synergistic interactions between ti–ooh and (po 4 [wo 2 (o 2 )] 4 ) 3- of hpw/zn-ti hydrotalcites: efficient heterogeneous catalysts for the epoxidation of fatty acid methyl ester

A series of hpw/zn-ti layered double hydroxides (ldhs) were prepared by immobilizing phosphotungstic acid (hpw) on the zn-ti ldhs. systematically characterizations were performed to elucidate their structure. these hpw/zn-ti ldhs hybrids were used as heterogeneous catalysts in the epoxidation of fatty acid methyl ester (fames) with h 2 o 2 . the hpw/zn-ti ldhs showed higher activity than bulk hpw and zn-ti ldhs. the conversion of fames and the selectivity to epoxy fatty acid methyl ester (efame) were up to 90.6 and 86.0%, respectively. (po 4 [wo 2 (o 2 )] 4 ) 3- was presumed to be the active site for the epoxidation in this work. the formed oxygen-donating intermediate ti−ooh transferred oxygen free radicals to (po 4 [wo 2 (o 2 )] 4 ) 3- in the catalytic process, accelerating the transfer of oxygen free radicals. therefore, high catalytic activity of hpw/zn-ti ldhs is related to the potential synergistic interactions of ti−ooh and pw anions.