Understanding physico-chemical properties of saponite synthetic clays.

Beitrag in einer Fachzeitschrift
(Originalarbeit)


Details zur Publikation

Autorinnen und Autoren: Thommes M
Zeitschrift: Microporous and Mesoporous Materials
Verlag: Elsevier B.V.
Jahr der Veröffentlichung: 2007
Band: 107
Heftnummer: 1-2
Seitenbereich: 90-101-101
ISSN: 1387-1811


Abstract

Synthetic saponite-like materials were prepd. by traditional hydrothermal crystn. at 513 K of 1 SiO2; 0.835MgO; 0.056Al2O3; 0.056Na2O; nH2O gel with variable amt. of H2O. The obtained layered materials were submitted to a systematic study of textural properties, morphol., thermal behavior of the produced materials by combining different exptl. techniques (XRD, SEM, TEM, N2 physisorption, Solid State MASNMR). For the 1st time, a fine characterization of the surface acidity of the produced saponites performed by FTIR spectroscopy of CO probe mol. (complemented with NH3) was given. The diln. (H2O/Si ratio) of the synthesis gel played a significant role in detg. the physicochem. properties of the final products, the higher the gel diln., the smaller the platelets detd. by TEM anal. Also, sp. surface area of saponite samples increased with decreasing the lamellae dimensions. NLDFT and BJH approaches applied to nitrogen adsorption and desorption branches were used to define the porosity of the samples. Both micro- and mesopores were found, the latter being much more abundant on the saponite prepd. at the highest gel diln. (SAP50, H2O/Si = 50). A combined XRD and IR study performed at variable temp. showed that the materials were stable up to 773 K and that thermal stability is not dependent on the diln. of the synthesis gel. 27Al-MASNMR indicated that SAP50 sample contained a higher concn. of octahedral Al species than SAP20 (H2O/Si = 20). These species were mainly located in the octahedral sheets as a result of isomorphous substitution of AlIII with MgII ions, and this consequently reduced the cation exchange capacity (CEC) of the material. FTIR of CO adsorption was used to monitor, beside surface protons, interlayer cations. Both magnesium and sodium ions were found in the interlayer space, and their distribution varied from one sample to another. Magnesium, for instance, was more abundant in SAP50 than SAP20. Protons located on bridged hydroxyls [Si-O(H)-Al] of the tetrahedral silica sheets displayed acidity similar to the most acid H-ZSM-5 zeolites. [on SciFinder(R)]


FAU-Autorinnen und Autoren / FAU-Herausgeberinnen und Herausgeber

Thommes, Matthias Prof. Dr.
Lehrstuhl für Thermische Verfahrenstechnik

Zuletzt aktualisiert 2019-27-02 um 20:54