A novel dual-membrane reactor is proposed for heterogeneous catalysis over ultrafine catalyst particles. In this reactor, one tubular porous ceramic membrane is employed as a distributor controlling the supply of reactant, while the other is employed as a membrane separator for in situ separation of ultrafine catalysts from the products. To evaluate the feasibility and the performance of the dual-membrane reactor, phenol hydroxylation with hydrogen peroxide (H2O2) over TS-1 catalyst was selected as a model reaction. As compared to traditional H2O2 feeding modes, the use of the porous ceramic membrane distributor allows a uniform injection of H2O2 into the reaction system, and as a result significantly promotes the dihydroxybenzene selectivity. The phenol conversion and the DHB selectivity above 15% and about 95%, respectively, can be achieved in a continuous operation of 30 h. TS-1 catalysts can be retained almost completely in the reactor system by the membrane separator. Our study demonstrates the advantages of the novel dual-membrane reactor in enhancing selectivity and catalysts separation in a continuous heterogeneous catalytic reaction.