36_Patidar

is

0 07

ng R

a r t i c l e i n f o

2012 Elsevier B.V. All rights reserved.

monly encountered in the industry as a byproduct of ethanolmanufacturing process through the fermentation route. Sugar-containing substrates when fermented with yeast in the presenceof nitrogenous diet (e.g. proteins like albuminoids which promotegrowth of yeast), yield ethanol associated with differentimpurities collectively known as fusel oil. Major ones among theseimpurities are aliphatic alcohols (see Table 1) higher in molecular

step, in this article, we present the studies in kinetics of differentreactions involved in esterication of fusel oil with acetic acid (seeEq. (1)) in the presence of ion exchange resin, Amberlyst-15, as acatalyst. Ion exchange resins are highly versatile catalysts thatwork well in both polar and non-polar media. They have beensuccessfully used in reactive distillation columns in a suitableform, for the production of chemicals like fuel ethers such asMTBE and TAME [1].

CH3COOH ROH\[Amberlyst-15

CH3COOR H2O 1 Corresponding author.

Chemical Engineering Journal xxx (2012) xxxxxx

Contents lists available at

ne

w.E-mail address: [email protected] (S.M. Mahajani).1. Introduction

The applicability of reactive distillation (RD) as a tool ofprocess intensication is well investigated in the past for esteri-cation of different alcohols [1]. The focus is on enhancing the per-pass conversion and bringing cost-effectiveness and compactnessto the chemical plant through reduction in equipment cost andenergy consumption. In these studies, a pure alcohol or its aque-ous solution is considered as a feedstock to make or recover a par-ticular ester of interest [e.g. see 2,3]. To the best of our knowledgethere are no studies reported in literature, dealing with a mixtureof alcohols as a raw material. Fusel oil is one such feedstock com-

weight than ethanol, such as, n-propanol, iso-butanol and iso-amylalcohol [46]. All these alcohols and their esters are individuallyvaluable and hence after bulk separation of ethanol, one can ester-ify and process the fusel oil for value addition [5]. Esterication ofsuch a mixture is more challenging, compared to that of an indi-vidual alcohol, owing to the presence of a large number of azeo-tropes and simultaneous trans-esterication reactions. There isnot much information available in the literature on the processingof fusel oil to bring in value addition. Hence, the broad objectiveof this work is to evaluate the applicability of RD for the esteri-cation of fusel oil and suggest the most cost-effective RD congu-ration giving all the esters in pure form as products. As the rstArticle history:Available online xxxx

Keywords:Reactive distillationEstericationFusel oilReaction kineticsIon exchange resins1385-8947/$ - see front matter 2012 Elsevier B.V. Ahttp://dx.doi.org/10.1016/j.cej.2012.06.139

Please cite this article in press as: P. Patidar, S.(2012), http://dx.doi.org/10.1016/j.cej.2012.06.1a b s t r a c t

Fusel oil is a mixture of C2C5 alcohols such as ethanol, n-propanol, iso-butanol and iso-amyl alcohol. It isexpected that reactive distillation (RD), which is a proven intensication strategy for esterication ofindividual alcohols can also be a promising option for simultaneous esterication of all the alcohols infusel oil. To evaluate its feasibility and design a unit on large scale, kinetic and phase equilibrium modelsare necessary. In this work, we experimentally investigate reaction kinetics for all the esterication andtrans-esterication reactions of the different constituents of fusel oil with acetic acid. The reactions areperformed in the presence of cation exchange resin, Amberlyst-15, in a batch reactor over a wide rangeof parameters such as temperature, mole ratio and catalyst loading. A unied LangmuirHinshelwoodHougenWatson (LHHW) model is proposed for the reacting system consisting of all the alcohols andthe experimental data is used to estimate the model parameters. The predictions are in line with theexperimental data for individual alcohols as well as their mixtures. A feasible process based on reactivedistillation is simulated in ASPEN PLUS using the kinetics developed in this work." A unied LHHW kinetic model is presented for the different reactions involved." Applicability of the developed kinetic model to a feasible RD process is shown.Esterication of fusel oil using reactive d

Prafull Patidar, Sanjay M. Mahajani Department of Chemical Engineering, Indian Institute of Technology, Powai, Mumbai 40

h i g h l i g h t s

" We present a process for value addition to fusel oil by esterication usi

Chemical Engi

journal homepage: wwll rights reserved.

M. Mahajani, Esterication of fu39tillation Part I: Reaction kinetics

6, India

D.

