GB671123A - Process for the catalytic partial oxidation of olefins containing at least three carbon atoms to unsaturated carbonylic compounds and the unsaturated carbonylic compounds so produced - Google Patents

Abstract

Unsaturated aldehydes or ketones are prepared by passing a gaseous mixture comprising an olefin of at least 3 carbon atoms and oxygen in contact with cuprous oxide, the activity of the catalyst being restored or maintained by periodically discontinuing or substantially decreasing the flow of olefin for a brief interval while subjecting the catalyst to a stream of oxygen or oxygen-containing gas, and then restoring the olefin flow. The oxidation is effected at about 150-650 DEG C. or more and desirably at 4-15 atmos. The activation of the catalyst is preferably effected at the same temperatures and pressures. The olefin feed may be cut off while the flow of other feed components including oxygen or air and, generally, an inert gas such as steam, nitrogen, carbon dioxide or methane is continued, if desired at an increased rate, or the entire feed may be diverted and replaced by an oxygen-containing gas. The time for activation may be a few minutes up to an hour, and the frequency may be once every hour up to 100 or more hours. The catalyst is desirably in fixed bed but moving bed or fluidized operation is possible. The oxygen content of the activating gas is generally above 3 and not over 35 per cent by volume. With higher oxygen content, a reduction with pure olefin or hydrogen may be desirable after the activation and before resuming the flow of reaction gas. Before or after activation, flushing with inert gas may be used. The oxygen concentration of the feed gases is preferably below the maximum at which mixtures of the olefin, inert gas, and oxygen form non-explosive mixtures at all values of the ratio between volume concentration of olefin and of inert gas, i.e. about 10 per cent for propylene and 11 per cent for isobutylene. In an example, a mixture of 30 per cent propylene, 37.5 per cent air, and 32.5 per cent steam is passed over cuprous oxide on silicon carbide at 375 DEG C. and 45 p.s.i.g. to yield acrolein. Periodic reactivation is effected with air or air and steam at about 385 DEG C. Specification 640,383 is referred to.