Kinetic Study Of Homogeneous Catalyzed Esterificationof Series Of Aliphatic Acids With Different Alcohols.pdf

Subscriber access provided by AUT Library

Kinetics, Catalysis, and Reaction Engineering

Kinetic study of homogeneous catalyzed esterification of series of aliphatic acids with different alcohols Abha Sahu, and Aniruddha Bhalchandra Pandit Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/acs.iecr.8b04781 • Publication Date (Web): 24 Jan 2019 Downloaded from http://pubs.acs.org on January 26, 2019

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 33 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Industrial & Engineering Chemistry Research

1

Kinetic study of homogeneous catalyzed esterification of series of aliphatic acids with

2

different alcohols

3

Abha Sahu1, Aniruddha B. Pandit 1*

4 5 6

1Chemical

Engineering Department, Institute of Chemical Technology, Mumbai 400019, India.

7 8 9 10 11 12 13 14 15 16 17

*Author to whom correspondence should be addressed

18

Email: [email protected], [email protected]; Tel: +91-22-3361 2012; Fax:

19

+91-22-33611020

20 1 ACS Paragon Plus Environment

Industrial & Engineering Chemistry Research 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 2 of 33

1

Abstract:

2

The kinetic study of esterification of series of aliphatic carboxylic acid (C1-C5) with various

3

alcohols (n-propanol, isopropanol, and n –butanol) have been conducted using sulphuric acid

4

as a catalyst in batch experiments. Effects of variables such as reaction temperature, catalyst

5

loading and initial mole ratio of reactants were investigated in detail. Temperature

6

dependence reaction rates and activation energies were determined by the Arrhenius plot.

7

Impact and reactivity of the series of linear chain length of carboxylic acids on esterification

8

reactions were investigated in terms of steric and polar effects of the α substituents on the

9

carboxylic group.

10

Keywords: Esterification, homogeneous system, acid catalyst, sulphuric acid, kinetic model,

11

activation energy, frequency factor, Taft equation and Charton correlation.

12

1. Introduction:

13

In the chemical industry, esterification is an essential chemical reaction. Esters are one of the

14

main classes of chemicals and have many applications in various fields such as plasticizers,

15

solvents, intermediates, and in pharmaceuticals industries. Esters are colorless, pleasant

16

aroma that is responsible for the fragrance of fruits and flowers and volatile liquids. Because

17

of the broad applications of esters in the chemical and allied fields, more than 500

18

commercial esters exists. Esters are synthesized from simple hydrocarbons, and the chemical

19

structure is R-COOR’. The general method for the preparation of esters is heating of

20

carboxylic acid with alcohol; removing water from the reaction mixture

21

reaction for esterification is as given below:

1-4.

The general

22

2 ACS Paragon Plus Environment

Page 3 of 33 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Industrial & Engineering Chemistry Research

1

Typically esterification reaction is prolonged and shows limited conversion; in the absence of

2

a catalyst, it requires many days to reach the equilibrium. For accelerating the higher

3

conversion or reaction rate, acid catalysts are always used as a proton donor in liquid phase

4

esterification 5,6. Due to the presence of by–product water, esterification reaction is extremely

5

reversible and show second-order reactions kinetics. Presence of water (by-product) in the

6

esterification reaction reduces the conversion of acid because of the hydrolysis reaction of the

7

ester to acid and alcohol as it is a readily reversible reaction. This problem is surmounted by

8

continuous removal of by-product water through distillation, using dean stark methods, using

9

a molecular sieve to absorb water or any advance separation technique such as reactive 3,7.

10

distillation

The primary challenge with esterification reaction in the absence of a catalyst

11

is that it requires several days to acquire equilibrium due to the reversibility and low reaction

12

rate, showing the limited equilibrium conversion of acid. Therefore, in the esterification rate

13

of reaction is enhanced by using a catalyst. Heterogeneous and homogeneous acids play the

14

role of the catalyst which protonate the oxy group of carboxylic acid and is the rate-

15

determining step in the esterification reaction mechanism.[5,8] A homogeneous catalyst for

16

example acid catalyst that acts as a proton donor and is used to enhance esterification

17

reaction. Mineral acid for example H2SO4, HI, and HCl and an organic acid such as p-

18

Toluene sulfonic acid are commonly employed as homogeneous catalyst. The varying

19

reaction conditions, such as the elevated temperatures, increase in the mole ratio of alcohol to

20

acid and employing of more active catalyst enhance the reaction rate in the presence of a

21

catalyst 6,8.

22

Mineral acid catalyst has many drawbacks such as being corrosive in nature and difficult to

23

separate yet they are of low cost, high solubility gives high conversion and is having a high

24

density of acid sites making it preferable over heterogeneous catalysts 2. Sulphuric acid is

25

commonly used as a homogeneous catalyst in the esterification reaction of acid and alcohol

3 ACS Paragon Plus Environment

Industrial & Engineering Chemistry Research 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 4 of 33

1

because of its strong acid strength and robust dehydrated nature. The acid strength of a

2

mineral acid is responsible for the protonation of the acid. In the literature, a comparative

3

study of heterogeneous and homogeneous catalyzed esterification reaction has been done.

4

The present study reports higher conversion of series of aliphatic acids to esters using

5

sulphuric acid as a homogeneous catalyst and is compared the activation energy with

6

heterogeneous catalyzed reaction reported in the litrature. In general, due to the presence of

7

free protons, reaction mixture using homogeneous catalysts (liquid-liquid phase) results in

8

faster reaction rates as compared to heterogeneous (liquid-solid reaction mixture) catalyst 8.

9

The objective of the current work is to examine the esterification of series of aliphatic acid

10

(C1-C5) with three different alcohols, n-propanol, isopropanol, and n –butanol using

11

sulphuric acid as a catalyst.

