摘要:

AbstractPendant drop tensiometry enhanced by video‐image digitization is shown to be a useful tool for the experimental measurement of the relaxation in interfacial tension due to the adsorption of surfactant at a fluid interface. Using this method, profiles of the relaxation in surface tension of a diffusion‐controlled, nonionic polyethoxy surfactant were measured. A diffusion coefficient was computed by comparing these profiles with numerical solutions of the bulk surfactant diffusion equation and a Frumkin equilibrium adsorption isotherm. This comparison was made for the entire relaxation period. This method establishes a more reproducible diffusion coefficient than current techniques that utilize only the short‐ or long‐time parts of the relaxation spectrum. In addition, lower bounds on the kinetic constants for the sorption process are inferred for the polyethoxy surfactant used by comparing numerical solutions of mixed diffusion and surface kinetic transfer with the diffusion‐limit

ISSN:0001-1541    

DOI:10.1002/aic.690361202

出版商:American Institute of Chemical Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractA combined experimental and theoretical investigation of the effect of forced feed composition cycling for CO oxidation on platinum has been performed. A novel approach to forced composition cycling was examined, in which the phase angle between the two input streams was varied. Reaction rate enhancement is shown to occur, and by varying the phasing of the feed streams it is possible to achieve a global maximum in the time‐average reaction rate. This phenomenon can be explained quantitatively by a model based on an adsorbate‐induced phase change of the Pt surface combined with CO adsorption self‐exclusion. This mathematical model can also quantitatively describe the complex steady‐state behavior (uniqueness‐multiplicity transitions) observed for this reaction. The predictions of the model have been validated further through a detailed experimental study of the effects of feed flow rate, temperature, size of catalyst charge, and cycling frequency on the instantaneous and time‐average conversions during forced cycling of the feed

ISSN:0001-1541    

DOI:10.1002/aic.690361203

出版商:American Institute of Chemical Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractFormaldehyde is one of the most important intermediate products of the chemical industry. Due to its high reactivity, it is commonly handled in aqueous or methanolic solutions. In these solutions, formaldehyde is dissolved chemically. Therefore, modeling thermodynamic properties of aqueous and methanolic formaldehyde‐containing mixtures require the consideration of chemical reactions and physical effects. A recently published physico‐chemical model (Maurer, 1986) for the description of vapor‐liquid equilibria of these systems is tested and improved on the basis of about 140 new experimental data points for mixtures containing formaldehyde, water, methanol, and trioxane at temperatures between 320 and 380 K and pressures below 100 kPa. Improvements are achieved by fitting some of those binary interaction parameters, which formerly had to be estimated due to the lack of experimental data. The revised model is able to reliably predict vapor‐liquid equilibria in multicomponent formaldehyde‐containing

ISSN:0001-1541    

DOI:10.1002/aic.690361204

出版商:American Institute of Chemical Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractWastewater of electrodeposition painting process contained diisopropanolamine, unknown three paints, and solvents (butylcellosolve and/or ethylcellosolve). The recovery of the amine and paints from the real wastewater by adsorption on an H‐form strong acid ion exchanger appeared feasible technically and economically.Equilibrium isotherms and breakthrough curves have been determined experimentally. The selectivity for the amine adsorption on the resin was fairly high. Solvents were not adsorbed on the resin. The components of the wastewater showed typical breakthrough curves for multicomponent system. Theoretical breakthrough curves and intraparticle effective diffusivities of the amine were determined from the analytic solution for rectangular isotherm in the single‐component system. Experiments of adsorption, elution and regeneration also have been repeated. The amine and paints adsorbed on the resin were eluted completely by NaOH aqueous solution. The adsorption capacity of the amine did not change with repeat times, and the intraparticle effective diffusivity of the amine was constant after the second cy

ISSN:0001-1541    

DOI:10.1002/aic.690361205

出版商:American Institute of Chemical Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractFor less labor‐intensive, larger‐scale, and more efficient production of D‐[1‐13C] glucose and other labeled monosaccharides using the cyanohydrin reduction reaction, an automated reactor was designed, constructed, and tested. A suitable vessel and all ancillary and control equipment were fabricated, or otherwise obtained, and the apparatus was controlled with a microcomputer program written in BASIC. Running without manual intervention, the yields for the condensation reaction of D‐arabinose with KCN and the recovery of the excess cyanide were high (>90%), and the resultant aldononitriles were reduced to product aldoses with little reduction of the intermediate imines to amines. The reduction rate could be improved by controlling pH between 2–4 and by agitation speeds>250 rpm, while no improvement resulted from the use of high hydrogen pressures [>129 kPa (4 psig)]. Reduction reactions conducted in the presence of formic acid (to regulate pH) suggest that formic acid acted as a cored

