Production of Middle Distillate Through Hydrocracking of Paraffin Wax Over NiMo/SiO2-Al2O3 Catalysts: Effect of Solvent in the Preparation of SiO2-Al2O3 by a Sol–Gel Method

Abstract

SiO2-Al2O3 supports were prepared by a sol–gel method in the presence of distilled water and ethanol, respectively (SiO2-Al2O3 supports were donated as H-SA and E-SA, respectively). NiMo/SiO2-Al2O3 catalysts (NiMo/H-SA and NiMo/E-SA) were then prepared by an impregnation method for use in the production of middle distillate (C10–C20) through hydrocracking of paraffin wax. The effect of solvent in the preparation of SiO2-Al2O3 support on the catalytic performance of NiMo/SiO2-Al2O3 catalyst was investigated. NiMo/H-SA catalyst showed a higher conversion of wax and a higher selectivity for middle distillate than NiMo/E-SA catalyst. The identity of solvent strongly affected the physical properties of H-SA and E-SA supports. High surface area of H-SA enhanced the dispersion of impregnated metal species, resulting in the increase of active sites of NiMo/H-SA catalyst. Large pore volume and large pore diameter of NiMo/H-SA catalyst played an important role in enhancing internal mass transfer during the reaction. Large acidity of NiMo/H-SA catalyst compared to NiMo/E-SA catalyst was responsible for high conversion of wax over NiMo/H-SA catalyst. The enhanced selectivity for middle distillate over NiMo/H-SA catalyst was attributed to abundant active sites for hydrogenation reaction.