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An excellent catalyst with a large number of weak acid centers and highly dispersed copper nanoparticles embedded in mesoporous SBA-15 carrier was successfully constructed for the purpose of efficient conversion of aniline with biomass-derived glycerin to the high value-added 3-methylindole, in which the catalyst of Cu/SBA-15 was modified with Al2O3, La2O3 and CoO in sequence. The modified carrier and the copper-based catalysts were studied by scanning electron microscopy and energy-dispersive X-ray (SEM–EDX) spectroscopy, nitrogen physical adsorption, ammonia temperature programmed desorption (NH3-TPD), hydrogen temperature programmed reduction (H2-TPR), powder X-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric and differential thermal analysis (TG–DTA) and inductively coupled plasma (ICP) emission spectroscopy. The research found that the Cu/CoO/La2O3/Al2O3/SBA-15 catalyst exhibited a very good catalytic performance with 3-methylindole yield up to 73.3% and selectivity reaching 86.4%. Besides, only a 3.9% yield decreased after the catalyst was circulated seven times. The characterizations revealed that Al2O3 could enhance the polarity of the carrier, thereby the interaction between the active component and the composite carrier was strengthened and the dispersion of copper was increased significantly. Adding La2O3 to Cu/SBA-15-Al2O3 could weaken the acidity and inhibit the formation of carbon deposits. CoO promoter could increase the number of weak acid centers, which was conducive to a good dispersion of active component and the high selectivity of 3-methylindole. Furthermore, the reaction pathway of gas-phase synthesis of 3-methylindole from glycerin and aniline on Cu/CoO/La2O3/Al2O3/SBA-15 was explored. [ABSTRACT FROM AUTHOR]

Highlights: [•] Zeolites-supported Cu-based catalysts were used in the synthesis of 3-methylindole. [•] Cu/NaY exhibited higher activity and selectivity than Cu/5A, Cu/HZSM-5 or Cu/MCM-41. [•] The addition of Na2O to Cu/NaY improved the selectivity of the catalyst remarkably. [•] Over Cu/NaY–Na2O, the selectivity and yield of 3-methylindole reached 72.3 and 50.4%, respectively. [•] The catalytic mechanism for the synthesis of 3-methylindole was proposed. [ABSTRACT FROM AUTHOR]

An AlO-modified Cu/SiO catalyst was used in the vapor-phase synthesis of 3-methylindole from glycerol and aniline. The effect of AlO and the preparation method of the Cu-AlO/SiO catalyst on the activity and selectivity of the catalyst were investigated. The catalysts were characterized by XRD, TEM, H-TPR, NH-TPD and TG techniques. The results indicated that the addition of AlO to Cu/SiO increased the activity and selectivity remarkably. Cu-AlO/SiO prepared by co-precipitation (COP) exhibited better catalytic performance compared with the catalyst prepared by incipient wetness impregnation (IWI) or ultrasonic impregnation (UI), because the catalyst possessed a good dispersion of Cu particles, a better resistance to the sintering of Cu particles as well as a larger amount of weak acid sites. Over Cu-AlO/SiO (COP) with the AlO content of 1.1 mmol/g, the yield of 3-methylindole reached 44 % at the third hour of reaction, and the yield could be kept to 41 % even after the reaction time of 51 h. [ABSTRACT FROM AUTHOR]

Abstract: A novel efficient method for vapor-phase synthesis of 3-methylindole from aniline and glycerol has been developed over Cu-based catalysts. The catalysts were characterized by BET, XRD, H2-TPR and NH3-TPD techniques. The results indicated that Cu/SiO2-Al2O3 catalyst exhibited high activity. The yield of 3-methylindole could be up to 40% when the Cu loading was 5.41wt% and the reaction temperature was 240°C. Moreover, the catalyst could be reused without obvious loss of the yield even after reaction time of 46h. Copper-based catalyst with good dispersion and large amount of weak acid sites was favorable for producing 3-methylindole. A possible reaction pathway for the catalytic synthesis of 3-methylindole was proposed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ag/SBA-15 modified with ZnO and CeO 2 exhibited a good activity with the 3-methylindole yield of 62%. • ZnO could increase the dispersion of silver and inhibit the sintering of Ag particles effectively. • CeO 2 could promote the reduction of Ag 2 O and suppress the formation of carbon deposition. • The yield of 3-methylindole sill reached 59% when Ag/SBA-15–ZnO–CeO 2 was circulated five times. • The reaction pathway was investigated in deeply and a probable route was proposed. An efficient mesoporous catalyst of Ag/SBA-15 modified with ZnO and CeO 2 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 CeO 2 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 N 2 physical adsorption, Fourier transform infrared (FT-IR), scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM-EDX), temperature programmed reduction of hydrogen (H 2 -TPR), X-ray diffraction (XRD), transmission electron microscopy (TEM), temperature programmed desorption (TPD) of NH 3 and CO 2 , 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. CeO 2 could promote the reduction of Ag 2 O and suppress the formation of carbon deposition effectively. In addition, doping ZnO and CeO 2 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–CeO 2 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. [ABSTRACT FROM AUTHOR]

An efficient catalyst of Cu/MIL-101 modified with CeO 2 for the conversion of biomass-derived glycerol with aniline to 3-methylindole was constructed with the yield of the aimed product up to 59%. The characterizations revealed that the addition CeO 2 to Cu/MIL-101 not only improved the dispersion of Cu particles, but also inhibited the sintering of active component, meanwhile, the number of weak acid sites of the catalyst was also greatly increased, which was favorable to the high selectivity of 3-methylindole. Moreover, the catalytic reaction mechanism was studied in depth, which both acetol and 1,2-propanediol were the intermediates in the synthesis of 3-methylindole. Unlabelled Image • Cu/MIL-101 modified with CeO 2 was fabricated for the vapor-phase synthesis of 3-methylindole. • The catalyst exhibited high activity and selectivity with the aimed product yield up to 59%. • CeO 2 could improve the dispersion of active component and inhibit the sintering of Cu particles. • In addition, the addition of CeO 2 also increased the number of weak acid sitesof the catalyst. • The catalytic mechanism for the synthesis of 3-methylindole from glycerol and aniline was studied. [ABSTRACT FROM AUTHOR]