Vapor Phase Catalytic Transformations of Terpene Hydrocarbons in the C10H16 Series. II. Aromatization of α-Pinene over Chromia–Alumina

Abstract

The aromatization of α-pinene in the vapor phase over chromia gel and chromia–alumina catalysts prepared from aluminas of different acidity has been studied. The acidity of alumina support has a remarkable influence on the composition of the aromatics resulting from the dehydrogenation of α-pinene. Over weakly acidic chromia–alumina doped with 1% sodium catalyst, α-pinene is aromatized to p-cymene, 1,2,4- and 1,2,3-trimethylbenzenes with traces of toluene and xylenes, whereas over the strongly acidic chromia – pure alumina and chromia–alumina containing 5% HF catalysts it gives considerable amount of m-cymene, toluene, and tetramethylbenzenes. A satisfactory mechanism to explain the formation of these compounds is offered.