ETHYL ACETATE: PROPERTIES, PRODUCTION PROCESSES AND APPLICATIONS - A REVIEW Bijay N. Pattanaik, Hiren C. Mandalia ijcrr Vol 03 issue 12 Research & Development Centre, Gujarat Narmada Valley Fertilizer Category: Review Company Ltd. (GNFC), Narmadanagar- 392 015, Bharuch, Gujarat Received on:04/10/11 Revised on:11/10/11 E-mail of Corresponding Author: [email protected] Accepted on:22/10/11 ABSTRACT E-mail of Corresponding Author: [email protected] Ethyl acetate is an important organic solvent widely used in the chemical industry. This review article attempts to provide an updated compilation of research studies reported on ethyl acetate production by using various methods/techniques/ processes and it‘s parameters, which affect their productivity. The perspectives potential applications of ethyl acetate are also presented. ______________________________________________________________________ Keywords: Ethyl acetate, Esterification, compounds which generated serious Ethanol, Acetic acid. damage to the environment and human beings. With the increasing number of 1. INTRODUCTION research groups worldwide thereby Ethyl acetate is the organic compound (an regularly increasing number of oxygenated solvent) with the formula publications, covering many areas such as CH3COOC2H5 and having a molecular properties, production process and weight of 88.10. This colourless liquid has applications of ethyl acetate, we thought it a characteristic, pungent smell like certain worth to present comprehensive review glues or nail polish removers, in which it is article which covers the important work of used. Ethyl acetate is the ester from ethanol all the research group across the world. and acetic acid; it is manufactured on a large scale for use as a solvent. Ethyl 1. PRODUCTION OF ETHYL acetate is a moderately polar solvent that ACETATE has the advantages of being volatile, Industrial production of ethyl acetate is relatively non-toxic, and non-hygroscopic. mainly classified into three processes, It is a weak hydrogen bond acceptor, and is The first one is a classical Fischer not a donor due to the lack of an acidic esterification process1 of ethanol with proton. Ethyl acetate can dissolve up to 3% acetic acid in presence of acid catalyst. water and has a solubility of 8% in water at This process needs acid catalyst2 such as room temperature. It is unstable in the sulphuric acid, hydrochloride acid, p- presence of strong aqueous bases and acids. toluene sulfonic acid etc. This mixture It is soluble in most organic solvents, such converts to the ester in about 65% yield at as alcohol, acetone, ether and chloroform. room temperature. It has been also used as solvent in many CH3CH2OH + CH3COOH ↔ chemical processes for replacing aromatic CH3COOC2H5 + H2O 23 International Journal of Current Research and Review www.ijcrr.com Vol. 03 issue 12 December 2011 The reaction can be accelerated by acid This method has been proposed by two catalysis and the equilibrium can be shifted different routes; (i) dehydrogenative to the right by removal of water. Mechanism process, which uses copper or palladium of esterification reaction has been discussed based catalyst and (ii) the oxidative one, by P. Sykes.3 which employs, PdO supported catalysts. The system is strongly non-ideal due to the The former one produces, besides ethyl presence of ethanol, acetic acid and water. acetate, hydrogen and also, other by- The separation of pure components is very products which make the acetate purification difficult due to the existence of five normal expensive. In the case of oxidation process, azeotropes, namely, ethanol–water; water– the purification is straightforward and the acetic acid, ethyl acetate–ethanol, ethyl catalysts are very stable. acetate–water, and ethanol–ethyl acetate– The third one, which has been recently water. I. Sujuki et al.4 also determined the commercialized, is addition of acetic acid to phase equilibrium for the system taking the ethylene using clay and heteroploy acid7 as a reaction into account (they fitted 16 catalyst. coefficients in modified Margules equations, CH2= CH2 + CH3COOH → CH3COOC2H5 for calculating the VLE-model of this The processes, however, have some mixture). disadvantages; both the conventional The normal boiling point of ethyl acetate, esterification and addition of acetic acid to ethanol, water and acetic acid is 77.1, 78.4, ethylene need stock tanks and apparatus for 100 and 118.1 in °C respectively. The order several feed stocks. Moreover, they use of volatility is ethyl acetate, ethanol, water acetic acid that causes apparatus corrosion. and acetic acid. Ethanol and water do not Although Teshchenko Reaction uses only differ greatly in volatility, making it difficult one feed and it is a non-corrosive material, it to move ethanol up the column. The is difficult to handle acetaldehyde because is minimum-boiling binary homogeneous not available outside of petrochemical azeotropes are formed by ethanol–water at industrial area. In such circumstances, an 78.2°C With 10.57mol% water and by ethyl improved process of ethyl