Amberlyst 15 Catalyzed Esterification of Nonanoic Acid with 1

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Amberlyst 15 Catalyzed Esterification of Nonanoic Acid with 1‑Propanol: Kinetics, Modeling, and Comparison of Its Reaction Kinetics with Lower Alcohols Mamta Sharma,† R. K. Wanchoo,†,‡ and Amrit Pal Toor*,‡ †

Energy Research Centre and ‡University Institute of Chemical Engineering and Technology, Panjab University, Chandigarh 160014, India ABSTRACT: A comprehensive kinetic investigation of the esterification of nonanoic acid with 1-propanol in the liquid phase was carried out using Amberlyst 15. Kinetic experiments were conducted using a batch reactor system at a stirrer speed of 500 rpm over the temperature range 323.15 −363.15 K. The catalyst loading was varied from 4% (w/v) to 8% (w/v), and acid to alcohol molar ratios of 1:1, 1:5, 1:10, and 1:15 were used. It was found that both external and internal diffusion limitations did not affect the overall reaction rate. The conversion of nonanoic acid increased with increasing temperature and catalyst loading. The Eley−Rideal (E−R) model was tested to correlate the kinetic data, and the activity coefficients were estimated using the UNIFAC model to account for the nonideal thermodynamic behavior of reactants and products. The model predicted the kinetic behavior of the studied system reasonably well. Water was found to be more strongly adsorbed than other species present in the system. The activation energy, preexponential factor, and standard enthalpy for the esterification was estimated to be 55.4 kJ/ mol, 2.3 × 105 L2 g−1 mol−1 h−1, and −218.08 J·mol−1, respectively, by this model. The influence of alcohol carbon chain length was studied, and their effects on reaction kinetics were compared. It was observed that activation energy increases with increases in chain lengths of alcohols. The exchange resins are subjected to remarkable swelling9−12 in the presence of polar substances. This phenomenon must be carefully considered in a kinetic approach. The liquid composition inside an exchange resin particle could be quite different with respect to the liquid bulk. We have studied the importance of this aspect in our previous work,2 where we have shown the effect of water and alcohol concentrations on esterification reaction has been elucidated. The nonideality of each species in liquid mixtures was represented by the activity coefficient, which is usually calculated from a solution model with the binary parameters determined from phase-equilibrium data. If the phaseequilibrium data are unavailable in the literature, a groupcontribution method, for example, the UNIFAC model,17 is a common choice for these purposes. Propyl nonanoate is used in chemical industries as a chemical intermediate for synthetic flavors, cosmetics, pharmaceuticals, and corrosion inhibitors. At present no information is available in the open literature describing the kinetics of nonanoic acid esterification with 1-propanol in the presence of ion-exchangeresin catalysts and comparison of its reaction kinetics with lower alcohols. Thus, we have conducted isothermal experimental batch studies on the esterification of nonanoic acid with 1-propanol in the presence of Amberlyst 15 ion-exchange resin as catalyst. The general reaction mechanism for this reaction is given in Scheme 1.

1. INTRODUCTION Ion-exchange-resin catalysts have been used for years in esterification processes and are the most commonly used solid catalysts. They have been proved to be effective in liquid phase esterification.1,2 Typical resin catalysts are sulfonic acids fixed to polymer carriers, such as polystyrene cross-linked with divinylbenzene (DVB). Solid ion-exchange resins as catalysts have several advantages:3−6 the catalyst can be removed from the reaction product; continuous operation in column reactors is enabled; the product purity is high, since side reactions can be suppressed or completely eliminated; reaction intermediates can be isolated; and, furthermore, ion-exchange resins can discriminate between small and large molecules.7,8 However, most of the recent studies use heterogeneous solid catalysts, such as acid ion-exchange resins, which can avoid the drawbacks of homogeneous catalysts, such as equipment corrosion and side reactions. But despite so many advantages, one of the challenges in determining kinetics parameters for the esterification over solid acid catalysts is the proper study of the water concentration. The water present in the reaction mixture limits the conversion not only due to thermodynamic equilibrium, but also by its adsorption on the active catalytic sites. For studies on ion-exchange resins, the reader may refer to the works of various authors, including Schmid et al.9 for esterification of ethylene glycol with acetic acid catalyzed by Amberlyst 36, Seo et al.10 for esterification of lactic acid with methanol in the presence of cation-exchange resin using a pseudohomogeneous model, and Izci et al.,11 Roy et al.,12 Teo and Saha, 13 Kirumakki et al.,14 and Yijun et al. 15 For a more recent review, the reader is referred to the work of Lee et al.16 and Sharma et al. 2 © 2014 American Chemical Society

