SILICA-MODIFIED CATALYST SUPPORTS

Abstract

A method for preparing a silica-modified catalyst support is described comprising: (i) applying an alkyl silicate solution to a porous support material in an amount to produce a silica content of the silica-modified catalyst support, expressed as Si, in the range 0.25 to 15% by weight, (ii) drying the resulting silicate-modified support and recovering a first alcoholic solution, (iii) optionally treating the dried silicate-modified support with water, drying the resulting water-treated support and recovering a second alcoholic solution, and (iv) calcining the dried material to form the silica-modified catalyst support, wherein the first alcoholic solution contains 10 vol % water and at least a portion of the first alcoholic solution is mixed with alkyl silicate to form the alkyl silicate solution.

Claims

1. A method for preparing a silica-modified catalyst support, comprising: (i) applying an alkyl silicate solution to a porous support material in an amount to produce a silicate-modified catalyst support having a silica content, expressed as Si, in the range of 0.25 to 15% by weight, (ii) drying the silicate-modified support and recovering a first alcoholic solution, and (iii) calcining the dried silicate-modified support to form the silica-modified catalyst support, wherein the first alcoholic solution contains 0.05 to 10 vol % water and at least a portion of the first alcoholic solution is mixed with alkyl silicate to form the alkyl silicate solution.

2. The method according to claim 1, wherein the alkyl silicate concentration in the alkyl silicate solution is in the range of 50-75% by weight.

3. The method according to claim 1, wherein the first alcoholic solution contains <5% water by volume.

4. The method according to claim 1, wherein the porous support material has a moisture content of 6.0 wt %.

5. The method according to claim 4, further comprising pre-drying the porous support material.

6. The method according to claim 1, further comprising adjusting the water content of the first alcoholic solution before mixing it with the alkyl silicate.

7. The method according to claim 6, wherein the amount of water in the first alcoholic solution is adjusted by dehydrating including one or more of distillation, adsorption, or membrane separation.

8. The method according to claim 1, wherein the porous support material comprises alumina, titania, or zirconia.

9. The method according to claim 1, wherein the porous support material comprises a transition alumina or hydrated alumina.

10. The method according to claim 1, wherein the porous support material is a spray-dried powder with an average particle size in the range of 1 to 200 micrometres.

11. The method according to claim 1, wherein the porous support material is a shaped unit with a particle size in the range of 1 to 50 mm.

12. The method according to claim 1, wherein the alkyl silicate is a tetraalkyl silicate of the formula Si(OR).sub.4, where R is a C1-C4 alkyl group.

13. The method according to claim 1, wherein the alkyl silicate comprises tetraethyl-orthosilicate and the alcohol in the first and second alcoholic solutions comprises ethanol.

14. The method according to claim 1, wherein the silica content of the silica-modified catalyst support, expressed as Si, is in the range of 1 to 10% by weight.

15. The method according to claim 1, wherein the volume of the alkyl silicate solution is less than or equal to the pore volume of the porous support material.

16. The method according to claim 1, wherein the silicate-modified support is dried at a temperature in the range of 30-150 C.

17. The method according to claim 1, wherein the moisture content of the dried silicate-modified support is 5% by weight.

18-21. (canceled)

22. The method according to claim 1, wherein the calcination step is performed by heating the dried support to a temperature in the range of 500-1100 C.

23. The method of preparing a catalyst comprising applying a catalytically active material to a silica-modified catalyst support prepared according to the method of claim 1.

24. The method according to claim 23 wherein the catalytically active material comprises cobalt.

25. A process for the Fischer-Tropsch synthesis of hydrocarbons comprising contacting a gas mixture containing hydrogen and carbon monoxide over a cobalt-catalyst prepared according to the method of claim 24.

26. The method according to claim 1, further comprising treating the dried silicate-modified support with water, drying the resulting water-treated support and recovering a second alcoholic solution.

27. The method according to claim 26, wherein the water treating comprises applying water or water containing an alcohol to the dried silicate-modified support.

