NL8105168A - Acid treatment of crystalline iron silicate materials - to improve catalytic properties, esp. for aromatic hydrocarbon synthesis - Google Patents

Abstract

A process is claimed for improving the catalytic properties of crystalline Fe silicates (I) which have the following characteristics after calcination in air at 500 deg.C for 1 hr: (a) thermally stable to temps. of at least 600 deg.C; (b) X-ray powder diffraction with strongest lines at d=11.1(+-)0.2 (vs), 10.0(+-)0.2 (vs), 3.84(+-)0.07 (s) and 3.72(+-)0.06 (s) Angstroms; (c) SiO2/Al2O3 molar ratio above 10: and (d) alkali metal content 200 ppm or less. The process comprises treating (I) with an acid one or more times. The prods. are capable of converting non-aromatic organic cpds. to aromatic hydrocarbons. A specifically claimed process comprises contacting synthesis gas (pref. with an H2/CO molar ratio of 0.25-1.0) with acid-treated (I) and a catalyst/pref. contg. Zn and Co) capable of converting synthesis gas to oxygenates.

Description

*, i

g 5590 NET

TREATMENT OF CRYSTALLINE SILICATES

The invention relates to a method for improving the catalytic properties of crystalline iron silicates.

Recently, new crystalline metal silicates of special structure have been synthesized, which have proved useful as catalysts for many chemical converters. For example, non-aromatic organic compounds can be converted into aromatic hydrocarbons using these silicates as catalysts. The respective crystalline metal silicates are characterized in that after an hour of calcination in air at 500 ° C, they have the following properties: a) thermally stable to a temperature of at least 600 ° C, 15 b) an X-ray powder diffraction pattern which shows the four lines shown in Table A as strongest lines contains: 8105168 V ί% -2-

Table A

Relative d (A) intensity

11.1 +0.2 ZS

10.0 + 0.2 ZS

. 3.84 + 0.07 S

3.72 + 0.06 S

in which the letters used have the following meaning: ZS = very strong, S * strong, ¢) in the formula which represents the composition of the silicate expressed in moles of the oxides and in which, in addition to SIO2, an oxide of a trivalent metal A selected from iron and aluminum is 5 SiO2 / A203 mol. ratio more than 10, and d) an alkali metal content of the highest 200 gpm.

In this patent application a crystalline silicate with a thermal stability of at least t ° C is understood to mean a silicate whose x-ray powder diffraction pattern does not substantially change when heated to a temperature of t ° C.

The crystalline metal silicates can be prepared from an aqueous mixture containing the following compounds: one or more silicon compounds, one or more compounds containing a monovalent organic cation (R) or from which such cation is produced during the preparation of the silicate is formed, one or more compounds containing either trivalent iron or aluminum and optionally one or more compounds of an alkali metal (M). The preparation is carried out by keeping the mixture at an elevated temperature until the silicate is formed and then separating the crystals of the silicate from the mother liquor and washing, drying and calcining the crystals. In the aqueous mixture from which the silicates are prepared, the different compounds should be present in the following proportions expressed in moles of the oxides: 5 M20 ϊ SiO2 <0.35, R20: SiO2 »0.01 - 0.5,

SiO 2: A 2 O 3> 10, and H 2 O: SiO 2> 5-65.

If the preparation of the crystalline silicates 10 is based on an aqueous mixture in which dSn or more alkali metal compounds are present, crystalline silicates containing alkali metal are obtained. Depending on the concentration of the alkali metal compounds in the aqueous mixture, crystalline silicates can be obtained which contain more than 1% by weight of the alkali metal. Since the presence of alkali metal in the crystalline silicates has an adverse effect on their catalytic properties, it is common practice to lower this content in crystalline silicates with a relatively high alkali metal content before using these silicates as catalysts. A reduction of the alkali metal content to about 200 gpm is sufficient for this.

It has been found that a further reduction of the alkali metal content has virtually no influence on the catalytic properties of the silicate. The reduction of the alkali metal content of crystalline silicates intended for use as catalysts is in practice effected by treating the silicates one or more times with a solution of an ammonium compound.

