CA1111073A

CA1111073A - Process for preparing aromatic hydrocarbons

Info

Publication number: CA1111073A
Application number: CA310,712A
Authority: CA
Inventors: Henricus M.J. Bijwaard; Frits M. Dautzenberg; Jan M. Oelderik
Original assignee: Shell Canada Ltd
Current assignee: Shell Canada Ltd
Priority date: 1977-10-17
Filing date: 1978-09-06
Publication date: 1981-10-20
Also published as: AU4073578A; NL7711350A; IT7828803A0; ZA785799B; GB2006260B; FR2405912A1; GB2006260A; FR2405912B1; IT1099979B; BE871122A; AU520964B2

Abstract

A B S T R A C T

Process for preparing aromatics from carbon monoxide and hydrogen. A mixture whose H2/CO molar ratio is less than 1.0, is contacted with a trifunctional catalyst containing at least one metal catalyzing the conversion of a H2/CO ? ?ture into hydrocarbons and/or oxygen-containing hydrocarbons, at least one metal catalyzing the water gas shift reaction and a crystal-line aluminosilicate zeolite having an SiO2/A12O3 molar ratio of at least 12 and a constraint index between 1 and 12.

Description

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PROCESS FOR PREPARING ARO~L~TIC HYDROCARBONS

The invention relates to a process for preparing aromatic hydrocarbons by catalytic reaction of carbon monoxide with hydrogen.

Hydroca.bon mixtures boiling in the gasoline range can be obtained. for instanceA by straight-run distillation of crude mineral oil. by conversion of heavier mineral oil fractions, for instance. by catalytic cracking. thermal cracking and hydrocracking and by conversion of lighter mineral oil fractions, for instance, by alkylation. ~'o 0 improve the octane number of the hydrocarbon mixtures thus obtained, they are often subjected to catalytic reforming, as a result of which the aromatics content increases.

In view of the increasing need of gasoline and the ` 15 decreasing reserves of mineral oil there is a great interest in processes permitting the conversion in an economically ;~ justified way of carbon-containing materials not based on mineral oil, such as coal, into hydrocarbon mixtures boiling in the gasoline range. It is desirable that these hydrocarbon mixtures should have a sufficiently high octane number, as a result of which they are suitable for use as gasoline without any fu-ther refining.

It is known that carbon-containing materials, such ~ as coal, can be converted in a relatively simple way ; 25 into mixtures of carbon monoxide and hydrogen by steam ., ~.

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gasification. It is further known that mixtures of carbon monoxide and hydrogen whose H2/CO molar ratio is more than l.0 can be converted in good yield into mixtures of hydrocarbons by contacting the gas mixtures with suitable catalysts. Attempts to achieve a commercially attractive process for the preparat;on of gasoline from carbon-containing materials, such as coal. by combining the two processes have met with serious objections. These - objections are in the first place connected with the composition of the m-xture oE carbon monoxide and hydrogen that is obtained in the steam gasification and further with the composition of the mixture of hydrocarbons formed in the conversion of the mixture of carbon monox;de and hydrogen.
It has been found that in the steam gasification fo obtaining a high yield of a mixture of carbon monoxide and hydrogen and for suppressing the formation of methane, tarry products and phenols, temperatures - higher than 1000C should be used. It has further been found that the Hz/CO molar ratio in the product obtained in the steam gasification is highly dependent on the temperature used and that at temperatures higher than lO00 C gas mixtures are obtained in which the H2/C0 molar ratio is smaller than lØ Such gas mixtures are ` 25 less suitable for conversion in the second stage of the above-mentioned combination process ;n which gas mixtures with a H2/CO molar ratio above l.0 are desired. An intermediate increase of the H2/CO molar ratio to above l.0 by applying the water gas shift reaction to these 3 gas mixtures with low H2/CO ratio is not suitable for commercial use, because this step implies that the gas ` with increased H2/CO molar ratio thus obtained should then be subjected to an expensive gas separation treatment to remove carbon dioxide~ before the gas can be converted in the sec:ond stage of the combination process.

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As regards the composition of the mixture of hydroca-bons formed in the conversion of the mixtu e of carbon monoxide and hydrogen it is noted that this mixture has a very wide molecular weight distribution and that it contains hardly any aromatics. This means that only part of this mixture consists of hydrocarbons boiling in the gasoline range and that, moreover, before this part can be used as gasoline it first has to be subjected to a catalyt;c reforming treatment to increase the aromatics content.
The Applicant has carried out an extensive investigation to examine to what extent it is possible to prepare from mixtures of carbon monoxide and hydrogen such as they are obtained in the high--temperature steam gasification of carbon-containing materials such as coal. aromatic ;; hydrocarbon mixtures with a high octane number that are - suitable for use as gasoline without any further refining.
In the investigation emphasis has been placed on the implementation of this conversion in one stage.

