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] is an important organic 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 , . 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 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 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 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 , 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

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The reaction can be accelerated by acid This method has been proposed by two 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 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 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. This approach is supported in a monolayer-growth mode, believed to apply to a wide class of reactions where the Nb sites showed the Lewis acidic catalyzed by polymeric resins, and it is properties available for the catalytic suitable for the optimal design of the esterification. corresponding process. The synthesis of ethyl, n-butyl, isopentyl A report on selective oxidation of water- and benzyl acetates, ethyl and n-butyl containing ethanol in the presence of excess benzoates and dioctylphthalates was ethanol provides a one-step preparation of achieved by using a H-ZSM-5 and two HY ethyl acetate have been reported by J-R zeolites as catalysts under conditions similar Chang et al.14 Acetic acid is formed from the to the classical case with sulfuric acid oxidation of ethanol catalyzed by a catalyst.12 A high yield of acetates was supported Pd catalyst and is further obtained with essentially 100% selectivity. catalytically esterifies to ethyl acetate by the M. Morbidelli et al.13 mentioned that the protons dissociated from acetic acid. The characteristics of ion-exchange resins difference of the catalytic performance provide the basis for many processes of between hydrophilic and hydrophobic Pd practical interest involving both sorption catalysts was investigated by a continuous separations and catalytic reactions. The fixed-bed reactor run at 95°C, 35.4 atm, and optimal design and operation of these an air/ethanol molar ratio of 2.37. They have processes require a proper understanding of studied that, after the induction period, the the equilibrium behaviour of conversion of ethanol catalyzed by a multicomponent liquid mixtures in contact styrene−divinylbenzene copolymer (SDB)- with cross-linked polymeric resins, in terms supported Pd catalyst is more than 20 times of both the amount and composition of the that catalyzed by a γ-alumina-supported Pd sorbed mixture. For this, a model which catalyst at a weight hourly space velocity describes the equilibrium between a polymer (WHSV) of 2.4 h-1. However, it may be phase, described through the extended caused by weak metal−support interactions Flory−Huggins theory, and a liquid phase, and the formation of palladium(II) acetate which does not contain the polymer, has during the reaction. been developed. This has then been coupled A one step synthesis of ethyl acetate from a with a kinetic model describing the catalytic feed mixture of ethene, oxygen and water reaction inside the resin particles. The model using a supported Pd and silicotungstic acid has been validated through an appropriate catalyst was demonstrated.15 At about 180°C experimental analysis involving both and 25% ethane conversion, ethyl acetate equilibrium partitioning and reactive could be produced with up to 46% experiments, for the case of a highly cross- selectivity together with 34% acetic acid and linked sulfonated resin in the presence of ethanol that could be recycled. The catalyst various mixtures of the components was believed to be bifunctional with Pd involved in the esterification of ethanol with providing the oxidation function and the 26 International Journal of Current Research and Review www.ijcrr.com Vol. 03 issue 12 December 2011

silicotungstic acid providing the acidic efficient application of ion-exchange resins function. is indicated in purification by ethyl acetate The esterification of acetic acid with ethanol by selective sorption of acetic acid. catalysed by an acidic ion-exchange resin Pervaporation-aided esterification of acetic (Amberlyst-15) was carried out in a batch acid with ethanol was investigated at 70°C reactor at temperatures between 50°C and using zeolite T membranes by K-ichi 80°C at various starting compositions Okamoto.18 Almost complete conversion ranging from stoichiometric regime to the was reached within 8 h when initial molar dilute regions have been reported by S. I ratios of alcohol to acetic acid were 1.5 and Kirbaslar et al.16 The resultant kinetic model 2. The reaction time courses were well fitted the experimental data well. The described by a simple model based on the activation energy was found to be 104129 assumptions that the reaction obeyed kJ.kmol−1 for the formation of ethyl acetate. second-order kinetics and the permeation The ethyl acetate production was also flux of each component was proportional to carried out in a packed bed reactive its concentration. They have also studied the distillation column operated in batch and influence of operating parameters on continuous modes. The effects of the variation in conversion with reaction time variables such as the reflux ratio, vapour rate was investigated by means of the simulation and feed flow rate on ethyl acetate using the model. production were studied experimentally. A Esterification reactions are conventionally packed bed reactive distillation column carried out using homogeneous acids, such operated in continuous mode gave the as sulphuric acid.19 Especially in view of highest ethyl acetate composition, far catalyst separation, the use of heterogeneous surpassing the chemical equilibrium at catalysts is now heavily pursued. A. Bliek operating conditions. et al.20 have assessed the potential of MCM- Sorption of acetic acid from ethyl acetate 41 as a solid esterification catalyst and and ethanol (95%) has been investigated tested this in esterification of acetic acid and using polymeric ion-exchange resins17 with ethanol as a model reaction. Whereas the a view for being possibly applied to the mechanism for the homogeneously catalysed removal of acetic acid impurities from esterification is long known, this does not organic solvents. The resins have tertiary or hold for the esterification over quaternary amino functional groups on a heterogeneous catalysts. Using transient and styrene–divinyl benzene copolymer matrix. steady state experiments, temperature- The equilibrium adsorption studies show programmed desorption (TPD), and isotopic very selective adsorption with a high loading labelling experiments, the esterification capacity for acetic acid. The uptake of the mechanism over MCM-41 (Si/Al=16) is acid from the organic solutions is by studied. Gas-phase esterification of acetic sorption reinforced by specific interaction acid with ethanol over MCM-41 (Si/Al=16) with the functional groups on the polymer is shown to proceed via a Langmuir– matrix. The specific interaction takes place Hinshelwood-type mechanism, involving a by a hydrogen bonded complex formation protonated acetic acid intermediate. between the acidic proton and the lone pair Direct synthesis of ethyl acetate from of electrons on the amino group. An ethanol over a Cu–Zn–Zr–Al–O catalyst was 27 International Journal of Current Research and Review www.ijcrr.com Vol. 03 issue 12 December 2011

