METHOD FOR MAKING COPPER-CONTAINING CATALYSTS

Abstract

A method for preparing a copper-containing catalyst is described comprising the steps of: (a) combining an acidic copper-containing solution with a basic precipitant solution in a first precipitation step to form a first precipitate, (b) combining an alkali metal aluminate solution with an acidic solution in a second precipitation step to form a second precipitate, (c) contacting the first and second precipitates together in a further precipitate mixing step to form a catalyst precursor, and (d) washing, drying and calcining the catalyst precursor to form the copper-containing catalyst, wherein at least 70% by weight of the copper in the catalyst is present in the first precipitate and a silica precursor is included in the first precipitation step, the second precipitation step or the precipitate mixing step, to provide a catalyst with a silica content, expressed as SiO.sub.2, in the range of 0.1 to 5.0 wt %.

Claims

1. A method for preparing a copper-containing catalyst comprising the steps of:(a) combining an acidic copper-containing solution with a basic precipitant solution in a first precipitation step to form a first precipitate, (b) combining an alkali metal aluminate solution with an acidic solution in a second precipitation step to form a second precipitate, (c) contacting the first and second precipitates together in a further precipitate mixing step to form a catalyst precursor, and (d) washing, drying and calcining the catalyst precursor to form the copper-containing catalyst, wherein at least 70% by weight of the copper in the catalyst is present in the first precipitate and a silica precursor is included in the first precipitation step, the second precipitation step or the precipitate mixing step, to provide a catalyst with a silica content, expressed as SiO.sub.2, in the range of 0.1 to 5.0 wt %.

2. The method according to claim 1, wherein the first precipitation step is performed by combining an aqueous acidic copper-containing solution containing copper and zinc compounds with an aqueous alkali metal carbonate solution in a first precipitation vessel.

3. The method according to claim 2, wherein the copper and zinc compounds are nitrates and the alkaline precipitant comprises sodium carbonate or potassium carbonate.

4. The method according to claim 1, wherein at least 80% by weight, of the copper in the catalyst is present in the first precipitate.

5. The method according to claim 2, wherein zinc compounds are included in both the first precipitation step and the second precipitation step and the amount of zinc in the second precipitation step is in the range of 0.5 to 50% of the total zinc added.

6. The method according to claim 1, wherein one or more promoter compounds selected from compounds of Mg, Co, Mn, V, Ti, Zr or rare earths are included in the acidic copper-containing solution in the first precipitation step and/or the acidic solution in the second precipitation step.

7. The method according to claim 1, wherein the first precipitation step is performed at a temperature in the range of 40 to 80° C.

8. The method according to claim 1, wherein the acidic copper-containing solution and basic precipitant solutions are added simultaneously to the first precipitation vessel such that the pH in the first precipitation vessel is maintained between 6 and 9.

9. The method according to claim 1, wherein the second precipitation step is performed by combining an aqueous solution containing sodium aluminate or potassium aluminate with an aqueous nitric acid solution, optionally containing one or more copper compounds, one or more zinc compounds and/or one or more promoter metal compounds, in a second precipitation vessel.

10. The method according to claim 1, wherein the second precipitation step is performed at a temperature in the range of 10 to 80° C.

11. The method according to claim 1, wherein the acidic solution and alkali metal aluminate solution are combined in a second precipitation vessel with a final precipitation pH between 3 and 9.

12. The method according to claim 1, wherein the second precipitate formed in step (b) and/or the combined precipitates in step (c) are aged at a temperature in the range of 10 to 80° C.

13. The method according to claim 1, wherein step (a) is performed before or after step (b), or step (a) and step (b) are performed simultaneously.

14. The method according to claim 1, wherein neither of the precipitates from steps (a) and (b) are separated and washed prior to the combining step (c).

15. The method according to claim 1, wherein in step (c) slurries of the first and second precipitates are combined in a mixing vessel.

16. The method according to claim 1, wherein step (c) is performed at the same time as step (a) or step (b).

17. The method according to claim 1, wherein the catalyst has a silica content, expressed as SiO.sub.2, in the range of 0.1 to 3.0 wt %.

18. The method according to claim 1, wherein the silica precursor is a colloidal silica or silica sol, a water-soluble silicon compound, an alkali metal silicate, or an organo-silicate.