Received: Revised: Accepted: Published: 2167

July 26, 2013 October 28, 2013 January 10, 2014 January 10, 2014 dx.doi.org/10.1021/ie402407r | Ind. Eng. Chem. Res. 2014, 53, 2167−2174

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catalytic tests were performed at least three times in order to ensure reproducible results. The experimental setup is shown in Figure 1. The samples for analysis were taken at time intervals whose duration, relatively short at the beginning, successively increased with the decreasing reaction rate. 2.3. Analysis. For kinetic measurements, samples were taken periodically and the amount of nonanoic acid was determined by titration with a standard 0.5 N sodium hydroxide solution, using phenolphthalein as an indicator. Parallel tests indicated that the average error of the titration method was less than 2%. The results obtained were also confirmed by a gas chromatograph (Nucon 5765) equipped with a fused silica capillary column of 30 m × 0.25 mm i.d. × 0.25 μm film thickness, flame ionization detector, and a thermal conductivity detector by matching the retention time of the reaction product to the retention time of propyl nonanoate. Nitrogen with a purity of 99.99% was used as the carrier gas. The results were comparable.

Scheme 1

2. EXPERIMENTAL SECTION 2.1. Chemicals and Catalysts. Nonanoic acid (purity >99.5), 1-propanol (purity >99), and 1,4-dioxane were purchased from Merck and used without further purification. Heterogeneous catalyst Amberlyst 15 (wet) was obtained from Rohm and Hass. The purity of all chemicals was checked by gas chromatography. The catalyst was initially washed with distilled water four to five times and was dried at ambient conditions for 4−5 h. Further the catalyst was washed by dipping in 0.1 N hydrochloric acid solution for 1/2 h. This solution was then filtered to separate the catalyst and dried at atmospheric conditions for about 48 h. 2.2. Apparatus and Reaction Procedure. Batch experiments were carried out in a 500 mL double jacketed glass reactor. The reaction temperature was maintained using a thermostatic water bath (Julabo F20). The temperature was maintained within an accuracy of ±0.1 °C and a reflux condenser was used to avoid the loss of volatile components. The reaction mixture was continuously stirred with an overhead stirrer with motor. The nonanoic acid and the catalyst were first charged into the reactor through a peephole on the lid and heated to the desired temperature. Then 1-propanol at the same temperature was fed into the reactor. The time at which 1-propanol was added was considered to be zero time. All

3. RESULTS AND DISCUSSION 3.1. Influence of External Mass Transfer. The optimal stirrer speed was determined before other experiments were carried out by repeating experimental runs with different stirrer speeds. Figure 2 shows the conversion of nonanoic acid versus time at three different speeds of 300, 500, and 800 rpm at an acid to alcohol molar ratio of 1:10, temperature of 363.15 K, and Amberlyst 15 loading of 8% (g/L). It is seen that the rate of the reaction as followed by the conversion of nonanoic acid is the same when the mixture is agitated at speeds of 500 and 800 rpm. This indicates the absence of external mass transfer limitations above 500 rpm. Therefore, all experiments were

