柠檬酸与磷的改性对Ni-Mo/Al_2O_3焦化蜡油加氢脱氮性能的影响

Effect of the Modification by Citric Acid Cooperating With Phosphorus on the Hydrodenitrogenation Performance of Ni-Mo/Al_2O_3 for Coking Gas Oil

以γ-Al_2O_3为载体,Ni-Mo为活性金属组分,采用等体积溶液浸渍法制备了焦化蜡油加氢处理催化剂Ni-Mo/Al_2O_3。在浸渍液中分别加入柠檬酸、磷酸二氢铵,以及同时加入柠檬酸和磷酸二氢铵,得到改性的催化剂Ni-Mo-CA/Al_2O_3、Ni-Mo-P/Al_2O_3和Ni-Mo-P-CA/Al_2O_3,采用NH_3-TPD、H_2-TPR、UV-Vis DRS和HRTEM等手段对制备的催化剂进行了表征,考察了柠檬酸和磷改性对催化剂的性质和加氢脱氮活性的影响。结果表明,磷改性提高了Ni-Mo/Al_2O_3催化剂的表面酸量,但降低了其加氢脱氮活性;柠檬酸的改性提高了Ni-Mo/Al_2O_3催化剂的加氢脱氮活性,但降低了催化剂的表面酸量;柠檬酸-磷的组合改性使Ni-Mo/Al_2O_3催化剂同时具有较高的表面酸量和加氢脱氮活性。柠檬酸-磷的组合改性使Ni-Mo/Al_2O_3催化剂的表面形成了更多的高活性Mo物种,活性金属有着更高的分散性,MoS_2堆垛层数集中分布在2层和3层,从而使其对焦化蜡油的加氢脱氮活性得到了大幅提升。

Ni-Mo/A120a catalysts for coking gas oil （CGO） incipient wetness impregnation method with Ni and Mo as hydrodenitrogenation were prepared by active metals and 1＇-A1203 as support. The Ni-Mo/A1203 catalyst was modified by ammonium dihydrogen phosphate, citric acid and ammonium dihydrogen phosphate cooperating with citric acid during impregnation, respectively. The modified Ni-Mo/A1203 catalysts were named as Ni-Mo-P/AI^O3, Ni-Mo-CA/A1203 and Ni-Mo- P-CA/A1203 catalysts, respectively, and their catalytic performances for coking gas oil hydrodenitrogenation（HDN） were examined. The physical and chemical properties of these catalysts were investigated by NH3-TPD, H2-TPR, UV-Vis DRS and HRTEM. The results indicated that on the surface of Ni-Mo-P/AI203 catalyst the amount of acid was increased and the HDN activity was weakened, while on the surface of Ni-Mo-CA/A1203 catalyst the amount of acidwas decreased and the HDN activity was strengthened, compared with unmodified Ni-Mo/A120~. On the surface of Ni-Mo-P-CA/A12 03 catalyst both the amount of acid increased and HDN activity was remarkably promoted, because more Mo species of high activity were formed, the dispersion of active components was increased and most of MoS2 nanoparticles were dilayered and trilayered.