NZ201367A - Preparation of crystalline iron silicates and use in production of aromatic hydrocarbons from syngas - Google Patents

Description

New Zealand Paient Spedficaiion for Paient Number £01 367 NEW ZEALAND PATENTS ACT, 1953 No: Date: COMPLETE SPECIFICATION PROCESS FOR THE PREPARATION OF CRYSTALLINE SILICATES We, SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ B.V., a Netherlands company, of Carel van Bylandtlaan 30, The Hague, The Netherlands hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: (followed by page -la-) rnoocoo pon the preparation of crystalline silicates The invention relates to a process for the preparation of crystalline silicates having improved catalytic properties.

Mixtures of carbon monoxide and hydrogen can be 5 converted into aromatic hydrocarbon mixtures by the use of a mixture of two catalysts, one having the property of catalyzing the conversion of a H2/C0 mixture into oxygen-containing organic compounds, and the other being a crystalline iron silicate 10 capable of catalyzing the conversion of oxygen-containing organic compounds into aromatic hydrocarbons. The said crystalline iron silicates are characterized in that, after one hour's calcination in air at 500°C, they have the following properties: 15 a) thermally stable up to a temperature of at least 600°C; b) an X-ray powder diffraction pattern in which the strongest lines are the four lines listed in Table A: 901367 2 TABLE A d(&) Relative intensity 11.1+0.2 VS .0+0.2 VS 3-84 + 0.07 S 3.72 + 0.06 S in which the letters used have the following meanings: VS = very strong; S = strong, and c) in the formula which represents the composition of the silicate, expressed in moles of the 5 oxides, the Si02/Fe20^ molar ratio is 75-300.

In the present patent application a crystalline silicate having a thermal stability of at least t°C should be taken to be a silicate whose X-ray powder diffraction pattern remains substantially unchanged 10 upon heating to a temperature of t°C.

The crystalline silicates used in the catalyst mixtures may be prepared starting from an aqueous mixture comprising the following compounds: one or more compounds of an alkali metal (M), one or more 15 amines of the general formula R^R^^N, in which R^ is an alkyl group and 3X1(1 ^3 are an alkyl group or a hydrogen atom, one or more silicon compounds with a high Si02 content and one or more compounds, comprising iron in the trivalent form. In the 3 present patent application silicon compounds with a high Si02 content should be taken to be silicon compounds which, after drying at 120°C and calcination at 500°C, yield a product with a Si02 content higher 5 than 90$w. The crystalline silicates are prepared by maintaining the mixture at an elevated temperature until the crystalline silicate has formed, separating the.latter from the mother liquor and calcining it. In the aqueous mixture from which the silicates are 10 prepared, the various compounds should be present in the following molar ratios, expressed - with the exception of the amines. - in moles of the oxides: M20 : Si02 = 0.01 - 0.35, R1R2R3N : Si02 = 0.04 - 2.0, Si02 : Fe203 = 50 - 400, and H20 : Si02 =5-65.

An investigation carried out by the Applicant into the application of the above-mentioned catalyst 15 mixtures for the preparation of aromatic hydrocarbon mixtures from H2/C0 mixtures, has shown that the presence of aluminium in the crystalline iron silicates has a great influence upon the stability of the catalyst mixtures. The catalyst^ mixtures have been 20 found to have an exceptionally high stability, when the crystalline iron silicate present therein contains such a quantity of aluminium that in the formula 4 representing the composition of the silicate expressed in moles of the oxides the SiC^/A^O^ molar ratio is lower than 2000.

In the present patent application the term 5 "crystalline iron silicate" relates both to crystalline silicates which comprise only iron as the tri-valent metal and to crystalline silicates which, in addition to iron, comprise aluminium, provided that in the formula which represents the composition of 10 the silicate expressed in moles of the oxides the Pe20^/Al20^ molar ratio is higher than 1.0. The aluminium-containing crystalline iron silicates are prepared starting from an aqueous mixture which, in addition to the aforementioned compounds, contains 15 one or more aluminium compounds. The quantity of aluminium compounds present in the aqueous mixture should be such that the Si02/Al20-^ molar ratio is 50 - 4000. The preparation of aluminium-containing crystalline iron silicates as mentioned hereinabove, 20 starting from an aqueous mixture containing one or more amines of the general formula R^f^R-jN and one or more silicon compounds having a high Si02 content, is. new.

