Cluster-like Mo2N anchoring on reduced graphene oxide as the efficient and deep-degree oxidative desulfurization catalyst

Abstract

Oxidative desulfurization (ODS) has been a promising technology for removing sulfur compounds from fuel oil under mild conditions. It is essential to design ODS catalyst exposing plentiful accessible active sites, but it remains a challenge. Here, we have reported the design of cluster-like Mo2N catalyst (1.5 nm) uniformly dispersed on graphene surface by anchoring PMo12 polyoxometalate clusters on polyethyleneimine (PEI)-modified graphite oxide (GO). The obtained Mo2N/rGO-A catalyst has highly exposed active sites and plentiful accessible surface. Importantly, Mo2N catalyst can readily activate oxidant to generate active Mo2N-peroxo intermediates. In the ODS reaction of dibenzothiophene (DBT) with H2O2 as the oxidant, the catalyst can achieve the 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, being superior to the corresponding Mo-O-based catalysts, large-sized Mo2N/rGO-D catalyst and the most of the reported transition metal-based catalysts. Furthermore, the catalyst shows good cycling stability with no obvious deactivation after eight cycles. The ODS reaction of DBT over Mo2N/rGO-A catalyst mainly follows a non-radical oxidation mechanism with DBTO2 (dibenzothiophene sulfone) being the only oxidation product based on the free radical scavenger experiment and GC-MS analysis. This work has important implications for the design of efficient and stable small-sized Mo-based catalyst for ODS of fuel oil.