Pervaporation of mixtures involved in the esterification of lactic acid with ethanol
Advancing the chemical engineering fundamentals
Membranes and Membrane Science (T2-8P)
Keywords: Pervaporation, esterification, lactic acid, ethanol
Lactic acid esters are non-toxic and biodegradable materials, and can be used as detergents and powerful high boiling solvents or varnishes. Ethyl lactate in particular is used as food additive, perfumery, flavor chemicals and solvent. Production of methyl, ethyl, isopropyl and n-butyl lactates is usually carried out by conventional esterification of lactic acid with the corresponding alcohol.
New technologies have been developed to yield lactate esters from carbohydrate feed stocks via esterification using reactive distillation or pervaporation-aided reactors. Pervaporation has gained increasing attention in many chemical processes as an effective and energy-saving membrane technique. In combination with a reactor, pervaporation is used to continuously remove one of the reaction products to shift the equilibrium reaction to higher yields. In most cases the removed product is water.
In this work, pervaporation experiments were performed for some binary mixtures involved in the esterification of lactic acid with ethanol: water/ethanol, water/ethyl lactate and water/lactic acid. Moreover the influence of adding a third component to the feed is examinated.
The experiments were carried out with a laboratory pervaporation set-up with a test cell unit (182 cm2 membrane area, Sulzer Chemtech) with two different commercial hydrophilic membranes PERVAP® 2201 and PERVAP® 2216 supplied by Sulzer Chemtech.
The effect of pervaporation temperature and feed composition on the pervaporation flux, permeances, and selectivity of the membranes has been investigated. The feed composition has large influence on flux and selectivity. It has been observed that the permeation rate increases as the feed water concentration increases. Both membranes showed to be water selective as indicated by its higher flux when compared to the other components. Selectivity decreases as the water concentration in the feed increases probably due to a higher swelling of the membrane. Pervaporation was promoted with increasing temperature thus favoring the operation at high temperatures to optimize separation performance. The temperature dependence of the pervaporation behavior has been discussed in terms of Arrhenius activation energy.
Presented Tuesday 18, 13:30 to 15:00, in session Membranes and Membrane Science (T2-8P).