Here, alkali metal ions are exchanged for NH4 + ions and the silicate is converted into the NH4 + form.

The NH4 + form of the silicate is converted into the H * form by calcination.

8105168 -4-

Although the catalytic properties of the above-described crystalline iron and aluminum silicates when used as catalysts are already at a very acceptable and mutually comparable level for various chemical conversions, there is still a need for a further improvement of one or a measure of these properties .

It has been found that the catalytic properties of the crystalline iron silicates can be considerably improved by treating them once or several times with an acid. For example, in the conversion of oxygenated organic compounds to an aromatic hydrocarbon mixture using a crystalline iron silicate as described above as a catalyst, it has been found that the activity and selectivity of the catalyst for this conversion is greatly improved by treatment with an acid. The treatment of the above crystalline iron silicates with an acid is new.

The present patent application therefore relates to a method for improving the catalytic properties of crystalline iron silicates, wherein crystalline iron silicates having the properties mentioned under a) -d) are treated with an acid one or more times.

Although the above-mentioned crystalline aluminum silicates are very closely related to the crystalline iron silicates in terms of their preparation, structure and catalytic properties, it has surprisingly been found that while the acid treatment of the crystalline iron silicates provides a strong improvement in the catalytic properties. achieved, a corresponding treatment with the crystalline aluminum silicates does not affect the catalytic properties. During the investigation it has been found that when an acid treatment is applied to crystalline iron or aluminum silicates with an alkali metal content of not more than 200 gppm, a slight drop in the alkali metal content may occur. Since, as has been established experimentally, this slight decrease in the alkali metal content has virtually no influence on the catalytic properties of the crystalline silicates, the strong improvement of the catalytic properties of the crystalline iron silicates which occurs during acid treatment cannot be explained by these possibly occurring decrease in the alkaline language-10 content.

The crystalline iron silicates to which the acid treatment according to the invention is applied are defined, inter alia, on the basis of the X-ray powder diffraction pattern that they display after calcination in air at 500 ° C for an hour.

This should include the four lines listed in Table A as the strongest lines. The complete X-ray powder diffraction pattern of a typical example of a crystalline iron silicate to which the acid treatment according to the invention can be applied is shown in Table B. 8103168

j V

-6-

Table B

d (A) Rel. int. d (A) Rel. int.

11.1 100 3.84 (D) 57 10.0 (D) 70 3.70 (0) 31 8.93 1 3.63 16 7.99 1 3.47 1 7.42 2 3.43 5 6.68 7 3.34 2 6.35 11 3.30 5 5.97 17 3.25 1 5.70 7 3.05 8 5.56 10 2.98 11 5.35 2 2.96 3 4.98 03) 6 2.86 2 4.60 4 2.73 2 4.35 5 2.60 2 4.25 7 2.48 3 4.07 2 2.40 2 4.00 4 03) = * doublet

The crystalline iron silicates to which the acid treatment according to the invention is applied have an SiO 2 / Fe 2 O 3 mol ratio which is more than 10.

The acid treatment is preferably applied to crystalline iron silicates with a SiO 2 / Fe 2 O 3 mol. ratio of less than 1000 and in particular between 20 and 300.

The preparation of the present crystalline iron silicates can in principle take place from aqueous base mixtures to which no or only very little alkali metal compound has been added. In view of the small amounts of alkali metal which usually occur as contamination in the reactants, as a rule, crystalline iron silicates containing an alkali metal content of at most 200 gppm and on which the acid treatment according to the invention 2 can be readily prepared can be prepared. applied. As a rule, however, the preparation of the crystalline iron silicates is based on an aqueous base mixture to which a substantial amount of one or more alkali metal compounds has been added and crystalline silicates are obtained.

S

which contain considerably more than 200 gppm of alkali metal. For these silicates, the alkali metal content must be reduced to a value of at most 200 gppm before successfully applying the acid treatment according to the invention.

