| A novel fluidized bed process for the production of xylene from toluene methylation over zeolite based catalysts was investigated. Experimental runs were carried out in a novel bench scale riser simulator at 375,400,425 and 450°C for reaction times of 3,5,7,10,13 and 15 sec. Two different catalysts based on Y and ZSM-5 zeolites were used. Over both catalysts, toluene conversion was found to increase with temperature reaching a value of 12.1%) and 16.81% at 450°C for the Y-and ZSM-5 based catalysts respectively. Further more, the use of short contact times greatly suppressed undesirable secondary para-xylene isomerization leading to para -xytene/ortho-xylene (P/O) ratios much higher than the equilibrium value. Partial deactivation of the external acid sites of the ZSM-5 based catalyst with coke deposit from 1, 3, 5-triisopropyl benzene (TIBP) was found to have a significant positive effect on the P/O ratio in the reaction product. The experimental results were modeled based on the Time-On-Stream model and the activation energies of toluene methylation were found to be 43.18 kJ/mol and 67.79kJ/mol over the Y-and ZSM-5 based catalysts respectively. |