12

The manuscript reports first of its kind study of esterification of series of a carboxylic acid

13

(formic, acetic, propionic, butyric and pentanoic acid) with different alcohols (n-propanol,

14

isopropanol and n-butanol respectively) using sulphuric acid as a homogeneous catalyst. The

15

present study also elaborate the structural effects and the reactivity of carboxylic acids and

16

effect of length and branching of alcohols for homogeneously catalyzed esterification

17

reaction of series of a carboxylic acids. The earlier literature has reported limited work on

18

esterification of series of such a carboxylic acids with various alcohols using a heterogeneous

19

and homogeneous catalyst. In the earlier literature, the esterification of acrylic, acetic,

20

propionic and butyric acid but not with formic and pentanoic acid, with methanol, ethanol,

21

and propanol were studied using hydrogen chloride and hydrogen iodide as a catalyst but not

22

sulphuric acid 5. Also, the past litrature reported esterification of such a series of carboxylic

23

acids with methanol, ethanol and propanol but not with n-propanol, isopropanol and n-

24

butanol under identical experimental conditions

25

carboxylic acids (acetic, propionic, butyric, hexanoic and caprylic acids) with methanol

5,9.

The impact of chain length of various

4 ACS Paragon Plus Environment

Page 5 of 33 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Industrial & Engineering Chemistry Research

1

employing sulphuric acid and SAC-13 ( a Nafion/silica nanocomposite ) as a catalyst has

2

been investigated and reported but not with formic and pentanoic acid9. The present work

3

endeavored to examine the esterification of formic, acetic, propionic, butyric and pentanoic

4

acid with propanol, isopropanol, and n –butanol respectively using sulphuric acid as a

5

homogeneous catalyst in the batch reactor. In the present research, a series of esterification

6

reaction of variable length of carboxylic acid have been conducted to find out the effect of

7

various reaction parameters, viz. reaction temperature, the mole ratio of reactants (acid :

8

alcohol) and the catalyst loading. Moreover, the latter part of this paper also presents the

9

kinetic modelling of the esterification reaction and reactivity of carboxylic acids and alcohol

10

under the optimized reaction conditions.

11

The literature is, limited to only a couple of studies found which elaborate the structural

12

effects and the reactivity of carboxylic acids for homogeneously catalyzed esterification

13

reaction

14

and chemical structure for various length alkyl chain carboxylic acids and their bulkier and

15

larger counterparts using a homogeneous catalyst (sulphuric acid) with propanol, isopropanol,

16

and n –butanol respectively.

17

2. Experiments:

18

2.1. Materials:

19

Propanol, isopropanol, and n –butanol analytical grade with purity of 99.5% were purchased

20

from HiMedia Lab. Pvt. Ltd (Mumbai, India).The homogeneous catalyst, sulphuric acid with

21

a purity of 99% and specific gravity of 1.853g/c.c., molecular seive were supplied by Thomas

22

Bakers, Mumbai, India. Formic acid, acetic acid, propionic, butyric acid and pentanoic were

23

supplied by SDFCL Mumbai, India. All the reagents used in the experiments were of

24

analytical grade.

5,9.

In contrast, the present study reveals the correlation between chemical reactivity

25 5 ACS Paragon Plus Environment

Industrial & Engineering Chemistry Research 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 6 of 33

1

2.2. Methods:

2

Experiments were conducted in a three neck round bottom flask batch reactor of a capacity of

3

250 ml with a magnetic stirrer. A reflux condenser was equipped at the top of the reactor to

4

stop the escape of volatile compounds.

5

and respective alcohol followed by the addition of sulphuric acid as a catalyst. The required

6

amount of reagents was calculated by mole ratio for each reaction. The stirring rate of

7

magnetic stirrer was kept constant at 650 rpm throughout the experiments. The effects of the

8

catalyst (H2SO4) loading to the percentage weight of acids, the mole ratio of acids to alcohols

9

and the variation of temperature were studied for all acid- alcohol combination. The length of

10

carbon chain is different and their miscibility in alcohols and boiling points are different for a

11

series of an acid. Therefore, to get the maximum conversion of acids to esters different

12

temperature ranges were studied. The by-product, water was adsorbed by means of a

13

molecular sieve. A Type 3A molecular sieve was used to adsorb by-product, water molecule

14

from the reaction mixture. Molecular sieves are usually zeolite compounds that strongly

15

adsorb water molecules as they have carefully controlled pore sizes. While both water and the

16

solvent will adsorb strongly to the surface of molecular sieve, but the pores present on large

17

surface area of molecular sieve is only accessible to the smaller molecules like water, and

18

they are effectively adsorbed and removed from the reaction mixture among the solvent

19

either in a vapour or liquid form. The aliquots were pipetted out at regular time intervals of

20

30 minutes and were monitored by gas chromatographic analysis.

21

For analysis of acids and esters gas chromatography (Chemito, GC 8610) was used using

22

hexane as an internal standard. The analyzing conditions for gas chromatograph analysis

23

were as follows: a flame ionisation detector (FID), a stainless steel column (packed column)

24

with the stationary phase of 3% SP-2310 and 2% SP-2300 matrix 100/120 Chromosorb solid

The reactor was charged with the carboxylic acid

6 ACS Paragon Plus Environment

Page 7 of 33 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Industrial & Engineering Chemistry Research

1

support. The detector temperature was 230°C; injection temperature was 210°C with nitrogen

2

as a carrier gas.

3

3. Results and discussion:

4

The probable reaction parameters which affect the rate of esterification reaction to increase

5

the conversion of acids to esters were studied in detail. The variables were reaction

6

temperature, catalyst loading, and reactants (acid: alcohol) mole ratio. The experiments were

7

performed by changing various process parameters. The activation energy, frequency factor,

8

and coefficient of variance were calculated at various temperatures for series of a carboxylic

9

acid (C1-C5) with n-propanol, isopropanol, and n-butanol respectively.

10

3.1. Effect of mole ratio:

11

Esterification reaction of acid with alcohol is equilibrium – limited, reversible reaction and

12

the conversion of acid can be enhanced by removing, by-product water or using an excess of

13

either of the reagents 8. In the present study, the effects of mole ratio of acids to alcohols were

14

investigated. Four different mole ratios of alcohols to acids were studied to find out the effect

15

of initial mole ratio on maximum conversion of series of aliphatic acids while other

16

parameters such as reaction temperature and catalyst loading were kept constant. Increasing

17

the mole ratio of respective acid to alcohol increases the conversion of acids.

