Keith E. Gubbins - US grants

The thermodynamic properties and phase equilibria of molecularly complex fluid mixtures are being studied using computer simulation and theoretical methods. The research is part of a comprehensive program that combines the methods of theory, simulation, and experiment. The study focuses on three types of fluids: those composed of nonspherical and polar molecules, hydrogen-bonded and associated molecules, and electrolytes. Increasingly sophisticated molecular dynamics and Monte Carlo simulation techniques are being developed to study such mixtures. These simulations are used to test both the statistical mechanical theories (perturbation and resummed cluster expansions) that are being developed, and also the intermolecular force models for these fluids. If successful, these methods will eventually replace the highly simplified and ad hoc methods used by engineers for complex mixtures.

This work is part of a larger program, with the general title, "Molecular Thermodynamics," which combines the methods of experiment, theory, and computer simulation in a coordinated study of dense fluids. Experimental studies of pressure-temperature-composition (PTX) phase diagrams are underway for a variety of binary fluid mixtures that exhibit nonideal behavior, including gas-liquid, liquid-liquid, and gas-gas phase equilibria. Emphasis is placed on mixtures containing polar liquids (HC1, H;i2S, CH;i3OH, CH;i3C1, SO;i2, etc.) and on the effect of molecular shape on phase equilibria. The principal purpose of these experiments is to provide data of high accuracy, covering wide ranges of temperature and pressure (70 to 500;soK and pressure to 4000 atm), for use in testing and refining molecular theories of dense fluids. Among the molecules studied are: HC1, HBr, CH;i3C1, (CH;i3);i2O, CO;i2, COS, BF;i3, c-C;i3H;i6, NF;i3, NH;i3, C(CH;i3);i4, PF;i5, SF;i6.

This award provides for a graphics workstation that will be used to display the results of large-scale numerical computations, including research on the computer simulation of blood flow in capillary networks, a variety of surface phenomena (fluid adsorption and diffusion in narrow capillary pores, surfactant behavior, nucleation, etc.), materials processing, and in molecular modeling of immobilized protein structures. Such simulations produce large quantities of raw data, and a sophisticated graphics station is needed to interpret and display the results. Four research groups will use the facility.

This project is aimed at developing a predictive theory for the thermodynamics and phase equilibria of fluid mixtures in which molecular association, due to H-bonding and complexing is important. A simple and successful theory has been derived recently for such mixtures; this is developed for practical use in the form of an equation of state. Fundamental aspects of the research include the development of more realistic intermolecular force models and an extension to multiple binding sites in a molecule. The proposed equation of state uses a reference term that includes the effects of association as well as those of the repulsive forces. Extensive comparisons with experimental data and with existing equations of state are presented. In parallel, the investigators carry out both molecular dynamics and Monte Carlo computer simulations of such fluids, in order to test both the theory and the force models. Included in the investigations is a study of adsorption and surface tension at fluid-fluid interfaces for such fluids. This work is an Industry-University Collaboration between Cornell and the Exxon Research and Engineering Company. Existing equations of state are, almost without exception, based on the idea of a reference fluid of hard molecules (usually hard spheres) that exhibit repulsive forces only. Such an equation cannot describe substances in which molecular association occurs due to strongly attractive off-center sites. Such association occurs in a wide variety of industrially important substances. The current method of dealing with this problem is to use the existing equations of state with the addition of the "chemical" approximation, in which chemical reactions are postulated to account for the association. This introduces temperature dependent equilibrium constants into the equations. In practice, these may not be available from independent experiments and must be fitted to thermodynamic data. This results in a method of little predictive value, particularly for multicomponent solutions. The proposed work is aimed at replacing such methods by a physical approach that is soundly based in statistical mechanics and has greater predictive value.

This award will enable Prof. Keith E. Gubbins and colleagues at Cornell University to collaborate with Prof. K. Nakanishi and co-workers at Kyoto University, Japan, over a period of two years. They will continue a cooperative research program which has advanced the use of computer simulation techniques to investigate the thermodynamic properties of fluids and mixtures of fluids, as well as their structural properties at the molecular level. The techniques to be used involve statistical (Monte Carlo) and more classical analytical computer solutions of the equations of molecular dynamics. The purpose of this research is to make possible the reliable prediction of the physical properties of fluid mixtures, such as those involving natural gas and petroleum, that are used in industrial and other chemical processes. The fluids studied here will be those which associate strongly, such as alcohol and water. The phase equilibria of such mixtures are so complex that no satisfactory theory for them has been available. Computer simulations will be performed to study the thermodynamic, phase equilibrium, and dynamical properties of the bulk phases of these aqueous solutions, and the work will then progress to a study of the adsorption of associating molecules at phase interfaces. This research may lead to significant improvements in production, processing, and separation methods.

This award will support continued collaboration between Dr. Keith Gubbins, Cornell University, and Professor John S. Rowlinson, Physical Chemistry Laboratory, Oxford University, England. The objective of the research is to study the behavior of fluids in micropores at the molecular level, using the methods of statistical mechanics and computer simulation. This collaboration grew out of studies of liquid drops, started independently at Cornell and Oxford, and has continued actively over the last few years. The investigators will use statistical mechanical theory and molecular simulation to develop a fundamental understanding of the phenomena associated with adsorption in micropores, including selective adsorption of a particular component, phase transitions, layering transitions, and hysteresis. The role of such variables as the type of fluid and solid material, nature of the surface and pore size, pore shape, and state conditions (temperature, pressure, and composition) will be studied. The validity of classical thermodynamic relations such as the Kelvin equation will be examined. The investigators will then use the results of this work to suggest the molecular design of advanced adsorbents for particular applications, including selective extraction of particular constituents of mixtures, the storage of natural gas at low pressure, and improved desiccant materials. Both the U.S. and British investigators are at the forefront of work on statistical mechanics of combined fluids and have made important contributions to this industrially relevant area of research.

A study of the behavior of fluids in porous solids emphasizing interactions between the walls and fluids in the micro- and meso-pore ranges. The work will encompass statistical mechanical theory, computer simulation, and experimental verification. The principal goals are: (1) basis understanding of the role of slate conditions, pore material, and pore morphology on typical properties as phase transitions, layerigtransitions, adsorption, wetting, and diffusion, and (2) the application of the newly developed theory to suggest specificity of adsorbent species for particular applications. Initial studies will be with polycarbonate materials followed by experiments and theoretical studies on well characterized ceramic materials.

