The Experts below are selected from a list of 2739 Experts worldwide ranked by ideXlab platform
William R Smith - One of the best experts on this subject based on the ideXlab platform.
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molecular simulation of Chemical Reaction Equilibria by kinetic monte carlo
Molecular Physics, 2019Co-Authors: Braden D Kelly, William R SmithAbstract:We describe a new algorithm for the molecular simulation of Chemical Reaction Equilibria, which we call the Reactive Kinetic Monte Carlo (ReKMC) algorithm. It is based on the use of the equilibrium...
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an efficient molecular simulation methodology for Chemical Reaction Equilibria in electrolyte solutions application to co2 reactive absorption
Journal of Physical Chemistry A, 2019Co-Authors: Javad Noroozi, William R SmithAbstract:We develop a computationally efficient molecular-based simulation algorithm for Chemical Reaction Equilibria in liquids containing neutral and ionic species, which is based on the combination of classical force field and ab initio calculations and permits calculations involving very small species concentrations. We show its application to the reactive absorption of CO2 in aqueous monoethanolamine (MEA) solvent as a benchmark case, the first time that a quantitatively accurate predictive approach requiring no experimental data has been successfully applied to calculate all solution species concentrations for this system, including the partial pressure of CO2 above the solution. The Reaction Ensemble Monte Carlo (REMC) algorithm, the only other generally applicable approach, requires special system-dependent Monte Carlo enhancements for its implementation, and to detect species with very small concentrations requires long simulation times and/or large system sizes. In contrast, the proposed algorithm can be straightforwardly implemented for systems of any molecular complexity using a standard Molecular Dynamics (MD) simulation package capable of calculating free energy changes and can calculate small species concentrations with normal simulation times and system sizes. In addition, the inherent parallelization capability of MD (which is problematic for MC-based approaches) enables the algorithm's computationally efficient implementation. The H2O-MEA-CO2 benchmark system has been the subject of many previous studies based on macroscopic thermodynamic modeling, which primarily involves fitting their parameters (of which Reaction p K values are the most important) to experimental data measurements. To make contact with such approaches, we show the translation of the molecular-based quantities to the direct prediction of these parameters and calculate Reaction equilibrium in the framework of a Henry Law-based Chemical potential model. We consider both the ideal solution form and its extension using the Davies equation for the species activity coefficients. We study a range of temperatures and CO2 solution loadings in a 30 wt % MEA solution and incorporate an uncertainty analysis in our methodology. We find that the uncertainties of the simulated solution species compositions are comparable to those of the available experimental data. We report predictions of minor species compositions of very small magnitude, for which experimental measurements are typically extremely challenging.
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simulation of Chemical Reaction Equilibria by the Reaction ensemble monte carlo method a review
ChemInform, 2008Co-Authors: Heath C Turner, William R Smith, John K Brennan, Martin Lisal, Karl J Johnson, Keith E GubbinsAbstract:Understanding and predicting the equilibrium behaviour of Chemically reacting systems in highly non-ideal environments is critical to many fields of science and technology, including solvation, nanoporous materials, catalyst design, combustion and propulsion science, shock physics and many more. A method with recent success in predicting the equilibrium behaviour of Reactions under non-ideal conditions is the Reaction ensemble Monte Carlo method (RxMC). RxMC has been applied to Reactions confined in porous solids or near solid surfaces, Reactions at high temperature and/or high pressure, Reactions in solution and at phase interfaces. The only required information is a description of the intermolecular forces among the system molecules and standard free-energy data for the reacting components. Extensions of the original method include its combination with algorithms for systems involving phase Equilibria, constant-enthalpy and constant-internal energy adiabatic conditions, a method to include Reaction kine...
Keith E Gubbins - One of the best experts on this subject based on the ideXlab platform.
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simulation of Chemical Reaction Equilibria by the Reaction ensemble monte carlo method a review
ChemInform, 2008Co-Authors: Heath C Turner, William R Smith, John K Brennan, Martin Lisal, Karl J Johnson, Keith E GubbinsAbstract:Understanding and predicting the equilibrium behaviour of Chemically reacting systems in highly non-ideal environments is critical to many fields of science and technology, including solvation, nanoporous materials, catalyst design, combustion and propulsion science, shock physics and many more. A method with recent success in predicting the equilibrium behaviour of Reactions under non-ideal conditions is the Reaction ensemble Monte Carlo method (RxMC). RxMC has been applied to Reactions confined in porous solids or near solid surfaces, Reactions at high temperature and/or high pressure, Reactions in solution and at phase interfaces. The only required information is a description of the intermolecular forces among the system molecules and standard free-energy data for the reacting components. Extensions of the original method include its combination with algorithms for systems involving phase Equilibria, constant-enthalpy and constant-internal energy adiabatic conditions, a method to include Reaction kine...
