Upgrading of thiophenic compounds from fuels over a silver-modified MoO3 catalyst under ambient conditions

The demand for heterocyclic sulfur compounds is increasingly in fine chemical industry, where the thiophenic sulfur impurities in fuels can be a potential recyclable feedstock. In this work, the catalytic upgrading of thiophenic sulfur compounds over a silver-modified MoO 3 catalyst under ambient conditions was reported. Br 2 and H 2 O 2 /HBr were used to convert thiophenic compounds in alkane and alcohol solutions. The conversion of various thiophenic compounds (thiophene, benzothiophene and dibenzothiophene) to the corresponding bromides reached up to 81.6 ~ 99.8%. The bromination path undergoes electrophilic substitution mechanism, and the transformation of mono- to dibromides is identified as the rate-determining step. The introduction of MoAg 2 O 4 phase on MoO 3 is rationalized to boost the conversion of mono-bromothiophene, which results in the selectivity of 2,5-dibromothiophene increased from 10% to over 50%. The optimized silver loading was 10% due to its high thiophene conversion and selectivity of dibromides. Silver modification of MoO 3 rods not only stabilized the textural property of catalysts but also improved its bromination activity compared to the bulk MoO 3 indicated by SEM and FTIR characterization. Density functional theory (DFT) calculation suggested that the formation of 2-bromothiphene and 2,5-dibromothiophene were preferred on the MoO 3 (111) and MoAg 2 O 4 (111) sites, respectively. The catalytic upgrading approach paves the way for the efficient utilization of thiophenic sulfur impurities in fuels to their value-added under mild conditions.