As already noted above, the reduction of the alkali metal content of crystalline iron silicates to a value of up to 200 gpm can very suitably be effected by treating the silicates with a solution of an ammonium compound in which the 2q alkali metal ions are exchanged for ammonium ions. Both organic and inorganic ammonium compounds are suitable for this purpose. Preferably, the treatment with an ammonium compound is carried out with an aqueous solution of an inorganic ammonium compound such as NH4CI, (NH4) 3PO4, (NH4) 2SO4 or NH4NO3. The use of an aqueous solution of NH4NO3 is particularly preferred. The concentration of the ammonium compound in the solution can vary within wide limits. Preferably, a solution is used with a normality of 0.5-5.

The temperature in the treatment with the solution of an ammonium compound can also vary within mime limits. The treatment can be carried out at room temperature, but preference is given to treatment at an elevated temperature, for example at the boiling point 8105168-8 of the solution. The duration of the treatment with an ammonium compound solution depends, inter alia, on the alkali metal content of the silicate to be treated, the concentration of the ammonium compound in the solution, the treatment temperature and the contact efficiency.

If desired, several treatments, each with a fresh solution of an ammonium compound, can be carried out. If desired, the silicate can be dried and calcined between treatments. The treatment of the crystalline iron silicate with a solution of an ammonium compound should be continued until the alkali metal content has fallen to a value of at most 200 gpm.

Both the organic and inorganic acids are suitable for the acid treatment according to the invention of the crystalline iron silicates with a low alkali metal content. Preferably, the acid treatment is carried out with an aqueous solution of a strong mineral acid such as H3PQ4, H2SO4, HNO3 or HCl. The use of an aqueous solution of HCl is particularly preferred. The concentration of the aqueous solution of the acid can vary within wide limits. Preferably a solution is used with a normality of 0.1-2. The temperature in the acid treatment can also vary within wide limits. The treatment can be carried out at an elevated temperature, but preference is given for a treatment at room temperature. The duration of the acid treatment. is usually at least 2 hours. The acid treatment is generally continued until veriere acid treatment no longer significantly improves the catalytic properties of the silicate. Usually the acid treatment does not take more than 100 hours. Very favorable results can be obtained with an acid treatment for 5-50 hours. As with the treatment with a solution of an 8105168 ammonium compound, with the treatment with an acid it is possible that this treatment can be repeated one or more times, if desired, each time with fresh acid and that, if desired, the silicate can be dried and calcined between the acid treatments.

The crystalline iron silicates to which an acid treatment according to the invention has been applied are useful as catalysts for many chemical conversions. A very important application is its use as a catalyst in the conversion of non-aromatic organic compounds to aromatic hydrocarbons. It has been found that, independently of the number of carbon atoms in the organic compound used as feed, aromatic hydrocarbon mixtures are obtained in which the aromatics essentially contain less than 12 carbon atoms. Examples of suitable non-aromatic organic compounds which can be converted into aromatic hydrocarbons using the crystalline iron silicates as catalysts are oxygen-containing organic compounds such as methanol and dimethyl ether, straight-chain paraffins such as propane, butane and pentane, branched paraffins such as isobutane and iso-pentane and mono-olefins such as propylene and butene. Methanol and dimethyl ether have been found to be very suitable to serve as a feed for the above-mentioned flavoring process.

The preparation of an aromatic hydrocarbon mixture from non-aromatic organic compounds is preferably applied to non-aromatic organic compounds obtained by reaction of a mixture of carbon monoxide and hydrogen. The conversion of an H 2 / CO mixture into an aromatic hydrocarbon mixture using a crystalline iron silicate subjected to an acid treatment according to the invention can be carried out in one step or two steps. At 8105168-10 the two-step process, an H 2 / CO mixture is contacted with a catalyst containing one or more metal components with catalytic activity for the conversion of an H 2 / CO mixture into non-aromatic organic compounds. the second step, the product thus obtained is converted into an aromatic hydrocarbon mixture by contacting it under crystallization conditions with the crystalline iron silicate. or more metal components with catalytic activity for the conversion of an H2 / CO mixture into non-aromatic organic compounds The process is preferably carried out as a one-step process using a mixture of two catalysts, one of which (catalyst X) has the power has the ability to convert an H2 / CO mixture to an essentially oxygen-containing organic compounds and the other (Catalyst Y) is the crystalline iron silicate. Suitable conditions for carrying out the process are a temperature of 200-500 ° C and. in particular from 300-450 ° C, a pressure of 1-150 bar and in particular from 5-100 bar and a spatial flow rate of 50-5000 and in particular from 300-3000 HI gas / 1 catalyst / hour. Preferably, as feed for the one-step flavoring process, an H2 / CO mixture with an H2 / CO mol is used. ratio between 0.25 and 10. Such H2 / CO mixtures can very suitably be prepared by steam gasification of a carbonaceous material such as coal, at a temperature of 900-1500 ° C and a pressure of 10-50 bar. Catalysts which are capable of converting an H 2 / CO mixture into mainly methanol and / or dimethyl ether are preferably used as catalysts X in the above-mentioned catalyst mixtures. Very suitable catalysts of this type are compositions containing zinc together with chromium. When using such a catalyst, one is preferably chosen in which the atomic percentage of zinc, based on the sum of zinc and chromium, is at least 60% and in particular 60-80%. Preferably, a catalyst mixture is used which contains, per volume part of catalyst Y, 1-5 volume parts of catalyst X *

