To form membranes with catalytic effectiveness in hydrogenation nano-sized palladium clusters were incorporated in polymeric membranes made from poly(ether-b-amide) (PEBA) mainly by a solution-casting method. Several configurations of the Pd in the membrane were tested to optimise the catalytic activity: homogeneously distributed in PEBA, homogeneously distributed in PEBA/poly(vinylpyrrolidone) (PVP) blend, homogeneously distributed in PEBA/PVP blend with silica filler, two-layer configuration, and surface coated PEBA-membranes. The membranes were characterised by SEM, XRD and pervaporation flux density. The catalytic activity was tested in the pervaporative membrane reactor by hydrodechlorination of chlorophenol and chlorobenzene in diluted aqueous solution saturated by hydrogen at 30 degreesC. The produced hydrochloric acid is proportional to the reaction and detected exclusively in the feed. The decrease of the feed-pH was used to monitor the reaction progress of chlorophenol hydrodehalogenation online. Alternatively, the hydrodehalogenation of chlorobenzene was traced by head space gas chromatography. An essential improvement of the homogeneous PEBA-membranes resulted in blending with PVP and adding silica filler. The calculated activity per gram of Pd in the hydrodechlorination of 4-chlorophenol increased about four times and an about two times higher conversion was detected, both at an even lower Pd content. The two-layered membranes at similar overall Pd content demonstrated about two times higher activity and conversion per time to related membranes with homogeneously partitioned Pd-nanoclusters. Surface coated membranes with a porous Pd-layer interconnected to the PEBA-membrane showed only at high Pd content a performance related to simple homogeneous membranes. (C) 2004 Elsevier B.V. All rights reserved.