Thermal Cracking and Catalytic Hydrocracking of a Colombian Vacuum Residue and Its Maltenes and Asphaltenes Fractions in Toluene

Thermal cracking and catalytic (molybdenum naphthenate) hydrocracking processes in toluene solvent were carried out in a batch reactor for a typical Colombian heavy vacuum residue and its corresponding separated maltenes and asphaltenes fractions. The thermal cracking and catalytic hydrocracking tests were performed at 430 °C and 13.5 MPa for 25 min in the presence of nitrogen and hydrogen, respectively. Additionally, catalytic hydrocracking was also conducted after conditioning the vacuum residue at 380 °C, and 12.2 MPa of H₂ for 60 min with activated carbon. The cracking and catalytic hydrocracking performances of the vacuum residue and its components (maltenes and asphaltenes) were assessed by evaluating the effects on the yield and quality of the products (gas, toluene-insoluble solid, and liquid) utilizing SARA (saturates, aromatics, resins, and asphaltenes) composition and removal of sulfur and heavy (Ni, V) metals analyses. The vacuum residue showed asphaltene conversions of 53.1 and 43.1 wt % (excluding the yield of toluene-insoluble solids) under conditions of thermal cracking and catalytic hydrocracking, respectively. When the vacuum residue was pretreated with activated carbon and then catalytically hydrocracked, the asphaltenes conversion was higher (68.7 wt %, excluding the yield of toluene-insoluble solids) when compared to that during thermal cracking and catalytic hydrocracking in the absence of such pretreatment. Overall, the results showed that the hydrocracking of a vacuum residue in toluene with a molybdenum naphthenate catalyst is effective in forming liquid products that are lighter and with a lower concentration of sulfur and Ni and V heavy metals. These heteroatoms are removed in the toluene-insoluble solid products that concentrate recalcitrant sulfur and nickel complex (i.e., porphyrinic) aromatic compounds to a greater extent. The primary function of the thermally activated carbon pretreatment was to increase the yield of lighter liquid products as a likely result of the conversion of more reactive vanadium-containing complex structures into simpler components that remain in the liquid product and which otherwise would have been rejected in the toluene-insoluble solid fractions.