W. Vincent Wilding

Brigham Young University - Provo Main Campus, Provo, Utah, United States

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Publications (60)90.17 Total impact

  • Richard A Messerly · Richard L Rowley · Thomas A Knotts · W Vincent Wilding ·
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    ABSTRACT: A rigorous statistical analysis is presented for Gibbs ensemble Monte Carlo simulations. This analysis reduces the uncertainty in the critical point estimate when compared with traditional methods found in the literature. Two different improvements are recommended due to the following results. First, the traditional propagation of error approach for estimating the standard deviations used in regression improperly weighs the terms in the objective function due to the inherent interdependence of the vapor and liquid densities. For this reason, an error model is developed to predict the standard deviations. Second, and most importantly, a rigorous algorithm for nonlinear regression is compared to the traditional approach of linearizing the equations and propagating the error in the slope and the intercept. The traditional regression approach can yield nonphysical confidence intervals for the critical constants. By contrast, the rigorous algorithm restricts the confidence regions to values that are physically sensible. To demonstrate the effect of these conclusions, a case study is performed to enhance the reliability of molecular simulations to resolve the n-alkane family trend for the critical temperature and critical density.
    The Journal of Chemical Physics 09/2015; 143(10):104101. DOI:10.1063/1.4928865 · 2.95 Impact Factor

  • Fluid Phase Equilibria 09/2015; DOI:10.1016/j.fluid.2015.08.030 · 2.20 Impact Factor
  • Sarah A. Brockbank · Neil F. Giles · Richard L. Rowley · Wade Vincent Wilding ·
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    ABSTRACT: A first-order temperature-dependent group contribution method was developed to predict Henry’s law constants of hydrocarbons, alcohols, ketones, and formates in which none of the functional groups are attached directly to a benzene ring. Efforts to expand this method to include ester and ether groups were unsuccessful. Second-order groups were developed at a reference condition of 298.15 K and 100 kPa. A second-order temperature-dependent group contribution method was then developed for hydrocarbons, ketones, esters, ethers, and alcohols. These methods were compared to existing literature prediction methods.
    Journal of Chemical & Engineering Data 12/2013; 59(4):1052–1061. DOI:10.1021/je400770a · 2.04 Impact Factor
  • R. L. Rowley · W. V. Wilding · A. Congote · N. F. Giles ·
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    ABSTRACT: The effectiveness of chemical process designs and the reliability of mixture models are no better than the accuracy of the pure-chemical thermophysical properties used. A systems-analysis approach can be used in evaluating data from all available sources to triangulate on the best values which can be of higher accuracy than the individual values. This approach includes applied constraints on property values from interproperty relationships, expected smooth trends of properties between related chemicals, and the impact of chemical similarities and differences. These constraints are simultaneously included in the evaluation of the raw experimental data to provide recommended values of constant properties and correlations for temperature-dependent properties. This paper will illustrate how this systems approach has been used to provide recommended property values in the DIPPR 801 evaluated database. In particular, a recent re-evaluation of the properties of the 1,n-alkanediol compounds in the DIPPR database, prompted by the availability of more recently measured critical temperatures and pressures of three members of this family, is used as an illustrative case study of this approach, and some of the newly recommended property values and temperature-dependent correlations for this family are provided.
    Journal of Chemical & Engineering Data 11/2013; 59(4):1031–1037. DOI:10.1021/je400747s · 2.04 Impact Factor
  • Loren C. Wilson · W. Vincent Wilding · Grant M. Wilson ·
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    ABSTRACT: Pressure–volume–temperature (PVT) data on hydrogen fluoride (HF) were measured from (293 to 473) K and from low pressure to near saturation pressure. These data were compared to existing literature data, and a model was developed which accurately represents the association behavior of pure, gaseous hydrogen fluoride. This model includes the assumption of HF dimers and hexamers in equilibrium with monomeric HF. The vapor pressure of hydrogen fluoride was also measured from (293 to 454) K, and these measurements were correlated using the Riedel equation. There is good agreement between these vapor pressures and previous work, while this work extends the measured vapor pressure for HF to within 7 K of the critical temperature.
