Pre-gold-plating Pd-Au-coated shell catalysts

Abstract

The present invention relates to a method for producing a shell catalyst that is suitable for producing vinyl acetate monomer (VAM). The present invention also relates to a shell catalyst that can be obtained by the method according to the invention as well as the use of the shell catalyst according to the invention for producing VAM.

Claims

1. Method for producing a shell catalyst, comprising the steps of: (a) subjecting a packed bed of a catalyst support body to a circulating movement; (b) bringing an atomized aqueous solution containing an Au-containing precursor compound into contact with the packed bed of the catalyst support body subjected to the circulating movement by spraying on of the solution; (c) bringing an atomized aqueous solution containing a Pd-containing precursor compound with the catalyst support body produced after step (b); and (d) reducing the metal components of the precursor compounds to elemental metals by subjecting the catalyst support body obtained in step (c) to a temperature treatment in a non-oxidizing atmosphere.

2. Method according to claim 1, wherein, during the bringing into contact in step (c), the solution is sprayed onto a packed bed of the catalyst support body subjected to a circulating movement.

3. Method according to claim 1, wherein the temperature treatment is carried out within a range of from 60 C. to 500 C.

4. Method according to claim 2, wherein the circulating movement of the catalyst support bodies is carried out with a process gas.

5. Method according to claim 2, wherein the circulating movement of the catalyst support bodies takes place in a fluid bed or a fluidized bed.

6. Method according to claim 1, wherein the ratio of the weight of the solution sprayed on in step (b) or (c) to the weight of the packed bed of the support body lies in the range of from 0.005 to 0.1.

7. Method according to claim 1, wherein in step (c) an Au-containing precursor compound is applied to the catalyst support body.

8. Method according to claim 1, wherein, between steps (c) and (d), an Au-containing precursor compound is applied in a step (c1) to the catalyst support body obtained in step (c).

9. Method according to claim 1, wherein the shell catalyst contains a proportion of Au in the range of from 0.1 to 1.0 wt-% relative to the total weight of the shell catalyst.

10. Method according to claim 1, wherein the shell catalyst contains a proportion of Pd in the range of from 0.6 to 2.0 wt-% relative to the total weight of the shell catalyst.

11. Method according to claim 1, wherein the Pd-containing precursor compound is a compound selected from the group consisting of a nitrate compound, nitrite compound, acetate compound, tetraammine compound, diammine compound, hydrogen carbonate compound, hydroxidic metallate compounds and mixtures thereof.

12. Method according to claim 1, wherein the Au-containing precursor compound is selected from the group consisting of an acetate compound, nitrite compound, nitrate compound, hydroxidic metallate compound and mixtures thereof.

13. Method according to claim 1, wherein the Au-containing precursor compound is selected from the group consisting of NaAuO.sub.2, KAuO.sub.2, LiAuO.sub.2, RbAuO.sub.2 and mixtures thereof.

14. Method according to claim 1, wherein the catalyst support body after step (b) contains a proportion of Au in the range of from 0.1 to 1.0 wt-% relative to the total weight of the catalyst support body.

15. Method according to claim 1, wherein the catalyst support body after step (c) contains a proportion of Au in the range of from 0.6 to 2.0 wt-% relative to the total weight of the catalyst support body.

16. Method according to claim 1, wherein the non-oxidizing atmosphere contains a reducing agent.

17. Method according to claim 16, wherein the reducing agent is hydrogen.

18. Shell catalyst made by a process comprising the steps of: (a) subjecting a packed bed of a catalyst support body to a circulating movement; (b) bringing an atomized aqueous solution containing an Au-containing precursor compound into contact with the packed bed of the catalyst support body subjected to the circulating movement by spraying on of the solution; (c) bringing an atomized aqueous solution containing a Pd-containing precursor compound with the catalyst support body produced after step (b); and (d) reducing the metal components of the precursor compounds to elemental metals by subjecting the catalyst support body obtained in step (c) to a temperature treatment in a non-oxidizing atmosphere.

