jp6b09012_si_002.zip (4.22 MB)
Inelastic Neutron Scattering Study on the Location of Brønsted Acid Sites in High Silica LTA Zeolite
dataset
posted on 2016-10-17, 00:00 authored by Tetiana Lemishko, Susana Valencia, Fernando Rey, Mónica Jiménez-Ruiz, German SastreThe
presence of Brønsted acid sites (SiOHAl) is crucial in
many of the applications of zeolites in petroleum refining and related
industries. This acidity relies on the number and location of acid
sites, but the latter is difficult to know accurately in spite of
a large number of experimental techniques available. Zeolites usually
contain many types of acid sites depending on the crystallographic
different O-sites and their chemical environment. In the present work
we show how inelastic neutron scattering (INS) can be employed for
an accurate determination of the location of Brønsted acid sites
in zeolites. This is achieved using a sample of LTA zeolite with few
defects of connectivity, few (O1H, O2H, O3H) crystallographically
different oxygens, and high Si/Al ratio. The narrow and intense peaks
corresponding to SiOH bending modes ca. 1100 cm–1 have been shown, using periodic DFT calculations, to strongly depend
on the type of oxygen to which the proton is bonded. A comparison
between calculations and INS experiments shows that a large majority
of the protons in the sample are of the type O2H, which vibrate close
to the small cavity of LTA.