is carried out stepwise and consists of a plateau at 1500 ° C. for 2 hours and then a rise in temperature up to 450 ° C. C at a speed of 1 ° C / min, then a plateau of 2 hours at 450 ° C. During this reduction protocol, the hydrogen flow rate is 1000 liters of H2 per liter of catalyst.

The reaction is carried out at 300 ° C. under a total pressure of 12 MPa, a hourly volume rate of 0.9 h -1 and a hydrogen flow rate of 1000 1 H 2 per liter of feedstock, under which the net conversion to 400.degree. is 65% and the base oil yield is 86%.

The characteristics of the oil after hydroisomerization are reported in the table below.

<Tb>

<SEP> index of <SEP> viscosity <SEP> VI <SEP> 136
<tb> Flow <SEP> Point <SEP> -18
<tb> Yield <SEP> Oil / Load <SEP> (% <SEP> 86
<tb> weight)
<Tb>
This example shows the interest of using a catalyst according to the invention, which allows to lower the pour point of the initial charge, in this case a hydrocracking residue, while maintaining a high viscosity number (VI).

The present invention has been illustrated for the purpose of obtaining an oil, but other objectives can be achieved. Generally, the invention will be used to obtain multiple and localized connections.

Claims (17)

1. Process for selective hydroisomerization of compounds having at least  minus one n-alkane chain with more than 10 carbon atoms, in  which said compound to be treated is brought into contact with a catalyst  comprising at least one molecular sieve having a network  porous single or two-dimensional, including pore openings  accessible are delimited by at least 10 oxygen atoms, and  the distance said bridge width between said pores being lower  at 0.70 nm, and said catalyst subjected to the standard test  isomerization of n-heptadecane present, for a conversion  95%, selectivity to isomerized products of at least 70%. 2. Method according to one of the preceding claims, wherein  the bridge distance is between 0.50 and 0.68 nm. 3. Method according to one of the preceding claims, wherein  the bridge distance is between 0.52 and 0.65 nm. 4. Method according to one of the preceding claims, wherein  the molecular sieve has a crystallite size smaller than  2 I.Lm. 5. Method according to one of the preceding claims, wherein  the molecular sieve has a crystallite size smaller than  1 clam. 6. Method according to one of the preceding claims, wherein  the molecular sieve has a crystallite size smaller than  0.4, um. 7. Method according to one of the preceding claims, wherein  the molecular sieve is selected from the group consisting of NU-10,  NU-23, NU-87, and their derivatives including boron, iron,  gallium and / or zinc. 8. Method according to one of claims 1 to 6, wherein the sieve  molecular weight is selected from the group consisting of Theta-1, EU-13 and  their derivatives including boron, iron, gallium and / or zinc atoms. 9. Method according to one of the preceding claims, wherein  the catalyst contains at least one hydro element  dehydrogenating. The method of claim 9, wherein said element  belongs to group VIII. 11. Method according to one of the preceding claims, wherein  the pressure is between 1 and 250 bar, the temperature between  170 and 5000C, the hourly space velocity between 0.05 and 100 h-1,  and the hydrogen content between 50 and 2000 I of hydrogen / l of  charge. 12. Method according to one of the preceding claims, wherein  the compound to be treated is chosen from the group formed by the n  alkanes, n-alkylcycloalkanes and compounds having  least one aromatic group. 13. Method according to one of the preceding claims, wherein  the compound to be treated is present in a point charge  initial boiling point above 175 ° C. 14. Method according to one of the preceding claims, wherein  the compound to be treated is present in a point charge  initial boiling point of at least 380 ° C. 15. Method according to one of the preceding claims, wherein  the compound to be treated comprises an n-alkane chain having  at 50 carbon atoms. 16. Method according to one of the preceding claims, wherein  the compound to be treated comprises an n-alkane chain having  at 40 carbon atoms. 17. Method according to one of the preceding claims, wherein  the compound to be treated is present in a hydrocarbon feedstock  selected from the group consisting of middle distillates,  Vacuum residues, hydrocracking residues, paraffins  from the Fischer-Tropsch process, synthetic oils,  gasoil and middle distillate cuts from the FCC, oils,  polyalphaolefins.