Abstract
The process of adsorption of five aliphatic alcohols (C1–C5) on α-Al2O3 in the temperature range 25–200°C has been studied by means of a Calvet microcalorimeter (moderately high temperature) equipped with a volumetric ramp. The calorimetric and volumetric isotherms indicate that the integral heats released and the amounts of alcohols adsorbed decreased as the experimental temperature increased. All the volumetric isotherms follow the Langmuir isotherm trend, i.e. type I isotherms. The differential heats of the five alcohols on α-alumina were very high (>250 kJ/mol) at very low coverages at all temperatures and decreased rapidly towards the heat of vaporization of the alcohols at higher coverages. The trends in the differential heats of adsorption as a function of the number of μmol of MeOH, EtOH, and 1-PrOH adsorbed appear to be different from those for 1-BuOH and 1-PeOH (1-pentanol) at the different temperatures studied. Increasing the adsorption temperature made the trends in the differential heats more pronounced, with the alumina surface requiring smaller amounts of adsorbed alcohol to effect its saturation.
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