2~ It has been found that the above-mentioned requirements ;` can indeed be met by contacting the gas m-xture with a catalyst which combines three functions. In the first place the catalyst should comprise one or more metal components having catalytic activity for the conversion of a H2/CO mixture into hydrocarbons and!or oxygen-containing hydrocarbons. The catalyst should further contain a crystalline `~ aluminosilicate zeolite with an Si~2/A1203 molar ratio of at least 12 and a constraint index between 1 and 12.
Finally, the catalyst should contain one or more metal

3 components having catalytic activity for the water gas - shift reaction.
The present patent application therefore relates ; to a process for preparing aromatic hydrocarbons by catalyt;c reaction of carbon monoxide with hydrogen, in which process a mixture of carbon monoxide and hydrogen, whose H2/CO

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- molar ratio is less than l.0 is converted in one step into an aromatic hydrocarbon mixtu e by contacting the gas mixture with a trifunctional catalyst containing one o. more metal components having catalytic activ;ty for the conversion of a H2/CO m;.xture into hydrocarbons and/or o~ygen-containing hydrocarbons one o more metal components having catalyt;c activity for the water gas : shift reaction and a crystalline aluminos.ilicate zeolite - having an SiO2/Al203 mola- ratio of at least l:X and a constraint index between l and 12.
The process according to the invention starts from a mixture of carbon monoxide and hydrogen whose H2/C0 : molar ratio is 7ess than lØ As was mentioned earlier, : such a mixture can be readily prepared by steam gasification :-~ 15 of a carbon-containing material at a high temperature.
Examples of such materials are brown coal ! anthracite, coke, crude mineral oil and fractions thereof, as we~l as oils extracted from tar sand and bituminous shale.
: During the steam gasification the feed, in finely divided; 20 form, is converted with steam and oxygen or air, if des-red enriched with oxygen. i.nto a gas mixture contai.ning. inter ~ alia, hydrogen, carbon monoxide, carbon dioxide, nitrogen. and water. The steam gasification is preferably carriedout at a temperature between lO00 and 2000C and a pressure -~ 25 between lO and 50 bar. In order to be able to remove contaminants such as ash! carbon-containing material . and hydrogen sulphide from the gas obtained in the steamgasification, which has a temperature higher than 1000C, this gas should first be cooled down to a temperature 3 between lO0 and 200C. This cooling can very suitably ; be effected in a boiler :in which steam is generated with the aid of the waste heat. The cooled gas can be freed from nearly all solid components by washing it with water. After this washing treatment, during which the temperature of the gas has fallen to 20-80 C~ the . .
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:- ~ ,', ~ : , gas is furthe. pur;fied by removal of hydrogen sulphide and carbon dioxide. This may very su;tably be effected with the aid of the ADIP process or the S~LFINOL process.
The trifunctional catalysts which are used in the process according to the invention contain, in add;tion to the metal componen~s. a crystalline aluminosilicate zeolite of a special class. These zeolites effect a high conversion of a1iphatic hydrocarbons into aromatic hydrocarbons in commercially desirable yields and they are in general very act~ve in conversion reactions in which aromatic hydrocarbons - are involved. Although they have an uncommonly low alumina content, i.e. a high SiO2/Al203 molar ratio, they are very `~ active, even when the SiO2/Al203 molar ratio is more than 30.
This activi~y is surprising. because the catalyt;c activity of zeolites is generally ascribed to the aluminium atoms of the ; lattice and the cations present in combination with these alumin;um atoms. These zeolites retain their crys~alline character for a very long time in sp:.te of the presence of steam, even at high temperatures such as those which effect irreversible collapse of the crystal lattice of other zeolites J
e.g. those of the X- and A-type. If carbon-containing deposits are formed, they can be removed by burning them at temperatures that are higher than the temperatures usually employed for restoring the activity. In many media zeolites of this group show a very slight capability of forming coke, as a result of which the operational times between regenerations are very long.
An important property of the crystal structure of this class of zeolites is that it provides constrained access to and 3 egress from the intracrystalline free space, because the pore size is more than about 5 ~ and the pore windows are of about the same size as are provided by rings of 10 oxygen atoms.
Obviously~ these rings are those formed by the regular arrange-ment of the tetrahedrons forming the anionogenic lattice of the crystalline aluminosilicate, the oxygen atoms themselves being ~ . . , .

