摘要:

AbstractThe thermolysis of benzylphenylether (BPE) was examined at 320°C in liquid, vapor, and supercritical methanol phases as a probe of the reaction mechanism. Toluene and phenol were the major products in all cases, but observed selectivities were dependent upon the reaction phase. Isotopic labeling experiments demonstrated that methanol participated in the reaction network as a hydrogen donor through a free‐radical mechanism. These results are consistent with free‐radical steps for neat BPE primary pyrolysis that include BPE fission followed by hydrogen abstraction and radical recombination reactions. A detailed set of 21 free‐radical steps quantitatively explains the dependence of the selectivity and conversion on the phase be

ISSN:0001-1541    

DOI:10.1002/aic.690360802

出版商:American Institute of Chemical Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractThe direct‐contact heat transfer to a dispersed population of immiscible evaporating droplets is analyzed. Also studied is a population balance formulation for the distribution of two‐phase bubbles, which is similar to that utilized in particle and droplet dispersion analysis and is capable of including bubble coalescence and break‐up. It is shown that the method of classes is useful particularly in solving such problems when the growth functions are size‐ and time‐dependent and nonquadratic. The method is applied to a liquid cool‐down, representing the initial chilling stage of a direct‐contact batch crystallizer or cold‐storage unit wherein a vessel containing a liquid is chilled by injecting a dispersion of refrigerant droplets. Transient bubble population characteristics, volumetric heat transfer coefficient, total heat transfer, and liquid temperature are predicted, along with the liquid ref

ISSN:0001-1541    

DOI:10.1002/aic.690360803

出版商:American Institute of Chemical Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractA mathematical model of copper plating of a through‐hole is developed which relates uniformity of deposition to bulk electrolyte composition, applied potential difference, aspect ratio, through‐hole diameter, and deposition kinetics. The electrochemical transport equations governing plating in a through‐hole are solved assuming that the fluid within the through‐hole is stagnant. Conditions for uniform plating are determined both for Butler‐Volmer kinetics considering the effects of dissociation of bisulfate ions in the electrolytic solution and for kinetics limited by complexation of cupric ions with an adsorbed neutral additiv

ISSN:0001-1541    

DOI:10.1002/aic.690360804

出版商:American Institute of Chemical Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractThe study of interference effects is of fundamental importance in understanding multicomponent chromatography. In this work, a displacement effect is examined and shown to be able to explain the dominating interference effects in three major modes of chromatography—frontal, elution, and displacement—involving competitive isotherms. It is concluded that the concentration profile of a component usually becomes sharper due to the displacement effect from another component, while the concentration front of the displacer is usually diffused. Five factors that escalate the displacement effect in multicomponent elution were investigated. A binary elution with a competing modifier in the mobile phase was also discussed. This study was carried out using computer simulations based on a general nonlinear multicomponent rate equation model that considers axial dispersion, external mass transfer, intraparticle diffusion, and Langmuir isotherms. The use of the general model helps the visualization of the multicomponent interactions in chromatography under mass transfer conditi

ISSN:0001-1541    

DOI:10.1002/aic.690360805

出版商:American Institute of Chemical Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractThe analysis in this paper shows the relationship between molecular resolution in supercritical fluid chromatography (SFC), and certain divergent thermodynamic properties of solutes dissolved in near‐critical fluids. This divergence is most pronounced in the near‐critical regime, leading to the hypothesis that this region provides most promise for heightened molecular resolution, which lies at the heart of analytical and separation technologies.A thermodynamic model for representing capacity factor data in SFC is proposed, spanning a wide density range. The model uses a perturbed hard sphere equation for the fluid phase and lattice concepts for the stationary phase. In addition, data are presented for a number of systems and discussed in terms of the analysis provided. For an isomeric system, the data shows that resolution between species increases with the onset of retrograde behavior, resulting in a distinct maximum po

ISSN:0001-1541    

DOI:10.1002/aic.690360806

出版商:American Institute of Chemical Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractA percolation model of foam mobilization in porous media is developed. This model indicates that there is a minimum pressure gradient or, equivalently, a minimum gas velocity required to initiate mobilization of foam. As a result, for most foam enhanced oil recovery processes, where the surface tension is not low, deep foam penetration depends on propagation of foam formed at a high pressure gradient near the well. Low surface tension makes mobilization of CO2foams feasible, however, at pressure gradients found throughout much of the formation in a typical field application. The theory further predicts, and data confirm, that the minimum velocity for foam mobilization during steady flow of liquid and gas decreases as injected liquid volume fraction increases. The theory suggests a better strategy for foam generation: alternate injection of small slugs of liquid and gas.

