H/D reactivity and acidity of Bronsted acid sites of MWW zeolites: Comparison with MFI zeolite

Kód výsledku v IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F00216275%3A25310%2F19%3A39914312" target="_blank" >RIV/00216275:25310/19:39914312 - isvavai.cz</a>

Nalezeny alternativní kódy

RIV/61388955:_____/19:00517215 RIV/00216208:11310/19:10403681

Výsledek na webu

<a href="https://www.sciencedirect.com/science/article/pii/S0926860X19300675?via%3Dihub" target="_blank" >https://www.sciencedirect.com/science/article/pii/S0926860X19300675?via%3Dihub</a>

DOI - Digital Object Identifier

<a href="http://dx.doi.org/10.1016/j.apcata.2019.02.024" target="_blank" >10.1016/j.apcata.2019.02.024</a>

Jazyk výsledku

angličtina

Název v původním jazyce

H/D reactivity and acidity of Bronsted acid sites of MWW zeolites: Comparison with MFI zeolite

Popis výsledku v původním jazyce

Acid site strength in MWW and MFI zeolites was investigated by isotopic exchange reaction between deuterated hydroxyl groups of zeolites and ethane molecules. The course of the reaction was monitored by FT-IR spectroscopy through time changes of integral intensities of the Si(OD)Al Bronsted acid sites represented by absorption bands at 2644, 2655, and 2657 cm(-1) for MFI, MWW and MCM-36 zeolite, respectively. The rate of the reaction was described by pseudo first order kinetics and acid site strength was compared using rate constants characteristic of individual zeolites at constant temperature. The exchange reaction is significantly faster over MFI zeolite compared with MWW zeolites, suggesting a higher acid strength of Bronsted sites in MN zeolite than in MWW. In our previous study (Arean et al. Phys. Chem. Chem. Phys. 16 (2014) 10,129), we found notable discrepancy in the relation between OH group frequency shift induced by adsorption of weak base molecules like CO and N-2 and the change of adsorption enthalpy of these probe molecules for MWW zeolites, which calls into question the use of frequency shifts as a measure of acidity. Our reported results based on isotopic exchange reaction rate measurement correlate with the change of the probe molecules adsorption enthalpy involved in hydrogen bonding. Therefore, we believe that enthalpy change or H/D exchange activity measurement is more reliable method for assessment of acid strength than O-H frequency shift probed by a weak base adsorbed at a low temperature.

Název v anglickém jazyce

H/D reactivity and acidity of Bronsted acid sites of MWW zeolites: Comparison with MFI zeolite

Popis výsledku anglicky

Acid site strength in MWW and MFI zeolites was investigated by isotopic exchange reaction between deuterated hydroxyl groups of zeolites and ethane molecules. The course of the reaction was monitored by FT-IR spectroscopy through time changes of integral intensities of the Si(OD)Al Bronsted acid sites represented by absorption bands at 2644, 2655, and 2657 cm(-1) for MFI, MWW and MCM-36 zeolite, respectively. The rate of the reaction was described by pseudo first order kinetics and acid site strength was compared using rate constants characteristic of individual zeolites at constant temperature. The exchange reaction is significantly faster over MFI zeolite compared with MWW zeolites, suggesting a higher acid strength of Bronsted sites in MN zeolite than in MWW. In our previous study (Arean et al. Phys. Chem. Chem. Phys. 16 (2014) 10,129), we found notable discrepancy in the relation between OH group frequency shift induced by adsorption of weak base molecules like CO and N-2 and the change of adsorption enthalpy of these probe molecules for MWW zeolites, which calls into question the use of frequency shifts as a measure of acidity. Our reported results based on isotopic exchange reaction rate measurement correlate with the change of the probe molecules adsorption enthalpy involved in hydrogen bonding. Therefore, we believe that enthalpy change or H/D exchange activity measurement is more reliable method for assessment of acid strength than O-H frequency shift probed by a weak base adsorbed at a low temperature.

Druh

J_imp - Článek v periodiku v databázi Web of Science

CEP obor

—

OECD FORD obor

10403 - Physical chemistry

Projekt

<a href="/cs/project/GBP106%2F12%2FG015" target="_blank" >GBP106/12/G015: Vývoj nových nanoporézních adsorbentů a katalyzátorů</a><br>

Návaznosti

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

Rok uplatnění

2019

Kód důvěrnosti údajů

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

Název periodika

Applied catalysis A: General

ISSN

0926-860X

e-ISSN

—

Svazek periodika

575

Číslo periodika v rámci svazku

April

Stát vydavatele periodika

NL - Nizozemsko

Počet stran výsledku

7

Strana od-do

180-186

Kód UT WoS článku

000462801700020

EID výsledku v databázi Scopus

2-s2.0-85062030879