Highly enhanced phenol hydroxylation in [h0h]-oriented Fe-ZSM-5 membranes

Abstract

Catechol (CAT) and hydroquinone (HQ) are two important diphenol isomers with a variety of industrial applications. The hydroxylation of phenol catalyzed by transition metal (TM) substituted ZSM-5 is an environmentally benign route for diphenol production, which is usually governed by intracrystalline diffusion. Therefore, the availability of highly oriented TM-ZSM-5 membranes and their utilization in an interphase membrane reactor can significantly promote the hydroxylation of phenol. The continuous and [h0h]-oriented Fe-ZSM-5 membrane on the porous α-Al2O3 was prepared using a new seeded growth method. Characterization was carried out by using SEM, XRD, UV/Vis, and EPMA techniques, which demonstrated that the [h0h]-oriented membrane consists of Fe substituted ZSM-5 crystal grains with an Si/Fe ratio of approximately 75. Compared with the catalytic performance of different sized Fe- ZSM-5 grains loaded in the traditional slurry reactor, the [h0h]- oriented Fe-ZSM-5 membrane in the interphase membrane reactor showed significantly improved phenol conversion and selectivity for CAT and HQ due to the molecular path control in the zeolite membranes. © 2009 Wiley-VCH Verlag GmbH& Co. KGaA, Weinheim.