investigated under pressured conditions Tsotsissa et al.22 have developed to describe between 200°C and 270°C by I. Kanichiro at PVMR behaviour. The simulation results of al.21 Both the selectivity to ethyl acetate and the model have been validated with the space-time yield of ethyl acetate increase experimentally observed pervaporation with increasing reaction pressure, whereas membrane reactor conversions. The model is ethanol conversion decreases. The highest used to describe a number of alternative space-time yield of ethyl acetate is attained PVMR configurations and analyze the at a reaction pressure of about 0.8 MPa with reactors that effect and optimize their maximum selectivity of 93 wt%. During the performance. process, ethanol is first dehydrogenated to The reactive distillation system for the acetaldehyde and is then coupled with production of ethyl acetate via esterification another ethanol molecule to form of acetic acid with ethanol using sulphuric hemiacetal, which is further dehydrogenated acid as homogeneous catalyst have been to ethyl acetate. The concentration of by- reported by Y. T. Tang et al.23 A suitable products such as 1-butanol and butanone, NRTL (non-random two-liquid) model which form after the aldol addition of parameter set for calculating of liquid acetaldehyde, decreases with increasing activity coefficients has been established reaction pressure. Since the equilibrium of with excellent prediction of the the dehydrogenation of ethanol to compositions and temperatures for the four acetaldehyde shifts to an ethanol-rich azeotropes in this system. In the VLE composition at high pressure, the decrease in (vapour liquid equilibrium) calculations, the partial pressure of acetaldehyde explains vapor association of acetic acid due to the suppression of the by-products formed dimerization has also been considered. A through acetaldol. reactive distillation column with an Esterification reactions are typically limited overhead decanter can be designed to by thermodynamic equilibrium, and face achieve over 93 wt% of ethyl acetate challenges with product purification. composition at organic phase top product Commercially, it was carried out using stream while the bottom product stream is either large excess of one of the reactants, or designed to be rich in acetic acid so that it by removing through reactive distillation can be recycled and mixed with fresh acid one of the product. As a result reactive make-up stream to serve as acid feed to the distillation, which favourably shifts reactive distillation column. Since the purity equilibrium through the removal of one of of the optimum top organic product is still products, is becoming more common in not good enough for the ethyl acetate plant-scale production. It is, however, an product specification in industry, an energy-demanding operation and is not additional column is designed to purify the recommended when dealing with ethyl acetate product of the reactive temperature-sensitive chemicals or distillation column to over 99.5 wt%. The biocatalysts. The aforementioned difficulties top draw of the second column will be have motivated efforts for the development recycled back to the decanter. In summary, of other coupled reactive/separation they have developed, the overall optimum processes. Pervaporation membrane reactors design of this ethyl acetate reactive (PVMR), in particular, are distillation. T. T. distillation system includes two columns 28 International Journal of Current Research and Review www.ijcrr.com Vol. 03 issue 12 December 2011