Figure 1. Experimental setup of batch reactor for the esterification reaction of nonanoic acid with 1-propanol over Amberlyst 15. 2168

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Table 1. Significance of Pore Diffusion for the Different Systems Catalyzed by Amberlyst 15 exptl params A/B/Ca

DA × 10−6 (cm2/s)

DE × 10−7 (cm2/s)

φ × 10−6

η

41.00/363.15/10 49.20/363.15/10 57.47/363.15/10 65.66/363.15/10 73.87/363.15/10 65.66/323.15/10 65.66/333.15/10 65.66/343.15/10 65.66/353.15/10

4.851 4.851 4.851 4.851 4.851 4.316 4.450 4.583 4.717

5.821 5.821 5.821 5.821 5.821 5.180 5.340 5.500 5.661

4.760 4.760 4.760 4.760 4.760 1.528 5.559 6.297 9.615

1 1 1 1 1 1 1 1 1

a

A, catalyst loading in g/L; B, temperature in K; C, acid to alcohol mole ratio.

Figure 2. Plot of fractional conversion vs speed of agitation at 363.15 K, 1:10 molar ratio, and catalyst loading 8% (w/v).

conducted at 500 rpm so as to neglect the effect of external mass transfer and to avoid the breakage of catalyst at higher rpm. 3.2. Influence of Internal Mass Transfer. The influence of internal mass transfer resistances in the case of Amberlyst 15 catalyzed esterification was evaluated by first calculating the observable modulus (ηφ2) and implementation of the Weisz− Prater criterion (ηφ2 ≪ 1) for each experiment.18 φ=

ro 2k 9De

(1)

where ro and De denote the radius of catalyst particle and the effective diffusion coefficient, respectively, k is the reaction rate constant, and φ is the Thiele modulus. If the calculated value of φ was less than 1, the internal diffusion could be neglected.19 The effective diffusion coefficient was defined as follows: εD De = A (2) τ where DA is the liquid phase diffusion coefficient, τ is the particle tortuosity, and ε is the porosity. For most resin catalysts, the values of ε/τ are between 0.12 and 0.50.19 In this study, the value of ε/τ for Amberlyst 15 was taken as 0.12.2 The liquid phase diffusion coefficient DA can be evaluated from the Wilke−Chang equation.18 Taking the initial rate as the maximum rate for each experiment, calculating the liquid phase diffusion coefficient DA of nonanoic acid in 1-propanol is based on Weisz−Prater criteria; the value of φ (Thiele modulus) is found to be less than 1 and the value of the effectiveness factor, i.e., η, is found to be almost unity (shown in Table 1). Hence, interestingly, no pore diffusion limitation was detected. 3.3. Effect of Catalyst Loading. Catalyst loading was varied from 4% (w/v) to 8% (w/v) at a temperature 363.15 K, molar ratio 1:10 (acid:alcohol), and stirrer speed of 500 rpm for a period of 6 h. The conversion of nonanoic acid as a function of time with different catalyst loadings is shown in Figure 3. As can be seen from Figure 3, with increasing catalyst loading the conversion of nonanoic acid increases because of the increase in the total number of available active catalytic sites for the reaction. From Figure 3 it is evident that the fractional conversion of nonanoic acid is almost constant as the catalyst loading is increased after 8% (w/v); hence it is not very practical to use more than 8% (w/v) catalyst loading because

Figure 3. Fractional conversion vs time for different catalyst loadings at molar ratio 1:10, temperature 363.15 K, and 500 rpm.

