Catalyst for vinyl acetate production from ethylene, acetic acid and oxygen contains palladium and other metals on a pyrogenic mixed oxide support based on silicon, aluminum, titanium and/or zirconium oxide

摘要

Pyrogenic mixed oxides with specified properties based on at least two of the components from aluminum oxide and silicon, titanium or zirconium dioxides, except for SiO2/Al2O3 systems with more than 75 wt.% SiO2, are used as support materials for catalysts based on palladium and alkali compounds plus gold and/or cadmium and/or barium. Supported catalysts in which the active components are palladium and/or Pd compounds and alkali compounds plus gold (Pd/alkali/Au system) or cadmium (Pd/alkali/Cd system) or barium (Pd/alkali/Ba system), or Pd, alkali compounds and mixtures of Au and/or Cd and/or Ba. The support materials for these catalysts comprise pyrogenic mixed oxides with any combination of at least 2 components selected from SiO2, Al2O3, TiO2 and ZrO2 and containing less than 1 wt.% other components, except for SiO2-Al2O3 mixed oxides with more than 75 wt.% SiO2. The pelleted support materials show a bulk density of 250-1500 g/l, an outside diameter of 0.8-25 mm, a BET surface of 5-400 m2/g, a pore volume of 0.2-1.8 ml/g and a breaking strength of 5-350 N. Independent claims are also included for: (a) a process for the production of catalysts from mixed oxide pellets as described, by impregnation, spraying, vapor deposition, dip-treatment or precipitation with Pd, Au, Cd and/or Ba compounds, optional reduction of reducible metal compounds, washing to remove any chloride, and impregnation with alkali acetate or with alkali compounds which are converted into acetate under the conditions used for vinyl acetate monomer production; (b) an alternative process involving impregnation of the support with a basic solution and a solution containing Au and Pd salts, washing to remove chloride, reduction of precipitated compounds, drying and impregnation with alkali acetate etc. as in (a).