Kinetics of the hydrodesulfurization of dibenzothiophene over a commercial NiW/Al2O3 catalyst

The kinetics of the hydrodesulfurization (HDS) reaction of dibenzothiophene (DBT), as the model compound for S-bearing organics in middle distillates, were studied over the commercial NiW/Al2O3 catalyst RN-10 in a high-pressure trickle-bed reactor. The effect of reaction conditions on the catalytic behavior was studied at the hydrogen pressure of 1.5 MPa-4.5 MPa, volume ratio of hydrogen/oil of 150-700, weight hourly space velocity of 15 h-1-60 h-1 and reaction temperature of 280°C to 380°C. The hydrogen pressure and volume ratio of hydrogen/oil exert little influence on the conversion of DBT at the high hydrogen pressures and volume ratios of hydrogen/oil. At low reaction temperatures, the conversion of DBT increases drastically with the increase of reaction temperature up to 3307deg;C, while it increases slowly at high reaction temperatures. A kinetic model of HDS is established according to a second-order kinetics model at various reaction temperatures. The parameters of the model are calculated. The model correlation coefficient is above 0.989. The apparent activated energy at high reaction temperature region ( greater than or equal 330°) is less than that at low temperature region, which are 13.4 kJ/mol and 121.4 kJ/mol respectively. Therefore, the HDS performance of the RN-10 catalyst could not be improved by just increasing the reaction temperature.