Formation of NH<inf>4</inf><sup>+</sup>at the Brønsted site in SAPO catalysts

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 amm...

Full description

Saved in:
Bibliographic Details
Main Authors: Jumras Limtrakul, Jarungsak Yoinuan
Other Authors: Mahidol University
Format: Article
Published: 2018
Subjects:
Online Access:https://repository.li.mahidol.ac.th/handle/123456789/9549
Tags: Add Tag
No Tags, Be the first to tag this record!
Institution: Mahidol University
id th-mahidol.9549
record_format dspace
spelling th-mahidol.95492018-02-27T11:30:19Z Formation of NH<inf>4</inf><sup>+</sup>at the Brønsted site in SAPO catalysts Jumras Limtrakul Jarungsak Yoinuan Mahidol University Chemistry Physics and Astronomy 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. 2018-02-27T04:26:03Z 2018-02-27T04:26:03Z 1994-06-15 Article Chemical Physics. Vol.184, No.1-3 (1994), 51-57 10.1016/0301-0104(94)00083-2 03010104 2-s2.0-21344485412 https://repository.li.mahidol.ac.th/handle/123456789/9549 Mahidol University SCOPUS https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=21344485412&origin=inward
institution Mahidol University
building Mahidol University Library
continent Asia
country Thailand
Thailand
content_provider Mahidol University Library
collection Mahidol University Institutional Repository
topic Chemistry
Physics and Astronomy
spellingShingle Chemistry
Physics and Astronomy
Jumras Limtrakul
Jarungsak Yoinuan
Formation of NH<inf>4</inf><sup>+</sup>at the Brønsted site in SAPO catalysts
description 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.
author2 Mahidol University
author_facet Mahidol University
Jumras Limtrakul
Jarungsak Yoinuan
format Article
author Jumras Limtrakul
Jarungsak Yoinuan
author_sort Jumras Limtrakul
title Formation of NH<inf>4</inf><sup>+</sup>at the Brønsted site in SAPO catalysts
title_short Formation of NH<inf>4</inf><sup>+</sup>at the Brønsted site in SAPO catalysts
title_full Formation of NH<inf>4</inf><sup>+</sup>at the Brønsted site in SAPO catalysts
title_fullStr Formation of NH<inf>4</inf><sup>+</sup>at the Brønsted site in SAPO catalysts
title_full_unstemmed Formation of NH<inf>4</inf><sup>+</sup>at the Brønsted site in SAPO catalysts
title_sort formation of nh<inf>4</inf><sup>+</sup>at the brønsted site in sapo catalysts
publishDate 2018
url https://repository.li.mahidol.ac.th/handle/123456789/9549
_version_ 1763492282945765376