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In the name of Allah, The most Beneficent, the most
Gracious.
A PROCESS REPORT ON COMPARATIVE STUDY OF PRODUCTION OF
ISOAMYL ACETATE BY FISCHER ESTERIFICATION USING DIFFERENT CATALYSTS
Submitted To
Institute of Chemical Engineering &Technology
University Of Punjab Lahore
In Partial Fulfillment of B.Sc. Engineering (Chemical)
By
Sajjad Rasool Chaudhry (M08-PG12) Ali Rafiq (M08-PG11) Ibrar ur Rehman Faisal (M08-PG09) Babar Rafiq (M08-PG10)
(Session 2007-2011)
Supervisor: Prof. Dr. Syed Zahoor ul Hassan Rizvi
Faculty of Engineering & Technology
Institute of Chemical Engineering & Technology University of the Punjab Quid-e-Azam Campus, Lahore, Pakistan
A PROCESS REPORT ON COMPARATIVE STUDY OF PRODUCTION OF ISOAMYL
ACETATE BY FISCHER ESTERIFICATION USING DIFFERENT CATALYSTS
This Process Report is submitted to the Institute of Chemical Engineering &
Technology, University of the Punjab Lahore, Pakistan. As per requirement for the
partial fulfillment of the B.Sc. Engineering (CHEMICAL)
Approved by:
------------------------- Project Supervisor
Prof. Dr. Syed Zahoor ul Hassan Rizvi
Faculty of Engineering & Technology Institute of Chemical Engineering & Technology
University of the Punjab Quid-e-Azam Campus, Lahore, Pakistan
Acknowledgement
Definitely nothing can be done without the will of Allah. Therefore, we are highly thankful to almighty Allah, Who made us able to explore things from His universe.
After that we are thankful to our respectable teacher, Prof. Dr. Syed Zahoor ul Hassan Rizvi who guided us about the rich information of the topic and also for his help as Director; Institute of the Chemical Engineering & Technology. He provided us a great opportunity to work in a best educational environment. No word of indebtedness can ever repay the debt, we owe to hem. Moreover we are very thankful to Dr. Javed Iqbal for his continuous help and kindness throughout the research work. The credit, if any, goes to the venerable teachers and error is because of our incompetence because mistakes are a part of learning and we would like to accept the useful suggestions from the worthy teachers. At the end we are thankful to all those who helped us in gathering data and providing information about the concerned project and words are lacking to express our humble obligations to our cherished affectionate parents, who ever remembered us in their prayers and supported us in all respects along the awful avenue to our academic achievements.
Authors
Dedicated To
Our Beloved Parents
And Teachers Whose
Proper Guidance and
Prayers
Made This All Possible
PREFACE
As food technology progresses, its impact on the human diet becomes more evident. The use of preservatives, color additives, and flavoring agents by manufacturers plays an important role in sustaining and extending the quality and quantity of food. Due to the diversity required in food flavors, Isoamyl acetate is the most famous natural identical for banana and pear flavorings.
Iso-amyl acetate is a colorless organic ester of acetic acid and Isoamyl alcohol. The most famous and conventional method of manufacturing Isoamyl acetate has been Fischer Esterification, using an appropriate catalyst and under appropriate conditions. Being a third world country, for Pakistan it’s the need of the hour to design methods for manufacturing chemicals through most economical means, and also reducing high amounts of imports from the developing/developed countries. Keeping in view, all these aspects the authors studied the preparation of Isoamyl acetate on laboratory scale, using three different types of catalyst, to choose the most appropriate one. Here, the “appropriate catalyst” signifies the catalyst which can give the maximum yield with maximum purity and minimum cost. Over the years, various catalysts have been tested upon and proven right or wrong for the process.
Though, our research work may not have contributed much to the actual advancement of the commercial use of flavors, however we have tried to expose the role of the catalyst on a very important and most commonly used flavor in food industry.
TABLE OF CONTENTS CHAPTER 1: LITERATURE REVIEW 1.1 ESTERS ................................................................................................................................................ 10
1.2 ESTERIFICATION .............................................................................................................................. 11
1.3 TYPES OF ESTERIFICATION ........................................................................................................... 11
1.3.1 BATCH ESTERIFICATION .................................................................................................... 12
1.3.2 CONTINUES ESTERIFICATION ........................................................................................... 12
1.3.3 VAPOR PHASE ESTERIFICATION ....................................................................................... 12
1.3.4 CATALYTIC ESTERIFICATION ........................................................................................... 12
1.4 PROCESS SELECTION FOR ISO-AMYL ACETATE ....................................................................... 12
1.5 FISCHER ESTERIFICATION ............................................................................................................. 13
1.5.1REACTION MECHANISM ...................................................................................................... 14
1.5.2RATE EXPRESSION ............................................................................................................... 16
1.5.3COMPLETING ESTERIFICATION ......................................................................................... 18
1.5.4PROS & CONS OF FISCHER ESTERIFICATION ..................................................................... 18
CHAPTER 2: ISOAMYL ACETATE 2.1 SIGNIFICANCE ................................................................................................................................... 21
2.2 CHEMISTRY OF AMY ACETATE ..................................................................................................... 23
2.3 CHEMICAL AND PHYSICAL PROPERTIES OF ISOAMYL ACETATE ........................................ 24
2.3.1PHYSICAL DATA ................................................................................................................... 24
2.3.2REACTIVITY .......................................................................................................................... 24
2.3.3FLAMMABILITY .................................................................................................................... 24
2.3.4STORAGE ............................................................................................................................... 25
2.3.5EXPOSURE LIMITS ................................................................................................................ 25
2.3.6SUMMARY OF TOXIC BEHAVIOR ....................................................................................... 25
2.3.7EXPOSURE SOURCES AND CONTROL METHODS ............................................................. 26
2.4 APPLICATIONS .................................................................................................................................. 27
2.5 STATUS IN PAKISTAN ....................................................................................................................... 28
2.6 ISOAMYL ACETATE: THE PAST, THE PRESENT AND THE FUTURE ........................................ 28
CHAPTER 3: RAW MATERIALS & EXPERIMENTATION
3.1 RAW MATERIALS .............................................................................................................................. 31
3.1.1 ISOAMYL ALCOHOL ............................................................................................................ 31
3.1.2 ACETIC ACID/ ETHANOIC ACID ......................................................................................... 34
3.1.3 CATALYST ............................................................................................................................ 35
3.2 EXPERIMENTAL PERFORMANCE .................................................................................................. 40
3.2.1 CHEMICAL REACTION INVOLVED .................................................................................... 40
3.2.2 PROCEDURE .......................................................................................................................... 40
CHAPTER 4: RESULTS & DISCUSSION 4.1 STOICHIOMETRIC CALCULATIONS ............................................................................................. 45
4.1.1 ISOAMYL ALCOHOL ............................................................................................................ 45
4.1.2 ISOAMYL ACETATE ............................................................................................................. 45
4.2 EXPERIMENTAL CALCULATIONS ................................................................................................. 46
4.2.1 AMOUNT OF WATER PRODUCED ....................................................................................... 46
4.2.2 ACTUAL AMOUNT OF ISOAMYL ACETATE ...................................................................... 48
4.2.3 THEORETICALLY PRODUCED AMOUNT OF ISOAMYL ACETATE ................................. 48
4.2.4 PERCENTAGE YIELD ........................................................................................................... 49
4.2.5 LABORATORY TESTS OF ISOAMYL ACETATE ................................................................. 51
4.3 TABLE OF SUMMARY OF RESULTS ............................................................................................... 54
4.4 DISCUSSION ON RESULTS: .............................................................................................................. 54
4.4.1 CONCLUSION ........................................................................................................................ 55
REFERENCES…..…..…………………………………………………………………………...57
Chapter 1 Literature Review
9
Chapter no. 1
LITERATURE REVIEW
Chapter 1 Literature Review
10
1.1 Esters [1]
Esters are derivatives of carboxylic acids. They are a class of organic compounds
which, unlike many organics, have pleasant odor.
The process of formation of ester is termed as esterification. Esters are naturally
abundant and readily synthesized, but all have the same following structure,
Several examples of Fischer esterification products has been presented in the table 1
given below.
