Catalyst activity control in process for converting an alkene to a carbonyl derivative in the presence of a noble metal and redox agent

摘要

In converting an alkene such as ethylene to a carbonyl derivative such as acetaldehyde by a process which comprises passing the alkene through a tubular reactor along with an aqueous acidic catalyst solution comprising a noble metal such as palladium together with a cupric chloride redox agent, followed by separating the carbonyl product from the depleted catalyst solution which is then reoxidized with a source of molecular oxygen such as air prior to being returned to the reactor, continuous depletion of the chloride content of the catalyst solution takes place as a result of the formation of chlorinated reaction by-products. This necessitates replenishment of the chloride content of the catalyst solution by adding hydrochloric acid into a catalyst regeneration zone preceding the catalyst reoxidation step of the process. Over-treating or under-treating with the hydrochloric acid results, however, in occasional process upsets and failure to maintain optimal activity of the catalyst solution and maximum reactor output. The present invention comprises maintaining optimal catalyst activity by adding hydrochloric acid in response to the hydraulic pressure gradient obtaining within the alkene- oxidation reactor, within which a deficiency of acid causes an increasing hydraulic pressure gradient due to fouling of the tubular reactor with precipitated solids. Optimal catalyst activity obtains when the acid addition rate is just sufficient to prevent the inception of a pressure gradient rise due to precipitation of solids within the reactor.