OLI Systems Inc

Morris Plains, NJ, United States

OLI Systems Inc

Morris Plains, NJ, United States
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Springer R.D.,OLI Systems Inc | Wang Z.,Pacific Northwest National Laboratory | Anderko A.,OLI Systems Inc | Wang P.,OLI Systems Inc | Felmy A.R.,Pacific Northwest National Laboratory
Chemical Geology | Year: 2012

Phase equilibria in mixtures containing carbon dioxide, water, and chloride salts have been investigated using a combination of solubility measurements and thermodynamic modeling. The solubility of water in the CO 2-rich phase of ternary mixtures of CO 2, H 2O and NaCl or CaCl 2 was determined, using near infrared spectroscopy, at 90atm and 40 to 100°C. These measurements fill a gap in the experimental database for CO 2-water-salt systems, for which phase composition data have been available only for the H 2O-rich phases. A thermodynamic model for CO 2-water-salt systems has been constructed on the basis of the previously developed Mixed-Solvent Electrolyte (MSE) framework, which is capable of modeling aqueous solutions over broad ranges of temperature and pressure, is valid to high electrolyte concentrations, treats mixed-phase systems (with both scCO 2 and water present) and can predict the thermodynamic properties of dry and partially water-saturated supercritical CO 2 over broad ranges of temperature and pressure. Within the MSE framework the standard-state properties are calculated from the Helgeson-Kirkham-Flowers equation of state whereas the excess Gibbs energy includes a long-range electrostatic interaction term expressed by a Pitzer-Debye-Hückel equation, a virial coefficient-type term for interactions between ions and a short-range term for interactions involving neutral molecules. The parameters of the MSE model have been evaluated using literature data for both the H 2O-rich and CO 2-rich phases in the CO 2-H 2O binary and for the H 2O-rich phase in the CO 2-H 2O-NaCl/KCl/CaCl 2/MgCl 2 ternary and multicompontent systems. The model accurately represents the properties of these systems at temperatures from 0°C to 300°C and pressures up to ~4000atm. Further, the solubilities of H 2O in CO 2-rich phases that are predicted by the model are in agreement with the new measurements for the CO 2-H 2O-NaCl and CO 2-H 2O-CaCl 2 systems even though the new data were not used in the parameterization of the model. Thus, the model can be used to predict the effect of various salts on the water content and water activity in CO 2-rich phases on the basis of parameters determined from the properties of aqueous systems. Given the importance of water activity in CO 2-rich phases for mineral reactivity, the model can be used as a foundation for predicting mineral transformations across the entire CO 2/H 2O composition range from aqueous solution to anhydrous scCO 2. An example application using the model is presented which involves the transformation of forsterite to nesquehonite as a function of temperature and water content in the CO 2-rich phase. © 2012 Elsevier B.V.

Engelhardt G.R.,OLI Systems Inc | MacDonald D.D.,Pennsylvania State University | MacDonald D.D.,King Fahd University of Petroleum and Minerals
Electrochimica Acta | Year: 2012

The case when the potential distribution inside a corrosion cavity obeys Ohm's law is considered. Mathematically, the potential drop in the crevice is described by a Poisson-type equation with a non-linear source term. A simple method for finding all possible solutions in a one-dimensional approximation and for investigating their stability has been developed. We derive a simple relation for estimating the critical depth of the crevice, L c (which is defined as the depth at which the active-passive transition just occurs within the crevice) as a function of the width of the crevice, w, electrolyte conductivity, κ, metal potential, E met, and a polarization curve. It is shown that L c is proportional to √(wκ) and is a linear function of E met. Calculation of the corrosion damage (maximum depth of the penetration into the metal, w max) as a function of time and position inside the crevice has been performed. It is shown that during the initial stages of crevice corrosion, when the one-dimensional approximation is valid, w max is determined mainly by the polarization curve for the anodic dissolution of the metal. It is shown that, in the general case, it is impossible to neglect the potential drop in the external environment when quantitatively describing crevice corrosion. © 2012 Elsevier Ltd. All rights reserved.

