Co或Ni促进的Cu/SiO2-Al2O3催化剂上丙三醇和苯胺气相合成3-甲基吲哚

对丙三醇和苯胺在Co或Ni促进的Cu/SiO2-Al2O3催化剂上气相合成3-甲基吲哚进行了研究.采用N2吸附、氢气程序升温还原(H2-TPR)、电感耦合等离子体(ICP)发射光谱、X射线衍射(XRD)、透射电子显微镜(TEM)、氨程序升温脱附(NH3-TPD)及热重(TG)分析等技术对催化剂进行了表征.结果表明,向Cu/SiO2-Al2O3催化剂加入钴或镍助剂改善了催化剂的催化性能,钴比镍更加有效.在催化剂Cu-Co/SiO2-Al2O3和Cu-Ni/SiO2-Al2O3上,反应第3 h,3-甲基吲哚收率分别达到47%和45%,而且催化剂经过6次再生收率仍能达到44%和42%.各种表征表明,向Cu/SiO2-Al2O3催化剂加入钴或镍助剂能增强铜和载体之间的相互作用,其结果不仅促进了铜粒子在载体表面的分散度,而且有效减少了反应过程中铜组分的流失.另外,加入钴或镍助剂还能减少催化剂的中强酸中心数,从而提高3-甲基吲哚的选择性,并且抑制积炭的形成.此外,钴助剂还能增加催化剂的弱酸中心数,促进3-甲基吲哚的生成.提出了金属铜与弱酸中心共同促进3-甲基吲哚合成的催化反应机理.

Vapor-Phase Synthesis of 3-Methylindole from Glycerol and Aniline over Cu/SiO2-Al2O3 Catalyst Modified by Co or Ni

This paper investigated the vapor-phase synthesis of 3-methylindole from glycerol and aniline over the catalyst of Cu/SiO₂-Al₂O₃ modified by Co or Ni. The catalysts were characterized by N₂ adsorption, H₂ temperature-programmed reduction (H₂-TPR), inductively coupled plasma (ICP) emission spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), temperature-programmed desorption of ammonia (NH₃-TPD), and thermogravimetric (TG) analysis. The results indicated that adding Co or Ni to Cu/SiO₂-Al₂O₃ improved the performance of the catalyst and Co exhibited higher efficiency than Ni. The yields of 3-methylindole over Cu-Co/SiO₂-Al₂O₃ and Cu-Ni/SiO₂-Al₂O₃ reached 47% and 45%, respectively at the third hour of reaction and the yields remained 44% and 42% after the catalysts were regenerated six times. The characterizations revealed that the addition of Co or Ni to Cu/SiO₂-Al₂O₃ improved the interaction between copper and the support, which promoted the dispersion of Cu particles on the surface of the support, and also prevented the loss of the copper component during the reaction. Furthermore, Co or Ni promoter decreased the amount of the middle-strong acid sites on the catalyst surface, which gave rise to a high selectivity for 3-methylindole, and inhibited the formation of the coke. In addition, Co promoter increased the amount of the weak acid sites on the catalyst, which was favorable for the production of 3-methylindole. Acatalytic mechanism in which copper and weak acid sites acted together to promote the formation of 3-methylindole was proposed.