CATALYSTS CONTAINING COPPER, ZINC OXIDE, ALUMINA AND SILICA

Abstract

A catalyst suitable for use in carbon oxide conversion reactions is described, said catalyst in the form of a shaped unit formed from an oxidic catalyst powder, said catalyst comprising 30-70% by weight of copper oxide, combined with zinc oxide, alumina and silica, having a Si:AI atomic ratio in the range 0.005 to 0.15:1, and having a BET surface area >105 m.sup.2/g and a copper surface area >37 m.sup.2/g catalyst. The catalyst is prepared by a co-precipitation method using an alumina sol.

Claims

1. A catalyst, suitable for use in carbon oxide conversion reactions, in the form of a shaped unit formed from an oxidic catalyst powder, said catalyst comprising 30-70% by weight of copper oxide, combined with zinc oxide, alumina and silica, having a Si:Al atomic ratio in the range 0.005 to 0.15:1, and having a BET surface area ≥105 m.sup.2/g and a copper surface area >37 m.sup.2/g catalyst.

2. A catalyst according to claim 1 wherein the catalyst is a methanol synthesis catalyst comprising copper oxide in an amount in the range 50 to 70% by weight, preferably 60 to 70% by weight.

3. A catalyst according to claim 2 wherein the weight ratio CuO:ZnO is in the range of 2:1 to 3.5:1, preferably in the range of 2.5:1 to 2.75:1.

4. A catalyst according to claim 2 or claim 3 wherein the catalyst contains 20 to 30% by weight zinc oxide.

5. A catalyst according to any one of claims 1 to 4 wherein the catalyst contains alumina, in an amount in the range 5 to 20% by weight, preferably 5 to 15% by weight, more preferably 8 to 11% by weight.

6. A catalyst according to any one of claims 1 to 5 wherein the catalysts have a copper surface area ≥40 m.sup.2/g catalyst, preferably ≥45 m.sup.2/g catalyst, more preferably ≥50 m.sup.2/g catalyst.

7. A catalyst according to any one of claims 1 to 6 wherein the catalyst further comprises one or more promoter compounds selected from compounds of Mg, Co, Mn, V, Ti, Zr or rare earths, preferably magnesium compounds, more preferably magnesium oxide in an amount in the range of 1 to 5% by weight.

8. A catalyst according to any one of claims 1 to 7 wherein the amount of silica in the catalyst is in the range of 0.05 to 1.50% by weight, preferably 0.2 to 1.20% by weight, more preferably 0.3 to 0.8% by weight.

9. A catalyst according to any one of claims 1 to 8 wherein the Si:Al atomic ratio is in the range of 0.03 to 0.07:1.

10. A catalyst according to any one of claims 1 to 9 wherein the Si:Cu atomic ratio is in the range of 0.001 to 0.018:1, preferably 0.004 to 0.017:1, more preferably 0.007 to 0.009:1.

11. A catalyst according to any one of claims 1 to 10 wherein the BET surface area of the catalyst, as determined by nitrogen physisorption, is ≥107 m.sup.2/g, preferably ≥109 m.sup.2/g, more preferably ≥110 m.sup.2/g, and most preferably 115 m.sup.2/g.

12. A method for making a catalyst according to claim 1 comprising the steps of: (i) forming, in an aqueous medium, an intimate mixture comprising a co-precipitate of copper and zinc compounds, with alumina and silica wherein the alumina is provided by an alumina sol, (ii) recovering, washing and drying the intimate mixture to form a dried composition, and (iii) calcining and shaping the dried composition to form the catalyst.

13. A method according to claim 12 wherein the co-precipitate is prepared by mixing an acidic aqueous solution containing copper and zinc compounds and combining this with an aqueous alkaline precipitant solution in a precipitation vessel.

14. A method according to claim 13 wherein the copper and zinc compounds are nitrates and the alkaline precipitant comprises an alkali metal carbonate, preferably potassium carbonate.