bound to the silicon or aluminium atoms in the centres of the tetrahedrons. In short. the zeolites that are preferably used according to the invention have a ratio of silica to alumina of at least 12 and a structure that gives constrained access to the free space in the crystals.
The said ratio of silica to alumina can be determined by usual analyis. This ratio serves the purpose of representing as precisely as possible the ratio in the rigi~1 anionogen;c lattice of the zeolite crystal, so that aluminium in the binder materiai or in cationogenic or other form in the 3 channels is excluded. Although zeolites having a molar SiO2/A12G3 ratio of at least 12 are suitable, use is preferably made of zeolites having a higher ratio of at least 30 and in particular having an SiO2/A12G3 ratio between 60 and 400. After activation~
these zeolites obtain an intracrystalline sorptive power for n-hexane that is greater than for water, i.e. they show hydro-phobic properties. It is assumed that this hydrophobic nature is an advantage in the present invention.
The zeolites that are suitable according to the invention freely sorb n-hexane and have a pore size of more than 5 ~.
2G The structure must further provide constrained access to certain large molecules. Sometimes it is possib~e to infer from a known crystal structure whether such a constrained access exists. If~ for instance, the only pore windows in a crystal are formed by rings of eight oxygen atoms, the access for molecules having a larger cross-section than n-hexane is ex-cluded and then the zeolite is not of the desired type. Zeolites ~ with windows of rings with 10 atoms are preferred, although an ; excessive puckering or pore blockage may deactivate these zeolites. In general~ zeolites with windows of rings with 12 atoms have been found to give no suffic;ently constrained ~` access to effect the conversions desired according to the invention, although as a result of pore blockage or other causes structures ;` are possible here which are active.
Instead of trying to judge from the crystal structure : ~ .

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'`.rt`73 whether a zeol;te has the requ.red constra;ned access or not, a simple constraint ;ndex determination can be carried out by cont;nuously passing a mixture of equal quantities by weight of n-hexane and 3-methylpentane at atmospheric pressure - 5 across a small samplel about 1 g or less, of the zeolite according to the process given he~einafter. A samp'e of the zeolite ln the form of granules or extrudate is ground to a particle size which is about equal to thae of coarse sand and introduced into a glass tube. Before the examination the zeolite is treated for at least 15 minutes with a stream of air of about 538 C. The zeolite is thereupon purged w;th helium and the temperature is set at a value between about 285C and about 510C to give a total conversion between 10~ and 60~. The mixture of hydro--carbons is passed across the zeolite at a volume velocity of 1 (i.e. 1 volume of liqu-d hydrocarbon pe volume of zeolite per hour), the mixture being diluted with helium such that the molar ratio of helium to total hydrocarbons is 4:1.
` After a running time of 20 minutes a sample of the e~fluent is taken and analysed ~the best way is by gas chromatography) ~0 in order to determine the fraction of each of the two hydro^
carbons that has not been converted.
The constraint index is calculated as follows:
C0n9traint index = _log~t_e~ma_n_n~V fracti_n O~-n-hexane) lolog (remaining fraction of 3--methylpentane) The constraint index approaches the rat-io of the velocity ~5 constants fo~ cracking the two hydrocarbons. Catalysts which are suitable for the present process are those containing a zeolite with a constraint index betw~en 1 and 12. For some representative materials, some of which fall outside the scope of the invention, the values for the constraint index (CI) are given below ':~

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CI
ZS~1-5 8.3 ZS~I-ll 8.7 ZS~1-12 2 ZS~1-38 2 : ZSM-35 4 5 TMA-offretite 3.7 Beta 0.6 ZS~1-4 0.5 . Acid mordenite 0.5 Amorphous silica-alumina 0.6 Erionite 38 Examples of zeolites of the class defined here are ZSM-5, ZSM-ll, ZSM-12, ZSM-35 and ZSM-38. United States patent 3,702,886 describes ZSM-5.
ZSM-ll is described in United States patent 3,709,979 and ZSM-12 in United States Patent 3,832,449.
Naturally occurring zeolites may sometimes be converted into this type of zeolite by various activation methods and other treatments such as base e~change, steam treatment, alumina extraction and calcination or combin-:
ations of these treatments. Of the naturally occurring minerals that may be treated in this way are to be mentioned: ferrierite, brewsterite, stilbite, 3 dachiardite, epistilbite, heulandite and clinoptilolite. The crystalline ~ aluminosilicate zeolites which are preferably used are ZSM-5, ZSM-ll, ZSM-12, .
- ZSM-35 and ZSM-38, particular preference being given to ZSM-5.
According to a preferred aspect of the invention the zeolites used in the catalysts have in the dry hydrogen form a crystal lattice density of at least 1.6 g per cm . The dry-state density can for known structures be calculated from the number of silicon plus aluminium atoms per 1000 R, as described for instance on page 19 of the article on zeolite structure by W.M. ~teier. This article is to be found in "Proceedings of . ~