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simulation of Chemical Reaction Equilibria and kinetics in heterogeneous carbon micropores
Applied Surface Science, 2002Co-Authors: Heath C Turner, John K Brennan, Jorge Pikunic, Keith E GubbinsAbstract:Abstract We present a simulation study which shows how the equilibrium yield and kinetics of Chemical Reactions can be enhanced by tailoring the structure and surface chemistry of the catalyst support material. Equilibrium results are presented for the ammonia synthesis Reaction, N 2 +3H 2 ↔2NH 3 , occurring within various carbon supports, representing a range of Chemical and physical surface heterogeneity. Using a simulation technique known as Reactive Monte Carlo (RxMC), we find that surface activation and pore width are primary factors in determining the conversion of the ammonia synthesis Reaction while effects of surface corrugation are small. We probe the kinetic effects of physical confinement within microporous carbons by studying the bimolecular hydrogen iodide decomposition Reaction, 2HI→H 2 +I 2 , in carbon slit-pores and nanotubes. The rate constant of this Reaction is measured by combining the quasi-equilibrium hypothesis of transition-state theory (TST) with the RxMC simulation technique. The kinetic simulations represent a new method for probing Reaction kinetics in non-ideal environments and show accurate results when applied to the hydrogen iodide decomposition Reaction.
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influence of Chemical and physical surface heterogeneity on Chemical Reaction Equilibria in carbon micropores
Molecular Physics, 2001Co-Authors: Heath C Turner, Jorge Pikunic, Keith E GubbinsAbstract:Recent simulation results are presented for the equilibrium yield of the ammonia synthesis Reaction in various model microporous carbons. It is found that the Reaction Equilibria within the micropores is affected by many factors, including pore size, pore shape, connectivity, surface roughness, and surface Chemical activation. In order to probe these effects, reactive Monte Carlo simulations of the Reaction were performed in several microporous carbon models: smooth slit-shaped carbon pores, a realistic carbon model generated from experimental diffraction data, single-walled carbon nanotubes, and smooth slit-shaped pores activated by carboxyl surface groups. The simulations show that the ammonia conversion is most sensitive to the carbon pore width and to the amount of surface Chemical activation. Effects of surface corrugation and pore connectivity on the equilibrium Reaction yield are minimal.
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effect of confinement on Chemical Reaction Equilibria the Reactions 2no no 2 and n2 3h2 2nh3 in carbon micropores
Journal of Chemical Physics, 2001Co-Authors: Heath C Turner, Karl J Johnson, Keith E GubbinsAbstract:We report reactive Monte Carlo (RMC) simulations of Reaction Equilibria for both the nitric oxide dimerization and the ammonia synthesis Reactions. We have applied the RMC technique to both a single bulk phase and also to a two-phase system, composed of the bulk gas and a slit-shaped pore, with pore parameters chosen to model activated carbon fibers. We achieve close agreement with the experimentally measured conversions of nitric oxide and ammonia in the bulk phase. Both Reactions involve a stoichiometric decrease in mole number, which should cause the yield of each to be enhanced by the increased density within the pore phase. We show that the effect of confinement on the yield of both Reactions is significant, and is particularly dramatic for the nitric oxide Reaction; in addition, the ammonia synthesis Reaction is affected by the selective adsorption of nitrogen over hydrogen in the pore under certain conditions.
Gerd Maurer - One of the best experts on this subject based on the ideXlab platform.
