m-Xylene isomerization and disproportionation kinetics have been studied over four zeolite catalysts (ZSM-5, mordenite, SSZ-33 and TNU-9) in a riser simulator reactor over the temperature range of 300-400 degrees C. The effect of reaction conditions on m-xylene conversion, p-xylene/o-xylene (P/O) ratios, ratio of isomerization to disproportionation (VD) products were investigated with the view of comparing the respective performances of the catalysts. Kinetic parameters for the disappearance of m-xylene were determined using catalyst activity decay function based on time-on-stream (TOS). The experimental results show that SSZ-33, TNU-9 and mordenite gave higher m-xylene conversion compared to ZSM-5. Both m-xylene P/O and I/D ratios over the catalysts were found to be in the order: ZSM-5 > TNU-9 > SSZ-33 > mordenite. Apparent activation energy for m-xylene disproportionation reaction was found to decrease in the order: EZSM-5 > ETNU-9 > E-mordenite > ESSZ-33. The riser simulator and the modeling procedures employed have proved to be very effective as tools in investigating fluidized bed reaction kinetics. (C) 2010 Elsevier B.V. All rights reserved.