还原条件对Ni2P/SiO2催化剂催化氯苯气相加氢脱氯反应性能的影响

采用程序升温还原方法制备了Ni2P/SiO2催化剂,考察了还原条件对催化剂结构及其催化氯苯加氢脱氯反应性能的影响.结果表明,还原条件(氢气流速、还原温度及时间)对Ni2P/SiO2催化剂的比表面积、孔结构及Ni2P晶粒大小没有明显的影响,但催化剂表面的磷含量差异较大.Ni2P/SiO2催化剂在氯苯加氢脱氯反应过程中存在一定的诱导期,而采用提高还原温度和H2空速以及延长还原时间等方法制备的催化剂可以缩短反应诱导期.初步分析认为磷覆盖催化剂活性中心是产生诱导期的主要原因,而还原条件会影响催化剂的表面性质.Ni2P/SiO2催化剂具有良好的加氢脱氯活性及稳定性,在573K,H2流量75ml/min及氯苯流量3ml/h的条件下,该催化剂上氯苯转化率在130h内保持在99%以上.

Influence of Reduction Conditions on the Catalytic Activity of Ni2P/SiO2 for Gas-Phase Hydrodechlorination of Chlorobenzene

The silica-supported nickel phosphide,Ni2P/SiO2,was prepared by the temperature-programmed reduction method,and the influence of reduction conditions(H2 flow rate,reduction temperature,and time)on the textural properties of the catalyst was investigated.There was no remarkable difference in BET specific surface area,pore structure,and the Ni2P crystallite size for the catalysts prepared under different reduction conditions,whereas the P contents on the catalyst surface differed obviously.The catalysts showed an induction period for the hydrodechlorination,which might be due to the excess P covering the active sites.The induction period could be shortened by increasing the H2 flow rate,reduction temperature,and reduction time during the catalyst preparation,indicating that reduction conditions influenced the surface properties of the catalyst.Ni2P/SiO2 showed excellent activity and stability for the hydrodechlorination of chlorobenzene.Under the conditions of 573 K,H2 flow rate of 75 ml/min,and chlorobenzene flow rate of 3 ml/h,the chlorobenzene conversion maintained above 99% during 130 h reaction over the Ni2P/SiO2 catalyst.