This award will facilitate continued cooperation between chemical engineers at Cornell University and Kyoto University. The project is part of a larger project in the field of molecular thermodynamics that includes research on fluids by means of the methods of statistical mechanics and computer simulation. In previous research conducted by the two groups, the effect of molecular association on the properties of associating fluids has been studied by simulation for simple and realistic potential models. This project will focus on studies of water and aqueous mixtures. In particular, the scientists will carry out investigations on theoretical and simulation studies of water-methanol mixtures; molecular dynamics simulations of the behavior of water in microporous materials, including carbons, silicas, and clays; and simulations of rapid cooling in polyol-water mixtures. The Cornell group, led by Professor Keith E. Gubbins and Professor Paulette Clancy, will provide expertise in the theoretical methods and simulation techniques for studying micropores and rapid cooling. The Japanese group, under the leadership of Professor Koichiro Nakanishi, has complementary expertise in developing intermolecular potential models for these systems and in molecular dynamics techniques applied to aqueous mixtures. The long term aim of the research project is to understand fluids and fluid mixtures of associating molecules (involving H-bonds, charge-transfer complexes, etc.) in detail at the molecular level. The approach has been based on the use of fundamental statistical, mechanical, mean-field and perturba- tion theories, as well as Monte Carlo and molecular dynamics computer simulations. The simulations are used to test the theoretical predictions for a well-defined potential model, and also to investigate phenomena that are difficult or impossible to study by experiment.

The PI proposes to purchase a Omnisorp 100 CX sorptometer (an adsorption) porosimeter) from Coulter. The instrument measures the surfaces area, pore volume, and micropore (20 A) and mesopore (20-500 A) size distribution of a porous solid sample based on the physical adsorption of N2. A volumetric method is used to measure the adsorption and desorption isotherms over a large pressure range, and from these the pore characteristics of the material can be calculated. The PI, together with collaborators, will use this instrument in several related studies, including: (i) Experiments to obtain date in well-characterized porous materials, and comparisons of this data with theoretical results using modern statistical mechanical Monte-Carlo and molecular dynamic simulations and (ii) characterizations of the porosity of intercalated composite silicate materials, and high surface area aluminas, silicas and alumino-silicates. The molecular dynamics simulations of the PI are of the highest quality, and the purchase of this instrument will facilitate the comparison of the simulations with experiments. The instrument will further the research of collaborators working on new layered and catalyst porous materials.

9302837 Gubbins This award provides funds to permit Dr. Keith E. Gubbins, School of Chemical Engineering, Cornell University, to pursue with Dr. Soong-Hyuck Suh, Department of Chemical Engineering, Keimyung University, and Dr. Soon-Chul Kim, Andong University, Korea, for 24 months, a program of cooperative research on the behavior of fluids in narrow pores and in microporous media using the methods of statistical mechanics and molecular simulation. The objectives of the research are (1) to use several molecular dynamics and Monte Carlo simulation techniques to study the equilibrium and transport properties of simple fluid and their mixtures in porous media having simple geometries, (2) to use these computer experimental results to test recently developed density functional and kinetic theories of fluids in pores, (3) to study networking effects in porous media using molecular dynamics simulation techniques, (4) to study the adsorption and dynamical behavior of water in porous carbons, and (5) to further develop and improve the density functional and kinetic theories for fluids in porous media. Microporous materials are widely used in the chemical, oil and gas, pharmaceutical, and food industries to carry out chemical reactions and for purification and separations. The collaborators expect the proposed work to help them design improved processes and materials for these industries. The collaborators are recognized as experts in the field of the proposal. They will be assisted by several postdoctoral workers and graduate students. This project is relevant to the objectives of the U.S.-Korea Cooperative Science Program which seeks to increase the level of cooperation between U.S. and Korean scientists and engineers through the exchange of scientific information, ideas, skills, and techniques and through collaboration on problems of mutual benefit. Korean participation in the project is supported by the Korea Science and Engineering Foundation (KOSEF). Thi s project adds an international cooperative dimension to the PI's research under NSF Grant No. CTS-9122460. ***

This award supports the travel to Australia by two U.S. investigators as part of a cooperative research program between Cornell University and the Australian National University to study the transport behavior of fluids in narrow pores, using the methods of nonequilibrium statistical mechanics and molecular simulation. The senior collaborators will be Professor K. E. Gubbins and Dr. L. A. Pozhar from Cornell and Professor D. J. Evans at the Australian National University. The objectives of the research, to be conducted over a two year period, are to develop and test a kinetic theory of inhomogenius fluids, and to apply it to the prediction of diffusion, viscous flow and heat transport in model micropores. In addition, molecular dynamics simulations will be used to test the kinetic theory and nonequilibrium simulations of transport processes in micropores of simple geometries (slits and cylinders) will be made to obtain an understanding of the effects of pore size and shape, type of pore wall, and state conditions on transport processes in such confined fluids. Microporous materials are widely used in industry to carry out chemical reactions and to effect purification and separations. The proposed work is needed to design better and more efficient processes for such industries. This project, supported jointly by NSF and the Australian Department of Industry, Technology and Commerce (DITAC), brings together the expertise of the researchers in computational and theoretical statistical mechanics.

9309835 Gubbins The behavior of fluids in microporous and membrane systems will be investigated using novel methods, that allow the permeability of the pore wall to be controlled while maintaining its atomic nature. A realistic model of the micropore will be developed based on these methods. The fluid behavior will be studied with respect to its structural, thermodynamic and transport properties. Special attention will be given to the study of anisotropy in viscosity and thermal conductivity in confined systems. Non-equilibrium molecular dynamics (NEMD) methods will be developed for investigating these transport properties.

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9321100 Gubbins Partial support is sought for invited speakers from the United States to attend the Fourth Liblice Conference on the Statistical Mechanics of Liquids, to be held at Lake Milovy, Czech Republic on June 6-10, 1994. The Czech Academy of Sciences is organizing and hosting the conference, and will cover all local costs within the Czech Republic. Unique features of the conference will include: (a) coverage of the most recent molecular methods and results for complex liquids and interfaces, including ionic and associated liquids, colloids and micellar solutions, self-assembly, aqueous solutions, surfactants and adsorbents, etc., (b) latest developments in advanced molecular simulation techniques, including parallel and distributed systems, (c) coverage of both applied and basic aspects, and (d) an opportunity for U.S. researchers to become familiar with leading research in this area by groups from East and West Europe, Japan and Australia. The invited speakers will include many of the international experts from these countries. Previous conferences were held in 1983, 1986, and 1990, and received widespread acclaim from U.S. attendees. ***

ABSTRACT CTS-9508680 Keith E. Gubbins Cornell University Micro-and meso-porous solids find widespread use in the chemical, oil, pharmaceutical and food industries as adsorbents and membranes for separation processes, and as catalysts and catalyst supports. At present the design of such processes and materials is largely empirical. The aim of this project is to provide more powerful methods, based in molecular theory and simulation, for prediction of absorbed fluid behavior and for the design of improved processes. Modern statistical mechanical methods, including density functional theory, simulation, and kinetic theory will be employed to carry our studies in four areas: 1. Development of an improved method for pore size distribution (PSD) analysis. Density functional theory proves much more powerful than classical methods for determining PSD's from absorption isotherms. This method, which is already findine commercial application for carbons, will be extended to gases other than nitrogen, and to materials such as aluminosilicate and oxide molecular sieves, which have cylindrical pore geometries. 2. Molecular simulations will be used to develop and understanding of the importance of connectivity effects in networks for both pure fluids and mixtures. The effects of connectivity on both diffusion rates and absorption isotherms will be investigated. Goals include incorporation of network effects into PSD analyses, and understanding how networks can hinder and promote separations. 3. Selective absorption of trace components in gas streams. Calculations will be made to elucidate the role of pore and system variables on the selective absorption of trace contaminants in nitrogen and air streams for materials with pores of cylindrical geometry. Specific case studies will be made for several trace halocarbons in a range of molecular sieves, carbons and oxides. The goal of this work is to develop methods for designing improved absorbents for removal of trace contaminants. 4. Viscou s flow and diffusion in pores. Nonequilibrium molecular dynamics methods will be used to study viscous flow and mutual diffusion in mixtures in pores. The goal of this work will be to develop an understanding of the role of fluid-wall interactions and pore shape and size on these transport processes.

