Separation and Purification Technology 64 (2008) 78–87 Contents lists available at ScienceDirect Separation and Purification Technology journal homepage: www.elsevier.com/locate/seppur Pervaporation study for different binary mixtures in the esterification system of lactic acid with ethanol Patricia Delgado, María Teresa Sanz ∗ , Sagrario Beltrán Department of Chemical Engineering, University of Burgos, 09001 Burgos, Spain article info Article history: Received 10 January 2008 Received in revised form 16 July 2008 Accepted 4 August 2008 Keywords: Pervaporation PERVAP ® Esterification Lactic acid Ethyl lactate abstract 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. The effects of feed composition and operating temperature on the membrane performance were analyzed. Two differ- ent commercial hydrophilic membranes PERVAP ® 2216 and PERVAP ® 2201 were tested for the system water/ethanol. PERVAP ® 2201 membrane was chosen for further experiments due to its better selectivity towards water. The permeation flux, as well as permeances, was found to increase with water feed con- centration. The influence of temperature on the permeation flux can be described by an Arrhenius-type expression. However, not a great influence of temperature on the permeance was found. Separation factor and selectivity were found to depend on water feed concentration but not a clear influence of temperature was found on these two parameters. © 2008 Elsevier B.V. All rights reserved. 1. Introduction Lactic acid esters are powerful high-boiling solvents that are biodegradable and non-toxic. Lactate esters can also be used in pharmaceutical preparations, food additives and fragrances. Cur- rent production of lactate esters by esterification of lactic acid with the corresponding alcohol suffers from low conversion and purity [1,2]. Esterification reactions are characterized by thermodynamic limitations on conversion. Higher ester yields can be obtained by shifting the reaction towards products formation by hybrid pro- cesses such as reactive distillation and pervaporation-aided reactor instead of using a large excess of one of the reactants, usually the alcohol. Pervaporation has gained increasing attention in many chemical processes as an effective energy-saving membrane tech- nique. In this regard, the integration of a pervaporation process into conventional esterification processes is attractive because the sep- aration is based on the transport of the components through the membrane, which is determined by the solubility and diffusivity of the components to be separated and it is not limited by the rel- ative volatility of the components as in distillation processes [3]. In combination with a reactor, pervaporation is used to continu- ously remove one of the reaction products to shift the equilibrium reaction to higher yields; in most cases the removed product is water. ∗ Corresponding author. Tel.: +34 947 258810; fax: +34 947 258831. E-mail address: tersanz@ubu.es (M.T. Sanz). For a correct synthesis and design of reaction-pervaporation hybrid processes, reliable information on kinetic reaction and per- meation performance is needed. In a previous paper [2] a detailed kinetic study was carried out for the heterogeneous ion exchange (Amberlyst 15) catalyzed synthesis of ethyl lactate: CH 3 CHOHCOOH + CH 3 CH 2 OH ⇆ CH 3 CHOHCOOCH 2 CH 3 + H 2 O Additionally, vapor liquid equilibrium for the quaternary mix- ture involved in the process was determined in a previous work [4] to obtain reliable UNIQUAC interaction parameters to take into account the non-ideality of the liquid mixtures. The main aim of this work was to study systematically the effect of feed temperature and water feed composition on the permeation characteristics for different binary mixtures involved in the synthe- sis of ethyl lactate. The mixtures considered in this work were the following: water/ethanol, water/ethyl lactate and water/lactic acid. The results obtained have been compared in terms of the perme- ation flux, permeance, separation factor and selectivity obtained for the different mixtures. Two commercial membranes, PERVAP ® 2216 and PERVAP ® 2201, were tested for water/ethanol mixtures. Although both membranes were water selective, higher fluxes and separation factors were obtained for PERVAP ® 2201. Consequently, this membrane was chosen to perform pervaporation experiments for the rest of the binary mixtures. Additionally the swelling behav- ior of the membrane PERVAP ® 2201 was studied for the different components at room temperature. 1383-5866/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.seppur.2008.08.002