19. The method according to claim 1, wherein an acidic silica sol is included in the acidic copper-containing solution in the first precipitation step, the acidic solution in the second precipitation step, the first precipitate, the second precipitate or a mixture of the first and second precipitates in the precipitate mixing step.

20. The method according to claim 1, wherein an alkali metal silicate or basic silica sol is included in the basic precipitant solution in the first precipitation step, the alkali metal aluminate solution in the second precipitation step, the first precipitate, the second precipitate or a mixture of the first and second precipitates in the precipitate mixing step.

21. The method according to claim 1, wherein the drying is performed at a temperature in the range of 90-150° C.

22. The method according to claim 1, wherein the calcination is performed at a temperature in the range of 250° C. to 500° C.

23. The method according to claim 1, wherein the dried or calcined catalyst precursor is shaped by pelleting.

24. The method according to claim 1, wherein one or more zinc compounds is included in the first precipitation, or in both the first and second precipitations, the weight ratio of Cu:Zn (expressed as CuO:ZnO) in the calcined catalyst is in the range of 2:1 to 3.5:1 for methanol synthesis catalysts, and in the range of 1.4:1 to 2.0:1 for water-gas shift catalysts.

25. The method according to claim 1, wherein the calcined catalyst comprises 30-70% by weight of copper, expressed as CuO, 15 to 50% by weight of Zn, expressed as ZnO, 5 to 40% by weight alumina, expressed as Al.sub.2O.sub.3, 0 to 5% by weight magnesia, expressed as MgO, and 0.1 to 2.0% by weight Si, expressed as SiO.sub.2.

26. The method according to claim 1, wherein the calcined catalyst comprises 50 to 68% by weight of copper, expressed as CuO, 20 to 35% by weight of Zn, expressed as ZnO, 6 to 20% by weight alumina, expressed as Al.sub.2O.sub.3, 0 to 5% by weight magnesia, expressed as MgO, and 0.20 to 1.0% by weight Si, expressed as SiO.sub.2.

27. A catalyst obtainable by the method of claim 1.

28. A process selected from methanol synthesis, methanol reforming and water-gas shift using the catalyst according to claim 27.

29. The method according to claim 1, wherein the catalyst has a silica content, expressed as SiO.sub.2, in the range of 0.1 to 2.0 wt %.

30. The method according to claim 1, wherein the catalyst has a silica content, expressed as SiO.sub.2, in the range of 0.2 to 1.0 wt %.

Description

Example 1

[0054] An oxidic catalyst with the molar ratio Cu:Zn:Al:Si of 6.1:2.3:1.0:0.04 and a copper oxide content of 67.1 wt. % was prepared. In a first precipitation step a mixed metal solution comprising nitrates of copper and zinc was co-precipitated with a sodium carbonate solution at a pH of 6.7-6.9 and a temperature of 65-70° C. to form a first slurry. In a second precipitation step a nitric acid solution, which additionally contained a silica sol, was added to a solution of sodium aluminate to form a precipitate, which was aged at a pH of 6.2-7.0 and a temperature of 65-70° C. for at least 30 minutes to form a second slurry. The precipitate slurries were combined and further aged with stirring for up to 1.5 hours at 65-70° C., then dewatered, washed with demineralised water, dried and calcined in air at 300° C. for 6 hours.

Example 2

[0055] An oxidic catalyst with the molar ratio Cu:Zn:Al:Mg:Si of 5.6:2.1:1.0:0.2:0.04 and a copper oxide content of 65.8 wt. % was prepared. In a first precipitation step, a mixed metal solution comprising nitrates of copper, zinc and magnesium was co-precipitated with a sodium carbonate solution at a pH of 6.7-6.9 and a temperature of 65-70° C. In a second precipitation step, a nitric acid solution was added to a solution of sodium aluminate which additionally contained sodium silicate to form a precipitate, which was aged at a pH of 6.2-7.0 and a temperature of 65-70° C. for at least 30 minutes. The remaining steps were as described in Example 1.

Example 3

[0056] An oxidic catalyst with the molar ratio Cu:Zn:Al:Si of 5.1:1.9:1.0:0.08 and a copper oxide content of 65.8 wt. % was prepared using the method of Example 1.

