Formation of Paramagnetic Defect Centers in Aluminophosphate Molecular Sieves

Autor:	Suk Bong Hong, Sun Jin Kim, Young Sun Uh
Rok vydání:	1996
Předmět:	Pore size Chemistry General Chemistry Molecular sieve Biochemistry Catalysis law.invention Ring size Paramagnetism Crystallography Colloid and Surface Chemistry law Torr Electron paramagnetic resonance Spectroscopy Spin (physics)
Zdroj:	Journal of the American Chemical Society. 118:8102-8110
ISSN:	1520-5126 0002-7863
Popis:	The formation of paramagnetic defect centers in aluminophosphate (AlPO4) molecular sieves with different structures is investigated by electron spin resonance (ESR) spectroscopy. Distinct differences in the position and number of the ESR signals generated by dehydroxylation of AlPO4 molecular sieves under a vacuum of 10-5 Torr at 773 K clearly show that the nature of the paramagnetic defect centers formed is significantly different in the structure type of the molecular sieves. In addition, it is found that the spin concentration of these defects depends strongly on the pore size of the AlPO4 molecular sieves as well as their hydration level before dehydroxylation. The larger ring size the molecular sieve has, the higher spin concentration of paramagnetic defects it shows. Thus, the extra-large-pore VPI-5 shows the highest spin concentration value among the molecular sieves studied here, which corresponds to 6.4 defects per 1000 unit cells. The ESR results obtained from AlPO4-based molecular sieves contai...
Databáze:	OpenAIRE
Externí odkaz:	https://explore.openaire.eu/search/publication?articleId=doi_________::10652b295dbee2b9dc7397982c74f8c8 https://doi.org/10.1021/ja960419i Zobrazit plný text záznamu