The present patent application therefore relates 25 to a process for the preparation of crystalline iron silicates, characterized in that, after one hour's. 201367 calcination in air at 500°C, they have the following properties: a) thermally stable up to a temperature of at least 600°C; 5b) an X-ray powder diffraction pattern in which the strongest lines are the four lines listed in Table A, and c) in the formula which represents the composition of the silicate expressed in moles of the oxides, 10 the Si02/Fe20^ molar ratio is 75-300, the Si02/Al20-j molar ratio is below 2000 and the Fe20^/Al20^ molar ratio is higher than 1.0. The preparation is carried out by maintaining an aqueous mixture comprising the following com-15 pounds: one or more compounds of an alkali metal(M), one or more amines of the general formula R^RgR^N, one or more silicon compounds having a high SiO^ content, one or more compounds in which iron is present in the trivalent form and one or more aluminium 20 compounds, in which mixture the various compounds are present in the following molar ratios, expressed -with the exception of the amines - in moles, of the oxides: 201 6 m2O Si02 Si02 h2o r1R2R3N Si02 = 0.01 - 0.35, Si02 = 0.04 - 2.0, Pe203 = 50 - 400, A1203 = 50 - 4000, and Si02 =5-65 at an elevated temperature until the crystalline silicate has formed and subsequently separating the crystalline silicate from the mother liquid and calcining it. Preferably, the H20/Si02 molar ratio 5 in the aqueous mixture is below 0.12.

The silicates prepared according to the invention are defined, among other things, by the X-ray powder diffraction pattern that they show after one hour's calcination in air at 500°C. In this pattern 10 the strongest lines should be the four lines listed in Table A. The complete X-ray powder diffraction pattern of a typical example of a silicate prepared according to the invention is given in Table B.

~ Dt 367 7 TABLE B d (8) Eel. int. d(8) Rel int 11.1 100 3-84 (D) 57 .0 (D) 70 3.70 (D) 31 8.93 1 3-63 16 7.99 1 3.47 1 7.42 2 3.43 6.68 7 3.34 2 6.35 11 3-30 .97 17 3.25 1 .70 7 3.05 8 .56 2.98 11 .35 2 2 .96 3 4.98 (D) 6 2.86 2 4.60 4 2.73 2 4.35 2 .60 2 4.25 7 2.48 3 4.07 2 2.40 2 4.00 4 (D) = doublet The prepatation of the silicates may be carried out at an atmospheric pressure as well as at an elevated pressure. If the reaction temperatures used lie above the boiling point of the mixture, the reaction is preferably carried out in an autoclave under autogenous pressure. The silicates are preferably prepared by maintaining the mixture for at least four hours at a temperature between 90 and 300°C and in particular at a temperature between 125 and 175°C. After the formation 5 of the silicates3 the crystals are separated from the mother liquor, for instance by filtration, decantation or centrifugation. The mass of crystals is then washed with water and finally dried and calcined.

As examples of suitable compounds that can be 10 used in the preparation of the silicates according to the invention may be mentioned nitrates, carbonates, hydroxides and oxides of alkali metals; amorphous solid silicas, silica sols, silica gels and silicic acid; oxides, hydroxides, normal salts and complex 15 salts of trivalent iron; linear and branched alkyl-amines. In the preparation of silicates according to the invention the starting mixture is preferably an aqueous mixture in which M is present in a sodium compound and R^F^R^N is a linear primary alkylamine 20 having 3"5 carbon atoms in the alkyl group, in particular n-butylamine.

As regards aluminium which, in the preparation of the crystalline iron silicates according to the invention, should be present in the aqueous, mixture, 2 5 the following may be noted. The silicon compounds with a high Si02 content eligible from the economical 2 013 6 point of view for the preparation on a technical scale of crystalline iron silicates according to the invention, usually contain a small proportion of aluminium as an impurity. At least part of this 5 aluminium is found in the iron silicate prepared.

