【摘要】 对OFF沸石进行离子交换,制备出NH4-OFF沸石,然后通过Li2CO3/NH4-OFF体系的固态反应制备了不同锂离子交换度的Li-OFF沸石.对吸附氮气和氧气的Li-OFF样品进行了7Li MAS NMR表征,结果表明,所有吸附氧气样品的部分7Li MAS NMR共振峰均发生了顺磁位移.通过对实验谱的拟合,得知Li-OFF沸石中的锂离子可分布在3类阳离子位置(A,B和C)上,对应于3个不同位移的谱峰.Li+离子并非等比例地进入3类可交换的位置,而是优先占据主孔道中的A位置,随着交换度的升高,位能较高的C和B位置上的Li离子占有率逐渐增加.在100%固态交换度样品中,Li+离子在不同离子位的占有率分别为17%(位置B),29%(位置C)和54%(位置A).其中,位置B是O2分子不可接近的,所以Li-OFF沸石中有83%的阳离子是可以接近的.更多还原

【Abstract】 NH4-OFF zeolite was obtained by ion-exchange of OFF zeolite.The Li-OFF zeolite with different exchange degree of Li+ was prepared through solid-state reaction of Li2CO3/NH4OFF system.Paramagnetic shift effect of adsorbed O2 was observed in the 7Li MAS NMR spectra of all O2-containing Li-OFF samples.By simulation of the 7Li MAS NMR spectra,it was found that Li+ was located in three types of cationic sites,corresponding to three simulated peaks.Li+ cations prefer the site A in the center of the channel.With the growth of exchange degree,Li+ appears more gradually in site B and C.As for the 100% Li+ exchanged OFF,Li+ occupy the three locations with a constant ratio: 54% site A,17% site B and 29% site C,and approximately 83% of Li+ cations are accessible to O2 molecules.更多还原