Discrete lumping kinetic models for hydrodesulfuration and hydrocracking of a mixture of FCC feedstock and light gasoil

The hydrotreating of a mixture of Fluid Catalytic Cracking feedstock (70 wt.%) and light gas oil (30 wt.%) was carried out at 340–380° C, initial pressure of 70 bar, at reaction times of 1 to 4 h in a batch reactor system. Commercial alumina NiMo supported catalyst was used, at 5 g of powder for each 100 g oil. The catalyst particle was 60–70 mesh; and the stirring speed was kept at 750 rpm. The feedstock and products were characterized by Energy-Dispersive X-ray Fluorescence Spectroscopy and simulated distillation to determine the hydrodesulfuration and hydrocracking conversion, respectively. Experimental data were used to estimate the kinetic model parameters for hydrodesulfuration (single lump) and hydrocracking (five lumps), by using power law kinetic models. From the inverse modeling problem solution, the global error was of 0.0054 for hydrodesulfuration, and the reaction order and activation energy were 2.75 and 129.8 kJ/mol, respectively. For hydrocracking, a first order reaction kinetics was employed; the errors were 0.0042, 0.0021 and 0.0030 for reaction temperatures of 340, 360 and 380° C, respectively, while the activation energies ranged between 15.2 and 208.5 kJ/mol, being the largest for the conversion from heavy gasoil to light gas oil.