(including the reactive distillation column impact to the environment and cause no and the second column), one decanter, and corrosion to the reactor wall. These catalysts two recycle streams. The optimum operating had continued performance for 2200 h. condition of the overall system will also be Evaluation also shows that half of the studied by authors to minimize the total process water and one-third of the operating cost of the overall system while consumption of purification steam can be meeting product specifications. saved. Most of the commercial processes for ethyl Vapor-liquid equilibrium for the quaternary acetate productions are via liquid-phase reactive system, ethyl acetate + ethanol + esterification. Owing to the thermodynamic water + acetic acid and constituent binary limitations, the overall yields of ethyl system ethyl acetate + ethanol, ethyl acetate acetate are confined to 67% with equimolar + acetic acid and water + acetic acid has reactant feeds of acetic acid and ethanol. An been determined at 101.3 kPa by J. Tojo et 25 efficient two-phase reaction of ethyl acetate al. UNIQUAC equation was used to production in modified ZSM-5 zeolites has correlate the experimental phase equilibrium been reported by K-C Wu and Y-W Chen.24 data of the quaternary system. Experimental The reactions were conducted at 90–127 °C, binary data were correlated using Wilson, with molar ratio of ethanol/acetic acid=1.5 NRTL and UNIQUAC equations. and with LHSV=1 h−1. One of the critical The esterification of acetic acid by ethanol parameters in this novel ethyl acetate in presence of modified catalysis- synthesis process is the reaction phosphomolybdic acid (PMA) supported on 26 (esterification) temperature. It was kept silica gel (1–30 wt %) have been reported. between the liquid- and gas-phase operation The catalysts were characterized by regimes at which some parts of the reacting thermogravimetry (TG), differential thermal composition were vaporized. The major analysis (DTA), X-ray diffraction, FT-IR consideration is based on the equilibrium spectroscopy and N2 adsorption constants in the gas-phase reaction, which measurements. The surface acidity and are higher than those in the liquid phase. basicity of the catalysts were determined by The initial reaction stage in the liquid phase adsorption of pyridine and the dehydration– has the advantage of smaller reactor size and dehydrogenation of 2-propanol. The gas- more efficient contacting with the catalysts. phase esterification of acetic acid by ethanol As the equilibrium had been achieved in the was carried out in a conventional flow bed final gas phase, a higher conversion of reactor. The results clearly revealed that ethanol was obtained due to the equilibrium among the PMA loading, the use of 10 wt% constant constraints. Consequently, both the catalysts showed maximum yield of ethyl equilibrium conversion constraint for the acetate. This catalyst also improved on liquid-phase regime and the larger reactor addition of Na or K-hydroxide. These results volume requirement for the gas-phase were correlated with the structure and the reaction have been overcome. They have acid–base properties of the prepared studied that the one-pass ethanol conversion catalysts. was successfully improved from 67 to SiO2, Al2O3, ZnO, SnO2 and WO3-ZrO2 85 mol%. In addition, the solid acid (29%, w/w WO3) supported Pd catalysts catalysts used in this novel process have low (1%, w/w Pd) for the direct transformation 29 International Journal of Current Research and Review www.ijcrr.com Vol. 03 issue 12 December 2011

of ethanol to ethyl acetate under medium of the grafted silica gel is only 25% of the pressure conditions (1 MPa pressure) have ion-exchange resin, the catalytic activity of been studied by P. R. de la Piscina et al.27 acid groups in the grafted silica gel is higher The synthesis of ethyl acetate was than in the resin. investigated using a heterogeneous catalyst- On the other hand, kinetic studies on the

Commercial acid resin, Amberlyst 15 liquid phase esterification of C3 and C4 (Rohm and Haas) and a pervaporation unit - alcohols on acetic acid were carried out over Commercial hydrophilic composite zeolites30 Hβ, HY and HZSM5. Zeolite Hβ membrane, PERVAP 1000 and 1001 Le was found to be the most active for the Carbone Lorraine28. Shifting the reaction esterification reaction of ethanol and acetic equilibrium by selective water removal acid. The acidity of zeolite determines the increased the ethyl acetate productivity. The extent of the esterification reaction. The effects of catalyst mass, reaction esterification reaction was found to follow temperature, and initial reactants ratio were the Eley–Rideal pathway. Acetic acid is studied. The kinetic parameters, such as activated by adsorption on the zeolite acid activation energy and apparent reaction site, which then reacts with the alcohol in order, were determined. The water the bulk to form the corresponding acetate. production and removal rates obtained in The reaction kinetics of the esterification of reaction and pervaporation experiments, acetic acid with ethanol, catalyzed both respectively, were used in a computational homogeneously by the acetic acid, and code to simulate the behaviour of the heterogeneously by Amberlyst 15, has been coupled system. The highest conversion was investigated by A. Dominguez et al.31 The observed when an initial ethanol/acetic acid reactions were carried out at several molar ratio of 9:1 was used. At this temperatures between 30-80°C and at condition, the water production was reduced various starting reactant compositions. turning the water removal process more Homogeneous and heterogeneous reactions selective, increasing the acetic acid have been described using the models conversion from 51.0% to 63.9%. proposed by T. Popken et al.32 These models Sulfonated polystyrene grafted silica gel use activities instead of mole fractions. particles29 were synthesized for use as an Activity coefficient has been calculated acid catalyst in the liquid phase using ASOG33 and UNIFAC34 methods. A esterification of acetic acid with ethanol at packed bed reactive distillation column 40-80°C. The synthesis of the grafted silica filled with Amberlyst 15 has been employed gel particles consists of three steps: to obtain ethyl acetate. The influence of feed polymerization, grafting, and sulfonation. compositions and reflux ratio has also been The synthesized catalyst is non-cross-linked, analysed. non-swelling, and mechanically as well as An additional example, the aerobic chemically stable. It contains 29% oxidation of aqueous ethanol to produce covalently-bound sulfonated polystyrene acetic acid and ethyl acetate was studied chains that give an acid capacity of using heterogeneous gold catalysts.35 −1 0.99 mmol g . The kinetics of the grafted Comparing the performance of Au/MgAl2O4 silica gel is as rapid as that of a commercial and Au/TiO2 showed that these two catalysts ion-exchange resin. Since the acid capacity exhibited similar performance in the 30 International Journal of Current Research and Review www.ijcrr.com Vol. 03 issue 12 December 2011