Microscopy is ubiquitous among measurement methods in the biological sciences and related engineering disciplines. Virtually all laboratories at MIT utilize some form of microscopic technology, yet these images are commonly obtained, stored, and analyzed on individual machines using commercially-available systems and standardized processing software. Interpretations often remain qualitative, and storage capabilities available to individual users limit data transfer speed and the number of raw and processed images that can be maintained. Today, however, computerized networks can greatly enhance and extend image acquisition, processing, analysis, storage, and interpretation. Accordingly, this project aims to develop a Quantitative Microscopy & Image Processing Network (QMIPN) that will enable access to facilities capable of acquiring, transferring, storing, and recalling images rapidly and efficiently. Advanced methodologies for quantitative image interpretation will be available from both central and remote sites. QMIPN will also serve as a platform for developing new imaging modalities, further enhancing hardware and software image processing modules, and establishing automated and remote forms of image acquisition and analysis. Three phases are planned: PHASE I -- The Principal Investigators will use relevant research projects as prototypes to define network capabilities. Light, fluorescent, confocal, atomic-force, and transmission electron microscopes will be connected to a central server/router. These microscopes will be adapted to provide common interface, data storage, and analysis paradigms, along with automated remote access and image manipulation. Local computer terminals will control each microscope and sample, communicate with the central processor, and perform basic image filtering. Acquired images will be transported via high-speed ATM connections and downloaded to large capacity systems so that more complex, computer-intensive proces sing methods can be employed. PHASE II -- This network will be broadened to involve an increased number of investigators and projects, employing either the core microscope facilities or their own individual laboratory microscope facilities. Inexpensive new CD-ROM writing capabilities will be used to create a large database of stored images. By developing indexing and retrieval methods, these images can be a world-wide source of information. PHASE III -- The network will be extended to an even wider group of investigators both on and off campus. Accessibility of our network through the Internet will provide a powerful teaching tool that can be tapped by other less-advantaged institutions with a relatively small investment. This would raise the possibility of developing innovative outreach programs to enrich curricula, e.g., at smaller minority schools that do not have strong research programs. Three major benefits will grow as the network develops: 1. Increased research efficiency and innovation, resulting from multi-user facilities involving investigators with diverse interests and skills, in terms of both applications and techniques; 2. Increased research productivity, resulting from wide dissemination and application of stateof-the-art image acquisition and processing methods; 3. Increased cooperation among scientists and engineers on and off campus in terms of both research and teaching, resulting from the ease of access to visual images display and analysis from electronic information networks. Substantial matching funds have already been raised from a variety of institutional and other non-federal sources, standing ready to be leverage this grant.

CTS-9700842 Gubbins Cornell University ABSTRACT Seven invited speakers from the U.S. will be provided partial support to attend the International Conference on Advances in Chemical Engineering, to be held at ITT, Madras on December 11-13, 1996. The conference is organized by a national committee, with advice from an International Scientific Advisory Committee. This is the first conference of this type to be held in Madras, although a similar Chemical Engineering conference was held in Bangalore about ten years ago. The conference possesses several unique features: (a) an opportunity to discuss and learn about the most recent scientific and technological advances in a broad range of areas of chemical engineering, particularly areas of current importance in Asia and Europe; (b) there will be an industrial session, with several keynote speakers and other presentations on R&D and New Technologies; ( c ) coverage of applied, as well as fundamental, aspects; (d ) discussions of recent and future trends in chemical engineering education with leading educators from India, Japan and Europe.

The first careful experimental studies of gas-liquid phase separation (capillary condensation) in well characterized materials, giving the full gas-liquid phase diagram and critical point for a range of confined systems, were recently reported by Thommes and Findenegg. In this project, the PIs will use Grand Canonical Monte Carlo simulation to study these phase changes in controlled pore glasses (CPGs), with a view to understanding and interpreting the confinement effects involved. The simulations will employ an efficient parallelized Monte Carlo program, based on histogram methods, and using the SemiGrand Ensemble. Models of CPG will be prepared by two different methods involving the use of Quench Molecular Dynamics to quench supercritical silica. These methods will be tested and the best will be used in the future work. The absorption, and phase transitions for sulfur hexafluoride in CPGs of various pore diameters will be calculated and compared with the experimental data. This work will be followed by studies of melting and freezing of simple fluids in CPGs, and again comparisons with experiment will be an important part of the project.

ABSTRACT CTS-9712138 K. Gubbin/Cornell Nanoporous solids find widespread use in the chemical, oil, pharmaceutical and food industries as adsorbents and membranes for separation processes and materials is largely empirical. The aim of this project is to provide more powerful methods, based in molecular theory and simulation, for prediction of adsorbed fluid behavior and for the design of improved processes. Modern statistical mechanical methods, including molecular simulation and kinetic theory, will b employed to carry our studies in three areas: 1. Phase separation in porous media will be studied by novel molecular simulation methods (including quench molecular dynamics, Monte Carlo with histogram reweighting, etc.). Three separate investigations are planned. The first will aim to model capillary condensation in well-characterized controlled pore glasses (CPG), for which high quality experimental data have been recently become available; a goal of this work will be to develop sophisticated models that will be useful in other CPG studies. The second will be a study of freezing and melting of fluids confined within nanoporous materials; systems studied will include the adsorbates neopentane, carbon tetrachloride, water and water/methane mixtures in carbons and oxides. The third project will be an examination of the importance of interpore correlation effects in inducing phase separation in small pore zeolites. 2. Selective adsorption of trace components in gas streams. Calculations will be made to elucidate the role of pore and system variables on the selective adsorption of trace contaminants in nitrogen and air streams for materials with pores of various geometries. The effect of the presence of water vapor on such selective adsorption on activated carbons will be studied to elucidate the mechanism for the large effects of humidity in industrial adsorption operations of this kind. The goal of this work is to develop methods for designing improved adsorbents for removal of trac e contaminants. 3. Diffusion in pores. Nonequilibrium molecular dynamics methods will be used to study mutual diffusion in mixtures in pores. The goal of this work will be to develop an understanding of the role of fluid-wall interactions, pore shape and size, and pore entrance effects on diffusion in real nanoporous materials.