Ester Structure Fragrance/Flavor Carboxylic Acid Alcohol
Iso-Butyl Formate
HCO2CH2CH(CH3)2 Raspberry essence acetic acid iso-
butanol Propyl Acetate
CH3CO2CH2CH2CH3 Pear essence acetic acid 1-
Propanol Iso-Amyl Acetate
CH3CO2(CH2)2CH(CH3)2 Banana essence formic acid iso-amyl alcohol
Octyl Acetate CH3CO2CH2(CH2)6CH3 Orange essence acetic acid octanol
Benzyl acetate
CH3CO2CH2C6H5 Peach essence acetic acid Benzyl alcohol
Iso-butyl CH3CH2CO2CH2CH(CH3)2 Rum essence propionic acid iso-butyl
Ethyl butyrate
CH3CH2CH2CO2CH2CH Pineapple essence butyric acid alcohol
Methyl butyrate
CH3CH2CH2CO2CH3 ‘Apple like’ essence butyric acid ethanol
Iso-amyl butyrate
CH3CH2CH2CO2(CH2)2 CH(CH3)2
Apricot essence butyric acid methanol
Iso-amyl valerate
CH3CH2CH2CO2(CH2)2 CH(CH3)2
‘real’ Apple essence valeric acid iso-amyl
Methyl anthranilate
H2NC6H4CO2CH3 Grape essence anthranilic acid alcohol
Ethyl laurate CH3(CH2)10CO2CH2CH3 Tuberose essence lauric acid iso-amyl
MEthyl salicylate
HOC6H4CO2CH3 Oil of wintergreen salicylic acid alcohol
Table-1: [2] Combinations of carboxylic acids and alcohols resulting in ‘familiar’ esters
Chapter 1 Literature Review
11
1.2 Esterification [1]
As mentioned earlier, methods used for the manufacturing of esters are generally
called as esterification. They may be mainly prepared by one of the four methods.
1) By Direct esterification of a carboxylic acid with an alcohol (Fischer Esterification).
2) From carboxylic acid derivatives by:
a) Reaction of acid anhydride and alcohol.
b) Reaction of acid salts and alkyl halides
c) Reaction of acid chloride and alcohol.
d) Reaction of amides and alcohol
e) Reaction of nitriles and alcohol
f) Reaction of ethers and alcohol.
g) Trans esterification(ester interchange)
i. Ester alcohol interchange (alcoholysis)
ii. Ester acid interchange (acidolysis)
iii. Ester-ester interchange
3) By Esters addition to unsaturated system
4) By dehydrogenation of alcohol
Different techniques are used to employ above mentioned processes. A brief
introduction of each technique or type of esterification has been discussed below.
1.3 Types of Esterification [3]
Following types of esterification are most widely used on industrial scale or in
laboratory.
• Batch Esterification
• Continues Esterification
• Vapor-Phase Esterification
• Catalytic Esterification
Chapter 1 Literature Review
12
1.3.1 Batch Esterification
Batch process was used on industrial scale but it is now regarded as the older
method of production of esters. This method is based on the use of still pot reactor and an
ordinary fractionating column (bubble cap or packed type).
1.3.2 Continues Esterification
Three major factors, namely, law of mass action, laws of kinetics and laws of
distillation operate continuously in the operation of this type. Esterification occurs only when
the concentration of the components give calculated values of the apparent equilibrium
constants which are less than the value of the true equilibrium constants; otherwise hydrolysis
occurs. As whole process is taking place continuously, exact and accurate mathematical
calculations should be applied for successful completion of the process.
1.3.3 Vapor Phase Esterification
The catalytic esterification of alcohol and acid in the vapor phase has received
considerable attention because the conversions obtained are generally higher in the
corresponding liquid phase reactions. No commercial application of the vapor phase method
has been reported.
1.3.4 Catalytic Esterification
The esterification process carried away in the presence of a catalyst is taken in
the category of catalytic esterification. Often in the absence of catalyst the rate of reaction is
very small. This rate is increased by the addition of a catalyst acting as dehydrating agent,
thus shifting the equilibrium toward the right in favor of formation of the product. Further
details are discussed later.
1.4 Process Selection for Iso-amyl Acetate [3] [4]
All processes mentioned before for the preparation of esters are not equally
satisfactory for preparation of iso-amyl acetate. Comparison between the reaction, cost of raw
material, operational efficiency and percentage conversion are made to select the best method
of preparation.
Chapter 1 Literature Review
13
The process of esterification by addition to unsaturated systems, results in secondary
and tertiary esters, if all olefins are used. So, it also results in the formation of vinyl acetate if
acetylene is used so this process cannot be used for the preparation of isoamyl acetate.
The process involving the reaction of carboxylic salts and alkyl halides, is employed
commercially for the production of isoamyl acetate, but it is very expensive. This reaction is
very rapid at room temperature, infact explosive almost. HCL gas may also be produced that
corrode the equipment. This gas causes the product to blacken, making it inappropriate for its
use in food industry. However, this method is applied only when esterification cannot be
carried out by the usual means.
The processes employing the reactions between acid chlorides/ alcohols, acid
anhydrides/ alcohols and transesterfication (Ester interchange), become very expensive, due
to very high cost of raw materials, for instance acetic finhydride, esters of acetic acid and acid
chlorides.
Moreover, acid chlorides/alcohols process, produce hydrogen chloride, which causes
corrosion and blackens the product.
However, today due to the advancements in science and technology, few alterations in
the above mentioned processes, make these reactions to be feasible and much more practical.
The process most preferable in Pakistan is Fischer Esterification of isoamyl alcohol and
acetic acid in the presence of appropriate catalyst, under specified conditions. Though the raw
material can be expensive for their use in Pakistan, but the method of preparation becomes
more economical due to high product yields and comparatively low operating cost.
1.5 Fischer esterification [5] [6]
In a Fischer esterification reaction, a carboxylic acid is exposed to an alcohol and a
strong acid catalyst that in turn yields an ester and water as the reaction products. The
reaction is reversible and the composition of the reaction mixture or position of equilibrium is
determined by thermodynamics. There are a number of ways to obtain good yields of the
product ester. Generally these methods involve the removal (or complexation) of water or the
use of a large excess of one of the reactants in order to favor the formation of the ester. Both
procedures for obtaining good yields of ester follow Le Chatelier's principle in that the
Chapter 1 Literature Review
14
removal of water or the addition of an excess of one of the reactants drives the reaction
towards formation of the ester. A typical example of Fischer esterification reaction may be as
follows:
As mentioned before, the reaction is reversible, so it must be shifted to the product
side by using excess reagent, or removing one of the products. This reaction is also limited by
any steric hindrance in the carboxylic acid or the alcohol. The presence of acid catalyst acts
as a dehydrating agent and is usually used to remove water thus keeping the reaction moving
in forward direction to favor the formation of the ester.
The ease with which esterification takes place is determined largely by the type of
hydroxyl compounds and by the acid used. In general it may be said that primary alcohols
react more readily then the corresponding secondary alcohols, while tertiary alcohols and
phenols do not react to any serious extent. So, the preparation of acyl derivatives by direct
action of carboxylic acid on an alcohol is restricted to primary and secondary alcohols.
Under special circumstances, the preparation of esters by this method is
effected by warming a solution of the acid in an excess of appropriate alcohol using a
catalyst, for instance sulphuric acid or alcohol containing hydrochloric acid. The amount of
catalyst required is only about 1-5% of the weight of alcohol used.
1.5.1 Reaction Mechanism [5]
The reaction mechanism for this reaction may be divided in the following steps:
a) Proton transfer from acid catalyst to carbonyl oxygen. It increases electrophilic
behavior of carbonyl carbon.
b) The carbonyl carbon is then attacked by the nucleophilic oxygen atom of the
alcohol
c) Proton transfer from the oxonium ion to a second molecule of the alcohol gives
an activated complex.
Chapter 1 Literature Review
15
d) Protonation of one of the hydroxyl groups of the activated complex giving a new
oxonium ion.
e) Loss of water from this oxonium ion and subsequent de-protonation giving
the ester.
All these steps can be expressed in the form of chemical equations as written as:
Formation of water in the reaction indicates that cleavage of breaking of carbonyl
oxygen bond of organic acid takes place thus releasing the -OH group as nucleophile. The
nucleophile attacks an alcohol thus forming water and releasing ester.
Therefore it can be safely concluded that “in the process of esterification of acid by
alcohol the hydrogen atom is available by alcohol while -OH group comes from acid”. The
generalized explanation of this selectiveness of the bond can also be done in the basis
Chapter 1 Literature Review
16
electronic configuration (structure) of reactants and products. Since oxygen is more
electronegative than carbon, the carbonyl carbon in the carboxylic acid acquires a positive
charge while the carbonyl oxygen acquires a negative charge.
Any compound containing the electron pair will attack the carboxylic acid thus
creating a negatively charge state. The Transition State can lose the negative charge either by
loss of hydroxyl ion or by loss of species.
1.5.2 Rate Expression [3]
The interaction between a carboxylic acid and an alcohol is a reversible process and
proceeds very slowly. Equilibrium is only attained after refluxing for several hours.
