Variation in the selectivity of dehydrogenation and hydrogenation reactions was observed as a result of the conditions of hydrogen transfer from the zone of paraffin, olefin or cyclohexane dehydrogenation into the zone of diene hydrogenation through a hydrogen permeable membrane in the form of foil, thin-walled tube or a dense palladium alloy layer on the thermostable porous support. Industrial granular catalysts Pt-Re/Al2O3 and alumina-chromia were used for dehydrogenation, and hydrogenation was performed by palladium-containing membrane catalysts. The dependence of the selectivity of cyclopentadiene (CPD) hydrogenation into cyclopentene (CPE) was measured by an increase in the thickness from 20 to 80 nm of the palladium-ruthenium (Pd-Ru) alloy layer on the polydimethylsiloxane film which was inert towards CPD hydrogenation. Cyclopolyolefines C7-C12 of different structure differ in the rate of their reaction with hydrogen diffused through the membrane catalysts or mixed with the polyolefin. © 2001 Published by Elsevier Science B.V.