Towards A Molecular Description of Zeolite Nucleation and Growth

沸石成核和生长的分子描述

• 批准号: 0646052
• 负责人: Daniel Shantz
• 金额: $ 40.82万
• 依托单位: Texas A&M Engineering Experiment Station
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-09-01 至 2011-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0646052&HistoricalAwards=false
• 关键词: Towards; Molecular; Description; Zeolite; Nucleation

Zeolites are highly porous aluminosilicate solids that are useful in catalysis and as molecular adsorbents. Despite the widespread use of zeolites their formation mechanism is poorly understood. Many useful synthetic zeolites are prepared using positively charged organic molecules (organocations) as templates. This project, funded by the Analytical and Surface Chemistry Program, seeks to understand how organocation - silicate association and organocation hydrophobicity influence the zeolite nucleation and growth process. The overarching goal is to develop a molecular description for how the organocation participates in zeolite nucleation and growth. This goal will be achieved using a battery of tools including solution NMR spectroscopy, most notably pulse gradient spin echo and NOESY/ROESY NMR, electrophoretic mobility (zeta potential) measurements, and small angle scattering. The intellectual merit of this work is fourfold. First, this investigation will provide a body of unambiguous knowledge about the strength of association between organocations and zeolite nanoparticles and how the nanoparticles perturb organocation solvation under a wide range of experimental conditions. Second, the strength of association between organocations and silicate oligomers in mixtures that ultimately lead to zeolite formation will be determined under a wide range of conditions. Third, the fundamental knowledge gained from this work will be used to develop new approaches to make high-silica zeolite nanocrystals, something not currently feasible. Fourth, the chemistry learned in this work has relevance in numerous areas including geochemistry, understanding the biochemistry of silica, and mesoporous oxides.The technological broader impact of this research is threefold. First, understanding zeolite nucleation and growth will lead to improvements in existing zeolitic materials, relevant to applications for which they are currently used such as catalysis and separations. Second, the development of synthetic approaches to make nanocrystals of high-silica zeolites will advance the application of zeolites in areas such as low-k dielectrics for faster electronics, thin films and membranes for selective molecular filtration, and advanced chemical sensors. Third, the body of knowledge about aqueous silicate chemistry generated here will be also of relevance to researchers in geochemistry, biosilification, and mesoporous silicas as it will provide new insights to designing oxide materials in aqueous solutions. Finally, there will be an educational broader impact engendered by a new undergraduate course, "Nanostructured Material Synthesis and Characterization." The course will introduce students to emerging nanotechnology issues in materials chemistry and engineering, and provide a research mode laboratory experience intended to encourage student involvement in undergraduate research, stimulate interest in graduate studies in nanotechnology related disciplines.

沸石是一种高度多孔的铝硅酸盐固体，可用于催化和作为分子吸附剂。尽管沸石被广泛使用，但人们对其形成机理知之甚少。许多有用的合成沸石是以带正电的有机分子(有机阳离子)为模板制备的。该项目由分析和表面化学计划资助，旨在了解有机阳离子-硅酸盐缔合和有机阳离子疏水性如何影响沸石的成核和生长过程。首要目标是开发一种分子描述，说明有机阳离子如何参与沸石的成核和生长。这一目标将使用一系列工具来实现，包括溶液核磁共振波谱，最主要的是脉冲梯度自旋回波和NOESY/ROESY核磁共振，电泳迁移率(Zeta电位)测量，以及小角散射。这项工作的学术价值有四个方面。首先，这项研究将提供关于有机正离子与沸石纳米颗粒之间的缔合强度以及在广泛的实验条件下纳米颗粒如何干扰有机正离子溶剂化的明确知识。其次，混合物中有机阳离子和硅酸盐低聚物之间的缔合强度将在广泛的条件下确定，最终导致沸石的形成。第三，从这项工作中获得的基本知识将被用来开发制造高硅沸石纳米晶体的新方法，这是目前尚不可行的。第四，在这项工作中学到的化学在许多领域都有相关性，包括地球化学、理解二氧化硅的生物化学和介孔氧化物。这项研究的技术更广泛的影响有三个方面。首先，了解沸石的成核和生长将导致现有沸石材料的改进，这些材料与目前使用它们的应用相关，如催化和分离。其次，合成高硅沸石纳米晶的方法的发展将促进沸石在诸如用于更快电子的低k介电材料、用于选择性分子过滤的薄膜和膜以及先进的化学传感器等领域的应用。第三，这里产生的有关硅酸盐水化学的知识体系也将与地球化学、生物硅化和介孔二氧化硅的研究人员相关，因为它将为设计水溶液中的氧化物材料提供新的见解。最后，一门新的本科课程“纳米结构材料合成与表征”将对教育产生更广泛的影响。该课程将向学生介绍材料化学和工程中新出现的纳米技术问题，并提供一种研究模式的实验室经验，旨在鼓励学生参与本科生的研究，激发对纳米技术相关学科的研究生学习的兴趣。