磷化镍和磷化钼催化剂的原位XRD研究

 采用共浸渍法制备了负载型和非负载型磷化镍和磷化钼催化剂前驱体，通过程序升温原位还原法制备了催化剂，并采用原位XRD和TPR技术对催化剂的活性相转化过程进行了研究。由表征结果可以推测，Ni的磷化物的生成过程为：(1)Ni2P2O7→Ni；(2)P前驱体还原，并与Ni生成Ni12P5；(3)Ni12P5进一步还原生成Ni2P。Mo的磷化物的生成过程为：(1)MoO3 →MoO2；(2)MoO2 →Mo；(3)P前驱体还原，并与Mo进一步生成MoP。Ni2P/SiO2和非负载型Ni2P催化剂晶相变化规律基本相似；而MoP/SiO2催化剂在700℃时，只发生相转变的趋势，并无晶体生成。对催化剂Ni2P/SiO2和MoP/SiO2在650℃进行预还原，并在压力2MPa、体积空速3h-1、氢/液体积比300/1条件下，以二苯并噻吩(DBT)和喹啉(Q)为模型化合物考察了催化剂Ni2P/SiO2和MoP/SiO2的加氢脱硫和加氢脱氮活性。结果表明，Ni2P/SiO2催化剂的加氢脱硫和脱氮活性远高于MoP/SiO2催化剂。

IN-SITU XRD STUDY OF NICKEL PHOSPHIDE AND MOLYBDENUM PHOSPHIDE CATALYSTS

Nickel phosphide and molybdenum phosphide catalysts were prepared via in-situ temperature-programmed reduction method of oxidic precursors in H2 in a fixed bed flowing micro-reactor. The precursors were obtained by co-impregnation method. The active phase transformation of the phosphide catalysts were characterized by means of in-situ XRD and TPR technique. The results indicated that the phase transformation process of nickel phosphide is (1)Ni2P2O7→Ni;(2)the reduction precursor of P, and the interaction of P with Ni to produce Ni12P5;(3)Ni12P5 further convert to Ni2P. While the phase transformation of molybdenum phosphide is (1)MoO3→MoO2;(2)MoO2→Mo; (3)the reduction precursor of P, and the interaction P with Mo to produce MoP. The phase transformation process of Ni2P/SiO2 is similar to that of unsupported-Ni2P. At 700℃,MoP/SiO2 only has the trend of phase transformation, but MoP crystalline phase was not observed in XRD pattern. The hydrodesulfurization (HDS) and hydrodenitrogenation (HDN) performance were evaluated in the fixed bed flowing micro-reactor using dibenzothiophene(DBT) and quinoline(Q) as model compounds at 320℃ or 300℃, 2.0MPa, LHSV 3h-1 and H2/liquid 300/1 (V/V). The results indicated that Ni2P/SiO2 has higher HDS and HDN activity than MoP/SiO2.