CATALYTIC ALKYLATION OF PHENOL WITH METHANOL - FACTORS INFLUENCING ACTIVITIES AND SELECTIVITIES .2. EFFECT OF INTRACRYSTALLINE DIFFUSION AND SHAPE SELECTIVITY ON H-ZSM5 ZEOLITE

Six samples of H-ZSM5 zeolites, differing in the size of crystallites and acidity, have been tested as catalysts in the alkylation of phenol with methanol. We observed that the size of crystallites strongly influences activity, even for very small crystallites (220-280 Å), by the intervention of intracrystalline diffusion. Kinetic runs have been performed on the most active catalyst. A moderate shape selectivity has been observed only in the formation of p-methylanisole and xylenols. Catalyst deactivation occurs through two mechanisms which are independent of the contact time, the first evolving exponentially and the second linearly. The interpretation of this behaviour and of related consequences on the reaction is discussed in the paper together with the reaction path model, the mechanism and the kinetics. © 1990.