TY - JOUR
T1 - Entrapping molecules in zeolites nanocavities
T2 - A thermodynamic and ab-initio study
AU - Bolis, V.
AU - Barbaglia, A.
AU - Broyer, M.
AU - Busco, C.
AU - Civalleri, B.
AU - Ugliengo, P.
PY - 2004/2
Y1 - 2004/2
N2 - Adsorption enthalpies of Ar, N2, CO, H2O, CH 3CN and NH3 on H-BEA and H-MFI zeolites and on Silicalite, have been measured calorimetrically at 303K in order to assess the energetic features of dispersive forces interactions (confinement effects), H-bonding interactions with surface silanols and specific interactions with Lewis and Brønsted acidic sites. The adsorption of the molecular probes with model clusters mimicking surface silanols, Lewis and Brønsted sites has been simulated at ab-initio level. The combined use of the two different approaches allowed to discriminate among the different processes contributing to the measured (-ΔadsH). Whereas CO and N2 single out contributions from Lewis and Brønsted acidic sites, Ar is only sensitive to confinement effects. For H2O, CH3CN and NH3 the adsorption on Brønsted sites is competitive with the adsorption on Lewis sites. The energy of interaction of H2O with all considered zeolites is surprisingly higher than expected on the basis of -Δ adsH vs PA correlation.
AB - Adsorption enthalpies of Ar, N2, CO, H2O, CH 3CN and NH3 on H-BEA and H-MFI zeolites and on Silicalite, have been measured calorimetrically at 303K in order to assess the energetic features of dispersive forces interactions (confinement effects), H-bonding interactions with surface silanols and specific interactions with Lewis and Brønsted acidic sites. The adsorption of the molecular probes with model clusters mimicking surface silanols, Lewis and Brønsted sites has been simulated at ab-initio level. The combined use of the two different approaches allowed to discriminate among the different processes contributing to the measured (-ΔadsH). Whereas CO and N2 single out contributions from Lewis and Brønsted acidic sites, Ar is only sensitive to confinement effects. For H2O, CH3CN and NH3 the adsorption on Brønsted sites is competitive with the adsorption on Lewis sites. The energy of interaction of H2O with all considered zeolites is surprisingly higher than expected on the basis of -Δ adsH vs PA correlation.
KW - Adsorption
KW - Brønsted acidity
KW - Lewis acidity
KW - Microcalorimetry
KW - Zeolites
KW - ab initio calculations
UR - http://www.scopus.com/inward/record.url?scp=0842345496&partnerID=8YFLogxK
U2 - 10.1023/B:ORIG.0000009829.11244.d1
DO - 10.1023/B:ORIG.0000009829.11244.d1
M3 - Article
SN - 0169-6149
VL - 34
SP - 69
EP - 77
JO - Origins of Life and Evolution of Biospheres
JF - Origins of Life and Evolution of Biospheres
IS - 1-2
ER -