bluuebunny/crossref_metadata_2025_split huggingface dataset:
Infinite dilution fugacity coefficients and the general behavior of dilute binary systems
Authors: Debenedetti P. G. , Kumar S. K. 
Published: June 2004

AbstractA universally valid formal expression for the composition dependence of solute and solvent fugacity coefficients in any dilute binary system far from criticality is derived in this paper. In the present context, dilution denotes the y1 → O limit, regardless of the mixture's molar density. The results are independent of the system under study and of the choice of equation of state. The solute fugacity coefficient is simply the product of a composition‐independent term (the infinite dilution fugacity coefficient) and an exponential decay composition correction. These two parameters have important thermodynamic implications: their temperature and pressure derivatives are related to the solute's partial molar enthalpy and volume, respectively. When applied to activity coefficients, the same theoretical analysis yields universal relationships for the composition dependence of activity coefficients which can be used as consistency checks for empirical correlations. The relationship between infinite dilution activity and fugacity coefficients can be used to estimate relative solubilities of a given solute in different solvents. Excellent agreement is found when the theoretical expressions are tested with three different binary systems involving a nonvolatile solid solute and a supercritical fluid.
Modeling of coal liquefaction kinetics based on reactions in continuous mixtures. Part I: Theory
Authors: Prasad G. N. , Wittmann C. V. , Agnew J. B. , Sridhar T. 
Published: June 2004

AbstractBased on the concept of reactions in a continuum, a mathematical model has been developed to simulate coal liquefaction kinetics. In an excess hydrogen donor environment, the rate‐limiting reactions are considered to be irreversible cracking reactions involving cleavage of carbon and oxygen linkages. Concurrent evolution of a wide spectrum of products, with an initial rapid formation of species of high carbon and oxygen contents, followed by progressively slower reactions leading to lower carbon and oxygen content species is predicted. Simple lumping functions are employed to obtain conventional lumped pseudocomponents (preasphaltenes, asphaltenes, and oils). Parameter analysis has been carried out.
Turbulent reactive mixing with a series‐parallel reaction: Effect of mixing on yield
Authors: Li K. T. , Toor H. L. 
Published: June 2004

AbstractThe yield of a nonpremixed series‐parallel reaction at complete conversion was measured in a turbulent, tubular‐flow reactor with single and multijet feeds. The yield of the intermediate decreased as mixing was slowed relative to the chemical kinetics, either by decreasing the Reynolds number, or by using a less efficient mixing device, or by increasing the feed concentration.Four models, a modified slab model, a modified stretch model, the Harada mass transfer model, and a new closure model, adequately predict the yield when chemical and mixing kinetics are known from independent measurements of the conversion of acid‐base reactions. Without modification, the original slab and stretch models are unable to account for the earlier observed invariance of conversion to Schmidt number of very rapid, single‐step reactions or to satisfactorily predict the yield of the series‐parallel reaction.
Inhibition of gas hydrates by methanol
Authors: Anderson F. E. , Prausnitz J. M. 
Published: June 2004

AbstractA molecular‐thermodynamic correlation has been developed for calculating the inhibition effect of methanol on the formation of hydrates in moist gas mixtures. Six phases are potentially present in these mixtures: gas, aqueous liquid, hydrocarbon liquid, ice, and hydrate structures I and II. For a given temperature and system composition, the molecular‐thermodynamic method described here allows computation of the hydrate‐point pressure as well as relative amounts and compositions of all coexisting phases. Good agreement is obtained when calculated results are compared with diverse experimental data reported in the literature. The correlation given here may be useful for computeraided design for gas processing and transportation.
Identifiability and distinguishability of fundamental parameters in catalytic methanation
Authors: Walter Eric , Lecourtier Yves , Happel John , Kao Juo‐Yu 
Published: June 2004

AbstractMethods are presented to determine structural identifiability and distinguishability of parametric models. Results are applied to transient isotope tracing of methanation over a nickel catalyst. More meaningful information is obtained in this way about fundamental parameters than is possible by empirical curve‐fitting.
Liquid extraction during drop formation: Effect of formation time
Authors: Heideger W. J. , Wright M. W. 
Published: June 2004

