Analysis of gas pressure buildup within a porous catalyst particle which is wet by a liquid reactant

Abstract

During the startup of a liquid-feed catalytic reactor, liquid reactant can wet the outside surfaces of porous catalyst particles and wick into the pores by capillary flow. Under these conditions, the liquid in the pores of the catalyst particles will prevent the escape of gaseous reaction products until sufficient gas pressure is generated to expel the liquid from the pores. A mathematical analysis of the gas pressure buildup within a porous catalyst particle which is wet by liquid reactant was developed which considers the simultaneous processes of mass transfer, heat, transfer and chemical reaction within the porous particle. Capillary and viscous forces were considered in developing methods to predict the residence time of liquid reactant in the catalyst particle. This liquid penetration model is used to explain the unusually long ignition delays and sudsequent reactor pressure excursions observed during the startup of certain liquid-feed catalytic reactors. In particular, startup characteristics observed with hydrazine catalytic reactors are noted and discussed relative to the computed liquid pore residence times.