Study on methanol reforming-inorganic membrane reactors combined with water-gas shift reaction and relationship between membrane performance and methanol conversion

When a methanol reforming-membrane reactor is employed as a hydrogen generator for proton exchange membrane fuel cell (PEMFC), three important aims should be simultaneously achieved in one process, which are methanol conversion improvement, high hydrogen recovery, and high CO removal efficiency. To achieve the aims, we investigated five different configurations of a membrane reactor (a methanol reforming-microporous membrane (MMi) reactor, methanol reforming-mesoporous membrane (MMe) reactor, methanol reforming-mesoporous membrane-water-gas shift (MMeW) reactor, methanol reforming-macroporous membrane (MMa) reactor and methanol reforming-macroporous membrane-water-gas shift (MMaW) reactor). As a result, the MMi reactor was not suitable for a hydrogen carrier of PEMFC due to low hydrogen recovery. The MMe and MMa reactor showed low CO removal efficiency due to low permselectivity of the mesoporous and macroporous membrane. In contrast, the MMeW and MMaW reactor gave simultaneously methanol conversion improvement, high hydrogen recovery, and high CO removal efficiency in one process. The low CO removal efficiency due to low permselectivity of the mesoporous and macroporous membrane was significantly enhanced by the water-gas shift reaction in the permeate side of the MMeW and MMaW reactor. In addition, based on the reaction results in the MMi, MMe and MMa reactor, it was confirmed that methanol conversion in a membrane reactor system is higher as a membrane used in a membrane reactor has higher total permeance difference (Sigma permeance of products - Sigma permeance of reactants). (C) 2008 Elsevier B.V. All rights reserved.