Viscous flow effects in the periodic pressure cycling of gas-phase catalytic reactions

Abstract

The previous study of Hamer and Cormack[1], on the increased effectiveness of gas phase catalytic reactions under conditions of oscillating external pressure, is extended to include viscous flow effects. For this purpose, the full, time dependent equations of viscous flow, diffusion and chemical reaction for a first order, isothermal reaction in a porous catalyst are solved numerically. The inclusion of viscous effects results in a new dimensionless parameter, N. It is shown that in general the catalyst effectiveness factor is smaller for smaller N. It is concluded, however, that even though viscous effects might be very important for extremely low permeability catalysts, viscous effects can be neglected for operating conditions such that N > 1. For one example cited this corresponds to a permeability of 0.2 millidarcy.