Solid-state NMR study on dealumination mechanism of H-MOR zeolite by high-temperature hydrothermal treatment
Microporous and Mesoporous Materials(2023)
摘要
The acidity of zeolites which plays an important role in various catalytic reactions is closely related to framework aluminum. After dealumination, not only the Si/Al ratio of zeolites increases, but also new aluminum species are generated. Furthermore, the pore structure and catalytic performance of zeolites are affected. High-temperature hydrothermal treatment, as a frequently-used method of dealumination, is widely concerned. However, the dealumination mechanism of zeolite during the hydrothermal treatment is not clear. In this work, the existence of different Al species in H-MOR during the process of high-temperature hydrothermal treatment was confirmed by 27Al MQ MAS NMR. It was found that the second tetrahedrally coordinated framework aluminum (Al(IV)-2) species is the precursor of amorphous non-framework aluminum transformed from framework aluminum of H-MOR during high-temperature hydrothermal treatment. Besides, the 1H -1H DQ-SQ NMR was used to study spatial proximity between different hydroxyl species. Finally, the dealumination process of H-MOR zeolite is revealed: Al(IV)-1 species firstly transformed into Al(IV)-2 species, and then evolved into pentahedrally coordinated aluminum (Al(V)) species and hexahedrally coordinated aluminum (Al(VI)) species.
更多查看译文
关键词
hydrothermal treatment,nmr,solid-state,h-mor,high-temperature
AI 理解论文
溯源树
样例
生成溯源树,研究论文发展脉络
Chat Paper
正在生成论文摘要