ISSN:0001-1541    

DOI:10.1002/aic.690361206

出版商:American Institute of Chemical Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractRecent procedures developed by Heidemann (1990) and by Michelsen (1990a, b) enable us to formally incorporate excess Gibbs energy model parameters into a fully consistent equation of state, cith accurate reproduction of the behavior of the excess Gibbs energy model at atmospheric pressure.This paper investigates the ability of the mixing rules proposed by Michelsen to predict high‐pressure phase equilibrium, when used in combination with the parameter table of modified UNIFAC. Considering that a group contribution method is used for the excess Gibbs energy and that model parameters are extrapolated over a 200 K temperature interval, quite satisfactory results are obtained for the mixtures investigate

ISSN:0001-1541    

DOI:10.1002/aic.690361207

出版商:American Institute of Chemical Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractNonisothermal inflation of a viscous annular parison and its cooling and solidification before and upon wall contact are analyzed by solving the unsteady momentum and energy conservation equations. The algorithm simultaneously determines the flow field and temperature distribution within the parison together with the moving surfaces at every time step. Results of the present study indicate that the inflation rate is increased as a result of higher temperature within the parison. However, the instantaneous shape of the parison and the final thickness variation upon mold contact remain virtually unchanged. Due to the temperature dependence of physical properties, the critical factor during inflation is initial temperature distribution within the parison. Inflation resulting in full attachment to a confining mold wall takes only a small fraction of the time required to cool the material to the ambient gas temperature. The transient calculations illustrate how computer simulations may be used to improve design of blow molding operations, and they are in good agreement with available experiments.

ISSN:0001-1541    

DOI:10.1002/aic.690361208

出版商:American Institute of Chemical Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractThe associated perturbed‐anisotropic‐chain theory (APACT) has been applied to treat multicomponent mixtures, in which components exhibit Lewis acid‐base interactions. Mixtures of amphoteric molecules (such as alcohols), acidic molecules (such as chloroform), and basic molecules (such as ketones) as well as nonassociating components (diluents) are treated. The acid‐base version of the perturbed‐anisotropic‐chain theory (ABPACT) is a closed form equation of state that takes into account explicitly dispersion interactions, polar interactions, and hydrogen bonding interactions between components that self‐associate or solvate. The equation fits binary VLE mixtures quite accurately. Calculated results also are compared with those obtained from the Peng‐Robinson equation of state, UNIFAC and the original APACT. In all cases where there are mixtures of associating components, the ABPACT gives a better fit of experimental data than these

ISSN:0001-1541    

DOI:10.1002/aic.690361209

出版商:American Institute of Chemical Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractA model of the reaction between SO2and calcium‐based slurries is presented. The model is coupled with an extensive model of the evaporation process and considers external SO2mass transfer and liquid‐phase mass transfer of dissolved sulfur and calcium species in both the film surrounding the calcium particles and the bulk liquid phase. The model assumes that particles do not circulate within slurry droplets and that evaporation results in an accumulation of particles at the droplet surface that causes a shift in the controlling mechanisms. Agreement between the model and data available in the literature is excell

ISSN:0001-1541    

DOI:10.1002/aic.690361210

出版商:American Institute of Chemical Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractThe effect of shear‐thinning rheology on the spatial growth of waves in multilayered flow down an inclined plane is modeled, utilizing the Carreau viscosity constitutive equation. It is shown that waves associated with the free surface propagate as if they were in a Newtonian system, where the viscosity is some average of the varying viscosities in the shear‐thinning layer. This averaging is due to the global effects of shear thinning, such as changes in velocity profile and film thicknesses. In contrast, waves that are associated with the interfaces between adjacent fluid layers are largely affected by the local interfacial viscosities; wave propagation is not governed by some average Newtonian viscosity across the layer. It is found that shear‐thinning rheology can either increase or decrease the growth of waves associated with a fluid‐fluid interface, compared with a purely Newtoni

ISSN:0001-1541    

DOI:10.1002/aic.690361211

出版商:American Institute of Chemical Engineers    

年代:1990

数据来源: WILEY