15. A method according to claim 14 wherein the precipitation is performed at a temperature in the range of 40 to 80° C., preferably 50 to 80° C., especially 60 to 80° C.

16. A method according to any one of claims 13 to 15 wherein the co-precipitate is aged in a separate ageing vessel at a temperature in the range of 10 to 80° C., preferably in the range of 40 to 80° C., more preferably 50 to 80° C., especially 60 to 80° C.

17. A method according to any one of claims 13 to 16 wherein the alumina sol is added to the precipitation vessel separately from the acidic metal solution or alkaline precipitant solution.

18. A method according to any one of claims 12 to 17 wherein the alumina sol is a dispersion of colloidally dispersed boehmite having a D50 average particle size in the range of 5 to 200 nm, preferably 5 to 100 nm, more preferably 5-50 nm, when dispersed.

19. A method according to any one of claims 13 to 18 wherein the silica in the catalyst is derived from a silica sol, including a silica-modified alumina sol, and/or from a water-soluble silicon compound, such as an alkali metal silicate, or from an organo-silicate.

20. A method according to claim 19 wherein a silica sol is added to the acidic metal solution and/or the alumina sol and/or added to the precipitation vessel and/or the ageing vessel.

21. A method according to claim 19 wherein an alkali metal silicate is added to the alkaline precipitant solution and/or the alumina sol and/or to the precipitation and/or ageing vessel.

22. A method according to any one of claims 12 to 21 wherein the drying step is performed at a temperature in the range of 90-150° C.

23. A method according to any one of claims 12 to 22 wherein the shaped composition is a cylindrical pellet having a diameter in the range of 2.5 to 10 mm, preferably 3 to 10 mm and an aspect ratio (length/diameter) in the range of 0.5 to 2.0.

24. A method according to any one of claims 12 to 23 wherein the calcination is performed at a temperature in the range of 275 to 450° C., preferably 275 to 400° C., more preferably 275 to 350° C.

25. A carbon oxides conversion process which comprises reacting a carbon oxide containing process gas containing at least one of carbon monoxide and carbon dioxide and additionally containing hydrogen and/or steam, in the presence of a catalyst according to any one of claims 1 to 11 or prepared according to the method according to any one of claims 12 to 24.

26. A carbon oxides conversion process according to claim 25 wherein the process is selected from methanol synthesis and the water-gas shift reaction.

Description

EXAMPLE 1

[0054] An oxidic catalyst with the molar ratio Cu:Zn:Al:Mg:Si of 4.4:1.7:1.0:0.2:0.04 and a copper oxide content of 64.4 wt. % was prepared by co-precipitation of a mixed metal nitrate solution comprising nitrates of copper, zinc and magnesium with a potassium carbonate solution, with simultaneous addition of a mixture of an alumina sol and a silica sol to the precipitation vessel, at a pH of 6.3-6.8 and a temperature between 65-70° C. The resulting precipitate was aged for up to 2 hours at 65-70° C., filtered, washed with demineralised water, dried and calcined in air at 330° C. for 6 hours.

EXAMPLE 2

[0055] An oxidic catalyst with the molar ratio Cu:Zn:Al:Si of 5.1:1.9:1.0:0.04 and a copper oxide content of 66.1 wt. % was prepared as described in Example 1, without magnesium nitrate, and with calcination in air at 300° C. for 6 hours.

EXAMPLE 3

[0056] An oxidic catalyst with the molar ratio Cu:Zn:Al:Mg:Si of 4.5:1.7:1.0:0.2:0.006 and a copper oxide content of 64.5 wt. % was prepared as described in Example 1 with calcination in air at 305° C. for 6 hours.

EXAMPLE 4

[0057] An oxidic catalyst with the molar ratio Cu:Zn:Al:Mg:Si of 4.5:1.7:1.0:0.2:0.08 and a copper oxide content of 64.2 wt. % was prepared as described in Example 1 with calcination in air at 305° C. for 6 hours.