    Journal of Chemical & Engineering Data 11/2013; 59(4):983–990. DOI:10.1021/je400733m · 2.04 Impact Factor
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    ABSTRACT: A database containing Henry’s law constants, infinite dilution activity coefficients, and solubility data of industrially important chemicals has been compiled for aqueous systems. These properties are important in predicting the fate and transport of chemicals in the environment. The structure of this database is compatible with the existing \(\hbox {DIPPR}^{\circledR }\) 801 database and DIADEM interface, and data are included for a subset of compounds found in the \(\hbox {DIPPR}^{\circledR }\) 801 database. Thermodynamic relationships, chemical family trends, and predicted values were carefully considered when designating recommended values.
    International Journal of Thermophysics 11/2013; 34(11):2027-2045. DOI:10.1007/s10765-013-1530-z · 0.96 Impact Factor
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    ABSTRACT: Henry's law constants and infinite dilution activity coefficients were measured for toluene, 1-butanol, anisole, 1,2-difluorobenzene, 4-bromotoluene, 1,2,3-trichlorobenzene, and 2,4-dichlorotoluene in water using the inert gas stripping method at ambient pressure (approximately 86.2 kPa) and at temperatures between 281.15 K and 323.15 K. Fugacity ratios, required to determine infinite dilution activity coefficients for the solid solutes, were calculated from literature values for the heat of fusion and the liquid and solid heat capacities. Chemicals were chosen based on missing or conflicting data from the literature.
    Fluid Phase Equilibria 06/2013; 348:45–51. DOI:10.1016/j.fluid.2013.03.023 · 2.20 Impact Factor
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    ABSTRACT: Ternary LLE data have been experimentally measured for several systems consisting of biodiesel compounds. Systems measured include mixtures with the methyl esters of lauric, myristic, palmitic, and oleic acids, each with glycerin and water. Data were collected at atmospheric pressure and 60 °C. These ternary systems have been correlated using the NRTL equation. These data and correlation parameters can be used to improve separations efficiency in transesterified biodiesel fuels.
    Journal of Chemical & Engineering Data 03/2013; 58(4):1001–1004. DOI:10.1021/je301348z · 2.04 Impact Factor
  • Sonal Patel · W Vincent Wilding · Richard L Rowley ·
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    ABSTRACT: Two-phase molecular dynamics simulations employing a Monte Carlo volume sampling method were performed using an ab initio based force field model parameterized to reproduce quantum-mechanical dimer energies for methanol and 1-propanol at temperatures approaching the critical temperature. The intermolecular potential models were used to obtain the binodal vapor-liquid phase dome at temperatures to within about 10 K of the critical temperature. The efficacy of two all-atom, site-site pair potential models, developed solely from the energy landscape obtained from high-level ab initio pair interactions, was tested for the first time. The first model was regressed from the ab initio landscape without point charges using a modified Morse potential to model the complete interactions; the second model included point charges to separate Coulombic and dispersion interactions. Both models produced equivalent phase domes and critical loci. The model results for the critical temperature, density, and pressure, in addition to the sub-critical equilibrium vapor and liquid densities and vapor pressures, are compared to experimental data. The model's critical temperature for methanol is 77 K too high while that for 1-propanol is 80 K too low, but the critical densities are in good agreement. These differences are likely attributable to the lack of multi-body interactions in the true pair potential models used here.
    The Journal of Chemical Physics 12/2011; 135(23):234514. DOI:10.1063/1.3670013 · 2.95 Impact Factor
  • Jeffrey R. Rowley · Richard L. Rowley · W. Vincent Wilding ·
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    ABSTRACT: Published flash point prediction methods are evaluated for accuracy against experimental data from the DIPPR ® 801 database. The most accurate methods require a vapor pressure correlation, which is often not available. Two new methods are presented, one that uses the vapor pressure, and one based on the normal boiling point and enthalpy of vaporization at the normal boiling point. The vapor pressure method shows little improvement over the previous methods unless group contributions are implemented. The boiling point method predicts the flash point within an absolute average deviation of 1.3% when compared with data for more than 1000 compounds. The previous most accurate method that was not based on vapor pressure exhibited an absolute average deviation of 1.84% for the same test set. Copyright © 2010 John Wiley & Sons, Ltd.
