G.E.H. Joosten

Enhancement of gas-liquid mass transfer by a dispersed second liquid phae

Abstract From experiments in a stirred cell contactor with flat gas-liquid interface, it is shown that the rate of mass transfer of oxygen into an aqueous solution can be enhanced by the presence of small amounts (0.5–1 vol%) of a dispersed organic phase (e.g. hexadecane, decane, decanol or cyclohexane), provided that the droplet diameter is in the order of or smaller than the film thickness ( D/k L ) and the solubility of oxygen in the organic phase is larger than in water. A simple model is proposed that predicts the experimentally observed enhancement factors with reasonable accuracy.

KINETICS AND EQUILIBRIA OF THE HYDRATION OF PROPENE OVER A STRONG ACID ION EXCHANGE RESIN AS CATALYST

The kinetics and equilibria of the direct hydration of propane over a strong acid ion exchange resin (CSP ex AKZO) were studied. The experiments were carried out under such conditions that apart from the. solid resin catalyst only one waterrich liquid phase was present in the reactor. It was found that besides 2-propanol a certain amount of diisopropylether was formed. Other side products were not observed. The kinetics of the t-propanol and diisopropylether formation reactions can well be represented by a scheme in which the isopropylcarbenium ion is the intermediate. The numerical values of the rate constants and equilibrium constants involved have been determined. The presence of 2-propanol was found to lead to a larger reduction in reaction rate than expected by the approach of chemical equilibrium. This is ascribed to a solvent effect of Zpropanol. It was found that intraparticle diffusion limitations only occur at temperatures above 130°C when ion exchange resin particles of the normal commercial size (approximately 0.8 mm dia.) are used.

GAS-ABSORPTION WITH AUTOCATALYTIC REACTION AND SIMULTANEOUS DESORPTION OF THE CATALYST

Abstract Enhancement factors for gas absorption with autocatalytic reaction and simultaneous desorption of the catalyst have been calculated for the film and the penetration model. The enhancement factors both models virtually agree and are considerably larger than those for non-autocalytic reactions at the same values of the Hatta number and the other parameters. A simple approximate method is given to calculate the enhancement factor for the present type of reaction. Experiments were carried out in a stirred cell on the chlorination of cyclohexanone. In this reaction hydrogenchloride is a volatile reaction product which catalyses the reaction. The experimentally determined enhancement factors are in good agreement with the calculated ones.

EFFECT OF SOLVENT ON THE HYDRATION OF 2-METHYL- PROPENE IN SOLUTIONS OF p-TOLUENESULFONIC ACID AND POLY(STYRENESULFONIC ACID)

Results are reported of a kinetic study on the hydration of 2-methylpropene at 25.0 °C in solutions of p-toluenesulfonic acid and poly-(styrenesulfonic acid) in mixtures of 1,4-dioxane or sulfolane and water. Both cosolvents have a large influence on the rate of hydration. For sulfolane the rates are higher than for 1,4-dioxane, in spite of the higher solubility of the alkene in 1,4-dioxane/water mixtures. For the reactions catalyzed by p-toluenesulfonic acid, the variation of the pseudo first-order rate constant as a function of the solvent composition is explained in terms of the Hammett acidity function and an examination of the influence of the solvent on the initial- and transition-states of the reaction. Contrary to the rates of the reactions catalyzed by p-toluenesulfonic acid, the rates per equivalent of acid groups are independent of the acid concentration for the reactions catalyzed by poly(styrenesulfonic acid). This is explained by assuming that solutions of poly(styrenesulfonic acid) are divided into an ordered polymer-rich pseudo-phase and a highly disordered pseudo-phase in which the polymer concentration is very low. It appears that for the same overall mol fraction of the cosolvent, the amount of cosolvent in the ordered pseudo-phase is considerably higher for the rather polar sulfolane than for the almost non-polar 1,4-dioxane. The results of this study will give insight into the influence of the solvent composition on the catalytic activity of sulfonated polystyrene/ divinylbenzene-type cation exchange resins, which are used as catalysts for the hydration of lower alkenes on an industrial scale.

Effect of solvent on the kinetics of the hydration of 2-methylpropene catalyzed by strong acid ion exchangers

Abstract The hydration of 2-methylpropene, catalyzed by strong acid ion exchange resins, was investigated in solvent mixtures of water and either 1,4 dioxan or sulfolane at 25.0 °C. A gel type, an intermediate type and a macroporous resin were all investigated. It appeared that the macroporous resin is the most active catalyst for almost all solvent compositions investigated. The influence of the solvent composition on the rate of the hydration reaction can be explained by the acidity of the acid groups of the resin and by the distribution coefficient, X, of the alkene defined as the concentration ratio at equilibrium between the resin phase and the liquid phase surrounding the catalyst particles. The solvent also determines the value of the distribution coefficient, λ, of the alkene between the resin phase and bulk liquid. For one resin this effect was determined quantitatively. A complicating effect is the difference in the composition of the solvent in the resin phase and in the bulk liquid. For mol fractions of the cosolvent above 40%, it appeared that the concentration of sulfolane in the resin phase is considerably larger than that of 1,4-dioxan. As a consequence, the distribution coefficient of the alkene over the resin phase and the surrounding liquid is much higher for mixtures of sulfolane and water than for mixtures of 1,4-dioxan and water. This results in considerably higher hydration rates for sulfolane-water than for the 1,4-dioxan-water mixtures of comparable compositions.

On the reaction of potato starch with isocyanates

Abstract The reactions of potato starch in aqueous suspension with some isocyanates were investigated. In contrast to previously reported results we found that no starch carbamates were formed but only the corresponding urea compounds. These urea compounds were physically bound to the potato starch and could be washed from the starch by several organic solvents.

On the interpretation and identification of simultaneous-equation models☆

In this paper attention is paid to the interpretation of simultaneous-equation models. By choosing a specific variance-covariance structure of the disturbances each equation can be given a conditional expectation interpretation. In this case there is no identification problem. The relation to the REID-systems (introduced by Wold) and to the Cowles Commission interpretation is pointed out. The ideas are illustrated by means of three simple models.

SOME REMARKS ON THE UNDERSIZED SAMPLE PROBLEM IN ECONOMETRICS

Abstract This paper discusses three approaches to the problem of undersized samples: the estimable function, the generalized inverse and the principal component method. It turns out that the k -class estimation methods amount to ordinary least squares if use is made of estimable function or generalized inverses. The generalized inverse approach is a special case of the estimable function approach and of the principal component solution.