Isomerisation catalyst preparation process

Abstract

A process for preparing an alkylaromatics isomerisation catalyst comprising at least 0.01% wt of platinum on a carrier comprising of from 1 to 9 wt % of ZSM-12 and inorganic binder, which process comprises treating the carrier with an impregnation solution comprising base and an anionic platinum complex which impregnation solution has a pH of from 5.5 to 8; and a process for the isomerisation of alkylaromatics with the help of catalyst thus obtained.

Claims

1. A process for preparing an alkylaromatics isomerization catalyst, comprising: mixing an amount of ZSM-12 zeolite with an amount of an alumina binder to form a mixture, wherein said ZSM-12 zeolite has an average crystal size in the range of from 30 to 70 nm, a surface area of more than 250 m.sup.2/g as measured by nitrogen adsorption, and crystallinity of greater than 94%, and wherein the alumina of said alumina binder has a nitrogen pore volume of at least 0.6 cc/g and an average pore diameter greater than 80 ; shaping said mixture into extrudates; without prior calcination of said extrudates, impregnating said extrudates with an impregnation solution comprising a base and an anionic platinum complex to provide impregnated extrudates, wherein said impregnation solution has a pH of from 5.5 to 8; drying said impregnated extrudates; and calcining the dried impregnated extrudates at a calcination temperature in the range of from 300 to 600 C. to provide said alkylaromatics isomerization catalyst; wherein said amount of ZSM-12 zeolite and said amount of said alumina binder are such as to provide said alkylaromatics isomerization catalyst that comprises from 1 to 9 wt % ZSM-12 zeolite and more than 50 wt % alumina binder, based on the total weight of said alkylaromatics isomerization catalyst; wherein the alkylaromatics isomerization catalyst provides an ethylbenzene conversion of at least 37% wt at a PXate of 95 wt %.

2. A process as claimed in claim 1 in which the base is a compound according to the formula (R.sub.1R.sub.2R.sub.3NH)OH in which the compounds R.sub.1, R.sub.2, R.sub.3 each independently are chosen from the group consisting of hydrogen and alkyl containing of from 1 to 6 carbon atoms.

3. A process as claimed in claim 1 in which the impregnation is carried out by contacting the extrudates with an excess of impregnation solution while stirring.

4. A process as claimed in claim 1 in which a silica to alumina molar ratio of the ZSM-12 is in the range of from 60 to 200.

5. A process as claimed in claim 1 in which the anionic platinum complex is a platinum chloride complex of the general formula X.sub.nPtCl.sub.m, wherein X is either ammonium or hydrogen, n is an integer of from 1 to 6, and m is an integer of from 4 to 8.

6. A process as claimed in claim 1, wherein the alumina binder is present in the alkylation isomerization catalyst in an amount of at least 90 wt %.

7. A process as claimed in claim 6, wherein the alumina binder further comprises an additional compound selected from the group consisting of silica, titania, zirconia, ceria and gallia.

8. A process as claimed in claim 7, wherein the alumina binder contains up to 50% wt of the additional compound.

9. A process as claimed in claim 8, wherein a silica-to-alumina molar ratio of the ZSM-12 zeolite is in the range of from 70 to 150.

10. A process as claimed in claim 5, wherein the platinum chloride complex is hexachloroplatinic acid.

11. A process as claimed in claim 10, wherein the alumina binder is present in the extrudates in an amount of more than 80 wt %.

12. A process as claimed in claim 11, wherein the alkylaromatics isomerization catalyst comprises from 1 to 7 wt % of the ZSM-12 zeolite.

13. A process as claimed in claim 12, wherein the alumina binder further comprises an additional compound selected from the group consisting of silica, titania, zirconia, ceria and gallia.