28. The method according to claim 27, wherein the water is mains water, distilled water, or purified water.

29. The method according to claim 27, wherein the water containing alcohol comprises at least part of the first alcoholic solution or second alcoholic solution.

30. The method according to claim 27, wherein the water treated support is dried at a temperature in the range of 30-150 C.

Description

EXAMPLE 1

[0042] A solution was formed using 118 kg ethanol/water having a water content of 0.85% wt and 212 kg of TEOS. This solution was added to a mixer drier where it was mixed with 655 kg of a gamma alumina containing 19.65 kg water (3% by weight) under nitrogen. The mixture was dried at 80 C. for 2 hours. The water content in the dried product was 1% by weight. The vapours evolved during the drying process were fed to a condenser at 10 C. to collect a first alcoholic solution comprising 134.3 kg ethanol, 8.1 kg TEOS and 4.7 kg water. The water content therefore without pre-drying of the alumina or a dehydration treatment of the first alcoholic solution was 3.2% wt (2.5% by volume). However, the effect of the recycle of the first alcoholic solution recovered from the condenser and the gamma alumina containing 3% wt water was to increase the water content of the first alcoholic solution over the subsequent batches towards a steady state of 5.1% wt (4.0% by volume) as follows;

TABLE-US-00001 Water in first alcoholic Water in first alcoholic Batch No. solution (% wt) solution (% vol) 1 3.2 2.5 2 4.3 3.4 3 4.8 3.8 4 5.0 3.9 5 5.1 4.0

EXAMPLE 2

[0043] The process of Example 1 was repeated except the alumina was pre-dried to a moisture content of 2.5% wt. The water content of the first alcoholic solution was 1.8% wt (1.4% by volume). The water content of the dried product was again 1% by weight. The effect of the recycle of the first alcoholic solution recovered from the condenser and the gamma alumina containing 2.5% wt water was to increase the water content of the first alcoholic solution over the subsequent batches towards a steady state of 2.7% wt (2.1% by volume) as follows;

TABLE-US-00002 Water in first alcoholic Water in first alcoholic Batch No. solution (% wt) solution (% vol) 1 1.8 1.4 2 2.3 1.8 3 2.5 2.0 4 2.6 2.0 5 2.7 2.1

EXAMPLE 3

[0044] The process of Example 1 was repeated except the alumina was pre-dried to a moisture content of 1.5% wt and the product was dried instead to 0.5% by weight water. Whereas the water content from the feed alumina was reduced, drying to a lower water content in the product resulted in a first alcoholic solution with an increased water content. The water content of the first alcoholic solution was 1.9% wt (1.5% by volume). The effect of the recycle of the first alcoholic solution recovered from the condenser was to increase the water content of the first alcoholic solution over the subsequent batches towards a steady state of 3.0% wt (2.3% by volume) as follows;

TABLE-US-00003 Water in first alcoholic Water in first alcoholic Batch No. solution (% wt) solution (% vol) 1 1.9 1.5 2 2.5 2.0 3 2.8 2.2 4 2.9 2.3 5 3.0 2.3

EXAMPLE 4

[0045] The process of Example 1 was re-modelled to establish the amount of water to be removed from the ethanol-water first alcoholic solution to reduce its water content to 3.0% by weight (2.3% by volume) as an alternative to pre-drying the alumina. Alumina with water contents in the range 3-6% by weight were considered and the silicate-modified products were dried to water levels of 0.5% or 1% by weight. The results were as follows;

TABLE-US-00004 Residual Water Water water in dried concentration concentration Water to be Alumina silicate- in first in first removed from water modified alcoholic alcoholic first alcoholic content alumina solution solution solution (% weight) (% weight) (% weight) (% volume) (kg per batch). 6.0 0.5 12.5 9.7 13.7 4.0 0.5 8.9 7.0 8.3 4.0 1.0 6.6 5.1 4.9 3.0 0.5 6.8 5.3 5.2 3.0 1.0 4.2 3.3 1.6

[0046] The water in the first alcoholic solution may be removed by one or more steps of distillation, adsorption, and membrane separation.