Patent GB-348669-A (GB)
Title: Contact sulphuric acid process
IPC: C01B17/79
Filed: 1929-12-16
Abstract: The catalytic oxidation of sulphur dioxide to sulphur trioxide is effected with the use, as catalyst, of a diluted or undiluted non-base exchanging silicate or polysilicate of a catalytically active metal element which has been prepared in solutions within the range between neutrality and slight acidity to litmus. Silicates of metals of the platinum group, of groups V and VI of the periodic table and particularly of tetravalent vanadium, of iron and manganese, and of any of the catalytic metals referred to in Specifications 286,708 and 296,048, [both in Class 1 (i), Chemical processes &c.], may be used. Diluents comprise materials rich in silica such as kieselguhr, pumice meal, glaucosil, catalytically active or inactive siliceous or non-siliceous base-exchange bodies or their derivatives, and they may be introduced by any of the nine methods described in Specification 286,708, [Class 1 (i), Chemical processes &c.]. Easily decomposable complex compounds such as ammonia or cyanogen complexes or diluents such as starch or stearic acid which may be readily removed or destroyed by heating or leaching may also be introduced. In preparing the catalysts reaction may be effected between a soluble silicate and one or more metallates or metal salts, or both metallates and metal salts may be used, and the mechanical strength of the product may be increased by washing with waterglass, whilst alkali or alkaline-earth metal compounds may be used as cementing means and to tone the catalyst. Examples relate to the preparation of a vanadyl polysilicate diluted or not with "Celite" earth or with base-exchanging bodies, the earth, if desired, being impregnated with aluminium vanadate, copper vanadate, silver vanadate or tungstate; of a complex silicate of vanadium and aluminium, titanium, zirconium, thorium, zinc, cadmium, copper, silver, chromium, iron, cobalt, nickel, cerium, platinum, or bismuth diluted with glaucosil etc.; of a complex silicate of vanadium, copper aluminium, and iron diluted with infusorial earth, with or without tungsten, tantalum, or molybdenum; of a complex silicate of vanadium and aluminium, tungsten, molybdenum, lead, zinc, or cadmium, diluted with materials rich in silica including natural and artificial zeolites, the diluents being treated with iron, titanium, or copper oxide; of a vanadyl silicate diluted with a siliceous base-exchanging body containing vanadium and aluminium and with diatomaceous earth; of a complex silicate containing vanadium, aluminium, and tungsten diluted with "Celite" earth; of a silicate containing pentavalent and tetravalent titanium diluted with materials rich in silica which may have been impregnated with iron, nickel, silver, copper, cobalt, or aluminium oxide, or with heavy metal vanadates, molybdates, tungstates, chromates, or tantalates; and of a complex silicate of vanadium diluted with catalytically active or inactive base-exchange bodies or their salt-like or acid-leached derivatives. The silicates may also be coated on to massive carrier fragments comprising quartz fragments, silica gel fragments, fragments of natural or artificial silicates or other siliceous materials including base-exchange bodies, metal granules of aluminium, ferrosilicon, ferrovanadium, or ferrochrome.  Adhesives such as waterglass or alkali metal salts may be used, or the surfaces of the carrier be roughened as by etching with hydrofluoric acid, and the previously formed silicate may be applied as a coating or formation thereof be effected in situ.  A diluted or undiluted silicate containing iron, aluminium and platinum may be coated on to such carriers. Specification 290,316, [Class 1 (i) Chemical processes &c.], also is referred to.  Reference has been directed by the Comptroller to Specifications 159,508, 286,212, 286,708, 294,975, 298,142 and 314,858, [all in Class 1 (i), Chemical processes &c.].