No abstract

No abstract

No abstract

Models are developed for isothermal desorption in a fixed bed of adsorbent particles. While more general models require numerical solution of the governing equations, two practically important cases have analytical solutions: 1) an equilibrium desorption model where the rate of desorption is controlled by external and intraparticle mass transfer; and 2) a kinetic model where external and intraparticle mass transfer and a first-order irreversible desorption step control the overall process.Recent experimental data (Tan and Liou, 1988) for the desorption of ethyl acetate from activated carbon with supercritical carbon dioxide are found to fit the local-equilibrium model. Data for the effect of temperature on fractions desorbed indicate a reversal of the temperature dependence of the adsorption isotherm as the supercritical pressure is increased. This phenomenon is analogous to the observed cross-over region for the effect of temperature on the solubility of a solid at supercritical conditions.

No abstract

No abstract

Intrinsic rates of isobutene hydration to tert-butyl alcohol on Amberlyst-15 particles were measured to establish a rate equation in a solvent-free, liquid-phase system. The ranges of temperature and concentration are those likely to be found in a multiphase reactor, such as trickle bed or slurry type. Although inhibition by water may also be present, the effect of TBA is far more significant. Thus, the alcohol is found to inhibit the rate more than expected from the values of the equilibrium constant for the hydration reaction, determined in separate experiments. Various rate expressions, including that derived from the accepted hydration mechanism, are tested to account for product inhibition. Extreme care has been put in ascertaining the effects of internal and external mass-transfer resistances, by use of suitable derived criteria.

No abstract