Kinetics of thermal hydrocracking of heavy oils under moderate hydroprocessing reaction conditions

Thermal hydrocracking (non-catalytic) of a heavy oil residue was studied in a bench-scale fixed-bed reactor unit. The reaction temperature and the ratio of total mass flow to inert material volume were varied from 380 to 420 °C and from 0.23 to 0.65 g T cm SiC - 3 h - 1 respectively, at constant hydrogen-to-oil ratio (890 m3/m3) and pressure (100 kg/cm2). The reactor was loaded with silicon carbide as inert material. The results from the simulated distillation of the feed and of the products were used to calculate conversion of vacuum residue and the yield of each specific fraction (vacuum gasoil, middle distillates, naphtha and gases). The lumping approach was used to study the kinetics of the hydrocracking reaction. The results confirm that hydrocracking reactions proceed by cascade mechanism from the heavier fractions to the lighter fractions. Naphtha does not hydrocrack to form gases at the operating conditions studied. The reaction order that better fits the experimental data of vacuum residue conversion is two with activation energy of 42 kcal/mol.