Attapulgite with the composition of [MgAlFe]5Si8O20(OH)2(OH)2(OH2)44H2O has beenwidely used as catalyst or catalyst support in various catalytic reactions. The surface acidityand basicity of attapulgite should play an important role, in particular, in the acid/base cat-alyzed reactions. In this paper, a Tian-Calvet type microcalorimeter was used to measurequantitatively the number and strength of acid/base sites on the surface of attapulgite sam-ple. The acid/base properties of the sample were also investigated with infrared spectroscopyand test reaction of isopropanol dehydration.The results indicated that the attapulgite dis-played the acidity with initial differential NH, adsorption heat of 130kJ/mol and saturatedNHs coverge of 1. 5 pmol/m2. The strength distributions of surface acid sites on attapulgiteand the calorometric results suggested that the attapulgite possessed only a few(<0.1 μmol/m2) very weak base sites with CO2 adsorption heat lower than 5 kJ/mol. The infrared spec-troscopy revealed that the attapulgite had both Brdnsted and Lewis acid sites- Moreover, theLewis acid sites(1 619 cm-1 ) were stronger than 90 kJ/mol characteric of the NH, adsorptionheat. In summary, the attapulgite was a weak solid acid without any basicity compared tothe γ-Al2O3。
