CChhaapptteerr 55 ______________________

Esterification of Acid Oil using Ionic liquid

183

5.1 Introduction

Fuel is any material that stores energy that can be later be extracted to perform

mechanical work in a controlled manner. Most of the fuel use by humans

undergoes combustion a redox reaction in which a combustible substance releases

energy after it ignites and reacts with the oxygen in the air. Other process used to

convert fuel in to energy includes various other exothermic chemical reactions and

nuclear reactions, such as nuclear fission or nuclear fusion. Fuel is also used in the

cell of organism in a process known as cellular respiration, where organic

molecules are oxidized to release usable energy. Hydrocarbon are by far the most

common source of fuel used by humans, but many other substances such as

radioactive metals are currently used as well.

To date fossil fuel account over 80.3% of primary energy consumed in the world,

and 57.7% of that amount is used in transportation sector. On the other hand, the

global consumption of diesel fuel is estimated to be 934 million tons per year.

Thus the world energy forum predicted that fossil oil will be exhausted in less than

10 decades, if new oil were not found stated by Man et al. (2010). The high energy

demand in the industrialized world as well as in the domestic sector and pollution

problems caused due to the widespread use of fossil fuels make it increasingly

necessary to develop the renewable energy sources of limitless duration and

smaller environmental impact than the traditional one. This has stimulated recent

interest in alternative sources for petroleum-based fuels. Meher et al. (2004)

explained that an alternative fuel must be technically feasible, economically

competitive, environmentally acceptable, and readily available the energy trend

offers a challenge as well as an opportunity to look for substitutes of fossil fuels

for both economic and environmental benefits. Biofuel can be produced from any

carbon source that can be replenished rapidly e.g. plants. Many different plants

and plant derived materials are used for biofuel manufacture. Recently biofuel

have been developed for use in automotive transport.

Biodiesel is the name of a clean burning alternative fuel produced from domestic,

renewable resources. These can be fatty acids derived from vegetable oils or

animal fats. Pure Biodiesel does not contain any petroleum diesel but can be

184

mixed to create what is known as a biodiesel blend. At the correct blends it can be

used in normal diesel engine with no major modifications. Biodiesel is simple to

use, biodegradable, nontoxic, and essentially free of sulphur and aromatics.

The use of biodiesel in a conventional diesel engine results in a substantial

reduction of unburned by hydrocarbons, carbon monoxide and particulate matter

compared to emissions from diesel fuel. In addition, the exhaust emission of sulfur

oxide and sulfates from biodiesel are essentially eliminated compared to diesel. Of

the major exhaust pollutants, both unburned hydrocarbons and nitrogen oxides are

ozone or smog forming precursors. The use of biodiesel results in a substantial

reduction of unburned hydrocarbon.

Biodiesel is the best greenhouse gas mitigation strategy for today’s medium and

heavy duty vehicles. A 1998 biodiesel lifecycle study jointly sponsored by the

U.S. Department of Energy and the U.S. Department of Agriculture, concluded

biodiesel reduces net carbondioxide emissions by 78% compared to petroleum

diesel. Biodiesel has highest energy balance of any transportation fuel. The

analysis shows for every unit of fossil energy it takes to make biodiesel, 3.2 units

of energy are gained. This takes into account the planting, harvesting, fuel

production and fuel transportation to the end user. So it produces 3 times more

energy than it takes to make it. Pure biodiesel emissions have decreased level of

polycyclic aromatic hydrocarbons PAH and nitrited PAH compounds. Also,

particulate matter, an emission linked to asthma and other diseases, is reduced by

about 47 % and carbon monoxide, a poisonous gas, is reduced by about 48%.

Biodiesel production by transesterification of vegetable oils and animal fats is one

of the bio-based alternatives to fossil fuels. Biodiesel has been gaining worldwide

popularity as an alternative energy source because it is non-toxic, biodegradable

and non-flammable and has significantly fewer emissions than petroleum based

diesel (petro-diesel) when burned as reported by Bajpai and Tyagi (2006). These

positive attributes have attracted the attention of the scientific community,

industries and government agencies worldwide for a step ahead in making

biodiesel fuel for usage in the transportation sector. It however, also presents few

constraints which have to be taken care of during its production, storage and

utilization as a fuel studied by Sharma and Singh (2010). In conventional

185

processes, biodiesel is manufactured by the transesterification of oils with

methanol in the presence of catalysts such as alkali, NaOH, KOH.

