碱金属离子交换Y型分子筛CO分子吸附量子化学研究

摘要

Quantum chemistry method has been employed to investigate the microscope mechanism of the adsorption of carbon monoxide (COJon alkali-ion (Li+ ,Na+ ,K+ , Rb* , Cs+ ) exchanged Y zeolites. In addition,the change of IR spectrum after CO adsorbed on zeolites has been studied in detail. Results showed that multi-molecule adsorption could take place between CO molecules and alkali-ion exchanged Y zeolites and the adsorbed behavior was similar with the structure. After single molecule or two molecules absorption, the IR spectrums of CO both showed blue shift. Two new IR adsorption bands appeared when two CO molecules were adsorbed on zeolites,and the vibration frequency was lower than that for single molecule absorption. When CO adsorbed on Li - Y or Na - Y,the vibration frequency for single molecule adsorption and two molecules adsorption changed greatly. However,the vibration frequency changed slightly when single molecule and two molecules adsorbed on K - Y, Rb - Y or Cs - Y zeolites, and the vibration frequency values for the two CO molecules were closed when dimer molecules adsorption occurred. Energy results showed that the interaction between CO and alkali ion exchanged Y zeolites tended to be weak with the increase of alkali ion radius.%应用量子化学方法,从微观角度了解一氧化碳(CO)分子吸附在碱金属离子(Li+、Na+、K+、Rb+、Cs+)交换Y型分子筛上的机理,详细研究了吸附时红外光谱的变化情况.研究发现,CO分子能与碱金属离子交换Y型分子筛发生多分子吸附,且其吸附行为和结构相类似.CO发生单分子和双分子吸附后,其红外光谱均会发生蓝移.当CO双分子吸附时,其红外光谱会出现两个新的吸附带,且其振动频率比单分子吸附时有所降低.当CO在Li-Y、Na -Y分子筛上发生双分子吸附时,其振动频率与单分子吸附时有较大差别；而CO在K-Y、Rb-Y、Cs -Y分子筛上发生双分子吸附时,其吸附前后的振动频率变化较小,且两个CO分子的振动频率很接近.能量计算结果显示,CO分子吸附强度会随着离子半径的增加而减弱.