Multi-component mass transfer behavior in catalytic membrane reactors

•Comparison membrane reactors for different equilibrium reaction characteristics.•Membrane reactors with catalyst confined on membrane surface or dispersed in bulk.•Implications of multi-component mass transport on membrane reactor performance.•Design directions for membrane reactors.•Guidelines for optimal operation of membrane reactors.

Numerical simulations are presented to compare mass transfer at the bulk fluid-membrane interface of two types of membrane reactors, for arbitrary equilibrium reactions: the catalytic membrane reactor (CMR) in which the location of the reaction and separation coincide, and the inert membrane reactor (IMR) in which locations of reaction and separation distinct. The Maxwell–Stefan theory is adopted to describe this multi-component mass transport and to take friction between the species in the reaction mixture into account. Simulation results are presented that aid selection of the most appropriate reactor configuration for different reaction equilibrium characteristics. Effects of process conditions, membrane properties, and possibilities to optimize reactor design are discussed.Three regimes can be distinguished, based on the value of reaction equilibrium constant (Keq). At very low Keq, the CMR outperforms the IMR, and in particular a high membrane area/reactor volume ratio (A/V), a high product permeance, and a large residence time are required. At moderate Keq, the CMR potentially outperforms the IMR, and conversion benefits in particular from a high A/V ratio and sufficiently high mass transfer. For high Keq the performance of the IMR is superior as compared to the CMR.The simulation results indicate that, in particular for the CMR, a mass transport description that can properly address multi-component mass transport characteristics is vital. The results predicted based the Maxwell–Stefan theory will not be captured adequately by a model based on, for instance, the law of Fick.

Graphical abstractComparison between catalytic membrane reactor (CMR) and inert membrane reactor (IMR) for multi-component mass transfer behavior.Figure optionsDownload full-size imageDownload high-quality image (131 K)Download as PowerPoint slide