Vapor-Phase Synthesis of 3-Methylindole from Glycerol and Aniline over Cu/SiO<sub>2</sub>-Al<sub>2</sub>O<sub>3</sub> Catalyst Modified by Co or Ni

Abstract

This paper investigated the vapor-phase synthesis of 3-methylindole from glycerol and aniline over the catalyst of Cu/SiO2-Al2O3 modified by Co or Ni. The catalysts were characterized by N2 adsorption, H2 temperature-programmed reduction (H2-TPR), inductively coupled plasma (ICP) emission spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), temperature-programmed desorption of ammonia (NH3-TPD), and thermogravimetric (TG) analysis. The results indicated that adding Co or Ni to Cu/ SiO2-Al2O3 improved the performance of the catalyst and Co exhibited higher efficiency than Ni. The yields of 3-methylindole over Cu-Co/SiO2-Al2O3 and Cu-Ni/SiO2-Al2O3 reached 47% and 45%, respectively at the third hour of reaction and the yields remained 44% and 42% after the catalysts were regenerated six times. The characterizations revealed that the addition of Co or Ni to Cu/SiO2Al2O3 improved the interaction between copper and the support, which promoted the dispersion of Cu particles on the surface of the support, and also prevented the loss of the copper component during the reaction. Furthermore, Co or Ni promoter decreased the amount of the middle-strong acid sites on the catalyst surface, which gave rise to a high selectivity for 3-methylindole, and inhibited the formation of the coke. In addition, Co promoter increased the amount of the weak acid sites on the catalyst, which was favorable for the production of 3methylindole. A catalytic mechanism in which copper and weak acid sites acted together to promote the 2444 BAO Zhuo-Ran et al.: Vapor-Phase Synthesis of 3-Methylindole from Glycerol and Aniline over Co or Ni Promoted No.11 formation of 3-methylindole was proposed.