SciVerse ScienceDirect

ering Journal

elsevier .com/locate /cejsel oil using reactive distillation Part I: Reaction kinetics, Chem. Eng. J.

a liquid phase activity of species i

Engii

Ks,i adsorption constant of species iEf, Eb activation energy of forward and backward reaction,

kJ/kmolk0f ; k

0b Arrhenius pre-exponential factor for forward and

backward rate constant, kmol/kg skf, kb forward and backward reaction rate constants,

kmol/kg sMcat mass of catalyst, kgn initial molar holdupNfeed feed stage location in the distillation columnNreac reactive stage no. in the distillation columnNT total number of stages in the distillation columnQR reboiler dutyri rate of the reaction of species i, kmol/sR ideal gas constant, kJ/kmol Kt time, sT temperature, Kxi mole fraction of species i in the liquid phase

Greek lettermi stoichiometric coefcient for component i/ objective functionNomenclature

2 P. Patidar, S.M. Mahajani / ChemicalThe major constituents of fusel oil are ethanol, n-propanol, iso-butanol and iso-amyl alcohol and all are reactive under the condi-tions of interest. Since we are dealing with the reaction mixtureconsisting of alcohols and esters, trans-esterication reactions(see Eq. (2)) are also likely to take place simultaneously and theirimportance needs to be assessed.

CH3COOR R0OH\[Amberlyst-15

CH3COOR0 ROH 2

In all, four esterication and six trans-esterication reactions arepossible and are studied in the presentwork. The article is organizedas follows: First we review the information available in literature onthe kinetics of esterication of all the individual constituents offusel oil in the presence of ion exchange resin. The experimentalprocedure for the reaction kinetics is described and the generateddata is presented. A unied activity based LangmuirHinshel-woodHougenWatson (LHHW) kinetic model is proposed andthe relevant parameters are estimated. The model is further usedto simulate a feasible RD conguration for the esterication of fuseloil giving all the products in pure form. The experimental validationof reaction in RD and further optimization is out of the scope of thiswork and will be dealt with in the subsequent parts of this series.

2. Previous studies

The studies in esterication of acetic acid with different alco-hols of interest, over ion exchange resins, are reported by severalinvestigators, and are summarized in Table 2. Kirbaslar et al. [7]

Table 1A typical composition of the distilled fusel oil on water-free basis [5].

Component wt.%

Ethanol 12.4n-Propanol 3.5iso-Butanol 9.5iso-Amyl alcohol 74.6

Please cite this article in press as: P. Patidar, S.M. Mahajani, Esterication of f(2012), http://dx.doi.org/10.1016/j.cej.2012.06.139and Hangx et al. [8] have studied esterication of acetic acid withethanol in the presence of Amberlyst-15 and Purolite CT179, andproposed the kinetics models. However, their kinetic models donot take into account the activities of components. Calvar et al.[9] have studied the kinetics for this reaction, both when catalyzedhomogeneously by the acetic acid, and heterogeneously by Amber-lyst-15. Pseudo-homogeneous activity based models have beenproposed and are used to assess the performance of reactivedistillation.

AbbreviationsAcH acetic acidER EleyRideal modelEtAc ethyl acetateEtOH ethanolFID ame ionization detectorGC gas chromatographiAmAc iso-amyl acetateiAmOH iso-amyl alcoholiBuAc iso-butyl acetateiBuOH iso-butanolLHHW LangmuirHinshelwoodHougenWatson modelnPrAc n-propyl acetatenPrOH n-propanolPH pseudo-homogeneous modelRD reactive distillationSim simulationSSE sum of squares of errorsTCD thermal conductivity detectorVLE vaporliquid equilibrium

neering Journal xxx (2012) xxxxxxThe kinetics of esterication of acetic acid with n-propyl alcoholin the presence of ion exchange resins has also been reported [1013]. Rao and Bhagwat [10] used Dowex-50W cation exchange resinfor the reaction and interpreted the rate data using LangmuirHin-shelwood model, whereas, Bart et al. [11] proposed an activity-based EleyRideal (ER) model for this reaction catalyzed by cationexchange resin Dowex Monosphere 650C. Brehelin et al. [12] haveinvestigated the reaction in the presence of homogeneous (sulfuricacid) as well as heterogeneous (Amberlyst-15) catalyst and pro-posed the pseudo-homogeneous activity based models, which isfurther used in RD studies. Huang and Sundmacher [13] have mod-eled the same reaction in the presence of Amberlyst-15 usingactivity based ER and LHHW models. They have also providedguidelines to overcome the convergence problem encountered inthe estimation of the LHHW model parameters.