Transesterification consists of a number of consecutive, reversible reactions: the

triglyceride is converted stepwise to diglyceride, monoglyceride and finally

glycerol. The methanol is used commercially because of its low price. Thus the

resulting esters are called fatty acid methyl esters (FAME or biodiesel) (Jin et al.,

2008). Transesterification reactions can be alkali-catalyzed, acid catalyzed or

enzyme catalyzed. As for enzyme catalyzed it requires a much longer reaction

time than the other two systems (Zhang et al., 2003).

The use of edible vegetable oils and animal fats for biodiesel production has

recently been of great concern because they compete with food materials. As the

demand for vegetable oils for food has increased tremendously in recent years, it is

impossible to justify the use of these oils for fuel use purposes such as biodiesel

production. Moreover, these oils could be more expensive to be used as fuel

(Chhetri et al., 2008). Since most of the fatty acid methyl esters (FAME) produced

commercially today is made by the alkali-catalyzed reaction from high quality

virgin oil, the cost of biodiesel is relatively higher than petroleum-based diesel. It

costs approximately one and a half time of petroleum-based diesel. It is reported

that approximately 70-95% of the total biodiesel production cost of the raw

material; that is, vegetable oil or animal fats (Jin et al., 2008) As an alternative to

fossil fuel biodiesel is technically feasible, economically competitive,

environmentally acceptable, and readily available.

In order to reduce the production costs and to make it competitive with petroleum

diesel, low cost feedstocks, such as non-edible oils and waste frying oils, can be

used as raw material (Zhang et al., 2009). A lot of research is going on using non-

edible oils like Jatropha oil, karanja oil, mahua oil, soapnut, tobacco seed oil, rice

bran oil, rapeseed oil, neem oil etc as potential source for biodiesel production.

Still for making biodiesel from non-edible oil, initial investment in terms of land

and maintenance is high as compared to acid oil, waste oil etc. So potential

research is going on for exploring Acid oils, waste oil, used frying oils as vital

source for biodiesel production.

186

The use of wastes for biodiesel production has three major advantages:

� Do not compete with the food market;

� Recycle wastes; and

� Reduces production costs and therefore increasing biodiesel economic

competitiveness (Dias et al., 2009).

However the waste oil, acid oil etc contains significant amount of free fatty acids

(FFA), which cannot directly undergo alkali catalyzed transesterification reaction

because FFAs react with alkali catalyst to form soaps, resulting in serious

emulsification and separation problems.

Several methods have been proposed to solve these problems (Serio et al., 2005):

a) Alkali refining method: an alkali such as caustic soda is added to transform

FFA in to fatty acid soaps and these are then removed by washing with

water;

b) Excess addition of catalyst method: in addition to the amount of catalyst

sufficient for transesterification, an excess of alkali is added;

c) Solvent extraction method: free fatty acids are removed by extraction with

a selective solvent;

d) Distillation refining method: FFA are distilled away from the oil:

e) Pre-esterification method: FFA are firstly esterified to FAME by using an

acidic catalyst:

R

O

OH

+

OH

HH

HR

O

Me

+ H2 O

Acid Methanol Ester Water

Figure 5.1 Schematic representation of esterification reaction

187

The first four methods described above results in product (biodiesel) loss, also

excessive addition of alkali results in the formation of emulsion which in turn

causes separation problems due to the formation of soaps. Distillation requires

high energy usage. So finally only the last method seems to be a viable option and

also this method was used for carrying out transesterification for oils like Jatropha

oil, karanja oil, waste oils etc.

188

5.2 What is Acid Oil?

Use of Fried oil, waste oil, and nonedible oil is reported to be economic, collection

and availability of required quantities for such types of oils is still at its nascent stage

in the country. To make biodiesel as viable programme, alternate resources which are

economic sufficient and readily available are to be identified and appropriate type of

technology which can produce biodiesel of acceptable quality is too developed.

Acid oil which is a byproduct of vegetable oil refinery operation may prove a viable

source, as it is cheap and readily available in significant quantities as unutilized by

product. Chemical composition and fuel properties of acid oil are determined.

Acid oil is a by-product in the neutralisation step of vegetable oil refining and is

an alternative source of biodiesel fuel. Acid oil predominantly consists of long

chain free fatty acid mixture along with small amounts of mineral acids(1-2%),

free moisture(5-8%), phospholipids and sterols(8-10%) which all impart a

characteristic pungent odour and dark brown colour to acid oil. Acid oil because of

its oxygenated nature and chain type of configurational compounds, Kulkarni et al.