This means that the use of such silicon compounds as the starting material results in crystalline iron silicates in which the. formula representing the composition of the silicate expressed in moles of the 10 oxides, in addition to Si02 and Fe^^, also contains Al^O^. However, the Si02/Al203 molar ratio is usually considerably higher than 2000. For instance, from silicon compounds with a normal aluminium contamination of 50-100 ppmw as the starting material, 15 crystalline iron silicates are obtained having a Si02/Al203 molar ratio of 5000-20,000. Regarding the incorporation of aluminium into the aqueous mixtures from which the crystalline iron silicates are prepared according to the invention there are, 20 basically, two possibilities. The starting mixture may be an aqueous mixture comprising a silicon compound which is contaminated with aluminium to such an extent that a crystalline iron silicate is obtained having the desired Si02/Al203 molar ratio below 2000. 25 For instance, from silicon compounds with a high aluminium contamination - of about 1000 ppmw - as 2 013 6 7 the starting material, crystalline iron silicates aire obtained having a SiC^/A^O^ molar ratio of 500-1000. The aqueous mixture may also be made to contain such a proportion of one or more aluminium compounds that, 5 while any quantity of aluminium already present in the silicon compound used is taken account of, a crystalline silicate is obtained having the desired Si02/Al203 molar ratio below 2000. Examples of suitable aluminium compounds which, in the preparation of the crystalline 10 iron silicates, may be incorporated into the aqueous mixture include aluminium hydroxide, aluminium sulphate, sodium aluminate and amorphous alumina.

Silicates prepared according to the invention may be used, among other things, as adsorbing agents 15 and extracting agents, as drying agents, as ion exchangers and as catalysts or catalyst carriers for use in a variety of catalytic processes, in particular the catalytic preparation of aromatic hydrocarbons from acyclic compounds.

If the silicates prepared according to the in vention are to be used as catalysts or catalyst carriers, the alkali metal content of these silicates should preferably be reduced beforehand to less .than 0.1^' and in particular to less than 0.01$w. The reduction 25 of the alkali metal content of the silicates may very suitably be carried out by contacting the silicates c=^, <z\ {2 '*> 'i ' 11 once or several times with an aqueous solution containing ammonium ions. The NH^+ silicates thus obtained may be calcined to form the H+ silicates.

When the crystalline iron silicates are used as 5 catalysts they may, if desired, be combined with a binder material, such. as. bentonite or kaoline.

As explained hereinabove, the silicates prepared according to the invention find an important application in catalyst mixtures to be used for the 1 10 preparation of an aromatic hydrocarbon mixture from a H2/CQ mixture. H^/CO mixtures may be prepared by steam gasification of a carbon-containing material. Examples of such materials are brown coal, anthracite, coke, crude mineral oil and fractions thereof and 15 also oils obtained from tar sand and bituminous shale. The steam gasification is preferably carried out at a temperature between 900 and 1500°C and a pressure between 10 and 50 bar. For the preparation of the aromatic hydrocarbon mixture the starting material 20 is preferably a H2/C0 mixture with a H2/C0 molar ratio between 0.25 and 1.0. The preparation of the aromatic hydrocarbon mixture from a H2/C0 mixture using a catalyst mixture comprising a crystalline iron silicate prepared according to the invention, is 25 preferably carried out at a temperature of from 200-500°C and in particular of from 300-450°C, a ^ f r~': A " '•*-■3 '' ' J , 12 pressure of from 1-150 bar and in particular of from 5-100 bar and a space velocity of from 50-5000 and in particular of from J00-3000 N1 gas/1 catalyst/hour. The two catalysts present in the catalyst mixture 5 used in the preparation of the aromatic hydrocarbon mixture from a ^/CO mixture will for the sake of brevity hereinafter be referred to as catalysts X and Y. Catalyst X is the catalyst capable of catalyzing the conversion of a Hg/CO mixture into oxygen-contain-10 ing organic compounds and catalyst Y is the crystalline iron silicate prepared according to the invention. For use as catalysts X preference is given to catalysts capable of converting a I^/CO mixture into substantially methanol and/or dimethyl ether. 15 If it is the object to prepare a product substantially consisting of hydrocarbons boiling in the gasoline range, the catalyst X used may very suitably be a catalyst which comprises zinc together with chromium. When such a catalyst is used, it is preferably chosen 20 to be a catalyst in which the atomic percentage of zinc, calculated on the sum of zinc and chromium, is at least 60% and in particular 60-80$. If the object is to prepare not only hydrocarbons boiling in the gasoline range, but also a fuel gas with a high 25 calorific value, the catalyst X used may very suitably be a catalyst comprising zinc together with 201367 13 copper. Preference is given .to. the use of a catalyst mixture which, per part by volume of catalyst Y, comprises 1-5 pbv of catalyst X.

