化学分析正电子谱技术的新进展

RECENT APPROACH OF PASCA IN CATALYSIS STUDY

本文是“PASCA技术在催化研究中的新进展”一文的继续,介绍了近三年来PASCA(化学分析正电子谱)技术的新进展。这些进展包括:研究金属-载体之间相互作用的程度及相互作用的性质;表征催化剂表面结构;准确测定金属在氧化铝表面的分散度并判断其分散状态;研究沸石-基质之间的协同作用等。这些进展表明,PASCA技术已经或将成为研究和开发多相催化剂的灵敏、准确而有效的新手段。

PASCA (Positron Annihilation Spectroscopy for Chemical Analysis) is a newly developed surface technique, which is based on the chemical reactions of the probe atom, o-P_s (ortho-positronium), whose lifetimes and intensities depend upon the electron density and the structure of surface active sites of porous materials.In the last few years, PASCA has been extended to the studies of heterogeneous catalysts and their supports, and more experimental results have been obtained, which include:(1)studying the interaction between metal and its support, which strongly affects the surface properties; (2)characterizing the surface structures (formation of surface complexes or compounds); (3) correctly determining the dispersity of metal (Pt, WO_3, MoO_3 and NiO) on catalyst surface and judging its dispersion state; (4)studying the synergism between zeolites and matrixes. All these exhibit that PASCA is a sensitive, accurate and effective technique for catalysis study.