GB808150A - Improvements in and relating to the oxidation of sulphur dioxide to sulphur trioxideand catalysts therefor - Google Patents

Abstract

Sulphur dioxide is oxidized to sulphur trioxide in the presence of a catalyst prepared by contacting a dissolved or suspended vanadium compound with an aqueous silicate solution, the materials being such that a precipitate is obtained containing a vanadium compound, silica, a sodium compound and a potassium compound, and then mixing the precipitate with kieselguhr to make the silica content of the final catalyst from 50 to 65 per cent by weight. The catalyst preferably contains by weight 5.5 to 8.0 per cent of potassium oxide, 1.25 to 1.75 per cent of sodium oxide, 3.5 to 7.5 per cent of vanadium pentoxide, and 52.5 to 62.5 per cent of silica. The initial vanadium compound may be vanadyl chloride, vanadyl oxalate, vanadyl sulphate or ammonium vanadate. A vanadyl sulphate solution may be added to a solution of potassium silicate and sodium silicate, or a solution of potassium hydroxide may be added to a vanadyl sulphate solution and the gelatinous suspension formed added to sodium silicate solution. The kieselguhr may be incorporated by adding a suspension of the precipitate in water to a suspension of kieselguhr in water. The catalyst is dried at 100 DEG to 120 DEG C. and then calcined at 300 DEG to 400 DEG C. Before calcining the dried catalyst may be wetted with a solution of sulphuric acid. Sulphur trioxide is obtained by contacting sulphur dioxide and free oxygen with the catalyst at a temperature of at least 380 DEG C. Examples are given.