CXN天然沸石的研究——Ⅰ.离子交换与结构性质表征

Studies on CXN Natural Zeolite——Ⅰ. Ion Exchange and Structural Characterization

采用离子交换和焙烧等方法,对我国CXN天然沸石(STI型)进行改性.应用化学分析,粉末XRD,TG/DTA,^(27)Al MAS NMR,^(29)Si MAS NMR,低温N_2吸附等方法表征相关的结构、离子交换等性质.CXN沸石的晶胞组成Na_(0.2)Mg_(0.1)Ca_(8.4)[Al_(17.2)Si_(54.8)O_(144)]·65H_2O,属富钙型.经离子交换脱出Ca^(2+)后的沸石在焙烧过程中伴随有骨架脱铝,骨架的热稳定性已由原样的500℃以下提高到700℃以上.交换改性后的沸石,呈现反映该沸石微孔特性的Ⅰ型氮吸附等温线.

CXN zeolite, a natural STI type zeolite in China, was modified by ion exchange and calcination. The structural properties of raw zeolite and modified zeolite were characterized by chemical analysis,powder XRD, TG/DTA, 27Al MAS NMR,29Si MAS NMR and nitrogen adsorption. The raw zeolite is rich in calcinium with cell composition of Na0.2Mg0.1 Ca8.4 [Al17.2Si54.8O144]·65H2O. After treatment of ion-exchange and de-calcinium, the zeolite was found to be de-alunminumated in the framework during calcination. Therefore the thermal stability of the modified zeolite was increased from 500℃ for raw material to 700℃. The type I adsorption isotherm of nitrogen proved the nature of the micropore in the zeolite.