Example 4

[0057] An oxidic catalyst with the molar ratio Cu:Zn:Al:Si of 6.0:2.2:1.0:0.04 and a copper oxide content of 66.9 wt. % was prepared. In a first precipitation step, a mixed metal solution comprising nitrates of copper and zinc, and additionally containing a silica sol, was co-precipitated with a sodium carbonate solution at a pH of 6.7-6.9 and a temperature of 65-70° C. In a second precipitation step, a nitric acid solution was added to a solution of sodium aluminate to form a precipitate, which was aged at a pH of 6.2-7.0 and a temperature of 65-70° C. for at least 30 minutes. The remaining steps were as described in Example 1.

Example 5

[0058] An oxidic catalyst with the molar ratio Cu:Zn:Al:Mg:Si of 5.6:2.1:1.0:0.3:0.03 and a copper oxide content of 65.8 wt. % was prepared. In a first precipitation step, a mixed metal solution comprising nitrates of copper and zinc was co-precipitated with a sodium carbonate solution at a pH of 6.7-6.9 and a temperature of 65-70 ° C. In a second precipitation step, a nitric acid solution which additionally contained magnesium nitrate and a silica sol was added to a solution of sodium aluminate to form a precipitate, which was aged at a pH of 6.2-7.0 and a temperature of 65-70° C. for at least 30 minutes. The remaining steps were as described in Example 1.

Example 6

[0059] An oxidic catalyst with the molar ratio Cu:Zn:Al:Mg:Si of 5.3:2.0:1.0:0.2:0.05 and a copper oxide content of 65.2 wt. % was prepared. In a first precipitation step, a mixed metal solution comprising nitrates of copper, zinc and magnesium was co-precipitated with a sodium carbonate solution at a pH of 6.7-6.9 and a temperature of 65-70° C. In a second precipitation step, a solution of nitric acid and zinc nitrate was added to a solution of sodium aluminate which additionally contained sodium silicate to form a precipitate, which was aged at a pH of 6.2-7.0 and a temperature of 65-70° C. for at least 30 minutes. The remaining steps were as described in Example 1. The amounts of zinc nitrate used in the solutions was such that the first precipitate contained 84% of the Zn and the second precipitate 16% of the Zn in the calcined catalyst.

Example 7

[0060] An oxidic catalyst with the molar ratio Cu:Zn:Al:Si of 4.9:1.9:1.0:0.03 and a copper oxide content of 65.6 wt. % was prepared. In a first precipitation step, a mixed metal solution comprising nitrates of copper and zinc was co-precipitated with a sodium carbonate solution at a pH of 6.7-6.9 and a temperature of 65-70° C. In a second precipitation step, a solution of nitric acid and copper nitrate, which additionally contained a silica sol, was added to a solution of sodium aluminate to form a precipitate, which was aged at a pH of 6.2-7.0 and a temperature of 65-70° C. for at least 30 minutes. The remaining steps were as described in Example 1. The amounts of copper nitrate used in the solutions was such that the first precipitate contained 94% of the Cu and the second precipitate 6% of the Cu in the calcined catalyst.

Example 8

[0061] An oxidic catalyst with the molar ratio Cu:Zn:Al:Si of 5.1:1.9:1.0:0.05 and a copper oxide content of 66.1 wt. % was prepared by addition of a nitric acid solution which additionally contained a silica sol to a solution of sodium aluminate to form a precipitate, which was aged at a pH of 6.2-7.0 and a temperature of 65-70° C. for at least 30 minutes. A mixed metal solution comprising nitrates of copper and zinc and a sodium carbonate solution were simultaneously added to the first precipitate with stirring, while maintaining a pH of 6.7-6.9 and a temperature of 65-70° C. The final precipitate slurry was aged for 1 hour at 65-70° C., then dewatered, 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 5.7:2.2:1.0:0.03 and a copper oxide content of 66.6 wt. % was prepared. In a first precipitation step a mixed metal solution comprising nitrates of copper and zinc was co-precipitated with a sodium carbonate solution at a pH of 6.7-6.9 and a temperature of 65-70° C. to form a first slurry. In a second precipitation step a nitric acid solution, which additionally contained a silica sol, was added to a solution of sodium aluminate to form a precipitate, which was aged at a pH of 3.5-4.5 and a temperature of 65-70° C. for at least 30 minutes to form a second slurry. The remaining steps were as described in Example 1.