The conversion described hereinabove using a 5 mixture of a crystalline iron silicate prepared according to the invention and a catalyst capable of catalyzing the conversion of a H^/CO mixture into oxygen-containing organic compounds, can very suitably be carried out as the first step of a two-step 10 process for the conversion of E^/CO mixtures into hydrocarbon mixtures. In this case carbon monoxide and hydrogen present in the reaction product from the first step are contacted in a second step, if desired, together with other components of this reaction product, 15 with a catalyst comprising one or more metal components having catalytic activity for the conversion of a H2/C0 mixture into paraffinic hydrocarbons, which metal components have been chosen from the group formed by cobalt, nickel and ruthenium, care being taken that the 20 feed for the second step has a E^/CO molar ratio of 1.75-2.25.

The conversion described hereinabove, using a mixture of a crystalline iron silicate prepared according to the invention and a catalyst capable of 2 5 catalyzing the conversion of a H2/C0 mixture into oxygen-containing organic compounds, can very suit- 0 136 ■14. ably be used as the first step of a three-stage process for preparing, inter alia, middle distillates from a H^/CO mixture. In this case carbon monoxide and hydrogen present in the reaction product from the 5 first step are contacted in a second step, if desired, together with other components of this reaction product, with a cobalt catalyst comprising zirconium, titanium or chromium as promoter, care being taken that the feed for the second step has a I^/CO molar ratio of 10 1.75-2.25. An example of a suitable catalyst for use in the second step is a catalyst which comprises 10-40 pbw of cobalt and 0.2 5-5 pbw of zirconium, titanium or chromium per 100 pbw of silica and has been prepared by impregnation of a silica carrier with one or more 15 aqueous solutions of salts of cobalt and zirconium, titanium or chromium, followed by drying of the composition, calcination at 350-700°C and reduction at 200-350°C. At least that part of the reaction product from the second step whose initial boiling 20 point lies above the final boiling point of the heaviest middle distillate desired as end product, is subjected in a third step, to a catalytic hydro-treatment .

The invention is; .now. illustrated with the aid of 25 the following example.

EXAMPLE Three crystalline iron silicates (silicates 1-3) were prepared from aqueous mixtures of NaOH, C^H^NI^, t 0 t 3 © amorphous silica I. (for silicates 2 and 3) or amorphous silica II (for silicate i) and, optionally, amorphous alumina (for silicate 3). Further, two crystalline aluminium silicates: (silicates 4 and 5) were prepared 5 from aqueous mixtures of NaOH, C^H^NHg, amorphous silica I and amorphous alumina. The preparation was carried out by heating the aqueous mixtures in an autoclave with stirring and under autogenous pressure for 120 hours at 150°C. After cooling of the reaction 10 mixtures the silicates formed were filtered off, washed with water until the pH of the wash water was about 8, and dried at 120°C. After one hour's calcination in air at 500°C, silicates 1-5 had the following properties: a) thermally stable up to a temperature of at least 800°C, b) an X-ray powder diffraction pattern substantially corresponding to that given in Table B, and c) a value of the SiOg/E^O^ and Si02/Al203 molar 20 ratios as stated in Table C. *6 2 013 6 7 16 TABLE C Silicate SIC^/E^O^ SiC^/AlpO^ No. molar ratio molar ratio 1 108 10000 2 115 2570 3 130 560 4 - 540 - 300 Amorphous silica I. used in the preparation of silicates 2-5 comprised 280 ppmw of aluminium and, after drying at 120°C and calcination at 500°C?; yielded a product consisting of 99«9$w of Si02> Amorphous 5 silica II used in the preparation of silicate 1 comprised 70 ppmw of aluminium and, after drying at 120°C and calcination at 500°C, yielded a product consisting of 99.7$w of Si02.