ISSN:0001-1541    

DOI:10.1002/aic.690360807

出版商:American Institute of Chemical Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractA model for coal thermal depolymerization is described and used to predict molecular weight distributions (MWD) of primary coal pyrolysis liquids. The model assumes that rupture of kinetically similar bonds in the coal is the preferred pathway for release of oligomers which ultimately become tars or extractables. The analysis provides the liquids MWD as a probability function of finding different oligomers composed of whole integer numbers of monomers and it is in excellent qualitative agreement with measured MWDs of coal pyrolysis liquids. The predicted MWDs are of the form of the gamma distribution function (GDF), and its parameters are interpreted in terms of the postulated chemistry of coal thermal depolymerization. Consequently, successful empirical correlations of experimental data on coal pyrolysis liquids MWDs with the GDF are better understood. Thus a protocol is provided to predict MWDs of pyrolysis liquids from knowledge of coal molecular structure.

ISSN:0001-1541    

DOI:10.1002/aic.690360808

出版商:American Institute of Chemical Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractThe Bodenstein approximation for trace‐level intermediates is used to reduce multistep reaction‐kinetic networks of arbitrary topology and size to simpler forms with only pseudosingle steps between nodes and to derive explicit equations for formation or consumption rates of end members. Networks with nontrace intermediates or steps of higher orders in intermediates must be broken at the respective steps into portions to which the procedure can then be applied separately. A recipe is provided with which rate and yield‐ratio equations are readily compiled for networks of arbitrary configuration and complexity. The method is illustrated with an example of a reaction of industrial int

ISSN:0001-1541    

DOI:10.1002/aic.690360809

出版商:American Institute of Chemical Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractA systematic procedure is developed for the simultaneous synthesis of primary transfer mass‐exchange networks and their associated mass‐exchange regeneration networks. The purpose of the primary transfer network is to preferentially transfer certain species from a set of rich streams to a set of lean streams. The regeneration network aims at regenerating any recyclable lean stream. The proposed procedure deals with the problem in two stages. In the first stage, a mixed‐integer nonlinear program is solved to minimize the cost of mass‐separating and regenerating agents. The solution of this program provides the location of the pinch points as well as the optimal flow rates of all the lean and the regenerative streamswithout any prior commitment to the network structure. In the second stage, a mixed‐integer linear program is solved to minimize the number of exchangers in both networks. An example problem with industrial relevance is solved to elucidate the merits offered by the devised synthesis

ISSN:0001-1541    

DOI:10.1002/aic.690360810

出版商:American Institute of Chemical Engineers    

年代:1990

数据来源: WILEY

摘要:

AbstractContinuous displacement chromatography separations are obtained using a continuous annular chromatograph (CAC). The apparatus consists of a rotating annular bed. At fixed positions at the top of the bed, four solutions are continuously supplied: the feed mixture to be separated, a displacer solution, a regenerant, and a rinse. The four solutions flow concurrently through the bed with little mixing. If the bed is sufficiently deep, a fully developed displacement train forms and the separated components are continuously recovered at various angular locations at the bottom of the bed. Mixtures of amino acid were separated by cation exchange displacement chromatography in a laboratory‐scale CAC. Separation and concentration of dilute mixtures was obtained with a continuous separation performance comparable with the performance of a conventional chromatograph. A mathematical model is developed to describe the separation and provide guidance in design and optimizatio

ISSN:0001-1541    

DOI:10.1002/aic.690360811

出版商:American Institute of Chemical Engineers    

年代:1990

数据来源: WILEY