When equimolar proportions of the acid and alcohol are employed, only about two-
third of the theoretically possible yield is obtained. Conversely, when equimolar quantities of
ester and water heated together approximately one third of the ester was converted to acid
and alcohol.
In the esterification reaction
2 2 2KKRCO H RCO R H O′ ′+ → +
The rate of esterification can be represented by
[ ][ ]2K RCO H R OH′
And the rate of hydrolysis by
[ ][ ]2 2K RCO R H O′ ′
Thus if the concentration are those at equilibrium
[ ][ ] [ ][ ]2 2 2K RCO H R OH K RCO R H O′ ′ ′=
And
[ ][ ][ ][ ]
2 2
2
RCO R H OKKK RCO H R OH
′= =
′ ′
Chapter 1 Literature Review
17
The constant K is called the equilibrium constant of the reaction. Different
concentrations of the reactants and products can be present initially, but when equilibrium is
obtained the concentration of different species will be related such that the equilibrium holds.
The value of K will depend upon the particular carboxylic acid and alcohol
concentration and is determined experimentally by allowing the reaction mixture to reach
equilibrium and analyzing for reactants and products. In general, the numerical value of the
esterification constant varies between 1 to 10 for various primary and secondary alcohols and
carboxylic acids. The primary alcohols have higher value than secondary alcohols. Tertiary
alcohols have value much lesser than unity and direct esterification with carboxylic is not
practical since dehydration of alcohol will generally occur much more readily than
esterification.
The heat of reaction of many esterification reactions is nearly zero or at least quite
small. For these reactions the equilibrium constant is essentially independent of temperature.
Although the equilibrium constant indicates the extent to which esterification will
proceed. It tells nothing about the rate of reaction. The rate of reaction is affected much more
dramatically than the position of equilibrium by changes in the structure of the reactants. The
largest change is due to steric effects, with relatively little influence due to polar effects.
Because the esterification of an alcohol and an organic acid involves a reversible
equilibrium, the reactions do not go to completion: It is necessary to displace the equilibrium
in order to obtain high conversions. According to the law of mass action, the equilibrium is
displaced on favor of the ester by the use of excess one of the reactants. It is frequently
convenient to use acid in excess, however, if acid is expensive then alcohol can be taken as
an excess reactant. The excess reactant can be recovered by distillation.
The equilibrium is also displaced by removing one or both of the products as they are
formed. In practice it is generally achieved by distillation of water formed as it is insoluble
with other components of reactor and hence separated. It is first order reaction so rate
expression is proportional to 1st power of reactant.
Chapter 1 Literature Review
18
1.5.3 Completing Esterification [3]
As in industry a higher yield is achieved by disturbing the equilibrium just by
removing one of the products formed either ester or water. For the removal of any product
formed, the esterification can be divided into three broad classes depending upon the
volatility of the ester.
• Class 1
This is the class of esters formed by esterification whose boiling point is lesser than
that of the corresponding alcohol. In such case ester can be removed from the reaction
mixture by employing the distillation method. For example, methyl formate, methyl acetate,
ethyl formate.
• Class 2
Esters of medium volatility are capable of removing water formed by distillation.
These include propyl, butyl and amyl formate, ethyl propyl butyl and amyl acetate and
methyl and ethyl esters of propanic, butyric and valeric acids.
• Class 3
With the esters of low volatility several possibilities exist. In case of the esters of
butyl and amyl alcohol, water is removed as a binary mixture with the alcohol. Usually using
solvent extraction technique separates this type of ester.
1.5.4 Pros & Cons of Fischer esterification [5]
The primary advantages of Fischer esterification compared to other esterification
processes are based on its relative simplicity. Straightforward acidic conditions can be used if
acid-sensitive functional groups are not an issue; sulfuric acid can be used; softer acids can be
used with a tradeoff of longer reaction times. Because the reagents used are "direct," there is
less environmental impact in terms of waste products and harmfulness of the reagents. Alkyl
halides are potential greenhouse gases or ozone depletors and possible ecological poisons.
Acid chlorides evolve hydrochloric acid gas upon contact with atmospheric moisture, so they
are corrosive, react vigorously with water and other nucleophiles (sometimes dangerously);
they are easily quenched by other nucleophiles besides the desired alcohol; their most
Chapter 1 Literature Review
19
common synthesis routes involve the evolution of toxic carbon monoxide or sulfur
dioxide gases (depending on the synthesis process used).
Fischer esterification is primarily a thermodynamically-controlled process: because of
its slowness, the most stable ester tends to be the major product. This can be a desirable trait
if there are multiple reaction sites and side product esters to be avoided. In contrast, rapid
reactions involving acid anhydrides or acid chlorides are often kinetically-controlled.
The primary disadvantages of Fischer esterification routes are its thermodynamic
reversibility and relatively slow reaction rates—often on the scale of several hours to years,
depending on the reaction conditions. Workarounds to this can be inconvenient if there are
other functional groups sensitive to strong acid, in which case other catalytic acids may be
chosen. If the product ester has a lower boiling point than either water or the reagents, the
product may be distilled rather than water; this is common as esters with no protic functional
groups tend to have lower boiling points than their protic parent reagents. Purification and
extraction are easier if the ester product can be distilled away from the reagents and
byproducts, but reaction rate can be slowed because overall reaction temperature can be
limited in this scenario. A more inconvenient scenario is if the reagents have a lower boiling
point than either the ester product or water, in which case the reaction mixture must be
capped and refluxed and a large excess of starting material added.
Chapter 2 Iso-Amyl Acetate
20
Chapter no. 2
ISO-AMYL ACETATE
Chapter 2 Iso-Amyl Acetate
21
2.1 Significance [8] [9] [13]
Isoamyl acetate is a colorless organic ester of acetic acid and Isoamyl alcohol.
As discussed in the previous chapter, most famous and conventional method of
manufacturing Isoamyl acetate has been Fischer Esterification, using an appropriate catalyst
and under appropriate conditions. For Pakistan, being a third world country, it’s the need of
hour to design methods for manufacturing chemicals through most economical means, and
also reducing high amounts of imports from the developing/developed countries.
Keeping in view, all these aspects the authors studied the preparation of Isoamyl
acetate on laboratory scale, using three different types of catalyst, to choose the most
appropriate one. Here, the “appropriate catalyst” signifies the catalyst which can give the
maximum yield with maximum purity and minimum cost. Over the years, various catalysts
have been tested upon and proven right or wrong for the process.
With the enhancement in food technology, its impact on the human diet becomes
more evident. The global food supply has grown to depend on the quantity, quality, and
variety of wholesome and nutritious foods produced through scientific advancements in this
field. The use of preservatives, color additives, and flavoring agents by manufacturers plays
an important role in sustaining and extending the quality and quantity of food.
The Swiss company, Givaudan, one of the oldest and largest flavor and fragrance
houses in the world, manufacture flavorings for range of products, like breakfast cereals, ice
creams, herbal teas, biscuits, cake-mixes, soups and chewing-gums - Today Givaudan’s
formulations go into one in every five of the world’s artificially flavored foods; and although
the company will not name its customers, you can safely assume that it supplies most of the
big names. Thomas Hefti, senior scientist of Givandan explains that it’ll be uneconomic for
the food industry to rely solely on real bananas pears, strawberries etc.; there would not be
enough fresh fruit to go round, and besides, the individual fruit contain far too little natural
flavor to make large-scale extraction viable. Besides, we consumers apparently want those
heavily processed tastes that have become familiar.
Moreover, he adds, naturally sourced flavors may include all sorts of undesirable
residues left over from the farm: herbicides, pesticides, microorganisms, even levels of plant
toxins that, he suggests, could be harmful. In a state-of-the-art plant like Givaudan’s, the
consumer is guaranteed a healthiest end product, he suggests.
Chapter 2 Iso-Amyl Acetate
22
The secret to food flavoring popularly known as ‘creative appraisal’ of the flavors
provided by nature: although a real banana comprises around 225 volatile flavor components,
scientists can engineer an artificial alternative using just nine ingredients, with Isoamyl
acetate being the key one. A kilogram of the recipe, all mixed into a solvent - will flavor
5,000 liters of drinks. Even if it lacks the fresh fruit’s nuances, the result is impressively
familiar to anyone who has ever tasted a banana fast-food milkshake.
Isoamyl acetate is a famous replacement for banana and pear flavorings. In the past
few years, recent media had reported that bananas may be extinct within 10 years. The
Cavendish banana, found mostly on western supermarket shelves, has been under attack in
some Asian countries by a new strain of Fusarium wilt, also known as “Panama disease.”
