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US 5,332,710 AGranted
Vinyl acetate catalyst preparation method
AssigneeHoechst Celanese Corporation
InventorsIoan Nicolau, Philip M. Colling, Leland R. Johnson
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AssigneeHoechst Celanese Corporation
InventorsIoan Nicolau, Philip M. Colling, Leland R. Johnson
Estimating the term…
A method of preparing a catalyst particularly useful in the reaction of ethylene, oxygen and acetic acid in the vapor phase to form vinyl acetate comprises impregnating a porous support with water soluble salts of palladium and gold, fixing the palladium and gold on the support as water insoluble compounds by immersing the impregnated support in a reactive solution and tumbling the impregnated support in the reactive solution for at least 1/2 hour to begin precipitation of the insoluble compounds and completing precipitation of the insoluble compounds on the support and reducing the insoluble compounds to free palladium and gold. The catalysts prepared in this manner have been shown to provide improvement with respect to reduced selectivity to CO.sub.2 during the vinyl acetate forming reaction.
In a method of preparing a catalyst composed of a porous support containing thereon precious metals which comprises impregnating said support with water soluble compounds of said precious metals, converting said water soluble precious metal compounds to water insoluble precious metal compounds by immersing said impregnated support in a fixing solution containing a compound reactive with said water soluble compounds to precipitate on said support said water insoluble precious metal compounds, washing said support, and reducing said water insoluble precious metal compounds with a reducing gas to form free precious metals on said support, the improvement which comprises tumbling said impregnated support by rotation at from about 1 to about 10 rpm at least 0.5 hour while said impregnated support is immersed in said fixing solution, thereby completing precipitation of said water insoluble compounds.
In a method of preparing a catalyst composed of a porous support containing thereon a mixture of palladium and gold which comprises impregnating said support with water soluble salts of said palladium and gold, converting said salts to insoluble palladium and glod hydroxides by immersing said impregnated support in an aqueous sodium or potassium hydroxide solution to precipitate said hydroxides, washing said supports to remove freed anions from said salts and reducing said hydroxides with a reducing gas to form free palladium and gold on said support, the improvement which comprises tumbling said support therein by rotation at about 1 to about 10 rpm for at least 0.5 hour while said impregnated support is immersed in said aqueous sodium or potassium hydroxide solution, to complete precipitation of said hydroxides.
In a method of preparing a catalyst composed of a porous support containing thereon a mixture of palladium and gold which comprises impregnating said support with water soluble chloride salts of said palladium and gold, converting said salts to water insoluble palladium and gold compounds by immersing said impregnated support in a solution containing an alkaline compound reactive with said salts to precipitate on said support said water insoluble compounds of said palladium and gold, washing said support to remove freed chloride ions and reducing said water insoluble compounds with a reducing gas to form free palladium and gold on said support, the improvement which comprises tumbling said support therein by rotation at about 1 to about 10 rmp for at least 0.5 hour while said impregnated support is immersed in said reactive solution, the volume of said reactive solution being about 50 to 500% the volume of said support and the alkaline compound being present in an amount such that the molar ratio of alkali metal of said alkaline compound to chloride anion of said salt equals from about 1.2:1 to 1.6:1, to complete precipitation of said water insoluble compounds.
Dependencies are inferred from the claim text.