GB694354A - Oxidation of olefines - Google Patents

Abstract

In a process for the manufacture of unsaturated aldehydes olefines of the general formula <FORM:0694354/IV (b)/1> in which R is a hydrogen atom or alkyl group, are passed with molecular oxygen, with or without the admixture of inert gases, at temperatures of 180 DEG to 400 DEG C. in the presence in the reaction zone of elementary selenium over a contact material comprising the chromate, molybdate, sulphate, tungstate or vanadate of copper. The copper compounds may be distributed on a carrier such as pumice, asbestos, silica gel and alumina or may be formed into pellets. The elementary selenium may be added to the mixture of gaseous reactants as vapour, e.g. part or the whole of the olefine or olefine-oxygen mixture may be passed over heated selenium or it may be generated in situ by the decomposition of selenides, such as selenides of silver, antimony and cobalt, added to the contact mass containing the copper compounds. Alternatively elementary selenium may be mixed with the contact material before use. The molecular oxygen may be pure or commercial oxygen or air and the amount of olefine in the gas mixtures should be less than that corresponding to the lower explosion limit. Inert gases may be added such as carbon dioxide and steam and these may be removed by scrubbing with alkali or condensation respectively from the reaction mixture when it is desired to recycle unreacted olefine. In some cases the contact material may be given a preliminary heat treatment. The process may be carried out in a single pass or continuously when part of the gas is vented and the remainder is recirculated after replenishing the olefine and molecular oxygen. Unsaturated aldehydes produced by the process are recovered from the reaction mixture, e.g. by scrubbing with water. In examples propylene mixed with air is passed over heated selenium and then through a tube containing heated contact material which consists of (1) copper sulphate on alumina, (2) copper vanadate, (3) copper tungstate, (4) copper chromate and (5) copper molybdate, the material being formed into pellets in examples 2-5, graphite being added as lubricant in examples 2 and 3. By replacing propylene by isobutene or any other olefine of the defined structure the corresponding unsaturated aldehyde is obtained. Specifications 625,330, 648,386 and 655,210 are referred to.ALSO:In a process for the manufacture of unsaturated aldehydes by passing olefines of the general formula <FORM:0694354/III/1> in which R is a hydrogen atom or alkyl group, with molecular oxygen, with or without the admixture of inert gases, at temperatures of 180 DEG to 400 DEG C in the presence in the reaction zone of elementary selenium over a contact material comprising the chromate, molybdate, sulphate, tungstate or vanadate of copper. The copper compounds may be distributed on carriers such as pumice, asbestos, silica gel and alumina or where this presents difficulties, e.g. with the tungstate, vanadate or molybdate the copper compound may be made into pellets. Elementary selenium may be introduced into the reaction zone, e.g. by passing part or the whole of the mixed reactants or the olefine over heated selenium and thence to the reactor, it may be generated in situ by the addition of decomposable selenides, e.g. the selenides of silver, antimony and cobalt, to the contact material or elementary selenium may be added to the contact material. Heat treatment of the solid contact material may be employed when this can be applied without decomposition of the contact material. In examples: (1) activated alumina is treated with aqueous copper sulphate and dried (2) ammonium vanadate and copper sulphate are reacted in aqueous solution (3) copper tungstate is obtained from aqueous solutions of sodium tungstate and copper nitrate (4) copper chromate is obtained by adding copper carbonate to aqueous chromium trioxide and refluxing (5) copper molybdate is obtained from aqueous solutions of sodium molybdate and copper sulphate. The precipitate in examples (2)-(5) is washed, dried and after addition of graphite as lubricant in examples (2) and (3) is made into tablets or pellets. Propylene is mixed with air and the mixture passed over heated selenium and the heated contact materials in the examples to obtain acrolein. Isobutene and other olefines of the defined configuration are stated to be similarly oxidized to the corresponding unsaturated aldehydes (see Group IV(b)). Specifications 625,330, 648,386 and 655,210 are referred to.