18

esterification of acetic acid with n-propanol, isopropanol and n-butanol using H2SO4 as a

19

catalyst increases the conversion of acid from 62.2 ± 0.06 % to 95.2 ± 0.17 %, 58.8 ± 0.04 %

20

to 92.6 ± 0.17 % and 60.07 ± 0.05 % to 93.7 ± 0.17 % respectively with increasing the mole

21

ratio from 1:1to 1:4 (acid: alcohol) shown in fig.1a-1c over a similar time interval (240

22

minute). Similarly, conversion of formic, propionic, butyric and pentanoic acids increased

23

with an increasing the mole ratio of acid to alcohol from 1:1 to 1:3, 1:4, 1:4 and 1:6

24

respectively as shown in fig. 2 a-2d. However, it was found that for esterification of formic

25

acid, the conversion of formic acid at a mole ratio of 1:4 is slightly lower than 1:3 (96 ± 0.18

The

7 ACS Paragon Plus Environment

Industrial & Engineering Chemistry Research 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 8 of 33

1

% to 95.2 ± 0.18 %, 93.5 ± 0.15 % to 92.6 ± 0.15 % and 94.1 ± 0.18 % to 93.2 ± 0.15 %)

2

with n-propanol, isopropanol, and n-butanol respectively. For acetic acid the conversion of

3

acids is slightly higher from 1:3 to 1:4 mole ratio( 91.4 ± 0.11 % to 95.2 ± 0.17 %, 91.2 ±

4

0.17 % to 92.6 ± 0.17 % and 92.9 ± 0.17 % to 93.7 ± 0.17 % with n-propanol, isopropanol

5

and n-butanol respectively) as shown in fig.1a-1c..The reason could be the dilution of

6

alcohols concentration at higher mole ratio. Therefore, a decrease in conversion or slightly

7

increase in conversion were obtained for high mole ratio 3.

8

Increase in the mole ratio of acids to alcohols for propionic acid, butyric acid, and pentanoic

9

acid (1:1 to 1:4 and 1:6) leads to a significantly enhance the conversion of respective acid.

10

The results obtained for the effect of mole ratio on the carbon chain length of a carboxylic

11

acid to n-propanol, isopropanol and n-butanol respectively specified that with the use of an

12

excess of alcohol, the equilibrium conversion of respective acid can be efficiently enhanced.

13

The results are illustrated in the Supporting Information (Table S1). From fig.1a-1c and 2a-2d

14

it can be concluded that the initial mole ratio of acids to alcohols has significant impact on

15

the equilibrium conversion of respective acid, which notably increases with using excess

16

alcohols and equilibrium conversions shifted towards the desired product. Further increase in

17

the moles of alcohols has a little effect on the reaction rate; it only causes to attain the state of

18

equilibrium in the somewhat shorter period 1,8. The maximum percentage conversion of series

19

of carboxylic acids (C1-C5) with n-propanol, isopropanol and n-butanol respectively, were

20

optimised and reported in the Supporting Information (Table S1).

21

3.2. Effect of concentration s of catalyst:

22

The amount of catalyst loading is the most important parameter to increase the equilibrium

23

conversion of acid and the rate of the reaction because catalyst provides an alternative path

24

by lowering the activation energy of the reaction and giving out the desired product. Hence, it

25

consequently increases the reaction rate and higher conversion

1,8.

To evaluate the effect on 8

ACS Paragon Plus Environment

Page 9 of 33 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Industrial & Engineering Chemistry Research

1

the amount of catalyst, experiments were performed by varying the catalyst concentration

2

based on the weight of the acids from 0.5% to 7% w/w keeping the temperature and mole

3

ratio of acids to alcohols constant. It was found that the conversion of a variable length of

4

carbon chain of a carboxylic acid with n-propanol, isopropanol, and n-butanol respectively

5

are efficiently increased with increasing the catalyst loading as shown in the fig. 3a-3c for

6

esterification of acetic acid. The higher conversion of acids with a high concentration of

7

catalyst is due to the presence of more H+ ions which eventually enhances the rate of reaction

8

8.

9

increased and attain equilibrium conversion. From fig. 3a-3c and 4a it is indicated that further

10

increase in the amount of catalyst from 3% to 5% the conversion of formic acids decreases

11

from 96.0 ± 0.18 % to 94.7 ± 0.18 % , 93.5 ± 0.15 % to 92.2 ± 0.15 % and 94.1 ± 0.18 % to

12

93.2 ± 0.15 %. And for acetic acid conversion decreases from 95.2 ± 0.17 % to 94.3 ± 0.18

13

%, 92.6 ± 0.17% to 91.7 ± 0.17 % and 93.7 ± 0.17 % to 93 ± 0.17 % with n propanol,

14

isopropanol and n-butanol respectively. The equilibrium conversion of formic and acetic acid

15

reduces when the amount of catalyst concentration increases from 3 to 5% by weight of acids.

16

This might be due to the dehydration of alcohols in the presence of excess of acid catalyst

17

resulting in the alkene formation (n-propene, isopropene and n-butene) as shown in scheme1

18

10.

Esterification of formic, acetic, propionic, butyric and pentanoic acids were significantly

19 20

Scheme1. Dehydration of alcohol in the presence of excess acid catalyst

21 9 ACS Paragon Plus Environment

Industrial & Engineering Chemistry Research 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 10 of 33

1

Fig. 4b-4d depicted the conversion of propionic,butyric and pentanoic acids increased with

2

increasing the catalyst amount from 0.5 % to 5 % and 1 % to 7 % respectively. In fig. 3a-3c

3

the graph shows the effect of catalyst loading on the esterification reaction of acetic acid acid

4

with n-propanol, isopropanol, and n-butanol respectively. It can be concluded that the rate of

5

equilibrium conversion of respective acid increases with an increasing in the catalyst

6

concentration. This is because increase in the number of H+ ions in the reaction mixture and

7

hence more active free protons are available which is proportional to the used catalyst

8

concentration 7. Thus in the presence of more H+ ions a higher number of carbonyl carbon of

9

acids are activated, and nucleophilic attack by alcohols become more favourable resulting in 11.