EXAMPLE 5

[0058] An oxidic catalyst with the molar ratio Cu:Zn:Al:Mg:Si of 6.7:2.5:1.0:0.3:0.11 and a copper oxide content of 66.1 wt. % was prepared as described in Example 1 with calcination in air at 305° C. for 6 hours.

EXAMPLE 6

[0059] An oxidic catalyst with the molar ratio Cu:Zn:Al:Mg:Si of 3.3:1.2:1.0:0.1:0.06 and a copper oxide content of 62.2 wt. % was prepared as described in Example 1 with calcination in air at 305° C. for 6 hours.

EXAMPLE 7

[0060] An oxidic catalyst with the molar ratio Cu:Zn:Al:Mg:Si of 5.4:2.0:1.0:0.2:0.04 and a copper oxide content of 65.9 wt. % was prepared by co-precipitation of a mixed metal nitrate solution comprising nitrates of copper, zinc and magnesium with a potassium carbonate solution, with simultaneous addition of a silica-doped alumina sol to the precipitation vessel, at a pH of 6.3-6.8 and a temperature between 65-70° C. The resulting precipitate was aged for up to 2 hours at 65-70° C., filtered, washed with demineralised water, dried and calcined in air at 330° C. for 6 hours.

EXAMPLE 8

[0061] An oxidic catalyst with the molar ratio Cu:Zn:Al:Si of 4.3:1.7:1.0:0.04 and a copper oxide content of 64.6 wt. % was prepared by co-precipitation of a mixed metal nitrate solution comprising nitrates of copper and zinc and a silica sol, with a potassium carbonate solution, with simultaneous addition of an alumina sol to the precipitation vessel, at a pH of 6.3-6.8 and a temperature between 65-70° C. The resulting precipitate was aged for up to 2 hours at 65-70° C., filtered, washed with demineralised water, dried and calcined in air at 300° C. for 6 hours.

EXAMPLE 9

[0062] An oxidic catalyst with the molar ratio Cu:Zn:Al:Si of 4.0:1.5:1.0:0.03 and a copper oxide content of 64.4 wt. % was prepared by co-precipitation of a mixed metal nitrate solution comprising nitrates of copper and zinc with a potassium carbonate solution, with simultaneous addition of an alumina sol to the precipitation vessel, at a pH of 6.3-6.8 and a temperature between 65-70° C. A silica sol was added to the resulting co-precipitate. The resulting mixture was aged for up to 2 hours at 65-70° C., filtered, washed with demineralised water, dried and calcined in air at 300° C. for 6 hours.

EXAMPLE 10

[0063] An oxidic catalyst with the molar ratio Cu:Zn:Al:Mg:Si of 4.4:1.7:1.0:0.2:0.04 and a copper oxide content of 63.2 wt. % was prepared by co-precipitation of a mixed metal nitrate solution comprising nitrates of copper, zinc and magnesium with a potassium carbonate solution, with simultaneous addition of an alumina sol containing a soluble potassium silicate to the precipitation vessel, at a pH of 6.3-6.8 and a temperature between 65-70° C. The resulting precipitate was aged for up to 2 hours at 65-70° C., filtered, washed with demineralised water, dried and calcined in air at 305° C. for 6 hours.

EXAMPLE 11

[0064] An oxidic catalyst with the molar ratio Cu:Zn:Al:Si of 4.2:1.6:1.0:0.03 and a copper oxide content of 64.4 wt. % was prepared by co-precipitation of a mixed metal nitrate solution comprising nitrates of copper and zinc with a solution comprising potassium carbonate and potassium silicate, with simultaneous addition of an alumina sol to the precipitation vessel, at a pH of 6.3-6.8 and a temperature between 65-70° C. The resulting precipitate was aged for up to 2 hours at 65-70° C., filtered, washed with demineralised water, dried and calcined in air at 300° C. for 6 hours.

