Amorphous Cr2WO6-Modified WO3 Nanowires with a Large Specific Surface Area and Rich Lewis Acid Sites: A Highly Efficient Catalyst for Oxidative Desulfurization.

Abstract

The oxidative desulfurization (ODS) of fuel oils is of great significance for environmental protection, and the development of efficient ODS heterogeneous catalysts is highly desired. Herein, we have designed and synthesized a novel material of amorphous Cr2WO6-modified WO3 (a-Cr2WO6/WO3) nanowires (3-6 nm) with a large specific surface area of 289.5 m2·g-1 and rich Lewis acid sites. The formation of such a unique nanowire is attributed to the adsorption of Cr3+ cations on non-(001) planes of WO3. In the ODS process, the a-Cr2WO6/WO3 nanowires can efficiently oxidize benzothiophene (BT), dibenzothiophene (DBT), and 4,6-dimethyldibenzothiophene (4,6-DMDBT) to their corresponding sulfones in a quasi-microemulsion reaction system and possess the highest activity (Ea = 55.4 kJ/mol) for DBT: 99.0% of 15,000 ppm DBT with 2600 ppm S can be removed (70 °C, H2O2 as the oxidant). The improvement in ODS activity from most of WO3 catalysts is owing to the sufficient active sites and enhanced adsorption of DBT on the basis of structural features of a-Cr2WO6/WO3 nanowires. Combined with free radical capture experiments, a possible ODS mechanism of W(O2) peroxotungstate route based on surface -OH groups is reasonably proposed. Moreover, the a-Cr2WO6/WO3 nanowires have good stability and can be synthesized on a large scale, suggesting its potential applications as an efficient heterogeneous catalyst.