FAO (United Nation’s Food and Agriculture Organization) has urged producers to promote
greater genetic diversity in commercial bananas, to counter the disease and meet the high
demand of bananas all year long. Here, a replacement for banana’s flavoring, Isoamyl acetate
is a pure blessing for the world masses.
Today, majority of scientists do not like the words ‘artificial’ or non-natural for
flavoring, instead the flavorings are mostly referred to as’ nature identical’. Dr Heini Menzi,
vice president for European R&D explains, ‘NI’ chemicals, are identical in their molecular
composition to ingredients found in nature. The difference is that they have been synthesized
in the lab by a chemical process - allowing a flavor originating in a plant to be manufactured
cost-effectively in vast quantities. A chemist can get to the same molecule, whether he takes
it physically out of the raw plant, or via synthesis. From a taste point of view, you could use
either.”
The importance of Isoamyl acetate does not end here. Isoamyl acetate over the years
has been used as a solvent for the major industrial polymer, cellulose nitrate. Though the
advent of other solvents for nitrocellulose, have replaced Isoamyl acetate, it still upholds its
individuality as a solvent. The popular antibiotic, pencilin relies on amyl acetate for its
extraction and purification from the fermentation broth. Due to their powerful solvency, high
volatility and mild odor, acetates are widely used in the manufacture and in the processing of
paints, coatings, adhesives, and printing industry. Furthermore, Isoamyl acetate due to its
characteristic aroma proves its significance in the manufacture of perfumes. Due to its vast
range of applications, Isoamyl acetate has proven to be one important chemical in the
industrial realm.
Chapter 2 Iso-Amyl Acetate
23
2.2 Chemistry of Amy Acetate [10]
Amyl acetate belongs to homologous series of organic compounds which are
known as esters. Esters are derivatives of carboxylic acids in which (-OH) group has been
replaced by (-OR) group.
R and R may be the same or different alkyl groups. These esters of carboxylic acid are
often referred as “Carboxylic esters”.
The Ester functional group (or function) may be presented as -CO-OR’ or -
COOR. Esters are the most important class of acid derivatives. A large number of these occur
in flowers and fruits which owe their fragrance to these compounds. They are used in many
perfumes, pesticides, fiber solvents and plasticizers. Amyl acetate (CH3COOC5H11), the ester
under consideration has the following structural formula.
Its “IUPAC” name is n-Pentyl Ethanoate. It is sometimes marketed under the
trader name of “Pantacetate or Pentasol-acetate”. Amyl is the name given due to eight
isomeric arrangements of radical C5H11.The word “amyl” is derived from Latin word
“Amylum” that means starch. Since, formerly the fusel oil (a mixture of primary alcohols
obtained by fermentation of starch), was the only significant source of five carbon alcohols
and their derivatives and then fusel oil in turn is obtained from starch hence the term ”amyl”
arose for Pentyl group (C5H11).
But the special compound we are discussing in this report is Isoamyl acetate, an
isomer of Pentyl acetate. It has structural formula as follows:
Chapter 2 Iso-Amyl Acetate
24
2.3 Chemical and Physical Properties of Isoamyl Acetate [11] [12]
2.3.1 Physical data Molecular weight: 130.18 amu
Boiling point (at 760 mm Hg) 142 oC (287.6 oF)
Specific gravity 0.876 at 15 oC (59 oF)
Vapor density 4.5
Melting point -78.5 oC (-109.3 59 oF)
Vapor pressure at 20 oC (68 oF) 4 mm Hg
Solubility Slightly soluble in water,
Soluble in most organic solvents.
Evaporation rate (butyl acetate = 1) 0.42
2.3.2 Reactivity Conditions contributing to
instability:
Heat, sparks, or flame.
Incompatibilities: Contact between Isoamyl acetate and nitrates, strong
oxidizers, strong alkalies, and strong acids should be
avoided.
Hazardous decomposition
protects:
Toxic gases and vapors (such as carbon monoxide and
carbon dioxide) may be released in a fire involving
isoamyl acetate.
Special precautions: None reported.
2.3.3 Flammability
The National Eke Protection Association has assigned a flammability rating of 3
(severe fire hazard) to isoamyl acetate. Some other specifications are:
1. Flash point: 38 oC (100 oF)
2. Auto-ignition temperature: 360 oC (680 oF)
3. Flammable limits in air (% by Vol. at 100 oC): 1.0 - 7.5
4. Extinguishing: For small fires use dry chemical, carbon dioxide, water spray, or
alcohol-resistant foam. Use water spray, fog, or alcohol-resistant foam to fight
large fires involving isoamyl acetate.
Chapter 2 Iso-Amyl Acetate
25
2.3.4 Storage
Isoamyl acetate should be stored in a cool, dry, well-ventilated area in tightly sealed
containers that are labeled in accordance with OSHA’s Hazard Communication Standard [29
CPR 1910.1200]. Containers of isoamyl acetate should be protected from physical damage
and ignition sources, and should be stored separately from nitrates, strong oxidizers, strong
alkalies, and strong acids.
2.3.5 Exposure Limits
Exposure to isoamyl acetate can occur through inhalation, ingestion, and eye or skin contact.
Limits and regulations for exposure to isoamyl acetate by different authorities are given in the
following lines.
OSHA PEL
The current Occupational Safety and Health Administration (OSHA) permissible exposure limit (PEL) for isoamyl acetate is 100 ppm (525 mg/m3) as an 8-hour time-weighted average (TWA) concentration.
NIOSH REL
The National Institute for Occupational Safety and Health (NIOSH) has established a recommended exposure limit (REL) for isoamyl acetate of 100 ppm (525 mg/m3) as a TWA for up to a 10-hour workday and a 40-hour workweek [NIOSH 1992].
ACGIH TLV
The American Conference of Governmental Industrial Hygienists (ACGIH) has assigned
isoamyl acetate a threshold limit value (TLV) of 100 ppm (532 mg/m3) as a TWA for a
normal 8-hour workday and a 40 hour workweek [ACGIH 1994].
2.3.6 Summary of toxic behavior
Effects on Animals
Isoamyl acetate is an irritant of the eyes and mucous membranes, and at high
concentrations it is a narcotic. Mice survived 2- to 3-hour exposures to 1,000 ppm
without effect, but at concentrations of 3,800 ppm for 4 to 6 hours, central nervous
system effects were seen. Cats and rabbits exposed to 900 ppm exhibited irritation of
the eyes and nose; at 5,000 ppm, the animals displayed lassitude, and some developed
diarrhea and albuminuria (indicating kidney damage). At postmortem, rabbits exposed
to isoamyl acetate on a sub-acute regimen displayed changes in the liver, congestion
and hypertrophy of the spleen, and congestion of the kidneys. Instilled into the eyes of
rabbits, isoamyl acetate caused mild and transient corneal epithelial injury.
Chapter 2 Iso-Amyl Acetate
26
Effects on Humans
Isoamyl acetate is an irritant of the eyes and mucous membranes. Human
volunteers exposed to 1,000 ppm isoamyl acetate for 30 minutes experienced
irritation, difficulty in breathing, fatigue, and an increased pulse rate. Severe throat
irritation occurs in humans at 200 ppm, and slight throat discomfort is experienced at
100 ppm. A concentration of 300 ppm is reported to be “noticeably” irritating to the
eyes; at higher concentrations, isoamyl acetate causes redness of the eyes and a
burning sensation, but no corneal damage has been reported. Exposure to
concentrations of 1,000 ppm for 30 minutes causes irritation, dyspnea increased pulse
headache and fatigue.
