Effective Zinc-Substituted Keggin Composite to Catalyze the Removal of Sulfur from Real Diesels under a Solvent-Free System

The Keggin phosphotungstate (PW₁₂) and its zinc derivative (PW₁₁Zn) were tested as oxidative catalysts for desulfurization processes using simulated and real diesels. These compounds were used as homogeneous catalysts, while the corresponding SBA-15 composites were used as heterogeneous catalysts. The comparison of their catalytic performance demonstrated that the zinc-substituted polyoxometalate is more efficient than the plenary PW₁₂ structure. Additionally, using the heterogeneous PW₁₁Zn@aptesSBA-15, the sustainability and catalytic efficiency was largely improved, allowing the total sulfur removal from model diesel after 1 h using a small amount of oxidant (H₂O₂/S = 4) under an oxidative solvent-free system. The desulfurization of real diesels was performed under similar conditions, achieving 87.8% of efficiency using the PW₁₁Zn@aptesSBA-15 catalyst. Furthermore, the catalyst maintained its activity over consecutive desulfurization cycles. The cost-effective operational conditions achieved with PW₁₁Zn@aptesSBA-15 turn this into a promising material to be used in an industrial scale to treat diesel.