A study by adsorption calorimetry, effect of resorcinol/catalyst at different ratios using polar and non-polar molecules in the synthesis of carbon aerogels.

Abstract

The heterogeneity and hydrophilicity of a series of aerogels were studied using adsorption calorimetry with molecules of different polarity. Four samples of carbon aerogel were synthesized with different resorcinol/catalytic (R/C) relations: 100, 200, 800 and 1500. The isotherms of N2 at -196 ◦C were determined and from these were calculated the textural parameters using the Dubinin–Astakhov (DA), Barret–Joyner–Halenda (BJH), Non-Local Density Functional Theory (NLDFT) and Quenched Solid Density Functional Theory (QSDFT) models. The adsorption isotherms of polar and non-polar molecules: benzene, hexane, methane, methanol and methyl-ethyl-ketone (MEK) were determined, as well as the differential adsorption enthalpies of these on the aerogel. The results show that the aerogels samples at low R/C have a fundamental development of micropores and at high R/C values present an additional development of mesoporosity. Adsorption isotherms of polar and non-polar molecules were adjusted to the Langmuir–Sips model and In-homogenous DA equation, respectively. Adsorption calorimetry shows that the carbon aerogels at these relations present heterogeneous surfaces that are essentially hydrophilic.

Keywords

• Aerogels
• isotherms
• adsorption calorimetry
• Langmuir–Sips
• In-homogeneous isotherm