FREMGANGSMAADE TIL FREMSTILLING AF EN KATALYSATOR TIL OXIDATION AF SVOVLDIOXID TIL SVOVLTRIOXID

Catalysts for the oxidation of sulfur dioxide to sulfur trioxide, consisting of a silica-based carrier and, applied on this, an active substance containing vanadium and alkali metal compounds, are prepared by dissolving vanadium pentoxide in an alkali solution, acidifying the solution with sulfuric acid, mixing the acidified solution with the carrier, molding the mixture and drying and calcining the molding. To obtain mechanically stable catalysts, a dissolved alkali metal silicate and/or silica sol are added to the alkaline solution before acidification, the latter process is carried out at below 35 DEG C. and the solution is then immediately incorporated into the carrier. The resulting moist crumbly material contains from 2 to 6% by weight of V2O5, from 35 to 45% by weight of H2O and from 15 to 50% by weight of SiO2. From 5 to 25% by weight of the total silica content originates from the dissolved alkali metal silicate and/or silica sol.