天然CXN沸石水热改性及水热稳定性

MODIFICATION AND HYDROTHERMAL STABILITY OF NATURAL CXN ZEOLITE

以天然CXN沸石为基底材料,通过离子交换、焙烧和酸处理等方法研究了影响该沸石水热稳定性的因素。XRD、XRF和27Al MAS NMR等结果表明,CXN沸石中阳离子的种类和位置均会影响其水热稳定性,其中铵型CXN沸石的水热稳定性最高。高温焙烧铵型CXN沸石虽能提高骨架硅铝比,但骨架缺陷增多导致其水热稳定性下降。采用水热处理方法改性天然CXN沸石,考察了水蒸气量、处理温度和时间对CXN沸石骨架结构变化的影响,结果表明提高温度和水蒸气量均会降低沸石结晶度,但处理时间则对其结晶度的影响较小。

Some factors, such as calcination, ion-exchange, acid leaching etc. , were studied on influencing the hydrothermal stability of natural CXN zeolite. Characterization of CXN zeolite with XRD, XRF and ^27Al MAS NMR proved that the type and location of cations in CXN obviously influenced the hydrothermal stability of the zeolite, NH4-type CXN zeolite possessed the best hydrothermal stability. Although the framework SiO2/Al2O3 ratio of NH4-CXN zeolite could be enhanced by calcination, the hydrothermal stability of calcined NH4-CXN zeolite greatlyreduced due to the increase of followed framework defects. The effects of steam volume, treatment temperature and time on the evolution rules of CXN zeolite framework were also studied. The results indicated that raising the treatment temperature and steam volume both decreased the zeolite crystallinity, while the effect of treatment time was negligible.