paper

Chem. Eng. Technol. 2006, 29, No. 11, 1340–1346

Separation of Ethylene Glycol/Water Mixtures  using NaA Zeolite Membranes

^{Omid Ghaffari Nik  Toraj Mohammadi}

Introduction                                                     

zeolite membranes has made it possible to overcome the above The production of organic solvents (alcohols, ketones, esters, limitations of hydrophilic polymeric membranes. etc.) includes their dehydration as the final stage. In common Zeolites are hydrated aluminosilicates composed of crystalline processes, the dehydration of these organic solvents is carried structure with molecular sieving properties and are inorganic

out by a power consuming distillation combined with addi-materials with thermal, chemical and mechanical stability. They tional chemical treatment [1]. also have nanopores, and as a result, zeolite membranes are suit-

PV is selective evaporation of one component in a liquid able for molecular sieving separation or the PVof organic solu­mixture by a membrane, which is in direct contact with the tions at high temperatures [3]. NaA zeolite membranes (with mixture. A vacuum is maintained on the permeate side of the 0.4 nm pores) offer significant potential as a dehydration agent membrane while the feed side of the membrane is kept at at-with a high separation factor and permeation flux, together with

mospheric or elevated pressure, such that a pressure difference high chemical and thermal stability. is created across the membrane, which is driving force of the EG is an odorless liquid and is completely miscible with PV process. Due to the fact that only a fraction of the liquid water and many organic liquids. It is primarily used as anti-feed is vaporized in PV, its energy efficiency is greater than that freeze and in the manufacture of polyester fibers and films. At

of competing, distillation technology [2]. present, EG is commercially produced by direct oxidation of Although the dehydration of solvents by hydrophilic poly-ethylene to ethylene oxide followed by the hydrolysis of ethyl­meric PV membranes is a well-established technology, a major ene oxide [4].

drawback of these membranes is their limited solvent and tem-In the hydrolysis reaction, excess water is added to ethylene perature stability and their possible unsuitability for applica-oxide to increase the EG content and to decrease the diethylene tions involving high water concentrations.