On understanding the sequential post-synthetic microwave-assisted dealumination and alkaline treatment of Y zeolite

Systematic investigation was performed to understand the change of physiochemical properties in Y zeolite after the microwave (MW)-assisted dealumination (using mineral acid, HCl, and chelating agent, EDTA4−) and the subsequent alkaline treatment (of the dealuminated zeolites). The findings show that the combination of EDTA4− and hydrogen ions was effective to achieve dealumination of zeolite Y under MW irradiation, which formed complexed framework Al, instead of extra-framework Al (EFAl), to be extracted readily by the sequential alkaline treatment for mesopore formation. Conversely, under the same MW condition, the use of HCl encouraged the formation of EFAl species in the defective Y framework, which did not benefit the mesopore formation. The disclose of the distinct dealumination mechanisms of the MW-assisted method using different agents can benefit the further development of effective MW methods for dealumination of zeolites and/or making mesoporous zeolites.

Keywords: Y zeolite; post-synthetic treatment; dealumination; microwave (MW); NMR