2.3.7 Exposure Sources and Control Methods
The following operations may involve isoamyl acetate and lead to worker exposures
to this substance:
• During the manufacture and transportation of isoamyl acetate
• Liberated during application of varnishes and nitrocellulose lacquers as protective
and finish coatings for wood, paper, metal, leather, and other surfaces by dipping,
roller coating, tumbling, knifing, or brushing
• Liberated during manufacture of nail polish, shoe polish, and furniture polish;
during fermentation of whiskey grains
• Liberated during manufacture of cellulosic photographic film by formation from
solvent solutions
• Use as a solvent of old oil colors, formaldehyde, synthetic resins, waxes, paints,
phosphors, tannins, nitrocellulose, lacquers, celluloid, and camphor, and to cover
unpleasant odors
• Use in manufacture of bath sponges, artificial leathers, artificial silk, rayon, pearls,
artificial glass, waterproof varnishes, bronzing fluids, and metallic paints
Methods that are effective in controlling worker exposures to isoamyl acetate,
depending on the feasibility of implementation, are as follows:
• Process enclosure
• Local exhaust ventilation
• General dilution ventilation
Chapter 2 Iso-Amyl Acetate
27
• Personal protective equipment (PPEs)
2.4 Applications [10] [14] [15]
Isoamyl acetate had been a very prominent and useful chemical product, and is sold
under the trade name of” banana oil” or “pear oil”. It has following important applications
a) Isoamyl acetate is one of the older and still one of the best solvents for cellulose
nitrate.
b) Amyl acetate is used in the, extraction and purification of penicillin. Penicillin is
recovered from the fermentation broth by extraction with amyl acetate after lowering
the pH, to get a favorable partition coefficient. The solvent is then treated with
buffered phosphate solution from which penicillin is eventually produced by drying.
c) It is employed in making of photographic films and moving picture films.
d) Though rarely, but it is used as an additive in American cigarettes.
e) It is employed in the manufacture of shoe polishes, silk, water proof varnishes and
bronzing liquids.
f) Furthermore, it is used for drying and finishing of textile.
g) It is recommended as standard oil in photometry.
h) It is widely used in the formation of artificial fruit flavors. For instance,
i. Banana flavored bubble gum.
ii. Sometimes found as a preservative in sodas, soft drinks, etc
iii. One form of isoamyl acetate is found in artificially pear flavored food
articles
iv. In alcohol solution as a pear flavor in mineral waters and syrups
i) Amyl acetate is also used as a solvent for celluloid, camphor, formaldehyde synthetic
and natural resins.
j) It is utilized in the making of rayon and perfumes. (Note: for use in the manufacture
of perfumes it should be free from amyl alcohol.
k) Dry cleaning preparations also employ isoamyl acetate.
Chapter 2 Iso-Amyl Acetate
28
2.5 Status in Pakistan
Reliable sources from PCSIR reported that Isoamyl acetate was being manufactured
in Pakistan in very minor quantities. The reason being the expensive raw materials, also the
fact that the product obtained was not fitting for the use in food and pharmaceutical
industries. Therefore, it is being imported from Brazil and China, to fulfill its demand in
Pakistan’s industrial realm.
2.6 Isoamyl Acetate: the past, the present and the future [10] [16]
Isoamyl acetate has been seen, tasted, or touched by many generations. Over centuries
it has been consumed by the human population, as a popular fruit known as banana. Isoamyl
acetate is the distinctive odor, taste, and color of bananas.
The discovery of isoamyl acetate can be traced back to the early 20th century. In 1920,
the Standard Oil Company of New Jersey began to produce isopropyl alcohol from light
fraction of petroleum. By 1926, Sharpless Chemical Corporation Belle, started separating
pentane from casing head gas and employed it in producing a mixture of pentyl alcohols,
including amyl alcohol and subsequently produced theft respective acetates (amyl acetate) in
order to fulfill the demands of liquor industry.
Before and during World War II, amyl acetate was popularly known as Banana Oil
and was very widely used as high boiling solvent constituent for paints coatings and resins. It
was also employed for the extraction of penicillin from the fermentation broth.
After the mid of 20th century, isoamyl acetate went on to prove its importance as an
industrial chemical. Its realm of applications has further widened over the years.
Subsequently, a variety of processes for its production have come into being.
By the year 1965, Isoamyl acetate was Granted Generally Recognized as Safe
(GRAS) status by PEMA.
By 1983, isoamyl acetate could be derived from natural gasoline, along with the
method of esterification of isoamyl alcohol with acetic acid.
Later that decade in 1989, the applications of isoamyl acetate diversified. The
following uses of isoamyl acetate were also recognized in alcohol solution as a pear flavor, in
Chapter 2 Iso-Amyl Acetate
29
mineral waters and syrups; as a solvent for old oil colors; swelling bath sponges; covering
unpleasant odors, and perfuming shoe polish.
In 1994, Isoamyl acetate as a synthetic flavoring substance was permitted for direct
addition to food for human consumption, as long as (a) it is used in the minimum quantity
required to produce its intended effect, and otherwise in accordance with all the principles of
good manufacturing practice. (b) It consists of one or more of the following, used alone or in
combination with flavoring substances and adjuvants generally recognizable as safe in food.
The use pattern which was prominent by 1990s: Isoamyl acetate being used as a solvent for
tannins, nitrocellulose, lacquers, celluloid, and camphor. It also is used as a flavoring agent in
soft drinks, chewing gum, and candies. Isoamyl acetate being applied during the
manufacturing process of artificial silk, leather, pearls, photographic films, celluloid cements,
waterproof varnish, bronzing liquids, metallic paints, dyeing, and finishing textiles.
Today, in the 2l century isoamyl acetate still keeps the status of an essential industrial
chemical. It is still being applied in the fields mentioned earlier. It is now without any doubt,
the natural identical of banana and pear fruits.
In future isoamyl acetate will withhold its reputation. Moreover if the New Science
Magazine reports (of bananas being extinct within 10 years) prove right, then it is going to be
a very important replacement for bananas for all the fruit lovers.
Due to its diverse nature in the past and present, its future is full of bright possibilities.
Chapter 3 Raw Materials & Experimentation
30
Chapter no. 3
RAW MATERIALS & EXPERIMENTATION
Chapter 3 Raw Materials & Experimentation
31
As described in 1st chapter isoamyl acetate can be prepared by Fischer
esterification reaction by the reversible, catalyzed, combination of acetic acid with isoamyl
alcohol. This method consists of heating a mixture of the acid and alcohol in the presence of
catalyst.
CH3COOH + C2H5OH → CH3COOC2H5 + H2O
The authors’ task was to prepare isoamyl acetate, using three different types of
catalysts; Paratoluene sulphonic acid, vanadium titanate and sulphuric acid.
3.1 Raw Materials
Following are the raw materials used for the preparation of isoamyl acetate.
1. Isoamyl Alcohol
2. Acetic Acid/Ethanoic Acid
3. Catalyst:
(i) Sulphuric Acid
(ii) Para-Toluene Sulphonic Acid
(iii) Vanadium Titanate
3.1.1 Isoamyl Alcohol [17] [18]
It is one of the eight isomers of amyl alcohol. Amyl alcohol may be any of 8
alcohols with the formula C5H11OH. Out of these eight isomers four are primary alcohol, 3
are secondary and 1 is tertiary. The odd carbon structure and the extent of branching provide
email alcohol with unique physical and solubility properties.
Our desired alcohol Isoamyl alcohol is the chief constituent of fermentation
amyl alcohol, and consequently a constituent of fusel oil. It is separated from fusel oil by
shaking with strong brine solution; then the oily layer is separated from the brine layer and is
distilled, the portion boiling between 125 and 140 °C is collected. For further purification it is
shaken with hot lime water, the oily layer is separated, dried with calcium chloride and
fractionated; the fraction boiling between 128 and 132 °C is collected.
Chapter 3 Raw Materials & Experimentation
32
It may also be synthesized from isobutanol by conversion into isovaleraldehyde,
which is subsequently reduced to isobutyl carbinol by means of sodium amalgam.
It is a colourless liquid of density 0.8247 g/cm³ (0 °C), boils at 131.6 °C, slightly
soluble in water, easily soluble in organic solvents. It possesses a characteristic strong smell
and a sharp burning taste. When pure, it is nontoxic, while the impure product is toxic
On industrial scale, a mixture of isomeric alcohols (1-pentanol and 2-methyl 1-
butanol) is often preferred because the different degree branching imparts a more desirable
combination of properties; they are also less expensive to produce commercially.
Three significant commercial processes for the production of amyl alcohols include:
1) Fusel oil
2) Chlorination hydrolysis process
3) Oxo process
3.1.1.1 Preparation from Fusel oil [19]
Fusel oil is a by-product of alcoholic fermentation process and is obtained during
distillation crude ethyl alcohol. Prior to the development of a synthetic process, fusel oil was
the only commercial source of amyl alcohols.
The major components of fusel oil are the primary alcohols, 3-Methyl 1-butanol and
2-Methyl 1-butanol. Fusel oil also contains water, 1-Pentanol and ethyl, propyl, butyl, hexyl
and heptyl alcohols. The product sold as refined amyl alcohol contains about 85% 3-Methyl
1-butanol (isoamyl alcohol) and 2-Methyl 1-butanol.
3.1.1.2 Preparation from Chlorination Hydrolysis Process [20]
The manufacture of first synthetic amyl alcohol by this route was begun in 1926.
Fusel oil alcohols were in limited supply and a new source of amyl alcohols and their esters
were needed to meet the increasing demand of automotive industry for higher boiling lacquer
solvents.
