Dehydration of methanol and tert-butyl alcohol on silica-alumina

Abstract

The catalytic dehydration of tert-butyl alcohol and of methanol has been studied over silica-alumina. Both reactions obey the rate law, v=kap^½_a/(1 +ap^½_a+bp_w). Pyridine, Na⁺ and tetracyanoethylene poison the dehydration reactions. These results show that the reaction requires both acidic and basic sites. However, the dehydration of tert-butyl alcohol is much more sensitive to the presence of strongly acidic sites then the methanol dehydration. Alumina, which has a basic character, is more active than silica-alumina for methanol dehydration. These experimental results and those previously published in the literature accord with a conventional carbonium ion mechanism for the dehydration of tert-butyl alcohol. A new mechanism which involves a nucleophilic attack by the alcohol molecule is proposed for the dehydration of methanol.