EXAMPLE 12

[0065] An oxidic catalyst with the molar ratio Cu:Zn:Al:Mg:Si of 4.2:1.2:1.0:0.2:0.04 and a copper oxide content of 67.8 wt. % was prepared by co-precipitation of a mixed metal nitrate solution comprising nitrates of copper, zinc and magnesium with a sodium carbonate solution, with simultaneous addition of an alumina sol and a silica sol to the precipitation vessel, at a pH of 6.3-6.8 and a temperature between 65-70° C. The resulting precipitate was aged for up to 2 hours at 65-70° C., filtered, washed with demineralised water, dried and calcined in air at 300° C. for 6 hours.

COMPARATIVE EXAMPLE 1

[0066] An oxidic catalyst with the molar ratio Cu:Zn:Al:Si of 3.8:2.2:1.0:0.04 and a copper oxide content of 56.6 wt. % was prepared following the procedure outlined in U.S. Pat. No. 6,048,820 Example 2. A mixed metal nitrate solution containing nitrates of copper, zinc and aluminium and a silica sol, and a solution of sodium carbonate were added simultaneously to demineralised water in the precipitation vessel at room temperature with stirring. The resulting precipitate was aged at room temperature for 24 hours, filtered, washed with demineralised water, dried and calcined in air at 600° C. for 2 hours.

COMPARATIVE EXAMPLE 2

[0067] An oxidic catalyst with the molar ratio Cu:Zn:Al:Si of 3.8:2.2:1.0:0.04 and a copper oxide content of 56.6 wt. % was prepared as described in Comparative Example 1 with calcination at 305° C. for 6 hours.

COMPARATIVE EXAMPLE 3

[0068] An oxidic catalyst with the molar ratio Cu:Zn:Al:Si of 3.3:1.5:1.0:0.01 and a copper oxide content of 60.1 wt. % was prepared following the procedure outlined in CN101306369A Example 5. An aluminium nitrate solution was co-precipitated with a solution of sodium carbonate and sodium silicate at a pH of 7.0-7.2 and a temperature of 80° C. to form Precipitate A. This material was not a stable colloidal suspension and sedimented over several hours. Analysis showed the D50 average particle size to be 226 nm. Separately, a solution of copper and zinc nitrate was co-precipitated with a sodium carbonate solution at a pH of 7.0-7.2 and a temperature between 65-70° C. to form Precipitate B. Precipitate A was added to Precipitate B in a 1:7 ratio by volume. The resulting mixture was aged at 70° C. for 2 hours, filtered, washed with demineralised water, dried and calcined in air at 340° C. for 4 hours.

COMPARATIVE EXAMPLE 4

[0069] An oxidic catalyst as described in U.S. Pat. No. 4,788,175 with the molar ratio Cu:Zn:Al:Mg of 4.4:1.6:1.0:0.2 and a copper oxide content of 64.2 wt. % was prepared by co-precipitation of a mixed metal nitrate solution comprising nitrates of copper, zinc and magnesium with a solution of potassium carbonate, with simultaneous addition of an alumina sol to the precipitation vessel, at a pH of 6.3-6.8 and a temperature between 65-70° C. The resulting precipitate was aged for up to 2 hours at 65-70° C., filtered, washed with demineralised water, dried and calcined in air at 330° C. for 6 hours.

COMPARATIVE EXAMPLE 5

[0070] An oxidic catalyst with the molar ratio Cu:Zn:Al:Si of 6.2:3.4:1.0:0.08 and a copper oxide content of 59.5 wt. % was prepared following the procedure outlined in U.S. Pat. No. 9,314,774 Example 2. A solution of sodium carbonate was added to a mixed metal nitrate solution containing nitrates of copper, zinc and aluminium and a silica sol, at room temperature with stirring. The resulting precipitate was aged at 70° C. for 2 hours, filtered, washed with demineralised water, dried and calcined in air at 350° C. for 2 hours.

COMPARATIVE EXAMPLE 6

[0071] An oxidic catalyst with the molar ratio Cu:Zn:Zr:Al:Si of 4.8:3.3:1.6:1.0:0.12 and a copper oxide content of 42.5 wt. % was prepared following the procedure outlined in U.S. Pat. No. 9,314,774 Comparative Example 5. A mixed metal nitrate solution containing nitrates of copper, zinc, aluminium and zirconium and a silica sol, and a solution of sodium carbonate were added simultaneously to demineralised water at room temperature with stirring. The resulting precipitate was aged at 70° C. for 2 hours, filtered, washed with demineralised water, dried and calcined in air at 400° C. for 2 hours.

