Dibenzothiophene hydrodesulfurization using in situ generated hydrogen over Pd promoted alumina-based catalysts

Catalytic hydrodesulfurization (HDS) of dibenzothiophene (DBT) was carried out in a temperature range of 320-400 °C using in situ generated hydrogen via steam reforming of ethanol and the effect of some organic additives was studied for the first time. Four kinds of alumina-based catalysts, i.e. Co-Mo/Al2O3, Ni-Mo/Al2O3 and their corresponding Pd promoted catalysts Pd-Co-Mo/Al2O3 and Pd-Ni-Mo/Al2O3, prepared through incipient impregnation method, were used for the desulfurization process. Catalytic activity was investigated in a batch autoclave reactor in the complete absence of external hydrogen gas. Experiments showed that organic additives like diethylene glycol (DEG), phenol, naphthalene, anthracene, o-xylene, tetralin, decalin and pyridine can affect the HDS activity of the catalysts in different ways, and only naphthalene is inhibitive for the catalytic activity towards HDS. The results showed that Ni-based catalysts are more active than Co-based ones while Pd shows a high promotion effect. DBT conversion of up to 97% was achieved with Pd-Ni-Mo/Al2O3 catalyst at 380 °C temperature and 13 h reaction time. Catalyst systems followed the HDS activity order of: Pd-Ni-Mo/Al2O3 > Ni-Mo/Al2O3 > Pd-Co-Mo/Al2O3 > Co-Mo/Al2O3 at all conditions. Qualitative analysis of the products stream was carried out using GC-MS technique. The present HDS process using in situ generated hydrogen might be applied as an alternative approach for the catalytic HDS of DBT on industrial level due to its cost effectiveness, mild operating conditions and high activity of the catalysts.