Activity and sulfidation behavior of the CoMo/Al2O3 hydrotreating catalyst: The effect of drying conditions

The influence of drying condition of the CoMo/Al2O3 catalyst prepared using citric acid as a chelating agent on the sulfidation behavior and on the catalytic activity to hydrodesulfurization of straight-run gas oil (SRGO) was investigated. The catalysts dried at 110, 220, 300 and 400 °C were studied using Raman, IRS and DTG techniques. The sulfidation behavior with straight-run gas oil spiked with dimethyldisulfide (DMDS) was investigated using gas chromatography (GC) with a thermal conductivity detector and GC with an atomic-emission detector for analysis of gas and the liquid phases, respectively. It was shown that the sulfidation behavior of the catalysts prepared using the chelating agents depends on the drying condition: the lower drying temperature, the later DMDS conversion and oxide precursor sulfidation starts. A higher activity in SRGO desulfurization was obtained with catalysts dried at 110 and 220 °C. This phenomenon was accounted for by the stabilization effect of chelating agent that retards precursor sulfiding but provides favorably the formation of active CoMoS phase and achieving the highest activity.