The molar composition of the aqueous mixtures from 10 which silicates 1-5 were prepared may be rendered as follows: 1.0 Na20.10 C^NI^. x Fe^. y Al20j.25 Si02.450 H20, where x and y have the values given in Table D. 17 table d Silicate . No.. . x y 1 0.20 0.002 2 0.20 0.008 3 0.20 0.041 4 / - 0.041 - 0.075 • From silicates 1-5 were prepared silicates 6-10, respectively, by boiling silicates 1-5 with a 1.0 molar NH^NO^ solution, washing with water, boiling again with a 1.0 molar NH^NO^ solution, and washing, 5 drying at 120°C and calcination at 500°C. Five catalyst mixtures (catalyst mixtures A-E) were subsequently prepared by mixing a ZnO-C^O^ composition with each of silicates 6-10. The atomic Zn percentage of the ZnO-C^O^ composition, calculated on the sum 10 of Zn and Cr, was 10%. All the catalyst mixtures comprised 10 pbw of the ZnO-C^O^ composition per pbw of silicate.

Catalyst mixtures: A-E were tested for the preparation of an aromatic hydrocarbon mixture from 15 a E^/CO mixture. The test was carried out in a 50-ml reactor containing a fixed catalyst bed of 7.5 ml 7 P <?■ -7 fiL f 18 volume. In. five experiments, a H^/CO mixture, having a H2/C0 molar ratio of 0.5 was passed over each of catalyst mixtures A-E at a temperature of 375°C> a pressure of 60 bar and a space velocity of -1 -1 1000 Nl.l .h . All these experiments yielded a product the C^+ fraction of which consisted more than 30$w of aromatics. Furth-er results of the experiments are given in Table E. • •• • • •• • table e Experiment No.

Catalyst mixt- • ure No.

Silicate No.

Synthesis gas conversion. %v Stability expressed as difference between C^0 and C100 .

C3+-select-ivity, averaged over 100 h, #w C,- + -select-5 ivity, averaged over 100 h, %vi after 10 h <C10> after 10 h (C100^ 1 I A 6 62 57 93 80 2 B ; 7 62 58 4 . 93 79 3 C 8 63 62 1 95 78 4 D 9 52 32 94 78 E 60 50 95 74 <Qo< 'Uil 7/7 tiu I _•' 6 / Of the silicates listed in Table C only crystalline iron silicate 3 was prepared according to the invention. Crystalline iron silicates 1 and 2 and crystalline aluminium silicates 4 and 5 fall outside 5 the scope of the invention. They have been included in the present patent specificatian for comparison. Of the experiments, listed in Table E only Experiment 3 was carried out using a catalyst comprising a crystalline iron silicate prepared according to the in-10 vention. Experiments 1, 2, H and 5 fall outside the scope of the invention. They have been included in the patent specif ication for comparison. On the results given in Table E the following may be remarked: a) The results of Experiments 1 and 2 show that 15 catalyst mixtures comprising a crystalline b) The result of Experiment 3 shows that raising the Al-content of the crystalline iron silicate to an Si02/Al203 molar ratio < 2000, yields a very substantial improvement of the stability, while iron silicate having a low aluminium content (Si02/Al203 molar ratio > 2000), show a high initial activity and a very high selectivity.

