【摘要】 金属Ru具有较低的N₂活化解离能,被广泛应用于合成氨反应,但Ru表面较高的自由能导致颗粒易团聚成较大的纳米簇,如何提高Ru纳米粒子在合成氨反应中的热稳定性是亟待解决的问题.为此,本文提出以含Ru的ZSM-5为晶种,通过封装的方法获得具有高稳定性的Ru@ZSM-5催化剂.相比于通过传统浸渍法制备的Ru/ZSM-5-IWI催化剂,采用封装法获得的Ru@ZSM-5催化剂,不仅具有较高的合成氨反应速率(在400℃和1MPa,Ru@ZSM-5和Ru/ZSM-5-IWI的NH₃合成反应速率分别为5.84和2.13 mmol NH₃ g_cat^-1h^-1),而且具有较优异高温稳定性.透射电子显微镜（TEM）、X射线光电子能谱（XPS）和X射线吸收精细结构谱（XAFS）等分析结果表明, Ru@ZSM-5催化剂具有优异的合成氨性能与其暴露较多的Ru⁰活性位点及较强的抗烧结能力密切关联.该研究为设计和制备高稳定性Ru基催化剂开辟了新的途径.更多还原

【Abstract】 To stabilize Ru nanoparticles against sintering is an urgent problem in the utilization of Ru-based catalysts for NH₃ synthesis. In the present study, we used Ru-containing ZSM-5 as seeds to crystallize ZSM-5, and the resulted Ru@ZSM-5 catalyst is highly resistant against Ru sintering. According to the results of diffuse reflectance infrared fourier transform spectroscopy（DRIFTS） and transmission electron microscopy（TEM） analyses, the average size of Ru nanoparticles is around 3.6 nm, which is smaller than that of Ru/ZSM-5-IWI prepared by incipient wetness impregnation. In NH₃ synthesis（N₂:H₂= 1:3） at 400 ℃ and 1 MPa, Ru@ZSM-5 displays a formation rate of 5.84 mmol_NH3 g_cat^-1 h^-1, which is much higher than that of Ru/ZSM-5-IWI(2.13 mmol_NH3 g_cat^-1 h^-1). According to the results of TEM, N₂-temperatureprogrammed desorption（N₂-TPD）, X-ray photoelectron spectroscopy（XPS） and X-ray absorption fine structure（XAFS） studies, it is deduced that the superior performance of Ru@ZSM-5 is attributable to the small particle size and the ample existence of metallic Ru⁰ sites. This method of zeolite encapsulation is a feasible way to stabilize Ru nanoparticles for NH₃ synthesis.更多还原