Use of Protein Charge Ladders to Study Electrical Interactions in Porous Membranes

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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.