AbstractThis study was designed to evaluate the effects of internal droplet convection on the extraction that occurs during generation of a dispersed phase. A photographic determination of dispersed‐phase controlled mass transfer from liquid droplets in the formation stage demonstrates a strong dependence on formation time. Convection appears to control mass transfer during rapid drop formation, but an abrupt transition in transfer coefficient occurs as time of formation increases. Diffusion calculations overestimate total extraction for long formation times.
Electrooxidation of urea at the ruthenium titanium oxide electrode
Authors: Wright J. C. , Michaels A. S. , Appleby A. J. 
Published: June 2004

AbstractUrea adsorbs on the ruthenium titanium oxide electrode, depressing the observed current. For artificial kidney dialysate concentrations of urea and NaCl (0.50 kg/m3 and 100 mol/m3, respectively), the major electrolysis products are N2, CO2, O2, and H2, and the reaction mechanism is solution oxidation of urea by anodically generated active chlorine. A nitrogen‐yielding direct electrode reaction is observed at high urea concentration (30 kg/m3) and low NaCl concentration (10–100 mol/m3).
Conversion of propylene and butylene over ZSM‐5 catalyst
Authors: Tabak S. A. , Krambeck F. J. , Garwood W. E. 
Published: June 2004

AbstractUsing the zeolite ZSM‐5, new technology has been developed for catalytically oligomerizing light olefins (C3 to C4) to gasoline (C5 to C10) and diesel (C10 to C20) range product. This reaction produces product constrained by both the shape selectivity of the zeolite catalyst and the thermodynamics governing the oligomerization reaction.
Transient behavior of heterogeneous catalytic reactions with educt inhibition
Authors: Truffer M. A. , Renken A. 
Published: June 2004

AbstractUnder periodic operating conditions, the instantaneous rate of the heterogeneous catalytic addition of acetic acid to ethylene can be an order of magnitude higher than at steady state. A real surface, multistep control model takes into account the strong inhibition of the acid to ethylene sorption and describes the steady state and transient behavior quantitatively.
Simplified vent sizing equations for emergency relief requirements in reactors and storage vessels
Authors: Leung J. C. 
Published: June 2004

AbstractSimplified vent sizing equations for emergency relief requirements in reaction kettles and storage vessels are obtained from analytical consideration. Venting modes include homogeneous‐vessel venting, all‐vacor venting, and all‐liquid venting; energy sources due to runaway chemical reactions and external heating are treated separately. The resulting equations have been shown via numerical examples to yield good agreement with detailed computer simulations, both in terms of temperature and pressure histories during venting and in vent size predictions. These equations are generally applicable over a wide range of overpressure situations and reduce to the correct limit at no overpressure. The relative merit of allowing for overpressure in various venting modes can be demonstrated using these equations. Because of their simple forms, requiring only pertinent physical property and thermal data, these equations readily lend themselves to quick but accurate vent sizing predictions.
Local composition model for chainlike molecules: A new simplified version of the perturbed hard chain theory
Authors: Kim Choon‐Ho , Vimalchand P. , Donohue M. D. , Sandler S. I. 
Published: June 2004

AbstractA simple analytical equation for chainlike molecules interacting with square‐well potential is derived by replacing the complicated attractive term in the perturbed hard chain theory (PHCT) of Beret, Donohue, and Prausnitz with a theoretical but simple expression derived by Lee, Lombardo, and Sandler. The resulting simplified perturbed hard chain theory (SPHCT) reproduces both experimental vapor pressure and liquid density data for a number of fluids over a wide temperature and pressure range with good accuracy.The three pure‐component parameters in the SPHCT have been obtained for several n‐alkanes and multipolar fluids. Average errors in predicted vapor pressures and liquid densities, over a wide temperature and pressure range, are about 3 and 4%, respectively. Preliminary mixture calculations indicate that the SPHCT predicts K factors and Henry's constants with reasonable accuracy without the use of any binary parameters.
Uniqueness of solutions to single‐stage isobaric flash processes involving homogeneous mixtures
Authors: Lucia Angelo 
Published: June 2004

