GOALI: Fundamental Studies of Transport of Mixtures in Microporous Membranes under Supercritical Conditions

本项目是一个学术/工业合作研究（GOALI）项目，旨在研究超临界碳氢化合物/二氧化碳混合物在微孔碳分子筛膜中的传输。本研究将分两部分进行：(1)膜的制备和实验表征，并对其合成过程中的结构演变进行计算建模；(2)测量和同时计算机模拟超临界混合物在膜内的吸附和传输。所研究的系统是由二氧化碳和下列一种或多种碳氢化合物组成的超临界混合物：丁烷、异丁烷、苯和甲苯。这些碳氢化合物被选择代表典型的脂肪族和芳香族化合物，并允许探索因素，如分子形状。非平衡大正则分子动力学（NEGCMD）模拟技术被用于研究这些混合物在微孔材料中的输运。分子计算的目的是将膜的分子结构与实验观察到的转运性质和分离效果联系起来。长期目标是为分子筛和催化膜反应器实现可靠的工程和改进材料的设计。这些研究结果将有助于超临界CO2吸附剂再生和超临界条件下膜的使用等应用。碳分子筛膜能够承受与超临界条件有关的高压和高温。它们的孔隙度和孔径控制得很好，孔径分布很窄。基于膜内分子迁移率的差异，了解决定这些材料分离超临界混合物能力的因素，将促进它们在去除水中、污泥、土壤、废催化剂和颗粒活性炭等吸附剂中的各种污染物方面的应用。与通常用于从超临界溶剂中分离溶质的耗能膨胀/再压缩循环相比，从超临界二氧化碳中连续去除溶质的能力将显著降低运营成本。

ABSTRACT This project is a collaborative academic/industrial research (GOALI) project to investigate the transport of supercritical hydrocarbon/CO2 mixtures in microporous carbon molecular-sieve membranes. The study will proceed in two parts: (1) preparation and experimental characterization of the membrane along with computational modeling of the evolution of its structure during synthesis; and (2) measurement and simultaneous computer simulation of the sorption and transport of supercritical mixtures within the membranes. The systems under study are supercritical mixtures composed of CO2 and one or more of the following hydrocarbons, butane, isobutane, benzene, and toluene. These hydrocarbons were selected to represent typical aliphatic and aromatic compounds and to permit exploration of factors such as molecular shape. Non-equilibrium grand canonical molecular dynamics (NEGCMD) simulation techniques are being used to study the transport of these mixtures in microporous materials. The objective of the molecular calculations is to relate and correlate the membrane's molecular structure with experimentally observed transport properties and separation efficacy. The long-term goal is to achieve reliable engineering and design of improved materials for molecular sieves and catalytic-membrane reactors. The results of these studies will contribute to applications such as the regeneration of adsorbents by supercritical CO2 and the use of membranes under supercritical conditions. Carbon molecular- sieve membranes are capable of withstanding the high pressures and temperatures associated with supercritical conditions. They can be prepared with well-controlled porosity and pore size and a very narrow pore-size distribution. Understanding the factors determining the ability of these materials to effect separations of supercritical mixtures based on differences in molecular mobility within the membranes will promote their use in the removal of various contaminants from water, sludges, soils, spent catalysts, and adsorbents like granular activated carbon. The ability to remove solutes continuously from supercritical carbon dioxide would produce significant reductions in operating costs compared with the energy-intensive expansion/re-compression cycle normally used to separate solutes from supercritical solvents.