(2008) showed the difference in the properties of the biodiesel produced from acid

oil with diesel fuel. Acid oil is produced during the acidulation process involved in

the refining of vegetable oil as shown in the figure 5.1

During refining of vegetable oil many steps are involved like Degumming, caustic

refining, deodorizing, vacuum bleaching etc. In the neutralisation process, crude

oil from storage is fed to cylindrical tanks equipped with heating coils and stirrers.

The oil is heated to 80°C while being stirred, and a measured amount of NaOH

solution is introduced by spraying on the surface of the oil. An excess of 5-10%

NaOH over the stoichiometric requirement is added to ensure appropriate

neutralization of FFAs. In this stage, hydrated gums migrate to the water phase.

Heating and stirring are stopped when soap “breaks” are formed. A break forms as

soap coagulates with some occluded neutral oil, excess NaOH and other

impurities. The aqueous soapstock is allowed to settle and subsequently drawn off

for acidulation with H2SO4 to recover a mixture of fatty acids, occluded neutral

oil, and other impurities. The mixture is called Acid oil describe by Hui. (1945).

189

Acid oil is typically sold as a feed ingredient energy source but may also be used

as a feedstock for soaps, fatty acids, distillation and purification and other

industrial application. Because of the fluctuation in demand of soap stock and also

the low market price, methods are being developed to utilise it as a vital source.

Figure 5.2: Flow diagram for Acid oil formation

Caustic Soda

Crude Oil with excess FFA

Aqueous Soap stock solution i.e. salt solution of FFA

H2SO4

Acid WaterAcid Oil

190

5.3 Esterification Reaction

Esterification is a reaction in which Carboxylic acid is converted to Ester in presence

of acid catalyst and at elevated temperature. The esterification reaction is usually

catalyzed by a homogeneous acidic catalyst such as sulphuric acid, p-toluenesulfonic

acid and solid acid. Sulphuric acid cannot be reused and it has other disadvantages

such as equipment corrosion, more by-products, tedious work up procedure and

environmental problem. P-toluenesulfonic acid also has some disadvantages such as,

difficult separation from products, more consumption of energy and higher cost stated

by zhang et al. (2009). The use of heterogeneous acid catalysts to replace

homogeneous ones has been considered to eliminate the problems associated with

homogeneous acid catalysts. There are several reports about the use of heterogeneous

acid catalysts to produce biodiesel, including Zeolites, La/Zeolites beta, MCM-41,

Silica-supported zirconium sulphate, Amberlyst-15 and Nafion. However,

heterogeneous acid catalyst commonly is hydrophilic, and its activity will be

decreased by the water produced from the esterification of FFA. This is because the

acid catalysis over these inorganic oxide solid acids occurs at the acidic hydroxyl

groups (-OH), which act as strong Bronsted acid sites, and the acid strength of these

would be reduced by the hydration of –OH when water is present was explained by

Shu et al. (2010).

One of the most important targets of modern industry is to combine the advantages of

both homogeneous and heterogeneous catalysis. Greater selectivity is generally

observed in homogeneous catalysis compared to its heterogeneous counterparts, but

separation of the catalyst from the product stream or from the extract stream causes a

problem. ILs offers the advantages of both homogeneous and heterogeneous catalysts

with their two main characteristics: A selected IL may be immiscible with the

reactants and products, but on the other hand the IL may also dissolve the catalysts.

ILs combines the advantages of a solid for immobilizing the catalyst, and the

advantages of a liquid for allowing the catalyst to move freely. Brennecke and

Maginn indicated that the ionic nature of the IL also gives an opportunity to control

reaction chemistry, either by participating in the reaction or stabilizing the highly

polar or ionic transition states as explained by Keskin et al. (2007). ILs are used as

catalyst in various organic reaction like Esterification reaction, Friedel-Crafts

alkylation reaction, Oxidation, Reduction reactions etc.

191

The unique properties of ILs and the choice available to design ILs by combining

various anions and cations have created many more processing options. However,

high cost, lack of physical property and toxicity data restrict the advantageous use of

ILs as process chemicals and processing aids at the present.