10

desired products

Fig. 3a-3c and 4a-4d reveals that the catalyst concentrations of 3% for

11

formic and acetic acids, 5% for propionic acid and 7% for butyric and pentanoic acids by

12

weight of the acids resulted in a relatively higher conversion. It is because of the 3%-7%

13

catalyst concentration by weight of acids are the maximum amount of catalyst required to

14

activate the carbonyl carbon of various chain length of carboxylic acids

15

amount of 3 %, 5 % and 7% catalyst concentrations by weight of the acids are considered as

16

more efficient for the esterification system of various carboxylic acids involving n-propanol,

17

isopropanol, and n-butanol respectively.

18

3.3 Effect of Temperature:

19

The effect of reaction temperature on the rate of reaction is extremely imperative as this

20

information helps in calculating the rate constant of the reaction and the activation energy.

21

Hence the rate constant, activation energy and frequency factor are functions of temperature.

22

The conversion and rate of reaction enhances with increasing the temperature are due to the

23

more successful collision which has sufficient energy to break the bonds resulting in the

24

product 7,8.

12.

Therefore the

10 ACS Paragon Plus Environment

Page 11 of 33 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Industrial & Engineering Chemistry Research

1

Esterification reactions are conducted at various temperatures to examine the effect of

2

temperature on the reaction rate while keeping other parameters constant. The reaction was

3

conducted with four different temperatures for fix mole ratio of respective acid to alcohol and

4

catalyst concentration. Fig. 5a-5c showed the esterification of acetic acid. The effect of

5

temperature on the esterification of acetic acid was investigated over a temperature range of

6

323.15 K to 353.15 K at 1: 4 mole ratio of acid to alcohols (acetic acid: n-propanol,

7

isopropanol, and n-butanol) and catalyst concentration(H2SO4) of 3% w/v to acid (240

8

minute). Similarly, esterification of formic, propionic and butyric acids with n-propanol,

9

isopropanol and n-butanol were investigated at different temperature region with molar ratio

10

of 1:3 and 1:4 (acids: alcohols ) , catalyst loading of 3%, 5% and 7 % w/v of acid (300

11

minute) . Esterification of pentanoic acid with n-propanol, isopropanol and n-butanol were

12

carried out over 7% w/v of the catalyst over a temperature range of 363.15 K to 383.15 K

13

with a mole ratio of 1:6 (acids: alcohols) over fix time period (300 minute) to get the

14

maximum equilibrium conversion. Results are shown in fig. 5a-5c indicate that the

15

conversion of acids and rate of reactions are sensitive to the change in the reaction

16

temperature. Also, the change in the temperature affects the kinetics and thermodynamics of

17

the reaction. In order to find out the scope of the present work the esterification of other

18

carboxylic acids (formic, propionic, butyric and pentanoic acid) were examined. The detailed

19

graphs (S1a-S1d) are included in the Supporting Information file in the revised manuscript.

20

3.4. Evaluation of kinetic parameter:

21

The kinetic model of the esterification reaction between acid and alcohol to produce ester and

22

water is reversible and elementary second order reaction; first order with respect to each

23

reactant. To develop a kinetic model esterification reaction is expressed as:

24 25

𝐴 +

𝐵

⇋

𝐸 +

𝑊

(2) 11

ACS Paragon Plus Environment

Industrial & Engineering Chemistry Research 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

1

Where 𝐴 = Acid,

𝐶𝐴 = concentration of acid

2

𝐵 = Alcohol, 𝐶𝐵 = concentration of alcohols

3

𝐸 = Ester,

4

𝑊 = Water, 𝐶𝑊 = concentration of water

5

Page 12 of 33

𝐶𝐸 = concentration of esters

At stoichiometric condition rate of equation can be formulated as:

6 7

― 𝑟𝐴 = 𝑘1 𝐶𝐴𝐶𝐵 ― 𝑘2 𝐶𝐸𝐶𝑊

(3)

8 9

However, in the present work, the excess of alcohols was used and the water was adsorbed by

10

means of molecular sieve from the reaction mixture during the reaction, hence reverse

11

reaction could be neglected and it was considered that the reaction equilibrium did not hinder

12

the completion of the reaction. Furthermore, the excess of alcohol was used in the reaction,

13

therefore, its concentration could be assumed to remain constant during the reaction time.

14

Therefore the pseudo-homogeneous first-order kinetic model was proposed as the reaction

15

mechanism and is expressed by the following equation: 𝑘 𝑡 = ― ln (1 ― 𝑋𝐴)

16

(4)

17 18

In fig. 6a., 6c. and 6d. the graph was plotted between ― ln (1 ― 𝑋𝐴) versus time in minute to

19

find out the rate constant. The kinetic data obtained fitted well for a proposed kinetic model

20

(pseudo homogeneous first order) and was appropriate with high regression coefficients

21

(Table 1).

22 23

3.5. Apparent Activation Energy Measurement

12 ACS Paragon Plus Environment

Page 13 of 33 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Industrial & Engineering Chemistry Research

1

The reaction rate constant was obtained using linear regression method using the equilibrium

2

equation and integrated rate equation ( graph between ― ln (1 ― 𝑋𝐴) versus time). It was

3

utilized to find out the value of rate constant, activation energy (Ea) and frequency factor (A),

4

expressed by Arhhenius equation. To find out the value of frequency factor and activation

5

energy, a graph is plotted between lnk verses 1/T as shown in fig 6b., 6d. and 6f. 1,3,11. It was

6

found that the activation energy for the esterification of acetic acid with n-propanol,

7

isopropanol, and n-butanol are 36.27, 33.51 and 34.69 kJ/mole respectively, which was quite

8

comparable to reported in the literature.[13-17] For propionic acid the, activation energy were

