Modelling of the interaction of kinetics and external transport phenomena in structured catalysts: The effect of reaction kinetics, mass transfer and channel size distribution in solid foams

The increasing use of structured reactors and catalysts, particularly solid open foams requires a new touch to the interaction of intrinsic chemical kinetics and mass transfer. In spite that the internal mass transfer resistance in the catalyst pores is efficiently suppressed because of thin washcoat layers on structured catalysts, the low flow velocities applied in many liquid-phase processes impair the mass transfer efficiency at the outer surface of the catalyst layer inside the channels of monoliths and open foams. The coupling of external mass transfer resistance and intrinsic kinetics was considered for various power-law and adsorption kinetics in tubular reactors filled with structural catalysts. The relevant mass balance equations were derived and solved numerically and the behaviors of single-channel systems were illustrated in the parameter spaces of Damköhler numbers. The single-channel model was successfully extended to a system of parallel channels with a distribution of channel sizes. The effect of the channel size distribution on the Reynolds and Sherwood numbers was illustrated by numerical simulations. The proposed approach is a potential tool for the design of structured catalysts.