Synthesis, Characterization and Catalytic Fuel Ultra-Deep Desulfurization of Keggin-Type Polyoxometalates

Keggin-type polyoxometalate catalysts M-x/n,H0.6PW (Zr0.6H0.6PW, Al0.8H0.6PW, Zn1.2H0.6PW, Fe0.8H0.6PW, Ti0.6H0.6PW and Sn0.6H0.6PW) and Alx/3H3-xPW (AlPW, Al0.8H0.6PW, Al0.5H1.5PW, Al0.3H2.1PW and Al0.1H2.7PW) were prepared using 6 metal salts and phosphotungstate. The prepared catalysts were characterized by FTIR, XRD, DSC/ TGA and ICP. Al0.5H1.5PW is the best catalyst based on the catalytic activity screening results. The catalytic oxidation extraction for fuel ultra-deep desulfurization was studied using hydrogen peroxide as the oxidant and MeCN as the extractant. The effect of catalyst dosage, O/S molar ratio, pre-immersion time of the catalyst in H2O2 solution, reaction temperature and initial sulfur content on the desulfurization efficiency was studied. The results show that the sulfur content of simulated diesel is reduced from 350 mg.L-1 to 2.45 mg.L-1 with a desulfurization efficiency of 99.3% at 60 min under the following operating conditions: Al0.5H1.5PW catalyst/simulated diesel, 0.25%(m/m); molar ratio of 0/S, 10; pre-immersion time of the catalyst in H2O2 solution, 8 min; reaction temperature, 60 degrees C; initial sulfur content, 350 mg.L-1. The efficiency of the oxidation extraction desulfurization is much higher than that of extraction only (45.3% higher). Moreover, very good desulfurization efficiency is obtained for real gasoline and diesel catalytic oxidative desulfurization over Al0.5H1.5PW catalyst, and the desulfurization efficiency is not reduced obviously after 5 cycles.