Membrane Reactors for Hydrogen Generation: from Single Stage to Integrated Systems

The excessive production of carbon dioxide, the greenhouse effect, and the resulting global warming due to the use of fossil fuels have prompted governments, industry, and researchers toward renewable and clean energy sources. Hydrogen has emerged as a novel carbon neutral energy carrier with the highest specific energy content. Production, storage, distribution, and utilization of hydrogen are rapidly increasing. In this context, the use of hydrogen in power plants, fuel cells and internal combustion engines is constantly being developed. However, widespread use of hydrogen requires its sustainable production at low cost and under high purity conditions, which is the subject of further research. Hydrogen separation using membrane reactors is not a new concept; however, it has gained special attention in the last decades and represents a relevant and promising option to potentially overcome the above mentioned problems. This review examines advances in industry and research in hydrogen utilization, hydrogen production using membrane reactors, the nature and physicochemical properties of membranes, and the various configurations of membrane reactors. The effects of membrane reactors on the interplay of temperature, pressure, reactant conversion, hydrogen production, and thermodynamic equilibrium are explained, and the results are compared with those of conventional reactors. Finally, fuel cells, solar collectors, and their integrability into membrane reactors are discussed.