New insights in the formation of silanol defects in silicalite-1 by water intrusion under high pressure.
The "water-silicalite-1" system is known to act as a molecular spring. The successive intrusion-extrusion cycles of liquid water in small crystallites (6 × 3 × 0.5 μm(3)) of hydrophobic silicalite-1 were studied by volumetric and calorimetric techniques. The experiments displayed a decrease of the intrusion pressure between the first intrusion-extrusion cycle and the consecutive ones, whereas the extrusion pressures remained unchanged. However, neither XRD studies nor SEM observations revealed any structural and morphological modifications of silicalite-1 at the long-range order. Such a shift in the value of the intrusion pressure after the first water intrusion-extrusion cycle is attributed to the creation of silanol groups during the first water intrusion. Detailed FTIR and solid-state NMR spectroscopic characterizations provided a molecular evidence of chemical modification of zeolite framework with the formation of local silanol defects created by the breaking of siloxane bonds.
Karbowiak
Thomas
T
Laboratoire Interdisciplinaire Carnot de Bourgogne (ICB), UMR 5209 CNRS, Université de Bourgogne, 9 Av. A. Savary, BP 47870, F-21078 Dijon, France.
Saada
Mohamed-Ali
MA
Rigolet
Séverinne
S
Ballandras
Anthony
A
Weber
Guy
G
Bezverkhyy
Igor
I
Soulard
Michel
M
Patarin
Joël
J
Bellat
Jean-Pierre
JP
D002151:Calorimetry; D003460:Crystallization; D011312:Pressure; D012821:Silanes / Q000737:chemistry*; D017640:Silicates / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D014867:Water / Q000737:chemistry*; D014961:X-Ray Diffraction; D017641:Zeolites / Q000737:chemistry
D012821:Silanes; D017640:Silicates; D014867:Water; C082343:silanol; D017641:Zeolites