Modification of zeolites with organic ligands for improved separations

分离混合物以产生高纯度成分占世界能源消耗的很大一部分。从烯烃中分离烷烃，例如从丙烯中分离丙烷，是最困难和最耗能的方法之一。改进这些分离过程对于降低商品化学品和塑料生产的成本和环境影响至关重要。微孔材料，如沸石，可以根据分子大小的差异进行分离。进一步提高沸石分离效率需要新的方法来控制气体和吸附剂之间的相互作用。该项目将开发一种新的选择性控制方法，即在沸石表面和孔隙上沉积定制的有机配体。通过控制配体的性质，可以调节它们在微孔材料上的位置，以及孔的有效尺寸和化学功能。实现这种增强的控制水平可以大大改善类似大小的分子的分离，包括丙烯和丙烷。实验和计算方法将用于了解有机配体如何与沸石结合，以及有机改性材料如何影响烷烃、烯烃和其他关键气体的吸附和扩散。整个研究工作的目标是设计出用于气体分离的改进材料。本研究还与面向本科生和高中生的基于发现的学习，以及面向不同教育水平的理工科学生的在线学习工具的开发和传播密切相关。本项目旨在开发一种新的分离选择性控制方法。该方法采用有机自组装过程中使用的有机膦酸配体的受控沉积来定制沸石的外表面和孔隙。配体化学结构的变化可以用来控制它们在沸石中的组织，并且可以显著提高对类似大小的分子（包括丙烯和丙烷）的选择性吸附。实验和计算技术的结合将用于发展配体改性沸石的结构-性质关系。通过改变沸石的结构和配体的大小，这些研究将检查沉积局限于沸石外表面的情况，以及改性剂可以部分或完全进入沸石孔隙的情况。该项目还将侧重于确定如何根据配体-气体亲和的变化调整有机配体的性质，以改变气体进入沸石的扩散。最后，量子和经典分子建模工具将用于设计配体和沸石的改进组合，以适应特定的分离，如丙烷-丙烯和二氧化碳-甲烷。该项目将发展对化学工业中主要能源支出的分离过程的理解和控制能力。拟议的研究将与研究生，本科生和高中生一起进行；该团队将协作开发和实施适合级别的研究、指导和扩展目标。该团队还将开发与吸附和膜分离相关的学生可访问的主动学习工具。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The separation of mixtures to yield high purity components accounts for a large fraction of the world's energy consumption. Separations of alkanes from alkenes, for example propane from propylene, are among the most difficult and energy intensive. Improving these separations processes is vital to decreasing the cost and environmental impact of commodity chemicals and plastics production. Microporous materials such as zeolites enable separations based on differences in molecular size. Efforts to further enhance zeolite separation efficiencies require new methods for controlling interactions between the gases and sorbents. This project will develop a new approach to selectivity control that uses deposition of tailored organic ligands on the zeolite surface and pores. By controlling the properties of the ligands, it is possible to regulate their location on the microporous material as well as the effective size and chemical functionality of the pores. Achieving this enhanced level of control can yield dramatic improvements in separations of molecules of similar size, including propylene and propane. Both experimental and computational methods will be used to understand how the organic ligands bind with zeolites and how the organic-modified material affects sorption and diffusion of alkanes, alkenes, and other key gases. The overall research effort is directed toward enabling the design of improved materials for gas separations. This research is also closely linked with discovery-based learning for undergraduate and high school students and with development and dissemination of online learning tools for science and engineering students at different education levels. This project aims to develop a new approach to selectivity control in separations. The approach employs the controlled deposition of organophosphonic acid ligands used in organic self-assembly processes to tailor the zeolite external surface and pores. Changes in the chemical structure of the ligands can be used to control their organization within the zeolites and can yield dramatic improvements in the selective adsorption of molecules of similar size, including propylene and propane. A combination of experimental and computational techniques will be used to develop structure-property relationships for ligand-modified zeolites. By varying both the zeolite structure and the size of the ligands, these studies will examine cases in which deposition is confined to the external surface of the zeolites, as well as situations where the modifiers can partially or fully enter the zeolite pores. The project will also focus on determining how the nature of the organic ligand can be tuned to alter diffusion of gases into the zeolite based on changes in ligand-gas affinities. Finally, quantum and classical molecular modeling tools will be employed to design improved combinations of ligands and zeolites tuned for selected separations such as propane-propylene and CO2-methane. The project will develop understanding of and the ability to control separations processes that account for major energy expenditures in the chemical industry. The proposed research will be carried out in conjunction with graduate, undergraduate, and high school students; this team will collaboratively develop and implement level-appropriate research, mentoring, and outreach goals. The team will also develop student-accessible active learning tools related to sorption- and membranes-based separations.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.