Catalytic dehydration of alcohols over alumina Mechanism of ether formation

Abstract

The dehydration of alcohols over alumina to form ethers and olefins was studied from a mechanistic point of view. The rates of both olefin formation and ether formation were independent of the partial pressure of the alcohol, beyond a certain partial pressure. This saturation partial pressure was higher for ether formation than for olefin formation. The conclusion was drawn that both reactions are surface reactions but requiring different types of active sites. Certain reagents, like phenol, when added to the alcohol in small quantities, caused a large increase in the rate of olefin formation and a large decrease in the rate of ether formation. Certain other reagents like pyridine caused decrease in the rates of both ether formation and olefin formation. An explanation is offered for the above observations assuming the presence of both acidic and basic sites on the surface of alumina.