9602960 Gubbins This Americas Program award will support a collaborative research project between Dr. Keith E. Gubbins, Cornell University and Dr. Erich Mueller, Universidad Simon Bolivar, Caracas, Venezuela. They will study the equilibrium and dynamic behavior of water and aqueous solutions when confined within the narrow pores of activated carbons. The objectives of the work are to determine the effects of confinement on the adsorption behavior of pure water, water/hydrocarbon and water/carboxilyc acid mixtures, and investigate the dynamic behavior and diffusion rates in the pores. Methods to be used will include Grand Canonical Monte Carlo and equilibrium and nonequilibrium Molecular Dynamics simulation. Comparisons of results from both methods will clarify the poorly understood confinement effects in these systems. A general aim of this research is to suggest new and optimal designs for adsorbents and adsorption processes for use in the oil and petrochemical industry, and for the removal of pollutants from air and water streams. ***

ABSTRACT CTS-9813499 Keith E. Gubbins/N. C. St. U. Partial support is provided for chemical engineering participants Liblice Conference on the Statistical Mechanics of Liquids, to be held at Zelena Ruda, Czech Republic on June 7-12, 1998. The Czech Academy of Sciences is organizing and hosting the conference, and will cover all local costs within the Czech Republic. Unique features of the conference will include: (a) coverage of the most recent molecular methods and results for complex liquids and interfaces, including ionic and associated liquids, colloids and micellar solutions, self-assembly, aqueous solutions, surfactants and adsorbents, glasses, polymers, phase equilibria, and confined nanofluids, (b) latest developments in advanced molecular simulation techniques, including parallel and distributed systems, (c) coverage of both applied and basic aspects, and (d) an opportunity for U. S. researchers to become familiar with leading research in this area by groups from East and West Europe, Japan and Australia. The invited speakers will include many of the international experts from these counties. Previous conferences were held in 1983, 1986, 1990 and 1994. ***

The aim of this project is to carry out a study to determine the effects of confinement in porous media on chemical reactions. Although there has been much progress in understanding the effects of confinement in porous media on physical properties, there has been no fundamental theoretical or molecular simulation work on chemical effects, particularly on chemical reaction equilibrium. Direct experimental investigations are complicated by difficulties in measuring compositions in the confined phase and in differentiating equilibrium from rate limitations. Confinement may have a substantial effect on the yields of reactions in which there is a net change in the number of moles because of increased density in pore volume or strong selectivity effects near the pore walls; molecular orientation may also play a role. However, the magnitude of these effects is currently unknown. A goal is to elucidate the fundamental principles that underlie confinement effects on chemical equilibrium. The reactions chosen for study are the nitric oxide dimerization reaction and the reduction of nitric oxide to nitrogen and oxygen. These reactions will be carried out in activated carbons and in carbon nanotubes. Reactive canonical Monte Carlo simulations will be performed to investigate the effects of pore size, pore shape, temperature, and pressure on the reaction yield, composition profiles and heats of reaction. Porous materials are widely used in chemical, oil, gas, and pharmaceutical industries as catalysts and in chemical processes such as adsorption separations, drying, and removal of pollutants from gas and liquid streams; the fundamental principals determined in this study may have application in these areas.

ABSTRACT
CTS-9908535
Gubbins, K./N. C. State

Activated carbons are the most widely used of all industrial adsorbents. They have two main advantages: (a) they are cheap, since they are made from readily available materials (wood, lignite, etc.), (b) they adsorb a wide range of fluids and materials very strongly, and are highly selective. The latter property derives from the fact that the carbon atoms are very high.

Despite these advantages, activated carbons have proved very difficult to characterize because of their complex and amorphous structure. In general they possess both micropores (less than 2 nm in width) and also some mesopores (larger than 2 nm) linked in a complex pore structure. Some information on this structure can be obtained from small angle x-ray or neutron scattering (SAXS and SANS), and from high resolution
transmission electron microscopy (HRTEM). However, the picture of the structure is incomplete from experiment. A realistic structural model of the carbon, at the molecular level, is needed in order to interpret other experiment on these materials, to determine pore size distributions, and to predict selective adsorption and pore phase transitions for the wide range of chemical systems used in industry. The current models used for this
purpose (arrays of independent slit pores) are known to be much over simplified, and are too crude for industrial needs.

We have recently developed protocols based on molecular simulation to construct much more realistic models of carbons at the atomic level. These are based on Reverse Monte Carlo, which matches the structure of the model to the structure factor (SAXS or SANS) and HRTEM data from experiment. The resulting models agree well with other experimental measures of the carbons, and there is good reason to believe that they are quite accurate representations of the real materials, A long range goal is to use these simulation methods to construct a data bank of materials which could be used to match data for particular industrial carbons. Such a data bank can be used for characterization of a wide range of carbons, and subsequent prediction of their adsorption and separation behavior.


Most of the expertise for synthesizing these carbons, and in addition most of the characterization and adsorption data, resides in industry. We need access to samples of these materials, and particularly advice on future directions for the modeling, in order to ensure that our research follows directions that are most relevant and useful for industry. Westvaco is a major world producer of these carbons. Westvaco's Charleston Technical Center has a number of leading experts in synthesis and characterization of activated carbons, particularly:

Dr. Jacek Jagiello, Research Chemist

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This three-year award for U.S.-France cooperative research involves Keith E. Gubbins of North Carolina State University and Roland J.-M. Pellenq of the Centre de Recherche sur la Matiere Divisee in Orleans, France for studies of disordered porous materials, in particular, glasses and carbons. These materials are widely used in the chemical, oil and gas and pharmaceutical industries as adsorbents for chromatography and as catalysts and catalyst supports. The collaboration addresses the development of realistic atomistic models to better characterize porous materials and to study phase changes and adsorption. The investigators will use molecular simulation techniques combined with experimental studies of the structure of these materials. The US investigator brings to this collaboration expertise in applying molecular simulation methods to porous solids. This is complemented by French expertise in experimental structure measurements and reconstruction methods.

This award represents the US side of a joint proposal to the NSF and the French National Center for Scientific Research (CNRS). NSF will cover travel funds and living expenses for the US investigator, postdoctoral researcher and graduate student. The CNRS will support the visits of French researchers to the United States. The collaboration will advance understanding of adsorption in disordered materials.

The self-assembly of nanostructures on surfaces and in porous media has been studied extensively by experiment, and is of interest in a wide range of applications, including optical and biological sensors, lithography, fabrication of nano-scale devices, and biomimetic materials. Despite this wide interest, the few attempts to develop theories and simulation methods for these systems give a poor account of the formation of the nano-structures and the effects of major variables (surfactant architecture, nature of surface, temperature, concentration, etc.) on them; some trends (e.g. temperature dependence) are predicted to be the opposite of those found experimentally.

