Membrane Reactors for Green Synthesis

The chemical industries have been identified as the most important source of environmental contamination. Two critical processes in a chemical industry are separation and reaction. Membrane reactor [MR] field has been concentrated on novel membrane materials to be combined in a compressed structure. This kind of reactors can perform two roles: reaction and separation media. Subsequently, they are very useful to adjust concentrations of products and reactants. Membrane reactors, due to synergistically performing many operations, containing separation and reaction in one unit, are highly desirable in green synthesis and environmental protection. In the past three decades, there has been wide investigations in the green synthesis processes because of sustainable development, industrial safety and environmental worries, which makes green synthesis a promising substitute to the conventional synthesis methods. Promoting the efficiency of these green processes leads to the protection of the environment and personal safe. We reviewed several existing studies relevant to MRs for green synthesis applications. The MR can be applied in the synthesis of different components like ammonia, liquid fuels, methanol through reverse water gas shift reaction, enzyme synthesis using supercritical–ionic liquid system and reactions based on photocatalytic. Several parameters like operating temperature, pressure, feed flow rate in both side of MR, which affect the MR efficiency, are investigated. The MRs application for the synthesis green fuel including hydrogen and biofuels is reviewed. Then, the biocatalyst membrane reactor is introduced as a more effective reactor due to compactness and higher conversion, biocatalyst stability and activity. Finally, we focused on applications of photocatalyst MRs in wastewater treatment.