Heteropoly ionic liquids functionalized ?-Fe2O3 NPs: synthesis, characterization, and catalytic application in selective oxidation of benzyl alcohol to benzaldehyde using H2O2 as a green oxidant

摘要

A novel series of heteropoly ionic liquids [HMIm](3)[PW12O40], [HMIm](3)[PMo12O40], and [HMIm](4)[SiW12O40] were synthesized and supported on magnetic gamma-Fe2O3 NPs to get magnetic heterogeneous catalysts, Fe2O3-[HMIm](3)[PW12O40], Fe2O3-[HMIm](3)[PMo12O40], and Fe2O3-[HMIm](4)[SiW12O40]. The materials were characterized using various techniques such as FTIR, EDX, XRD, TEM, SEM, elemental mapping, EPR, TGA, and VSM analyses. Among the three heteropoly ionic liquids, [HMIm](3)[PW12O40] had very strong acidic sites, as confirmed by potentiometric titration. Fe2O3-[HMIm](3)[PW12O40] had also very strong acidic property as analyzed by potentiometric titration. Further, thermal stability of Fe2O3-[HMIm](3)[PW12O40] was assessed using TGA analysis, and the catalyst was found stable up to 500 ?. The catalytic prospect of the materials was examined through selective oxidation of benzyl alcohol to benzaldehyde using H2O2 as a green oxidant. The reaction was monitored using GC-MS analysis. Among the three magnetic materials, Fe2O3-[HMIm](3)[PW12O40] had the highest catalytic activity in terms of conversion of benzyl alcohol (98%) and benzaldehyde selectivity (100%). A recyclability study of Fe2O3-[HMIm](3)[PW12O40] was done and found that the material was recyclable up to 7 cycles without any significant loss in its catalytic performance.