The aim of this project is to carry out a one year feasibility study to develop and evaluate a new multi-scale molecular simulation strategy to predict the equilibrium behavior of nano-structures formed from non-ionic surfactants on planar surfaces and in nano-pores. The simulations will cover size ranges from sub-Angstrom to hundreds of nanometers by using a combination of ab initio, atomistic simulation, and discretized lattice Monte Carlo simulation methods. By optimizing the lattice discretization and intermolecular potentials, the PI hopes to develop an approach that can predict not only the nanostructures that form, but the influence of temperature, composition, solvent, surfactant architecture, nature of the solid surface, and morphology of the pore structure, on the self-assembled structures. The challenge will be to include a sufficient level of molecular detail and sophistication in the model, while preserving sufficient simplicity that calculations can be made in a reasonable time on current computers.

The feasibility of the method will be evaluated by comparison with experimental data. Criteria for success will include (a) correct prediction of qualitative trends of property behavior (adsorption, structures, aggregate size, heats) with variation in temperature, concentration, type of surface, etc., (b) quantitative agreement with experiment, and (c) computational burden of the calculations.

0335118
Gubbins
This award supports faculty from several disciplines and several US universities to participate in a workshop on organizing an international graduate program to be held at the Fritz Haber Institute in Berlin, Germany on 10-13 June 2003. The workshop will focus on developing a program between North Carolina State and Vanderbilt Universities on the US side and the Technical University of Berlin, the Max Planck Institute for Colloid and Interface Science, and the Fritz Haber Institute in Berlin. The fields of study for the international graduate program will be self-assembled nanostructures, including surfactant self-assembled structures on solids and in pores, thin films on metals and semiconductors, and biological membranes. As part of the program, US graduate students will spend part of their PhD tenure in one or more of the Berlin institutions (typically for a period of 6 months or more). Workshop participants will be drawn from the fields of chemistry, physics, biochemistry, materials science, and chemical engineering.

0329695
Gubbins
This award supports the PI and several graduate, undergraduate, and postdoctoral students from North Carolina State University in a collaboration withMartin Schoen, Gerhard Findenegg, and Sabine Klapp of the Physics Department at the Technical University of Berlin, Germany. The research will focus on the self-assembly of surfactants on solid surfaces and in nano-porous solids. Such self-assembly processes are as yet only poorly understood, but are crucial in applications ranging from sensors, thin-film technologies, lithographic processes, electronic devices , and sol-gel nano-coatings to biomimetic materials. They are also of great fundamental interest, since many unique features of the self-assembly are as yet unexplained. The phenomena of interest spans a range of length scales from the atomic to the microscopic and of time scales from picoseconds to microseconds, so that new simulation methodology or theoretical techniques are required to study the systems successfully. The project combines the expertise in experimental and dynamical simulation studies of surfactant self-assembly of the Berlin group with the extensive experience of the NC State group in equilibrium properties of host phases confined within nano-porous materials.

The broader impacts of this collaboration are that it increases interactions between US researchers and those in Germany, it promotes collaborative opportunities and career development for US students, and it enhances the infrastructure for research and education by laying the groundwork for future international research and education opportunities.

Gubbins, Keith E. / Glotzer, Sharon C.
North Carolina State University / University of Michigan

"NIRT: Surfactant Self-Assembly on Nano-Structured Surfaces: Multi-Scale Computational Prediction and Design"

This proposal is for a collaborative research program on multi-scale computational prediction and design of nano-structures formed by self-assembly of surfactants from aqueous solution onto solid surfaces and nano-porous media. Such processes are ubiquitous throughout nanoscale science, and the resulting structures have potential applications in enhanced and selective separations, as nanosensors, biosensors, bioelectronic materials, and as electronic devices. Despite widespread interest in these structures, the underlying principles governing their formation, structure and properties are poorly understood. Theoretical treatments are lacking, because the pertinent length and time scales span many orders of magnitude, from Angstroms to tens of microns, and femtoseconds to hundreds of microseconds.

This project draws on the expertise of PIs and Co-PIs drawn from the fields of Chemical Engineering (K.E. Gubbins, NC State University and S.C. Glotzer, University of Michigan), Physics (J. Bernholc, NC State University), and Materials Science and Engineering (D.W. Brenner, NC State University). In addition, three additional investigators (whose research is fully funded by DFG in Germany) will be involved from the Stranski Institute of Physical Chemistry, Technical University of Berlin (TU-B); G.H. Findenegg, Professor of Physical Chemistry and Director of the Institute; M. Schoen, Professor of Theoretical Chemistry; and S. Klapp, Head of Junior Group. A multi-scale simulation scheme will be developed involving electronic, atomistic and meso-scale simulation methodologies. Methods for bridging these scales will be developed and tested, and then applied to study non-ionic and ionic surfactants self-assembling on non-porous carbons, carbon nanotubes, fullerenes, and mesoporous silicas. These methods will be used to investigate the factors determining structure and the relationship between structures and properties, including electrical and electronic properties, sensor activity, selective adsorption from mixtures, the mechanism for solvation of carbon nanotubes, and nanofluidics.

Among the broader aspects of the project will be a strong international component through our collaboration with TU-B, which will include opportunities for graduate students and postdoctoral workers to visit and work with our Berlin collaborators; students will have the opportunity to develop expertise in theoretical and simulation methodologies suited to a wide range of spatial and temporal scales, with emphasis on applications to nanoscience and nanotechnology. It is anticipated that the advanced computational methods developed in this project will be useful in other applications within nanotechnology. A graduate course on Computational Nanoscience of Soft Matter will be developed jointly by UM, NCSU and TU-B, and will be available to students via video-conference link; short courses on specialized topics in simulation methodology will be available to students through the High Performance Simulation Center at NCSU. Outreach activities will include tutorials by project faculty for high school students, undergraduates, industrial researchers, and senior citizens; an existing. nanotechnology tutorial, developed at NCSU, will be expanded to include multimedia presentations and video streamed seminars, and will be available to the general public via the group's websites. Under-represented minorities will be recruited through NCSU's close ties with Meredith College (a women's college) and St. Augustine's University (a HBU), through NCSU's Women in Science and Engineering program (first year undergraduates), and through UM's University research Opportunities Program.

The primary research theme of this proposal is Multi-Scale Multi-Phenomena Theory, Modeling and Simulation at the Nanoscale. A second theme is Nanoscale Structures, Novel Phenomena, and Quantum Control.

This award supports the PI and several graduate, undergraduate, and postdoctoral students from North Carolina State University in a collaboration withMartin Schoen, Gerhard Findenegg, and Sabine Klapp of the Physics Department at the Technical University of Berlin, Germany. The research will focus on the self-assembly of surfactants on solid surfaces and in nano-porous solids. Such self-assembly processes are as yet only poorly understood, but are crucial in applications ranging from sensors, thin-film technologies, lithographic processes, electronic devices , and sol-gel nano-coatings to biomimetic materials. They are also of great fundamental interest, since many unique features of the self-assembly are as yet unexplained. The phenomena of interest spans a range of length scales from the atomic to the microscopic and of time scales from picoseconds to microseconds, so that new simulation methodology or theoretical techniques are required to study the systems successfully. The project combines the expertise in experimental and dynamical simulation studies of surfactant self-assembly of the Berlin group with the extensive experience of the NC State group in equilibrium properties of host phases confined within nano-porous materials.

