Simple jQuery Dropdowns
Please use this identifier to cite or link to this item: http://repository.li.mahidol.ac.th/dspace/handle/123456789/9549
Title: Formation of NH<inf>4</inf><sup>+</sup>at the Brønsted site in SAPO catalysts
Authors: Jumras Limtrakul
Jarungsak Yoinuan
Mahidol University
Keywords: Chemistry;Physics and Astronomy
Issue Date: 15-Jun-1994
Citation: Chemical Physics. Vol.184, No.1-3 (1994), 51-57
Abstract: The catalytic properties of ammonia adsorption on silicoaluminophosphate (SAPO) clusters have been investigated within the framework of the ab initio self-consistent field method. Full optimization of strutures has been carried out at the DZ, DZP and TZ2P levels of theory. Two different types of ammonia adsorption on SAPO framework sites are proposed. In one of these the structures H 3 SiOHA1(OH) 2 OPH 3 ...NH 3 are stablilized on the bridging OH by a single site binding with an interaction energy of - 17.49 kcal/mol. The others is a type of the structure [H 3 SiOA1(OH) 2 OPH 3 ] [NH 4 + ], in which the ammonium cation forms two hydrogen bonds towards the unprotonated framework sites. Other possible structures like a "bifurcated" structure are less stable than the two H-bonded structures by about 0.48 and 0.1 kcal/mol at the DZP and TZ2P basis set levels respectively. This indicates the free rotation of the NH 4 + on the SAPO surface site at room temperature. The interaction energies for the structures [H 3 SiOA1(OH) 2 OPh 3 ] [NH 4 + are more stabe than for the structures H 3 SiOhA1(OH) 2 OPH 3 ...NH 3 by 0.5-1.36 kcal/mol depending on the basis sets. These calculated energy values are an inversion order from the zeolite/NH 3 complexes. Comparison of the SAPO complexes with hydrogen halides, silanol, and zeolite has demonstrated that the hydrogen-form SAPO is at least as acidic as zeolite. © 1994.
URI: https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=21344485412&origin=inward
http://repository.li.mahidol.ac.th/dspace/handle/123456789/9549
ISSN: 03010104
Appears in Collections:Scopus 1991-2000

Files in This Item:
There are no files associated with this item.


Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.