    Fire and Materials 10/2011; 35(6):343 - 351. DOI:10.1002/fam.1057 · 1.32 Impact Factor
  • Jiangping Liu · W. Vincent Wilding · Richard L. Rowley ·
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    ABSTRACT: A local composition model is developed for mixture dielectric constants based on the nonrandom two-liquid (NRTL) model commonly used for correlating activity coefficients in vapor−liquid equilibrium (VLE) data regression. In this model the NRTL local compositions, which represent an effective local molecular structure, are the counterpart of the Kirkwood factor g, which in dielectric constant theory characterizes local molecular orientations and their effect on the static dielectric constant. The resultant model requires values for the pure-component dielectric constant and binary NRTL model parameters available from VLE data compilations or predicted from the universal functional activity coefficient model (UNIFAC). It is predictive in that no mixture dielectric constant data are used and there are no adjustable parameters. Predictions made on 16 binary and six ternary systems at various compositions and temperatures compare favorably with extant correlations that require experimental values to fit an adjustable parameter in the mixing rule and are significantly improved over values predicted by Oster's equation that also has no adjustable parameters.
    Journal of Chemical & Engineering Data 03/2011; 56(5). DOI:10.1021/je200007x · 2.04 Impact Factor
  • J R Rowley · R L Rowley · W V Wilding ·
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    ABSTRACT: A new method of estimating the lower flammability limit (LFL) of general organic compounds is presented. The LFL is predicted at 298 K for gases and the lower temperature limit for solids and liquids from structural contributions and the ideal gas heat of formation of the fuel. The average absolute deviation from more than 500 experimental data points is 10.7%. In a previous study, the widely used modified Burgess-Wheeler law was shown to underestimate the effect of temperature on the lower flammability limit when determined in a large-diameter vessel. An improved version of the modified Burgess-Wheeler law is presented that represents the temperature dependence of LFL data determined in large-diameter vessels more accurately. When the LFL is estimated at increased temperatures using a combination of this model and the proposed structural-contribution method, an average absolute deviation of 3.3% is returned when compared with 65 data points for 17 organic compounds determined in an ASHRAE-style apparatus.
    Journal of hazardous materials 02/2011; 186(1):551-7. DOI:10.1016/j.jhazmat.2010.11.039 · 4.53 Impact Factor
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    Sonal Patel · W Vincent Wilding · Richard L Rowley ·
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    ABSTRACT: Molecular dynamics simulations were performed to determine two-phase configurations of model propane molecules below the critical point and in the near-critical, two-phase region. A postprocessor that uses a Monte Carlo method for determination of volumes attributable to each molecule was used to obtain density histograms of the particles from which the bulk coexisting equilibrium vapor and liquid densities were determined. This method of analyzing coexisting densities in a two-phase simulation is straightforward and can be easily implemented for complex, multisite models. Various degrees of internal flexibility in the propane models have little effect on the coexisting densities at temperatures 40 K or more below the critical point, but internal flexibility (angle bending and bond vibrations) does affect the saturated liquid densities in the near-critical region, changing the critical temperature by approximately 20 K. Shorter cutoffs were also found to affect the phase dome and the location of the critical point.
    The Journal of Chemical Physics 01/2011; 134(2):024101. DOI:10.1063/1.3528117 · 2.95 Impact Factor
  • J.R. Rowley · R.L. Rowley · W.V. Wilding ·
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    ABSTRACT: The flash point is an important indicator of the flammability of liquids and solids. Many methods of estimating the flash point of pure chemicals have been published, but these methods either rely on accurate thermodynamic data or are limited to hydrocarbons. This work presents a method of estimating the flash point of general organic compounds based entirely on structural contributions. The proposed correlation results in an average absolute deviation of 2.84% from experimental values for more than 1,000 organic compounds. © 2010 American Institute of Chemical Engineers Process Saf Prog, 2010
    Process Safety Progress 12/2010; 29(4):353 - 358. DOI:10.1002/prs.10401 · 0.46 Impact Factor
  • Sarah A. Purcell · Neil Giles · Richard L. Rowley · W. Vincent Wilding ·
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    ABSTRACT: Henry's law constant is important in engineering and environmental calculations. It can be used to determine the fate and transport of chemicals in air and water, and it can also be used in the design of air-stripping columns. An extensive literary review was conducted to compile a database of experimental Henry's law constants. Reported values of each chemical are compared in addition to the methods of measurement. Methods and family trends are considered in order to designate a recommended value for each compound in the database. Existing predictive methods are compared, and experimental and modeling needs are identified.
