Adsorptive Drying of Isopropyl Alcohol on 4A Molecular Sieves: Equilibrium and Kinetic Studies

Abstract

Batch equilibrium and kinetic studies were carried out for adsorption of water from aqueous solution of isopropyl alcohol on 4A molecular sieves (cylindrical pellets of 1.8 mm diameter). Equilibrium data obtained were rectangular in shape. The adsorption capacity was about 0.25 g water per gram dry adsorbent. This corresponds to 0.29g water/cm³ of molecular sieve pellets. The effect of temperature on equilibrium behavior was not significant in the temperature range 20 to 70°C. Batch kinetic studies were carried out at room temperature. Differential equations for the uptake of water by biporous cylindrical particles were written and solved numerically by the finite forward difference method. The macropore diffusion coefficient was estimated by assuming the macroporosity of the pellet to be 0.35 and the value of tortuosity to be 3. The diffusion coefficient for micropores was obtained by matching the computed uptake curve with the experimental data. Assuming the average radius of microspheres to be 1 μm, the diffusion coefficient for micropores was found to be 0.4 × 10^?12 cm²/s.