Abstract:

The Y zeolite dealumiated by oxalic acid and ammonium oxalate maintained the faujasite structure with a good crystallinity. The OH-IR spectra and chemical analysis showed that there were aluminum vacancies in the framework of the dealuminated Y zeolite. In such a dealuminated Y zeolite, the hydroxyls represented by 3550cm-1 was accessible to pyridine, while not so stable as the hydroxyls represented by 3640cm-1 when they were heated in vacuum. The IR spectra of double probes of Pyridine and CO illustrate the production of extra-framework aluminum species which are related to Lewis acid sites in the process of dehydroxylation. The results of N2 adsorption at low temperature suggest the existence of secondary pores which are much larger than the aluminum vacancies, and this probably resulted from the structure reconstruction.

Key words: Dealuminated Y zeolite, Aluminum vacancy, Secondary pores, Chemical dealuminization