Zhang Y.,Pennsylvania State University | Urquidi-MacDonald M.,Pennsylvania State University | Engelhardt G.R.,OLI Systems Inc | MacDonald D.D.,Pennsylvania State University | MacDonald D.D.,King Fahd University of Petroleum and Minerals
Electrochimica Acta | Year: 2012

Passivity on steel surfaces plays a crucial role in the development of pitting corrosion damage. In this work, the passivity on Type 403 stainless steel (SS), low pressure steam turbine (LPST) blade alloy, and A470/471 low alloy steel (LPST) disk/rotor steel has been studied in borate buffer solution. The highly defective barrier layers on Type 403 SS and A470/471 steel, formed at potentials in the passive region, exhibit n-type semiconductor behavior, due to the predominance of oxygen vacancies and/or cation interstitials as crystallographic point defects. The defective Cr 2O 3 barrier layer on the Type 403 SS surface has a greater donor concentration and a smaller thickness than does the barrier layer (defective Fe 3O 4) on the A470/471 steel surface. Increasing oxygen and chloride concentration in the electrolyte increase the donor concentration in the passive film on Type 403 SS. In the passive regions of Type 403 SS and A470/471 steel, the steady-state current density is nearly independent of, and the steady-state barrier layer thickness increases linearly with, increasing film formation potential. These experimental observations are interpreted in terms of the point defect model (PDM) for the passive state. Mechanistic analysis of electrochemical impedance spectroscopy (EIS) data by the impedance model developed from the PDM, is also performed, and the validity of the impedance model is demonstrated. © 2012 Elsevier Ltd.

Choudhary V.,University of Delaware | Mushrif S.H.,Nanyang Technological University | Ho C.,University of Delaware | Anderko A.,OLI Systems Inc | And 5 more authors.
Journal of the American Chemical Society | Year: 2013

5-(Hydroxymethyl)furfural (HMF) and levulinic acid production from glucose in a cascade of reactions using a Lewis acid (CrCl3) catalyst together with a Brønsted acid (HCl) catalyst in aqueous media is investigated. It is shown that CrCl3 is an active Lewis acid catalyst in glucose isomerization to fructose, and the combined Lewis and Brønsted acid catalysts perform the isomerization and dehydration/rehydration reactions. A CrCl3 speciation model in conjunction with kinetics results indicates that the hydrolyzed Cr(III) complex [Cr(H2O)5OH]2+ is the most active Cr species in glucose isomerization and probably acts as a Lewis acid-Brønsted base bifunctional site. Extended X-ray absorption fine structure spectroscopy and Car-Parrinello molecular dynamics simulations indicate a strong interaction between the Cr cation and the glucose molecule whereby some water molecules are displaced from the first coordination sphere of Cr by the glucose to enable ring-opening and isomerization of glucose. Additionally, complex interactions between the two catalysts are revealed: Brønsted acidity retards aldose-to-ketose isomerization by decreasing the equilibrium concentration of [Cr(H2O)5OH]2+. In contrast, Lewis acidity increases the overall rate of consumption of fructose and HMF compared to Brønsted acid catalysis by promoting side reactions. Even in the absence of HCl, hydrolysis of Cr(III) decreases the solution pH, and this intrinsic Brønsted acidity drives the dehydration and rehydration reactions. Yields of 46% levulinic acid in a single phase and 59% HMF in a biphasic system have been achieved at moderate temperatures by combining CrCl3 and HCl. © 2013 American Chemical Society.