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&73 _9_ the Conference on Molecular Sieves", London! April 1967. published ~- by the Society of Chemical Industry~ London, 1968. If the crystal structu-.e is un~no~n! the density of the crystal lattice can be determined according to classical. pycnometer methods. The density may be dete mined. for instance~ by ;mmersing the zeolite in the dry hydrogen form in an o~ganic solvent which is not sorbed by the crystal. It may be that the extraordinary~ long lasting activity and stability of this class of zeolites is connected with the high density of the anionogenic lattice of lQ the crystal~ which is at least 1.6 g per cm3. Obviously, this high density has to be associated with a relatively small free space in the crystal~ which may be expected to lead to stabler structu~es. However? this free space seems to be important as the seat of the catalytic activity.
Below the densities are given of the crystal lattice of some representative zeolites. of which some fall outside the scope of the ~nvention .
Zeolite Volume of cavities, Density of lattice, cm ~cm g/cm3 ___ _ _ _ .___ _ _ _ _ __ 2Q Ferrierite 0.28 1.76 Mordenite 0.2S 1.7 ZSM--5? -11 0.29 1.79 Dachiardite 0.32 1.72 L 0.32 1.61 25 Clinoptiloiite 0.34 1.71 Laumontite 0.34 1.77 ZSM-4 (omega) 0.38 1.65 Heulandite 0.39 1.69 - P 0.41 1.57 30 Offretite 0.40 1.55 Levynite 0.40 1.54 Erionite 0.35 1.51 Gmelenite 0.44 1.46 Chabazite 0.47 1.45 35 A 0.5 1.3 Y 0.48 1.27 ' ` ' ' :
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The trifunctional catalysts which are used in the process according to the invention contain one or more metal components having catalytic activ;ty for the conversion of a H2/CO mixture into hydrocarbons and/or oxygen-containing hydrocarbons, one or more metal com-ponents having catalytic activity fo. the water gas shift reaction and a crystalline atuminosilicate zeolite as def;ned hereinbefore having catalytic activity or the conversion of acyclic hydrocarbons and/or oxygel1-containing acyclic hydrocarbons into an aromatic hydrocarbon mixture boiling in the gasoline range. The rat;o in which the three catalytic Eunctions are present in the catalyst may vary within wide limits and is substantially determined by the activity of each of the catalytic functions. For~
in the process according to the invention the object is that of the acyclic hydrocarbons andtor oxygen-containing acyclic hydrocarbons formed under the influence of the first catalytic function. as much as possible is converted under the influence of a second catalytic function into an 23 aromatic hydrocarbon mixture boiling in the gasoline range, and that of the water liberated in the conversion of the mixture of carbon monoxide and hydrogen into hydrocarbons and/or in the conve.sion of oxygen-containing hydrocarbons into an aromatic hydrocarbon mixture, as much as possible reacts under the influence of a third catalytic function with the carbon mono-xide present in an excess amount in the mixture of carbon monoxide and hydrogen with Eormation of a mixture of hydrogen and carbon dioxide. In the composition of an optimum trifunc-tional catalyst to be used in the process according to the invention, which catalyst contains a given quantity of a first catalytic function having a given activity, it is therefore possible to do with less of the other catalytic functions according as these are more active.
~lthough the catalysts according to the invention are described in this patent application as catalysts containing .
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one or mo~e metal components having catalytic activity for the conversion of a H2/C0 mixture into hydrocarbons and/or oxygen-containing hydrocarbons and one o. more metal components having catalytic activity for the water gas shift reaction~
this means in no way that metal components each having in themselves one of the two catalytic functions should always separately be present in the catalysts according to the invention. For. it has been found that metal components and combinations of metal components having catalyt;c activity for 0 the conv~rsion of a H2/C0 mixture into substantially oxygen-containing hydrocarbons as a rule also have sufficient catalyt;c activity for the water gas shift reaction, so that in ~- such a case incorporation of one metal component or one com-bination of metal components into the catalysts according to the invention will suffice. Examples of such metal components are the metals chosen from the group formed by the metals zinc.
copper and chromium. I~hen use is made of trifunctional cata-lysts according to the invention containing these metals, preference is given to catalysts containing combinations of at ~; 20 least two of these metals, for instance the combination zinc-copper, zinc-chromium or zinc-copper-chromium. Pa-ticular preference is given to a trifunctional cata~yst containing in addition to the crystal]ine aluminosilicate zeolite the metal combination zinc-chromium. Metal components and combinations of metal components having catalytic activity for the conversion of a ~ /C0 mixture into substantially hydrocarbons have as a . 2 rule no o- insufficient activity for the water gas shift react-ion. When use is made of such metal components or combinations of metal components in the catalysts according to the invent-33 ion, one or more separate metal components having catalytic activity for the water gas shift reaction should therefore be incorporated therein.
The trifunctional catalysts which are used according to the invention are preferably composed of two or three - , :

