Vapor-Phase Synthesis of 3-Methylindole over Fe-, Co-, or Ni-Promoted Ag/SiO2 Catalysts

Fe, Co, or Ni as a promoter was added into the Ag/SiO2 catalyst for the vapor-phase synthesis of 3-methylindole from aniline and 1,2-propanediol. The promoted Ag/SiO2 catalysts were characterized by X-ray diffraction, H2 temperature-programmed reduction, and thermogravimetry. The results indicated that the addition of Fe or Ni to Ag/SiO2 was favorable for the increase of the catalyst selectivity. Among them, Fe could reinforce the interaction between the silver active component and the support and greatly promote the dispersion of silver particles on the support, which resulted in the remarkable increase in the initial activity of the catalyst. Adding Co or Ni to Ag/SiO2 promoted the sintering of silver during the reaction although it reduced the coking a little. As a result, the stability of the catalysts decreased.