CuO-CuAl₂O₄ Catalyst for Synthesis of 1-Methylindole by Alcohol Amine Method

Cu-based catalysts used for the vapor-phase synthesis of 1-methylindole from N-methylaniline and ethylene glycol are prone to Cu sintering and deactivation under the reaction conditions. In this work, CuO-CuAl₂O₄ catalysts were prepared by a coprecipitation method and applied to the synthesis of 1-methylindole via alcohol amine route. The effects of calcination temperature and Cu/Al molar ratio on the textural properties, crystalline phases, reducibility, surface composition, and catalytic performance were investigated. The catalyst calcined at 700°C with a Cu/Al molar ratio of 1:2 showed the highest 1-methylindole yield, exceeding 85% under the investigated conditions. Characterization results indicate that an appropriate balance between non-spinel CuO and CuAl₂O₄ spinel improves the reducibility of Cu species and reduces the agglomeration of Cu particles to a certain degree. The catalyst maintained a 1-methylindole yield above 80% during the first 8 h, while gradual deactivation was observed during the 28 h stability test.