If the performance of an IL is extremely higher than that of the other material

(solvent) it aims to replace, less amount of IL may be needed for a given specific job,

thus totally or partially overcoming the price disadvantage. Another barrier to the

large scale application of ILs is due to their high viscosities. The viscosity of ILs are

too high comparable to that of oil. Because of which it reduces the rate of reaction and

even a reduction in the diffusion rates of species. Also, handling of ILs with high

viscosities is difficult however; increasing temperature, changing anion–cation

combinations may yield ILs with lower viscosities. To overcome mass transfer

limitations in gas-IL systems resulting from high viscosity reactions using ILs may be

run at high pressures and in efficient gas–liquid contacting equipment.

In chemical processing, pharmaceuticals, fine chemicals, petroleum refining, metal

refining, polymer processing, pulp and paper, and textiles where a nonvolatile liquid

with a wide liquidus range could work better, ILs are the best choice however, the

challenges of turning ILs into useful and environmentally benign fluids must be

overcome.

In addition to the fact that they are now commercially available, there is a better

understanding of the effect of ionic liquids (chemical and physical properties as well

as engineering fluids). Consequently, ionic liquids have been used more widely and

efficiently, with better control over the overall process. Smiglak et al. (2007)

introduces the structural functionalities on the cationic or anionic part has made it

possible to design new ILs with targeted properties. More recently, ILs appear to be

the subject of fundamental publications aimed at improving the understanding of

these solvents, predicting their physicochemical properties and publications

describing their use in increasingly diverse applications such as sensors, fuel cells,

batteries, capacitors, thermal fluids, plasticisers, lubricants, ionogels, extractors and

solvents in analysis, synthesis, catalysis and separation, to name just a few. The

contribution ILs make to homogeneous catalysis has more to do with the enhancement

of catalytic performances (activity, selectivity or new chemistry) and the possibility of

192

catalyst separation and recycling by immobilization in the IL-phase than with

environmental concerns as stated by Olivier-Bourbigou et al. (2010)

For these reasons, ionic liquid was investigated as catalyst for the esterification

reaction in the present work.

In order to overcome the adverse effect of these mineral acids it has been replaced by

a more efficient and greener catalyst known as “IONIC LIQUID”. Ionic liquid has

attracted much attention in recent years as clean and promising catalyst because of its

properties like wide liquid range, negligible vapour pressure, excellent chemical and

thermal stability, design possibilities and easy recoverability.

193

5.3.1 Mechanism of the reaction

Step 1: Acid takes a proton (a hydrogen ion) from the [IL]. The proton becomes

attached to one of the lone pairs on the oxygen which is double bonded to the carbon.

O

R OH

[IL] H+

OH+

R OH

C+

R OH

OH

R OH+

OH

Step 2: The positive charge on the carbon atom is attacked by one of the lone pairs on

the oxygen of the alcohol molecule

C+

R OH

OH

+ ROH

ROH

OHO

+

R

H

Step 3: Proton gets transferred from one of the oxygen atom to other.

ROH2

+

OHO

R

ROH

OHO

+

R

H

194

Step 4: A molecule of water is lost from the ion

ROH2

+

OHO

RC

+

R

OHO

R

Step 5: The hydrogen is removed from the oxygen by reaction with the IL ion which

was formed in the first step

C+

R

OHO

R

[IL]

R O

R

O

195

5.4 Literature Survey

Esterification is the general name for a chemical reaction in which an acid molecule

reacts with an alcohol to form an ester and a water molecule.

Esterification is a reversible reaction and the reaction moves in forward direction by

using excess alcohol. Esterification reaction is generally carried out using acidic

catalyst like sulphuric acid, p-toluene sulphonic acid etc. But this catalysts leads to

several other problems like corrosion of equipment and also requires tedious

isolation of products. Heterogeneous catalyst because of their corrosive nature, high

cost and unstable nature cannot be used in production centres.

Ionic liquids are emerging as green reaction media (catalyst + solvent). ILs has

recently gained recognition as possible environmentally benign alternative media in

various chemical processes. As ILs is entirely constituted of ions and owing to their

low vapour pressure, they do not contribute to any VOC emissions.

The use of ionic liquids in esterification reaction has been limited to the derivatives

of imidazole and pyridine. A lot of research articles are available on esterification of

acids using ionic liquids. Dubreil et al. (2002) carried out esterification reaction in

various ILs with HSO4- , H2PO4 as counteranions and found that nature of both the

counteranion and cation influences the behaviour of catalyst. Gui et al. (2004)

showed the effect of three new halogen-free Bronsted acidic ionic liquids, 1-(4 -

sulphonic acid) butyl-3-methylimidazolium hydrogen sulphate, 1-(4-sulphonic acid)

butylpyridinium hydrogen sulphate and N-(4-sulfonic acid) butyl triethylammonium

hydrogen sulphate on esterification reaction. Out the three catalyst; 1-(4 -sulphonic

acid) butyl-3-methylimidazolium hydrogen sulphate, gave better conversion

suggesting that cation of IL has a little impact on catalyst performance.

