An ultrasound enhanced catalytic ozonation process for the ultra-deep desulfurization of diesel oil

Abstract

An ultrasound enhanced catalytic ozonation process was applied for the desulfurization of diesel oil with some metal salts of Keggin-type heteropolyacids, H₃PW₁₂O₄₀–M_x/nH_3−xPW₁₂O₄₀ (abbreviated as M_x/nH_3−xPW₁₂O₄₀), as catalysts. Fe_0.8H_0.6PW₁₂O₄₀ exhibited the best catalytic activity among the prepared catalysts, and catalytic activities of other salts followed the order of Lewis acidity of metal ions, Zn²⁺ < Zr⁴⁺ < Al³⁺ < Ti⁴⁺ < Sn⁴⁺. It was confirmed that the high desulfurization capacity comes from the hydroxyl radicals generated in an ultrasound enhanced catalytic ozonation process by EPR analysis. The difficulty of removing sulfur compounds from diesel depended on the electron density of sulfur atoms. Sulfur compounds with high electron density were more easily removed. Moreover, the Fe_0.8H_0.6PW₁₂O₄₀ catalyst could be recycled successfully 4 times with slightly reduced activity. The Fe_0.8H_0.6PW₁₂O₄₀ catalyst also showed good catalytic activity in the actual diesel oil desulfurization process.