The Effect Of ZnO And CeO₂ Promoters On The Performance Of Ag/SBA-15 Catalyst For The Vapor-phase Synthesis Of 3-Methylhydrazine From Glycerol And Aniline

3-methylindole,an important indole derivative,is widely used in many fields such as industry,agriculture and medicine.The preparation of 3-methylindole in efficiently,cheaply and environmental protection is the difficulty and focus of research.Catalytic synthesis of3-methylindole from glycerol and aniline as raw materials over a silver-based catalyst meets the cheaply and greenly chemistry concept and now is the best manner for the synthesis of3-methylindole.In this paper,the reaction of gas-phase catalytic synthesis of 3-methylindole from glycerol and aniline over Ag/SBA-15-ZnO and Ag/SBA-15-ZnO-CeO₂ was studied.The SBA-15material was prepared by hydrothermal synthesis method,and the promoters of ZnO and CeO₂ were sequentially loaded on the SBA-15 by equivalent-volume impregnation method,and the active component silver was loaded afterwards.The catalytic reaction was carried out on the atmospheric gas solid reaction device.The catalysts weres characterized by X-ray diffraction?XRD?,temperature programmed reduction of H₂?H₂-TPR?,temperature programmed desorption?TPD?of NH₃ and CO₂?NH₃-TPD,CO₂-TPD?,transmission electron microscope?TEM?,inductively coupled plasma?ICP?,thermogravimetric and differential thermal analysis?TG-DTA?methods.The results showed that the ZnO promoter not only increased the dispersion of the active component Ag on the carrier,but also inhibited the sintering of Ag particles although the acidity of catalyst enhanced.The activity and selectivity of Ag/SBA-15-ZnO?1.000 mmol/g of Ag loading,1.000 mmol/g of ZnO content?catalyst were the best under the following conditions:the reduction temperature of 180?,the ratio of reduction gas of N₂:H₂=15:15?mL/min?,the catalytic reaction temperature of 220?,the ratio of reacting gas mixture of N₂:steam:H₂=9:16:15?mL/min?,which the yield of 3-methylindole was 45%and the selection rate of 3-methylindole was 52%.The effect of CeO₂ on the structure and performance of the catalyst was investigated by introducing CeO₂ promoter into Ag/SBA-15-ZnO using various characterization methods.The results showed that although CeO₂ promoter was not conducive to the dispersion of active component Ag on the surface of the SBA-15,it could reduce the acidity of the catalyst and thus inhibited the formation of carbon deposition.Under the conditions that the content of CeO₂ promoter of 0.050 mmol/g,the reduction temperature of 170?,the reduction gas ratio of N₂:H₂=15:15?mL/min?,the catalytic reaction temperature of 210?and the reaction gas mixture ratio of N₂:steam:H₂=9:16:15?mL/min?,the activity and selectivity of Ag/SBA-15-Zn O-CeO₂ catalyst were the best,which the yield of 3-methylindole was up to 62%and the selection rate of 3-methylindole was 75%.The yield of 3-methylindole was decreased by 9%when Ag/SBA-15-ZnO-CeO₂ catalyst was regenerated and reused 5 times.The reaction mechanism of 3-methylphenyl for the gas-solid phase synthesis from aniline and glycerol over Ag/SBA-15-ZnO-CeO₂ catalyst was proposed based on the GC-MS analysis of the reaction products of aniline with glycerol and gas chromatography analysis for the reaction products of the hydrogenolysis of glycerol,the catalytic conversion of acetol,as well as the catalytic reaction products of aniline with acetol or 1,2-propanediol..