Example 10

[0063] An oxidic catalyst with the molar ratio Cu:Zn:Al:Mg:Si of 4.6:1.8:1.0:0.2:0.04 and a copper oxide content of 63.6 wt. % was prepared. In a first precipitation step, a mixed metal solution comprising nitrates of copper, zinc and magnesium was co-precipitated with a sodium carbonate solution, which additionally contained sodium silicate, at a pH of 6.6-6.8 and a temperature of 63-68° C. In a second precipitation step, a nitric acid solution was added to a solution of sodium aluminate to form a precipitate, which was aged at a pH of 6.2-7.0 and a temperature of 65-70° C. for at least 30 minutes. The remaining steps were as described in Example 1.

Comparative Example 1

[0064] 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 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 a stirred vessel at room temperature. The resulting precipitate was aged at room temperature for 24 hours, dewatered, washed with demineralised water, dried and calcined in air at 600° C. for 2 hours.

Comparative Example 2

[0065] An oxidic catalyst with the molar ratio Cu:Zn:Al:Si of 4.4:1.6:1.0:0.05 and a copper oxide content of 65.8 wt. % was prepared following the method described in CN110935478. A mixed metal solution containing nitrates of copper and zinc and sodium silicate, a sodium aluminate solution and a sodium hydroxide solution were added simultaneously to demineralised water in a stirred vessel at 55° C. and at a pH of 6-7. The addition of sodium hydroxide was necessary in order to achieve the required precipitation pH and final composition. The resulting precipitate was aged at 65° C. and a pH of 6.5 for 30 minutes. This precipitate contained 40 wt. % of the total copper oxide content and 50 wt. % of the total silica content. A mixed metal solution containing nitrates of copper and aluminium and sodium silicate and a solution of sodium carbonate were simultaneously combined with the precipitate at 65° C. and a pH of 8-9 with stirring. The resulting slurry was aged at 65° C. and a pH of 8.5 for 2 hours before being dewatered, washed with demineralised water, dried and calcined in air at 300° C. for 6 hours.

Comparative Example 3

[0066] 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 CN101306369 Example 5, by co-precipitating a mixed metal solution comprising nitrates of copper and zinc with a sodium carbonate solution at a pH of 7.0-7.2 and a temperature between 65-70° C. to form a first precipitate. Separately, a second precipitate was formed by mixing an aluminium nitrate solution with a solution of sodium carbonate and sodium silicate at a pH of 7-7.2 and a temperature of 80° C. then ageing at 65° C. for 40 minutes. The first and second precipitates were combined in a 1:7 ratio by volume, and the mixture was aged at 70° C. with stirring for 2 hours. The slurry was dewatered, washed with demineralised water, then dried and calcined in air at 340° C. for 4 hours.

Comparative Example 4

[0067] An oxidic catalyst with the molar ratio Cu:Zn:Al:Si of 5.4:2.0:1.0:0.16 and a copper oxide content of 65.7 wt. % was prepared by addition of a nitric acid solution which additionally contained a silica sol to a solution of sodium aluminate to form a precipitate, which was aged at a pH of 6.2-7.0 and a temperature of 65-70° C. for at least 30 minutes. Separately a mixed metal solution comprising nitrates of copper and zinc was co-precipitated with a sodium carbonate solution at a pH of 6.7-6.9 and a temperature of 65-70° C. The two precipitates were combined and further aged with stirring for up to 1.5 hours at 65-70° C., then dewatered, washed with demineralised water, dried and calcined in air at 300° C. for 6 hours.

Comparative Example 5

[0068] An oxidic catalyst with the molar ratio Cu:Zn:Al:Si of 4.3:1.6:1.0:0.03 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, which additionally contained a silica sol, with a sodium aluminate solution and a sodium carbonate solution at a pH of 6.3-6.9 and a temperature between 65-70° C. The resulting precipitate was aged for up to 1.5 hours at 65-70° C., then dewatered, washed with demineralised water, dried and calcined in air at 300° C. for 6 hours.

