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 (NiPxSy) 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.

摘要采用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873 K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(NiPxSy), 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. 

H2S/H2 treatment improved the turnover frequency of hydrodechlorination on Ni2P/SiO2. This is ascribed to an increased electron deficiency of Ni sites and a greater amount of spilt-over hydrogen species.Figure optionsDownload as PowerPoint slide