separate catalysts. which will for convenience be designated caealysts X, Y and Z. Catalyst X is the catalyst containing the metal components having catalyt;c activity for the conversion of a H2/CO mixture into hydrocalrbons and/or oxygen-- containing hydrocarbons. Catalyst Y is the crystalline aluminosilicate ~eolite. Catalyst Z is the catalyst containing the metal component having catalytic activity for the water gas shift reaction. As has bee~ explained hereinbefore tl~e use of a Z-catalyst may be omitted in some cases.
1~ If as the X-catalyst a catalyst is used wh;ch is capable of converting a H2/CO mixture into substantial]y oxygen-con~
taining hydrocarbons, preference is g;ven to a catalyst which is capable of converting the H2/CO mixture into substant,ally methanol and/or dimethyl ether. For the conve~s;on of a H2/CO
mixture into substantially methanol. catalysts containing the metal combinat;ons mentioned hereinbefore are very su;table.
IE desired, the said metal comb-inations may be emplaced on a carrier material. By introducing an acid function into these catalysts, for instance by emplacing the metal combination on 23 an acid carrier, it may be effected that apart from the - conversion of the H2/CO mixture into methanol a considerable part of the mixture will be converted into dimethy] ether.
X-catalysts which are capable of converting a H2/CO
mixture into substantially hydrocarbons are referred to in the literature as Fischer-Tropsch catalysts. Such catalysts often contain one or more metals of the iron group or ruthenium together with one or more p-omoters to ;ncrease the activity and/or selectivity and sometimes a carrier material such as kieselguhr. They can be prepared by precipitation~ melt;ng and by impregnation. The preparation of the catalysts containing one or more metals of the iron group, by impregnation, takes place by impregnating a porous carrier with one or more aqueous solutions of salts of metals of the iron group and, optionally.
of promoters~ followed by drying and calcining the composit;on.
If in the process according to the invention use is made of a ~ lL~ '73 -l3-';
catalyst combination in wh;ch catalyst X is a Fischer-Tropsch catalyst, it is p eEerred to cnoose for this purpose an iron or cobalt catalyst. in particular such a catalyst which has been prepared by impregnation. Ve.y su table Fischer--Tropsch cata]ysts for use in the caealyst combinations according to the invention are the catal~sts.prepared by Impregnation f acco-ding to the ~ e~a~s patent a~r~ss~s~ No. 76~6~.
The catalysts concerned contain per lOO pbw carrier 10-75 pbw of one or more metals of the iron group. together with one or 10 more promote~s in a quantity of l-50~ of the quantity of metals of the iron group p-esent on the catalyst. which catalysts have such a specific average pore diameter ~p) of at most lO.OOO nm and such a specific average particle diameter (d) of at most 5 mm~ that the quotient p/d is more than 2 (p in nm and d in mm).
If in the process according to the invention the object is to use a catalyst combination of which X is a Fischer- Tropsch iron catalyst, it is preferred to choose an iron catalyst containing a promoter combination consisting of an alkalimetal !
a metal that is easy to reduce ! such as copper or silver and, optionally. a metal that is hard to reduce ? such as aluminium or zinc. A very suitable iron catalyst for the present purpose is a catalyst prepa-ed by impregnation containing iron.
potassium and copper on silica as the carrier. If in the process according to the invention the object is to use a catalyst combination of which X is a Fischer-Tropsch cobalt catalyst? it is preferred to choose a cobalt catalyst containing a promoter combination consisting of an alkaline-earth metal and thorium, uranium or cerium. A very suitable Fischer-Tropsch cobalt catalyst for the present pur-30 pose is a catalyst prepared by impregnation containing cobalt,magnesium and thorium on silica as the carrier. Other very suitable Fischer-Tropsch cobalt catalysts prepared by impregnaeion are catalysts containing. in addition to cobalt, one of the elements chromium, titaniumS zirconium and zinc on =ilica =9 the c~lrier. IE desired, it ;9 also possible to use ': , ~ ~.
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` in the process according to the invention catalyst combinations containing `~ an X-catalyst, wllicll is capable of converting a H2/C0 mixture into a mixture . .
- containing both hydrocarbons and oxygen-containing hydrocarbons in compar-able quantities. As a rule, such a catalyst has sufficient catalytic activ-ity for the water gas shift reaction, so that the use of a Z-catalyst in the combination can be omitted. An example of an X-catalyst of this type is an iron-chromium oxide catalyst. If desired, it is also possible to use in the process according to the invention catalyst combinations containing two or :- more X-catalysts, for instance in addition to a catalyst of the X-type which . 10 is capable of converting a 1-l2/C0 mixture into substantially hydrocarbons, a second catalyst of the X-type which is capable of converting a H2/CO mixture into substantially oxygen-containing hydrocarbons.
Z-catalysts which are capable of converting a H20/C0 mixture into ,. a H2/C02 mixture are referred to in the literature as CO-shift catalysts.
Such catalysts often contain one or more metals of the group formed by iron, chromium, copper, zinc, cobalt, nickel and molybdenum as the catalytically active component, either as such, or in the form of their oxides or sul-phides. Examples of suitable C0-shift catalysts are the mixed sulphidic cat-alysts according to British patent No. 1,472,595 and Indian Patent No.
1~401,246 and the spinel catalysts according to British patent No. 1,536,652.
If in the process according to the invention use is made of a catalyst com-bination in which a Z-catalyst is present, it is preferred to choose a cat-alyst which contains both copper and zinc, in particular a catalyst in which the Cu/Zn atomic ratio lies between 0.25 and 4Ø
- In the trifunctional catalysts the catalysts X, Y and, optionally, Z may be present as a mixture, in which, in principle, each particle of cat-; alyst X is surrounded by a number of particles of catalyst Y and, optionally, `' - 1~ _ X

