Heteropolyoxometalates which are included in microporous silica, CsxH3−xPMo12O40/SiO2 and CsyH5−yPMo10V2O40/SiO2, as insoluble solid bifunctional catalysts: synthesis and selective oxidation of benzyl alcohol in liquid–solid systems Original Research Arti

Heteropolyoxometalates (HPOMs) which are included in microporous silica, CsxH3−xPMo12O40/SiO2 and CsyH5−yPMo10V2O40/SiO2, have been synthesized by a sol–gel technique and characterized by IR, UV–VIS, X-ray and N2 adsorption isotherms. IR and UV–VIS data indicate that the identities of CsxH3−xPMo12O40 and CsyH5−yPMo10V2O40 are preserved within these synthesized compounds. TEM image and BET adsorption isotherms confirm the presence of nanometer particles and microporous structures. X-ray powder patterns prove that the cesium salts of the HPOMs are uniformly dispersed in the silica network. As insoluble solid bifunctional catalysts, they show high catalytic activity and selectivity for selective oxidation of benzyl alcohol into benzyl aldehyde by H2O2 in liquid–solid systems. The highest activity is observed at x=1.5 or y=2.5 in CsxH3−xPMo12O40/SiO2 or CsyH5−yPMo10V2O40/SiO2, respectively.