Joseph et al. (2005) reported the use of Bronsted acidic ionic liquid containing

nitrogen based organic cations 1-methylimidazole and 1-butyl-3-methylimidazolium

and inorganic anions of the type BF4-, PF6

- and PTSA- for esterification of acetic

acid. Maximum substrate conversion 100% and maximum selectivity was achieved

for [BMIM][PTSA-]. Ganeshpure et al. (2007) demonstrated the use of simple

triethylammonium salts as ionic liquid media for esterification reaction.

196

Transesterification is an organic reaction in which a triglyceride reacts with an

alcohol in presence of strong acid or base to form fatty acid alkyl ester and glycerol.

The overall process is a sequence of three consecutive and reversible reactions.

When oil contains high Free Fatty Acid (FFA) direct transesterification cannot be

done. Our feedstock acid oil contains high FFA, because of which its direct

transesterification was not possible as it will lead to soap formation. The work done

on Acid oil as source for production of fatty acid alkyl ester is summarised below:

Haas et al. (2003) using acid oil as the source and sulphuric acid as catalyst followed

two different methods to produce fatty acid alkyl ester. In the first method, they

carried out esterification of oil for 26 hrs using sulphuric acid as catalyst, but still the

oil had some residual amount of FFAs. So an alternative approach was developed,

according to which, the acylglycerols species in soapstock were saponified prior to

acidulation. High-acid (HA) acid oil made from this saponified soapstock had an

FFA content of 96.2 wt%. So again esterification was carries out for 14 hrs, FAME

recovery under this condition was 89% of theoretical, and the residual unesterified

FFA content was approximately 20 mg/g. This was reduced to 3.5 mg/g by washing

with NaCl, NaHCO3 and Ca(OH)2 solutions. Also an alternative step to washing was

by subjecting the unwashed layer to a second esterification step.

Hammond et al. (2005) suggested a three step acid catalyzed esterification process

using sulphuric acid as catalyst.

Wattanbe et al. (2007) carried out the conversion of acid oil to FAME using a two

step reaction system, comprising methyl esterification of FFAs and Methanolysis of

acylglycerols using immobilized Candida antarctica lipase. But in the second step

they added some amount of refined oil in addition to 10 wt% glycerol, to convert

acylglycerols to FAMEs.

Kulkarni et al. (2008) used “ED3R” esterification process developed at the institute

(Bapuji institute of engineering and technology, Davangere) using sulphuric acid as

catalyst. No specific details about the process were given in literature.

Chen et al. (2008) showed used different enzymes namely: Soluble lipase NS81006

and NS81020 produced from Aspergillus oryzae / Aspergillus niger for carrying out

the reaction

197

The results obtained from this process suggested that enzyme concentration,

temperature, molar ratio of methanol to oil and stirring speed were the significant

factors on the yield of fatty acid methyl ester and a quadratic polynomial equation

was obtained for methyl ester yield by multiple regression analysis.

Park et al. (2010) carried out esterification of acid oil using WO3/ ZO2, zeolite as

catalyst. The process required high amount of solid catalyst up to about 20 wt%, but

the process gave a good conversion.

Since acid oil contains high amount of FFAs, so it is very difficult to directly

transesterify such oil using commercially available alkali transesterification

technique. Some researchers in their study used two- step procedure to treat the high

free fatty acid content oil. Ghadge and Rehman in 2004 studied biodiesel production

from oils containing high FFAs; they suggested a two step process to reduce the

FFAs. Similarly Ramadhas et al. (2004) suggested the usage of two step process to

reduce the FFAs. So for acid oil; initially esterification using ionic liquid was done

followed by transesterification using an alkali catalyst.

198

5.5 Experimental Data

5.5.1Pretreatment to Crude Acid Oil (CAO):

Crude Acid Oil (CAO) contains small solid particles and some moisture. These were

removed by treating it as, first it were heated at 100oC for 1 hr, after cooling it were

centrifuge, to settle down solid particles. These solid particles were removed through

filtration. Traces of water were removed by passing it through 10% silica column then

again filter to remove small particles of silica. These procedures were repeated four

times to remove traces of water present in CAO, which can inter the reaction

equilibrium.

