Hydrodesulphurization and hydrodeoxygenation of gasoil-vegetable oil mixtures over a Pt/γ-Al2O3 catalyst

• Desulphurization during co-hydroprocessing of palm oil and gasoil over a Pt/Al2O3 catalyst is investigated.
• Hydrogen consumption kinetics is determined.
• Hydrodeoxygenation selectivity is evaluated by gas analysis.
• H2S plays an important role on HDO selectivity.
• CH4 production from HDO reactions is enhanced in the absence of H2S.

A Pt/γ-Al2O3 catalyst was used for the study of the effect of a refined palm oil on the hydrodesulphurization (HDS) of heavy atmospheric gasoil and vegetable oil mixtures. Catalyst selectivity for the deoxygenation reactions in the presence and absence of H2S and free fatty acids has been investigated. The co-processing of the mixtures was conducted in a bench-scale trickle-bed reactor at total pressure of 33 bar and temperatures from 330 to 370 °C. The palm oil content in the liquid feed mixtures varied from 0 to 20 wt % and its presence adversely affected the HDS reactions in all different experimental conditions. Hydrogen consumption (HCON) was measured and was found to increase with increasing palm oil content in the feed and reaction temperature. Catalytic selectivity of the hydrodeoxygenation reactions was estimated via analysis of the exit gas. The selectivity for decarboxylation and decarbonylation reaction paths increased with increasing palm oil content in the feed and the reaction temperature. The presence of hydrogen sulphide in the reacting mixture results in a strong shift in HDO selectivity towards the deoxygenation pathway. The presence of free fatty acids in the liquid feed has shown similar behavior as the triglycerides. CH4 production is suppressed by the presence of H2S in the gas phase.