9

found 36.34, 35.33 and 35.93, for butyric acid the value of activation energy were found

10

35.59, 36.12 and 34.79 kJ/mole respectively and was comparable to those reported in the

11

previous literature 4,18-20. In spite of relatively similar results the, mole ratio of respective acid

12

to alcohol, catalyst loading and temperature in our experiments were different than those

13

described in the literature. ― 𝐸𝐴

14

𝑘 = 𝑘0 exp (

15

ln [𝑘] = ln [𝑘0] ― 𝑅𝑇

𝑅𝑇

(5)

) 𝐸𝐴

(6)

16

The activation energy, frequency factor and coefficient of regression for a series of a

17

carboxylic acid with n-propanol, isopropanol, and n-butanol respectively are summarised

18

(Table 1) . The linear plot between ― ln (1 ― 𝑋𝐴) versus time for the esterification of formic,

19

propionic, butyric and pentanoic acid with n-propanol, isopropanol and n-butanol are

20

reported in the Supporting Information (S2a-S2c, S3a-S3c, S4a-S4c and S5a-S5c). And detail

21

of graph plotted between lnk verses 1/T for the esterification of formic, propionic, butyric and

22

pentanoic acid with n-propanol, isopropanol and n-butanol are in the Supporting Information

23

(S6a-S6c, S7a-S7c, S8a-S8c and S9a-S9c).

13 ACS Paragon Plus Environment

Industrial & Engineering Chemistry Research 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 14 of 33

1 2 3

Table 1. Value of activation energies, frequency factor, coefficient of determinates and

4

TOF for esterification of various carboxylic acids with n-butanol, isopropanol and n-

5

butanol respectvely. Sr.N.

Esters O

1 H

Frequency Factor (min.-1) 1822

R2

TOF (h-1)

0.957

22.86

33.13

1680

0.998

22.26

34.11

2456

0.998

22.38

36.27

2869

0.991

12.93

33.51

982

0.995

12.58

34.69

1559

0.995

12.73

36.34

1927

0.978

6.26

35.33

1276

0.996

6.06

35.93

1632

0.996

6.14

35.59

795

0.993

2.94

36.12

936

0.989

2.89

34.79

584

0.989

2.92

37.36

1003

0.989

2.53

36.98

873

0.992

2.52

O

3a

O

2 H

O

3b

O

3 H

4

Activation energy (kj/mol) 33.02

O

3c

O

O

5

3d

O

O

6

3e

O

O

3f 7 8

O

O

O

3g O

3h 9

O

O

3i 10

O

O

3j 11

O

O

3k 12

O

O

3l 13

O

O

3m 14

O

O

3n 14 ACS Paragon Plus Environment

Page 15 of 33 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Industrial & Engineering Chemistry Research

15

O

O

35.07

459

0.989

2.47

3o 1 2

3.6. Reactivity of carboxylic acids:

3

The impact of chain length of various carboxylic acids (formic, acetic, propionic, butyric and

4

pentanoic acid) on the esterification reaction with n-propanol, isopropanol, and n-butanol

5

respectively at optimal reaction conditions were studied. Fig 7a-7c, shows the effect of

6

various chain length of carboxylic acids on the esterification reaction with n-propanol,

7

isopropanol, and n-butanol respectively at 343.15 K for formic, acetic, propionic, butyric, and

8

pentanoic acids, the mole ratio of 1:3 and catalyst loading 3% for fix time (180 minute). The

9

conversion of acids decreases from 96 ± 0.18 % to 33.9 ± 0.11%, 93.5 ± 0.15 % to 31.2 ±

10

0.12 % and 94.1 ± 0.18 % to 31.5 ± 0.12 % as the increases in the chain length of carboxylic

11

acids for n-propanol, isopropanol, and n-butanol respectively as shown in fig. 7a-7c. Table 1 ,

12

reveal the reactivity difference in term of turn over frequency (TOF) of the series of

13

carboxylic acids with n-propanol, isopropanol, and n-butanol respectively using sulphuric

14

acid as catalyst at optimized reaction condition for all experiments

15

the reactivity of the carboxylic acid decreases with increasing the alkyl chain length for each

16

addition of each CH2 moiety. Two factors namely steric hindrance and an inductive effect

17

contribute to the diminishing reactivity of carboxylic acids. With the lengthening of the alkyl

18

chain of the acids, the electrophilicity of the carboxylic group decreases due to the inductive

19

effect. Hence in the rate controlling step, the nucleophilic attack on carbonyl carbon become

20

more energy hindered 9.

21

The decisive factor is responsible for the steric component which affects the reactivity of the

22

carboxylic acid in acid catalyzed esterification. With an increase in molecular size, the steric

23

hindrance increases which results in electronic repulsion in reactant molecules between non

5,9.

It was evaluated that

15 ACS Paragon Plus Environment

Industrial & Engineering Chemistry Research 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 16 of 33

1

bonded atoms. Due to this repulsive steric hindrance, in the intermolecular region the electron

2

density diminishes and affects the molecule bonding interaction. Thus the steric effect

3

increases with an alkyl chain of carboxylic acids. Since the steric effects are governed by

4

molecular size and

5

homogeneously catalyzed esterification reactions higher carboxylic acid may assume a

6

conformation which minimizes the contribution of steric hindrance. Because of the free acid

7

sites present in reaction mixture in the homogeneously catalyzed esterification reaction, the

8

steric hindrance is less important as compared to a heterogeneous catalyst which has fixed

9

acid sites 5,9.

preferential conformations called conformational leveling effect. In

10

The steric effect caused by the alpha substituents in the carbon atom of aliphatic system was

11

quantitatively calculated by using Taft equation, the correlation shown below in equation

12

(12).

13

14

log

𝑟

(𝑟 𝑟 ) 0

= 𝛿 𝐸𝑠

(12)

15

Where

16

acid bearing a methyl group, 𝐸𝑠 is the steric hindrance and 𝛿 is the susceptibility

17

measurement of steric effect of substituents for a particular reaction series. Further Taft

18

correlation was improved by Chatron and 𝐸𝑠 constant was replaced by vander waals radii 𝑣

19

for a given substituents 9. The proposed Charton correlation is shown in equation 13.