Engelhardt G.R.,OLI Systems Inc | Macdonald D.D.,Pennsylvania State University
Corrosion Science | Year: 2010

The application of standard mathematical techniques for the solution of mass transport equations, in the case of advection that is caused by the pulsating movement of crack walls in the case of corrosion fatigue, can be very time consuming. This problem arises, due to the requirement that the time step that must be employed, when solving the non-stationary equations numerically, must be significantly smaller than the period of oscillation. For overcoming these time-consuming limitations, a simple algorithm, which is based on eliminating the convective term from the equations of mass transfer in the pulsating slab by a suitable change of variables, was developed. The estimation of the advection effect on the rate of corrosion fatigue has been performed for the cases of diffusion and mixed kinetic control at high frequencies of applied stress. It is shown that, in many cases, it is possible to use codes that were developed for describing stress corrosion cracking, i.e. for the case of mass transfer without advection at zero loading frequency, to predict corrosion fatigue crack propagation rate, by simply substituting an effective crack length. Numerical calculations that have been performed in this work also show that the method developed here yields results that are applicable not only to the elevated frequencies, but to the any arbitrary frequency from 0 to ∞ for estimating corrosion fatigue crack propagation rate. © 2009 Elsevier Ltd. All rights reserved.

Macdonald D.D.,Pennsylvania State University | Engelhardt G.R.,OLI Systems Inc
ECS Transactions | Year: 2010

The Point Defect Model (PDM) has been shown to accurately describe the properties of passive films that form on metal surfaces in contact with aggressive environments under both open circuit and anodic polarization conditions. However, the commonly-employed PDM, known henceforth as Generation II or PDM-II assumes that passivity arises from the properties of the barrier layer and that the outer layer, if present, contributes negligibly to the interfacial impedance. In this paper, we describe a third generation of the PDM, PDM-III, in which a resistive outer layer exists on the surface and contributes substantially to the impedance of the interface and hence to the corrosion resistance. The outer layer is shown to have a profound impact on the properties of the barrier layer and under certain circumstances the barrier layer is predicted to disappear. This new form of depassivation is observed experimentally in the corrosion of carbon steel in CO2-acidified oil-field brines, for example. The use of electrochemical impedance spectroscopy to characterize passive films having resistive outer layers is describe and illustrated with reference to the passive state on zirconium in simulated PWR (Pressurized Water Reactor) primary coolant. ©The Electrochemical Society.

Wang P.,OLI Systems Inc | Anderko A.,OLI Systems Inc
Industrial and Engineering Chemistry Research | Year: 2013

A comprehensive model has been developed for calculating the interfacial tension (σ) in liquid-liquid systems with or without electrolyte components. The model consists of an equation for computing the interfacial tension of two-liquid-phase nonelectrolyte systems and an expression for the effect of the electrolyte concentration. The dependence of the interfacial tension on the electrolyte concentration was derived by combining the Gibbs equation with a modified Langmuir adsorption isotherm that represents the interfacial excess of the solute species. The Langmuir adsorption formalism was extended by introducing the effects of binary interactions between solute species (ions or molecules) on the interface. The equation for the interfacial tension of nonelectrolyte liquid-liquid systems was derived using a general thermodynamic framework that was empirically extended by introducing an effective interfacial area that is defined for each component and takes into account the effects of other components at the interface. The model was found to reproduce experimental data for a variety of liquid-liquid systems. In particular, the interfacial tension of ternary systems can be accurately predicted using parameters determined from only binary data. Furthermore, the interfacial tension model was coupled with a previously developed thermodynamic model to provide activity coefficients and equilibrium concentrations in coexisting liquid phases. This makes it possible to reproduce the effects of speciation and salting out or salting in. Because of the coupling of the thermodynamic model with interfacial tension calculations, the variation of σ with electrolyte concentration can be reasonably predicted even without introducing electrolyte-specific parameters in the interfacial tension model. Thus, the model can be used to estimate the electrolyte effect on σ in the absence of experimental data. With regressed model parameters, the average deviations between the calculated results and experimental data were 0.50 mN·m-1 for 30 binary nonelectrolyte systems, 0.88 mN·m-1 for 23 ternary nonelectrolyte systems, and 0.16 mN·m-1 for 26 systems with ionic components. © 2013 American Chemical Society.