    2010 AIChE Annual Meeting; 11/2010
  • R. L. Rowley · W. V. Wilding · A. Congote · N. F. Giles ·
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    ABSTRACT: Maintaining currency of thermophysical property values in a chemical database with the rapid pace of published new experimental data is particularly difficult for evaluated databases. Evaluated databases that provide recommended values for each of the properties require labor intensive evaluation of not only the newly published property values, but also all related property values stored in the database. One possible solution to this problem is the establishment of a triage system to evaluate the potential influence of new data on recommended property values. Such a priority assignment system for the DIPPR®801 Pure Chemical Database has been developed. Evaluation of the potential impact of new data on the recommended values is done through a correlation for the Influence Factor (IF) that includes weighting factors for the type of property, the experimental methodology, the quality of the data, the quantity of data upon which the current recommendation is based, and the significance of the potential change. Database IFs help prioritize review work on the DIPPR®801 database and thereby contribute to its quality and currency. KeywordsDatabase-DIPPR-Thermophysical properties-Weighting factor
    International Journal of Thermophysics 05/2010; 31(4):860-874. DOI:10.1007/s10765-010-0706-z · 0.96 Impact Factor
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    ABSTRACT: The flash point is an important indicator of the flammability of a chemical. For safety purposes, many data compilations report the lowest value and not the most likely. This practice, combined with improper documentation and poor data storage methods, has resulted in compilations filled with fire-hazard data that are inconsistent with related properties and between members of homologous chemical series. In this study, the flash points reported in the DIPPR® 801 database and more than 1,400 other literature values were critically reviewed based on measurement method, inter-property relations, and trends in chemical series. New measurements for seven compounds illustrate the differences between experimental flash points and data commonly found in fire-hazard compilations. With a critically reviewed set of experimental data, published predictive methods for the flash point were evaluated for accuracy. KeywordsData evaluation-Database-DIPPR-Flash point-Prediction
    International Journal of Thermophysics 05/2010; 31(4):875-887. DOI:10.1007/s10765-010-0716-x · 0.96 Impact Factor
  • Jeffrey R. Rowley · Richard L. Rowley · W. Vincent Wilding ·
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    ABSTRACT: The lower flammability limits of 18 CxHyOzNw liquids were measured as a function of initial temperature in an ASHRAE 12 L style apparatus. Results indicate that the calculated adiabatic flame temperature is not constant, as previously reported but rather decreases with increasing temperature. Consequently, the modified Burgess−Wheeler law does not accurately predict the effect of temperature on the lower flammability limit. Though few direct comparisons are possible, previously reported data agree well with the values measured in this study.
    Journal of Chemical & Engineering Data 02/2010; 55(9). DOI:10.1021/je901076a · 2.04 Impact Factor
  • Sonal Patel · W. Vincent Wilding · Richard L. Rowley ·
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    ABSTRACT: A molecular dynamics (MD) method [Fern et al., J. Phys. Chem. B 2007, 111, 3469.] recently developed for determination of phase equilibrium in a single, two-phase simulation has been shown to be accurate even near the critical point because complete phase separation and no particle insertions are required. In this work, we modify the method for structured molecules by employing a Monte Carlo (MC) method to determine the associated volume for every particle in the simulation cell. Bulk liquid and vapor densities are then determined by comparing the molecular volume distributions of liquid and vapor in the two-phase simulations to those obtained in single-phase simulations. Two-phase molecular dynamic (MD) simulations were performed on n-Propane using a Transferable Potential for Phase Equilibria (TraPPE) model. The coexisting liquid and vapor densities obtained agreed well with literature values from Gibbs Ensemble Monte Carlo (GEMC) simulations.
    2009 AIChE Annual Meeting; 11/2009
  • Jiang-Ping Liu · W. Vincent Wilding · Neil F. Giles · Richard L. Rowley ·
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    ABSTRACT: The dielectric constant (ε) or relative static permittivity of a material represents the capacitance of the material relative to a vacuum and is important in many industrial applications. Nevertheless, accurate experimental values are often unavailable, and current prediction methods lack accuracy and are often unreliable. Reported here is the development and testing of a new QSPR (quantitative structure property relation) correlation of ε for organic chemicals. On the basis of the regression analysis and tests of the correlation in prediction mode, the average absolute percent error is expected to be less than 3 % when applied to hydrocarbons and nonpolar compounds and less than 18 % when applied to polar compounds with ε values ranging from 1.0 to 50.0. The correlation requires values for the dipole moment, solubility parameter, van der Waals area, and refractive index. We show also that density functional calculations of the dipole moment using B3LYP/6-311+G(3df,2p) can be used in the ε correlation, when experimental values are unavailable, with little decrease in accuracy of the predicted values.
    Journal of Chemical & Engineering Data 09/2009; 55(1). DOI:10.1021/je900518k · 2.04 Impact Factor