Altiokka and Citak [14] have proposed a concentration based ki-netic model to represent the esterication of acetic acid with iso-butanol in the presence of Amberlite IR-120. The EleyRidealmodel was found to be suitable for this reaction. Izci and Bodur[15] examined the progress of this reaction in 1,4-dioxan as a sol-vent using ion exchange resins Dowex 50Wx2 and Amberlite IR-120. They have reported the catalytic activity of Dowex 50Wx2to be higher than that of Amberlite IR-120. Korkmaz et al. [16] havestudied isobutyl acetate production by esterication in a pervapo-ration membrane reactor using different membranes in the pres-ence of Dowex 50W-X8 as catalyst. As regards to esterication ofacetic acid with isoamyl alcohol, only one systematic kinetic studywas found in the literature. Teo and Saha [17] used cation-ex-change resin catalyst, Purolite CT-175, for this reaction and corre-lated the kinetic data using activity-based LHHW model.

usel oil using reactive distillation Part I: Reaction kinetics, Chem. Eng. J.

ols

asedasedH

R

HH, E

ased

ased

11 Purolite CT-175 333363 K; 1 atm Activity-based LHHW

EngiIt can be seen that only a few investigators have reported thedata on esterication kinetics in the form of suitable activity basedmodels. Moreover, kinetic data on simultaneous esterication ofmixture of alcohols along with trans-esterication of different es-ters in the presence of ion exchange resins, has not been studied tilldate, to the best of our knowledge. Though all the estercationshave been studied in the presence of ion exchange resins, thereis no single resin that has been investigated for all the reactionsof interest. Hence, the models presented in the literature cannotbe applied in any form for the esterication of fusel oil. With thisbackground, the present work is undertaken to systematicallystudy and model the different esterication and trans-esterica-tion reactions involved in esterication of fusel oil with acetic acidin the presence of a commonly used strong cation exchange resin,Amberlyst-15. The kinetic data is correlated with the best suitedTable 2Summary of the work reported on ion exchange resin catalyzed esterication of alcoh

S. no. Ion exchange resinused as catalyst

Temperature andpressure range

Kinetic model

Esterication of ethanol1 Amberlyst-15 323353 K; 1 atm Concentration-b2 Purolite CT179 328338 K; 1 atm Concentration-b3 Amberlyst-15 303353 K; 1 atm Activity-based P

Esterication of n-propanol4 Dowex 50W 323343 K; 1 atm LHHW5. Dowex Monosphere

650C303343 K; 1 atm Activity-based E

6. Amberlyst-15 Not provided Activity-based P7 Amberlyst-15 338368 K; 1 atm Activity-based P

and LHHW

Esterication of iso-butanol8 Amberlite IR-120 318348 K; 1 atm Concentration-b

9 Dowex 50Wx2,Amberlite IR-120

318348 K; 1 atm Concentration-b

10 Dowex 50W-X8 333343 K; 1 atm

Esterication of iso-amyl alcohol

P. Patidar, S.M. Mahajani / Chemicalkinetic model that works for the mixture of alcohols in any propor-tion over a reasonably wide range of reaction conditions.

3. Experimental studies

3.1. Materials and catalyst

Ethanol, n-propanol, iso-butanol, iso-amyl alcohol, 2-ethylhexa-nol, n-propyl acetate (each >99 wt.%), and acetic acid (99.9 wt.%)are obtained from s.d. Fine Chem Ltd., India. iso-Butyl acetate andiso-amyl acetate (98% wt.%) are supplied by Loba Chemie Pvt.Ltd., whereas, iso-propyl alcohol (AR grade, moisture 900 rpm). We conrmed

sel oil using reactive distillation Part I: Reaction kinetics, Chem. Eng. J.

Table 3Kinetic rate expressions for different product esters, in the reaction of acetic acid with quaternary mixture of ethanol, n-propanol, iso-butanol and iso-amyl alcohol.

rEtAc 1McatdnEtAcdt

kf1aAcHaEtOH kb1aEtAcaH2O kf5aEtOHanPrAc kb5aEtAcanPrOH kf6aEtOHaiBuAc kb6aiBuOHaEtAckf7aEtOHaiAmAc kb7aiAmOHaEtAc

1Pall componentsKs;iai 2 3

rnPrAc 1McatdnnPrAcdt

kf2aAcHanPrOH kb2anPrAcaH2O kf5aEtOHanPrAc kb5aEtAcanPrOH kf8anPrOHaiBuAc kb8aiBuOHanPrAckf9anPrOHaiAmAc kb9aiAmOHanPrAc

1Pall componentsKs;iai 2 4

kf3aAcHaiBuOH kb3aiBuAcaH O kf6aEtOHaiBuAc kb6aEtAcaiBuOH kf8anPrOHaiBuAc kb8aiBuOHanPrAc

all c

iAm

P

4 P. Patidar, S.M. Mahajani / Chemical Engineering Journal xxx (2012) xxxxxxriBuAc 1McatdniBuAcdt

2

kf10aiBuOHaiAmAc kb10aiAmOHaiBuAc1P

riAmAc 1McatdniAmAc

dt

kf4aAcHaiAmOH kb4aiAmAcaH2O kf7aEtOHakf10aiBuOHaiAmAc kb10aiAmOHaiBuAc

1

0these ndings through few preliminary runs before systematicallygenerating the data on intrinsic kinetics.