The broader impacts of this collaboration are that it increases interactions between US researchers and those in Germany, it promotes collaborative opportunities and career development for US students, and it enhances the infrastructure for research and education by laying the groundwork for future international research and education opportunities.

Project Abstract

GOALI: Molecular Modeling of Confined Nano-Phases and Novel Nano-Porous Materials (CTS-0626031)

Keith Gubbins, North Carolina State Univ.; Matthias Thommes, Quantachrome, Instruments, Inc.

This is a GOALI project involving university-industry collaboration between researchers at North Carolina State University (NCSU) and at Quantachrome Instruments, a leading maker of instruments for characterizing nano-structured materials. The aim of this project is to develop and apply atomistic simulation methods to obtain realistic atomic models of several new classes of synthetic nanoporous materials, and to use these to investigate confined phases within these materials and to assist in optimization of the materials for specific applications. The materials to be studied are templated mesoporous silicas, and the recently reported mesoporous carbons (CMKs), carbide-derived carbons and periodic mesoporous organosilicas (PMOs). These materials hold great promise for applications in microelectronics (mesoporous silicas), as electrodes in fuel cells, batteries and supercapacitors (mesoporous carbons, carbide-derived carbons), hydrogen storage (carbide-derived carbons), as catalytic and chromatographic supports (organosilicas), as sensors and in environmental remediation (organosilicas). Accurate and realistic atomic models of these materials are essential to the development of optimal material designs for these applications. Preparation of these materials and experimental studies of adsorption on them will be performed by researchers at Quantachrome Instruments, and this data will be provided to the NCSU researchers. Quantachrome scientists will also offer advice on directions for the modeling work carried out at NCSU. The NCSU researchers have already developed realistic models of templated mesoporous silica materials, which form the starting point in the synthesis of mesoporous carbons, and will develop Monte Carlo (MC) simulation methods that mimic the synthesis of these carbons within the silica, followed by silica removal and relaxation. Both lattice and off-lattice MC methods will be developed to model the organosilicas. MC and molecular dynamics simulations will be carried out to study adsorption and diffusion in these materials.

Intellectual Merit. Because these novel materials are not crystalline, a combination of atomistic simulation and experiment provides the best route to developing realistic atomic models of them. Existing models of such materials assume over-simplified pore geometries (slit or cylinder shaped) and are inadequate for predicting the behavior of adsorbed phases. The realistic models that are being developed will make possible fundamental investigations of the influence of confinement and nature of the material on adsorption, phase changes, reactions and diffusion. PMOs offer the possibility to tune the chemistry of the pore walls to obtain a range of interactions from hydrophilic to hydrophobic, while the CMKs combine desirable features of carbons (conductivity, mechanical and thermal stability) with those of silicas (large pores, regular pore structure).
Broader Impact. Improved understanding of the behavior of nano-phases confined within these novel nano-porous materials will impact a broad range of technologies, and is essential to the design of new biological and chemical sensors, nano-reactors, hydrogen storage media, electrodes for fuel cells and batteries, and nano-structured catalysts. Graduate and undergraduate students working on this project will learn modern multi-scale modeling methods, and will gain experience of international cooperative research through our active collaborations in this area with researchers in France, Germany, Poland, China and Hong Kong. Graduate students from under-represented groups will be recruited from colleges and universities in North Carolina with whom NCSU has established ties and programs.

Proposal Number: CBET- 0741367
Principal Investigator: Keith Gubbins
University: North Carolina State University

Title: Group Travel: Workshop on "Interfacial Phenomena and Advanced Materials", to be held in Gdansk, Poland on June 4-6, 2008

This project provides travel support for U.S. participants to attend a 3 day Workshop on "Interfacial Phenomena and Advanced Materials", to be held in Gdansk, Poland on June 4-6, 2008. The purpose of the Workshop is to encourage closer scientific contacts and long term research collaboration between researchers in this area between the U.S. and Poland. The Workshop will involve 15 U.S. participants and approximately 15 from Poland, with a balance between junior, mid-career and senior researchers, and between experiment and theory, with similar or complementary interests on the two sides. In addition, young researchers in these areas from Poland will attend the meeting, present poster papers, and interact with the more senior participants throughout the meeting. Approximately three of the USA participants will be provided additional travel funds to visit a Polish workshop participant in Poland in order to develop the collaborative research projects they will initiate at the workshop.

Intellectual merit. The topic of the Workshop will represent cutting edge research in the areas of soft and hard materials, bio-materials, polymers, self-assembled materials, complex fluids, surface science, colloids, adsorption, catalysis, and computational nanoscience. The participants are leading researchers in these areas, and the objective is to provide a survey of current research in these areas and to explore fruitful future possibilities for research collaboration.

Broader impact. The international workshop is expected to initiate individual and institutional collaboration among the participants. A previous workshop on "Nanoscience and Nano-Structured Materials" held in Poznan, Poland in June 2006 proved highly successful and led to numerous research contacts and collaborations between U.S. and Polish participants, and it is anticipated that this workshop will be equally successful in this regard. The participation of a substantial number of young Polish researchers at the Workshop will offer the U.S. participants a much broader view of research in this area in Poland, and it is expected that this may lead to future visits to U.S. laboratories by some of these young workers. U.S. participants will visit other institutions in Poland after the Workshop, to learn more about research activities and to explore further possibilities for research cooperation between the two countries. Such research cooperation will enrich the research and education infrastructure of both countries.

CBET-0754979
Gubbins

This NSF award by the Chemical and Biological Separations program supports work by Professors Teresa J. Bandosz and Keith E. Gubbins at CUNY City College and North Carolina State University, respectively, to investigate and design novel reactive adsorbents for the removal of toxic gases. Growing concerns about the environment and terrorist attacks prompt a search for effective adsorbents for removal of small molecule toxic gases, such as ammonia, hydrogen sulfide, sulfur dioxide, and carbon monoxide. These are usually to be removed under ambient conditions in the presence of moisture, conditions where physical adsorption forces are weak.

In the research program proposed here we will use a combined experimental and theoretical approach to explore toxic gas removal using reactive adsorption, by designing graphite oxide materials with functional surface groups that are optimal for removal of these gases. The experimental work will be carried out at CUNY City College, and the theoretical program at North Carolina State University. We seek to determine the fundamental mechanism, at the atomic and electronic levels, of reactive adsorption/intercalation of small molecule toxic gases on these materials. The graphite oxides will be synthesized and modified to achieve suitable microporosity and reactive/catalytic surface properties. The fundamental theoretical studies will guide the synthesis of materials with appropriate pore structures and surface functionalilties. In return, the experimental findings will suggest new directions of enquiry for the theoretical studies. Studies will be made both in the absence and presence of water, thus mimicking practical conditions in industry.
This will be the first concerted combined experimental and theoretical investigation of these systems. The research is expected to lead to improved functionalized adsorbents, which may find application in other scientific challenges where the separation of reactive molecules is involved. In addition to developing experimental and theoretical algorithms to design effective adsorbents, the results may find wide applications in air cleaning, energy storage, and fuel cell technology. The materials developed may also find application as gas sensors. Changes in electrical conductivity due to the presence of such small molecules intercalated within the graphite interlayer space can be used to detect toxic gases at low concentrations.

