LAUSR

Abstract Keggin-type polyoxometalates (POM) immobilized on alkylaminophosphazene (RPN)-functionalized silica (POM/RPN-SiO2) are new effective single-site solid catalysts for oxidative desulfurization (ODS) of diesel fuel under mild conditions in a biphasic system composed of a benzothiophene-containing model diesel fuel (heptane) and aqueous 30% H2O2. The catalytic activity of POM/RPN-SiO2 was found to be influenced by the choice of POM and the amine R group in RPN, decreasing in the order PMo > PW > SiW and Bz > iBu > iPr, respectively. The most effective catalyst, PMo/BzPN-SiO2 (PMo = PMo12O403−), exhibited 100% removal of dibenzothiophene from model diesel fuel at 60 °C and ambient pressure and could be reused without loss of activity. This catalyst outperforms other recently reported heterogeneous catalysts for ODS in similar systems. 13C, 29Si and 31P MAS NMR, FTIR, SEM, BET and elemental analysis were used to characterize the structure of surface phosphazene and POM species in the new catalysts.