3.5. Development of kinetic model and parameter estimation

The literature suggests that the activity based heterogeneous ki-netic models such as LHHW, are best suited for the reactions withion exchange resin as catalyst and hence the LHHWmodel is chosento explain the kinetic data generated in the present work. In thismodel, all the reactants and products are assumed to be adsorbedon the catalyst surface. Based on this assumption, rate expression

where; kf ;j kf ;j expEf ;j=RT

kb;j k0b;j expEb;j=RT; j indicates the reaction no: as arranged in

(a) (b

Fig. 1. Esterication of n-propyl alcohol with acetic acid. (a) Effect of temperature on the ccatalyst loading (w/w) on the conversion of acetic acid (temperature = 343 K, AcH:nPrO(temperature = 343 K, catalyst loading = 3%).

Please cite this article in press as: P. Patidar, S.M. Mahajani, Esterication of f(2012), http://dx.doi.org/10.1016/j.cej.2012.06.139omponentsKs;iai2 5

Ac kb7aEtAcaiAmOH kf9anPrOHaiAmAc kb9aiAmOHanPrAc

all componentsKs;iai2 6for various species involved in the reaction can be developed [21]to give kinetic rate expressions (Eqs. (3)-(6); Table 3) for differentproduct esters, in the reaction of acetic acid with quaternary mix-ture of ethanol, n-propanol, iso-butanol and iso-amyl alcohol. Sinceit is a liquid phase reaction, adsorption constants can be assumed tobe constant with respect to temperature. Reaction is assumed totake place only in the liquid phase owing to the fact that very smallamount of reactants are present in the vapor phase, which do notreact owing to the absence of catalyst there.

The rate expressions with respect to other components, i.e.reactants and water, can also be derived on similar lines. The

7

Table 4 8

) (c)

onversion of acetic acid (catalyst loading = 3% (w/w), AcH:nPrOH = 1:1); (b) effect ofH = 1:1); (c) effect of mole ratio, AcH:nPrOH, on the conversion of limiting reactant


developed kinetics can be used to predict concentration prolebetween any time interval t1 to t2 starting with the initial concen-tration at time t1. The activities of different components are calcu-lated using UNIQUAC thermodynamic model. It is observed in theexperiments that the system is highly non-ideal as the values ofactivity coefcient differ signicantly from unity for many compo-nents, although the variation in the values during the course ofreaction is not much for most of the components. For example,in most of the esterication experiments the values of activitycoefcient for acetic acid is below 1, for alcohols and esters be-tween 0.5 and 2, while that for water is between 2 and 3.5. The

kinetic parameters of the model, such as rate and adsorption con-stants with activation energy, are estimated by minimizing thesum of squares of error between the calculated values of molefractions of different components and that observed throughexperiments.

min/ X

samples

xi;cal xi;exp2 9

MATLAB function nlint, which is based on LevenbergMarquardtalgorithm, is used to perform the regression analysis.

(a) (b) (c)

Fig. 2. Esterication of ethanol with acetic acid. (a) Effect of temperature on the conversion of acetic acid (catalyst loading = 3% (w/w), AcH:EtOH = 1:1); (b) effect of catalystloading (w/w) on the conversion of acetic acid (temperature = 343 K, AcH:EtOH = 1:1); (c) effect of mole ratio, AcH:EtOH, on the conversion of limiting reactant(temperature = 343 K, catalyst loading = 3%).

(a) (b) (c)

Fig. 3. Esterication of iso-butyl alcohol with acetic acid. (a) Effect of temperature on the conversion of acetic acid (catalyst loading = 3% (w/w), AcH:iBuOH = 1:1); (b) effect ofcatalyst loading (w/w) on the conversion of acetic acid (temperature = 373 K, AcH:iBuOH = 1:1); (c) effect of mole ratio, AcH:iBuOH, on the conversion of limiting reactant(temperature = 373 K, catalyst loading = 3%).

(b)

P. Patidar, S.M. Mahajani / Chemical Engineering Journal xxx (2012) xxxxxx 5 (a)

Fig. 4. Esterication of iso-amyl alcohol with acetic acid. (a) Effect of temperature on theof catalyst loading (w/w) on the conversion of acetic acid (temperature = 373 K, AcH:iAmO(temperature = 373 K, catalyst loading = 3%).

