Membrane microreactors for catalytic reactions

Abstract

Membrane microreactors (MMRs) combine the advantages of membrane separation and microreactors such as high area/volume ratio, enhanced mass and/or heat transfer, improved catalytic efficiency without equilibrium limitation, good operational safety and design flexibility. This article presents a short review of recent developments in MMRs and in particular highlights their applications in catalytic processing. The structure and fabrication of MMRs, the incorporation of catalysts with membranes, the flow characteristics as well as their applications in a variety of catalytic processes are presented. The prospects and challenges of MMRs in catalytic processing are also presented and discussed. © 2013 Society of Chemical Industry

Single-stage hydrogen production and separation from fossil fuels using micro- and macromembrane reactors

“…(3) intensification of process owing to the integration of different steps in a small-scale device; (4) enhancement of surface area to volume ratio owing to extremely high intensification; (5) high reactant conversion or low reaction temperature owing to thermodynamic equilibrium shifting resulting from the removal of specified products from reacted mixture; and (6) high selectivity of the achieved product owing to optimized reactant distribution resulting from the addition of specified reactants in a controllable way (Alfadhel & Kothare, 2005;Gallucci, Fernandez, Corengia, & Van Sint Annaland, 2013;Jensen, 1999;Kim, Kellogg, Livaich, & Wilhite, 2009;Kolb, 2013;Kothare, 2006;Tan & Li, 2013). Among versatile MMRs, those with a hydrogen separation function are being investigated and have found a number of applications such as hydrogen production from WGS, hydrogen production from methanol steam reforming (MeOHSR), onboard fuel processing for portable PEMFCs, production of moisture-free formaldehyde by the dehydrogenation of methanol, and dehydrogenation of cyclohexane to benzene (Alfadhel & Kothare, 2005;Allen, Irving, & Thomson, 2000;Franz, Schmidt, & Jensen, 1999;Karnik, Hatalis, & Kothare, 2003;Mauer, Claivaz, Fichtner, Schubet, & Renken, 2000;Zheng, Jones, Fang, & Cui, 2000).…”

“…Catalysts can be coated on the inner surface of hollow fibers or impregnated in the porous wall, whereas separation can be achieved via the porous hollow fibers themselves or through the membrane formed on the outer surface of the hollow fibers. This kind of hollow-fiber MR can also be attributed to MMRs, called hollow-fiber MMRs (Tan & Li, 2013). Hollow-fiber MMRs were investigated in detail for hydrogen production in Li's group (Garía-García & Li, 2013;García-García, Rahman, & Gonz alez-Jiménez, 2011;García-García, Rahman, Kingsbury, & Li, 2010;Rahman, García-García, Irfan Hatim, Kingsbury, & Li, 2011;Rahman, García-García, & Li, 2012;Tan & Li, 2013).…”

Continuous flow ZIF-8/NaA composite membrane microreactor for efficient Knoevenagel condensation

“…This is largely driven by the development of flow chemistry and the advantages associated with microreactors compared with traditional batch reactors based on protocols such as, improved efficiency, rapid mass and heat transfer rates, use of supported reagents and reduced reaction time [3][4][5]. Membrane microreactor (MMR), fabricated by assembling membranes/films in a microreactor, significantly expands the applications of microreactor technology, especially in heterogeneous catalysis [6,7]. The utilization of MMR in a reaction system can realize catalyst immobilization, large contact area between reactants and catalyst, optimal axial concentration profiles, supra-equilibrium conversions and improved product purity.…”

Microscale technology and biocatalytic processes: opportunities and challenges for synthesis

“…Product removal/product isolation The high surface-to-volume ratio of microscale reactors is of extreme value for integrated product removal (ISPR) (see Glossary) using either membranes [24] or two-liquid flow for in situ extraction [25][26][27], which among other factors enable improved catalytic efficiency overcoming thermodynamic limitations, enhanced product purity and prevention of catalyst poisoning, and deactivation by removing undesirable byproducts from the reaction zone. Membranes are integrated within microchannels either to achieve product separation or as a catalyst support.…”

“…Membranes are integrated within microchannels either to achieve product separation or as a catalyst support. They could be made from various materials including zeolites, carbon nanofibers, metals, nylon, polytetrafluoroethylene (PTFE), ceramics, or thin layers of ionic liquids acting as selective media for separation [24].…”