there is not much effect of catalyst loading after 8% (w/v). The same results were obtained by Teo and Saha.13 Hence it can be concluded that the optimum catalyst loading based on the current finding was taken as 8% (w/v). 3.4. Effect of Temperature. To investigate the temperature effect of the esterification reaction, the reactions were carried out in the temperature region of 323.15−363.15 K while keeping the molar ratio of acid to alcohol at 1:10. The conversion versus time graph belongs to experiments that were carried out at 323.15, 333.15, 343.15, 353.15, and 363.15 K to determine the reaction rate constants and is depicted in Figure 4. In general, the acid conversion was found to increase with increasing reaction temperature. Increasing the temperature is apparently favorable for the acceleration of the forward reaction. The conversion value becomes almost double when the temperature of the reactant is increased from 323.15 to 363.15 K. 3.5. Effect of Feed Molar Ratio. Esterification of nonanoic acid with 1-propanol is an equilibrium limited chemical reaction, and the position of equilibrium controls the amount of ester formed. The use of an excess of 1-propanol drives the equilibrium toward the formation of ester and enhances the forward reaction. The initial molar ratio of 1-propanol to nonanoic acid was varied from 1:1 to 15:1 at a temperature 363.15 K, 8% (g/L) catalyst loading, and stirrer speed of 500 rpm. Acid conversion increases with the increase in the amount of 1-propanol under otherwise similar conditions as is evident from Figure 5 2169

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Figure 4. Fractional conversion vs time for different temperatures at molar ratio 1:10, catalyst loading 8% (w/v), and 500 rpm.

Figure 6. Initial rate of reaction (−rA,o) vs activity of nonanoic acid (aA,o) at three different temperatures: ◆, 363.15 K; ■, 348.15 K; ▲, 338.15 K. Catalyst loading 6% (w/v), 500 rpm.

Figure 5. Fractional conversion vs time for different molar ratios at temperature 363.15 K, catalyst loading 8% (w/v), and 500 rpm. Figure 7. Initial rate of reaction (−rA,o) vs activity of 1-propanol (aB,o) at three different temperatures: +, 363.15 K; ■, 348.15 K; ▲, 338.15 K. Catalyst loading 6% (w/v), 500 rpm.

3.6. Mathematical Model for Esterification Kinetics. To study the effect of initial concentrations of reacting components, experiments were carried out in the presence of Amberlyst 15 catalyst at the three different temperatures of 363.15, 348.15, and 338.15 K using 1,4-dioxane as solvent at 500 rpm. The initial rate of reaction (rA,o) defined up to a conversion of 10% was observed using different concentrations of nonanoic acid, 1-propanol, and water. The concentrations were expressed in terms of activities so as to account for the nonideal behavior of the reaction mixtures.2 As can be seen from Figure 6, that initial reaction rate is a linear function of the initial activity of nonanoic acid rather than producing a figure of a plateau, giving evidence that nonanoic acid is not adsorbed over the surface of Amberlyst 15 beads. Figure 7 shows that the initial reaction rate increases linearly with increasing 1-propanol activity whereas at high 1-propanol activity the rate is essentially independent of it; hence we can conclude that the adsorption effect of 1-propanol is very low at low concentrations of 1propanol and it almost becomes constant as the concentration is increased further. Figure 8 shows that the initial reaction rate is a nonlinear function of the activity of water and decreases with an increase in the activity of water, hence confirming the inhibiting effect of the water concentration as the reaction proceeds. From this analysis, it is concluded that the reaction

Figure 8. Initial rate of reaction (−rA,o) vs activity of water (aW,o) at three different temperatures: ◆, 363.15 K; ■, 348.15 K; ▲, 338.15 K. Catalyst loading 6% (w/v), 500 rpm.

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mechanism can be represented by the Eley−Rideal model; i.e., the reaction occurs between adsorbed molecules of 1-propanol and the molecules of nonanoic acid in the bulk solution. In addition to this, water molecules adsorbed by the resin have an inhibiting effect on the reaction rate. The adsorption of solvent (dioxane) and ester were reported to be negligible in the literature.18 Therefore, the stoichiometric and corresponding reaction rate expression in the form of the Eley−Rideal model with surface reaction is the rate-determining step, and after excluding the adsorption terms of nonanoic acid and propyl nonanoate, the reaction equation can be written as −ri =

k f wcat(aA aB − (aEaW /Ke)) 1 + KBaB + KW aW

(3) Figure 10. Plot of (aA,oaB,o)/(−rA,o) versus aW,o for alcohol at three different temperatures: ◆, 363.15 K; ■, 348.15 K; ▲, 338.15 K. Catalyst loading 6% (w/v), 500 rpm.