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reprint of quantitative nmr spectroscopy of binary liquid mixtures aldehyde alcohol part ii propanal or butanal or heptanal methanol or ethanol or 1 propanol
The Journal of Chemical Thermodynamics, 2013Co-Authors: Silke Jaubert, Gerd MaurerAbstract:Abstract The Chemical Reactions of aldehydes with alcohols to (hemiacetals and poly(oxymethylene) hemiacetals) have an essential influence on the thermodynamic properties and related phenomena like, for example, the vapor + liquid phase equilibrium of such liquid mixtures. This is well known in the literature for systems such as, for example, formaldehyde and methanol. Experimental information on the Chemical Reaction Equilibria in mixtures with aldehydes other than formaldehyde and alcohols is extremely scarce. Therefore, in the first part of this series, quantitative NMR spectroscopy was used to investigate the Chemical Reaction equilibrium in binary liquid mixtures of acetaldehyde and an alcohol (methanol or ethanol or 1-propanol) at temperatures between (255 and 295) K. That work is here extended to three other aldehydes, viz. (1-propanal, 1-butanal and 1-heptanal). The results confirm the expectations from the first part of this series, i.e., that the majority of the constituents of the mixture is present as hemiacetal and the first two poly(oxymethylene) hemiacetals. For example, in an equimolar liquid mixture of {1-heptanal + methanol (or + ethanol or + 1-propanol)} at T = 273 K about 88% (or 81% for both other alcohols) of the aldehyde is bound to hemiacetal and the first two poly(oxymethylene) hemiacetals, i.e., the conversion rates are nearly the same as in the previous investigations with acetaldehyde instead of 1-heptanal. In the series investigated of combinations of aldehydes and alcohols, the particular aldehyde has only a small influence on the conversion rate. In the series of alcohols investigated only methanol has a somewhat larger influence whereas the results (speciation and conversion) for ethanol and 1-propanol are very similar. The NMR-spectroscopic results were also evaluated to determine the mole-fraction based Chemical Reaction equilibrium constants for the formation of the hemiacetals and the first two poly(oxymethylene) hemiacetals and the Chemical Reaction enthalpies.
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new experimental results for the vapor liquid equilibrium of the binary system trioxane water and the ternary system formaldehyde trioxane water
Journal of Chemical & Engineering Data, 2005Co-Authors: Michael Albert, Hans Hasse, Christian Kuhnert, Gerd MaurerAbstract:New experimental results for the vapor−liquid equilibrium of the binary system (trioxane + water) at 393 K and 413 K and the ternary system (formaldehyde + trioxane + water) at 413 K and around 450 kPa are reported and compared with predictions/correlations using a physicoChemical model combining the UNIFAC equation for the Gibbs excess energy with Chemical Reaction Equilibria. Revised parameters of the model for these systems are reported.
Heath C Turner - One of the best experts on this subject based on the ideXlab platform.
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simulation of Chemical Reaction Equilibria by the Reaction ensemble monte carlo method a review
ChemInform, 2008Co-Authors: Heath C Turner, William R Smith, John K Brennan, Martin Lisal, Karl J Johnson, Keith E GubbinsAbstract:Understanding and predicting the equilibrium behaviour of Chemically reacting systems in highly non-ideal environments is critical to many fields of science and technology, including solvation, nanoporous materials, catalyst design, combustion and propulsion science, shock physics and many more. A method with recent success in predicting the equilibrium behaviour of Reactions under non-ideal conditions is the Reaction ensemble Monte Carlo method (RxMC). RxMC has been applied to Reactions confined in porous solids or near solid surfaces, Reactions at high temperature and/or high pressure, Reactions in solution and at phase interfaces. The only required information is a description of the intermolecular forces among the system molecules and standard free-energy data for the reacting components. Extensions of the original method include its combination with algorithms for systems involving phase Equilibria, constant-enthalpy and constant-internal energy adiabatic conditions, a method to include Reaction kine...
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simulation of Chemical Reaction Equilibria and kinetics in heterogeneous carbon micropores
Applied Surface Science, 2002Co-Authors: Heath C Turner, John K Brennan, Jorge Pikunic, Keith E GubbinsAbstract:Abstract We present a simulation study which shows how the equilibrium yield and kinetics of Chemical Reactions can be enhanced by tailoring the structure and surface chemistry of the catalyst support material. Equilibrium results are presented for the ammonia synthesis Reaction, N 2 +3H 2 ↔2NH 3 , occurring within various carbon supports, representing a range of Chemical and physical surface heterogeneity. Using a simulation technique known as Reactive Monte Carlo (RxMC), we find that surface activation and pore width are primary factors in determining the conversion of the ammonia synthesis Reaction while effects of surface corrugation are small. We probe the kinetic effects of physical confinement within microporous carbons by studying the bimolecular hydrogen iodide decomposition Reaction, 2HI→H 2 +I 2 , in carbon slit-pores and nanotubes. The rate constant of this Reaction is measured by combining the quasi-equilibrium hypothesis of transition-state theory (TST) with the RxMC simulation technique. The kinetic simulations represent a new method for probing Reaction kinetics in non-ideal environments and show accurate results when applied to the hydrogen iodide decomposition Reaction.
