Immobilized VO–Schiff Base Complex on Modified Graphene Oxide Nanosheets as an Efficient and Recyclable Heterogeneous Catalyst in Deep Desulfurization of Model Oil

New heterogeneous catalyst was synthesized via covalent anchoring of oxovanadium(IV) complex of 5,5?-dibromobis(salicyledene)diethylenetriamine (VO[5-Br(Saldien)]) on the surface of chloro-modified graphene oxide (GO@CTS). The structure of the catalyst was investigated using different characterization techniques such as XRD, SEM, EDX, FT-IR, TG, DTA and ICP-AES analyses. The synthesized heterogeneous oxovanadium(IV) was an efficient catalyst for high yield and selective oxidation desulfurization (ODS) of dibenzothiophene (DBT) as a model oil using H2O2 as oxidant and formic acid as a promoter. The effects of the catalyst mass, reaction temperature and time, formic acid/H2O2 ratio and molar ratio of H2O2 to the total amount of sulfur (O/S) on oxidation desulfurization activity were investigated. Moreover, the prepared catalyst can be easily separated from the reaction mixture and reused six times without a significant loss of catalytic activity and selectivity.