Wang P.,OLI Systems Inc | Anderko A.,OLI Systems Inc | Young R.D.,OLI Systems Inc
Industrial and Engineering Chemistry Research | Year: 2011

A comprehensive model has been developed for calculating the surface tension of aqueous, nonaqueous, and mixed-solvent electrolyte systems ranging from dilute solutions to fused salts. The model consists of a correlation for computing the surface tension of solvent mixtures and an expression for the effect of electrolyte concentration. The dependence of surface tension on electrolyte concentration has been derived from the Gibbs equation combined with a modified Langmuir adsorption isotherm for modeling the surface excess of species. The model extends the Langmuir adsorption formalism by introducing the effects of binary interactions between solute species (ions or molecules) on the surface. This extension is especially important for high electrolyte concentrations and in strongly speciated systems. The surface tension of mixed solvents is calculated by utilizing the surface tensions of the constituent pure components together with an effective surface concentration, which is defined for each component and takes into account interactions between solvent molecules. This procedure has been shown to reproduce experimental data for a variety of mixtures. In particular, it accurately predicts the surface tension of ternary solvent mixtures using parameters determined from only binary data. The surface tension model has been coupled with a previously developed thermodynamic equilibrium model to provide speciation and activity coefficients, which are necessary for electrolyte systems. This makes it possible to reproduce the effects of complexation or other reactions in solution. In all cases for which experimental data are available and have been tested, the new model has been shown to be accurate in reproducing surface tension over wide ranges of temperature and concentration. The average deviations between the calculated results and experimental data are 0.68% for binary solvent mixtures, 1.89% for ternary solvent mixtures, and 0.71% for salt solutions up to the solid saturation or pure solute limit. © 2011 American Chemical Society.

Wang P.,OLI Systems Inc | Anderko A.,OLI Systems Inc
Fluid Phase Equilibria | Year: 2011

A previously developed thermodynamic model for mixed-solvent electrolyte solutions and associated transport property models have been applied to calculating various properties of ionic liquid systems. For the analysis, imidazolium-based ionic liquids and their mixtures with water and organic solvents have been selected. The ionic liquids are treated as dissociable species that are subject to chemical speciation equilibria. The parameters of the model are determined from available thermodynamic property data including phase equilibria, activity coefficients, osmotic coefficients, enthalpies of mixing and dilution, and heat capacities. Subsequently, electrical conductivities and viscosities are calculated using the chemical speciation obtained from thermodynamic analysis. The modeling framework has been designed to reproduce the properties of ionic solutions at temperatures ranging from the freezing point to 300 °C and concentrations ranging from infinite dilution to the fused salt limit. The accuracy of the thermodynamic model has been verified by calculating vapor-liquid, liquid-liquid, and solid-liquid equilibria in wide ranges of composition and temperature. In view of the strong dependence of electrical conductivity and, secondarily, viscosity on the ionic concentration, the accurate representation of transport properties confirms that the thermodynamic speciation results are reasonable, thus verifying the applicability of the computational framework to modeling multiple thermophysical properties of ionic liquid systems. © 2010 Elsevier B.V.

Wang P.,OLI Systems Inc | Anderko A.,OLI Systems Inc
International Journal of Thermophysics | Year: 2012

A model has been established for calculating the thermal conductivity of aqueous electrolyte solutions containing the Na +, K +, Mg 2+, Ca 2+, Cl -, SO 4 2-, CO 3 2-, HCO 3 -, and Br - ions. The model is based on a previously developed computational framework for the thermal conductivity of mixed-solvent electrolyte systems, whichhasbeenexpandedbyexplicitlyaccountingfor pressure effects inaddition totemperature and electrolyte composition effects. Themodel consists of a contribution of the solvent, a contribution of individual species expressed using modified Riedel coefficients, and an ionic strength-dependent term that is due to interactions between species. Themodel accurately represents the thermal conductivity of solutions containing single and multiple salts at temperatures ranging from 273 K to 573 K, pressures up to at least 1400 bar, and concentrations up to the limit of solid saturation. Further, the model has beenapplied toseawaterandused to elucidate thediscrepanciesbetweenthe experimental data for seawater and those for Na-K-Mg-Ca-Cl-SO 4 salt solutions.With parameters evaluated on the basis of data for binary and multicomponent salt solutions, the model provides reliable predictions of the thermal conductivity of seawater. © Springer Science+Business Media, LLC 2012.

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