AbstractAll single‐stage isobaric flash processes involving multicomponent homogeneous mixtures are shown to have unique two‐phase solutions. No simplifications with regard to nonideal phase behavior are made. The main result for the isothermal, isobaric (TP) case is established with the aid of a different characterization of material stability, the Gibbs‐Duhem equation, and the Cauchy interlace theorem. Results for the other traditional specifications of heat duty and pressure (QP), and total vapor flow rate and pressure (VP) are proved by establishing a one‐to‐one correspondence between the solution sets for TP and QP and the solution sets for TP and VP flash problems, respectively. Construction of these one‐to‐one mappings results in some interesting analysis associated with the appropriate plane curves in the TQ and TV planes. Some new properties of the underlying matrices involved in the phase equilibrium of homogeneous mixtures are presented.
Analysis of gas chromatography pulse dispersion data for the system n‐butane/zeolite nay
Authors: Fu Chen‐Chen , Ramesh M. S. P. , Haynes H. W. 
Published: June 2004

AbstractAn analysis of gas chromatography pulse dispersion data for the system n‐butane/zeolite NaY is presented. The data were analyzed in terms of two models, an intracrystalline diffusion limiting model and a surface barrier model. Both models provided acceptable fits to the pulse dispersion data; however, the temperature dependence of the apparent mass transport parameters strongly suggests that a surface barrier is responsible for the observed transport resistance. The Henry's law constants were independent of choice of model and the isosteric heat of sorption was consistent with literature values.
Optimization of catalytic activity distributions in series and parallel reaction schemes
Authors: Dougherty R. C. , Verykios X. E. 
Published: June 2004

AbstractOptimal activity distributions within nonisothermal porous hetergeneous catalysts for series and parallel reaction networks are determined employing a numerical search procedure based on orthogonal collocation techniques. At high values of the Thiele modulus, a shell profile is found to be optimal at moderate heat of reaction parameters. In certain cases a pendulum effect, in which activity shifts from shell to core and back to shell profiles, is observed with increasing value of the heat of reaction parameters.
A population balance approach to direct‐contact secondary refrigerant freezing
Authors: Byrd L. W. , Mulligan J. C. 
Published: June 2004

AbstractA population balance approach is used in developing an analysis of homogeneous freezing in a brine‐ice slurry by direct‐contact heat transfer to a dispersed secondary refrigerant. Exponential and beta distributions are assumed for the ice crystals and refrigerant droplets, respectively. The effects of freezer pressure (refrigerant temperature), inlet refrigerant drop size, and refrigerant and brine flow rates on well‐mixed freezer characteristics are presented.
Light intensity models for annular UV disinfection reactors
Authors: Suidan M. T. , Severin B. F. 
Published: June 2004

AbstractThe finite‐length lamp model was compared to the infinite‐length lamp model (or parallel radiation model) for annular reactors, specifically for the purpose of calculating average light intensities. Based upon the specified conditions that both models must apply equal energy to a reactor, such as is expected when the average surface flux of energy is measured by a chemical actinometric method, the results for the average intensity were very similar for the two models. Long lamp length and short reactor radius favored conditions where the finite‐length model predicted a slightly higher average intensity than that calculated using the infinite‐length model.The inactivation of f2 virus was predicted in a completely mixed flow‐through reactor using kinetic data obtained from batch reactions. For the particular flow‐through reactor used, very little difference for the average intensity was calculated using the two intensity models. Indeed, predictions of reaction results using both models yielded results well within the range of experimental error.
Vapor‐liquid equilibria from perturbation gas chromatography. Part I: Multicomponent parameter estimation
Authors: Ruff W. A. , Glover C. J. , Watson A. T. 
Published: June 2004

