US 4,048,096 AGranted

Surface impregnated catalyst

AssigneeE. I. Du Pont de Nemours and Company

InventorThomas Charles Bissot

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Abstract

A surface impregnated catalyst consisting essentially of a catalyst support, a palladium-gold alloy distributed in a surface layer of the catalyst support extending less than about 0.5 millimeter from the surface, and alkali metal acetate are provided. The catalyst has substantially higher specific activity than prior art catalysts used for the production of vinyl acetate.

Claims19

Dependent claims

In the process of preparing a catalyst comprising palladium and gold deposited on a catalyst support having a particle diameter of from about 3 to about 7 mm, and a pore volume of from about 0.2 to about 1.5 ml/g, a 10% by weight water suspension of said support having a pH of from about 3.0 to about 9.0, by

1. impregnating the catalyst support with aqueous solution of water-soluble palladium and gold compounds,
2. precipitating water-insoluble palladium and gold compounds on the catalyst support by contacting the impregnated catalyst support with a solution of compounds capable of reacting with the water-soluble palladium and gold compounds to form water-insoluble palladium and gold compounds,
3. converting the water-insoluble palladium and gold compounds into palladium and gold metal by treatment with a reducing agent,
4. washing the catalyst with water,
5. contacting the catalyst with alkali metal acetate, and
6. drying the catalyst,
the improvement where the palladium and gold is distributed as an alloy in a surface layer of the catalyst support, said surface layer extending less than about 0.5 mm from the surface of said support, the palladium in said alloy being present in an amount of from about 1.5 to about 5.0 grams per liter of catalyst, the gold being present in an amount of from about 0.5 to about 2.25 grams per liter of catalyst, and the alkali metal acetate being present in an amount of from about 5 to about 60 grams per liter of catalyst, said impregnating step being carried out with an aqueous solution of palladium and gold compounds, the total volume of which is from about 95% to about 100% of the absorptive capacity of the catalyst support and said precipitating step being carried out by soaking the wet catalyst support with a solution of an alkali metal silicate, the amount of alkali silicate being such that after the alkali metal silicate solution has been in contact with the catalyst support for about 12 to 24 hours the pH of said solution is from about 6.5 to about 9.5.

4 more elements

Dependencies are inferred from the claim text.

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Abstract

1. impregnating the catalyst support with aqueous solution of water-soluble palladium and gold compounds,
2. precipitating water-insoluble palladium and gold compounds on the catalyst support by contacting the impregnated catalyst support with a solution of compounds capable of reacting with the water-soluble palladium and gold compounds to form water-insoluble palladium and gold compounds,
3. converting the water-insoluble palladium and gold compounds into palladium and gold metal by treatment with a reducing agent,
4. washing the catalyst with water,
5. contacting the catalyst with alkali metal acetate, and
6. drying the catalyst,
the improvement where the palladium and gold is distributed as an alloy in a surface layer of the catalyst support, said surface layer extending less than about 0.5 mm from the surface of said support, the palladium in said alloy being present in an amount of from about 1.5 to about 5.0 grams per liter of catalyst, the gold being present in an amount of from about 0.5 to about 2.25 grams per liter of catalyst, and the alkali metal acetate being present in an amount of from about 5 to about 60 grams per liter of catalyst, said impregnating step being carried out with an aqueous solution of palladium and gold compounds, the total volume of which is from about 95% to about 100% of the absorptive capacity of the catalyst support and said precipitating step being carried out by soaking the wet catalyst support with a solution of an alkali metal silicate, the amount of alkali silicate being such that after the alkali metal silicate solution has been in contact with the catalyst support for about 12 to 24 hours the pH of said solution is from about 6.5 to about 9.5.

4 more elements