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 re...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 mmolNH3 gcat^-1 h^-1,which is much higher than that of Ru/ZSM-5-IWI(2.13 mmolNH3 gcat^-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.展开更多
As the most important nanoporous material, zeolites, which have intricate micropores, are essential heterogeneous catalysts in industrial processes. Zeolites are generally synthesized with organic templates under hydr...As the most important nanoporous material, zeolites, which have intricate micropores, are essential heterogeneous catalysts in industrial processes. Zeolites are generally synthesized with organic templates under hydrothermal conditions; however, this method is environmentally unfriendly and costly due to the formation of harmful gases and polluted water. This article briefly summarizes the role of organic templates and describes designed routes for the organotemplate-free synthesis of zeolites, aided by zeolite seeds and zeolite seeds solution. Furthermore, this review explicates that the micmpore volume decreases with an increase of the Si/Al ratios in the organotemplate-free synthesis of zeolite products, where Na^＋ exists as an alkali cation. This feature is very important in directing the synthesis of zeolite catalysts with controllable Si/AI ratios under organotemplate-free conditions, and is thus important for the efficient design of zeolites.展开更多
基金supported by the National Science Fund for Distinguished Young Scholars of China(21825801)the National Natural Science Foundation of China(21972019,21978051).
文摘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 mmolNH3 gcat^-1 h^-1,which is much higher than that of Ru/ZSM-5-IWI(2.13 mmolNH3 gcat^-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.
基金This work was supported by the National Natural Science Foundation of China （21273197 and 21333009）.
文摘As the most important nanoporous material, zeolites, which have intricate micropores, are essential heterogeneous catalysts in industrial processes. Zeolites are generally synthesized with organic templates under hydrothermal conditions; however, this method is environmentally unfriendly and costly due to the formation of harmful gases and polluted water. This article briefly summarizes the role of organic templates and describes designed routes for the organotemplate-free synthesis of zeolites, aided by zeolite seeds and zeolite seeds solution. Furthermore, this review explicates that the micmpore volume decreases with an increase of the Si/Al ratios in the organotemplate-free synthesis of zeolite products, where Na^＋ exists as an alkali cation. This feature is very important in directing the synthesis of zeolite catalysts with controllable Si/AI ratios under organotemplate-free conditions, and is thus important for the efficient design of zeolites.