catalyst Z and conversely. If the process is carried out with use of a fixed catalyst bed, this bed may be built up of alternate - 14a -~ . ~
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- layers of particles of catalysts X? Y and. opt;onally. Z. If the two or th ee catalysts are used as a mixture. this mixtuce may be a macromixture or a miccom xture. In the first case the trifunctional catalyst consists of two or three kinds of --/ 5 macropart;cles of wh;ch one kind is completely made up of catalyst X, the second Xind completely of catalyst Y and~
optionally. a third kind completely of catalyst Z. In the ` second case the trifunct;onal catalyst consists of one k-ind of macroparticles. each macroparticle being made up of a large number of mic-roparticles of eac:h of the catalysts X, Y and.
optionally! Z. Trifunctional catalysts according to the invention in the form of micromixtures may be prepared. for . instance. by thoroughly mixing a fine powder of catalyst X with ; a fine powder of catalyst Y and, optionally, with a fine powder of catalyst Z and shaping the mixture to larger particles. for ~- instance, by extruding or pelletizing. In the process according ~ to the invention it is preferred to use tr;functional catalysts -. in the form of micromixtures.
The trifunctional catalysts which are used acco.ding to ~ 2~ the invent;on may also have been prepared by incorporating the metal components having catalytic activity for convert-;ng aH2/CO mixture into hydrocarbons and/or oxygen-containing hydrocarbons and, optionally, the metal components having catalytic activity for the water gas shift reaction into the 25 crystalline aluminosilicate zeolite, for instance by impregnation or by ion exchange.
The crystalline aluminosilicate zeolites which are used in the process according to the invention are usually prepared from an aqueous mixture as the starting material which contains 30 the following compounds in a given ratio: one or more compounds : of an alkali or alkaline-ea-th metal, one or more compounds containing a mono- or bivalent organic cation or from which such a cation is formed dur-ing the preparation of the zeolite, ~ one or more s;licon compounds and one or more aluminium ; 35 compounds. The preparation is effected by maintain;ng the ~ , ' . ` , ~ " ' " - :
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--16~ 73 mixture at elevaeed temperature until the zeolite has been formed and then separating the crystals of the zeolite from the mother liquor. The zeolites thus prepa~ed contain alkali and/or alkaline--earth metal ions and mono- and/or bivalent organic cat;ons. Be~ore being used in the trifunctional catalysts according to the invention at least part of the mono-and/or bivalent organic cations intcoduced during the preparation are prefe.ably converted into hydrogen ions. for instance by calcining and at least part af the exchangeable 13 mono- and/or b~valent cations inteoduced during the preparation are preferably replaced by other ions! in particular hydrogen ions, ammonium ions and/or ions of the rare-earth metals. The - crystalline aluminosilicate ~eolites used in the trifunctional catalysts according to the invention preferab'y have an alkali metal content of less than l %w and in particular of less than 0.05 70W. If desired. a binder material such as bentonite or kaolin may be incorporated in the trifunctional catalysts.
The process according to the invention preferably starts from a mixture of carbon monoxide and hydrogen whose H2/C0 2~ molar ratio is more than 0,4.
The process according to the invention is preferably carried out at a temperature of from ~00 to 500 C and in particula~ of from 300 to 450CI a pressure of from 1 to 150 bar and in particular of from 5 to lO0 bar and a space velocity of from 50 to 5000 and in particular of from 300 to 3000 Nl gas/l catalyst/hour.
The process according to the invention can very suitably be carried out by passing the feed in upward or in do-~nward direction through a vertically disposed reactor in which a ; 30 fixed or a moving bed of the trifunctional catalyst concerned is present. The process may. for instance~ be carried out in the so-called fixed-bed operation, in bunker-flow operation or in ebulated-bed operation. It is preferred to use catalyst particles then with a diameter between l and 5 mm. If desired, the process may also be carried out in fluidized-bed operation : . , , : :
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-17~ 3 ;~' or with the use of a suspension of the catalyst in a hydro--carbon o-l. It is preferred to use catalyst particles then w~th a diameter between 10 and 150~/~m.
The invent;on w;ll now be expla;ned w;th reference to ~, 5 the Eo71Owing examples.
Example_I
ZSM-~5 ~zeolite A) was prepa.ed as follows. A mixtu e of SiO2~
-~ N A12' NaOH and !: (C3H7)4N /oH in water with the molar compositiOn 2' A--2O3' 9/ (C3H7)4N f?O. 2~-1 S;O2- 480 H20 was heated for 48 hours in an autoclave at 150 C under autogenous p{essure.
; 10 After having cooled the reaction mixtuTe. the zeolite formed was filtered off. washed with water unti] the pH of the wash water ' was about 8 and dried for two hours at 120C. With zeolite A as' the starting material zeolite B was prepa-ed by. successively. cal-cining zeolite A at 500 C. boiling with 1.0 molar NH4NO3 solution.
washing with water, boiling again with 1.0 mo~ar NH4NO3 soluti,on and washing. drying for two hours at 120C and calcining for four hours at 500C.
_xample_II
A catalyst was prepared by thoroughly mixing equal parts by weight of the following three finely powdered 2C materials a) a Fe/Cu/K/SiO2 Fischer-Tropsch catalyst;
b) zeolite B;
c) a Cu/Zn CO shift catalyst.
; The catalyst was pressed to particles having a diameter of 1-3 mm and tested for the one-stage preparation of an aromatic hydrocarbon mixture starting from a mixture of carbon monox;de and hydrogen. The testing was carr;ed ' out in a 250-ml reactor, in which a fixed catalyst bed having a volume of 50 ml was present. Previous to the testing the catalyst was treated with hydrogen for two hours at 280C. A mixture of carbon monox;de and hydrogen with a H2/co molar ratio of 0.5 was then passed across the catalyst at a temperature of 2~0C. a pressure of '~ 30 bar and a space velocity of 1000 Nl gas/l catalyst/h.

