Computational fluid dynamics (CFD) is used to study the flow behaviour and conversion in a freely bubbling bed of porous cracking catalyst particles fluidised by a mixture of ethylene and hydrogen on the in-house code FLOTRACS-MP-3D. The solid phase viscosity and pressure are modelled on the basis of kinetic theory of granular flows (KTGF). An effective solid density is calculated to account for the inherent porosity of particles. The cohesive inter-particle forces are incorporated into the CFD model by using an empirical approach proposed in literature. Qualitatively, the CFD model captures the flow behaviour and heat transfer in the bed quite well. On the quantitative front, the variation of conversion with gas velocity is predicted fairly well with the deviation between the predicted and measured conversion remaining within 20%. (C) 2011 Canadian Society for Chemical Engineering