Utilize este identificador para referenciar este registo:
|Título:||Spectroscopic characterization of hydroxyl groups in SAPO-40. Part I: Study of the template-free samples and their interaction with ammonia|
Lourenço, J. P.
|Editora:||American Chemical Society|
|Citação:||Onida, B.; Gabelica, Z.; Lourenço, J.P.; Garrone, E. Spectroscopic characterization of hydroxyl groups in SAPO-40. Part I: Study of the template-free samples and their interaction with ammonia, J. Phys. Chem. 100, 11072-11079, 1996.|
|Resumo:||FTIR, MAS 1H-NMR, and molecular graphics data are reported concerning the hydroxyl species in a series of SAPO-40 samples with variable Si contents, as well as FTIR data concerning the interaction of ammonia with the different acid sites. Up to seven types of Si(OH)Al Brønsted sites are present, mainly differing by the O-H stretching frequency. Three high-frequency bands (3637-3624 cm-1) correspond to hydroxyls located in the 12-member channels and two low-frequency bands (3559 and 3528 cm-1) to OH species in eight-member rings and side pockets of the AFR structure. Two bands at exceptionally low frequency (3485 and 3445 cm-1 ) are due to OH species interacting with silica islands. All low-frequency bands behave with temperature as H-bonded species. All types of hydroxyls form ammonium ions, the thermal decomposition of which shows some difference in acidity among the OH species. IR evidence indicates that NH4 + species interact strongly with the basic oxygen atoms of the lattice. No Lewis sites were evidenced by ammonia adsorption.|
|Aparece nas colecções:||FCT2-Artigos (em revistas ou actas indexadas)|
Ficheiros deste registo:
|JPC, 1996.pdf||542,93 kB||Adobe PDF||Ver/Abrir Acesso Restrito. Solicitar cópia ao autor!|
Todos os registos no repositório estão protegidos por leis de copyright, com todos os direitos reservados.