Catalytic transformation of 2-phenylethanol over alumina based catalysts

Abstract

This investigation involves the dehydration of 2-phenyl ethanol to styrene over aluminas prepared from different sources, aluminas modified by alkali and alkaline earth metal and fluoride ions and also over silica-alumina catalysts of varying silica-alumina compositions in the temperature range 275-500^oC, in a vertical flow reactor. It is found that alumina prepared from aluminiumisopropoxide is more reactive than the other catalysts for the selective dehydration of 2-phenylethanol to styrene. Using this alumina, the effects of alkali, alkaline earth metal, fluoride ions and partial pressure of water vapour have been investigated on the overall conversion of 2-phenylethanol and on the product distribution. Presence of alkali and alkaline earth metal ions minimises the undesired side reactions while water vapour in addition, enhances the yield of styrene. Over fluorided alumina, formation of styrene is maximum when fluoride content is below 2.0%. Silica-alumina catalyses dehydrogenation and cracking-reactions. The dehydration process follows first order kinetics and the kinetic and thermodynamic parameters are reported.