Preparation of highly active g-C3N4 supported amphiphilic quaternary ammonium phosphotungstate catalyst for solvent-free oxidative desulfurization of benzothiophene

The high efficiency amphiphilic CTAB-PW( x )/g-C 3 N 4 catalysts with different quaternary ammonium phosphotungstate (CTAB-PW) loadings ( x , wt%) were designed and successfully synthesized. The catalysts were characterized by XRD, SEM, FTIR, XPS and BET. The effects of CTAB-PW loading, oxidative desulfurization (ODS) conditions and different sulfides on the performance of ODS were investigated using green oxidant H 2 O 2 as oxidant in solvent-free reaction system. The results show the crystalline structure of CTAB-PW and g-C 3 N 4 were retained in CTAB-PW( x )/g-C 3 N 4 hybrid materials. And the use of cetyltrimethylammonium bromide (CTAB) can save cost and prevent the application of harmful solvents. The CTAB-PW( x )/g-C 3 N 4 with CTAB-PW loading of 50% exhibited the best ODS performance. The benzothiophene, dibenzothiophene removal rate of 99.9% and 4,6-dimethyl-dibenzothiophene removal rate of 98.9% were achieved under the conditions of catalyst dosage of 0.04 g, O/S molar ratio of 8, reaction temperature of 60 °C for 2 h. Moreover, the removal rate of benzothiophene still maintained at 94.3% after the catalyst was recovered for 5 times, which was mainly due to the presence of amino group in g-C 3 N 4 , which can inhibit the leaching of active phosphotungstate (HPW). Graphical abstract