以SiO_2为载体的磷化钼催化剂上喹啉的加氢脱氮反应

HYDRODENITROGENATION OF QUINOLINE CATALYZED BY SiO_2-SUPPORTED MOLYBDENUM PHOSPHIDE

通过原位还原方法制备了以SiO2为载体的磷化钼（MoP）催化剂。采用喹啉作为模型化合物，在300～360℃、5．0 MPa和MHSV为21 h^-1的条件下，考察了MoP／SIO2催化剂的加氢脱氮（HDN）反应活性和产物分布。结果表明，MoP／SiO2催化喹啉的HDN反应中。喹啉首先加氢饱和生成十氢喹啉（DHQ），然后再开环并脱氮生成丙基环基烷（PCH）。同时，考察了二苯并噻吩（DBT）对MoP／SiO2催化喹啉的HDN反应活性及反应路径的影响。未加DBT时。MoP／SiO2催化剂表现出较高的HDN活性和加氢能力。C—N键的氢解是HDN反应速率的控制步骤。加入DBT后，即使加入的量很少，喹啉的脱氮率也明显降低。DBT对MoP／SiO2催化喹啉的HDN反应的影响主要体现在对喹啉的加氢反应路径的抑制，说明DBT和喹啉在MoP／SiO2催化剂的加氢活性位上存在着强烈的竞争吸附，此时HDN反应速率的控制步骤由氢解步骤转为加氢步骤。

Silica-supported molybdenum phosphides（MoP/SiO2） from their oxidic precursors were prepared in a fixed bed reactor by in-situ reduction method. The hydrodenitrogenation （HDN） activities of the catalysts and HDN product molar distribution were studied by using 1% （mass fraction） quinoline in decalin as the feed at the temperature range of 300-360℃, pressure of 5.0 MPa, MHSV of 21 h 1. It was shown that in the HDN reaction quinoline was fully saturated to be decahydroquinoline（DHQ） and then the hydrogenated heterocyclic ring was broken to form propylcyclohexane（PCH）. The effects of dibenzothiophen（DBT） on the HDN activities and reaction pathway were also tested. The results showed that MoP/SiO2 catalysts presented better denitrogenation and hydrogenation activities in HDN of quinoline in the absence of DBT, the rate-control step of HDN reaction rate might be C-N bond hydrogenolysis of DHQ, while in the presence of DBT, even at a small amount, dramatic decrease in HDN activity of quinoline was occured. The detrimental effect of DBT on HDN of quinoline was mainly characterized by the inhibition on the hydrogenation route in the quinoline reaction network, mostly resulted from the competitive adsorption of DBT with quinoline on the hydrogenation active sites, and the control step of HDN reation rate changed from C-N bond hydrogenolysis to hydrogenation of quinoline.