Kinetic Investigation in Transalkylation of 1,2,4 Trimethylbenzene with Toluene over Rare Earth Metal-Modified Large Pore Zeolite

Gas-phase transalkylation of 1,2,4 trimethylbenzene (1,2,4-TMB) with toluene was carried out for the production of xylene in a fixed-bed reactor at 1 atm pressure over cerium-modified NaX zeolites. The modified zeolites were characterized by Energy Dispersive Spectra, X-ray Diffraction, and Scanning Electron Microscopy. The acidic properties of metal-modified zeolites were studied using the Temperature Programmed Desorption profile of ammonia. The effects of various parameters like cerium content, catalyst loading, temperature, reactant mole ratio, and space-time were investigated to select the optimum process conditions to maximize the specific product of transalkylation. NaX zeolite modified with cerium exhibited higher activity and stability than the unmodified zeolite in time-on-stream study. Maximum toluene conversion of 44.96% and xylene selectivity of 55.13% were obtained over CeX10 (X zeolite exchanged with 10% ceric ammonium nitrate solution) at 723 K, reactant mole ratio 2.5, and space-time 4.44 kg . h/kmol. Experimental data was fitted in the Langmuir-Hinshelwood-Hougen-Watson (LHHW) model based on dual-site, single-site, and stoichiometric equations. The kinetic and adsorption parameters for toluene conversion were calculated using nonlinear regression. The activation energy for this transalkylation reaction was found to be 60.3 kJ/mol.