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1524781 
Journal Article 
Influence of the nitric acid treatment on Al removal, framework composition and acidity of BEA zeolite investigated by XRD, FTIR and NMR 
Baran, R; Millot, Y; Onfroy, T; Krafft, JM; Dzwigaj, S 
2012 
1 
Microporous and Mesoporous Materials
ISSN: 1387-1811 
163 
122-130 
WOS:000309625800015 
Two different procedures were used to prepare dealuminated
BEA zeolite. The first procedure realized in two steps consisted of first calcination of original
tetraethylammonium (TEA) BEA(17) zeolite in air at 823 K for 15 h to remove organic template and
then treatment of as resulted organic-free HAIBEA(17) zeolite with concentrated nitric acid
solution for different times to remove part or all Al atoms. Two periods was distinguished in the
removal of Al atoms from HAIBEA(17) framework during the first procedure. During initial period
(up to 0.08 h), the dealumination was very fast and 94% of Al was removed. This period
corresponded to the easy removal of extra framework octahedral and framework tetrahedral aluminum
from T3-T9 sites. In the second period (from 0.08 to 4 h), the dealumination was much slower. It
corresponded to a much more difficult removal of framework tetrahedral aluminum from T1 and T2
sites. The second procedure realized in one step consisted of direct treatment of original TEABEA
zeolite with concentrated nitric acid solution to remove simultaneously organic template and Al
atoms. To obtain partly or totally dealuminated BEA zeolite the treatment time was 0.08 and 4 h
respectively. The influence of the nitric acid treatment on Al removal, framework composition and
acidity of BEA zeolite were investigated by XRD, FTIR and NMR. 20 Al-27 3Q MAS NMR allowed
distinguishing two kinds of framework tetrahedral Al atoms (Al-Td(2a) and Al-Td(2b)) in BEA
zeolite which relative amounts depended on the Si/Al ratio. The Bronsted and Lewis acidic centers
were evidenced in dealuminated BEA zeolites by FTIR spectra of adsorbed pyridine and CO use as
probe molecules. Their relative amounts depended on the degree of dealumination and procedure
used for removal Al atoms. (C) 2012 Elsevier Inc. All rights reserved. 
Dealumination; BEA zeolite; CO; FTIR; NMR