- -18- ~ 73 The results of this experiment are given below.
C0 conve.sion ! % 80 H2 conversion, % 94 - Product composit;on. %w on C product _ .. _ ~ . _ _ .. .. . . . _ _ _ ._ .. I _ __ . . _.
, 5 Cl l6 . C2 10 5 12 -i C13 Clg 6 C5 product compos~tion. YOW on C5 product o'.efins 45 paraffins 45 aromatics 10 Example III
A catalyst was prepared by mixing an Fe--Cr203composition with zeolite B in a weight ratio of 1 : 1. Both materials were present in the catalyst in the form of particles having a diameter of 0.15-0.3 mm. The Fe-Cr303 compos;tion used catalyses both the reduction of C0 to a product 23 containing about equal portions of Fischer-Tropsch product and methanol, and the water gas shift reaction. The catalyst obtained by mixing was tested for the one-stage preparat;on , of an aromatic hydrocarbon mixture starting from a mixture : of carbon monox;de and hydrogen. The testing was carried 2~ out in a 50-ml reactor, in which a fixed catalyst bed having a volume of 7.5 m] was present. A mixture of ca bon monoxide and hydrogen with a H2/C0 molar ratio of 0.5 was passed across the catalyst at a temperature of 350C~
a pressure of 30 bar and a space velocity of 1000 Nl gas/l 30 catalyst/h. The results of this experiment are given below C0 conversion, % 56 H2 conversion~ % 75 .

, .

