Improvements in and relating to the oxidation of sulphur dioxide to sulphur trioxideand catalysts therefor

Catalysts suitable for the oxidation of sulphur dioxide to sulphur trioxide are produced by forming a silica gel containing Na+ and K+ ions from an aqueous Na-K silicate solution and incorporating in the gel a vanadium compound substantially the whole product being dried by heating and thereafter more strongly heated, the compositions and proportions of the reactants being chosen so that the finished catalyst comprises, by weight, 6-10% V2O5, 6-15% K2O, 1,5-6% Na2O and 10-30% SO3. Additional silica, e.g. in the form of kieselguhr, may be incorporated in the catalyst, preferably before the gelling stage.