20

𝑟0 represents the rate constant of an acid having a given alpha substituent versus

log 𝑟 = 𝜑𝑣 + ℎ

(13)

21

Where 𝜑 and ℎ are constants. The values of 𝑣 for homogeneous catalysed esterification

22

reaction have been determined in literature 21. In fig. 8a-8c, graph plotted between log TOF 16 ACS Paragon Plus Environment

Page 17 of 33 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Industrial & Engineering Chemistry Research

1

vs 𝑣 suggests that the steric effect is dominate for catalytic activity in homogeneous catalysed

2

esterification reaction.

3

In fig. 8a-8c, graph is plotted between log (TOF) vs 𝑣, for acetic, propionic, butyric and

4

pentanoic acid with n-propanol, isopropanol and n-butanol respectively. Results indicated

5

that the reactivity of acids depends on stearic hindrance of acids. As carbon chain length of

6

acids increases stearic hindrance also increases and the reactivity of acids decreases as shown

7

in fig. 8a-8c. However the reactivity of formic acid is independent of stearic hindrance as it is

8

not mention in graph, but value of TOF for formic acid listed in Table1. At same point fig.8

9

(a-c) and are seem to be identical for the esterification of series of acids with n-propanol,

10

isopropanol and n-butanol respectively. Fig. 8 (a-c) reveals that the reactivity of series of

11

acids with different alcohols only marginally depends on the physical property i.e. solubility

12

and boiling of different alcohols (n-propanol, isopropanol and n-butanol respectively) instead

13

of chemical property (steric hindrance and inductive effect) at the same temperature. Hence

14

the curves (a–c) in Figure 8 seems be identical for esterification of series of acids with all

15

alcohols (n-propanol, isopropanol and n-butanol respectively) are seem to be identical 22.

16

3.7. Reactivity of alcohols:

17

The impact of chain length and branching of various alcohols (n-propanol, isopropanol, and

18

n-butanol) were studied by conducting multiple experiments with formic, acetic, propionic,

19

butyric and pentanoic acids using sulphuric acid as a catalyst. Fig. 9 reveals that the

20

conversion of acetic acids with increasing chain length and branching of alcohols. The

21

equilibrium conversion of acetic acid after fix time (240 minute) was observed to be 95.2 ±

22

0.17%, 92.6 ± 0.17 % and 93.7 ± 0.17% with n-propanol, isopropanol, and n-butanol

23

respectively. From fig. 9, it can be concluded that, for a given catalyst the conversion of

24

acetic acids are highest for n-propanol, n –butanol and isopropanol respectively. Similarly for 17 ACS Paragon Plus Environment

Industrial & Engineering Chemistry Research 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 18 of 33

1

formic, propionic and butyric acid the order of reactivity of alcohol is n-propanol, n –butanol

2

and isopropanol respectively. The order of reactivity of alcohol is n-propanol, isopropanol

3

and n-butanol respectively for pentanoic acid. Due to steric hindrance, both long chain and

4

branching cause the decreases in the acids conversion.

5

4. Conclusions:

6

Based on the results obtained from the experiments the kinetics of homogeneously catalyzed

7

esterification of different carbon chain length of aliphatic carboxylic acids with n-propanol,

8

isopropanol, and n-butanol were evaluated. The resultant kinetics data were well correlated

9

with pseudo homogeneous first order reaction for all the experiments. The conversion of

10

acids and rate constant were found to increase with increasing the temperature, initial

11

respective acid: alcohol mole ratio and the catalyst loading. For different carboxylic acids

12

conversions obtained were the highest for formic acid followed by acetic, propionic, butyric

13

and pentanoic acid respectively. Among the alcohols the order of reactivity was found to be

14

n-propanol > n-butanol> isopropanol for the esterification of formic, acetic, propionic and

15

butyric acids. For the esterification of pentanoic acid order of reactivity of alcohols were n-

16

propanol > isopropanol > n-butanol. To achieve 100 % conversion one has to make use of an

17

in situ separation technique such as reactive distillation.

18

Acknowledgement:

19

We gratefully acknowledge the University Grant Commission (F.5-64/2007 BSR), New

20

Delhi, India for financially supporting the research work.

21

Supporting Information:

22

The detail plot for effect of temperature on esterification of formic, acetic, propionic, butyric

23

and pentanoic acids are shown in fig. S1a-S1d. And linear plot between ― ln (1 ― 𝑋𝐴) versus 18 ACS Paragon Plus Environment

Page 19 of 33 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Industrial & Engineering Chemistry Research

1

time and lnk verses 1/T for esterification of formic, acetic, propionic, butyric and pentanoic

2

acids are shown in fig. (S2a-S2c, S3a-S3c, S4a-S4c and S5a-S5c ) and (S6a-S6c, S7a-S7c,

3

S8a-S8c and S9a-S9c).

4

References:

5

[1] Mittal, A.; Nair, S.; Deshmukh, K. The Kinetic Comparison Study of Catalytic

6

Esterification of Butyric Acid and Ethanol over Amberlyst 15 and Indion-190 Resins.

7

IJIRSET 2015, 5860–5867.

8

[2]

9

Homogeneous Acid Catalyst. Indian Chem. Eng. 2015, 57 (2), 177–196.

Beula, C.; Sai, P. S. T. Kinetics of Esterification of Acetic Acid and Ethanol with a

10

[3]

Zeki, N. S. A.; Al-Hassani, M. H.; Al-Jendeel, H. A. Kinetic Study of Esterification

11

Reaction. Al-Khwarizmi Eng. J. 2010, 6 (2), 33–42.

12

[4]

13

Development of the Rate Expression for the Dowex 50 Wx8-400 Catalyzed Esterification of

14

Propionic Acid with 1-Propanol. Chem. Eng. Sci. 2007, 62 (12), 3197–3217.

15

[5] Keshav, A.; Joshi, N. Experimental Study of Esterification of Carboxylic Acid with

16

Different Alcohol Using Various Catalysts. IJSEM 2018, 3 (1), 27–29.

