Kinetics of toluene methylation over USY-zeolite catalyst in a riser simulator

Abstract

The kinetics of toluene alkylation has been studied in a riser simulator over a USY-zeolite-based catalyst. The study was carried out at 375, 400, 425 and 450 °C for reaction times of 3, 5, 7, 10, 13 and 15 s. Toluene conversion was found to increase with both temperature and reaction time with maximum toluene conversion of 12.16% achieved at 450 °C for a reaction time of 15 s. Xylene selectivity, though almost independent of toluene conversion and reaction time was found to be significantly affected by temperature. It was found that xylene selectivity dropped from close to 100% to about 75% as temperature was increased from 375 to 450 °C. A non-equilibrium xylene distribution in the product with P/O and P/M ratios significantly higher than the equilibrium values were obtained. While P/O ratio increased as temperature was increased from 375 to 450 °C, P/M ratio on the other hand was found to decrease. Maximum P/O ratio of 1.63 and P/M ratio of 1.30 were obtained at 450 and 375 °C, respectively. The experimental results were modeled based on the time-on-stream catalyst decay function. The activation energy of toluene methylation was found to be 43.18 kJ/mol.