kf is the forward reaction rate constant in mol·L/(g min) and is given as ki = ki° exp(−Ei/RT), wcat is the weight of catalyst in g/ L, and Ke is the esterification reaction equilibrium constant in terms of activity catalyzed by Amberlyst 15. In eq 3, activity rather than concentration is used in the rate expression, because it results in improvement in the prediction of the model fitted against the measured kinetic data. Using eq 3, the initial reaction rate, with no product present, can be defined as

From Figures 9 and 10 the rate constants and adsorption constants kf, KB, and KW are obtained and their estimated values at three temperatures are tabulated in Table 2. Table 2. Kinetics and Adsorption Parameters

−rA,o =

k f wcataB,o 1 + KBaB,o

aA,o

temp (K)

(4)

338 348 363

These lines are presented in Figure 6 at different temperatures. If eq 4 is rearranged, the following expression can be obtained: aA,oaB,o −rA,o

=

⎛ k ⎞ 1 + ⎜ B ⎟aB,o k f wcat ⎝ k f wcat ⎠

kf (L2/mol·g·h) −4

6.5 × 10 1.1 × 10−3 2.5 × 10−3

KB

KW

0.50 0.17 0.11

1.82 1.61 1.38

3.7. Activation Energy. The effect of temperature on the rate of reaction was studied by conducting the reactions at different temperatures from 323.15 to 363.15 K under the conditions of a catalyst loading of 8% (g/L), molar feed ratio (acid to alcohol) of 1:10, and stirrer speed of 500 rpm. The temperature dependency of the rate constant is expressed by the Arrhenius law:

(5)

A plot of (aA,oaB,o)/(−rA,o) versus aB,o produces a straight line with the slope of kB/(kfwcat) and intersection of 1/(kfwcat). These lines are presented in Figure 9 at different temperatures. Rearranging eq 3 to check the inhibiting effect of water, a plot of (aA,oaB,o)/(−rA,o) versus aW,o results in a straight line with the slope of KW/(kfwcat) and intercept (1 + KBaB,o)/ (kfwcat) as shown in Figure 10.

ki = ki° exp( −Ei /RT )

(6)

Ei is activation energy and ki° is the frequency factor. From eq 6, A plot of ln kf, ln KB, and ln KW versus 1/T gives a straight line with the slope of E/R, as shown in Figures 11 and 12. The activation energy of the reaction was found to be 55.4 kJ·mol−1 in the presence of Amberlyst 15. Applying the Arrhenius

Figure 9. Plot of (aA,oaB,o)/(−rA,o) versus aB,o for ethanol at three different temperatures: ◆, 363.15 K; ■, 348.15 K; ▲, 338.15 K. Catalyst loading 6% (w/v), 500 rpm.

Figure 11. Plot of ln kf vs 1/T for catalyst loading 6% (w/v) and 500 rpm. 2171

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Figure 12. Plots of ln KB and ln KW vs 1/T for catalyst loading 6% (w/ v) and 500 rpm: ◆, ln KW; ■, ln KB. Figure 13. Plot of ln Ke vs 1/T for catalyst loading 8% (w/v) and 500 rpm.

equation, the rate constant kf and adsorption constants KB and KW can be correlated by the following expressions: ⎡ 6659.4 ⎤ k f (L /g of dry resin mol h) = exp⎢12.36 − ⎥ ⎣ T ⎦

(7)

⎤ ⎡ 799.25 KB (L/mol) = exp⎢ − 2.62⎥ ⎦ ⎣ T

(8)

