磷化镍和磷化钼催化剂的原位XRD研究

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

采用共浸渍法制备了SiO2负载型和非负载型磷化镍和磷化钼催化剂前驱体,再以程序升温原位还原法制备了催化剂,并采用原位XRD和TPR技术研究了催化剂的活性相转化过程。以二苯并噻吩(DBT)和喹啉(Q)为模型化合物,考察了Ni2P/SiO2和MoP/SiO2催化剂的加氢脱硫和加氢脱氮活性。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催化剂的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。在压力2 MPa、体积空速3 h-1、氢/液体积比300的条件下,以二苯并噻吩(DBT)和喹啉(Q)模型化合物为原料时,Ni2P/SiO2催化剂的加氢脱硫和脱氮活性远高于MoP/SiO2催化剂。

The precursors of nickel phosphide and molybdenum phosphide catalysts were prepared by co-impregnation method. Nickel phosphide and molybdenum phosphide catalysts were then obtained via in-situ temperature-programmed reduction method. The active phase transformation of the phosphide catalysts was characterized by means of in-situ XRD and TPR technique. The hydrodesulfurization （HDS） and hydrodenitrogenation （HDN） performances of these catalysts were evaluated in the fixed bed flowing micro-reactor with dibenzothiophene（DBT） and quinoline（Q） as model compounds. The results indicated that the phase transformation process of nickel phosphide was as follows： （1） Ni2P2O7→Ni; （2）The precursor of P was reduced, and then Ni12 P5 was produced through the interaction of P with Ni; （3）Ni12P5 further converted to Ni2P. The phase transformation of molybdenum phosphide was as follows. （1） MoO3 → MoO2 ; （2） MoO2 → Mo; （3）The precursor of P was reduced, and then MoP was produced through the interaction of P with Mo. The phase transformation process of Ni2P/SiO2 was similar to that of unsupported-Ni2P. At 700℃, MoP/SiO2 only showed the trend of phase transformation, but no MoP crystalline phase was observed in XRD pattern. At the reaction conditions of 320℃ or 300℃, 2.0 MPa, LHSV 3 h 1 and H2/liquid volume ratio 300, and with dibenzothiophene （DBT） and quinoline （Q） as modelcompounds, HDS and HDN activity of Ni2P/SiO2 was higher than that of MoP/SiO2.