5.5.2 Quality characteristic of CAO

The physiochemical properties of CAO were studied and shown in Table 1. Due to

high FFA content, transesterification of oil cannot be done first.

Table 5.1: Physical properties measured for Acid Oil obtained from refinery.

Properties Values

Free fatty acid content (FFA) 62.04%

Density (at 25°C) 0.914 g/cm3

Saponification value 195 mg KOH/g

Iodine value 111.16

Specific gravity 0.917 g/cm3

199

5.5.4 Synthesis of IL

1-Butyl-3-methylimidazole hydrogen sulphate [BMIM][HSO4] were prepared by

following reported procedure of Neeraj et al.(2007), whereas 1-Butyl-3-

methylimidazole boron tetraflouride [BMIM][BF4] were prepared following the

method of Joseph et al.(2005), for 3-methylimidazole hydrogen sulphate [Hmim][

HSO4] as explained by Wang et al..(2008) and confirmed by H1 NMR technique.

5.5.5.1 Synthesis of [TTDP][HSO4]

[TTDP][Cl] was obtained by CYTEC IL Company Ltd. further it was converted to

[TTDP][HSO4]. Initially [TTDP][Cl] were taken in round bottom flask diluted with

methanol as solvent. Equimolar of well dried KHSO4 powder was added slowly to the

mixture. It was kept for constant stirring for 24 hrs at 700rpm. Towards the

completion of the reaction white solid settles down at the bottom. Above solution

were decanted slowly as well as evaporating methanol to get colourless viscous Ionic

Liquid. Solid which settles down at the bottom were three times well sluiced with

methanol to remove the traces of IL on its surface; these methanol layers were

evaporated to give IL. Pale yellow viscous IL with 87% yield was obtained. It were

further analysed by H1NMR.

5.5.6 Esterification reaction:

Initially, oil was heated to 1000C for about 1hr to remove the moisture present in it.

Free Fatty Acid (FFA) content was determined using AOCS official method Ca 5a-

40. Acid oil had an initial FFA content 62%, which is far above the 1% limit for

satisfactory transesterification reaction using alkali catalyst. Therefore FFA was first

converted to ester in esterification.

Acid oil was heated at 100oC for 1 hr, after removing moisture from the acid oil,

calculated amount of IL as a catalyst i.e. 2 wt% of oil and methanol is taken in excess,

which act as reagent and solvent. On completion of the reaction, reaction mixture

poured in separating funnel. The two different separate layers were collected

200

separately. Upper layer which contains excess alcohol were reuse, after distillation,

where as lower oil layer which also contains ionic liquid, were further processed by

giving washing and removing ionic liquid catalyst for reuse.

FFA obtained from upper layer is analysed by using Gas Chromatography (Chemito)

using DB-23 capillary column with Flame Ionised Detector (FID) detector.

Temperature were maintain at 1400C for 1min, which were slowly increased by

30C/min up to 1800C holding for 2 min, which were again raise by rate of 40C/min up

to 2200C for 5 min.

Effect of ILs with difference in alkyl chain length, were studied along with change of

cation and anion. Different ILs with varying catalyst loading were studied. Namely 1-

hydrogen-3-methyl imidazolium sulphate, 4-butyl-3-methylimidazolium hydrogen

sulphate, 4-butyl-3-methylimidazoilum hydrogensulphate and tetraphosphonium

hydrogen sulphate were used and studied.

5.5.7 Determination of FFA content:

The FFA content was determined using AOCS official method Ca 5a-40. The general

steps involved in the procedure are as follows:

Initially take 0.1g of sample in a conical flask, to it add 10ml isopropyl alcohol and

shake properly so as to ensure a uniform mixture. To the mixture add 2-3 drops of

phenolphthalein indicator solution and perform the titration against 0.1N NaOH

solution until pink colour persists for about 10 seconds. Also take one blank reading

i.e. only of isopropyl alcohol. The FFA content was calculated using the following

formula:

[(A-B) x N x28.2]

Weight of oil

Where, A= ml of NaOH solution required for the test sample

FFA =

201

B= ml of NaOH solution required for the blank sample

N= Normality of NaOH solution.