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influence of Chemical and physical surface heterogeneity on Chemical Reaction Equilibria in carbon micropores
Molecular Physics, 2001Co-Authors: Heath C Turner, Jorge Pikunic, Keith E GubbinsAbstract:Recent simulation results are presented for the equilibrium yield of the ammonia synthesis Reaction in various model microporous carbons. It is found that the Reaction Equilibria within the micropores is affected by many factors, including pore size, pore shape, connectivity, surface roughness, and surface Chemical activation. In order to probe these effects, reactive Monte Carlo simulations of the Reaction were performed in several microporous carbon models: smooth slit-shaped carbon pores, a realistic carbon model generated from experimental diffraction data, single-walled carbon nanotubes, and smooth slit-shaped pores activated by carboxyl surface groups. The simulations show that the ammonia conversion is most sensitive to the carbon pore width and to the amount of surface Chemical activation. Effects of surface corrugation and pore connectivity on the equilibrium Reaction yield are minimal.
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effect of confinement on Chemical Reaction Equilibria the Reactions 2no no 2 and n2 3h2 2nh3 in carbon micropores
Journal of Chemical Physics, 2001Co-Authors: Heath C Turner, Karl J Johnson, Keith E GubbinsAbstract:We report reactive Monte Carlo (RMC) simulations of Reaction Equilibria for both the nitric oxide dimerization and the ammonia synthesis Reactions. We have applied the RMC technique to both a single bulk phase and also to a two-phase system, composed of the bulk gas and a slit-shaped pore, with pore parameters chosen to model activated carbon fibers. We achieve close agreement with the experimentally measured conversions of nitric oxide and ammonia in the bulk phase. Both Reactions involve a stoichiometric decrease in mole number, which should cause the yield of each to be enhanced by the increased density within the pore phase. We show that the effect of confinement on the yield of both Reactions is significant, and is particularly dramatic for the nitric oxide Reaction; in addition, the ammonia synthesis Reaction is affected by the selective adsorption of nitrogen over hydrogen in the pore under certain conditions.
Javad Noroozi - One of the best experts on this subject based on the ideXlab platform.
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an efficient molecular simulation methodology for Chemical Reaction Equilibria in electrolyte solutions application to co2 reactive absorption
Journal of Physical Chemistry A, 2019Co-Authors: Javad Noroozi, William R SmithAbstract:We develop a computationally efficient molecular-based simulation algorithm for Chemical Reaction Equilibria in liquids containing neutral and ionic species, which is based on the combination of classical force field and ab initio calculations and permits calculations involving very small species concentrations. We show its application to the reactive absorption of CO2 in aqueous monoethanolamine (MEA) solvent as a benchmark case, the first time that a quantitatively accurate predictive approach requiring no experimental data has been successfully applied to calculate all solution species concentrations for this system, including the partial pressure of CO2 above the solution. The Reaction Ensemble Monte Carlo (REMC) algorithm, the only other generally applicable approach, requires special system-dependent Monte Carlo enhancements for its implementation, and to detect species with very small concentrations requires long simulation times and/or large system sizes. In contrast, the proposed algorithm can be straightforwardly implemented for systems of any molecular complexity using a standard Molecular Dynamics (MD) simulation package capable of calculating free energy changes and can calculate small species concentrations with normal simulation times and system sizes. In addition, the inherent parallelization capability of MD (which is problematic for MC-based approaches) enables the algorithm's computationally efficient implementation. The H2O-MEA-CO2 benchmark system has been the subject of many previous studies based on macroscopic thermodynamic modeling, which primarily involves fitting their parameters (of which Reaction p K values are the most important) to experimental data measurements. To make contact with such approaches, we show the translation of the molecular-based quantities to the direct prediction of these parameters and calculate Reaction equilibrium in the framework of a Henry Law-based Chemical potential model. We consider both the ideal solution form and its extension using the Davies equation for the species activity coefficients. We study a range of temperatures and CO2 solution loadings in a 30 wt % MEA solution and incorporate an uncertainty analysis in our methodology. We find that the uncertainties of the simulated solution species compositions are comparable to those of the available experimental data. We report predictions of minor species compositions of very small magnitude, for which experimental measurements are typically extremely challenging.