In this process, a mixture of amyl chlorides was first produced by continuous vapor
phase chlorination of a mixture of pentane and iso-pentane in the absence of light and
Chapter 3 Raw Materials & Experimentation
33
catalysts. Hydrolysis of chlorides with aqueous caustic at high temperature produces a
mixture of 7 of the 8 amyl alcohol isomers; formation of neopentyl alcohol is negligible.
In contrast to the fusel oil and oxo process, this method provides significance
quantities of the three secondary amyl alcohols, especially 2-pentanol.
3.1.1.3 Preparation from Oxo Process [20]
Due to the catalytic advancements made since 1970s, Oxo process also known as
hydroformylation is used now as days to obtain amyl alcohols. Due to effectiveness of this
process, comparatively high cost and waste disposal problems associated with the
chlorination hydrolysis process have been minimized. So the Oxo process is now the
principle source of amyl alcohol. In the low pressure, hydro formulation (oxo) process for the
production of amyl alcohols, 1-butene, 2-butene and 2-methyl propylene react with a mixture
of carbon mono oxide and hydrogen in the presence of suitable metal catalyst (Rhodium) to
form an isomeric mixture of aldehyde with one more carbon atom than the olefin. Once made
the 1-pentaldehyde, 2-methyl butyraldehyde and 3-methyl butylaldehyde are hydrogenated to
corresponding amyl alcohols.
Both 1- and 2- butylene mainly give 1-pentanol and 2-methyl-1-butanol.
3-methyl-1-butanol (isoamyl alcohol) is formed in much smaller amount, methyl propene
leads chiefly to 3-methyl-1-butanol, and only very small amounts of 2,2-dimethyl-1-propanol
are formed. It will be noted that in all cases the main product is primary alcohols. The
product is fractionated, and sold in three grades.
Chapter 3 Raw Materials & Experimentation
34
3.1.2 Acetic Acid/ Ethanoic acid [21] [22]
It is a corrosive organic acid having sharp odor. It is found in ocean water, oil field
brines, rain and in traces in many plants and animals liquids. Fermentation of fruit and
vegetable juices yield 2- l2% of acetic acid solutions, usually called vinegar. It is colorless
liquid and is also known commonly by these names: Ethanoic Acid, Methane Carboxylic
Acid, and Ethylic Acid. it is shipped under the name of Acetic Acid or Glacial Acetic Acid.
Commercial production of acetic acid has been revolutionized in the decade 1978 to
1988. Currently all the acetic acid is produced commercially through:
1. Acetaldehyde Oxidation,
2. Methanol or Methyl Acetate Carbonylation
3. Light Hydrocarbon Liquid Phase Oxidation
Some small amounts are also generated by:
1. Butane Liq0uid Phase Oxidation
2. Direct Ethanol Oxidation
3. Synthesis gas
3.1.2.1 Acetaldehyde oxidation
Ethanol is easily dehydrogenated through oxidation, to acetaldehyde using silver,
brass or bronze as catalysts. Acetaldehyde can then be oxidized in the liquid phase in the
presence of cobalt or manganese salts yield acetic acid. Conversion of acetaldehyde is
typically more than 90% and the selectivity of acetic acid is higher than 95%. Stainless steel
can be used in constructing the plant.
The problems in this process exist are related to more extensively automating control
of the system, notably at startup and shut down, although even these matters have been
largely solved. This route is the most reliable of acetic acid processes.
Chapter 3 Raw Materials & Experimentation
35
3.1.2.2 Methanol Carbonylation
Acetic Acid is usually was produced in 1920s by the reaction of methanol with carbon
monoxide in the presence of catalyst. A wide range of catalysts and different ranges of
pressure and temperature have been used during the century for the production of acetic acid.
The chief catalysts used are phosphoric acid, copper phosphate, hydrated tungsten oxide, and
iodides. Nickel iodide proved to be more particularly valuable.
3.1.2.3 Butane-Naphtha Catalytic Liquid Phase Oxidation:
Direct Liquid Phase oxidation of butane and/or naphtha was once the most favored
worldwide route of acetic acid because of the low cost of these hydrocarbons. Butane, in the
presence of metallic ions, e.g. cobalt, chromium or manganese undergoes simple air oxidation
in acidic solvent. The peroxide intermediates are decomposed by high temperature,
mechanical agitation and by the action of metallic catalysts, to form acetic acid and a
comparatively small suit of other compounds. Ethyl acetate and butanone are produced, and
the process can be altered to provide large quantities of these valuable materials. Ethanol is
thought to be an important intermediate, acetone forms through minor pathways from
isobutene present in the hydrocarbon feed. Formic acid, propanoic acid and minor quantities
of butyric acid are also formed. Final acetic acid purification follows much the same
treatments as are used in acetaldehyde oxidation.
3.1.3 Catalyst [23] [24]
Flowing three type’s catalyst are used for the manufacture of isoamyl alcohol.
1. Para Toluene Sulphonic Acid 2. Vanadium Titanate 3. Sulphuric Acid
3.1.3.1 Para Toluene Sulphonic Acid (PTSA):
Chapter 3 Raw Materials & Experimentation
36
Para toluene sulphonic acid is employed as such in acid form for applications where
strongly polar hydrophilic (– SO2, OH) group confers needed properties on a comparatively
hydrophobic non polar organic molecule.
For the production of PTSA, sulfonation is carried out. Aromatic sulfonation places a
sulfonic group (-SO3H) onto the benzene ring. This is accomplished by the use of Sulfur
Trioxide in the presence of Sulfuric Acid. The Sulfur Trioxide (SO3) serves two purposes. It
acts first as the sulfonating agent, and it prevents the unfavorable reversible of this
equilibrium by reacting with and effectively removing the water product thus driving this
equilibrium to the right.
SO3 + H2O → H2SO4
The Sulfonation can be accomplished without the Sulfur Trioxide by using excess
Sulfuric Acid. Then extra Sulfuric Acid will act as a dehydrating agent absorbing the water
and preventing the reversal of the equilibrium. This is not as efficient as the Sulfur Trioxide
so the reaction is much slower.
Along with p-toluene sulphonic acid, traces (about 10 to 15%) of o-toluene sulphonic
acid are also formed. Washing and distillation can result in a purer product.
Para toluene sulphonic acid is the most recent catalyst utilized in the production of
isoamyl acetate. This is a strong deactivating agent, resulting in a much more stable sulfonate
ion and a proton. This proton helps in initiating the reaction between isoamyl alcohol and
acetic acid, as shown in the reaction mechanism below.
Chapter 3 Raw Materials & Experimentation
37
REACTION MECHANISM OF THIS CATALYS
STEP 1: DISSOCIATION:
STEP2: PROTONATION:
STEP 3: NUCLEOPHILIC ATTACK (AMYL ALCOHOL):
STEP 4: HYDROGEN ION TRANSFER:
STEP 5: ELIMINATION OF PROTON AND WATER:
STEP 6: REGENERATION:
Chapter 3 Raw Materials & Experimentation
38
3.1.3.2 Vanadium Titanate (V2O5/TiO2)
Vanadium catalysts have been used widely in various organic oxidation processes,
sulfonation of aromatic compounds, preparation of hypochlorites, manufacture of sulphuric
acid etc. The authors, due to its huge popularity as a catalyst, employed one of the vanadium
compounds in the production of isoamyl acetate i.e. vanadium titanate. It is also known as a
refractory titanate.
In general, vanadium titanate can be prepared merely by hearing an intimate mixture of the
oxide of vanadium with titanium dioxide at relatively high temperature.
The vanadium titanate behaves as a lewis acid/lewis base, to act as a catalyst in the
production of isoamyl acetate.
3.1.3.3 Sulphuric Acid:
Sulphuric acid is also largely used as catalyst in amyl acetate production. It is a strong
dibasic acid. In addition, it is an oxidizing and dehydrating agent, in particularly, towards
organic compounds. The dehydrating action is very important in absorbing the water formed
in such chemical conversions as esterification, nitration and sulphonation. This causes the
reaction to move in the forward direction, as a result ensures a high yield.
Sulphuric acid has a boiling point of 270°C and relative density of 1.8357. It is
manufactured by two process contact process and chamber process. Both processes are based
on SO2, being catalytic in nature and both require air as the source of oxygen for making SO3.
Sulphuric acid is widely sold as solutions in water of various concentration or in the
form of H2S2O7 (SO3 in H2SO4) known as oleum.
Sulphuric acid is very effective as a catalyst in the manufacture of isoamyl acetate,
and it is not as corrosive to metals as hydrochloric acid. However, the product obtained by
employing sulphuric acid, is not at all fitting for the use in food and pharmaceutical
industries.