Two graduate students (one at CCNY and one at NCSU) and one undergraduate student (CCNY) will work on the project. Since CCNY is a minority serving institution there is a high probability that students from underrepresented groups will be involved in the research, which will have a positive effect on development of environmental awareness in the minority group. Other important educational aspects are the development of new environmental chemistry experiments by the undergraduate student involved in the research (independent research undergraduate project), and the development of new theoretical methods for the surface characterization of functionalized materials and for reaction with diffusion in nano-structured materials.

Keith Gubbins of North Carolina State University and Liping Huang of Rensselaer Polytechnic Institute are receiving an award from the Theory, Models and Computational Methods program of the Chemistry Division. The project goal is the development and application of novel simulation methods for the discovery of confinement and surface effects on heterogeneous reactions with diffusion in nano-porous materials. The focus of the study is to provide a molecular level understanding of the mechanisms of adsorption, diffusion and reaction as well as the interplay among them. To that end, a suite of methods spanning the electronic, atomistic and continuum scales are developed to treat simultaneously reaction, diffusion and adsorption. These methods are projected to combine density functional theory, time dependent density functional theory, advanced optimization techniques, non-equilibrium and rare event molecular dynamics, and continuum modeling, and are able to accommodate temperature and pressure gradients, thus simulating experimental conditions. Hence, the simulation strategy reuses existing codes within a novel multiscale approach.

The research is at the interface of chemistry and materials engineering research and design. Improved multiscale methods for studying chemical reactions under realistic conditions provide a route to deeper understanding of the roles of diffusion and adsorption in heterogeneous reactions. The ability to predict the combined effect of these phenomena impacts a broad range of technologies, and is essential to the design of new reactive schemes for reducing energy demand and environmental impact. Graduate and undergraduate students working on this project learn modern multiscale modeling methods, and gain experience of international cooperative research through active collaborations with researchers in Japan, Poland, China and Hong Kong. Graduate students from under-represented groups are recruited through a bridging program and an existing AGEP program with HBCUs in the area, and through NCSU's Women in Science & Engineering program. At RPI, Huang is actively participating in New Visions: Math, Engineering, Technology and Science, a high school outreach program that provides advanced placement courses for students at rural schools in upstate New York.

The award is co-funded by a pilot program of the Office of Cyberinfrastructure.

1133112/1133066
Bandosz/Gibbins

Activated carbons possess high surface area (typically 1,000-2,000 m2g-1) and are powerful physical adsorbents, but have little catalytic activity except at high temperatures. Metal-organic framework (MOF) materials are generally effective catalysts, but are less effective as adsorbents. Recently, in a proof of concept, we have succeeded in synthesizing a GO/MOF nanocomposite material, and shown that it is very effective in removing toxic gases (ammonia, hydrogen sulfide) from gas streams through a combination of surface reaction and adsorption. The capacity of the nanocomposites to remove toxic gases significantly exceeds that of either the MOF or graphite oxide alone, and preliminary results for ammonia suggest that these nanocomposites can achieve a 300% or more increase in adsorption capacity over conventional activated carbons.

This project will be a joint experimental-theoretical study of such graphene/MOF and GO/MOF (collectively, G/MOF) nanocomposites, with the aim of determining their formation mechanism, atomic structure, pore structure and catalytic and adsorption properties, with the practical goal of designing materials with optimal adsorption and catalytic properties for the removal of toxic gases. As grapheme-based components graphite, graphite oxide and exfoliated graphite will be used. Syntheses will be followed by characterization. The interactions of NH3 and H2S, separately and mixed with methane, with the nanocomposites will then be investigated. These systems are chosen based on the properties and differences in the chemical nature of the adsorbates, the need for reactive adsorption under ambient conditions, and the potential detection capabilities of graphene-based nanocomposites. For the latter the changes in electrical conductivity can be employed. MOFs chosen for the study will include water stable materials with potentially active Cu, Cr and Fe sites, such as Cu-BT or MIL-100.

In parallel with the experimental program, dual scale theoretical studies using molecular simulation (Monte Carlo, Hybrid Reverse Monte Carlo and Molecular Dynamics) and (ab initio) density functional theory will be carried out to determine details of the atomic structure of the materials, the reaction mechanism, reactive adsorption capacity and heats of adsorption. These theoretical results will help direct the experimental program towards promising materials and conditions.

This research project will provide fundamental understanding of the relation between synthesis conditions, atomic structure and pore morphology, and separations performance for a new class of G/MOF nanocomposites that are designed for toxic gas removal. These novel materials may find application in other separations and in sensing devices. The broad spectrum of surface characterization and theoretical methods applied will lead to a better understanding of the surface chemistry of adsorbents and catalysts in general.

The research is directly relevant to developing new strategies to design effective materials for removal of toxic gases from air at ambient conditions through reactive adsorption. Another important technical aspect is the possibility of applications of these materials as gas sensors. If small molecule gases are intercalated within the graphite interlayer space the electrical conductivity is expected to change, and this phenomenon can be used to detect toxic gases at low concentration range. A preliminary exploratory study of ammonia on a GO/MOF nanocomposite showed an approximately threefold increase in adsorption capacity over conventional activated carbons. Thus, the proposed research is potentially transformative. The project will involve two graduate students, two undergraduate researchers and one high school student from an inner city science-oriented high school. CCNY is a minority serving institution, and the project would provide the possibility for a member of an under-represented group to perform research and to earn the Ph.D. NCSU?s AGEP/Opt-Ed and ORNL?s Research Alliance in Math and Science (RAMS) summer program will also provide opportunities to recruit students from under-represented populations. The whole education experience of the students will be based on the integration of research and education.

