NaX沸石的低温制备研究

Research on Preparation of Zeolite NaX at Low Temperature

通过水热法制备NaX沸石,采用XRD、SEM、TEM等方法考察低温合成晶化温度和晶化时间对产物的影响.结果表明,晶化温度越低,合成样品所需晶化时间越长,晶化温度提高会导致NaX沸石在Na2O-Al2O3-SiO2-H2O四元体系相图中单独形成的相区变窄,样品纯度和形貌发生变化.25℃和40℃合成产物是由单相NaX纳米粒子团聚为粒度100~300 nm的微米颗粒;60℃晶化初期产物为NaX沸石和少量杂相NaA沸石,延长晶化时间会导致杂相NaA溶解,NaX沸石是由长度约150 nm、直径约30 nm的棒状物构成的团聚体;常规温度(95℃)晶化产物为NaX和NaA沸石混合物,它们相对组成随时间变化保持不变,是生成的沸石与体系的胶体粒子的交换达到平衡所致.

Zeolites NaX were prepared by a hydrothermal method,and the influence of crystallization temperature and time at low temperature on the end products was investigated by XRD,SEM and TEM.The results showed that the lower the temperature,the longer the crystallization time.However,higher crystallization temperature favoured the formation of narrow area of single-phase zeolite NaX in the Na2O-Al2O3-SiO2-H2O quaternary system,which would lead to the changes of purity and morphology of the end products.The samples obtained at 25℃and 40℃showed microparticles(100~300 nm)were composed of highly crystalline zeolite NaX were produced.Zeolite NaX and some zeolite NaA occurred in the early stage of crystallization at 60℃,further prolonging the crystallization time and causing dissolution of heterogeneous Nat,samples zeolite NaX were aggregate particles composed of nanorods with length of 150 nm,diameter of 30 nm.In comparison,the mixtures of NaX and NaA zeolite were obtained at a normal temperature of 95℃,and their relative proportion remained constant with the reaction time increasing,which can be attributed to the equilibrium of colloidal particle exchanges between zeolite crystals obtained and the system.