在ITQ-21中合成,表征和框架异质原子定位
Teresa Blasco1, Avelino Corma, Maria José Díaz-Cabañas
1Instituto de Tecnología Química, UPV-CSIC, Universidad Politécnica de Valencia, Avda. de los Naranjos s/n, 46022 Valencia, Spain.
Journal of the American Chemical Society
|October 14, 2004
概括
研究人员精确地控制了ITQ-21热的合成,调整了晶体大小,并防止了不必要的相. 的结合被局部化,揭示了偏好和高负载时的Ge-O-Ge对的形成.
科学领域:
- 材料科学 材料科学 材料科学
- 无机化学 无机化学
- 催化剂是一种催化剂.
背景情况:
- ITQ-21是一种有着潜在应用在催化和分离中的热石.
- 控制合成参数对于获得纯热带石相和所需性质至关重要.
- 了解像 (Ge) 这样的异质原子的结合是定制热带石功能的关键.
研究的目的:
- 为了研究ITQ-21的合成,控制结晶体大小和相纯度.
- 在ITQ-21框架中确定 (Ge) 和 (Si) 的晶体位置.
- 了解Ge负荷对热岩结构和Ge-O-Ge键的形成的影响.
主要方法:
- 在各种条件下合成ITQ-21以控制晶体体大小并避免竞争相 (CIT-5,SSZ-24,层状).
- 用X射线衍射 (XRD) 进行相位识别和结晶体大小分析.
- -19神奇角度旋转核磁共振 ((19) F MAS NMR) 谱学以定位Ge和Si.
- 理论计算以确定替代Ge的能量偏好.
主要成果:
- 合成变量被优化,以实现可调节的晶体体尺寸 (纳米晶体到微米) 和ITQ-21的高相纯度.
- 在D4R中,Ge优先占据T1晶体位置,避免Ge-O-Ge对形成.
- 在高Ge负荷 (Si/Ge=1.7) 时,Ge-O-Ge对在Ge丰富的D4R中形成,由新的 (19) F MAS NMR信号证明.
- 理论计算证实了实验结果,确定了Ge替换的能量顺序:T1 < T2 < Ge-O-Ge 在T1 < T3.
结论:
- 对ITQ-21合成的合理控制可以微调结晶体大小和相纯度.
- 在ITQ-21中将Ge纳入显示了对特定晶体学位点的偏好,影响了结构完整性.
- 高Ge负载可能导致Ge-O-Ge连接的形成,影响热岩的局部环境.
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