文献类型：期刊文献

英文题名：Insightful understanding of the correlations of the microstructure and catalytic performances of Pd@chitosan membrane catalysts studied by positron annihilation spectroscopy

作者：Liu, Qi[1];Xu, Mengdie[1];Zhao, Jing[1];Wang, Yudong[1];Qi, Chenze[1];Zeng, Minfeng[1];Xia, Rui[2];Cao, Xingzhong[2];Wang, Baoyi[2]

机构：[1]Shaoxing Univ, Zhejiang Key Lab Alternat Technol Fine Chem Proc, Shaoxing 312000, Peoples R China;[2]Chinese Acad Sci, Inst High Energy Phys, Beijing 100049, Peoples R China

年份：2018

卷号：8

期号：6

起止页码：3225

外文期刊名：RSC ADVANCES

收录：SCI-EXPANDED(收录号：WOS:000423304700052)、、EI(收录号：20180404678888)、Scopus(收录号：2-s2.0-85040862463)、WOS

基金：The authors acknowledge the financial support from the National Natural Science Foundation of China (grant number: No. 11475114 and 11575117), Zhejiang Province Fundamental Public Welfare Research Project (grant number: No. LGG18E030004), and High-level Talents Further Study Abroad Support Plan of Shaoxing City. We would like to thank Prof. Y. Lin (Institute of Materials Science and Department of Chemistry, University of Connecticut) for his helpful discussions.

语种：英文

外文关键词：Chemical reactions - Chitosan - Free volume - Membranes - Microstructure - Molecules - Palladium - Palladium compounds - Positron annihilation spectroscopy - Positrons - Recycling

外文摘要：In this study, the catalytic performances of palladium supported on chitosan (Pd@CS) membrane heterogeneous catalysts have been studied from the aspects of free volume by positron annihilation Lifetime spectroscopy (PALS). The results showed that the variation in free volume hole size of the Pd@CS membrane catalyst was closely associated with microstructure evolutions, such as increase of Pd content, valence transition of Pd by reduction treatment, solvent swelling, physical aging during catalyst recycling, and so on. The PALS resuLts showed that both the mean free volume hole size of the Pd@CS membrane in the dry or swollen state (analyzed by the LT program) and its distribution (analyzed by the MELT program) are smaller than the molecue size of the reactants and products in the catalysis reaction. However, the resuLts showed that the Pd@CS membrane catalyst has excellent catalytic activity for the Heck coupling reaction of all the reactants with different molecule size. It was revealed that the molecule transport channels of the Pd@CS membrane catalyst in the reaction at high temperature was through a number of instantaneously connected free volume holes rather than a single free volume hole. This hypothesis was powerfully supported by the catalytic activity assessment resuLts of the CS Layer sealed Pd@CS membrane catalyst. Meanwhile, it was confirmed that the Leaching of Pd nanoparticles of the reused Pd@CS membrane catalyst during the recycling process was also through such instantaneously connected free volume holes.