AbstractElution times determined from perturbation chromatography experiments are functions of all sorbing species isotherms through the concentration partial derivatives. Measurements at a sufficient number of appropriate compositions along with isotherm models and adjustable parameters allow reduction of the retention time data to VLE by a nonlinear parameter estimation procedure described in this paper. The method can be implemented for both empirical isotherm models, which can be used to minimize model deficiencies, and for theoretical thermodynamic models, which have extrapolation potential and may require fewer parameters.
Prediction of rate constants for combustion and pyrolysis reactions by bimolecular QRRK
Authors: Westmoreland P. R. , Howard J. B. , Longwell J. P. , Dean A. M. 
Published: June 2004

AbstractBimolecular QRRK (Quantum Rice‐Ramsperger‐Kassel) analysis is a simple method for calculating rate constants of addition and recombination reactions, based on unimolecular quantum‐RRK theory. Input parameters are readily derived, and rate constants and reaction branching can be predicted with remarkable accuracy. Such predictive power makes the method especially useful in developing mechanisms of elementary reactions. Furthermore, from the bimolecular QRRK equations, limiting forms of the rate constants in the limits of low and high pressure are developed. Addition/stabilization is pressure‐dependent at low pressure but pressure‐independent at high pressure, as is conventionally understood for simple decomposition, its reverse. In distinct contrast, addition with chemically activated decomposition has the opposite behavior: pressure independence at low pressure and pressure dependence [as (pressure)−1] at high pressure. The method is tested against data and illustrated by calculations for O + CO → CO2; for H + O2 → HO2 or O + OH; for H + C2H4 → C2H5 or C2H3 + H2; and for H + C2H3 → C2H4 or H2 + C2H2.
Diffusion and catalytic activity studies on resid‐deactivated HDS catalysts
Authors: Johnson B. G. , Massoth F. E. , Bartholdy J. 
Published: June 2004

AbstractThree different pore size CoMo/Al2O3 catalysts, which had been deactivated to the same extent during bench‐scale tests with an atmospheric resid, were examined for coke and metal deposits, diffusivity, and intrinsic activity for hydrodesulfurization, hydrogenation, and hydrodenitrogenation using model compounds. The aged catalysts had very low effective diffusivities and lower intrinsic activities than the fresh catalysts. Both metals and coke deposits were responsible for lowering diffusivity, but activity reduction appears to be predominantly due to metal deposits.
Solids circulation pattern and particles mixing in a large jetting fluidized bed
Authors: Yang Wen‐Ching , Ettehadieh B. , Haldipur G. B. 
Published: June 2004

AbstractMacroscopic behavior of solids circulation in a large jetting fluidized bed was surveyed with a force probe. Particles mixing was studied by pulse injection of tracer particles, and a simple mechanistic model was developed on the basis of the solids circulation pattern observed. The model compares favorably with experimental tracer concentration profiles.
Production of ultrafine metal oxide aerosol particles by thermal decomposition of metal alkoxide vapors
Authors: Okuyama Kikuo , Kousaka Yasuo , Tohge Noboru , Yamamoto Satoru , Wu Jin Jwang , Flagan R. C. , Seinfeld J. H. 
Published: June 2004

AbstractUltrafine spherical titanium, silicon, and aluminium oxide particles were prepared by the thermal decomposition of their alkoxide vapors, produced by evaporation and subsequent heating. High‐concentration ultrafine particles having geometric mean diameters ranging between 0.01 and 0.06 μm and a geometric standard deviation of about 1.4 were obtained by varying the temperatures of the evaporator containing the liquid alkoxides and the reactor furnace, and the flow rate of carrier gas. For furnace temperatures lower than 400°C for TiO2 and 1000°C for SiO2 and Al2O3, the particles obtained were found to be amorphous. The observed changes in the particle size distributions due to changes in operating conditions were compared with those predicted theoretically by solving the discrete‐continuous aerosol general dynamic equation accounting for coagulation and generation of monomer by thermal decomposition. The effect of monomer number concentration on the size distribution of generated particles was found to be qualitatively explained.
Two‐phase flow behavior in the freeboard of a gas‐fluidized bed
Authors: Hamdullahpur F. , MacKay G. D. M. 
Published: June 2004