This program will provide a strong international experience for doctoral students at North Carolina State University and University of North Carolina at Chapel Hill, through collaborative research projects and teaching with institutions in and near Berlin, Germany. The research project will focus on interdisciplinary studies of self-assembly of molecules on solid surfaces to form nanostructures. The German institutions involved will be the Technical University of Berlin (the lead institution on the German side), Humboldt University and the Max Planck Institute of Colloid and Interface Science (Golm, Potsdam). The collaborative program will involve 13 faculty members in Germany, and 15 doctoral students there. On the U.S. side the project will involve 12 faculty at NCSU and UNC-Chapel Hill, and will support visits by 15 U.S. doctoral students to Berlin, where they will spend a part of their doctoral study period (a minimum of 11 weeks) working in the overseas partner institution. U.S IRES Fellows will have a U.S. advisor and a co-advisor in the partner institution in Germany, and will continue working on their research project after return to the U.S. The German doctoral students will spend a similar or longer amount of time working in the U.S. host institutions; funding for the visits by German students to the U.S. is available from a grant from the Graduate College program of the German Science Foundation (DFG). The educational program will include course modules in theory, experiment and technology of nanoscience taught by faculty on both sides and made available by video transmission. Regular IRES seminars, in which faculty, students and postdocs give short accounts of their latest results, will be broadcast synchronously as video conferences. There will be an annual meeting of the participants, including German colleagues (students and faculty), to discuss results and to assess the program. The plan described here is the result of workshops & discussions held by the participants in Berlin and Raleigh.
Intellectual Merit. The self-assembly of surface-active molecules to form various nano-scale structures on solid surfaces (micellar structures on surfaces and in pores, thin films, patterned films, nanoclusters, etc.) lies at the heart of many biological and physical processes, but the fundamental principles of how molecules self-assemble to form these structures are poorly understood, making it difficult to predict and design nano-structured devices. This graduate program will bring together many experts from diverse fields and institutions to develop a fundamental understanding of such processes.
Broader Impact. Improved understanding of directed self-assembly will impact many important technologies, including microelectronics, chemical and biological sensors, photonics, catalysis, drug delivery and medicine. The strong international aspects of the program address an important need in U.S. graduate education at a time of increasing globalization. We believe the international experience gained will have an important and lasting impact on the outlook and careers of the students. Recruitment of students from under-represented groups will be facilitated by our close contacts with North Carolina Central University (NCCU), a nearby (20 miles) HBCU, through coordination with NCSU?s AGEP/Opt-Ed program, and NCSU?s Women in Science & Engineering (WISE) program which is aimed at encouraging women to enter this field. Prior to departure the U.S. students will network with the visiting German students and will be encouraged to take the German for Graduate Students course offered at NCSU. Students whose research is in appropriate areas will have access in Berlin to the North German supercomputer network (at Konrad-Zuse-Institut, Berlin), and to the national synchrotron source BESSY, located at the Helmholtz-Zentrum in Berlin.

This project is supported by NSF's Office of International Science and Engineering (OISE) and the NSF Directorate of Engineering (ENG), Division of Chemical, Bioengineering, Environmental, and Transport Systems (CBET).

Abstract
1160515
Gubbins, Keith E.

This GOALI project involves university-industry collaboration between researchers at North Carolina State University (NCSU) and at Quantachrome Instruments, a leading maker of instruments for characterizing nano-structured materials. The aim of this project is to investigate the effects of confinement in nanoporous materials on pressure enhancement, diffusion, phase changes and supercapacitor performance, using realistic atomistic models of the materials. Fundamental understanding of these effects will assist in optimization of the materials for specific applications. The materials to be studied are carbide-derived carbons, mesoporous carbons and oxides, and hierarchical carbons and oxides. Applications of particular interest are the use of these materials for diffusional separations, chemical reactions and supercapacitors.

This project will involve cooperative research with researchers in Zhejiang University in Hangzhou (Professors Wang Qi and Liu Ying-Chun and coworkers) in China on diffusion in nanopores; the University of Hong Kong (Professor Kwong-Yu Chan and coworkers) on carbon-based supercapacitors; and Shinshu University (Professor Katsumi Kaneko) on pressure enhancement effects.

Preparation of these materials and experimental studies of structure and adsorption on them will be performed by researchers at Quantachrome Instruments and University of Hong Kong, and this data will be provided to the NCSU researchers. Quantachrome scientists will also offer advice on directions for the modeling work carried out at NCSU. The NCSU researchers will develop and test new simulation methodologies to model these materials and study effects of confinement on the properties of confined nano-phases. In particular, Monte Carlo and molecular dynamics simulations will be carried out to study adsorption, pressure enhancement and diffusion in these materials. In the case of the carbon materials, molecular simulations will be carried out to determine their use as supercapacitors, including studies of capacitance, power density and diffusion in the pore structures, with the aim of understanding the influence of pore design on performance.

Intellectual Merit. The realistic models that are being developed in this work will make possible fundamental investigations of the influence of confinement and nature of the material on adsorption, phase changes, diffusion, reactions and electrode performance. Recently, we have demonstrated that very high pressures (tens of thousands of bars) exist in confined nanophases within carbons and silicas, and studies of this effect are expected to
provide new insight into many confinement effects.

Broader Impact. Improved understanding of the behavior of nano-phases confined within these novel nano-porous materials will impact a broad range of technologies, and is essential to the design of new biological and chemical sensors, nano-reactors, energy storage media, electrodes for fuel cells and supercapacitors, and nano-structured catalysts. The graduate students working on this project will learn modern multi-scale modeling methods, and will gain experience of international cooperative research through our active collaborations in this area with the researchers in China, Hong Kong and Japan.

Proposal Number: 1603851, Gubbins
Enhanced solubility in nanoporous media and its role in adsorption separations

When gases or liquids are adsorbed into porous materials, such as activated carbon and silica, the fluid confined within the narrow pores often displays properties that are very different from those in the bulk gas or liquid. These differences are exploited in many practical applications, including industrial separation of chemicals, and in daily life in the purification of water and air. Much research has been reported on the effects of such confinement in a nanoporous solid on vapor-liquid and liquid-solid phase separations for pure substances, and the effects are found to be large. However, little is known of the effects of such confinement on the solubility of sparingly soluble solutes in liquid solvents. Knowledge of these confinement effects on solubility are important in many applications, including industrial adsorption separations, oil and gas exploration, hydraulic fracturing, geological carbon dioxide sequestration, the behavior of toxic gases and chemicals in soils, dissolved gases in fuel cells and in drug delivery.

In this project molecular simulation and modeling will be used to investigate the effects of confinement within porous materials on the solubility of sparingly soluble substances in water and in liquid hydrocarbons. An important aspect will be the development and testing of molecular theory for solvents that exhibit strong molecular association or Coulombic interactions; this will be of particular significance for water and aqueous electrolytes. The initial work will involve a broad study for simple systems in which the pores are of simple geometry and fluid molecules are non-polar, that will provide a fundamental understanding of the influence of the materials and other variables on the solubility. This will be carried out using advanced molecular simulation methods (Monte Carlo and molecular dynamics), and will explore effects of temperature, pressure, chemical composition, pore size and shape. In addition a density functional theory will be developed for highly polar and associating molecules for the first time. This latter part of the work will be carried out in collaboration with researchers at the East China University of Science and Technology in Shanghai. In addition, further and more detailed studies will be made for specific systems of direct interest in industrial adsorption separations, enhanced oil and gas recovery and carbon dioxide sequestration. While the research under the grant will be primarily theoretical (molecular simulation and classical density functional theory studies), the team will also collaborate with three international research groups in the U.K., Poland and Germany, carrying out experiments in this area. The development of density functional theory for water and aqueous solutions is expected to impact many fields. One graduate student and one undergraduate will be involved in this research, and will receive training in advanced simulation and theory methods, and gain experience of international research collaboration.