The stability of these catalyst mixtures remains susceptible of improvement. the high initial activity and the very high selectivity are preserved. 1 '

Claims (12)

21 c) The catalyst mixture, used in Experiment 4 .comprised a crystalline aluminium silicate, in which the SiC^/A^O^' molar ratio was chosen such- that it corresponded with, that of. the crystalline iron silicate in the catalyst mixture used in Experiment 3. The results: of Experiment 4 show, that this catalyst mixture, has a low initial activity and a very low stability. d) The catalyst mixture used in Experiment 5 Comprised a crystalline aluminium silicate in which the SiC^/A^O^ molar ratio was chosen such, that with this catalyst mixture an initial activity could be attained corresponding to that of th.e catalyst mixture used in Experiment 3. The results of Experiment 5 show that the stability of the catalyst mixture used remains very low. Comparison of the results of Experiments 5 and 4 shows that reduction of the SiC^/A^O^ molar ratio of the crystalline aluminium silicate leads to a considerable reduction in the C,- + select-ivity of the catalyst mixture. WHAT #VVE CLAIM 22. C|L A I M S

1. A proceas for the preparation of crystalline iron silicates which, after one hour's, calcination in air at 500°C, have the following properties: a) thermally stable up to a temperature of at 5 least 600°C; b) an X-ray powder diffraction pattern in which the four lines listed in Table A are the strongest lines: TABLE A d(8) Relative intens.ity 11.1+0.2 VS 10.0+0.2 VS 3.84 + 0.07 S 3-72 + 0.06 S in which the letters, used have the following 10 meanings: VS = very strong; S = strong, and c) in the formula which, represents, the. composition expressed in moles of the oxides, the Si02/Fe20j molar ratio is 75^300, the SiO^/Ai^o^ molar ratio is. lower than 2000 and the Fe20^/Al20^ molar ratio is higher than 1.0, characterized in that 15 an aqueous mixture comprising the following com pounds: one or more compounds: of an alkali metal (M), one or more amines of the general J ^ {<J / 23 . formula R^RgR^N, where R^ is an alkyl group and R2 and R^ are an alkyl group or a hydrogen atom, one or more silicon compounds which, after drying at 120°C and calcination at 500°C, yield a 5 product having an S.iC>2 content of more than 90$w, one or more compounds, in which iron occurs in the trivalent form and one or more aluminium compounds, in which mixture the compounds are present in the following molar ratios, expressed 10 - with the exception of the amines - in moles of the oxides: M20 : Si02 = 0.01-0.35, R1R2R3N : Si02 = 0.04-2.0, Si02 : Pe203 = 50-400, Si02 : A1203 = 50-4000, and H20 : Si02 = 5-65, is maintained at an elevated temperature until the crystalline silicate has formed and the latter is subsequently separated from the mother 15 liquor and calcined.

2. A process as claimed in claim 1, characterized in that the M20/Si02 molar ratio of the aqueous mixture is lower than 0.12.

3. A process as claimed in claim 1 or 2, characterized 20 in that the alkali metal compound used is a sodium compound and the R^R-pR^N compound used is n-hutylamine. WstP 24

4 . A process as claimed in any one of claims 1-3, characterized in that the aqueous mixture is kept for at * least 4 hours at a temperature between 90 and 300°C.

5. A process as claimed in any one of claims 1-4, 5 characterized in that the required quantity of aluminium has been introduced into the aqueous mixture by the use of a heavily aluminium-contaminated silicon compound and/or by the addition of a separate aluminium compound. 10

6. A process as claimed in claim 1, substantially as hereinbefore described with special reference to the Example. •' • - • v <w

7. Crystalline iron silicates prepared according to a process as claimed in any one of claims 1-6.

8. A process for carrying out catalytic processes, characterized in that an aromatic hydrocarbon mixture is prepared by contacting a I^/CO mixture with a mixture of two catalysts, one of which is capable of catalyzing the conversion of a-I^/CO mixture into oxygen-containing organic compounds, the other being a crystalline iron silicate as claimed in claim 7. \ '' ^O' J>L'] 201367 25

9. A process as. claimed in claim 8, char.acteri.zed in that as the catalyst capable of catalyzing the conversion of a I^/CO mixture into oxygen-containing organic compounds, a composition is used which comprises zinc together with chromium or copper.

10. A process as claimed in claim 8 or characterized in that the Hg/CO mixture has a Hg/CO molar ratio between 0.25 and 1.0.

11. 1 A process as claimed in claim 8,1 substantially as hereinbefore described with special reference to the Example.

12. Hydrocarbon mixtures prepared according to a process as claimed in any one of claims 8-11. - UATED THIS A. J. PARK & SON