Process for the catalytic oxidation of olefins in the presence of cuprous oxide to form unsaturated aldehydes and ketones and the aldehydes and ketones so formed

摘要

In the production of unsaturated aldehydes or ketones by oxidation of olefins of at least 3 carbon atoms in the vapour phase in the presence of a cuprous oxide catalyst with recycling of unreacted material, the carbon monoxide content of the recycled material is reduced to maintain the content of the mixture fed to the catalyst at below that at which substantial decrease in catalytic activity results. Carbon monoxide is formed as a by-product and builds up under cyclic conditions of operation. It is removed to give a content of less than 0.5, preferably less than 0.2 per cent by volume, in the reaction mixture. Where the fresh feed has a carbon monoxide content in excess of this figure, it is necessary to reduce it prior to reaction. The olefins specified range from propylene to octenes, and include cyclo-olefins, and homologues and substitution derivatives thereof. Propylene may be converted to acrolein, isobutylene to methacrolein, a - or b -butylene to methyl vinyl ketone, 1- or 2-pentene to ethyl vinyl ketone and/or 3-pentene-2-one, 2 - methyl - 2 - butene to methyl isopropenyl ketone, and cyclopentene to 2-cyclopentene-1-one. The cuprous oxide is preferably used with a carrier such as silica gel, silicon carbide or pumice and may be in fluidized form. Reaction temperatures are about 200-450 DEG or up to 600 DEG C., and apparent contact times about 0.1-10 seconds. Molar ratio of olefin to oxygen is from about 1 : 1 to 30 : 1, and diluents such as steam or nitrogen may be present. After separation of the carbonylic product, the unreacted olefin may be scrubbed with a selective solvent such as kerosene, gasoline, an ester or ketone, the unabsorbed gases vented, and the olefin stripped from the solution and recycled. Alternatively, the olefin, after adding further oxygen if required, is passed over a catalyst promoting selective oxidation of CO to CO2, e.g. "Hopcalite" catalysts comprising MnO2, Cu2O and, if desired, CO2O3 and Ag2O. The CO2 may be returned with the olefin or removed with alkali. Oxidation of the CO with steam in the presence of iron oxide, reduction with hydrogen in the presence of Ni, Co, Pt or Fe, and rmeoval by an adsorbent or absorbent, e.g. acidic cuprous chloride solution, are other methods referred to. Specification 640,383 is referred to.