Please cite this article in press as: P. Patidar, S.M. Mahajani, Esterication of fu(2012), http://dx.doi.org/10.1016/j.cej.2012.06.139 (c) conversion of acetic acid (catalyst loading = 3% (w/w), AcH:iAmOH = 1:1); (b) effectH = 1:1); (c) effect of mole ratio, AcH:iAmOH, on the conversion of limiting reactant


4. Results and discussion

4.1. Esterication reactions with acetic acid

As mentioned before, rst the experiments for the estericationof individual alcohols are carried out over the wide ranges oftemperature, catalyst loading and reactant mole ratio. As expected,the trends observed in the case of each alcohol are similar.

Fig. 1 shows the results obtained for n-propyl alcohol. The effectof temperature on the rate of the reaction is investigated over atemperature range of 343363 K under otherwise similar condi-

tions. As shown in Fig. 1a, the fractional conversion of acetic acidincreases with an increase in temperature. Fig. 1b shows the effectof catalyst loading on the rate of formation of n-propyl acetate,over a range of 325% w/w (wt. of catalyst/wt. of reactants). Therate increases linearly with an increase in catalyst loading overthe range studied. This can be attributed to a proportional increasein the number of active sites provided by the catalyst. Further, themole ratio of n-propyl alcohol to acetic acid is varied from 0.5:1 to2:1. As shown in Fig. 1c, the fractional conversion of the limitingreactant increases when either of the reactants is used in excessof the stoichiometric amount. As depicted in Figs. 24, similar

(a) (b) (c)

Fig. 5. Trans-esterication of n-propyl acetate with iso-butanol. (a) Effect of temperature on the conversion of iso-butanol (catalyst loading = 5% (w/w), nPrAc:iBuOH = 1:1);(b) effect of catalyst loading (w/w) on the conversion of iso-butanol (temperature = 348 K, nPrAc:iBuOH = 1:1); (c) effect of mole ratio, nPrAc:iBuOH, on the conversion oflimiting reactant (temperature = 358 K, catalyst loading = 5%w/w).

(a) (b) (c) Fig. 6. Trans-esterication of ethyl acetate with n-propanol. (a) Effect of temperature on the conversion of n-propanol (catalyst loading = 5% (w/w), EtAc:nPrOH = 1:1); (b)effect of catalyst loading (w/w) on the conversion of n-propanol (temperature = 343 K, EtAc:nPrOH = 1:1); (c) effect of mole ratio, EtAc:nPrOH, on the conversion of limitingreactant (temperature = 343 K, catalyst loading = 5%w/w).

)

6 P. Patidar, S.M. Mahajani / Chemical Engineering Journal xxx (2012) xxxxxx (a) (bFig. 7. Trans-esterication of isobutyl acetate with ethanol. (a) Effect of temperature on thcatalyst loading (w/w) on the conversion of ethanol (temperature = 348 K, EtOH:iBuAc(temperature = 348 K, catalyst loading = 5%w/w).

Please cite this article in press as: P. Patidar, S.M. Mahajani, Esterication of f(2012), http://dx.doi.org/10.1016/j.cej.2012.06.139 (c) e conversion of ethanol (catalyst loading = 5% (w/w), EtOH:iBuAc = 1:1); (b) effect of= 1:1); (c) effect of mole ratio, EtOH:iBuAc, on the conversion of limiting reactant


trends in the kinetics are realized in the case of esterication ofacetic acid with other alcohols.

4.2. Trans-esterication reactions

The experiments are carried out to study the possible individualtrans-esterication reactions of different alcohol-ester pairs. Againthe parameters like temperature, catalyst loading and reactantmole ratios are varied to generate sufcient data. The results areshown in Figs. 510 for the individual trans-estericationreactions. The trends are similar to esterication reactions, how-ever, these reactions are in general slower than the estericationreactions under otherwise similar conditions.

4.3. Reactions of mixture of alcohols with acetic acid

Some selective experiments are performed with binary, ternaryand quaternary mixtures of different alcohols and the data is alsoused for parameter estimation. Fig. 11a and b shows the resultsof esterication of binary mixture of ethanoliso-butanol and eth-anoliso-amyl alcohol pairs, while, Fig. 12a and b presents the datafor esterication of ternary mixtures of ethanoln-propanoliso-butanol, and ethanoliso-butanoliso-amyl alcohol with stoichi-ometric amounts of acetic acid. It is observed that in the mixture,ethanol has the highest reaction rate followed by n-propanol, iso-butanol and iso-amyl alcohol.

Table 4 gives the results of parameter estimation for LHHWkinetic model involving all the possible reactions. The values of

(a) (b) (c)

Fig. 8. Trans-esterication of isoamyl acetate with ethanol. (a) Effect of temperature on the conversion of ethanol (catalyst loading = 5% (w/w), EtOH:iAmAc = 1:1); (b) effectof catalyst loading (w/w) on the conversion of ethanol (temperature = 348 K, EtOH:iAmAc = 1:1); (c) effect of mole ratio, EtOH:iAmAc, on the conversion of limiting reactant(temperature = 348 K, catalyst loading = 5%w/w).