AbstractAn experimental and theoretical study was conducted to identify the flow behavior of gas and particulates in the freeboard of a gas‐fluidized bed. The axial velocity and turbulence intensity distributions were measured along the centerline and across the freeboard. A laser Doppler velocimeter (LDV) was used for the experiments. A technique based on fluorescence emission was developed to discriminate between gas‐phase and particle‐phase velocity information. The gas phase measurements revealed a strong influence of bubble induced turbulence on gas velocity distribution. The axial particle velocity indicated a two‐stage decay with height. Models were developed to predict centerline gas velocity and transport disengagement height.
Population balance modeling of the dissolution of polydisperse solids: Rate limiting regimes
Authors: Leblanc S. E. , Fogler H. S. 
Published: June 2004

AbstractSignificant errors can result in modeling dissolution processes if the polydispersity of the solid particles is ignored and the sample is treated as a collection of monodisperse spheres having the average size of the mixture. Population balance modeling provides an effective analytical means of predicting the effect of polydispersity on a wide variety of heterogeneous reaction systems including dissolution processes.
Low‐stress hemolysis in laminar blood flow: Bulk and surface effects in capillaries
Authors: Beissinger R. L. , Laugel Jean‐Francois 
Published: June 2004

AbstractHuman blood (blood bank, expired) sheared through stainless steel capillary tubing (508 μm ID) is analyzed for plasma hemoglobin to study the effect of shear‐induced blood damage within the low‐stress regime (stress ≤ 20 Pa). Blood damage results are described in terms of capillary length (related to blood residence time) and wall shear rate for assessing bulk and surface effects. A phenomenological model is proposed to explain these experimental results, obtained over a shear rate range to 7,000 s−1.
Equilibria of nitrogen, oxygen, argon, and air in molecular sieve 5A
Authors: Miller G. W. , Knaebel K. S. , Ikels K. G. 
Published: June 2004

AbstractPure‐component equilibrium data for nitrogen, oxygen, and argon, and multicomponent equilibrium data for air in 20 × 40 mesh 5A molecular sieve were measured at 297.15, 233.15, and 203.15 K and up to pressures of 4 bar. The multicomponent data were analyzed by a statistical thermodynamic model, ideal adsorbed solution theory, an extended Langmuir‐Sips equation, and an extended Langmuir equation. The multicomponent system exhibited nonideal behavior at 233.15 and 203.15 K. Isotherm parameters determined in this work may be useful in the design and evaluation of molecular sieve air separation systems.
Alternating flow model for mass and heat dispersion in packed beds
Authors: Klingman K. J. , Lee H. H. 
Published: June 2004

AbstractThe alternating flow model (AFM) views dispersion in packed beds as a sequence of streamline plugs that must repeatedly split and merge as the bulk fluid traverses the vessel. Thus, the flow in the AFM is ordered, as opposed to the random flow implied by the Fickian analogy. For mass dispersion only, model parameters arise from a priori considerations of packing geometry. Steady state and transient data (5.6 < Dt/dp < 54.4, 100 < Rep < 1,000, gases and liquids) show the AFM to surpass the Fickian analogy (based on correlations for dispersion coefficients) in most cases. Further, it can describe well the radial velocity profile trends in packed beds. For heat dispersion, two additional parameters (heat transfer coefficients) arise that are not functions of packing geometry. Simple correlations for these parameters and the justifications are given. Most of the comparisons made with the literature experimental results show the AFM to be at least as good as the back‐fit Fickian analogy. The AFM should be most useful for packed beds with a relatively small Dt/dp.
A generalized pore model for gas‐solid reactions exhibiting pore closure
Authors: Yu Huei‐Chung , Sotirchos S. V. 
Published: June 2004

AbstractA model of pore structure evolution has been developed for gas‐solid reactions exhibiting pore closure behavior. A cylindrical pore network of constant coordination number is used to represent the porous medium, and both discrete and continuous distributions of pore size are considered. The mathematical model takes into consideration the effects of pore overlapping and nonuniform pore growth, and follows the formation of inaccessible volume in the interior of the reacting particles by use of percolation theory concepts. The model is applied, along with an appropriate diffusion and reaction model, to the investigation of the transient behavior of calcined limestone particles in an environment of sulfur dioxide.