PURPOSE: To obtain a catalytically active microporous membrane having resistance to poison by rendering the reaction into heterogeneously catalyzed reaction and adding one kind of other catalytically active components as a component to form a continuous membrane permeable to one kind of reactant separated by this membrane.

CONSTITUTION: The catalytically active microporous membrane used for heterogeneously catalyzed reaction has resistance to poison if the membrane permeates only one kind of reactant separated from the membrane but it does not permeate a reactant of a larger molecular size and impurities. By using this membrane, three-phase reaction can be performed by a new method, and the reaction gas can be transferred directly to the active sites. In the membrane, ≥60 wt.% of the membrane is made of SiO2, TiO2 or the like or a mixture of these. The catalytically active component consists of Pt, Pd, Ni in an oxidizing or reducing catalytically active form or precursors of these and is incorporated by <10 wt.% into the membrane. The membrane is produced by a sol-gel method and activated by a normal method.