Vapor-Phase Catalytic Synthesis Of 3-methylindole

3-methylindole which is an important indole derivative, has many uses in the fields of agriculture and medicine. One of the most promising routes, from an economic point of view, seems to be the direct catalytic synthesis from aniline and 1,2-propanediol since this requires just one step from the reactants to 3-methylindole. This method avoids using a large amount of organic solvent and the starting materials are inexpensive. Herein, we report a simple and practical silver catalyzed procedure for the synthesis of 3-methylindole. The Ag/SiO₂ catalyst and the catalysts doped by the ZnO, CeO₂ and La₂O₃ promoters have been characterized by means of H2-TPR,XRD,NH3-TPD,TG and BET.The Ag/SiO₂ catalyst was prepared by incipient wetness impregnation. The preparation of catalysts and the best reaction condition have been optimized. The catalyst is doped by ZnO, CeO₂ and La₂O₃ promoter to increase the catalytic performance. It has been found that ZnO as a structure promoter could improve the stability of the catalyst. The catalyst modified by CeO₂ promoter did not show an efficiently catalysis while the La₂O₃ promoter improved the selectivity of 3-methylindole. The sequence of the promoters adding in the catalyst is investigated. It has been found the best performance of the catalyst was obtained on Ag/SiO₂-La₂O₃-ZnO catalyst and the yield of 3-methylindole could be up to 44%, which is much higher than the best literature result of 12% which is obtained over ZrO₂/SiO₂ catalyst.