14. A process as claimed in claim 13, wherein the alumina binder contains up to 10% wt of the additional compound.

15. A process for preparing an alkylaromatics isomerization catalyst comprising: mixing an amount of ZSM-12 zeolite with an amount of an alumina binder to form a mixture, wherein said ZSM-12 zeolite has an average crystal size in the range of from 30 to 70 nm, a surface area of more than 250 m.sup.2/g as measured by nitrogen adsorption, and crystallinity of greater than 94%, and wherein the alumina of said alumina binder has a nitrogen pore volume of at least 0.6 cc/g and an average pore diameter greater than 80 ; shaping said mixture into preformed carrier particles; drying said preformed carrier particles; calcining the dried preformed carrier particles at a calcination temperature in the range of from 300 to 600 C. to provide dried and calcined preformed carrier particles; impregnating said dried and calcined preformed carrier particles with an impregnation solution comprising a base and an anionic platinum complex to provide impregnated preformed carrier particles, wherein said impregnation solution has a pH of from 5.5 to 8; drying said impregnated preformed carrier particles; and calcining the dried impregnated preformed carrier particles at a calcination temperature in the range of from 300 to 600 C. to provide said alkylaromatics isomerization catalyst; wherein said amount of ZSM-12 zeolite and said amount of said alumina binder are such as to provide said alkylaromatics isomerization catalyst that comprises from 1 to 9 wt % ZSM-12 zeolite and more than 50wt % alumina binder, based on the total weight of said alkylaromatics isomerization catalyst; wherein the alkylaromatics isomerization catalyst provides an ethylbenzene conversion of at least 37% wt at a PXate of 95 wt %.

16. A process as claimed in claim 15 in which the base is a compound according to the formula (R.sub.1R.sub.2R.sub.3NH)OH in which the compounds R.sub.1, R.sub.2, R.sub.3 each independently are chosen from the group consisting of hydrogen and alkyl containing of from 1 to 6 carbon atoms.

17. A process as claimed in claim 16 in which a silica to alumina molar ratio of the ZSM-12 zeolite is in the range of from 60 to 200.

18. A process as claimed in claim 17, wherein the anionic platinum complex is platinum chloride complex, and wherein the platinum chloride complex is hexachloroplatinic acid.

19. A process as claimed in claim 18, wherein the alumina binder is present in carrier in an amount of more than 80 wt %.

20. A process as claimed in claim 19, wherein the alkylaromatics isomerization catalyst comprises from 1 to 7 wt % of the ZSM-12 zeolite.

21. A process as claimed in claim 20, wherein the alumina binder further comprises an additional compound selected from the group consisting of silica, titania, zirconia, ceria and gallia.

22. A process as claimed in claim 21, wherein the alumina binder contains up to 10% wt of the additional compound.

Description

EXAMPLES

Example 1 (Comparative)

(1) A ZSM-12/alumina catalyst support was prepared from 5wt % of ZSM-12 having a SAR of 95, and 95 wt % of Criterion WPA alumina.

(2) The mixture was kneaded and then shaped by extrusion into 1.6 mm cylinders. The extrudates were dried at 120 C. and subsequently calcined in air at 550 C. for 4 hours.

(3) These extrudates were impregnated by pore volume impregnation using an impregnation solution comprising hexachloroplatinic acid (H.sub.2PtCl.sub.6) as the metal source with nitric acid added to obtain pH of 1.6.

(4) The extrudates thus obtained were dried at 120 C. and subsequently statically calcined at 475 C. for 1 hour.

(5) The final catalyst contained 0.3% wt of platinum based on total weight of catalyst.

Example 2

(6) An impregnation solution was prepared comprising (NH.sub.4).sub.2PtCl.sub.6 as the metal source with NH.sub.4OH added to the impregnation solution to obtain a pH of 7.

(7) Freshly dried extrudates prepared as described in Example 1 were contacted with an excess of this impregnation solution and the mixture was continuously stirred.

(8) The impregnated extrudates were separated from the impregnation solution and excess solution was removed. The extrudates thus obtained were dried at 120 C. and subsequently calcined statically at a temperature of 475 C. for 1 hour.

(9) The final catalyst contained 0.3% wt of platinum based on total weight of catalyst.

Example 3

(10) An impregnation solution was prepared comprising hexachloroplatinic acid (H.sub.2PtCl.sub.6) as the metal source with triethanolamine added to obtain a pH of 7.

