CALORIMETRIC STUDY OF AMINE ADSORPTION ON ALPHA-TITANIUM-PHOSPHATE AND GAMMA-TITANIUM-PHOSPHATE

Using a microcalorimetric technique, we have determined the differenti al 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 diff raction peak broadening studies, and scanning electron microscopy. At low coverage, the measured heat of adsorption decreases with increasin g coverage, which means the solids have superficial heterogeneity. The gamma-phase external surface is more energetic than the a-one. The av erage heats of adsorption in the interlamellar region of the alpha-tit anium phosphate at 298 K (ethylamine, 95 kJ mol(-1); n-butylamine, 110 kJ mol(-1)) are in good agreement with gas-phase proton affinities da ta.