Post-synthetic activation of silanol covering in the mesostructured silicate materials MCM-41 and SBA-15

Описание

Тип публикации: статья из журнала

Год издания: 2010

Идентификатор DOI: 10.1016/j.micromeso.2010.04.024

Ключевые слова: MCM-41, SBA-15, Silanol number, Thermogravimetry, Destruction rates, Inner surfaces, IR-spectroscopy, Limit values, Material surface, Mesoporous silicates, Mesostructured, Mesostructured silicate material, Nitrogen adsorption, OH-groups, Percolation theory, Post-synthetic treatments, Silanol groups, Silanols, Calcination, Gas adsorption, Hydrofluoric acid, Materials, Silicates, Silicon, Thermoanalysis, Thermogravimetric analysis, X ray diffraction, Surfaces

Аннотация: The influence of different types of post-synthetic treatment (exposure at calcination, at boiling treatment in neutral, acidic and alkaline aqueous solutions, treatment in hydrofluoric acid) on the state of the silanol surface of the mesostructured mesoporous silicate materials MCM-41 and SBA-15 has been studied. The material alterПоказать полностьюation has been monitored by X-ray diffraction, IR-spectroscopy, thermal analysis and nitrogen adsorption. It has been shown that post-synthetic treatment changes the concentration of silanol groups on the material surface. The limit value has been established by experiment: about 3-4 OH/nm(2) for MCM-41 and 5-6 OH/nm(2) for SBA-15, with its excess resulting in the material destruction. The distribution of the re-formed Si-OH groups over the surface is of irregular focal nature. In spite of the destruction, the specific characteristics of the material (inner surface, volume, and lattice parameter) remain the same. The treatment type and medium content influence the material destruction rate, but not the limit density of the silanol covering. Based on the molecular model of MCM-41 and percolation theory an interpretation has been proposed due to the mechanism of fragmentary material decay. Fragments of the surface with the concentration of the OH-groups exceeding the limit eliminate from material because the concentration of OH-groups is correlated with concentrations of the broken silaxane bonds (Si-O-Si), which responsible for the surface connectivity. (C) 2010 Elsevier Inc. All rights reserved.

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Издание

Журнал: MICROPOROUS AND MESOPOROUS MATERIALS

Выпуск журнала: Vol. 133, Is. 1-3

Номера страниц: 124-133

ISSN журнала: 13871811

Место издания: AMSTERDAM

Издатель: ELSEVIER SCIENCE BV

Авторы

  • Kozlova S.A. (Institute of Chemistry and Chemical Technology SB RAS)
  • Kirik S.D. (Siberian Federal University)

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