Patent GB-1247386-A (GB)
Title: Process for the vapour-phase oxidation of lower olefins
IPC: B01J27/057
Filed: 1968-09-09
Abstract: 1,247,386. Oxidation catalysts. TOA GOSEI CHEMICAL INDUSTRY CO. Ltd. 9 Sept., 1968 [19 Dec., 1967], No. 42852/68. Heading B1E. [Also in Division C2] A catalyst comprising chromium, molybdenum and tellurium in relative proportions such that the atom percentages of chromium, molybdenum and tellurium, calculated as percentages of the total number of atoms of chromium, molybdenum and tellurium present in the catalyst, are 5 to 39, 51 to 94.5 and 0.5 to 10, respectively, is prepared by a process which comprises either preparing a mixed aqueous solution containing a compound of trivalent chromium, molybdic acid or a salt thereof and telluric acid or a salt thereof, drying the solution to form a deposit and calcining the deposit or preparing a mixed aqueous solution containing a compound, of trivalent chromium and molybdic acid or a salt thereof, drying the solution to form a deposit, impregnating the deposit with a solution of telluric acid or a salt thereof and calcining the impregnated deposit. Calcining may be effected at a temperature of from 430 to 550C in the presence of molecular oxygen, for example in air. If chromium and molybdenum are deposited in the absence of tellurium, the mixed aqueous solution may contain ammonia or an organic amine, for example ethanolamine, in an amount such that the pH of the solution is higher than 3 (but preferably not higher than 8) and the deposit comprising chromium and molybdenum may be calcined before being impregnated with the solution of telluric acid or salt thereof. The mixed aqueous solution comprising chromium and molybdenum or chromium, molybdenum and tellurium additionally may contain a water-soluble compound of at least one additional element selected from calcium, cadmium, aluminium, iron, cobalt and nickel, the amount of additional element or elements being such that the total content thereof in the catalyst will be from 0.01 to 0.5 atom per atom of molybdenum present in the catalyst, and/or porous solid carrier material whereby the deposit is deposited on to the carrier material thereby to provide a supported catalyst. The carrier material may be spongy aluminium, spongy titanium (see Example 2), alumina, silica (see Examples 15, 16, 17, 18), zirconia, diatomaceous earth or silicon carbide. If the deposit is deposited on to carrier material, the compound of trivalent chromium may be replaced by a compound of hexavalent chromium and a reducing agent capable of reducing hexavalent chromium to trivalent chromium; the reducing agent may be an amine, aldehyde, ketoacid or glycol, for example ethanolamine, triethanolamine, ethylenediamine, glyoxylic acid, ketogluteric acid, glyoxal, ethylene glycol or ammonium glutamate. The compound of trivalent chromium may be the nitrate, chloride, sulphate or acetate; the compound of hexavalent chromium may be ammonium chromate, potassium chromate or ammonium dichromate. The salt of molybdic acid may be ammonium or sodium or potassium molybdate; the salt of telluric acid may be sodium or potassium tellurate. In general, water-soluble oxides, hydroxides, halogenated compounds, inorganic salts and organic salts of chromium and of the additional element or elements may be used. The catalyst is used in the oxidation of a lower olefin,. for example propylene or isobutylene, to the corresponding unsaturated aldehyde.