(a) (b) (c)

Fig. 9. Trans-esterication of iso-amyl acetate with n-propanol. (a) Effect of temperature on the conversion of n-propanol (catalyst loading = 5% (w/w), nPrOH:iAmAc = 1:1);(b) effect of catalyst loading (w/w) on the conversion of n-propanol (temperature = 348 K, nPrOH:iAmAc = 1:1); (c) effect of mole ratio, nPrOH:iAmAc, on the conversion oflimiting reactant (temperature = 348 K, catalyst loading = 5%w/w).

(

P. Patidar, S.M. Mahajani / Chemical Engineering Journal xxx (2012) xxxxxx 7 (a) Fig. 10. Trans-esterication of iso-butyl acetate with iso-amyl alcohol. (a) Effect of tiBuAc:iAmOH = 1:1); (b) effect of catalyst loading (w/w) on the conversion of iso-aiBuAc:iAmOH, on the conversion of limiting reactant (temperature = 358 K, catalyst load

Please cite this article in press as: P. Patidar, S.M. Mahajani, Esterication of fu(2012), http://dx.doi.org/10.1016/j.cej.2012.06.139b) (c) emperature on the conversion of iso-amyl alcohol (catalyst loading = 5% (w/w),myl alcohol (temperature = 348 K, iBuAc:iAmOH = 1:1); (c) effect of mole ratio,ing = 5% w/w).


Engi8 P. Patidar, S.M. Mahajani / Chemicalkinetic parameters obtained by regressing smaller data set, whichdoes not include the experimental data of individual alcohol reac-

Fig. 11. The variation in the compositions of various components with time du(AcH:EtOH:iBuOH = 2:1:1; temperature = 353 K; catalyst loading = 3 wt.%) (b) binary micatalyst loading = 3 wt.%).

Fig. 12. The variation in the compositions of various components with time during react(AcH:EtOH:iBuOH:AmOH = 3:1:1:1; temperature = 345 K; catalyst loading = 5 wt.%) (b) tmOH = 3:1:1:1; temperature = 348 K; catalyst loading = 5 wt.%).

Table 4Parameters of the proposed LHHW kinetic model obtained. The values reported are for 95

S. no. Reaction kf0 kb0

1 AcH EtOHH

EtAcwater 2.9047 106 2.26 104 1.0967 106

2 AcH nPrOHH

nPrAcwater 2.9075 106 5.73 104 6.7793 105

3 AcH iBuOHH

iBuAcwater 8.5577 105 1.26 104 1.1927 105

4 AcH iAmOHH

iAmAcwater 2.1835 105 3.29 103 9400.7 687.5 EtOH nPrAc

HEtAc nPrOH 1497.6 41.6 4320.8 49.4

6 EtOH iBuAcH

EtAc iBuOH 5016.1 217.8 1155.1 679.7 EtOH iAmAc

HEtAc iAmOH 1426.7 273.9 832.7 76.7

8 nPrOH iBuAcH

nPrAc iBuOH 2505.8 84.0 1339.3 26.09 nPrOH iAmAc

HnPrAc iAmOH 7251.2 891.1 2511.5 48.6

10 iBuOH iAmAcH

iBuAc iAmOH 966.9 135.3 2006.0 82.2

Please cite this article in press as: P. Patidar, S.M. Mahajani, Esterication of f(2012), http://dx.doi.org/10.1016/j.cej.2012.06.139neering Journal xxx (2012) xxxxxxtions, results in different numerical values of kinetic parameters,with the predictions being satisfactory over a reduced composition

ring reaction of acetic acid with: (a) binary mixture of ethanoliso-butanolxture of ethanoliso-amyl alcohol (AcH:EtOH:iAmOH = 2:1:1; temperature = 353 K;

ion of acetic acid with: (a) ternary mixture of ethanoliso-butanoliso-amyl alcoholernary mixture of n-propanoliso-butanoliso-amyl alcohol (AcH:nPrOH:iBuOH:A-

% condence interval.