Product composition._7.w _n_Cl product - Cl 15 C5~C12 39 - C5 _product composition _~Ow on_C5 produc~
paraffins 24 10 aromatics 76 ; Examp]e IV
A catalyst was prepared by mixing a Cu-ZnO composition with zeolite B in a weight ratio of 1 : 1. Both mater;als were present in the catalyst in the form of particles having a diameter of 0.15-0.3 mm. The Cu-ZnO composition used catalyses both the reduction of CO to methano] and water gas shift reaction. The catalyst obta;ned by mixing was tested for the one--stage p eparation of an aromat~c hydrocarbon mixture starting from a mixture of hydro~en ~ and carbon monoxide having a H2/CO molar ratio of 0.5.
: 20 The testing was carr;ed out in the same way as described in Example III. The results of th;s experiment are given below CO conversioni % 45 H2 conversion. % 48 - ~5 Product composition. ~OW on Cl pro uct

4 14 3~ C --C 29 Example V
A catalyst was prepared by mix;ng a ZnO-Cr2O3 composition ., :

-20~ 7~

- w;th zeol;te B in a we;ght rat;o of 5 : 1. Both materialswere present ;n the catalyst in the form of particles having a diameter of 0.15-0.3 mm. The ZnO--Cr203 composition used catalyses both the reduction of C0 to methanol and the water gas shift reaction. The catalyst obtained by mixing was tested for the one-stage preparat-ion of an aromatic hydrocarbon mixture starting from a mixture of carbon monox;de and hydrogen having a H2!C0 molar ratio of 0.5. The testing was ca~r;ed out in substantially 10 the same way as described in Example III. with the proviso that the pressure was 40 bar ;nstead of 30 bar. The results of this expe.iment are given below C0 conversion, % 48 H2 conversion. % 52 15 Product composition. %w on C product -C5 +12 67 : C13 5 C5 product composition. ~OW on C5 product paraffins + olefins 9 naphthenes 6 25 aromatics 86 .

.,

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A process for preparing aromatic hydrocarbons by catalytic reaction of carbon monoxide with hydrogen characterized in that a mixture of carbon monoxide and hydrogen, whose H2/CO molar ratio is less than 1.0, is converted in one step into an aromatic hydrocarbon mixture by contacting the gas mixture with a trifunctional catalyst containing one or more metal components having catalytic activity for the conversion of a H2/CO mixture into hydro-carbons and/or oxygen-containing hydrocarbons, one or more metal components having catalytic activity for the water gas shift reaction and a crystalline aluminosilicate zeolite having an SiO2/A1203 molar ratio of at least 12 and a constraint index between 1 and 12.

2. A process according to claim 1, characterized in that the tri-functional catalyst contains a crystalline aluminosilicate zeolite having an SiO2/A1203 molar ratio of at least 30.

3. A process according to claim 2 wherein said molar ratio is between 60 and 400.

4. A process according to claim 1, characterized in that the tri-functional catalyst contains a crystalline aluminosilicate zeolite in which at least part of the mono-and/or bivalent organic cations introduced during the preparation has been converted into hydrogen ions and in which at least part of the exchangeable mono-and/or bivalent cations introduced during the preparation have been replaced by other ions.

5. A process according to claim 4 wherein said other ions are selected from the group consisting of hydrogen ions, ammonium ions and rare-earth metal ions.

6. A process according to claim 1, characterized in that the tri-functional catalyst contains a crystalline aluminosilicate zeolite having an alkali metal content of less than 1 %w (and preferably of less than 0.05 %w).

7. A process according to claim 6 wherein said alkali metal content is less than 0.05%w.

8. A process according to claim 1, characterized in that the tri-functional catalyst is composed of three separate catalysts of which the first catalyst (catalyst X) contains the metal components having catalytic activity for the conversion of a H2/CO mixture into substantially hydro-carbons, the second catalyst (catalyst Y) is the crystalline aluminosilicate zeolite and the third catalyst (catalyst Z) contains the metal components having catalytic activity for the water gas shift reaction.

9. A process according to claim 5, characterized in that catalyst X is an iron or cobalt catalyst, (and has preferably been prepared by impregnation).

10. A process according to claim 9 wherein said iron or cobalt catalyst has been prepared by impregnation.

11. A process according to claim 8, characterized in that catalyst Z is a catalyst which contains both copper and zinc.

12. A process according to claim 11 wherein said catalyst Z contains copper and zinc in a Cu/Zn atomic ratio of between 0.25 and 4Ø

13. A process according to claim 8, 9 or 11, characterized in that a trifunctional catalyst is used which consists of one kind of macroparticles, each macroparticle being build up of a large number of microparticles of each of the catalysts X, Y and Z.