Heats of adsorption of N-hexane by thermal gravimetry with differential scanning calorimetry (TG-DSC): A tool for textural characterization of pillared clays

Microporous materials, (materials with pore sizes with widths <2 nm) were p repared by pillaring of smectites obtained from different soil deposits. Th e materials were prepared by intercalation with oligomeric cations of alumi num, which were transformed to aluminum-oxide pillars by calcination. The a dsorption of n-hexane in the pillared clays was studied by the determinatio n of heats of adsorption. Heats of adsorption were measured using either a static microcalorimeter or differential scanning calorimetry coupled with t hermogravimetry (TG-DSC). In this latter case, two different procedures wer e used that differ on the introduction of the (n-hexane) molecules that are to be adsorbed. The results obtained by the (standard) static microcalorim eter method and the TG-DSC method were compared. This comparison showed the heats of adsorption obtained by TG-DSC are differential heats of adsorptio n, and it showed the range of adsorption. Characterizing the texture of pil lared clays, especially microporosity, is important for monitoring the inte rcalation process and for determining potential applications of these mater ials. Correlations between the obtained heats of adsorption and the dimensi ons of micropores suggest that TG-DSC is a semi-quantitative method for cha racterizing micropores in aluminum-pillared clays.