Co-Mo/γ-Al2O3催化剂的原位红外光谱表征研究

采用CO和NO作为探针分子,应用原位红外光谱法(in-situ FT-IR)和程序升温还原(H₂-TPR)对Mo/γ-Al₂O₃和Co-Mo/γ-Al₂O₃加氢催化剂进行表征,并对催化剂进行了加氢脱硫(HDS)活性评价。实验结果表明,在Co-Mo/γ-Al₂O₃催化剂表面存在三个吸附位;在Mo/γ-Al₂O₃催化剂中加入助剂钴对钼吸附位起到显著的改性作用,并且引入新的活性中心,提高了催化剂的催化活性;随着钼含量的增加,活性中心数目逐渐增多;用CO-NO共吸附原位红外光谱研究了Co-Mo/γ-Al₂O₃催化剂表面活性中心的信息,证明不同的Mo中心分别吸附CO和NO,并将它们区分开来,解决了不同活性中心的光谱互相重叠的问题。

An in-situ FT-IR study on the CO and NO co-adsorption on the Co-Mo/γ-Al2O3 catalysts

The active sites of reduced Mo/γ-Al₂O₃ and Co-Mo/γ-Al₂O₃ hydrotreating catalysts were studied by in-situ FT-IR using CO and NO as probe molecules; the results were correlated with their activity in hydrodesulfurization (HDS) and behavior in temperature programmed reduction (H₂-TPR). The results indicate that there exist three main adsorption sites on the surface of Co-Mo/γ-Al₂O₃ catalysts. The addition of cobalt to Mo/γ-Al₂O₃ is able to modify Mo sites and to introduce active Co sites; an increase of the molybdenum content may also increase the number of active sites and improve the catalytic activity of Co-Mo/γ-Al₂O₃. FT-IR spectra of CO and NO co-adsorption is able to distinguish the spectra overlapping of different active sites, which reveals that CO and NO are actually adsorbed on different Mo active sites.