Abstract A new process is proposed which converts CO2 and CH4 containing gas streams to synthesis gas, a mixture of CO and H2 via the catalytic reaction scheme of steam-carbon dioxide reforming of methane or the respective one of only carbon dioxide reforming of methane, in permeable (membrane) reactors. The membrane reformer (permreactor) can be made by reactive or inert materials such as metal alloys, microporous ceramics, glasses and composites which all are hydrogen permselective. The rejected CO reacts with steam and converted catalytically to CO2 and H2 via the water gas shift in a consecutive permreactor made by similar to the reformer materials and alternatively by high glass transition temperature polymers. Both permreactors can recover H2 in permeate by using metal membranes, and H2 rich mixtures by using ceramic, glass and composite type permselective membranes. H2 and CO2 can be recovered simultaneously in water gas shift step after steam condensation by using organic polymer membranes. Produc...