TY - JOUR
T1 - Shedding light on the atomic-scale structure of amorphous silica-alumina and its Brønsted acid sites
AU - Perras, Frédéric A.
AU - Wang, Zichun
AU - Kobayashi, Takeshi
AU - Baiker, Alfons
AU - Huang, Jun
AU - Pruski, Marek
N1 - Version archived for private and non-commercial use with the permission of the author/s and according to publisher conditions. For further rights please contact the publisher.
PY - 2019/9/21
Y1 - 2019/9/21
N2 - In spite of the widespread applications of amorphous silica–aluminas
(ASAs) in many important industrial chemical processes, their
high-resolution structures have remained largely elusive. Specifically,
the lack of long-range ordering in ASA precludes the use of diffraction
methods while NMR spectroscopy has been limited by low sensitivity.
Here, we use conventional as well as DNP-enhanced 29Si–29Si, 27Al–27Al, and 29Si–27Al
solid-state NMR experiments to shed light on the ordering of atoms in
ASAs prepared by flame-spray-pyrolysis. These experiments, in
conjunction with a novel Monte Carlo-based approach to simulating
RESPDOR dephasing curves, revealed that ASA materials obey Loewenstein's
rule of aluminum avoidance. 3D 17O{1H} and 2D 17O{1H,27Al}
experiments were developed to measure site-specific O–H and HO–Al
distances, and show that the Brønsted acid sites originate predominantly
from the pseudo-bridging silanol groups.
AB - In spite of the widespread applications of amorphous silica–aluminas
(ASAs) in many important industrial chemical processes, their
high-resolution structures have remained largely elusive. Specifically,
the lack of long-range ordering in ASA precludes the use of diffraction
methods while NMR spectroscopy has been limited by low sensitivity.
Here, we use conventional as well as DNP-enhanced 29Si–29Si, 27Al–27Al, and 29Si–27Al
solid-state NMR experiments to shed light on the ordering of atoms in
ASAs prepared by flame-spray-pyrolysis. These experiments, in
conjunction with a novel Monte Carlo-based approach to simulating
RESPDOR dephasing curves, revealed that ASA materials obey Loewenstein's
rule of aluminum avoidance. 3D 17O{1H} and 2D 17O{1H,27Al}
experiments were developed to measure site-specific O–H and HO–Al
distances, and show that the Brønsted acid sites originate predominantly
from the pseudo-bridging silanol groups.
UR - http://www.scopus.com/inward/record.url?scp=85072058092&partnerID=8YFLogxK
UR - http://purl.org/au-research/grants/arc/DP150103842
UR - http://purl.org/au-research/grants/arc/DP180104010
U2 - 10.1039/c9cp04099d
DO - 10.1039/c9cp04099d
M3 - Article
C2 - 31463497
AN - SCOPUS:85072058092
SN - 1463-9076
VL - 21
SP - 19529
EP - 19537
JO - Physical Chemistry Chemical Physics
JF - Physical Chemistry Chemical Physics
IS - 35
ER -