The role of defects in high-silica zeolite hydrolysis and framework healing

Kód výsledku v IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F00216208%3A11310%2F24%3A10481978" target="_blank" >RIV/00216208:11310/24:10481978 - isvavai.cz</a>

Výsledek na webu

<a href="https://verso.is.cuni.cz/pub/verso.fpl?fname=obd_publikace_handle&handle=vepGupeCeh" target="_blank" >https://verso.is.cuni.cz/pub/verso.fpl?fname=obd_publikace_handle&handle=vepGupeCeh</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1016/j.micromeso.2024.113219" target="_blank" >10.1016/j.micromeso.2024.113219</a>

Jazyk výsledku

angličtina

Název v původním jazyce

The role of defects in high-silica zeolite hydrolysis and framework healing

Popis výsledku v původním jazyce

The stability of high silica zeolites under standard laboratory and mild steaming conditions is understood to be due to the lack of hydrophilic Al-O-Si moieties, which can be targeted by water via hydrolysis reactions with relatively low barriers. However, in hydrophobic high-silica and siliceous frameworks, the specific interactions between water and the internal framework sites are incompletely understood. In particular, the behaviour of common internal defects, including partial hydrolysis species and silanol nests are not established, despite their expected role in accelerating the decomposition of the framework. In this work, we utilise machine learning potentials combined with density functional calculations to rigorously sample the hydrolysis processes in siliceous zeolites with topologies CHA and MFI under low water conditions and quantify the effect of defects. Internal silanol defect sites are found to accelerate zeolite decomposition primarily by bypassing the initial, highbarrier hydrolysis step. Subsequent steps proceed with lower reaction barriers. However, all reaction steps are found to be highly activated, and unlikely to occur rapidly at room temperature under conditions of low internal water concentration. Exchange-healing routes, which reverse hydrolysis while incorporating oxygen from water molecules are found to be competitive along the entire hydrolysis pathway in CHA, providing an additional source of stabilization against hydrolytic decomposition.

Název v anglickém jazyce

The role of defects in high-silica zeolite hydrolysis and framework healing

Popis výsledku anglicky

The stability of high silica zeolites under standard laboratory and mild steaming conditions is understood to be due to the lack of hydrophilic Al-O-Si moieties, which can be targeted by water via hydrolysis reactions with relatively low barriers. However, in hydrophobic high-silica and siliceous frameworks, the specific interactions between water and the internal framework sites are incompletely understood. In particular, the behaviour of common internal defects, including partial hydrolysis species and silanol nests are not established, despite their expected role in accelerating the decomposition of the framework. In this work, we utilise machine learning potentials combined with density functional calculations to rigorously sample the hydrolysis processes in siliceous zeolites with topologies CHA and MFI under low water conditions and quantify the effect of defects. Internal silanol defect sites are found to accelerate zeolite decomposition primarily by bypassing the initial, highbarrier hydrolysis step. Subsequent steps proceed with lower reaction barriers. However, all reaction steps are found to be highly activated, and unlikely to occur rapidly at room temperature under conditions of low internal water concentration. Exchange-healing routes, which reverse hydrolysis while incorporating oxygen from water molecules are found to be competitive along the entire hydrolysis pathway in CHA, providing an additional source of stabilization against hydrolytic decomposition.

Druh

J_imp - Článek v periodiku v databázi Web of Science

CEP obor

—

OECD FORD obor

10403 - Physical chemistry

Projekt

Výsledek vznikl pri realizaci vícero projektů. Více informací v záložce Projekty.

Návaznosti

P - Projekt vyzkumu a vyvoje financovany z verejnych zdroju (s odkazem do CEP)

Rok uplatnění

2024

Kód důvěrnosti údajů

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů

Název periodika

Microporous and Mesoporous Materials

ISSN

1387-1811

e-ISSN

1873-3093

Svazek periodika

377

Číslo periodika v rámci svazku

September

Stát vydavatele periodika

NL - Nizozemsko

Počet stran výsledku

7

Strana od-do

113219

Kód UT WoS článku

001259192300001

EID výsledku v databázi Scopus

2-s2.0-85196172321