Communication Sugaring-Out Separation of Acetonitrile from Its Aqueous Solution The separation of acetonitrile (ACN) from an ACN-water azeotrope is of particu- lar interest to industrial chemists and process engineers. In the work reported in this article, sugaring-out, a new phase separation method is reported and used to obtain high purity ACN from an ACN-water mixture. With the addition of a mono-sugar (glucose, xylose, arabinose or fructose) or a disaccharide (sucrose or maltose) into an ACN-water mixture, a phase separation is observed if the sugar concentration exceeds a threshold. The upper phase is rich in ACN while the low- er phase is rich in water. The ACN concentration in the upper phase increases when more sugar is added into the ACN-water mixture. When the glucose con- centration is > 35 g/L, the ACN concentration in the upper phase is > 40%. In the Sudan I extraction test with a glucose-triggered two-phase system, an extrac- tion rate of > 80 % is achieved when the glucose concentration is greater than 25 g/L. Keywords: Acetonitrile, Dehydration, Extraction, Phase separation, Separation, Sugaring-out Received: January 7, 2008; accepted: September 24, 2008 DOI: 10.1002/ceat.200800003 1 Introduction Acetonitrile (ACN) is widely used as a solvent or starting ma- terial for the syntheses of organic and inorganic chemicals [1]. It also finds applications in liquid chromatography and elec- trochemistry [2], as well as in the enhancement of catalytic efficiency of enzymes [3]. Crude acetonitrile typically contains 43.6 % water and is obtained as a co-product in the produc- tion of acrylnitrile, a nitrile manufactured on a large scale as an important monomer for the production of plastics [4]. The separation of high purity acetonitrile from its aqueous solution is of particular interest to industrial chemists and process engi- neers. Similar to other water-miscible organic solvents, e.g., etha- nol, propanol, isopropanol, and tertiary butanol, etc., ACN forms a constant boiling mixture (or azeotrope) with water, which prevents the production of pure ACN by conventional distillation methods. The ACN-water azeotrope (86 % ACN and 14 % water) boils at 76 °C. To obtain ACN with a purity of > 86 %, azeotropic or extractive distillation has to be used [5, 6]. In the patents disclosed by the Standard Oil Company, a three-column distillation system was used to obtain high pur- ity ACN [4, 7, 8]. The preferred reflux ratios for the three col- umns were 5.2 to 1, 5.0 to 1, and 10.9 to 1, respectively [8]. A large reflux ratio is usually accompanied by large condensing and reboiling requirements, and hence, a higher operating cost [9]. The extraction of acetonitrile from its aqueous solution by multiple solvents has also been tested [10–12]. It is well known that when a salt is added into a mixture of water and a water-miscible solvent, a two-phase separation oc- curs with the upper phase rich in organic solvent. The salting- out is attributed to the decreased solubility of organic solvents in water in the presence of electrolytes [13]. The salting-out systems of water-ACN-salt have been studied for the purifica- tion of hydrophilic proteins [14], extraction of metallopor- phyrins [15], and preconcentration of charged analytes [16]. However, no effort has been devoted to the separation of ACN from water with the salting-out method. This is probably due to the fact that the organic (ACN) upper phase in the salting- out system still contains salt and considerable amounts of water that will complicate the further purification of ACN. In addition, salting-out usually happens at high salt concentra- tions [17]. The high salt concentration, as well as the equip- ment corrosion and fouling caused by the salt may hinder the potential use of salting-out as an ACN-water separation meth- od [18, 19]. In this study, a new phase separation phenomenon triggered by the addition of a mono-sugar or a disaccharide into an ACN-water mixture is reported and used for the separation of ACN from its water mixture. The phase ratio and sugar parti- tion in the upper ACN phase and lower aqueous phase are also documented. © 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim http://www.cet-journal.com Bin Wang 1,2 Hao Feng 1,2,3 Thaddeus Ezeji 4 Hans Blaschek 1,2,3 1 Department of Food Science and Human Nutrition, University of Illinois at Urbana-Champaign, Urbana, USA. 2 Institute of Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, USA. 3 Center for Advanced BioEnergy Research, University of Illinois at Urbana-Champaign, Urbana, USA. 4 Department of Animal Science, The Ohio State University, Wooster, USA. – Correspondence: Dr. H. Feng (haofeng@uiuc.edu), Department of Food Science and Human Nutrition, University of Illinois at Urbana- Champaign, 1304 West Pennsylvania Avenue, Urbana, IL 61801, USA. Chem. Eng. Technol. 2008, 31, No. 12, 1869–1874 1869