19. A shell catalyst according to claim 18 for the oxyacetylation of olefins.

Description

(1) The invention is described in more detail below using a FIGURE and embodiment examples without these being understood as limiting:

(2) FIGURE:

(3) FIG. 1: FIG. 1 shows the VAM selectivities calculated from the measured VAM and CO.sub.2 peaks as a function of the O.sub.2 conversion using 3 different shell catalysts during the catalytic synthesis of VAM.

EXAMPLES

(4) The percentages relating to the solutions containing the precursor compounds are atomic wt-% of the respective metal relative to the total weight of the solution.

Comparison Example

Catalyst 1

(5) 100 g of the support KA-Zr-14 (KA-160 support doped with 14% ZrO.sub.2 from Sd-Chemie) is coated with an aqueous mixed solution of Pd(NH.sub.3).sub.4(OH).sub.2 and KAuO.sub.2 (produced by mixing 27.79 g of a 4.70% Pd solution+12.09 g of a 3.60% Au solution+50 ml of water) in an Innojet IAC025 coater at 70 C. (spraying rate 80%, i.e. 4 g of solution was applied per minute per 100 g of support), then dried at 90 C. for 40 minutes in a fluidized bed dryer and reduced at 150 C. for 4 hours with forming gas. After the reduction a 2-molar KOAc solution is impregnated using the incipient wetness principle, the impregnation time is one hour. This is again followed by drying in a fluidized bed dryer at 90 C. for 40 minutes. The LOI-free (LOI: loss on ignition) metal contents of the finished catalyst determined by chemical elemental analysis are 1-15% Pd+0.41% Au.

Comparison Example 2

Catalyst 2

(6) 100 g of the support KA-Zr-14 (KA-160 support doped with 14% ZrO.sub.2 from Std-Chemie) is coated with an aqueous solution of 27.79 g Pd(NH.sub.3).sub.4(OH).sub.2 (produced by mixing 27.79 g of a 4.70% Pd solution+50 ml of water) (4.70%) in an Innojet IAC025 coater at 70 C. (spraying rate 80%, i.e. 4 g of solution was applied per minute per 100 g of support) and then coated with 12.09 g of KAuO.sub.2 (produced by mixing 12.09 g of a 3.60% Au solution+50 ml of water) in an Innojet IAC025 coater at 70 C. (spraying rate 80%, i.e. 4 g of solution was applied per minute per 100 g of support), dried at 90 C. for 40 minutes in a fluidized bed dryer and reduced at 150 C. for 4 hours with forming gas. After the reduction a 2-molar KOAc solution is impregnated using the incipient wetness principle. The impregnation time is one hour. This is again followed by drying in a fluidized bed dryer at 90 C. for 40 minutes. The LOI-free metal contents of the finished catalyst determined by chemical elemental analysis are 1.16% Pd+0.41% Au

Example 1

Catalyst 3

(7) 100 g of the support KA-Zr-14 (KA-160 support doped with 14% ZrO.sub.2 from Sd-Chemie) is coated with an aqueous solution of 12.09 g of KAuO.sub.2 (produced by mixing 12.09 g of a 3.60% Au solution+50 ml of water) in an Innojet IAC025 coater at 70 C. (spraying rate 80%, i.e. 4 g of solution was applied per minute per 100 g of support) and then coated with 27.79 g of Pd(NH.sub.3).sub.4(OH).sub.2 (produced by mixing 27.79 g of a 4.70% Pd solution+50 ml of water) in an Innojet IAC025 coater at 70 C. (spraying rate 80%, i.e. 4 g of solution was applied per minute per 100 g of support), dried at 90 C. for 40 minutes in a fluidized bed dryer and reduced at 150 C. for 4 hours with forming gas. After the reduction a 2-molar KOAc solution is impregnated using the incipient wetness principle. The impregnation time is one hour. This is again followed by drying in a fluidized bed dryer at 90 C. for 40 minutes. The LOI-free metal contents of the finished catalyst determined by chemical elemental analysis are 1.17% Pd+0.41% Au.

