The atomic pair distribution function（PDF） reveals the interatomic distance in a material directly in real-space. It is a very powerful method to characterize the local structure of materials. With the help of the t...The atomic pair distribution function（PDF） reveals the interatomic distance in a material directly in real-space. It is a very powerful method to characterize the local structure of materials. With the help of the third generation synchrotron facility and spallation neutron source worldwide, the PDF method has developed quickly both experimentally and theoretically in recent years. Recently this method was successfully implemented at the Shanghai Synchrotron Radiation Facility（SSRF）. The data quality is very high and this ensures the applicability of the method to study the subtle structural changes in complex materials. In this article, we introduce in detail this new method and show some experimental data we collected.展开更多
Zeolite-supported noble metal nanoparticle(NP)catalysts demonstrate distinctive properties in heterogeneous catalysis reactions.However,due to the limitations of conventional liquid-phase synthesis methods,understandi...Zeolite-supported noble metal nanoparticle(NP)catalysts demonstrate distinctive properties in heterogeneous catalysis reactions.However,due to the limitations of conventional liquid-phase synthesis methods,understanding of the dynamic crystallization mechanism of zeolites on the microscopic scale is still limited.Importantly,it impedes the in-depth establishment of relationship between structure and reactivity.Herein,we successfully develop a unique solvent-free and organic template-free solid-phase synthesis strategy for preparing Pt/ZSM-5 encapsulated structures to investigate the time-resolved dynamic evolution of zeolite crystallization process.Using the time-resolved X-ray atom pair distribution function and the in-situ scanning electron microscopy technique,the“dissolution-recrystallization”transformation mechanism of structural evolution for zeolite is observed.This dynamic mechanism induces AlO_(4)structural distortion in Pt/ZSM-5 encapsulated structure,triggering strong metal-support interaction.The enhancement of Brønsted acid density and the cationic of Pt mediates the process of cracking of C–C bonds and hydrogenation of C=C bonds.Pt NPs confined in mesoporous pores of ZSM-5 improve the mass transfer efficiency of reaction intermediates.Therefore,Pt/ZSM-5 exhibits remarkable polyethylene hydrocracking performance,achieving approximately 90%conversion and higher liquid fuel selectivity.The complementary analysis of multimodal spectroscopy and in-situ imaging techniques advance our fundamental understanding of structure-activity relationships in zeolite-supported noble metal NPs catalysts.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.U1232112)the National Key Basic Research Program of China(Grant No.2012CB825700)
文摘The atomic pair distribution function（PDF） reveals the interatomic distance in a material directly in real-space. It is a very powerful method to characterize the local structure of materials. With the help of the third generation synchrotron facility and spallation neutron source worldwide, the PDF method has developed quickly both experimentally and theoretically in recent years. Recently this method was successfully implemented at the Shanghai Synchrotron Radiation Facility（SSRF）. The data quality is very high and this ensures the applicability of the method to study the subtle structural changes in complex materials. In this article, we introduce in detail this new method and show some experimental data we collected.
基金the financial support provided by the National Natural Science Foundation of China(grant no.52161145403)the Iran National Science Foundation(grant no.4001399)the Research Fund of Shenyang National Laboratory for Materials Science.
文摘Zeolite-supported noble metal nanoparticle(NP)catalysts demonstrate distinctive properties in heterogeneous catalysis reactions.However,due to the limitations of conventional liquid-phase synthesis methods,understanding of the dynamic crystallization mechanism of zeolites on the microscopic scale is still limited.Importantly,it impedes the in-depth establishment of relationship between structure and reactivity.Herein,we successfully develop a unique solvent-free and organic template-free solid-phase synthesis strategy for preparing Pt/ZSM-5 encapsulated structures to investigate the time-resolved dynamic evolution of zeolite crystallization process.Using the time-resolved X-ray atom pair distribution function and the in-situ scanning electron microscopy technique,the“dissolution-recrystallization”transformation mechanism of structural evolution for zeolite is observed.This dynamic mechanism induces AlO_(4)structural distortion in Pt/ZSM-5 encapsulated structure,triggering strong metal-support interaction.The enhancement of Brønsted acid density and the cationic of Pt mediates the process of cracking of C–C bonds and hydrogenation of C=C bonds.Pt NPs confined in mesoporous pores of ZSM-5 improve the mass transfer efficiency of reaction intermediates.Therefore,Pt/ZSM-5 exhibits remarkable polyethylene hydrocracking performance,achieving approximately 90%conversion and higher liquid fuel selectivity.The complementary analysis of multimodal spectroscopy and in-situ imaging techniques advance our fundamental understanding of structure-activity relationships in zeolite-supported noble metal NPs catalysts.
