We have developed an MEMS-based Pd membrane microreactor for one-step conversion of benzene to phenol, and also evaluated the H-2 permeation characteristics through the Pd membrane before the benzene hydroxylation experiments. The conversion of benzene, selectivity and yield of phenol were investigated by varying the operation conditions. The phenol yield of 20% and benzene conversion of 54% were obtained at a reaction temperature of 200 degrees C. The phenol and dihydric phenols dominated the distribution of products and the hydrogenation products of from benzene and phenol were absent in the MEMS-based Pd membrane microreactor, which was very different from the macrotubular Pd membrane reactors. The effect of H-2/O-2 ratio on products distribution has been investigated. From the comparison of reaction results with a macrotubular Pd membrane reactor, it is figured out that the Pd membrane microreactors fabricated by MEMS technology gave a higher reaction conversion and product yield. (C) 2009 Elsevier B.V. All rights reserved.