Cluster-like Mo2N anchored on reduced graphene oxide as an efficient and high-performance catalyst for deep-degree oxidative desulfurization

Abstract

Oxidative desulfurization (ODS) is a promising technology for removing sulfur compounds from fuel oil under mild conditions. Designing an ODS catalyst with plentiful accessible active sites is essential, yet it remains a challenge. Here, we have reported the design of a cluster-like Mo₂N catalyst (1.5 nm) uniformly dispersed on a graphene surface by anchoring PMo₁₂ polyoxometalate clusters on polyethyleneimine (PEI)-modified graphite oxide (GO). The obtained Mo₂N/rGO-A catalyst demonstrated highly exposed active sites and a highly accessible surface. Importantly, the Mo₂N catalyst readily activated the oxidant to generate active Mo₂N-peroxo intermediates. In the ODS reaction of dibenzothiophene (DBT) with H₂O₂ as the oxidant, the catalyst achieved complete removal of sulfur compounds (1000 ppm) within 15 min, with a reaction rate constant k of 1.94 × 10⁻¹ min⁻¹ at 60 °C. This performance surpassed that of Mo–O-based catalysts, large-sized Mo₂N/rGO-D catalyst and most of the reported transition metal-based catalysts. Furthermore, the catalyst showed good cycling stability with no obvious deactivation after eight cycles. The ODS reaction of DBT over the Mo₂N/rGO-A catalyst primarily followed a non-radical oxidation mechanism, with DBTO₂ (dibenzothiophene sulfone) being the only oxidation product, as confirmed by the free radical scavenger experiments and GC-MS analysis. This work has important implications for the design of efficient and stable small-sized Mo-based catalysts for the ODS of fuel oil.