Stepwise Dealumination of Zeolite Βeta at Specific T-Sites Observed with 27 Al MAS and 27 Al MQ MAS NMR
Year: 2000
Type: article
Abstract: Using 27 Al MAS and 27 Al MQ MAS NMR, dealumination of zeolite H-Beta has been observed at specific T-positions in the framework. 27 Al MQ MAS NMR is able to resolve aluminum in the T1 and T2 positions from the other (T3 − T9) positions in the framework. A quantitative analysis of the 27 Al MQ MAS NMR spectra shows that aluminum atoms in positions T1 and T2 resist dealumination and do not adopt an octahedral oxygen coordination. Moreover, it is shown that a heat treatment of 450 °C of NH 4 -Beta gives a single type of fairly symmetric framework octahedral aluminum, which can be reconverted to framework tetrahedral aluminum by ammonia treatment. A more severe heat treatment (550 °C under steam) causes some of the tetrahedral framework aluminum atoms on positions T3−T9 to convert to at least two different types of octahedral aluminum that are connected to the framework. These sites are proposed to be different consecutive steps in the process of framework dealumination of zeolite Beta.
DOI: 10.1021/ja002689d
Institutions: Utrecht University, Delft University of Technology
Language: English
Subfield: Inorganic Chemistry
Field: Chemistry
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W2017464771