Comparison of citric acid and glycol effects on the state of active phase species and catalytic properties of CoPMo/Al2O3 hydrotreating catalysts

CoPMo/Al2O3 catalysts were prepared using H3PMo12O40 and Co complexes with citric acid (CA) or non-complexing organic additives such as ethylene glycol (EG), diethylene glycol, triethylene glycol (TEG), glycerol, and a mixture of EG and CA. The catalysts were characterized by low-temperature N-2 adsorption, Raman spectroscopy, thermogravimetric analysis, temperature-programmed reduction, Xray photoelectron spectroscopy, and high-resolution transmission electron microscopy. The prepared samples were tested in hydrodesulfurization (HDS) of dibenzothiophene (DBT). The addition of either CA or glycols led to several beneficial effects such as weakening of the slab-support interaction at enhancing the promotion degree, dispersion and stacking number of the CoMoS species. It has been shown that the promotion degree of CoMoS edges increased with a pore volume gain by the additive-impregnated catalysts after their sulfidation. Catalysts with CA, TEG or the EG-CA mixture demonstrated higher activity in DBT HDS. Probable reasons for the found relationships are discussed. (C) 2016 Elsevier B.V. All rights reserved.