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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。
Attapulgite with the composition of [MgAlFe] 5Si8O20 (OH) 2 (OH) 2 (OH2) 44H2O has been used as catalyst or catalyst support in various catalytic reactions. The surface acidity and 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 spectroscopy and test reaction of isopropanol dehydration. The results indicated that the attapulgite dis-played the acidity with initial differential NH, adsorption heat of 130 kJ / mol and saturated NHS coversge 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-t r summary revealed that the attapulgite had both Brdnsted and Lewis acid sites- Moreover, the Lewis acid sites (1 619 cm -1) were stronger than 90 kJ / mol characteric of the NH, any basicity compared to t-γ-Al2O3.