17

[6] Lilja, J.; Wärnå, J.; Salmi, T.; Pettersson, L. J.; Ahlkvist, J.; Grénman, H.; Rönnholm,

18

M.; Murzin, D. Y. Esterification of Propanoic Acid with Ethanol, 1-Propanol and Butanol

19

over a Heterogeneous Fiber Catalyst. Chem. Eng. J. 2005, 115 (1–2), 1–12.

20

[7]

21

2-Methyl-4-Chlorophenoxyacetic Acid (MCPA Acid). Int. J. Chem. React. Eng. 2011, 9 (1).

Ali, S. H.; Tarakmah, A.; Merchant, S. Q.; Al-Sahhaf, T. Synthesis of Esters:

Kong, P. S.; Aroua, M. K.; Raman, A. A. Kinetics Study of Esterification Reaction of

19 ACS Paragon Plus Environment

Industrial & Engineering Chemistry Research 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 20 of 33

1

[8] Jyoti, G.; Keshav, A.; Anandkumar, J. Experimental and Kinetic Study of Esterification

2

of Acrylic Acid with Ethanol Using Homogeneous Catalyst. Int. J. Chem. React. Eng. 2016,

3

14 (2), 571–578.

4

[9]

5

carboxylic acids with methanol using acid catalysis, J. Catal. 2006(243)221-228.

6

[10] Altman, E.; Stefanidis, G. D.; Van Gerven, T.; Stankiewicz, A. Microwave-Promoted

7

Synthesis of n-Propyl Propionate Using Homogeneous Zinc Triflate Catalyst. Ind. Eng.

8

Chem. Res. 2012, 51 (4), 1612–1619.

9

[11] Kusumaningtyas, R. D.; Ratrianti, N.; Purnamasari, I.; Budiman, A. Kinetics Study of

10

Jatropha Oil Esterification with Ethanol in the Presence of Tin (II) Chloride Catalyst for

11

Biodiesel Production. AIP Conference Proceedings 2017, 1788 (Ii).

12

[12] Cardoso, A. L.; Neves, S. C. G.; da Silva, M. J. Esterification of Oleic Acid for

13

Biodiesel Production Catalyzed by SnCl2: A Kinetic Investigation. Energies 2008, 1 (2), 79–

14

92.

15

[13] Mali, V. V.; Deosarkar, M. P. Esterification of Acetic Acid With Butanol in the

16

Presence of Solid Acid Catalyst. International Journal of Advances in Science Engineering

17

and Technology 2016, 4 (2), 245–248.

18

[14] Gurav, H. R.; Nandiwale, K. Y.; Bokade, V. V. Pseudo-Homogeneous Kinetic Model

19

for Esterification of Acetic Acid with Propanol Isomers over Dodecatungstophosphoric Acid

20

Supported on Montmorillonite K10; 2014; Vol. 27.

21

[15] Tao, D.; Wu, Y.; Zhou, Z.; Geng, J.; Hu, X.; Zhang, Z. Kinetics for the Esterification

22

Reaction of n -Butanol with Acetic Acid Catalyzed by Noncorrosive Brønsted Acidic Ionic

23

Liquids. 2011, 1989–1996.

Lotero, Y. Liu, E.; Goodwin, J.G. Jr. effect of carbon chain length on esterification of

20 ACS Paragon Plus Environment

Page 21 of 33 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Industrial & Engineering Chemistry Research

1

[16] Li, W.; Liu, W.; Xing, W.; Xu, N. Esterification of Acetic Acid and n - Propanol with

2

Vapor Permeation Using NaA Zeolite Membrane. 2013.

3

[17] Balasubramanian, K.; Kuriacose, J.C.; Kinetic of Reaction of Acetic acid and 2-

4

Propanol Catalyzed by Zinc Chromium Ferrite Spinel. J. Res. Inst. Cata. Hokkaido Univ.

5

(1983 (1), 53-60.

6

[18] Lee, M.-J.; Chiu, J.-Y.; Lin, H. Kinetics of Catalytic Esterification of Propionic Acid

7

and n -Butanol over Amberlyst 35. Ind. Eng. Chem. Res. 2002, 41 (12), 2882–2887.

8

[19]

9

of Mixed Ethanol/ n -Butanol Esterification of Butyric Acid with Amberlyst 70 and p -

Santhanakrishnan, A.; Shannon, A.; Peereboom, L.; Lira, C. T.; Miller, D. J. Kinetics

10

Toluene Sulfonic Acid. Ind. Eng. Chem. Res.2013, 52 (5), 1845–1853.

11

[20]

12

Catalytic Esterification of Butyric Acid and N-Butanol over Dowex 50Wx8-400. Chem. Eng.

13

J.l 2011, 168 (1), 293–302.

14

[21] Charton, M. Steric Effects. 7. Additional V Constants. J. Org. Chem. 1976, 41 (12),

15

2217–2220.

16

[22] Kastratovic V. , Bigovic M., Esterification of Stearic Acid with lower Monohydroxylic

17

Alcohols. 2017.

Ju, I. B.; Lim, H. W.; Jeon, W.; Suh, D. J.; Park, M. J.; Suh, Y. W. Kinetic Study of

18 19 20 21

21 ACS Paragon Plus Environment

Industrial & Engineering Chemistry Research 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 22 of 33

1 2 3

List of Figures:

4

[1] Fig.1a.-1c. Effect of different initial mole ratio on esterification of acetic acid with n-

5

propanol, isopropanol and n-butanol respectively, at 353.15 K and 3% catalyst loading.

6

[2] Fig.2a.-2d. Effect of initial mole ratio on esterification of (a) formic acid at 343.15 K

7

and 3% catalyst loading, (b) propionic acid at 363.15 K and 5% catalyst loading, (c)

8

butyric acid at 373.15 K and 7% catalyst loading and (d) pentanoic acid at 383.15 K and

9

7% catalyst loading with n-propanol, isopropanol and n-butanol respectively.

