Molecular-Based Study of Reversed Micelles in Supercritical in Carbon Dioxide for Solvent Substitution in the U.S. Chemical Industry

基于分子的研究超临界二氧化碳中的反胶束用于美国化学工业中的溶剂替代

• 批准号: 9613555
• 负责人: Peter Cummings
• 金额: $ 34.57万
• 依托单位: University of Tennessee Knoxville
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1996
• 资助国家: 美国
• 起止时间: 1996-10-01 至 2000-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9613555&HistoricalAwards=false
• 关键词: Molecular; Based; Study; Reversed; Micelles

9613555 Cummings It is proposed to use small angle x-ray (SAXS) and neutron (SANS) scattering plus complementary molecular dynamics (MD) and Monte Carlo (MC) simulations to develop a molecular-level understanding of the formation and stability of reverse micelles (RMs) in supercritical carbon dioxide (SC-CO2). The results of this project will contribute to the fundamental knowledge base for the U.S. chemical industry to substitute SC-CO2 for many of the toxic or hazardous solvents presently used in most industrial chemical reaction and separation processes. Despite its attractive features as a solvent substitute, SC-CO2 is not a good solvent for certain classes of substances, e.g. 1) water, water-soluble, and polar substances or 2) most high molecular weight substances such as synthetic polymers or proteins. Techniques have been proposed, however, for processing these insoluble substances in SC-CO2 through the use of RMs. Recently, after a decade-long search, appropriate surfactants have been discovered to disperse both aqueous systems and polymers in RMs andSC-CO2. The aim of this work is to understand how the detailed molecular characteristics of the newly discovered surfactants contribute to the formation of RMs to understand what makes a successful CO2 -philic surfactant tail, to characterize the interfacial layer between the continuous SC-CO2 phase and the microscopic RM core, to establish the basis for predicting and measuring the size and shape of RMs, in short, to provide the molecular foundations for the needed knowledge base for widespread industrial utilization RMs in SC-CO2 as substitute for liquid solvents. It is proposed to apply four molecular-based techniques to study RMs in SC-CO2: 1) SANS for its ability to vary contrast between specific molecular components through selective deuteration, 2) SAXS for its high productivity and different contrast compared with SANS, 3) MC for its efficient exploration of the configuration space, and 4) MD for its capability to explore dynamical processes at a molecular level. Scattering can tell much about the microstructure (spheres? rods? lamella? biocontinuous structures?) and macrostructure (clustering?) of RMs which is unavailable by other means. Both the 30-m SANS instrument at ORNL with the existing high pressure SAXS cell, will be used to characterize RMs with both polymer and water cores. And the massively parallel Intel Paragon supercomputers at ORNL, will be used to simulate RMs from the newly discovered surfactants in SC-CO2 using accurate models developed from the OPLS parameter set. The combination of the power of the Paragon supercomputers and the efficiency of our parallel techniques will permit determination of the stability of preconstructed RMs. A primary goal will be to make quantitative comparisons between the stable RM structures as determined by SANS and SAXS experiments and those determined by simulation. Then, it is proposed to use simulation experiments, with available thermodynamic data, to understand the balance of interactions that is required to form stable RMs in SC-CO2, and thus to understand the molecular structure required for a successful surfactant. With anticipated success in the proposed SANS, SAXS, MC, and MD studies, a full repertoire of molecular-based tools for study of RMs in SC-CO2 would be available. With these tools it is proposed to test and adapt existing thermodynamic models of aqueous RMs, e.g., those Nagarajan, Blankschtein, and Holland, to RMs in SC-CO2 . With both molecular and thermodynamic models, it is proposed to suggest novel surfactants for synthesis and testing. Achieving even a small fraction of this degree of success, will substantially enhance the knowledge base for widespread substitution of SC-CO2 to replace conventional liquid solvents in the U.S. chemical industry. A more competitive industry with reduced emissions will be the ultimate result. ***

本文提出利用小角x射线（SAXS）和中子（SANS）散射加上互补分子动力学（MD）和蒙特卡罗（MC）模拟来发展对超临界二氧化碳（SC-CO2）中反胶束（RMs）形成和稳定性的分子水平理解。该项目的成果将为美国化学工业提供基础知识基础，以取代目前大多数工业化学反应和分离过程中使用的许多有毒或危险溶剂。尽管SC-CO2作为一种溶剂替代品具有诱人的特性，但它不是某些类别物质的良好溶剂，例如：1)水、水溶性和极性物质，或2)大多数高分子量物质，如合成聚合物或蛋白质。然而，已经提出了通过使用rmms处理SC-CO2中这些不溶性物质的技术。最近，经过长达十年的研究，人们发现了合适的表面活性剂，可以分散rm和sc - co2中的水体系和聚合物。这项工作的目的是了解新发现的表面活性剂的详细分子特征如何有助于RM的形成，了解是什么使一个成功的亲CO2表面活性剂尾部，表征连续的SC-CO2相和微观RM核心之间的界面层，为预测和测量RM的大小和形状建立基础，总之，为广泛的工业应用SC-CO2中的RMs作为液体溶剂的替代品提供所需的知识基础。提出了四种基于分子的技术来研究SC-CO2中的RMs: 1) SANS能够通过选择性氘化改变特定分子组分之间的对比度；2)SAXS具有与SANS相比的高生产率和不同对比度；3)MC能够有效地探索构型空间；4)MD能够在分子水平上探索动态过程。散射可以告诉我们很多微观结构(球体？棒吗?薄板吗?生物连续结构？)和rmms的宏观结构（聚类？），这是其他方法无法获得的。ORNL的30米SANS仪器和现有的高压SAXS电池将用于表征聚合物和水岩心的均一值。ORNL的大规模并行英特尔Paragon超级计算机将使用从OPLS参数集开发的精确模型来模拟SC-CO2中新发现的表面活性剂的均方根。Paragon超级计算机的能力和我们并行技术的效率相结合，将允许确定预构建的均方根的稳定性。主要目标将是对由SANS和SAXS实验确定的稳定RM结构与由模拟确定的结构进行定量比较。然后，提出利用现有的热力学数据，利用模拟实验来了解SC-CO2中形成稳定均方根所需的相互作用平衡，从而了解成功的表面活性剂所需的分子结构。随着拟议的SANS、SAXS、MC和MD研究的预期成功，SC-CO2中RMs研究的完整的基于分子的工具将可用。利用这些工具，建议测试和调整现有的水相均方根热力学模型，例如，Nagarajan， Blankschtein和Holland的模型，以适应SC-CO2中的均方根。结合分子和热力学模型，提出了用于合成和测试的新型表面活性剂。即使取得这一成功程度的一小部分，也将大大提高美国化学工业中广泛使用SC-CO2替代传统液体溶剂的知识库。最终的结果将是一个排放量减少、更具竞争力的行业。＊＊＊