Comparative Example 6

[0069] An oxidic catalyst with the molar ratio Cu:Zn:Al:Si of 4.0:1.7:1.0:0.04 and a copper oxide content of 62.5 wt. % was prepared. In a first precipitation step, a solution of copper nitrate was co-precipitated with a sodium carbonate solution at a pH of 6.7-6.9 and a temperature of 65-70° C. In a second precipitation step, a solution of zinc nitrate, which additionally contained a silica sol, was added to a solution of sodium aluminate to form a precipitate. A solution of sodium hydroxide was added to the precipitate to adjust the pH, and the resulting slurry was aged at a pH of 6.5-7.0 and a temperature of 65-70° C. for at least 30 minutes. The two precipitates were combined and further aged with stirring for 45 minutes at 65-70° C., then dewatered, washed with demineralised water, dried and calcined in air at 300° C. for 6 hours.

[0070] The catalyst properties were as follows:

TABLE-US-00001 Copper BET surface Malachite surface area area crystallite (m.sup.2/g (m.sup.2/g, SiO2 Example size (nm) catalyst) compacted) (wt %) Example 1 6.1 48 106 0.32 Example 2 5.0 71 114 0.37 Example 3 6.4 51 131 0.74 Example 4 5.8 53 99 0.32 Example 5 5.4 61 103 0.30 Example 6 4.5 64 108 0.46 Example 7 6.0 50 132 0.27 Example 8 6.1 53 104 0.48 Example 9 5.9 56 125 0.29 Example 10 4.0 71 117 0.41 Comparative n/a 35 99 0.48 Example 1 Comparative 23.7 30 41 0.52 Example 2 Comparative n/a 40 104 0.20 Example 3 Comparative 5.3 56 116 1.46 Example 4 Comparative 14.5 38 100 0.39 Example 5 Comparative 18.2 10 56 0.41 Example 6

Microreactor Testing

[0071] 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. This process gas mixture is representative of a synthesis gas produced by reforming of natural gas. 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 deactivation 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 Activity at 16 Activity at 275 hours on-line hours on-line relative to relative to comparative comparative Example example 1 example 1 Example 1 1.38 1.41 Example 2 1.74 1.43 Example 3 1.40 1.25 Example 4 1.42 1.35 Example 5 1.49 1.43 Example 6 1.43 1.29 Example 7 1.45 1.36 Example 8 1.47 1.44 Example 9 1.50 1.42 Example 10 1.68 1.41 Comparative Example 1 1.00 1.00 Comparative Example 2 0.80 0.94 Comparative Example 3 1.11 0.91 Comparative Example 4 1.46 0.72 Comparative Example 5 1.03 0.99 Comparative Example 6 0.28 0.25

[0072] The testing results show that catalysts made via methods of the invention possess both higher initial activity and higher retained activity, following a period of high temperature deactivation under methanol synthesis conditions, than catalyst made via prior methods (comparative examples 1, 2 and 3).

[0073] Comparative example 4 shows that higher silica loadings can be detrimental to long-term catalyst performance. Comparative example 5 exemplifies a single-step process using sodium aluminate which has poor activity compared to the two-step method. Comparative example 6 demonstrates that when no zinc is present with the copper in the first precipitation step, the activity of the catalyst is severely impacted.

[0074] In addition to the above tests carried out with a conventional synthesis gas, further microreactor tests were also carried out on the catalyst of Example 2 to evaluate performance under conditions appropriate for CO.sub.2 hydrogenation. In this case, following reduction as above, the samples were exposed to a process gas mixture with a composition of 16 % v/v CO.sub.2, 2% v/v CO, 10% v/v N.sub.2 and 72% v/v H.sub.2, initially at 225° C., 70,000 L/hr/kg and 50 barg. After a period, the samples were exposed to deactivation conditions above 265° C. to simulate harsh operation and accelerate deactivation. As in the previous testing, flow scans were periodically carried out throughout the run at the milder conditions in order to monitor the remnant activity of the samples. The results obtained are shown in the following table, again with the Comparative example 1 as the reference catalyst:

TABLE-US-00003 Activity at 164 Activity at 400 hours on-line hours on-line relative to relative to comparative comparative Example example 1 example 1 Example 2 1.26 1.42 Comparative Example 1 1.00 1.00

[0075] These results again show that catalysts made via methods of the invention possess both higher initial activity and higher retained activity, following a period of high temperature deactivation under CO.sub.2 hydrogenation to methanol conditions, than catalyst made via prior methods.