金属离子改性分子筛对CO_2的吸附研究

Study on Adsorption of CO_2 on Modified Molecular Sieves

以金属盐溶液浸渍的方法对13X,4A分子筛进行改性,选用了4种有代表性的碱土金属和过渡金属离子Ca2+,Sr2+,Zn2+,Cu2+。红外光谱分析结果表明,负载二价金属离子的分子筛上CO2的表面吸附态可以归属为一种线式吸附态和一种剪式吸附态,还有CO2分子非线性化学吸附在氧化物表面上所形成的类碳酸盐物种吸附态。对两种改性分子筛进行了CO2-TPD研究,CO2-TPD谱图上一般出现两个或两个以上的脱附峰,对照红外分析结果表明,低温脱附峰对应线式吸附态的CO2分子脱附,中温脱附峰对应剪式吸附态和类碳酸盐吸附态的CO2分子脱附。

4 A and 13X molecular sieves containing alkaline-earth and transition metal cations were prepared by impregnating them in relevant Ca2+, Sr2+ , Zn2+or Cu2+ solutions. Results of IR indicated that adsorption forms of CO2 on molecular sieves could be as follows: linear configuration, shear shape adsorption state and carbonate-like species formed by chemisorption of CO2 on surface of oxides. CO2-TPD of modified molecular sieves were studied. There were two or more desorption peaks. Comparing the results with those of IR's showed that low-temperature peak represented desorption of linear configuration CO2 molecules, and midst-temperature peak represented desorption of CO2 with shear shape adsorption state and carbonate-like species state. Diffusion control of desorption on 4A molecular sieve could be the reason of forming the third peak.