A Comparative study on hydrocracking and hydrovisbreaking combination for heavy vacuum residue conversion

Upgrading of heavy vacuum residue (302.3 ppm Ni + V, 4.36 wt% S, and 13 wt% asphaltenes) into valuable lighter fuels has been studied in a batch autoclave reactor by hydroconversions over bifunctional sulfided catalyst W–Ni–P/SiO2–Al2O3, at different reaction temperatures, 350–425 °C and 12 MPa hydrogen pressure. The activity of the sulfided catalyst towards hydrocracking reactions scheme alone has been compared with a combination scheme (hydrovisbreaking followed by hydrocracking) in order to produce light fractions suitable for automotive fuels. The catalyst gave, at higher temperature 425 °C, about 80% feedstock conversion, 5% coke make, 98% hydrodesulfurization (HDS) and 73% asphaltenes reduction, when applying the combination scheme, compared with hydrocracking alone. The presence of hydrogen in the hydrovisbreaking reaction medium was necessary to limit coke production. These results indicated that hydrovisbreaking was a suitable alternate treatment option for heavy vacuum residue before hydrocracking process.