TY - JOUR
T1 - Effect of the Si/Zr molar ratio on the synthesis of Zr-based mesoporous molecular sieves
AU - Salas, P.
AU - Wang, J. A.
AU - Armendariz, H.
AU - Angeles-Chavez, C.
AU - Chen, L. F.
PY - 2009/3/15
Y1 - 2009/3/15
N2 - Highly ordered Zr-based mesoporous molecular sieves were synthesized via a surfactant-templated method and the effect of the Si/Zr molar ratio on the crystalline structure, textural properties and surface acidity were studied by XRD, FTIR, TEM and 29Si MAS-NMR techniques. FTIR spectra show that the intensity of the band around 890 cm-1 which corresponds to the vibration of Si-O-Zr bond was increased with increasing of the zirconium content, therefore, this band may be used as an indicator of the degree of the zirconium incorporation into the Si-framework. When the zirconium content increased in the materials, the Q3/Q4 value obtained from 29Si MAS-NMR was linearly increased, whereas, the intensity the XRD peaks was gradually reduced; as a result, the pore wall thickness of the resultant materials was gradually increased, the surface area and the structural regularity were diminished. In order to obtain Zr-MCM-41 with highly ordered mesostructure and large surface area, proper Si/Zr molar ratio is a key factor, e.g., Si/Zr should be no less than 10. It was also found that the Brønsted acid sites which resulted from charge unbalance or local structure deformation due to the Zr4+ incorporation into the vicinity of the hydroxyls carrying silicon were created on the surface of the Zr-MCM-41 solids; strong Brønsted acidity could be formed on the solid with high zirconium content.
AB - Highly ordered Zr-based mesoporous molecular sieves were synthesized via a surfactant-templated method and the effect of the Si/Zr molar ratio on the crystalline structure, textural properties and surface acidity were studied by XRD, FTIR, TEM and 29Si MAS-NMR techniques. FTIR spectra show that the intensity of the band around 890 cm-1 which corresponds to the vibration of Si-O-Zr bond was increased with increasing of the zirconium content, therefore, this band may be used as an indicator of the degree of the zirconium incorporation into the Si-framework. When the zirconium content increased in the materials, the Q3/Q4 value obtained from 29Si MAS-NMR was linearly increased, whereas, the intensity the XRD peaks was gradually reduced; as a result, the pore wall thickness of the resultant materials was gradually increased, the surface area and the structural regularity were diminished. In order to obtain Zr-MCM-41 with highly ordered mesostructure and large surface area, proper Si/Zr molar ratio is a key factor, e.g., Si/Zr should be no less than 10. It was also found that the Brønsted acid sites which resulted from charge unbalance or local structure deformation due to the Zr4+ incorporation into the vicinity of the hydroxyls carrying silicon were created on the surface of the Zr-MCM-41 solids; strong Brønsted acidity could be formed on the solid with high zirconium content.
KW - Acidity
KW - FTIR
KW - Mesoporous molecular sieves
KW - Zirconium
KW - Zr-MCM-41
UR - http://www.scopus.com/inward/record.url?scp=58149462104&partnerID=8YFLogxK
U2 - 10.1016/j.matchemphys.2008.08.086
DO - 10.1016/j.matchemphys.2008.08.086
M3 - Artículo
SN - 0254-0584
VL - 114
SP - 139
EP - 144
JO - Materials Chemistry and Physics
JF - Materials Chemistry and Physics
IS - 1
ER -