摘要
用模拟退火方法研究了钠离子交换的脱水八面沸石结构中的钠离子分布.通过使用不变更的三个参量设值:结晶学不等价阳离子位Ⅰ′,Ⅱ与Ⅰ的位能差,e;—e;,e_1—e,和同时占据接邻Ⅰ、Ⅰ′位上的阳离子对间排斥能ω,模拟了不同阳离子浓度及不同温度时的NaHY沸石(Si/Al=2.46)中钠离子的分布.模拟结果与相应的实验数据有很好的符合.骨架硅铝比对位能差的影响可表达成单位晶胞中铝数目N_(A1)的线性函数:e_1;-e_1=-23.0490-0.5605N_(A1)(kJ/mol).e_1-e;=-22.4770+0.5605N_(A1)(kJ/mol).基于这一线性关系预言了不同铝含量的钠离子交换脱水八面沸石结构中的钠离子分布.将模拟退火方法研究的结果与Van Dun等人在统计热力学模型中分别通过Bragg—Williams近似或准化学平衡近似所得结果相比较.论证了早先预期准化学平衡方法优于Bragg—Williams近似的判断.
The simulated annealing method is employed to study the cation distribution in dehydrated Na-exchanged faujasite Zeolites. By use of the same three parameters , i. e. e 1 -e ,e-e 1, the site energy level differences getween sites I ' , II and I ; and w, the repulsive energy between cation pairs located on adjacent sites I and I ', the cation distribution in dehydrated NaHy-type zeolites (with a Si/A1 ratio of 2. 46) with varying cation loading ofr temperatures could be accurately predicted. It is found that the influence of the framework Al content, NA, on the site energy level differences can be expressed as e1-e1 =-23. 0490 + 0. 5605NA1(kJ/mol) and e1- e1 = -22. 4770+O. 4437NA1 (kJ/mol). By use these linear relations the cation distribution of dehydrated Na-exchanged faujasite with various Al content could be predicted excellently.
基金
国家自然科学基金资助项目
