Infrared spectra of methane adsorbed by ion-exchanged ZSM-5 zeolites
Infrared spectra of methane adsorbed by ion-exchanged ZSM-5 zeolites
复制标题
离子交换ZSM-5沸石吸附甲烷的红外光谱
作者：
T. Yamazaki;Isao Watanuki;S. Ozawa;Y. Ogino
本文测定了五种离子交换沸石（HZSM-5，LiZSM-5，NaZSM-5，KZSM-5，RbZSM-5，CsZSM-5）吸附甲烷的红外光谱，并与分别测定的吸附等温线进行了比较。红外吸收系数（A）和电子等排吸附热（qat）与交换离子的离子半径密切相关。此外，已发现阳离子位点的电场（E）按照Li+> Na+> K+> Rb+> Cs+的顺序减小。从这些结果，它已被假定，阳离子位点和甲烷分子之间的相互作用起着主导作用的吸附。此外，吸附数据表明，在沸石表面存在两种吸附位，即类硅沸石位（位1）和阳离子位（位2）。位1和位2的吸附能之差为qit-20.92kJ/mol，这与由IR数据计算的化学势差基本一致。
Infrared spectra of methane adsorbed by five kinds of ion-exchanged zeolites (HZSM-5, LiZSM-5, NaZSM-5, KZSM-5, RbZSM-5, and CsZSM-5) havebeen measured, andthe results havebeen compared with adsorption characteristics obtained from the adsorption isotherms measured separately. The shifts of the IR vi peak position (/J, the IR absorption coefficient (A), andalso the isosteric heat of adsorption (qat) have been found to be intimately related to the ionic radius of the cation exchanged. Furthermore, the electric field (E) of the cationic site has been found to decrease according to the sequence Li+> Na+> K+> Rb+> Cs+. From these results, it has been postulated that the interaction between the cationic site and a methane molecule plays a dominant role in the adsorption. In addition, the ÍR and adsorption data have revealed that there are two kinds of adsorption sites over the zeolite surface, ie, the silicalite-like site (site 1) and the cationic site (site 2). The difference between the adsorption energy for site 1 and for site 2 has been estimated to be qit- 20.92 kJ/mol, which has been almost identicalwith the chemical potential differenceevaluated fromIR data.