The above-described conversion using an IQ mixture of a catalyst X with a catalyst Y can very suitably be used as the first step of a two-step process for the conversion of H 2 / CO mixtures into hydrocarbon mixtures. In this case, carbon monoxide and hydrogen present in the reaction product from the first step, if desired together with other components of this reaction product, are contacted in a second step with a catalyst containing one or more metal components with catalytic activity for the conversion of an H 2 / CO mixture to paraffinic hydrocarbons, which metal components are selected from the group consisting of cobalt, nickel and ruthenium, care must be taken that the feed for the second step is an H 2 / CO mole. ratio of 1.75-2.25.

The above-described reaction using a mixture of a catalyst X with a catalyst Y can furthermore very suitably be used as the first step of a three-step process for the preparation of, inter alia, middle distillates from an H2 / CO mixture. In this case, carbon monoxide and hydrogen contained in the reaction product of the first step, optionally together with other components of this reaction product, are contacted in a second step with a cobalt catalyst containing zirconium, titanium or chromium to promote Ensure that the feed for the second step 8105168 -12- ν 'V- is an H2 / CO mol. ratio of 1.75-2.25. Of the reaction product of the second step, at least the part whose initial boiling point is above the final boiling point of the heaviest intermediate distillate desired as end product, is subjected to a catalytic hydrotreatment in a third step.

The invention is now illustrated by the following example. .

Example 10 Three crystalline silicates (silicates 1-3) were prepared by mixing mixtures of NaOH, (C3H7) 4NOH, amorphous silica as well as Fe (NO3) 3 or A1 (NO3) 3 in water in an autoclave under autogenous pressure for 24 hours 150 9C. After cooling the reaction mixtures, the resulting silicates were filtered off, washed with water until the pH of the washing water was about 8, dried at 120 ° C and calcined at 500 ° C. The silicates 1-3 had the following properties: a) thermally stable to a temperature of at least 20 800 ° C, b) a rattan powder diffraction pattern substantially corresponding to that stated in Table B, and c) a SiO 2 / Ve 2 O 3, respectively. SiO 2 / Al 2 O 3 mol. ratio as stated in table C.

Table C

Si02 / Fe203 S102 / A1203

Silicate No. mol, diff. mole, elev.

1 55 - 2 68 3 - 90 The molar composition of the aqueous mixtures from which the silicates 1-3 were prepared can be represented as follows: 8105168-13: a Na2O. b Fe2 O3c AI2O3. 4.5 [(G3H7> 4N] 20 · 25 SiO2 · 450 H2O in which a, b and c have the values shown in Table D.

