EFFECTIVENESS FACTORS FOR SOLID-CATALYZED GAS-SOLID REACTIONS

Effectiveness factors are given for gas-solid reactions catalyzed by a solid catalyst. Since the gasification of the solid reactant takes place at the catalyst-solid reactant interface, the gaseous reactant has to diffuse to the interface. As conversion proceeds, the thickness of the catalyst layer increases causing the effectiveness factor to decrease. Effectiveness factors obtained for the surface reaction show heavier dependence on the order of reaction and the Thiele modulus when compared with the effectiveness factors for the solid-catalyzed gas reactions. For the general case of gaseous reactant consumed by both surface and volume reaction, two Thiele moduli are required and the effectiveness factor decreases exponentially with increasing conversion. The effectiveness factor calculated from literature data on catalytic hydrogasification of coal is given to illustrate this dependence on conversion. © 1979.