Highly efficient C16-PW9/SiO2 designed based on trivacant tungstophosphate ([A-PW9O34]9−) for rapid oxidative desulfurization under mild conditions

Abstract

In order to achieve ultra-low sulfur fuel production, it is essential to design highly efficient catalysts for deep desulfurization. In this work, trivacant Keggin-type tungstophosphate PW₉ (Na₉[A-PW₉O₃₄]•7H₂O) was innovatively utilized to synthesize polyoxometalate-based supported silica C₁₆-PW₉/SiO₂. The intact presence of polyoxometalates (POMs) was evidenced by several techniques of describing the structure and composition of the obtained hybrid samples. Compared with the saturated tungstophosphate ([PW₁₂O₄₀]³⁻), the [A-PW₉O₃₄]⁹⁻ showed better coordination, which can coordinate with five ILs (C₁₆MIM). More ILs make it easier for the catalyst to attract DBT to the vicinity of PW₉, and the abundance of metal oxide W = O on PW₉ endows the catalyst’s excellent catalytic activity. Specifically, C₁₆-PW₉/SiO₂ exhibited excellent oxidative desulfurization performance, achieving 100 % dibenzothiophene (DBT) conversion efficiency at 50 °C for 10 min, and the turnover frequency (TOF) number reached 723.4 h⁻¹, which is higher than the catalysts of the POMs type that have been published. The strategy of combining lacunary polyoxometalates with ionic liquids offers a fresh viewpoint on the creation of POM-based catalysts.