磷对预硫化型NiMo/Al2O3催化剂加氢脱硫脱氮性能的影响

摘要

利用等体积浸渍法制备了不同磷含量的预硫化型NiMo/Al2O3催化剂,并利用XRD、BET、TPR和HRTEM等分析方法对其进行了表征,研究了磷对其加氢脱硫脱氮性能的影响.结果表明,由于预硫化型NiMo加氢催化剂上活性组分和载体的相互作用较弱,MoS2或Ni-Mo-S相主要以TypeⅡ形式存在,磷通过增加MoS2的堆积层数、减小片晶长度提高了MoS2的分散度.TPR结果表明磷仅提高了金属硫化物中Ni-Mo-S相的比例,而对Ni-Mo-S相和体相MoS2中的金属-硫键的键合强度没有影响.NiMoP-1.2催化剂(磷负载量为1.2%)表面MoS2的分散度最高,同时也具有最高的加氢脱硫(HDS)选择性和加氢脱氮(HDN)活性;过高磷含量(NiMoP-1.8,磷负载量为1.8%)则造成MoS2分散度降低,催化剂的比表面积、孔径和孔容也减小,导致其HDS和HDN反应性能下降.%Phosphorus promoted presulfided NiMo/A12 O3 catalysts were prepared by successive incipient wemess impregnation and characterized by XRD, N2-physisorption, TPR and HRTEM. The effect of phosphorus on the hydrodesulfurization ( HDS ) hydrodenitrogenation (HDN) performance of the presulfided NiMo/Al203 catalyst was investigated. The results indicate that the main active phase is type Ⅱ MoS2 or Ni-Mo-S phase because of theft weak interaction with the support. The incorporation of phosphorus in the catalyst enhances the dispersion of MoS2 particles by increasing the stacking number and reducing the slab length.Phosphorus has no influence on the metal-sulfur bonding energies in the Ni-Mo-S phases and bulk MoS2, but it increases the proportion of Ni-Mo-S phases in the metal sulfides. NiMoP-1.2 catalyst ( containing 1.2％ phosphoms) exhibits high hydrogenation (HYD) selectivity in the HDS of dibenzothiophene (DBT) and high HDN ratio of quinoline, which can be attributed to its high dispersion of the active phase. The HYD activity in HDS and HDN ratio on NiMoP-1.8 catalyst with excess phosphorus ( 1.8％ ) is declined due to the aggregation of MoS2 particles and the decrease of the catalyst surface area.