Study On Purification Of Small Amount Of Water From Organic Solvent By Adsorption

Organic solvents play an important role in the industry now and are often used in many fields. To meet with the industrial demand, the purification of the solvents is usually required in some fields. The organic solvents inevitably are intermixed with other undesirable materials, which seriously affect on the products'qualities. For instance, water is widespread in many important products and difficult to be removed. So the purity of the water from solvents is very important in the process of the production. Adsorption dehydration is low energy-consuming and harmless to environment. So it is promising technology involving separation and segregation.In this paper the adsorption performance of small amount of water in tetrahydrofuran(THF), 1,2-dimethoxyethane(DME) and isopropanol(IPA) on 4A molecular sieves were studied. Adsorption isotherms for these three systems were measured respectively at different temperatures. The data were fitted well with the models of Langmuir and Freundlich. According to the parameters, the results indicate that the adsorptive amount decrease with the temperature raising. The results are in agreement with tendency,which the raising temperature is not in favor of adsorption. From adsorption equilibrium data of DME, the adsorption heat was calculated according to the equation of Clausius-Clapeyron. The calculated adsorption heat was 26.9kJ/mol at the range of the concentration. The result indicated that the adsorption of water on 4A molecular sieves was physical adsorption.On the base of static adsorption, the Crank monopore model was fitting well with the kinetic data of the three systems. The effective diffusion coefficients of the tetrahydrofuran with small amount of water were 7.6×10^-8 and 1.101×10^-7cm²/s at 295K, 303K. The diffusion coefficients of water in DME at 283K and in IPA at 290K were 1.4135×10^-7 and 3.539×10^-8 cm²/s. The diffusion coefficients were at the magnitude of 10^-7 - 10^-8, which indicated the adsorption of three systems belonged to crystal diffusion limit.The adsorption dynamic characteristics of fixed-bed for these three systems were...