Commercial HZSM-5 was modified by treating with phosphoric acid and boric acid for the selective methylation of benzene. The study of the performance with respect to the selectivity of the major products, toluene and xylene is the interest of the work. Catalysts were characterized based on BET surface area and XRD, SEM and NH3-TPD analysis to observe the change in properties due to their modification. Although benzene conversion is the highest with HZSM-5 catalyst, but in terms of selectivity, BZSM-5 and PZSM-5 are found to be the suitable catalyst for toluene and xylenes respectively. Xylene selectivity declines for HZSM-5 with the increase in temperature where as the PZSM-5 and BZSM-5 show slightly increasing tendency.

The performance of toluene methylation reaction was studied by H-ZSM-5 modified with La, Ce and Nb at different percentage loading and found that 10% metal loading is producing the best performance in the reaction in terms of toluene conversion. The catalyst was coated on silicon carbide foam support which showed better conversion than the pelleted catalyst. Again, among the treated and untreated H-ZSM-5, the La-ZSM-5 catalyst is chosen for the reaction for its highest selectivity towards xylene, the main product. All catalysts were characterized in terms of surface properties, SEM, XRD and NH3-TPD. Kinetic study was done by La-ZSM-5 with 10% loading. Langmuir Hinshelwood kinetic model with surface reaction as rate controlling step was selected as the rate equation. The activation energy was found to be 47 kJ/mol.

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