GB948012A - Catalysts - Google Patents

Abstract

The process of the parent Specification in which a silica-alumina catalyst is made by reacting an aqueous alkali metal silicate solution with CO2 in amount sufficient to form a silica hydrogel containing dissolved alkali metal carbonate and then commingling the hydrogel with an aqueous solution of an aluminium salt of a strong mineral acid whereby alumina is precipitated from the aluminium salt solution in and on the hydrogel and is washed and dried is modified in that a slurried mass of an alkali metal silicate solution having a silica to alkali metal ratio of about 3 : 1-3,4 : 1 is provided and contacted with carbon dioxide in an amount sufficient to convert substantially all of the free alkali in the silicate to alkali metal carbonate and form a silica hydrogel containing dissolved carbonate, the resulting mass is commingled with a solution of an aluminium salt of a strong mineral acid, in an amount sufficient to provide up to 40% active alumina in the synthetic component of the finished catalyst and to react substantially completely with the residual carbonate, there being added if necessary a basic precipitant to the slurry to complete precipitation of the alumina, the product being filtered, purified and dried, with the proviso that clay may be added to the reaction materials at any stage during the process in a proportion constituting at most 50% by weight of the final product. Preferably the alkali metal salt is sodium silicate, the aluminium salt is alum and the clay is kaolin. Comparative examples are given.