The feasibility of harnessing the increase in moles in certain equilibrium-limited reactions to alleviate the pressure driving force requirement for permeation through membranes is demonstrated. The studies are conducted in a packed-bed membrane reactor operated as a semi-batch membrane reactor (SBMR) to capture the pressure generating potential of the reaction. The actual system investigated is the steam methane reforming, a reaction in which the number of moles doubles, carried out at various temperatures (873 K and 923 K) and pressures (0.5–1.5 MPa) with a Ni/MgAl2O4 catalyst. A silica-alumina membrane with a hydrogen permeance of 2.2 × 10−7 mol m−2 s−1 Pa−1 at 923 K prepared by chemical vapor deposition was used in the membrane reactor. The hydrogen productivities obtained in the SBMR were compared with the productivities obtained in a membrane reactor operated at the same conditions. At low pressures (0.5, 1.0 MPa) the hydrogen productivities of the SBMR were comparable to those obtained with the continuous membrane reactor, but at high pressure (1.5 MPa) the SBMR showed superior performance. One-dimensional modeling studies gave good agreement between simulated and experimental results obtained from both reactor types. Based on these calculations, further estimations on hydrogen productivities were made at high pressures. These results indicated that the SBMR improved the hydrogen production when the steam methane reforming was conducted above 1.5 MPa. The SBMR described here could be utilized in a system where multiple units would be arranged to undertake parallel filling and discharge operations, much akin to the arrangement used in a pressure swing adsorption system.
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