[0072] Microreactor Testing

[0073] Each of the catalyst samples were crushed and sieved to a particle size fraction of 0.6-1.0 mm. The experiments used a conventional micro-reactor. The crushed catalyst samples were fully reduced with a gas mixture of 2% v/v hydrogen in nitrogen at 225° C. A process gas mixture with a gas composition of 6% v/v CO, 6% v/v CO.sub.2, 9% v/v N.sub.2 and 79% v/v H.sub.2 was then introduced over the catalyst samples. The reduced catalyst samples were exposed to the process gas mixture at 225° C., 40,000 L/hr/kg, 50 barg at the start of life. After a period, catalyst samples were exposed to deactivating conditions over 300° C. to simulate harsh operating conditions and accelerate the ageing effects. Analysis flow scans of product gases were performed at the start of life and after the catalyst had been held at deactivation conditions. Analysis flow scans were performed by varying the mass velocity at 225° C., 50 barg. An infra-red analyser was used to determine the % v/v concentration of the exit gas streams from the reactors. The analysis flow scan data was used to calculate the relative activity of the test material against a reference catalyst, selected in these experiments to be Comparative Example 1. The relative activities are calculated from the ratio of the flow rates through each catalyst at constant conversion relative to the flow rate through the standard catalyst. The results are set out in the following table:

TABLE-US-00002 Cu BET Surface Relative Relative Surface CuO Area Si:Al Activity to Activity to Al Area content (m.sup.2/g atomic Comp. Ex. 1 Comp. Ex. 1 Sample Source (m.sup.2/g) (wt %) catalyst) ratio after 16 h after 340 h Example 1 sol 119.4 64.4 52.8 0.04 1.60 1.46 Example 2 sol 121.3 66.1 42.7 0.04 1.61 1.39 Example 3 sol 120.5 64.5 52.1 0.006 1.61 1.31 Example 4 sol 120.8 64.2 54.7 0.08 1.57 1.38 Example 5 sol 115.5 66.1 52.9 0.11 1.60 1.29 Example 6 sol 121.6 62.2 47.6 0.06 1.50 1.34 Example 7 sol 111.3 65.9 50.5 0.04 1.54 1.41 Example 8 sol 114.4 64.6 39.7 0.04 1.44 1.47 Example 9 sol 125.4 64.4 41.6 0.03 1.51 1.37 Example 10 sol 123.7 63.2 54.9 0.04 1.64 1.47 Example 11 sol 111.8 64.4 44.5 0.03 1.64 1.43 Example 12 sol 127.6 67.8 49.6 0.04 1.55 1.32 Comparative nitrate 98.9 56.6 30.1 0.04 1.00 1.00 Example 1 Comparative nitrate 94.7 56.6 29.5 0.04 0.74 0.84 Example 2 Comparative nitrate 103.9 60.1 33.1 0.01 1.16 0.95 Example 3 Comparative sol 108.7 64.2 51.7 0 1.43 1.09 Example 4 Comparative nitrate 41.9 59.5 6.1 0.08 0.29 0.28 Example 5 Comparative nitrate 86.8 42.5 17.7 0.12 0.73 0.67 Example 6

[0074] Comparative example 4, prepared using an alumina sol in a manner consistent with Examples 1-11 but without silica, has a high initial activity but an inferior retained activity.

[0075] The aluminium nitrate-based products in Comparative Examples 1, 5 and 6 have inferior initial and retained activities. This remains so, even if the calcination conditions are adjusted in accordance with Example 1 (Comparative Example 2).

[0076] Comparative example 3, prepared by separate co-precipitation of a silica-alumina co-precipitate using aluminium nitrate, also produced a catalyst with an inferior retention of activity.