reaction. By proper selection of the reaction thus prepared were crosslinked with conditions, yields of 90–95% of acetic acid glutaraldehyde and tested for the could be achieved at moderate temperatures pervaporation (PV) dehydration of ethanol and pressures. Based on author findings, a and acetic acid at 30–60 °C. The aluminum- reaction pathway for the catalytic oxidation rich zeolite beta, with its hydrophilic nature of ethanol via acetaldehyde to acetic acid is as well as molecular sieving effect and its proposed, and the rate-determining step favorable interaction with hydrophilic (RDS) in the mechanism is found to be the NaAlg, was responsible to enhance the PV (possibly oxygen-assisted) dehydrogenation dehydration of acetic acid and ethanol in of ethanol to produce acetaldehyde. It also is terms of separation factor, flux, concluded that most of the CO2 formed as a pervaporation separation index (PSI) and by-product in the reaction results from the enrichment factor (β). Thermodynamic absorbed intermediate in the model for sorption process was investigated dehydrogenation of ethanol to produce typically for water + ethanol mixtures based acetaldehyde. By varying the amount of on Flory–Huggins theory to explain the PV water in the reaction mixture, the performance. Based on these results, possibilities for producing ethyl acetate by permeance and driving force mechanisms the aerobic oxidation of ethanol is also were also elucidated. Extraction or studied. dissolution of zeolite beta from mixed On the other hand, inert membrane reactors matrix membranes is confirmed by have been a subject of interest during the equilibrium sorption. Arrhenius parameters last decade, the two main applications for the process of permeation were consist of distributing a reactant to increase calculated using these data at different selectivity and remove a product to enhance temperatures to investigate their effects on conversion in equilibrium-limited reactions. the nature of the mixed matrix membrane.

Two different zeolite membranes, mordenite The plots of in Jp vs. 1/T were constructed and zeolite A have been tested in the and found to follow the linear trends in the esterification of acetic acid with ethanol in a studied range of 30–60 °C for both the feed continuous membrane reactor packed with mixtures, indicating that flux followed the catalyst Amberlyst™ 15 by R. Mallada et Arrhenius trend. PV experiments were also al.36 Both membranes are capable of shifting carried out for 5 and 10 wt. % incorporated the equilibrium in less than 1 day of NaAlg mixed matrix membranes at 70 °C to experiment. Mordenite membranes showed verify the suitability of the membranes at the a great resistance to acidic reaction medium, esterification temperature. PV-aided with conversions of about 90% maintained catalytic esterification of acetic acid with for 5 days of experiment, with very high ethanol was studied at 70 °C, which led to a separation factors water/ethanol and considerable increase in ethyl acetate water/acetic acid. conversion with a reduction in reaction time Mixed matrix membranes of sodium as compared to the blank reaction due to alginate (NaAlg) were prepared37 by continuous removal of water permeating solution casting by incorporating 2.5, 5, 7.5 through the barrier membrane. and 10 wt. % of zeolite beta particles for the Supported niobium pentoxide catalysts38 are production of ethyl acetate. The membranes active for a variety of acid and redox 31 International Journal of Current Research and Review www.ijcrr.com Vol. 03 issue 12 December 2011

catalyzed reactions such as dehydration, production with a pilot plant, a complex hydrogenation and esterification. In this two-column configuration with liquid phase regards, niobium pentoxide has been split, (2) to study the initial charges to the supported on silica–alumina using two column holdups and a start-up procedure for 39 methods: grafting in CH2Cl2 or ethanol continuous production. 40 solution with NbCl5 precursor, and H-P Huang et al. prepared a pilot-scale impregnating in aqueous solution with plant consists of one RD column (10 ammonium niobium oxalate. These catalysts reactive trays plus structured packing for were used to characterize by various separation) and a downstream stripper with a methods such as XRD, TG/DTG/DTA, decanter in between the two columns are FTIR, DRIFTS, FT-Raman, and calorimetric equipped with temperature, flow, and level titration with pyridine. Calcination of the measurements and a Delta-V process control materials at 800 °C produced crystalline computer. The industrial grade alcohol

Nb2O5 (T-phase) for the samples prepared (89 mol% ethanol, 11 mol% H2O) and acid by grafting, while a mixture of T- and H- (96.75 mol% acidic acid and 3.25 mol% phases are formed by aqueous impregnation, H2O) are used as reactants. A product that indicating the higher stability of the former contains more than 99 mol% ethyl acetate materials. On the other hand, partial and less than 100 ppm acetic acid is required neutralization of hydroxyl groups occurred as specifications. The results from six on the support surface by grafting process, experimental runs show that, with proper and the neutralization reaction is practically initial charges in the inventory holdups and complete at 25 wt. % of Nb2O5 by a systematic start-up procedure, high-purity impregnation. The catalysts with about acetate can be produced in a straightforward

