Enrichment of polymeric WOx species in WOx@SnO2 catalysts for ultra-deep oxidative desulfurization of liquid fuels

Abstract

Designing an efficient and selective catalyst for the ultra-deep sulfur removal from liquid fuels under mild conditions is vibrant in environmental catalysis. This work reports the preparation of catalysts, i.e., WOx-based active sites generated on SnO2, for the sulfur removal from model diesel via biphasic oxidative desulfurization (ODS). The different active species generated on SnO2 such as monomeric and polymeric WOx species, and crystalline WO3 are characterized. Besides being the support, SnO2 adsorbs the sulfur compounds from the oil phase and boosts the ODS performance. No significant change in the ODS activity of WOx@SnO2 is observed in the presence of intrusive nitrogen and aromatic compounds. The order of ODS activity towards different sulfur compounds is dibenzothiophene (DBT) > 4,6-dimethyl DBT > benzothiophene. While using SnO2 with a higher surface area (96.5 m2/g) instead of that with a lower surface area (19.2 m2/g), the formation of highly efficient polymeric WOx species is enhanced. Consequently, the turn over frequency is augmented from 10.99 to 43.23 h−1, which is closely a 4-fold increase. The polymeric WOx species produced on SnO2 having the higher surface area are visualized by HAADF-STEM analysis. Scalable preparation and the higher turnover frequency of the present catalyst can develop a promising catalytic system for the ODS.