超临界流体介导的化中等性及其对水热稳定性的有益影响
Adam S O'Neil1, Robert Mokaya, Martyn Poliakoff
1School of Chemistry, University of Nottingham, University Park, Nottingham NG7 2RD, U.K.
Journal of the American Chemical Society
|September 5, 2002
概括
超临界流体 (SCFs) 通过促进在半孔上接种来增强酸材料的热水稳定性. 这种方法提高了蒸汽阻力,特别是对于高度材料,如MCM-41.
科学领域:
- 材料科学 材料科学 材料科学
- 纳米技术纳米技术
- 化学工程是化学工程的重要组成部分.
背景情况:
- 半孔二氧化材料,如MCM-41,广泛用于催化和吸附.
- 提高这些材料的热水稳定性对于它们在苛刻的应用中长期的性能至关重要.
- 传统的化半孔二氧化的方法可以在热水条件下导致结构降解.
研究的目的:
- 为了研究超临界流体 (SCF) 作为载体和溶剂的效果,用于 mesoporous silica 的合成后化.
- 评估SCF介导的化对产生的酸材料的热水 (蒸汽) 稳定性的影响.
- 阐明SCFs影响在二氧化框架内沉积的机制.
主要方法:
- 使用超临界流体 (SCF) 作为反应介质,对半孔性二氧化 (Si-MCM-41) 进行后合成化.
- 由此产生的Al-移植酸材料的特征.
- 通过蒸汽处理评估水热稳定性,特别是对于高度化样品 (Si/Al ≤10).
主要成果:
- 超临界流体有效地将转化为半孔,形成Al-移植的酸材料.
- 与使用水性或有机溶剂制备的材料相比,SCF显著提高了化材料的水热 (蒸汽) 稳定性.
- 高度的MCM-41材料 (Si/Al ≤10) 在使用SCF进行化时,在蒸汽稳定性方面表现出显著的改善.
- 沉积主要发生在孔壁的表面,而不是在框架的深处,这是由于SCF的低溶解能力.
结论:
- 超临界流体是高效的介质,用于 mesoporous silica 的后合成化,产生具有特殊热水稳定的材料.
- 该机制涉及的表面吸附,在蒸过程中保持框架的结构完整性.
- 在需要高蒸汽阻力的应用中,SCF为生产强大的酸材料提供了有前途的途径.
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