Intensification of ultra-lean catalytic combustion of methane in microreactors by boundary layer interruptions - A computational study

Oxidation of an ultra-lean mixture of methane and air over a platinum catalyst at the constant temperature of 1000 K is investigated numerically in several microreactor configurations featuring different hydrodynamics. These include a straight microchannel with the catalyst coated on the walls and a few wavy microchannels with continuous and discretised catalytic coating. The surface generated CO2 is selected as the indicator of catalytic activity and is evaluated along the catalytic surfaces and the outlet of reactor. It is shown that separation and reattachment of the boundary layer significantly alters the catalytic activity by modifying the structure of concentration boundary layer. Comparison of a strategically coated wavy microchannel with a straight microchannel, with accounting for the residence time, yields an increase of up to 400% in the production rate of CO2. It is argued that the observed hydrodynamic effects upon catalytic activities could help designing highly improved catalytic microreactors. (C) 2021 The Authors. Published by Elsevier Ltd.