四面体协调Al对Mg-Al二元混合氧化物表面酸度的影响
Vidya Chandrabose1, Taeho Kim1, Ji Won Park1,2
1Department of Energy and Materials Engineering, Dongguk University-Seoul, Seoul 04620, Republic of Korea.
Molecules (Basel, Switzerland)
|August 26, 2023
概括
从层状双氧化物 (LDH) 中合成的Mg-Al金属氧化物 (MO) 表明,富含Al的MO具有最高的易斯酸度. 酸度与暴露的Al3+-O2-位点有关,当Mg/Al比率超过2时显著减少.
科学领域:
- 材料科学 材料科学 材料科学
- 催化剂是一种催化剂.
- 表面化学 表面化学
背景情况:
- 层状双氧化物 (LDH) 是混合金属氧化物的前体.
- 在金属氧化物 (MO) 中调整Mg/Al比率可以改变其表面特性和酸度.
- 了解合成,结构和易斯酸度之间的关系对于催化应用至关重要.
研究的目的:
- 通过分层双氧化物 (LDH) 的化,合成具有不同Mg/Al比率的Mg-Al金属氧化物 (MO).
- 研究合成的MO的结构,纹理和表面特性.
- 为了评估MO的易斯酸度作为它们的Mg/Al比率和表面Al物种的函数.
主要方法:
- 合成Mg-Al分层双氧化物 (LDH),然后进行化,形成金属氧化物 (MO).
- 用X射线衍射 (XRD) 来进行晶体阶段和结晶性分析.
- 27Al神奇角度旋转核磁共振 (MAS NMR) 用于Al协调和表面物种.
- 的物理吸收用于特定表面积的确定.
- 温度调节的氨溶解 (TPD-NH3) 用于量化易斯酸度.
主要成果:
- 所有合成的MO都含有具有相似结晶度的危氧化物 (MgO) 结晶体,无论Mg/Al比率如何.
- 将LDH化成MO导致在MO表面具有不和协调的Al3+离子.
- 具体表面积在100-200 m2/g之间,并没有受到金属比率的显著影响.
- 对富含Al的MO (Mg/Al比为1) 观察到的易斯酸度最高,归因于暴露的Al3+-O2-对.
- 露出四面体Al位点时,易斯酸度增加,当Mg/Al比率超过2时,急剧下降.
结论:
- /的比率显著影响了由LDH衍生的MO的易斯酸度,主要是由于表面的Al物种.
- 富含Al的MO (Mg/Al=1) 呈现出最佳的易斯酸度,这是由于活性Al3+-O2位点的高效暴露.
- 这些MO的多孔结构和结晶性在很大程度上独立于研究范围内的Mg/Al比率.
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