Chapter 3 Raw Materials & Experimentation
39
REACTION MECHANISM
STEP 1: DISSOCIATION:
STEP 2: PROTONATION:
STEP 3: NUCLEOPHILIC ATTACK (AMYL ALCOHOL):
STEP 4: HYDROGEN ION TRANSFER:
STEP 5: ELIMINATION OF PROTON AND WATER:
STEP 6: REGENERATION:
Chapter 3 Raw Materials & Experimentation
40
3.2 Experimental Performance [25]
3.2.1 Chemical Reaction Involved
Following chemical reaction is involved in the iso amyl acetate preparation;
3.2.2 Procedure
Following procedure was adopted in order to prepare the isoamyl acetate using three
different catalysts.
1. First of all 500g of acetic acid (limiting reactant) was weighed out and mixed it
with 845g of isoamyl alcohol (the excess reactant being 10% in excess) in a round
bottom three neck flask
2. Now 2g of PTSA (Para Toluene Sulphonic acid) was added as a catalyst in to the
reaction mixture in the first experiment.
a. In second experiment, 4g of PTSA was weighed out in to the reaction mixture.
b. For the third experiment, 4g of PTSA was weighed out as a catalyst in to the
reaction mixture.
c. For the fourth one, 4g of PTSA was taken (and distillation was carried out
before and after washing.).
d. In the fifth experiment, 4g of vanadium titanate was taken as a catalyst.
e. In the last experiment, 50g of 0.1 of sulphuric acid were taken.
3. A reflux was attached to one of the necks of the flask and heated mixture to about
100-120°C under the reflux condition till the maximum quantity of water was
obtained. The heating was carried out for 5-6 hrs.
4. After the reaction being carried out, the flask was allowed to cool down.
5. A separating funnel was taken, washed and was dried on a stand.
Chapter 3 Raw Materials & Experimentation
41
6. Following treatments were done in the sixth step:
a. For 1st, 3rd and 4th experiments, a 5% Na2CO3 solution was prepared by
weighing 25g of Na2CO3 and dissolving it in 500m1 of water. The product
mixture containing isoamyl acetate, isoamyl alcohol, acetic acid and some
quantity of PTSA was washed with 5% Na2CO3 solution in the separating
funnel. Two layers of liquid were formed; the bottom layer was drawn off, as
it was that of water and other water-soluble ionic impurities, while the upper
layer was that isoamyl alcohol and isoamyl acetate. Now, the product mixture
was washed with water at least 4 times so that pH of the product mixture was
about 7.0.
b. For fifth experiment, 10% Na2CO3 solution by weighing out 50g of Na2CO3
and was dissolved in 500m1 of water. The product mixture was firstly washed
with it and then with water at least 6 times until its pH was almost 7.0.
c. For sixth time, 8% Na2CO3 solution was prepared by weighing 40g of Na2CO3
and dissolving it in 500m1 water. Washing of the product mixture was done
with it, until the pH of 7.0 was obtained.
7. The final product mixture was containing isoamyl alcohol and isoamyl acetate.
The only method to separate these two was distillation. The distillation was
carried out in a three neck round bottom flask. During distillation the product
mixture was heated to 132-135°C so that rest of water and unreacted and excess
isoamyl alcohol should be completely separated.
8. After distillation following colors of the product were obtained;
a. In case of PTSA used as a catalyst, the final product obtained was colorless.
b. In case of vanadium titanate used as catalyst, color of the product was very
pale.
c. In case of sulphuric acid used as catalyst, color of the product was slightly
pale. (A known quantity of charcoal was taken to remove color but of no use).
9. After the experiments completed, the product samples were sent for GLC (gas-
liquid chromatography) to obtain the results.
Chapter 3 Raw Materials & Experimentation
42
Fig 3.1: Schematic Figure of Experimental Setup
1. Isomantle 2. Condenser 3. Separator 4. Motor 5. Stirrer 6. Thermometer 7. 2 Litres round bottom three neck
flask
Chapter 4 Results & Discussion
44
Chapter no. 4
RESULTS & DISCUSSION
Chapter 4 Results & Discussion
45
4.1 Stoichiometric Calculations
As acetic acid was taken as a limiting reactant, hence the quantity of other chemicals
used is taken on basis of acetic acid
Amount of acetic acid weighed out = 500g
Density of acetic acid = 1025g/cm3
Volume of acetic acid used = 500/1025 = 488ml
So, Basis: 500g of acetic acid
4.1.1 Isoamyl Alcohol
As 60g of acetic acid is to react= 88g of isoamyl alcohol
1g of acetic acid is to react = (88/60)
500g of acetic acid is to react = (88/60) x 500 = 734g
As isoamyl alcohol is used 10% in excess therefore,
Amount of isoamyl alcohol in excess = 734 x 0.1 = 73.4g
So,
Total amount of isoamyl alcohol used = 734 + 73.4 807.4
As,
Density of isoamyl alcohol = 0.8104g/cm3
Therefore,
Volume of isoamyl used = 807.4/0.8104 996.3ml
4.1.2 Isoamyl Acetate
60g of acetic acid required to produce = 130g of isoamyl acetate
1g of acetic acid required to produce = 130/60
500g of acetic acid required to produce = (130/60) x 500 =1084g
As,
Density of isoamyl acetate 0.878g/cm3
So,
Volume of isoamyl acetate to be produced = 1084/.0878 = 1235ml
Chapter 4 Results & Discussion
46
3. Water:
60g of acetic acid required to produce = 18g or water
1g of acetic acid required to produce = 18/60
500g of acetic acid required to produce = (18/60) x 500 l5Og
As
Density of water = l000g/cm3
So,
Volume of water produced = 150/1.0 = 150ml
4.2 Experimental Calculations
4.2.1 Amount of Water Produced
PTSA was used as a catalyst for Sample# 1, 2, 3 & 4, Vanadium Titanate for sample#5 and
Sulfuric Acid for Sample# 6
SAMPLE #1
Volume of water obtained = 136 ml
Amount of water not formed = 150- 136 = 14 ml
As Density of water = 1.000 g/ml
Therefore, Amount of water not formed = 14g
SAMPLE # 2
Volume of water obtained = 132 ml
Amount of water not formed = 150 – 132 =18 ml
As, Density of water = 1.000 g/ml
Therefore, Amount of water not formed = 18 g
SAMPLE #3
Volume of water obtained = 141 ml
Chapter 4 Results & Discussion
47
Amount of water not formed = 150 - 141 = 9 ml
As, Density of water = 1.000 g/ml
Therefore, Amount of water not formed= 9 g
SAMPLE # 4
Volume of water obtained = 144 ml
Amount of water not formed = 150 - 144 = 6 ml
As, Density of water = 1.000 g/ml
Therefore, Amount of water not formed = 6 g
SAMPLE # 5
Volume of water obtained = 90 ml
Amount of water not formed = 150 - 90 = 60 ml
As, Density of water = 1.000 g/ml
Therefore, Amount of water not formed 60 g
SAMPLE # 6
Volume of water obtained = 110 ml
Amount of water not formed = 150 - 110 = 40 ml
As, Density of water = 1.000 g/ml
Therefore, Amount of water not formed = 40g
Chapter 4 Results & Discussion
48
4.2.2 Actual Amount of Isoamyl Acetate
No. of Samples Weight of product
(g) Purity from GLC
(%age) Weight of Isoamyl
Acetate (g)
1 965 92.89 896
2 952 92.04 876
3 1017 91.0 925
4 1024 94.0 963
5 880 54.0 475
6 776 76.4 590
4.2.3 Theoretically produced amount of Isoamyl Acetate
SAMPLE #1:
18g of water produced with = 130g of Isoamyl Acetate
1g of water produced with = 130/18
14g of water produced = 130/18 x 14
= 101.1g of isoamyl acetate
Amount of isoamyl acetate produced theoretically = 1084 -101.1
= 982.9g isoamyl acetate
SAMPLE # 2:
18g of water produced with = 130g of Isoamyl Acetate
1g of water produced with = 130/18
18g of water produced = 130/18 x 18
=130g of isoamyl acetate
Amount of isoamyl acetate produced theoretically = 1084 - 130
= 954g of isoamyl acetate
SAMPLE # 3:
18g of water produced with = 130g of Isoamyl Acetate
1g of water produced with = 10/18
9g of water produced = 130/18 x 9
=65g of Isoamyl Acetate
Amount of isoamyl acetate produced theoretically = 1084 - 65
= 1019 g of isoamyl acetate
Chapter 4 Results & Discussion
49
SAMPLE # 4:
18g of water produced with = 130g of Isoamyl Acetate
1g of water produced with = 130/18
6g of water produced = 130/18 x 6