Ef Eb Ks,i (SSE) 104

2.70 104 53047 32 59055 668 Ks,AA = 4.52 0.002 0.91 9.32 104 54596 12 59237 336 Ks,EtOH = 6.42 0.01 1.7 0.24 103 53016 71 58661 224 Ks,nPrOH = 6.05 0.12 2.541 47341 204 50739 597 Ks,iBuOH = 4.48 0.001 2.15

42962 75 45921 36 Ks,iAmOH = 2.56 0.003 0.45

5 49460 160 44237 1336 Ks,EtAc = 1.95 0.02 0.97

45648 529 42817 389 Ks,nPrAc = 1.68 0.12 1.02

47547 65 45011 57 Ks,iBuAc = 0.42 0.002 0.58

52420 411 48105 68 Ks,iAmAc = 0.29 0.001 0.25

47229 367 50321 82 Ks,H2O = 9.03 0.18 2.35


space. Further the reactionswith quaternarymixture are performedand the data is used to examine the reliability of the proposedmodel. Fig. 13a and b shows the comparison of the results of thereaction of quaternary mixture of alcohols with stoichiometricamount of acetic acid. Fig. 14 gives the parity plot comparing molefractions of limiting reactant, in all the different experiments per-formed, with that predicted by the proposed kineticmodel. The pre-dicted compositions for the different components agree reasonablywell with the experimental data.

5. Application of the kinetic model for reactive distillation

The developed kinetics is intended to be used for simulatingesterication of fusel oil using RD. Some preliminary RD simula-tions are performed using the developed kinetic models in RAD-FRAC module (equilibrium stage model) of ASPEN PLUSsimulator, for feed containing alcohol mixtures and acetic acid.The VLE model used is UNIQUAC-HOC with binary interactionparameters taken from ASPEN Databank. Fig. 15 shows one ofthe representative feasible congurations with stream composi-

Fig. 14. Parity plot showing comparison of predicted and experimental values ofthe mole fractions of limiting reactants in all the experiments.

P. Patidar, S.M. Mahajani / Chemical Engineering Journal xxx (2012) xxxxxx 9Fig. 13. Comparison between calculated and experimental mole fractions of (a) acetic acid and (b) other reactants, for the reaction of acetic acid with a quaternary mixture ofethanoln-propanoliso-butanoliso-amyl alcohol (AcH:EtOH:nPrOH:iBuOH:AmOH = 4:1:1:1:1; temperature = 348 K; catalyst loading = 5 wt.%).

Please cite this article in press as: P. Patidar, S.M. Mahajani, Esterication of fusel oil using reactive distillation Part I: Reaction kinetics, Chem. Eng. J.(2012), http://dx.doi.org/10.1016/j.cej.2012.06.139

f a f

Engitions and other results. In this conguration the rst column rep-resents the RD column with reaction taking place in the last two

Fig. 15. Schematic diagram showing simulation details o10 P. Patidar, S.M. Mahajani / Chemicalstages including reboiler. The product mixture is removed in theform of distillate and sent to other non-reactive distillation col-umns for further separation. As no product is withdrawn fromthe bottom, no stripping section is provided here. To check thesensitivity towards RD simulation results, the kinetic rate con-stants were varied by 10%. The suggested process congurationremains unaltered even in the changed conditions. A detailedstudy of different alternative process congurations for esterica-tion of fusel oil using RD, is in progress and will be covered in thesubsequent part of this series.

6. Conclusion

The reaction kinetics of esterication of acetic acid with etha-nol, n-propanol, iso-butanol and iso-amyl alcohol as well as theirmixtures over the cation-exchange resin, Amberlyst-15, are stud-ied. The kinetic data obtained in a batch reactor under various con-ditions are correlated using an activity-based LHHW model. Themodel explains the data successfully over a wide range of catalystloading and temperature for different esterication and trans-esterication reactions. The developed kinetic model is used forprocess simulation of esterication of fusel oil using reactive distil-lation and is shown that a process involving one reactive distilla-tion column and four non reactive distillation columns can besuccessfully used to obtain all the esters in pure form. The experi-mental validation and optimization of design and operatingparameters is the subject of future work.

References

[1] M.M. Sharma, S.M. Mahajani, Industrial applications of reactive distillation, in:K. Sundmacher, A. Kienle (Eds.), Reactive Distillation: Status and FutureDirections, Wiley-VCH, Weinheim, Germany, 2003, pp. 329.

Please cite this article in press as: P. Patidar, S.M. Mahajani, Esterication of f(2012), http://dx.doi.org/10.1016/j.cej.2012.06.139[2] A. Singh, R. Hiwale, S.M. Mahajani, R.D. Gudi, J. Gangadwala, A. Kienle,Production of butyl acetate by catalytic distillation: theoretical and

easible RD process for esterifying a mixture of alcohols.

neering Journal xxx (2012) xxxxxxexperimental studies, Ind. Eng. Chem. Res. 44 (2005) 30423052.[3] A. Singh, A. Tiwari, S.M. Mahajani, R.D. Gudi, Recovery of acetic acid from

aqueous solutions by reactive distillation, Ind. Eng. Chem. Res. 45 (2006)20172025.