10 wt. % of Nb2O5 prepared by aqueous manner. impregnation reached the monolayer, while Reduction of energy demand is a challenge by grafting it predominates bulk Nb2O5, as that must be faced in coming years and demonstrated by FT-Raman. These catalysts process integration in chemical industry is also showed the highest acidity, when pointed out as a feasible alternative to calcined at 300 °C. Based on these results, achieve more efficient processes. liquid phase esterification reactions of acetic Pervaporation membrane reactors are the acid were carried out with different alcohols systems in which the separation and reaction (ethanol, n-butanol, and iso-pentanol). The are carried out simultaneously in order to yields were about the same, independent of increase conversions by removing one or the preparation method for 10 wt. % Nb2O5 more of the products formed during catalysts. The conversions using molar ratio equilibrium reactions.41 2:1 (acid: alcohol) after 8 h showed good C. P. Borges et al.42 using acetic acid and results (83, 87, and 91%, respectively) and ethanol as a model system, pervaporation- 100% selectivity for all . assisted heterogeneous catalytic The production of high-purity ethyl acetate esterification was investigated to increase using reactive distillation (RD) is studied ester conversion in mild operational experimentally in a pilot-scale plant. The conditions. The pervaporation-assisted objectives are twofold: (1) to realize the esterifications were carried out using type-II RD process39 for ethyl acetate Amberlyst 15 and 35 (Rohm & Haas) as 32 International Journal of Current Research and Review www.ijcrr.com Vol. 03 issue 12 December 2011

catalyst and hydrophilic Pervap 1000 alumina-promoted SZ performances in the membrane (Sulzer) in a bench scale esterification reaction of ethanol and acetic pervaporation apparatus. A catalytic acid were investigated by X. L. Zhou et al.44 membrane was also developed by coating The textural property, crystalline phase and the Pervap membrane with a thin superficial surface acidity of the catalysts were layer of tiny catalyst particles in poly (vinyl characterized by using nitrogen adsorption– alcohol) solution. Reaction and separation desorption isotherms, XRD and FT-IR were conducted in two separated steps and spectroscopy of pyridine adsorption in a single one, by means of a catalytic techniques, respectively. Effects of the membrane. For the former, the membrane- reaction time and catalyst reuse cycle as assisted reactor, it was observed that the well as catalyst regeneration on the catalytic ratio of membrane area to reaction volume is behaviours were also studied. Experimental an important parameter to get equilibrium results showed that Yb2O3–Al2O3 promoted displacement. For the catalytic membrane SZ (designated as SZAY) catalyst exhibited there was an increase up to 60% in ethyl an optimal esterification performance; the acetate conversion at 60 °C. These results Lewis acid sites with moderate and super indicate the potentiality of the coupled strong strength could mainly be responsible process, since catalyst concentration can be for the esterification reaction; and doping easily increased, leading to higher ester both Yb2O3 and Al2O3 on SZ not only production rates. boosted the esterification activity but also A. Hasanoglu et al.43 have been studied the alleviated catalyst deactivation resulted from esterification reaction of acetic acid and the surface sulfur loss by solvation. ethanol to produce ethyl acetate and water On the other hand, the separation of ethyl was investigated using a batch pervaporation acetate and ethanol is important but difficult Polydimethylsiloxane (PDMS) membrane due to their close boiling points and reactor. The experiments were carried out in formation of an azeotropic mixture. The the temperature range of 50-70°C. The ratios separation of the azeotropic mixture of ethyl of ethanol concentration to acetic acid acetate and ethanol using the hydrophilic concentration were chosen as 1 and 1.5. ionic liquids (ILs) 1-alkyl-3- Amberlyst 15 and sulfuric acid were used as methylimidazolium chloride (alkyl = butyl, the catalysts. In this way, conversions were hexyl, and octyl) ([Cnmim]Cl, n = 4, 6, 8) increased by continuous removal of ethyl and 1-allyl-3-methylimidazolium chloride acetate from the reaction media. and bromide ([Amim]Cl and [Amim]Br) has Conversions are found to increase with an been investigated by Ji Chen et al.45 Triangle increase in both molar ratios of reactants and phase diagrams of five ILs with ethyl acetate temperature. Temperature has a strong and ethanol were constructed, and the influence on the performance of the biphasic regions were found as follows: pervaporation membrane reactor because it [Amim]Cl > [Amim]Br > [C4mim]Cl > acts on both the esterification kinetics and [C6mim]Cl > [C8mim]Cl. The results pervaporation. showed that the hydrophilic ILs [Cnmim]Cl Solid super acid catalysts including (n = 4, 6, 8), [Amim]Br, and [Amim]Cl 2− SO4 /ZrO2 (SZ), rare earth (RE) oxide- could remove ethanol effectively from the promoted SZ and RE oxides together with azeotropic mixture of ethyl acetate and 33 International Journal of Current Research and Review www.ijcrr.com Vol. 03 issue 12 December 2011

ethanol. Moreover, it was found that was studied and simulated by M. Tajdari et [Amim]Cl had the highest extraction al.47 The dynamic behaviour of the process efficiency, and the purity of ethyl acetate was experimentally analyzed. The reactants could reach 99.27 wt. % after extraction were conducted in a fifteen stages RDC in a twice. These hydrophilic ILs are easily single feed stream. An appropriate strategy synthesized and purified, are economically was chosen and performed for column start feasible, and caused no erosion to the up to achieve the steady state condition. The equipment, which usually happened for ILs temperature, pressure, mass flow rates (TPF) containing F. ILs could be recycled by and mole fractions effects in feed were simple distillation. The separating process considered in the column until a new steady can reduce the energy consumption greatly, state condition was obtained. For top flow of and the total process is green and the column, the simulated results were environmentally benign. compared with the experimental data. It The ethyl acetate synthesis by the oxidative concluded that there were errors less than route using a renewable raw material- 8% for the mole fraction shock results.

