Selective oxidation of aromatic compounds on zeolites using N2O as a mild oxidant - A new approach to design active sites

Dehydroxylated ZSM-5 type zeolites are used for selective oxidation of arom atic compounds, including benzene, chlorobenzene, styrene, difluorobenzenes , phenol, alkylbenzenes into corresponding phenols and diphenols using nitr ous oxide as a mild oxidant. In the case of benzene, the yield of phenol re aches 70-80%. Extremely high selectivity (similar to 98-100%) in the case o f benzene and similar to 85% in the case of difluorobenzenes and high regio selectivities are observed on the dehydroxylated HZSM-5 zeolite. The active sites are shown to be the strong Lewis acid-base pair sites formed upon de hydroxylation of the zeolites. The reaction mechanism that is alternative t o the proposed iron-mediated mechanism is discussed. (C) 2000 Published by Elsevier Science B.V.