[4] H.M. Brau, Review on origin and composition of fusel oil. Techical Paper no. 17,University of Puerto Rico Agriculture Experiment Station, April 1957, pp. 130.

[5] Z. Kucuk, K. Ceylan, Potential utilization of fusel oil: a kinetic approach forproduction of fusel oil esters through chemical reaction, Turk. J. Chem. 22(1998) 289300.

[6] A.G. Patil, S.M. Koolwal, H.D. Butala, Fusel oil: composition, removal, andpotential utilization, Int. Sugar J. 104 (2002) 5158.

[7] S.I. Kirbaslar, Z.B. Baykal, U. Dramur, Esterication of acetic acid with ethanolcatalyzed by an acidic ion-exchange resin, Turk. J. Eng. Environ. Sci. 25 (2001)569577.

[8] G. Hangx, G. Kwant, H. Maessen, P. Markusse, I. Urseanu, Reaction kinetics ofthe esterication of ethanol and acetic acid towards ethyl acetate, TechnicalReport to the European Commission, 2001. .

[9] N. Calvar, B. Gonzalez, A. Dominguez, Esterication of acetic acid with ethanol:reaction kinetics and operation in a packed bed reactive distillation column,Chem. Eng. Process. 46 (2007) 13171323.

[10] K.D. Rao, M. Bhagwat, Kinetics of esterication of n-propyl alcohol with aceticacid catalyzed by Dowex-50W, Indian J. Technol. 22 (1984) 268271.

[11] H.J. Bart, W. Kaltenbrunner, H. Landschutzer, Kinetics of esterication of aceticacid with propyl alcohol by heterogeneous catalysis, Int. J. Chem. Kinet. 28(1996) 649656.

[12] M. Brehelin, F. Forner, D. Rouzineau, J.U. Repke, X. Meyer, M. Meyer, et al.,Production of n-propyl acetate by reactive distillation: experimental andtheoretical study, transactions of the IChemE, part A, Chem. Eng. Res. Des.85(A1) (2007) 109117.

[13] Y.S. Huang, K. Sundmacher, Kinetics study of propyl acetate synthesis reactioncatalyzed by Amberlyst-15, Int. J. Chem. Kinet. 39 (5) (2007) 245253.

[14] M.R. Altokka, A. tak, Kinetics study of esterication of acetic acid withisobutanol in the presence of Amberlite catalyst, Appl. Catal. A 239 (2003)141148.

[15] A. Izci, F. Bodur, Liquid-phase esterication of acetic acid with isobutanolcatalyzed by ion-exchange resins, React. Funct. Polym. 67 (2007) 14581464.

[16] S. Korkmaz, Y. Salt, S. Dincer, Esterication of acetic acid and isobutanol in apervaporation membrane reactor using different membranes, Ind. Eng. Chem.Res. 50 (2011) 1165711666.

[17] H.T.R. Teo, B. Saha, Heterogeneous catalysed esterication of acetic acidwith isoamyl alcohol: kinetic studies, J. Catal. 228 (2004) 174182.


[18] Z.P. Xu, K.T. Chuang, Effect of internal diffusion on heterogeneous catalyticesterication of acetic acid, Chem. Eng. Sci. 52 (1997) 30113017.

[19] J. Gangadwala, S. Mankar, S. Mahajani, A. Kienle, E. Stein, Esterication ofacetic acid with butanol in the presence of ion-exchange resins as catalysts,Ind. Eng. Chem. Res. 42 (2003) 21462155.

[20] S.H. Ali, S.Q. Merchant, Kinetics of the esterication of acetic acid with 2-propanol: impact of different acidic cation exchange resins on reactionmechanism, Int. J. Chem. Kinet. 38 (2006) 593613.

[21] H.S. Fogler, Elements of Chemical Reaction Engineering, third ed., Prentice Hall,Englewood Cliffs, NJ, 1999.

P. Patidar, S.M. Mahajani / Chemical Engineering Journal xxx (2012) xxxxxx 11Please cite this article in press as: P. Patidar, S.M. Mahajani, Esterication of fu(2012), http://dx.doi.org/10.1016/j.cej.2012.06.139sel oil using reactive distillation Part I: Reaction kinetics, Chem. Eng. J.

Esterification of fusel oil using reactive distillation Part I: Reaction kinetics1 Introduction2 Previous studies3 Experimental studies3.1 Materials and catalyst3.2 Analysis3.3 Apparatus and procedure3.4 Elimination of mass transfer resistance3.5 Development of kinetic model and parameter estimation

4 Results and discussion4.1 Esterification reactions with acetic acid4.2 Trans-esterification reactions4.3 Reactions of mixture of alcohols with acetic acid

5 Application of the kinetic model for reactive distillation6 ConclusionReferences

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