Article ID Journal Published Year Pages File Type
637142 Journal of Membrane Science 2009 12 Pages PDF
Abstract
Studies of the steam reforming of methane were carried out at high temperature (773-923 K) and pressure (0.1-2.0 MPa (1-20 atm)) using a commercial Ni/MgAl2O4 catalyst in a reactor equipped with a tubular hydrogen-selective silica-alumina membrane. The membrane was prepared using a chemical vapor deposition (CVD) method which gave a H2 permeance of 1.6 × 10−7 mol m−2 s−1 Pa−1 with a H2/CH4 selectivity of 710 at 923 K. Operation as a membrane reactor gave improved methane conversions and hydrogen yields compared to use as a packed-bed reactor at all temperatures and pressures. One-dimensional (1-D) and two-dimensional (2-D) models without adjustable parameters were developed to describe the performance of the two reactors. The 2-D model gave a slightly better fit to the membrane reactor results than the 1-D model, which predicted higher conversion at high pressure than observed experimentally. This was because the 2-D model correctly accounted for decreased permeant concentrations in the vicinity of the membrane (concentration polarization) which reduce the driving force for permeation and give lower conversions. A general criterion, denoted as the Order-Hierarchy Criterion, is developed for predicting when a 2-D model should be applied instead of a 1-D model for describing reactor performance. The 2-D description is necessary when both deviations from plug-flow behavior occur and when the rate of permeation > the rate of reaction, calculated at entrance conditions.
Related Topics
Physical Sciences and Engineering Chemical Engineering Filtration and Separation
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