Fabrication of various morphological forms of a g-C3N4-supported MoO3 catalyst for the oxidative desulfurization of dibenzothiophene

Abstract

A series of catalysts consisting of nanosized MoO₃ particles supported on carbon nitride with different morphologies of bulk g-C₃N₄ (BCN), tubulous g-C₃N₄ (TCN), and rod g-C₃N₄ (RCN) were synthesized, and the mass content of MoO₃ was systematically screened. The catalysts were characterized by XRD, FT-IR, TG, SEM and TEM to understand the structure–property relationships. It proved that TCN possesses the highest pore volume compared to BCN and RCN owing to the unique morphology. MoO₃ particles were highly dispersed on the surface of TCN. When the catalysts were investigated in oxidative desulfurization, MoO₃/TCN gave a relatively higher desulfurization rate of 84.04%. The effects of reaction parameters on oxidative desulfurization were studied in detail, and reaction temperature, reaction time, catalyst loading, the ratio of O/S, and catalyst dosage were regarded for the optimal conditions. Under the optimal reaction conditions, of m(catalyst) = 0.013 g mL⁻¹, T = 60 °C, O/S = 4, V(model oil) = 15 mL, and V(CH₃OH) = 15 mL, the conversion of DBT could almost achieve 100%. Moreover, after six cycles of reuse, the activity of MoO₃/TCN did not decrease significantly, indicating good stability. Different typical sulfur-containing substrates were selected, including BT, DBT, and 4,6-DBT. A possible mechanism for oxidative desulfurization over MoO₃/TCN was proposed; hydroxyl radicals are suggested to be the main reactive species during the reaction according to the scavenger test.