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Direct Measurement of Zeolite Brønsted Acidity by FTIR Spectroscopy : Solid-State 1H MAS NMR Approach for Reliable Determination of the Integrated Molar Absorption Coefficients. / Gabrienko, Anton A.; Danilova, Irina G.; Arzumanov, Sergei S. и др.
в: Journal of Physical Chemistry C, Том 122, № 44, 08.11.2018, стр. 25386-25395.Результаты исследований: Научные публикации в периодических изданиях › статья › Рецензирование
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TY - JOUR
T1 - Direct Measurement of Zeolite Brønsted Acidity by FTIR Spectroscopy
T2 - Solid-State 1H MAS NMR Approach for Reliable Determination of the Integrated Molar Absorption Coefficients
AU - Gabrienko, Anton A.
AU - Danilova, Irina G.
AU - Arzumanov, Sergei S.
AU - Pirutko, Larisa V.
AU - Freude, Dieter
AU - Stepanov, Alexander G.
N1 - Publisher Copyright: © 2018 American Chemical Society.
PY - 2018/11/8
Y1 - 2018/11/8
N2 - Fourier transform infrared (FTIR) spectroscopy is broadly applied nowadays for probing the concentration and strength of acid sites in zeolite catalysts. Accuracy of direct determination of the quantity of different hydroxyl groups by FTIR method suffers from uncertainty of the integrated molar absorption coefficients, ϵ. The values of ϵ reported by different authors might differ by an order of magnitude. This paper provides an approach for reliable determination of the integrated molar absorption coefficients by combining 1H magic-angle spinning (MAS) NMR and FTIR spectroscopy techniques. The concentration of Brønsted acid sites for the series of H-ZSM-5 and H-ZSM-23 zeolite samples with different Si/Al ratio has been reliably established with 1H MAS NMR using methane and benzene as internal standards adsorbed on the studied samples. The data on the obtained concentration were further used to analyze same zeolite samples with FTIR spectroscopy and derive the information on the values of the integrated molar absorption coefficients. The coefficients ϵ have been reliably determined to be 3.06 ± 0.04 and 1.50 ± 0.06 cm μmol-1 for the IR bands at 3605-3615 and 3740-3747 cm-1, respectively. The ϵ values are similar for both H-ZSM-5 and H-ZSM-23 zeolites. It is also established that the ϵ values are constant with respect to the concentration of hydroxyl groups for H-ZSM-5 and H-ZSM-23 zeolites. The determined coefficients ϵ can be further used for reliable assessment of zeolite Brønsted acidity with the aid of the widely available and relatively simple methodology of FTIR spectroscopy.
AB - Fourier transform infrared (FTIR) spectroscopy is broadly applied nowadays for probing the concentration and strength of acid sites in zeolite catalysts. Accuracy of direct determination of the quantity of different hydroxyl groups by FTIR method suffers from uncertainty of the integrated molar absorption coefficients, ϵ. The values of ϵ reported by different authors might differ by an order of magnitude. This paper provides an approach for reliable determination of the integrated molar absorption coefficients by combining 1H magic-angle spinning (MAS) NMR and FTIR spectroscopy techniques. The concentration of Brønsted acid sites for the series of H-ZSM-5 and H-ZSM-23 zeolite samples with different Si/Al ratio has been reliably established with 1H MAS NMR using methane and benzene as internal standards adsorbed on the studied samples. The data on the obtained concentration were further used to analyze same zeolite samples with FTIR spectroscopy and derive the information on the values of the integrated molar absorption coefficients. The coefficients ϵ have been reliably determined to be 3.06 ± 0.04 and 1.50 ± 0.06 cm μmol-1 for the IR bands at 3605-3615 and 3740-3747 cm-1, respectively. The ϵ values are similar for both H-ZSM-5 and H-ZSM-23 zeolites. It is also established that the ϵ values are constant with respect to the concentration of hydroxyl groups for H-ZSM-5 and H-ZSM-23 zeolites. The determined coefficients ϵ can be further used for reliable assessment of zeolite Brønsted acidity with the aid of the widely available and relatively simple methodology of FTIR spectroscopy.
KW - SOLID-STATE NMR
KW - SURFACE HYDROXYL-GROUPS
KW - QUANTITATIVE INFRARED-SPECTROSCOPY
KW - NUCLEAR-MAGNETIC-RESONANCE
KW - HETEROGENEOUS CATALYSIS
KW - IR SPECTROSCOPY
KW - METHANE ACTIVATION
KW - HYDROGEN-ZEOLITES
KW - SILICA-ALUMINA
KW - Y-ZEOLITES
KW - INFRARED-SPECTROSCOPY
KW - H-ZSM-5
KW - Y ZEOLITE
KW - SITES
KW - CATALYSTS
UR - http://www.scopus.com/inward/record.url?scp=85056421612&partnerID=8YFLogxK
U2 - 10.1021/acs.jpcc.8b07429
DO - 10.1021/acs.jpcc.8b07429
M3 - Article
AN - SCOPUS:85056421612
VL - 122
SP - 25386
EP - 25395
JO - Journal of Physical Chemistry C
JF - Journal of Physical Chemistry C
SN - 1932-7447
IS - 44
ER -
ID: 17410955