10

[3] Fig. 3a.-3c. Effect of catalyst loading on esterification of acetic acid with n-propanol,

11

isopropanol and n-butanol respectively at 353.15 K and 1:4 mole ratio.

12

[4] Fig.4a.-4d. Effect of catalyst loading on esterification of (a) formic acid at 343.15 K

13

and 1:3 mole ratio of acid to alcohol, (b) propionic acid at 363.15 K and 1:4 mole ratio

14

of acid to alcohol, (c) butyric acid at 373.15 K and 1:4 mole ratio of acid to alcohol and

15

(d) pentanoic acid at 383.15 K and 1:6 mole ratio of acid to alcohol with with n-

16

propanol, isopropanol and n-butanol respectively.

17

[5] Fig.5a.-5c. Effect of temperature on esterification of acetic acid with n-propanol,

18

isopropanol and n-butanol respectively at 3% catalyst concentration and 1:4 mole ratio

19

of acid : alcohol.

20

[6] Fig. 6a, 6c and 6e, Linear plot of ― 𝐥𝐧 (𝟏 ― 𝑿𝑨) verses time in min. and fig. 6b, 6d

21

and 6f represents the linear plot of lnk vs 1/T resulting from the esterification of acetic

22

acid with n-propanol, isopropanol and n-butanol respectively.

22 ACS Paragon Plus Environment

Page 23 of 33 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Industrial & Engineering Chemistry Research

1

[7] Fig.7a.-7c. Effect of different carboxylic acids used in the esterification reaction with

2

n-propanol, isopropanol and n-butanol respectively at 343.15 K, 180 min. and 3%

3

catalyst loading.

4

[8] Fig.8a.-8c. Charton - correlation for sulphuric acid catalysed esterification between

5

n-propanol, isopropanol and n-butanol with series of acids (acetic, propionic, butyric

6

and pentanoic acid) respectively.

7

[9] Fig.9. Effect of length and branching of n-propanol, isopropanol and n-butanol with

8

acetic acid respectively on esterification reaction of acetic acid at 353.15 K.

9 10 11 12 13 14 15 16 17 18 19 20

23 ACS Paragon Plus Environment

Industrial & Engineering Chemistry Research 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 24 of 33

1 2 3

List of Figures with Caption:

4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Fig.1a.-1c. Effect of different initial mole ratio on esterification of acetic acid with n-

21

propanol, isopropanol and n-butanol respectively, at 353.15 K and 3% catalyst loading.

22 23 24 25

24 ACS Paragon Plus Environment

Page 25 of 33 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Industrial & Engineering Chemistry Research

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22

Fig.2a.-2d. Effect of initial mole ratio on esterification of (a) formic acid at 343.15 K and

23

3% catalyst loading, (b) propionic acid at 363.15 K and 5% catalyst loading, (c) butyric

24

acid at 373.15 K and 7% catalyst loading and (d) pentanoic acid at 383.15 K and 7%

25

with n-propanol, isopropanol and n-butanol respectively.

26 25 ACS Paragon Plus Environment

Industrial & Engineering Chemistry Research 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 26 of 33

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

Fig. 3a.-3c. Effect of catalyst loading on esterification of acetic acid with n-propanol,

20

isopropanol and n-butanol respectively at 353.15 K and 1:4 mole ratio.

21 22 23 24 25 26 ACS Paragon Plus Environment

Page 27 of 33 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Industrial & Engineering Chemistry Research

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Fig.4a.-4d. Effect of catalyst loading on esterification of (a) formic acid at 343.15 K and

17

1:3 mole ratio of acid to alcohol, (b) propionic acid at 363.15 K and 1:4 mole ratio of

18

acid to alcohol, (c) butyric acid at 373.15 K and 1:4 mole ratio of acid to alcohol and (d)

19

pentanoic acid at 383.15 K and 1:6 mole ratio of acid to alcohol with with n-propanol,

20

isopropanol and n-butanol respectively.

21 22 23 24 25 27 ACS Paragon Plus Environment

Industrial & Engineering Chemistry Research 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 28 of 33

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18

Fig.5a.-5c. Effect of temperature on esterification of acetic acid with n-propanol,

19

isopropanol and n-butanol respectively at 3% catalyst loading and 1:4 mole ratio of acid

20

: alcohol.

21 22

28 ACS Paragon Plus Environment

Page 29 of 33 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Industrial & Engineering Chemistry Research

1 2

Fig. 6a, 6c and 6e. Linear plot of ― 𝐥𝐧 (𝟏 ― 𝑿𝑨) verses time in min. and fig. 6b, 6d and 6f

3

represents the linear plot of lnk vs 1/T resulting from the esterification of acetic acid

4

with n-propanol, isopropanol and n-butanol respectively.

5 6 7 8 9

29 ACS Paragon Plus Environment

Industrial & Engineering Chemistry Research 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 30 of 33

1 2 3 4 5 6 7 8 9 10 11 12 13

Fig.7a.-7c. Effect of different carboxylic acids used in the esterification reaction with n-

14

propanol, isopropanol and n-butanol respectively at 343.15 K, 180 min. and 3% catalyst

15

loading.

16 17 18 19

30 ACS Paragon Plus Environment

Page 31 of 33 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Industrial & Engineering Chemistry Research

1 2 3 4 5 6 7 8 9 10 11 12 13

Fig.8a.-8c. Charton - correlation for sulphuric acid catalysed esterification between n-

14

propanol, isopropanol and n-butanol with series of acids (acetic, propionic, butyric and

15

pentanoic acid) respectively.

16 17 18

31 ACS Paragon Plus Environment

Industrial & Engineering Chemistry Research 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 32 of 33

1 2

Fig.9. Effect of length and branching of n-propanol, isopropanol and n-butanol with

3

acetic acid respectively on esterification reaction of acetic acid at 353.15 K.

4 5 6 7 8 9 10 11 12 13 14 15 16 17 32 ACS Paragon Plus Environment

Page 33 of 33 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

1

Industrial & Engineering Chemistry Research

Table of Content:

2

3

33 ACS Paragon Plus Environment