H2S预处理对Ni2P/SiO2催化剂结构及氯苯加氢脱氯性能的影响

采用10% H₂S/H₂对Ni₂P/SiO₂催化剂进行预处理,利用X射线衍射、电感耦合等离子发射光谱、X射线光电子能谱、CO化学吸附、H₂程序升温脱附、NH₃程序升温脱附及活性评价等方法研究了H₂S预处理对催化剂结构和氯苯加氢脱氯反应性能的影响.结果表明,即使在873K进行H₂S预处理,Ni₂P/SiO₂催化剂体相结构及Ni₂P晶粒大小没有发生变化,但导致Ni₂P晶粒表面形成了磷硫镍相(NiP_xS_y),同时使表面溢流氢数量增加.硫物种的存在不仅阻塞了部分镍中心,使催化剂表面镍中心密度降低,也导致镍中心的缺电子性进一步增加.经H₂S预处理后Ni₂P/SiO₂催化剂上氯苯加氢脱氯反应的转化频率(TOF)明显提高,这可能与催化剂表面Ni物种的缺电子性增强及溢流氢数量增多有关.

Effect of H2S pre-treatment on structure and activity of Ni2P/SiO2 catalyst for hydrodechlorination of chlorobenzene

The effect of 10% H₂S/H₂ treatment on the structure of Ni₂P/SiO₂ and its activity for the hydrodechlorination of chlorobenzene was investigated using X-ray diffraction, inductively coupled plasma atomic emission spectroscopy, X-ray photoelectron spectroscopy, CO chemisorption, H₂ temperature-programmed desorption, NH₃ temperature-programmed desorption, and activity tests. The H₂S/H₂ treatment did not change the Ni₂P phase or crystallite size even at temperatures as high as 873 K. However, S species were incorporated in the surface of the Ni₂P crystallites to form surface phosphosulfide (NiP_xS_y) species, which blocked the Ni sites and induced their further electron-deficiency. H₂S/H₂ treatment also led to an increase of spilt-over hydrogen species. The treated Ni₂P/SiO₂ catalyst had higher turnover frequencies in the hydrodechlorination of chlorobenzene than the untreated catalyst. This was ascribed to the increased electron-deficiency of Ni site and a greater amount of spilt-over hydrogen species.