acetate acetate–ethanol at 71.8°C with 46 mol% production is strongly desired. ethanol. A minimum-boiling binary Several new technologies have been heterogeneous azeotrope5 is formed by ethyl commercialised. BP‘s new Avada process8 acetate–water at 70.4°C with 24mol% water, employed in a new plant at Hull, UK, uses and a ternary, minimum-boiling azeotrope is ethylene and acetic acid with solid acid formed by ethanol–ethyl acetate–water at catalyst. Davy Process Technology 70.3°C with 12.4mol% ethanol and 60.1 (formerly Kvaerner) has licensed its ethanol- mol% ethyl acetate. based process to Sasol; in this process The second one is Tishchenko Reaction6 of ethanol is dehydrogenated to acetaldehyde, acetaldehyde using aluminium triethoxide as which further reacts to form ethyl acetate. a catalyst. In Germany and Japan, most ethyl Chinese National Petroleum has developed a acetate is produced via the Tishchenko one-step ethanol process where ethanol is process. partially oxidised to acetic acid and then 2 CH3CHO → CH3COOC2H5 esterified with excess ethanol to give ethyl acetate. 24 International Journal of Current Research and Review www.ijcrr.com Vol. 03 issue 12 December 2011 In esterification reactions the function of the silica-alumina group, it was recognized from catalysts is to donate protons for the a LFER (Linear Free Energy Relationship) autoprotolysis of the carboxylic acid. For approach and from poisoning with organic this purpose, either inorganic acids, such as bases that the esterification proceeded on H2SO4, HCl, HI or Cl-SO3OH or organic even weaker acid sites than other acid- acids such as p-toluene sulfonic acid have catalyzed reactions such as dealkylation and been used.9 In spite of their lower cost, the dehydration. From simple kinetics based on interest for homogeneous catalysts in a Langmuir-Hinshelwood mechanism, chemical industry has decreased because of distinct differences were found between the their miscibility with reaction medium, two groups in that acetic acid adsorbed more which gives raise to problems such their tightly than ethanol on alumina and the separation or the corrosion of devices in reverse on the silica-alumina group, and that contact with the acid. As a result there is an the activity ratios of esterification to increasing attention for various dehydration were much larger on the silica- process/techniques to obtain ethyl acetate. alumina group than on alumina. These characteristic behaviours of ethanol and 2. DEVELOPMENTS IN THE acetic acid on silica-alumina and alumina PRODUCTION PROCESS were satisfactorily interpreted by the Generally, two types of catalysts have been assumption that the active sites for used for the production of ethyl acetate, esterification were protonic acid sites on the a) Homogeneous acid catalysts (eg. mineral silica-alumina group, but Lewis acid sites on acids like HCl, H2SO4, alkyl sulfonic alumina. On the basis of these findings, an acid, aromatic sulfonic acid, methane esterification mechanism was also proposed sulfonic acid, benzene sulfonic acid, p- by authors.10 tolune sulfonic acid). Y. Iwasawa et al.11 prepared niobium b) Heterogeneous acid catalysts (eg. strong catalysts for the formation of ethyl acetate acid ion-exchange, Rohm Q-16, Hass A- from ethanol and acetic acid. The niobium 16). catalysts involving single, pair, and Effect of different catalysts concentration, monolayer Nb-sites have been prepared by different operative temperature is applied to the reaction between surface OH groups of 3 5 determine the amount of heat release and the SiO2 and Nb(η -C3H5)4, [Nb(η -C5H5)H-μ- 5 1 possibility of the reaction in creating runway (η , η -C5H4)]2, and Nb(OC2H5)5, reaction. respectively. The obtained Nb sites were Esterification of ethanol with acetic acid on found to be attached to the surface through silica-alumina, alumina-boria, sodium- oxygen atoms, showing Nb--Si bondings poisoned silica-alumina, and alumina has besides Nb---O bonds as proved by extended been investigated by the pulse technique and X-ray absorption fine structure (EXAFS). 10 compared with ethanol dehydration. The The Nb monomers on SiO2 were active for catalysts could be classified into two groups ethanol dehydrogenation which proceeds on according to their catalytic behaviour; silica- Nb=O bonds with basic character, while the alumina, alumina-boria, and sodium- Nb dimers showed dehydration activity to poisoned silica-alumina belong to one group form ethene and diethyl ether, based on and alumina to another. Concerning the acidic character. The Nb monolayers on 25 International Journal of Current Research and Review www.ijcrr.com Vol. 03 issue 12 December 2011 SiO2 produced ethyl acetate from ethanol. acetic acid. Authors also mentioned that the The monolayer catalyst also showed a high ability of the resin not only to catalyze the activity for the formation of ethyl acetate esterification reaction but also to shift the from ethanol and acetic acid. The Nb atoms corresponding equilibrium conversion, due were suggested to be nearly uniformly to its swelling capability.