The Effect Of ZnO And MgO Promoters On The Performance Of Cu/γ-Al₂O₃ Catalyst For The Vapor-phase Synthesis Of 3-methylindole From Glycerol And Aniline

3-Methylindole,an important indole derivative,can be used to synthesize a variety of important compounds because of its unique structure and property,and was widely applied in various fields of industry,agriculture and medicine,etc.The catalytic synthesis of 3-methylindole from aniline and biomass-based glycerol is the most promising route at present,which not only satisfies the concept of green chemistry,but also reduces the cost.In this paper,γ-Al₂O_3,which was of excellent performance,was used as support and metal copper was the active component for the vapor-phase synthesis of3-methylindole from glycerol and aniline.The effects of ZnO and MgO promotors to Cu/γ-Al₂O₃ catalyst were investigated.The ZnO and MgO were loaded onto Cu/γ-Al₂O₃ by equivalent-volume immersion method to obtain the copper based catalysts.The vapor-phase catalytic reactions were carried out under normal atmospheric pressure.And the catalysts were characterized by X-ray diffraction（XRD）,temperature programmed reduction of H₂（H₂-TPR）,temperature programmed desorption of NH₃（NH₃-TPD）,and thermogravimetric（TG）to study the mechanism of catalyst.The results indicated that ZnO promotor was beneficial to the reduction of CuO to metal copper and could decrease the middle-strong acid sites of the catalyst,which reduced the amount of carbon deposition during the reaction athough it was not conducive to the dispersion of copper particles on the support.Over Cu/γ-Al₂O₃-ZnO（Cu 0.75 mmol/g,ZnO 0.20 mmol/g）catalyst,the yield of 3-methylindole could reach 40%at the second hour of reaction when the reduction temperature was 250℃,the reduction gas ratio was 1:1（30 m L/min）,the reaction temperature was 260℃,and the flow rate for the reaction mixture gas of steam,H₂ or N₂ was 24,30 or 26 mL/min respectively.The addition of MgO promoter could not only reduce the middle-strong acid sites to inhibite the carbon deposition,but also promote the dispersion of copper particles on the support surface,as a result,the activity,selectivity and stability of the catalyst enhanced greatly.When MgO amount was 0.07 mmol/g,the temperature of reduction and reaction was 260℃,and the flow rate for the reaction mixture gas of steam,H₂ or N₂ was 24,40 or 16 mL/min respectively,Cu/γ-Al₂O₃-ZnO-MgO exhibited good performance with the yield of 3-methylindole up to 53%at the second hour of reaction.After Cu/γ-Al₂O₃-ZnO-MgO catalyst was regenerated and reused 8times,the activity decreased obviously,which the yield of 3-methylindole was low to33%at the second hour of reaction.