Heats of Adsorption of Aliphatic Alcohols on α-Al2O3 at 25–200°C. I. Variations with Experimental Temperature

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.

[1]  M. Bassoli,et al.  Heat of chemisorption of 1-propanol on α-Al2O3 at 25–200°C , 1994 .

[2]  P. Rossi,et al.  Variations in the chemisorption of methanoi on α-Al2O3 in the range 200–300°C , 1993 .

[3]  P. Rossi.  Adsorption Heat-Flow Microcalorimetry Applied to Coal Surface Properties , 1992 .

[4]  G. Busca,et al.  Adsorption of Methanol on Alumina in the 298–473 K Temperature Range: A Microcalorimetric and FT–IR Spectroscopic Study , 1986 .

[5]  G. Busca,et al.  Microcalorimetric and Fourier transform infrared spectroscopic studies of methanol adsorption on alumina , 1985 .

[6]  T. Morimoto,et al.  Adsorption of alcohols on zinc oxide surfaces , 1980 .

[7]  T. Morimoto,et al.  Differential heat of chemisorption. 4. Chemisorption of methanol and 1-propanol on zinc oxide , 1980 .

[8]  H. Knoezinger,et al.  Adsorption of alcohols on alumina. 1. Gravimetric and infrared spectroscopic investigation , 1978 .

[9]  G. Gatta,et al.  Energies of different surface rehydration processes on “eta”, “theta” and “alpha” aluminas , 1977 .

[10]  H. Knözinger,et al.  H-bonding on solid oxide surfaces. Infra-red spectroscopic study of the adsorption of alcohols on silica and alumina , 1973 .

[11]  V. F. Baston,et al.  The gas phase autophobicity of alcohols adsorbed on alumina , 1966 .

[12]  Y. Yao.  Adsorption of Polar Molecules on Metal Oxide Single Crystals , 1965 .

[13]  W. Wade,et al.  Heats of Immersion. VIII. Differential Heats of Adsorption as a Function of Particle Size for the Alumina-Water System , 1965 .