Effect of the Co/Mo Ratio on the Morphology and Activity of the CoMo Catalyst Supported on MgO Nanosheets in Dibenzothiophene Hydrodesulfurization

MgO nanosheets were employed to prepare CoMo catalysts with different Co/Mo ratios (CoMo/NA-MgO) by an aqueous co-impregnation method. CoMo/NA-MgO displayed an increase in the catalytic activity for hydrodesulfurization of dibenzothiophene as the Co/Mo ratio increased in the CoMo catalysts, and it reached maximal activity at the Co/Mo ratio of 0.5. The reaction rate constant (k) and turnover frequency of CoMo/NA-MgO-0.5 (2.7 × 10–7 mol g–1 s–1 and 7.9 × 10–4 s–1, respectively) were higher than those of conventional CoMo/γ-Al2O3 (2.1 × 10–7 mol g–1 s–1 and 4.1 × 10–5 s–1). Characterization results revealed that more basic sites on NA-MgO strengthen the interaction between MoO x and NA-MgO, leading to CoMo/NA-MgO with better MoO x dispersion than that of CoMo/γ-Al2O3. In addition, an increase in Co/Mo for CoMo/NA-MgO weakened the interaction of MoO x with NA-MgO, leading to more MoO x species transformed into a less stacked type II CoMoS phase after sulfidation, improving direct desulfurization activity.