⎤ ⎡ 2319.9 KW (L/mol) = exp⎢ − 5.91⎥ ⎦ ⎣ T

(9)

On comparing eqs 11 and 12, it is observed that the reaction enthalpy ΔHr and reaction entropy ΔSr are −218.08 J·mol−1 and 624.9 J K−1 mol−1, respectively. Furthermore, the liquid phase reaction free energy change can be calculated to be ΔGr = ΔHr − TΔSr = −227 058.6 J·mol−1. 3.9. Model Prediction. The observed reaction rate for the esterification of nonanoic acid with 1-propanol was compared with the proposed Eley−Rideal model (eq 3) using the rate consants given in Table 2 over the whole range of predicted parameters. Experimental data were calculated by eq 13, also explained in our previous work by Sharma et al.2

2

3.8. Chemical Equilibrium Constant, Reaction Enthalpy, Entropy, and Free Energy. In principle, the chemical equilibrium constant can be determined either by the thermodynamic data (the enthalpies and free energies of formation of all components, ΔHf and ΔGf) or by long-time experiments. However, the estimation based on the thermodynamic data is usually much less reliable because a small deviation in ΔHf and ΔGf can lead to a relatively large error in the reaction enthalpy ΔHr and the reaction free energy ΔGr, and thus the equilibrium constant Ke. Moreover, for the considered reaction system, the necessary thermodynamic data for propyl nonanoate are not available; therefore, the equilibrium constant is determined experimentally. The equilibrium constant in terms of activity coefficients can be calculated from the following equation: ⎛ C C ⎞⎛ γ γ ⎞ Ke = ⎜ E W ⎟⎜⎜ E W ⎟⎟ = Ke, CKe, γ ⎝ CAC B ⎠⎝ γAγB ⎠

−rA,experimental =

ΔC ΔX = CA Δt Δt

(13)

The parity plot between the experimental and calculated rates of reaction (−rA) is given in Figure 14. The model equation (5) represents the data reasonably well. 3.10. Effect of Carbon Chain Length of Alcohol. Esterification of nonanoic acid was carried out with methanol,2 ethanol,20 and 1-propanol using Amberlyst 15 catalyst by our research group. To understand the alcohol reactivity used in the reaction, the data for all three alcohols at similar conditions of

(10)

where Ke,C is the constant in terms of concentration and Ke,γ is the constant in terms of activity coefficients. The constant Ke,C was computed using the equilibrium concentrations of the individual components of the reaction mixture. The temperature dependence of Ke can be found by the plot of ln Ke versus the reciprocal temperature (1/T) as shown in Figure 13. −26.231 + 75.163 (11) T The reaction enthalpy ΔHr and entropy ΔSr can be estimated by using the van’t Hoff19 equation given below: ln Ke =

ln Ke =

−ΔHr ΔSr + RT R

Figure 14. Parity between observed rate of reaction, −rA(experimental), and predicted rate of reaction, −rA(predicted), over Amberlyst 15, in the catalyst range 4−11% (w/v), molar ratio range 1:1−1:15, temperature range 338.15−363.15 K, at 500 rpm.

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of the alcohol increases. According to Yeramian et al.,21 primary alcohol reacts faster than secondary alcohol and the latter reacts faster than tertiary alcohol once catalyzed by ion-exchange resins. Within each series, the reaction rate generally decreases with increasing molecular weight. Straight-chain alcohols react more readily than those branched once; in particular, branching in the α-position lowers the rate of esterification. Our results are in accordance with their study.

temperature (333.15 K), molar ratio of alcohol/acid (1:10), and amount of catalyst of (8% (w/v)) were compared. From these data it is observed that the forward rate constant and fractional conversion of nonanoic acid with methanol is the highest and it decreases with the increase in the chain length; the alcohol reactivity follows the order methanol > ethanol >1propanol. As shown in Figures 15 and 16 and Table 3, the