% Conversion was calculated using the following formula:

% Conversion = (Initial FFA – Final FFA) x 100

Initial FFA

5.5.8 Determination of Iodine value:

Iodine value was determined using Wijs reagent. Initially appropriate quantity of

sample was taken in round bottom flask. To the sample 15 ml of carbon tetrachloride

and 25 ml of Wijs reagent was added and gentle shaking was given. The mixture was

kept in dark for about 1 hr. After 1 hr, 20ml of 10% potassium iodide (KI) solution

and 100 ml distilled water was added to the mixture. The final solution formed was

titrated against 0.1 N sodium thiosulphate (Na2S2O3) solution using starch as

indicator. It was titrated till blue colour just disappears after vigorous stirring.

� �M

NVBIVeIodineValu ����

69.12)(

Where, N = Normality of the sodium thiosulphate solution

M = Mass of the test sample in grams.

B = ml of sodium thiosulphate solution required for the blank test.

V = ml of sodium thiosulphate solution required for the test sample.

202

5.6 Result and Discussion

Acid oil prepared by acid dilution of soapstock consists of almost 60–70 % FFA.

These were successfully esterified to FAME (Free Acid Methyl ester) using methanol

as reagent as well as solvent, since it was taken in excess. Effect of various

concentration of methanol has been studied.

5.6.1 Effect of speed of agitation:

Speeds of agitation were studied to evaluate the presence of interfacial mass transfer

resistance between catalyst and organic reactants. Speeds of agitation were varied

from 900 rpm to 1300 rpm as shown in the Figure 5.3. Conversion of FFA remains

virtually constant after 1100 rpm, which signifies the absence of external mass

transfer resistance after 1100 rpm.

Figure 5.3: Effect of speed of agitation on conversion of FFA with different IL used ; such as (X) [TTDP][HSO4] ; ( ) [BMIM][HSO4]; ( ) [HMIM][HSO4] ; ( )

[BMIM][BF4]. Reaction temperature = 60 oC ; catalyst loading 2 wt % ; reaction time = 2 hr.

0

10

20

30

40

50

60

70

80

90

100

800 900 1000 1100 1200 1300

% C

onve

rsio

n of

FFA

Speed of agitation (rev/min)

203

5.6. 2 Effect of molar ratio of methanol to oil

The molar ratio of alcohol to oil in esterification reaction is 3:1 stoichiometrically,

but, scientifically because of equivalent reaction, it requires greater amount of alcohol

for completing the reaction. In this step, the effect of molar ratio 3:1, 4:1, 6:1, 8:1 and

10:1 of methanol to oil were considered. The reaction conditions maintained at 60oC

with 2 %wt catalysts, 1100 rpm and 2 hrs. The results are shown in Figure 5.4, at the

molar ratio of 6:1 for alcohol to oil shows the highest efficiency for ester production

and acid value reduction.

Figure 5.4: Effect of Oil : Methanol molar ratio on conversion of FFA with different IL used ; such as (X) [TTDP][HSO4] ; ( ) [BMIM][HSO4]; ( ) [HMIM][HSO4] ;

( ) [BMIM][BF4]. Reaction temperature = 60 oC ; catalyst loading 2 wt % ; reaction time = 2 hr at 1100rpm.

0

20

40

60

80

100

120

1:01 1:03 1:04 1:06 1:07 1:09 1:10

% C

onve

rsio

n of

FFA

Oil : Methanol Molar ratio

204

5.6.3 Effect of catalyst loading

Specific amount of catalyst is needed for the slow esterification reaction. The

reactions were done with different catalyst weight percentages. This reaction were

performed at 60oC temperature with molar ratio 6:1 methanol to oil and stirrer speed

of 1000 rpm and 0.5, 1, 1.5, 2, 2.5, 3 %wt of catalyst to the amount of oil taken. As

shown in Figure 5.5, with increasing weight percentage of catalyst from 0.5 to 3 %

wt, the percentage of free fatty acid conversion to methyl ester increased and the acid

value of oil decreased to less than 1%. With increase amount of catalyst to 2 to 2.5

%w no visible change shown in the conversion and acid value. The suitable catalyst

concentration is 2 %wt of catalyst.

Figure 5.5: Effect of catalyst loading on conversion of FFA with different IL used ; such as (X) [TTDP][HSO4] ; ( ) [BMIM][HSO4]; ( ) [HMIM][HSO4] ; ( ) [BMIM][BF4]. reaction conditions , Oil : Methanol ratio 1:6 ; reaction temperature : 60 oC ; catalyst loading: 2 wt % ; reaction time : 2hr at1100 rpm.