PdO/SiO2 catalyst can be considered as a Liquid phase esterification of acetic acid very promising new process reported by L. with ethanol over dodecatungestophosphoric G. Appel et al.46 These catalysts were acid (DTPA) supported on K10 mont- characterized by XPS, UV–vis, XRD, morillonite was systematically studied and chemical analysis and BET. These catalysts optimization of process parameters was were tested under different experimental carried out by V. V. Bokade et al.48 The conditions using a conventional system with 20% m/m DTPA/K10 was found to be the a fixed bed reactor at atmospheric pressure. optimum catalyst with 90% acetic acid It was inferred that the ethyl acetate conversion and 100% ethyl acetate synthesis occurs via ethanol oxidation selectivity. Authors were also explored to followed by the condensation reaction of see the feasibility of 20% m/m DTPA/K10 acetaldehyde and ethanol or ethoxide as a catalyst for the alkylation of acetic acid species. Author also suggested that the rate with other alcohols like methanol, iso- limiting step of the synthesis change propanol and n-butanol. according to the rate of ethanol A tubular hydroxy sodalite (SOD) consumption. For low rates, the limiting step membrane was successfully applied in the is the ethanol oxidation to acetaldehyde, and esterification of acetic acid with ethanol and for the high ones, it is the condensation acetic acid with 1-butanol, by Freek reaction. It was verified that the catalysts Kapteijn et al.49 The reactions were carried preparation conditions modify the PdO out using equimolar solutions of acetic acid distribution on the support and its particle with the appropriate organic alcohol at 90°C sizes, therefore, changing the ethanol using Amberlyst 15 as acid catalyst. The consumption rate, and consequently, the hybrid process drove the esterification selectivities to acetaldehyde, ethyl acetate, reactions almost to completion. The SOD- acetic acid and CO2. membrane showed absolute selectivity The dynamics and shock-control in a towards water and retained its stability under reactive distillation column (RDC) for the the reaction conditions. The membrane trans-esterification of ethanol and acetic acid exhibited a stable water pervaporation 34 International Journal of Current Research and Review www.ijcrr.com Vol. 03 issue 12 December 2011

performance at pH values above 2.9 for obtained is desorbed. Oxides with strong acetic acid–water mixtures. basic sites generate the most active and Recently, the reaction of direct selective systems for the ethyl acetate transformation of ethanol to ethyl acetate synthesis. was investigated on reduced Cu/ZrO2 Recently, direct transformation of ethanol catalysis prepared by a co-precipitation into ethyl acetate through catalytic procedure.50 These catalysts were membranes containing Pd or Pd-Zn has been 52 characterized by N2 adsorption, XPS, XRD, reported by P. R. De La Piscina et al.

TPR, and NH3-TDP. The catalytic Authors were studied the ethanol performances of these Cu-Zr mixed oxides dehydrogenating coupling at 250°C and 1 were considerably influenced by changing MPa over catalytic membrane reactors the molar ratio of Cu to Zr. The highest (CMRs) conventional supported catalysts selectivity to ethyl acetate was found over based on Pd or Pd-Zn on CeO2-ZrO2. They

Cu/ZrO2 (1) catalyst (molar ratio of Cu and have prepared CMRs through a wet Zr was one). The studied revealed that the impregnated method based on evaporation presence of a certain amount of Cu+2 species craytallization was used to deposit Pd or Pd may play very important role in improving and Zn on membrane reactors of TiO2 with a the selectivity to ethyl acetate of the top layer of CeO2-ZrO2 and a pore size of 5

Cu/ZrO2 catalyst. nm. These systems were compared with

In the next decades, ethanol produced from conventional CeO2-ZrO2 supported Pd or cellulosic residues will be in large supply all Pd-Zn catalysts. Monomettalic Pd systems over the world. Undoubtedly, bio-ethanol favoured the decomposition of ethanol will be used as a gasoline substitute or giving CO and CH4 as the main product. additive. Taking its future large availability The presence of Zn in both Pd/CeO2-ZrO2 into account, its use as feedstock for the and CRMs containing Pd inhibited ethanol chemical industry can also be foreseen. The decomposition and favoured the production ethyl acetate one-pot synthesis from ethanol of acetaldehyde, which was subsequently is a good example of this new industry. The transformed to ethyl acetate. dehydrogenative route of the ethyl acetate one-pot synthesis and also the role of the 3. PATENTS support using physical mixtures comprised The production of esters by a reaction of a dehydrogenation catalyst and four between organic acids or their anhydrides different oxides have been studied by P. C. and olefin hydrocarbons in the presences of Zonetti et al.51 These catalysts were halide catalysis and it‘s pertains more characterized employing TPD of ethanol, particularly to the direction of reaction 53 CO2 and acetaldehyde and also pyridine toward the formation of particular esters adsorption. Authors have verified that and the avoidance of side reactions such as acetaldehyde synthesized on the polymerization. The preferred catalyst is dehydrogenation catalyst migrates towards boron fluoride promoted with a hydrogen the oxide and reacts with the ethoxide halide such as hydrogen chloride of species which are generated by the oxide hydrogen fluoride. Such catalysts other basic sites. The resulting hemiacetal is many advantages over sulphuric acid; dehydrogenated and the ethyl acetate phosphoric acid, aluminium chloride, etc. 35 International Journal of Current Research and Review www.ijcrr.com Vol. 03 issue 12 December 2011

