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发现在同样反应条件下,各种不同类型的加氢精制催化剂还原态比硫化态的吡啶加氢脱氮活性要高得多,某些催化剂的吡啶脱氮率甚至要高出一个数量级以上。通过研究Ni/Ni+W原子比与硫化态和还原态NiO-WO_3/Al_2O_3催化剂吡啶加氢脱氮活性的关系,可以清楚地看出:在硫化态催化剂中钨的硫化物是主要活性组份,而镍的硫化物是助剂;另一方面,在还原态催化剂中主要活性物质是镍。通过对吡啶加氢脱氮反应机理的分析,认识到金属Ni和金属Co不仅具有很高的加氢功能,对氮己环中的C-N键断裂也具有很高的氢解功能。用热重法对NiO-WO_3/Al_2O_3催化剂体系进行还原动力学研究的结果表明:催化剂的还原度和初始还原活化能与吡啶加氢脱氮活性之间有很好的对应关系。对催化剂还原过程的动力学数据分别用Elovich方程和核增长模型进行数据处理,结果表明,Elovich方程能更好地反映催化剂还原的动力学特征。
It was found that under the same reaction conditions, the reduction of various types of hydrotreating catalysts was much higher than that of sulfided pyridine hydrodesulfurization, and the pyridine denitrification rate of some catalysts even exceeded one order of magnitude. By studying the relationship between the Ni / Ni + W atomic ratio and the pyridine hydrodenitrogenation activity of the sulfided and reduced NiO-WO_3 / Al_2O_3 catalysts, it can be clearly seen that the sulfide of tungsten is the main active component in the sulfided catalyst , While nickel sulphides are auxiliaries; on the other hand, the main active species in the reduced catalyst is nickel. Through the analysis of pyridine hydrodenitrogenation reaction mechanism, it is recognized that metal Ni and metal Co not only have high hydrogenation function, but also have high hydrogenolysis function on the C-N bond cleavage in the nitrogen hexahydronaphthalene ring. The results of reduction kinetics of NiO-WO_3 / Al_2O_3 catalyst system by thermogravimetric method show that there is a good correspondence between the reduction degree of catalyst and the initial reduction activation energy and the hydrodenitrogenation activity of pyridine. The kinetic data of the catalyst reduction process were respectively processed by Elovich equation and nuclear growth model. The results show that the Elovich equation can better reflect the kinetic characteristics of the catalyst reduction.