凹凸棒粘土表面酸碱性质的研究  

Studies of Surface Acidity and Basicity of the Attapulgite

作　　者：王庆根[1] 屠迈[1] 王纬东 沈俭一[1] 

机构地区：[1]南京大学化学系,南京210093

出　　处：《高等学校化学学报》1997年第4期625-627,共3页Chemical Journal of Chinese Universities

基　　金：国家教育委员会跨世纪人才基金;国家自然科学基金

摘　　要：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 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。

关 键 词：微量吸附热 凹凸棒粘土 酸中心 碱中心 催化剂 

分 类 号：O643.36[理学—物理化学]