Table D

Silate no. A b c 1 3 0.2 - 2 3 0.16 - 3 1 - 0.2 5 Starting from the silicates 1-3, resp. the silicates 1A-3A prepared by boiling the silicates 1-3 successively for 1 hour with a 1.0 molar ΝΟ4ΝΟ3 solution (10 ml solution per g silate), washing, drying at 120 ° C and calcining at 500 ° G. The silicates 10 1A-3A were each divided into three portions. Starting from the first aliquots of the silicates 1A-3A, resp. the silicates 1B-3B prepared by boiling the first portions of the silicates 1A-3A successively for 1 hour with a 1.0 molar NH4NO3 solution (10 ml solution 15 per g silate), washing, drying at 120eC and calcining at 500 ° C. Starting from the second portions of the silicates 1A-3A, resp. the silicates 1C-3C prepared by successively treating the second portions of the silicates 1A-3A for a certain time at room temperature with 0.5 N hydrochloric acid (10 ml per g silate), washing, drying at 120eC and calcining at 500eC. The sodium contents of the silicates as well as the duration of the HCl treatment are listed in Table E.

8105168 'if ^ -il-

Table E

Duration of the

Silicate no »Na content HCl treatment 1 1.2 wt% 1A 150 gpm IS 125 gpm 1C 130 gpm 15 hours 2 1.2 wt% 2A 100 gpm 2B 70 gpm ^ 2C 80 gpm 40 hours 3 1.1 wt .% 3A 90 gpm 3B 75 gpm 1 3C 80 gpm 30 hours

The silicates 1A-1C, 2A-2C and 3A-3C were tested as catalysts for the preparation of an aromatic hydrocarbon mixture from dimethyl ether. The test was carried out in a 50 ml reactor containing a fixed catalyst bed with a volume of 7.5 ml consisting of a mixture of 1 ml. of the respective silicate and 6.5 ml of al-alumina. In nine experiments, dimethyl ether was passed over the catalysts at a temperature of 375 ° C and a pressure of 3 bar. The space body throughput rate was 23 g / g silicate / hour in the experiments with the silicates 1A-1C and 2A-2C and 33 g / g silicate / hour in the experiments with the silicates 3A-3C. The results of these experiments are shown in Table F. The table shows: a) the activities (expressed in weight percent of dimethyl ether converted to hydrocarbons) after 1 hour and after 5 hours, and 8105168 * · *? ** -15- b) the C5 + selectivity (expressed in weight% of C5 + hydrocarbons on C] + hydrocarbons in product) after 1 hour.

In all experiments a product was obtained, of which the C5 + fraction consisted of more than 50% by weight of aromatics.

label F.

Experiment No. 123456789

Silicate No. ΙΑ IB '1C 2A 2B 2C 3A 3b 3C

Activity after 1 hour, wt% 74 75 98 65 66 85 75 76 76

Activity after 5 hours, wt.% 49 50 76 43 44 62 40 41 41 C5 + selectivity after 1 hour wt.% 76 76 80 74 74 78 76 76 77

Three catalyst mixtures (catalyst mixtures IIA-IIC) were prepared by mixing a ZnO-Cr 2 O 3 composition 10 with each of the silicates 2A-2C. The atomic Zn percentage of the Zn0-Cr203 composition based on the sum of Zn and Cr was 70%. The catalyst mixtures contain per wt. part silicate, 10 wt. parts of the Zn0-Cr203 composition. The catalyst mixtures IIA-IIC were tested for the preparation of an aromatic hydrocarbon mixture from an H2 / CO mixture. The test was carried out in a 50 ml reactor containing a fixed catalyst bed with a volume of 7.5 ml. In three experiments, an H2 / CO mixture was mixed with an H2 / CO mole. ratio 2Q of 0.5 at a temperature of 375 ° C, a pressure of 60 bar and a spatial throughput of 1000 Nl. l ~ 1h- * over each of the catalyst mixtures IIA-IIC. The results of these experiments are shown in Table G.

8105168 "* -16-

Table G

Experiment No. 10 11 12

Cat. mixture No. IIA XIB IIG

Silicate No. 2A 2B 2G

Conversion of the synthesis gas,% by volume after 10 hours 58 59 65 after 100 hours 54 55 61

Cr1 * selectivity, wt% after 10 hours 90 90 92 after 100 hours 90 90 92

Ctj + selectivity, yes; e.% After 10 hours 75 75 78 after 100 hours 75 75 78

Aromatics in C $ + fraction averaged over 100 hours, wt% 35 36 44

The following can be noted with the results listed in Tables E-G.

