Impact of thermal and hydrothermal treatments on structural characteristics of silica gel Si-40 and carbon/silica gel adsorbents

Structural and adsorptive characteristics of silica gel Si-40 initial, modified by grafted carbon (carbosil), and differently treated (hydrothermally treated at 150 °C (or 200 °C) before and after heating at 500 °C and heating at 500 °C after HTT) were analysed using adsorption–desorption of nitrogen at 77.4 K, 1H NMR and TEM methods. Carbonisation of acenaphthene on Si-40 surface is accompanied by significant changes in the pore topology. Hydrothermal treatment of initial silica gel and carbosils results in strong modification of pore structure, which reflects in alteration in the shape of nitrogen adsorption–desorption isotherms, the 1H NMR spectra of adsorbed water, and an increase in non-uniformity of the adsorbents. Heating of silica and carbon/silica samples at 500 °C in air to remove carbon deposits reduces this non-uniformity.