= 413g of Isoamyl Acetate
Amount of isoamyl acetate produced theoretically = 1084 - 43.3
= l040.67g ≈ 1041 g of isoamyl acetate
SAMPLE # 5:
18g of water produced with = 130 g of Isoamyl Acetate
Ig of water produced with = 130/18
60g of water produced = 130/18 x 60
=433g of Isoamyl Acetate
Amount of isoamyl acetate produced theoretically = 1084 - 433
= 650.6 g of isoamyl acetate
SAMPLE #6:
18g of water produced with = 130 g of Isoamyl Acetate
1g of water produced with = 130/18
40g of water produced = 130/18 x 40
= 289g of Isoamyl Acetate
Amount of isoamyl acetate produced theoretically = 1084 - 289
= 795g of isoamyl acetate
4.2.4 Percentage Yield
SAMPLE # 1
%age yield of isoamyl acetate = Actual yield
Theoritical yield
= 896/983 x 100
= 91.15 %
SAMPLE # 2
%age yield of isoamyl acetate = Actual yield
Theoritical yield
= 876/954 x 100
= 91.82%
Chapter 4 Results & Discussion
50
SAMPLE # 3
%age yield of isoamyl acetate = Actual yield
Theoritical yield
= 925/1019 x 100
= 90.77%
SAMPLE # 4
%age yield of isoamyl acetate = Actual yield
Theoritical yield
= 963/1041 x 100
= 92.51%
SAMPLE # 5
%age yield of isoamyl acetate = Actual yield
Theoritical yield
= 475/651 x 100
= 72.90%
SAMPLE # 6
%age yield of isoamyl acetate = Actual yield
Theoritical yield
= 590/795 x 100
= 74.21%
Chapter 4 Results & Discussion
51
4.2.5 Laboratory Tests of Isoamyl Acetate
1. Surface Tension
Surface tension was found out by using stalagometer. Firstly, water was taken in
stalagometer and number of drops was counted from the lower end. Similar procedure was
repeated for isoamyl acetate. Densities of water and isoamyl acetate, and the value of surface
tension of water were taken from literature. Surface tension of isoamyl acetate was calculated
using the relation:
γ2/ γ1 = n1/n2 × Q2/Q1
No. Of Samples
No. of drops of water, (n1)
No. of drops of
Each sample,
(n2)
Density of water,
p1 (g/cm3)
Density of each sample,
p2 (g/cm3)
Surface Tension of water, γ1
(dyne/cm)
Surface Tension of
each sample, γ2 (dyne/cm)
1 59 144 1.00 0.876 72.53 26.03
2 59 141 1.00 0.876 72.53 26.59
3 59 140 1.00 0.876 72.53 26.77
4 59 140 1.90 0.876 72.53 25.03
5 59 137 1.00 0.876 72.53 27.26
6 59 139 1.00 0.876 72.53 26.92
2. Relative Viscosity
Relative viscosity was calculated by using Ostwald’s viscometer. In this case, the time
of flow of both water and isoamyl acetate through its bulb was noted. The values of density
of water and isoamyl acetate and viscosity of water were taken from literature. The
relationship used for the determination of viscosity of isoamyl acetate was:
γ2/ γ1 = n1/n2 × Q2/Q1
Chapter 4 Results & Discussion
52
No. Of Samples
Time of flow for sample t1 (s)
Time of flow for
water t2 (s)
Density of sample,
p1 (g/cm3)
Density of each sample,
p2 (g/cm3)
Viscosity of water, μ1 (cP)
Viscosity of each
sample, μ2 (cP)
1 65 59 0.876 1.00 0.89 0.860
2 64 59 0.876 1.00 0.89 0.844
3 62 59 0.876 1.00 0.89 0.819
4 68 59 0.876 1.00 0.89 0.898
5 6o 59 o.87t 1.00 0.89 0.792
6 66 59 0.876 1.00 0.89 0.870
3. Specific Gravity
Specific gravity of the prepared samples of esters was found by using the specific
gravity bottle. As the volume of specific gravity bottle was 25m1, so 25m1 of both water and
isoamyl acetate was taken in it, one by one. The bottle with sample was weighed using the
electrical balance. Then, their weight ratio was taken to find out the specific gravity.
Sp. gr. = w2/w1
No. Of Samples
Weight of sp. gr
bottle (g)
Weight of sp. gr
bottle + water (g)
Weight of sp. gr
bottle + sample (g)
Weight of water w1
(g)
Weight of sample w2
(g)
Specific gravity of
sample w2/w1
1 8.21 40.79 36.20 32.58 27.99 0.859
2 8.21 40.79 36.27 32.58 28.06 0.861
3 8.21 40.79 36.31 32.58 28.10 0.862
4 8.21 40.79 36.10 32.58 27.89 0.865
5 8.21 40.79 36.92 32.58 28.71 0.878
6 8.21 40.79 36.46 32.58 28.25 0.867
Chapter 4 Results & Discussion
53
4. Refractive Index
The refractive index of the prepared sample was determined by using Abbe’s
Refractrometer. The samples were applied respectively on to the prism and the reading was
observed directly from the graduated scale.
No. of Samples Refractive Index
1 1.416
2 1.411
3 1.419
4 1.404
5 1.429
6 1.421
Chapter 4 Results & Discussion
54
4.3 Summary of Results
Sample No.
(Catalyst Used)
Color Odor Purity (%age)
%age yield
Sp. Gravity
Refractive index
Viscosity Surf.
Tension
1 (PTSA)
Colorless Banana
like 92.89 91.15 0.859 1.416 0.86 26.03
2 (PTSA)
Colorless Banana
like 92.04 91.82 0.861 1.411 0.844 26.59
3 (PTSA)
Colorless Banana
like 91.09 90.77 0.862 1.419 0.819 26.77
4 (PTSA)
Colorless Banana
like 94.00 92.51 0.865 1.404 0.898 25.03
5 (Vanadium Titanate)
Very Pale
Banana like
54.00 72.90 0.878 1.29 0.792 27.26
6 (Sulfuric
Acid)
Slightly Pale
Banana like
76.40 74.21 0.867 1.421 0.870 26.92
Standard values
Colorless Banana
like 99.00
97-99
0.868-0.878
1.400-1.405
24.85-24.97
4.4 Discussion on Results:
Table 4.3 shows the observations made in the preparation of iso amyl acetate by
esterification of amyl alcohol with glacial acetic acid. It was observed that using different
reaction conditions and catalysts, extent of reaction and purity of product varied.
Firstly, the authors used PTSA as catalyst with excess of iso amyl alcohol and
performed a series of four experiments.
Chapter 4 Results & Discussion
55
i. The first sample obtained had a purity of 92.89% from the GLC report and
percentage yield of 91.15%.
ii. For the second, purity was 92.04% and yield was 91.82%.
iii. In case of third, the purity obtained from GLC was 91.09% and percentage yield
calculated was 90.77%.
iv. For the fourth experiment, the distillation was carried out before and after
washing, and the GLC reported a purity of 94.O%O and percentage yield
determined was 92.51%.This was the maximum purity and yield obtained.
Secondly, vanadium titanate was used as catalyst and the purity of product was 54%
and the yield obtained was 72.90%.
For the last experiment with sulphuric acid as catalyst, the purity reported was 76.40
and yield determined was 74.21%.
The tests of refractive index showed a linear relationship between purity and
refractive index. As the purity decreased the observed refractive index decreased and vice
versa. For the test of viscosity, again a linear relation with purity was observed.
However, from the tests of surface tension, an inverse relation between purity and
surface tension was seen. While, there was no proper pattern in the variation of specific
gravity with purity.
All of the above samples had a banana like odor; along with color range between
colorless to pale.
4.4.1 Conclusion Three catalysts were employed in the preparation of isoamyl acetate, namely PTSA
vanadium titanate and sulphuric acid.
In case of vanadium titanate, before washing product was obtained as an emulsion, for
which thorough washing with sodium carbonate was required. After washing and distillation,
the product with minimum yield and purity was obtained. Thus, the authors completely
discourage the use of vanadium titanate as a catalyst in the manufacture of isoamyl acetate.
The results from the conventional catalyst, sulphuric acid showed greater yield and
purity in comparison to vanadium titanate. However, the use of sulphuric acid as a catalyst
was rejected, as its performance was inferior to PTSA. Also, sulphuric acid, when used in the
Chapter 4 Results & Discussion
56
large scale preparation, gives a product which is not appropriate for food and pharmaceutical
use.
From the above results, the authors concluded that the maximum yield and the most
pure product obtained were, in case of PTSA as a catalyst. So it was found to be the most
feasible catalyst, and so recommended for the future and large scale preparation of isoamyl
acetate.
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