4. CONCLUSION For the esterification of nonanoic acid with 1-propanol, Amberlyst 15 as catalyst was investigated. A stirrer speed of ≥400 rpm was found to be effective in eliminating external diffusion limitations. Hence, the effects of catalyst loading, temperature, and acid to alcohol molar ratio on reaction kinetics were determined at 500 rpm. Internal diffusion limitations were assessed by the Weisz−Prater criterion and found to be absent. For all the reactions, increase in the acid to alcohol molar ratio increases the conversion of acid and this enhancement in kinetics is more pronounced when the molar ratio is raised from 1:10 than when it is raised from 1:1. Under the conditions studied, the increase in the catalyst loading is found to increase the percent conversion of nonanoic acid. The UNIFAC model was found to predict component activity coefficients reasonably well. The Eley−Rideal model was developed to interpret the obtained kinetic data. The parity plot between experimental and calculated −rA,o values obtained proves the success of the UNIFAC model in predicting the activity coefficients of the components present in the system. The activation energy for the forward reaction was found to be 55.4 kJ·mol−1 for the ER model catalyzed by Amberlyst 15.

Figure 15. Reactivity of alcohols: 1, CH3OH (C1); 2, CH3CH2OH (C2); 3, CH3CH2CH2OH (C3). ◆, 1 h; ■, 3 h; △, 5 h; ×, 7 h. Reaction temperature 333.15 K; catalyst loading 8% (g/L); molar ratio 1:10.

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS We gratefully acknowledge the financial support received from UGC (Government of India) vide Project No. F.No.37-295/ 2009 (SR).

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Figure 16. Activation energies for (◇) methanol, (□) ethanol, and (△) 1-propanol.

Table 3. Kinetics and Adsorption Parameters for All Alcohols at 333.15 K kf (L2/mol·g·h) 2

methanol ethanol20 1-propanol

−3

1.2 × 10 5.6 × 10−4 4.8 × 10−4

KB

KW

EA (kJ·mol−1)

0.25 0.67 0.80

1.18 1.71 2.85

47.6 53.7 55.4

conversion of nonanoic acid with methanol, ethanol, and 1propanol is 29, 19, and 11%, respectively, after a reaction time of 1 h and reaches 82, 52, and 45%, respectively, in 7 h. This shows that the fractional conversion of nonanoic acid is greater with methanol at the same reaction temperature. From Table 3 we can conclude that the activation energy and adsorption effect of alcohol and water increase as the carbon chain length 2173

NOTATION a = activity A = nonanoic acid B = 1-propanol E = ester W = water EA = activation energy, kJ·mol −1 ko = preexponential factor, mol·L·g−1·min−1 kf = forward reaction rate constant, mol·L·g−1·min−1 wcat = weight of catalyst, g·L−1 T = absolute temperature, K t = reaction time, min C = concentration γ = activity coefficient ΔGr = reaction free energy change, J/mol ΔHr = reaction enthalpy ΔSr = reaction entropy ln = natural logarithm (base e) R = 8.314 J/mol/K dx.doi.org/10.1021/ie402407r | Ind. Eng. Chem. Res. 2014, 53, 2167−2174

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(20) Sharma, M.; Toor, A. P.; Wanchoo, R. K. Reaction Kinetics of Catalytic Esterification of Nonanoic Acid with Ethanol over Amberlyst 15. Int. J. Chem. React. Eng. 2014; under review. (21) Yeramian, A. A.; Gottifredi, J. C.; Cunningham, R. E. Vaporphase reactions catalyzed by ion exchange resins: II. Isopropanol-acetic acid esterification. J. Catal. 1968, 12, 257.

ER = Eley−Rideal model rpm = revolutions per minute UNIFAC = universal quasichemical functional group activity coefficients

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REFERENCES

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dx.doi.org/10.1021/ie402407r | Ind. Eng. Chem. Res. 2014, 53, 2167−2174