a) Of the silicates listed in Table E, only 5 silicates 1C and 2G were prepared according to the invention. The remaining silicates are outside the scope of the invention. They were incorporated in the patent application for comparison.

b) Of the experiments listed in Table F, only 10 experiments 3 and 6 were performed using a catalyst containing a silicate prepared according to the invention.

c) The favorable influence of the acid treatment according to the invention on the activity and selectivity of the crystalline iron silicates when used as catalysts for the conversion of dimethyl ether to an aromatic hydrocarbon mixture is evident in 8105168-17 * * results of experiments 1 and 3 and of experiments 4 and 6. When comparing the results of experiments 1 and 2 and of experiments 4 and 5 it is clear that the improvement of the catalytic properties of the crystalline iron silicates which occurs as due to the acid treatment, cannot be explained by the slight decrease in the Na content of the silicates causing the acid treatment. Comparison 10 of the results of Experiments 7 and 9 shows that a corresponding acid treatment of a closely related crystalline aluminum silicate does not affect the behavior of this silicate when used as a catalyst for the above conversion of dimethyl ether.

D) Of the experiments listed in Table G, only experiment 12 was performed using a catalyst mixture in which the silicate component was prepared according to the invention. The favorable influence of the acid treatment according to the invention on the activity and selectivity of the crystalline iron silicates when used as a catalyst component in catalyst mixtures for the conversion of synthesis gas to an aromatic hydrocarbon mixture, becomes clear when comparing the results of experiments 10 and 12.

E) When comparing the results of experiments 10 and 11, it again appears that the improvement of the catalytic properties of the crystalline iron silicates which occurs as a result of the acid treatment cannot be explained by the slight decrease in the 30 Na content of the silicates causing the acid treatment.

8105168

Claims (12)

10 Table A Relative d (A) intensity 11.1 +0.2 ZS 10.0 +0.2 ZS 3.84 + 0.07 S 3.72 + 0.06 S in which the letters used have the following meanings: ZS = very strong, S e strong, c) in the formula which represents the composition of the silicate expressed in moles of the oxides and in which, in addition to SiO2, an oxide of a trivalent metal A selected from iron and aluminum is SiO2 / A203 mol. ratio more than 10, and 8105168 <-19- ο * d) an alkali metal content not exceeding 200 gpm, treated one or more times with an acid * 2. Process according to claim 1, characterized in that the acid treatment is applied to a crystalline iron silicate of which the SiO2 / Fe2O3 mol. ratio between 20 and 300 parts. 3. Process according to claim 1 or 2, characterized in that the acid treatment is applied to a crystalline iron silicate whose alkali metal has been reduced to a value of at most 200 gpm by treatment with an ammonium compound. 4. Process according to any one of claims 1-3, characterized in that the acid treatment is carried out with an aqueous solution of a strong mineral acid for 2-100 hours. A method according to claim 4, characterized in that the acid treatment is carried out with an aqueous solution of a strong mineral acid with a normality of 0.1-2 for 5-50 hours. Process according to claim 4 or 5, characterized in that the acid treatment is carried out with an aqueous solution of HCl at room temperature. 7. Process for improving the catalytic properties of crystalline iron silicates substantially as described above and in particular with reference to the acid treatment of the silicates 1A and 2A in the example. 8. Crystalline iron silicates, the catalytic properties of which have been improved according to a method as described in claim 7. Process for carrying out catalytic ora settlements, characterized in that a catalyst is used which contains a crystalline iron silicate according to claim 8. 8105168 -20- 10. Process according to claim 9, characterized in that an aromatic hydrocarbon mixture is prepared by contacting an H2 / CO mixture with a mixture of two catalysts, one of which has the capacity to convert an H2 / CO mixture to to catalyze oxygen-containing organic compounds and the other is the crystalline iron silicate. 11. Process according to claim 10, characterized in that as a catalyst which has the ability to catalyze the conversion of a & 2 / CO mixture into oxygen-containing organic compounds, a composition is used which contains zinc together with chromium. Process according to claim 10 or 11, characterized in that the H2 / CO mixture is an H2 / CO mol. ratio 15 has between 0.25 and 10. Hydrocarbon mixtures prepared by a method as described in any one of claims 10-12. 8105168