GB833577A - Process for the manufacture of catalysts - Google Patents

Abstract

A promoted chromia-alumina catalyst is prepared by (1) reacting aluminium sulphate or aluminium ammonium sulphate with an alkaline precipitant (preferably an aqueous solution of (a) ammonia or (b) sodium aluminate) under conditions effective to form a substantially granular hydrogel precipitate; (2) optionally washing the precipitate; (3) transforming it into a gel, preferably by passing through a colloid mill, particularly wherein the apertures are between 0.001 and 0.005 inch; (4) spray drying the gel under conditions effective to produce microspheroids of relatively uniform size distribution (preferably a chamber spray drier of the rotating disc type is used); (5) washing the product if stage (2) was omitted, preferably with dilute aqueous ammonia and particularly subsequently with water; (6) roasting the dried product at 500-700 DEG C., preferably 600 DEG C.; (7) impregnating with an aqueous solution comprising a compound of chromium and either a compound each of cerium (the technical material containing other lanthanons may be used) and potassium or a compound of iron, nickel or cobalt; (8) separating the impregnated product from any superfluous impregnating solution; and (9) calcinating the impregnated product to decompose the compounds of the active elements into their oxides, preferably at approximately 550 DEG C. For stage (7), one of the following alternatives is preferred:-either the impregnating solution comprises chromic acid and copperas, or the product of the roasting stage is introduced into an aqueous solution containing chromic acid, cerous nitrate and potassium nitrate.