Efficient synthesis of 3-methylindole using biomass-derived glycerol and aniline over ZnO and CeO2 modified Ag/SBA-15 catalysts

Abstract

An efficient mesoporous catalyst of Ag/SBA-15 modified with ZnO and CeO2 was successfully constructed with the purpose of efficiently synthesizing 3-methylindole by biomass-derived glycerol and aniline, which up to 62% yield and 75% selectivity for 3-methylindole were achieved when Ag loading was 1.00 mmol/g−1, ZnO or CeO2 content was 1.00 or 0.05 mmol/g−1, respectively. And only 3% yield decreased when the catalyst was circulated five times. The characterizations researches on N2 physical adsorption, Fourier transform infrared (FT-IR), scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM-EDX), temperature programmed reduction of hydrogen (H2-TPR), X-ray diffraction (XRD), transmission electron microscopy (TEM), temperature programmed desorption (TPD) of NH3 and CO2, thermogravimetric and differential thermal analysis (TG-DTA) indicated that adding the promoter of ZnO to Ag/SBA-15 increased the dispersion of the silver particles significantly and controlled the aggregation of Ag nanoparticles during the reaction remarkably because doping ZnO greatly increased the polarity of the composite carrier SBA–15–ZnO and brought about the interaction between Ag and carrier enhanced. CeO2 could promote the reduction of Ag2O and suppress the formation of carbon deposition effectively. In addition, doping ZnO and CeO2 increased the number of the weak-acid centers of the SBA-15 supported Ag-based catalyst observably, thereby the catalyst of Ag/SBA-15-ZnO-–ZnO–CeO2 acquired a good selectivity. Moreover, the reaction pathway for 3-methylindole synthesis by biomass-derived glycerol and aniline was probed in depth and a reasonable route was proposed.