Direct Vapor-Phase Synthesis of Indole: Effect of MgO on the Performance of Cu/SiO2 Catalyst

Magnesia was used as the promoter in the Cu/SiO2 catalyst for direct vapor-phase synthesis of indole from aniline and ethylene glycol. The catalyst was characterized by XRD, H2-TPR, and TG. The results showed that a suitable amount of MgO (i.e., 0.17 mmol/g) remarkably increased the stability and activity of the catalyst. The MgO additive improved the dispersion of copper phases on the silica and prevented them from sintering in the reaction process. There existed an interaction between CuO and MgO, which inhibited the sintering of copper. The MgO promoter could suppress the coking of this copper-based catalyst.