Changes in hydration properties of silica gel in a process of its carbonization by pyrolysis of acetylacetone Zn (Ti) acetylacetonates

Changes in hydration properties of different compounds in a process of formation of a complex adsorbent comprising carbon and TiO2 or Zn2SiO4 on its surface were studied by H-1 NMR spectroscopy under conditions of a liquid phase freezing. Adsorbents were synthesized on the basis of a mesoporous silica gel, the surface of which was covered with a carbon layer formed in a process of a high temperature pyrolysis of acetylacetone, Titanium oxide and zinc silicate on the surface of a parent silica gel were formed by a pyrolysis of acetylacetonates of the corresponding metals. It has been revealed that the main types of surface-active sites for the adsorbed water molecules on the carbosil surface are the systems of condensed benzene nuclei of a carbon component of the surface and hydroxyl groups of silica surface. Zn2SiO4 and TiO2 have been formed in a process of pyrolysis of the corresponding metal acetylacetonates. Water bound with the oxide component of the carbosil surface exceeds 80% of the total amount of the adsorbed water. The carbon component of the surface is localized mainly in the narrowest pores. A minimum value in the free surface energy was recorded for the carbosil sample. (C) 1998 Academic Press.