Abstract: The promoting effect of ZnO or K₂O promoter on Cu/SiO₂-Al₂O₃ catalyst for the vapor-phase synthesis of 3-methylindole from glycerol and aniline was studied. The catalyst samples were characterized by X-ray diffraction, transmission electron microscopy, H₂ temperature-programmed reduction, NH₃ temperature-programmed desorption, and thermogravimetric and differential thermal analysis. The results indicated that the addition of an appropriate amount ZnO or K₂O to Cu/SiO₂-Al₂O₃ increased the activity and selectivity as well as the stability of the catalyst remarkably, and ZnO exhibited better efficiency than K₂O. ZnO not only reinforced the interaction between the active component and the support, promoted the dispersion of copper particles on the support, but also inhibited the sintering of copper particles during the reaction. K₂O could suppress the sintering of copper particles during the reaction to some extent although it did not improve the dispersion of copper particles on the support. The addition of ZnO or K₂O to Cu/SiO₂-Al₂O₃ increased the number of weak acid sites in different degrees, which promoted the synthesis of 3-methylindole.

Key words: copper, silica, alumina, zinc oxide, potassium oxide, 3-methylindole, glycerol, aniline