Because of the remarkable effectiveness of oxidation of liquid ethanol in the presence of the boron fluoride-hydrogen halide catalyst excess liquid ethanol and a supported and the catalyst may be separated from oxidation catalyst by a solid ion-exchange reaction products and recovered for reuse. resin in the acid form (Amberlyst 15 in acid M. Gruffaz et al.54 invented a process for the form).58 In this process, the acetic acid preparation of ethyl acetate by vapour phase produced in the oxidation is absorbed by the reaction of ethylene with acetic acid, the excess liquid ethanol, which esterifies to improvement which comprise conducting ethyl acetate. The oxidation portion of said reaction in the presence of a catalytic process is preferred with a metallic amount of a solid, ion-exchange oxidation catalyst on a hydrophobic support. fluoropolymer comprising sulfonic acid The esterification portion of the process is moieties and its activity is virtually constant preferred with an acidic solid ion-exchange over a long period of time as well as resin to promote the esterification. virtually no by-products are formed. US P. 6 768 021 B2 describes another A process for the preparation of ethyl approach based on the use of a membrane acetate by hydrogenating acetic anhydride or separation unit to remove water from the mixture of acetic anhydride and ethylidene resultant product ethyl acetate-stream59. An diacetate in the presence of a Raney Nickel improved process for producing acetic acid catalyst55 and an organic sulfonic acid (p- and ethanol in a reaction zone in the toluene sulfonic acid) to produce ethyl presence of an acid catalyst (a variety of acetate is disclosed in US P. 4 471 136. homogeneous or heterogeneous acid, Rohm Carboxylic acid esters, and in particular and Hass A-16), distilling formed vapours ethyl acetate, are produced by esterification and condensing to form an organic phase of an organic carboxylic acid ester with an rich in ethyl acetate and an aqueous phase alcohol (methanol, ethanol, propanol, the rich in water, separating the phases and isomeric butanols and the isomeric further distilling each phase to obtain a final pentanols) in the presence of alkyl sulfonic purified ethyl acetate product and a water acid having desulphonation temperature in stream low in organic components, the excess of that of p-toluene sulfonic acid is improvement comprising directing the invented by John Russell et al.56 They also organic phase from the first distillation to claimed corrosion inhibitor-copper acetate, the reaction zone. to reduce corrosion of the vessel. US P. 0 255 072 A1 reveals a process for the Process for the preparation of ethylidene production of ethyl acetate by reacting diacetate and/or ethyl acetate by ethylene with acetic acid and water in hydrogenating acetic anhydride57 in the presence of a heteropoly acid catalyst7 in presence of a homogeneous ruthenium which the concentrations of reactants in the catalyst, methyl iodide and lithium iodide feed stream to the reactor are such as that are disclosed in US P. 4 886 905. The the mole ratio of ethylene to water lies in the process can also by utilize to hydrogenate range 8.0 to 17.0 and the mole ratio of acetic mixtures of acetic anhydride and ethylidene acid to water lies in the range 1.25 to 1.40. diacetate to produce ethyl acetate. Recently, a process for the selective In another process, ethyl acetate is production of ethyl acetate by vapour phase synthesized from a one step process of an reaction of acetic acid over a hydrogenating 36 International Journal of Current Research and Review www.ijcrr.com Vol. 03 issue 12 December 2011