0

10

20

30

40

50

60

70

80

90

100

0 0.5 1 1.5 2 2.5 3 3.5

catalyst amount wt (g)

%

Con

vers

ion

of F

FA

205

5.6.4 Effect of temperature

Temperature has significant effect on the rate of reaction. For 2wt% concentration of

catalyst, molar ratio of 6:1 of methanol to oil and temperatures variables to 40oC, 50oC, 60 oC, 70 oC, and 80 oC. In 2hrs, as shown in Figure 5.6, increase of temperature

from 50 to 60 shows increasing the percentage of ester conversion and decreased of

acid value to less than 1%. Increasing the temperatures higher than 60 reduces the

efficiency of reaction because increasing temperature more than boiling point of

methanol (64 oC), reduces amount of methanol in reaction mixture.

Figure 5.6: Effect of Temperature on conversion of FFA with different IL used ; (X)[TTDP][HSO4] ; ( ) [BMIM][HSO4]; ( ) [HMIM][HSO4] ; ( ) [BMIM][BF4].Reaction conditions, Oil : Methanol 1:6 molar ratio ; catalyst loading: 2 wt %; ; reaction time : 2 hr at 1100 rpm

0

20

40

60

80

100

120

40 50 60 70 80

Temperature oC

% C

onve

rsio

nof

FFA

206

5.6.5 Reusability of IL

IL can be reused for the reaction by simply removing water under vacuum. Good

conversions of FFA were observed. For [TTDP][HSO4] IL we can observe around

97% conversion which remains almost same over 3rd as seen from Figure 5.7. Use of

the same catalyst for the reaction these is due to water stability nature of the IL ,

whereas for [Bmim][HSO4] we can see that conversion is lower than that of

[TTDP][HSO4]. Rapid decrease in activity is seen in reusability of the same catalyst

for the reaction. Since moisture or water content for [Bmim][HSO4] is very high, due

water solubility of the IL during the IL. Different solvation might take place in high

content of water for [Bmim][HSO4]. This further reduces its activity by prohibiting it

to further react as an acid catalyst in the reaction.

Figure 5.7: Reusability of IL [TTDP][HSO4] ; [BMIM][HSO4] onconversion of FFA reaction conditions , Oil : Methanol ratio 1:6 ; catalyst loading 2 wt% of oil ; reaction temperature = 60 oC ; reaction time = 2 hr at 1100 rpm.

70

75

80

85

90

95

100

1st Use 2nd Use 3rd Use 4th Use 5th Use

No. of Uses

% C

onve

rsio

nof

FFA

207

5.7 Comparison of Esters with standard Biodiesel values

Esters which were separated by phase separation and further vacuum distilled to

remove methanol, was checked for acid value which shows 0.1 value. This denotes

it’s free of FFA and can be used as substitute for diesel, since its physical properties

are similar to that of diesel. Table 5.2 shows the comparison between the methyl ester

synthesised from acid oil to that of standard biodiesel used. It depicts that methyl ester

from acid oil can be used as biodiesel as alternate to diesel in different blends.

Table 5.2: Fuel Parameters of Acid oil methyl esters as compared with standard

ASTM biodiesel specification

Property Test method

Acid oil Biodiesel in

this work

ASTM standard

for 100% biodiesel

Density, Kg/m3 ASTM D4052 880 870-900

Acid value, mg KOH/ gm ASTM D445 0.32 0.5 max

specific gravity, g/cc ASTM D4052 0.88 0.88-0.90

Flash Point, oC ASTM D93 180 130 min

Water content, wt % ASTM D6304 0.02 0.03 max

Distillation temperature, oC ASTM D86 115 120 max

208

5.8 Conclusion

Ionic Liquid can help to accomplish high final conversions. Nevertheless, when

sulphuric acid were used, even though the final conversion is achieved in shorter time,

the down streaming purification and separation in order to produce FAME that could

be employed in engines are more complicated, less environmental friendly; while

using IL, better separation were achieved and neutralisation of final product were not

required. IL can be reused without affecting the activity of the catalyst conversion of

FFA to FAME. IL are novel environmentally friendly catalyst and also are promising

tools for esterification of oil containing high FFA i.e. not only the anion but also the

cation influences the catalytic properties of IL . From comparison of fuel parameters

of acid oil methyl esters with standard ASTM biodiesel specification Table 2, it can

be concluded, that biodiesel synthesised using Ionic Liquid had ASTM value in

reported range for any fuel to be used as Biodiesel. Hence biodiesel produced using

Acid oil and Ionic Liquid can be probably used in blends with other diesel available.