Calorimetric study of amine adsorption on α- and γ-titanium phosphate

Using a microcalorimetric technique, we have determined the differential heat of adsorption of ethyl-and n-butylamine over alpha- and gamma-titanium phosphate phases. The recorded data were compared with those obtained by using N-2/77 K adsorption-desorption isotherms, X-ray diffraction peak broadening studies, and scanning electron microscopy. At low coverage, the measured heat of adsorption decreases with increasing coverage, which means the solids have superficial heterogeneity. The gamma-phase external surface is more energetic than the a-one. The average heats of adsorption in the interlamellar region of the alpha-titanium phosphate at 298 K (ethylamine, 95 kJ mol(-1); n-butylamine, 110 kJ mol(-1)) are in good agreement with gas-phase proton affinities data.