catalyst composed of a supported bimetal of "fruitiness" in the wine. Sensitivity varies catalyst60 such as for example, platinum or with most people having a perception palladium and copper or cobalt supported on threshold around 120 mg/lit. An excessive a suitable catalyst to form ethyl acetate is amount of ethyl acetate is considered a wine disclosed in US 0029980 A1. fault. Exposure to oxygen can exacerbate the fault due to the oxidation of ethanol creating 4. APPLICATIONS acetaldehyde. This can leave the wine with Ethyl acetate has a wide range of sharp vinegar like taste. applications61 across many industries, Electronics: including: Small quantities of ethyl acetate are also Surface coating and thinners: used in the manufacture of video/audio Ethyl acetate is one of the most popular tapes. Magnetic media of tapes are purified solvents and finds wide use in the with ethyl acetate. It is also used for head manufacture of nitrocellulose lacquers, cleaning. In fact, ethyl acetate of 99.7% varnishes and thinners, to dissolve the quality is the best solvent for cleaning, etc. pigments for nail varnishes. It exhibits high Miscellaneous: dilution ratios with both aromatic and Ethyl acetate is used in the manufacture of aliphatic diluents and is the least toxic of adhesives, cleaning fluids, nail polish industrial organic solvents. removers and silk, coated papers, textiles, Pharmaceuticals: explosives, artificial leather etc. In the field Ethyl acetate is an important component in of entomology, ethyl acetate is an effective extractants for the concentration and poison for use in insect collecting and study. purification of antibiotics. It is also used as In a killing jar charged with ethyl acetate, an intermediate in the manufacture of the vapours will kill the collected (usually various drugs.62 adult) insect quickly without destroying it. Flavors and essences: Because it is not hygroscopic, ethyl acetate Ethyl acetate finds extensive use in the also keeps the insect soft enough to allow preparation of synthetic fruit essences, proper mounting suitable for a collection. flavors and perfumes. High purity product (ethyl acetate) can be Flexible packaging: used as a viscosity reducer for resins used in Substantial quantities of ethyl acetate are photo resist formulations in the electronics used in the manufacture of flexible industry. packaging and in the manufacture of Ethyl acetate is also used as a solvent in a polyester films and BOPP films. It is also variety of coating formulations including used in the treatment of aluminium foils. epoxies, urethanes, cellulosics, acrylics and Occurrence in wines: vinyls. These coatings are used for wood Ethyl acetate is the most common ester furniture and fixtures, agricultural, found in wine, being the production of the construction and mining equipment, most common volatile organic acid-acetic containers and closures, auto refinishing, acid and the ethanol alcohol created during and maintenance and marine applications. the fermentation of wine. The aroma of ethyl Over the past twenty years, ethyl acetate acetate is most vivid in younger wines and coatings have been losing share to contributes towards the general perception waterborne and high solids coatings, powder 37 International Journal of Current Research and Review www.ijcrr.com Vol. 03 issue 12 December 2011

and two-component coatings systems, due to 8. John R, Sowa Jr. Catalysis of Organic environmental constraints on volatile Reactions, CRC Press, 2005, Ch. 29, pp. organic compound (VOC) emissions. Ethyl 251-260. acetate is used as a solvent in inks for 9. Maki-Arvela P, Salmi T, Sundell M, flexographic and rotogravures printing, Ekman K, Peltonen R, Lehtonen J. where it‘s main function is to dissolve the Appl. Catal. A: General. 1999; 184: 25- resin, control the viscosity and modify the 32. drying rate. As with industrial coatings, the 10. Mochida I, Anju Y, Kato A, Seiyama T. decline in the use of acetate because of J. of Catalysis. 1971; 21(3): 263-269. environmental constraints has largely been 11. Shirai M, Ichikuni N, Asakura K, completed. Iwasawa Y. Catalysis Today. 1990; 8(1): 57-66. CONCLUSION 12. Yudao M, Wang QL, Yan H, Xingdong Survey of the literature reveals that ethyl J, Qiu Q. Applied Catalysis A: General. acetate has been used for a multitude of 1996; 139 (1-2): 51-57. applications. We believe that the almost all 13. Mazzotti M, Neri B, Gelosa D, Kruglov the important results presented in this review A, Morbidelli M. Ind. Eng. Chem. Res. will open up a potentially new chapter in the 1997; 36 (1): 3-10. ―chemistry of ethyl acetate‖. 14. Tzong-Bin L, Dong-Lin C, Jen-Ray C. Ind. Eng. Chem. Res. 1999; 38(4): REFERENCES 1271-1276. 1. Fischer E, Speier A. Ber. 1895; 28: 15. Furuta M, Kung MC, Kung HH. 3252-3258. Applied Catalysis A: General. 2000; 201 2. Hughes ED. Quart. Rev. 1948; 2: 110. (1): L9-L11. 3. Sykes P. A Guidebook to Mechanism in 16. Kirbaslar SI, Baykal ZB, Dramur U. Organic Chemistry, Longmans, 6th Turk. J. Engin. Environ. Sci. 2001; 25: edition, 1986. 569-577. 4. Suzuki I, Yagi H, Komatsu H, Hirata M. 17. Anasthas HM, Gaikar VG. Reactive and J. Chem. Eng. Japan. 1971; 4: 26-33. Functional Polymers. 2001; 47 (1): 23- 5. Seader JD, Henley EJ. Separation 35. Process Principle, Wiley John Wiley & 18. Tanaka K, Yoshikawa R, Ying C, Kita Sons, Inc., 2nd Edition, 2006. H, Okamoto K. Catalysis Today. 2001; 6. Seki T, Nakajo T, Onaka M. Chemistry 67 (1-3): 121-125. Letters. 2006; 35(8): 824-829. 19. Furniss BS, Hannaford AJ, Smith PWG, 7. (a) Fullerton W, Miller AJ, in-ventors; Tatchell AR, Vogel‘s: Textbook of BP Chemicals Limited, assignee. practical organic chemistry, Longman Process for the production of ethyl Group UK, 5th Edition, 1999. acetate. US Patent 0, 255, 072 A1. 2007 20. Koster R, van der Linden B, Poels E, Nov. 1. (b) Pirgonde BR, Bokade VV. Bliek A. Journal of Catalysis. 2001; 204 Indian Streams Research Journal. 2011; (2): 333-338. I (VI): 227-231. 21. Inui K, Kurabayashi T, Sato S. Journal of Catalysis. 2002; 212 (2): 207-215.

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