(11) Freshly dried extrudates prepared as described in Example 1 were contacted with an excess of this impregnation solution and the mixture was continuously stirred.

(12) The impregnated extrudates were separated from the impregnation solution and excess solution was removed. The extrudates thus obtained were dried at 120 C. and subsequently calcined statically at a temperature of 475 C. for 1 hour.

(13) The final catalyst contained 0.3% wt of platinum based on total weight of catalyst.

Example 4 (Comparative)

(14) Extrudates as described in Example 1 were impregnated by pore volume impregnation using an impregnation solution comprising Pt(NH.sub.3).sub.4(NO.sub.3).sub.2 as the metal source with ammoniumhydroxide added to obtain pH of 8.5.

(15) The pore volume impregnated extrudates were dried at 120 C. and subsequently statically calcined at 475 C. for 1 hour.

(16) The final catalyst contained 0.3% wt of platinum based on total weight of catalyst.

Example 5

(17) The catalysts prepared in the above Examples were tested in the isomerisation of an ethylbenzene and mixed xylene mixture (comprising 19 wt % ethylbenzene (EB), 15.5 wt % ortho-xylene (OX), 59 wt % meta-xylene (MX) and 6.5 wt % ethyl cyclohexane).

(18) The catalytic test was performed in a micro-flow reactor unit encompassing a reactor tube with an internal diameter of 15 mm, into which the catalyst was loaded together with SiC as packing material. After loading the catalyst was dried at 400 C. for 1.5 hours and then reduced with H.sub.2 at 400 C. for 1 hour at a pressure of 8 bar. The reactor was then heated to 425 C. and treated with a mixture of 20 wt % EB and 80 wt % meta-xylene for a period of 24 hours at a weight hourly space velocity (WHSV) of 5 g feed/g catalyst/h and a H.sub.2/hydrocarbon ratio of 4 mol/mol to reach a stable operation regime. Following this, the catalyst was subjected to a temperature of 387 C. and treated with the same EB and mixed xylene mixture described above (19 wt % EB, 15.5 wt % OX, 59 wt % MX and 6.5 wt % ethyl cyclohexane) at a WHSV of 4.5 g feed/g catalyst/h and a H.sub.2/hydrocarbon ratio of 4 mol/mol.

(19) The following expressions hereinafter have the following meaning.

(20) Ethylbenzene conversion (EB conversion) is the weight percent of ethylbenzene converted by the catalyst into a xylene, i.e. either ortho-, meta- or para-xylene.

(21) PXate is a measure for the degree to which the xylene reaction mixture has reached equilibrium for para-xylene. It is defined as follows:

(22) $\mathrm{PXate}=\frac{\%w\mathrm{PX}\mathrm{in}\mathrm{Xylenes}\mathrm{in}\mathrm{product}-\%w\mathrm{PX}\mathrm{in}\mathrm{Xylenes}\mathrm{in}\mathrm{feed}}{\begin{array}{c}\%w\mathrm{PX}\mathrm{in}\mathrm{Xylenes}\mathrm{in}\mathrm{equilibrium}-\\ \%w\mathrm{PX}\mathrm{in}\mathrm{Xylenes}\mathrm{in}\mathrm{feed}\end{array}}100\%$
where PX stands for para-xylene.

(23) The EB conversion was extrapolated to a PXate of 95% wt on basis of the experimental data. A PXate of 95% wt is often applied as a reference point for commercial purposes.

(24) The results can be seen in Table 1.

(25) TABLE-US-00001 TABLE 1 pH of EB conversion impregnation (% wt) at PXate solution of 95 (% wt) Comparative Example 1 1.6 33.8 Example 2 7 37.0 Example 3 7 37.0 Comparative Example 4 8.5 35.7

(26) It will be clear from Table 1 that the neutral impregnated catalysts of Examples 2 and 3 of the present invention have an improved activity in that a higher amount of ethylbenzene is converted at a PXate of 95% wt than with the acid impregnated catalyst of Comparative Example 1 or the basic impregnated catalyst of Comparative Example 4.