Example 2

Catalyst 4

(8) 100 g of the support KA-Zr-14 (KA-160 support doped with 14% ZrO.sub.2 from Sd-Chemie) is coated with an aqueous solution of 3.02 g of KAuO.sub.2 (produced by mixing 3.02 g of a 3.60% Au solution+50 ml of water) in a coating drum, (DF-LDP-3 coating pan from D&F Drouven GmbH, see also for example DE 10 2005 061382 A1) at 50 C. (spraying rate 80%, i.e. 4 g of solution was applied per minute per 100 g of support) and then coated with a mixed solution of 27.79 g of Pd(NH.sub.3).sub.4(OH).sub.2 and 9.07 g of KAuO.sub.2 (produced by mixing 27.79 g of a 4.70% Pd solution+9.07 g of a 3.60% Au solution+50 ml of water) in a coating drum at 50 C. (spraying rate 80%, i.e. 4 g of solution was applied per minute per 100 g of support), dried at 90 C. for 40 minutes in a fluidized bed dryer and reduced at 150 C. for 4 hours with forming gas. After the reduction a 2-molar KOAc solution is impregnated using the incipient wetness principle, the impregnation time is one hour. This is again followed by drying in a fluidized bed dryer at 90 C. for 40 minutes. The LOI-free metal contents of the finished catalyst determined by chemical elemental analysis are 1.19% Pd+0.42% Au.

Example 3

Test Results

(9) of catalysts 1 to 3 in respect of their selectivity during the synthesis of vinyl acetate monomer:

(10) For this, acetic acid, ethylene and oxygen were each passed over the catalysts 1 to 3 at a temperature of 140 C./12 h.fwdarw.143 C./12 h.fwdarw.146 C./12 h (these are the respective reaction temperatures that apply in turn during the automated execution of the screening protocol, i.e. measurement is carried out for 12 h at 140 C., then for 12 h at 143 C., and then for 12 h at 146 C. reactor temperature) and a pressure of 6.5 bar. The concentrations of the components used were: 40.2% ethylene, 6.3% O.sub.2, 0.6% CO.sub.2, 9.6% methane, 12.68% acetic acid, remainder N.sub.2.

(11) FIG. 1 and Table 1 below show the test results for catalysts 1 to 3. Under comparable process conditions, catalyst 4 exhibits a selectivity that lies between the selectivity of catalysts 1 and 2 and the selectivity of catalyst 3.

(12) TABLE-US-00001 TABLE 1 Catalyst 1 Catalyst 2 Catalyst 3 Selectivity Selectivity Selectivity calculated calculated calculated from VAM from VAM from VAM and CO2 O2 and O2 and CO2 O2 peaks conversion CO2 peaks conversion peaks conversion [%] [%] [%] [%] [%] [%] 94.98 38.88 95.06 40.73 94.29 51.86 94.92 38.92 95.07 40.66 94.26 51.88 94.92 38.91 95.1 40.75 94.3 51.84 94.88 38.95 95.04 40.46 94.28 52.15 94.92 39.64 95.02 40.47 94.27 52.28 94.55 42.71 94.7 44.16 93.83 56.68 94.58 42.9 94.65 43.95 93.89 56.95 94.58 43.16 94.74 44.21 93.93 56.86 94.63 42.98 94.77 43.88 93.98 56.99 94.6 42.67 94.81 43.87 93.92 56.86 94.64 42.94 94.82 43.97 93.92 56.91 94.68 43.01 94.85 43.7 93.46 60.73 94.28 46.29 94.47 47.26 93.51 61.02 94.31 46.6 94.41 46.92 93.56 61.03 94.33 46.51 94.51 47.02 93.54 60.94 94.32 46.3 94.49 46.87 93.56 60.9 94.27 46.25 94.49 46.68 93.56 61.15 94.31 46.02 94.44 46.24 93.55 60.98 94.29 46.42 94 49.92 93.01 64.82 93.75 49.91 94.01 50.08 92.92 65.06 93.77 49.82 93.95 49.89 92.96 64.86 93.69 49.95 93.98 49.88 92.97 64.77 93.96 49.66 94.11 49.53 93.11 64.67 93.84 49.37 94.13 49.6 93.13 64.61 93.89 49.66 94.14 49.49 93.10 64.49 94.73 42.76 94.95 42.62 94.12 57.3 94.84 42.34 94.97 42.44 94.14 57.02 94.73 42.15 94.95 42.22 94.16 56.78 94.73 41.76 94.92 42.17 94.16 56.62 94.76 41.84 94.99 42.1