PREPARATION OF VEGETABLE OIL BASED LUBRICANTS FOR BETTER BIODEGRADABILITY:

Submitted By:

KALYAN MAITY

ROLL NO.:91/OLT/091013

REGISTRATION NO.:0053851 OF 2006-2007

DEPARTMENT OF CHEMICAL TECHNOLOGY

UNIVERSITY OF CALCUTTA

Synthesis of Bio-based Lubricant from oleic acid and N-octanol

Introduction:

Biobased lubricants are an attractive alternative to conventional petrobased lubricants due to

number of advantageous physical properties including: renewablility, biodegradability, high

lubricity and high flash points. Biobased lubricants have not yet replaced petrobased

lubricants due to their higher sensitivity to hydrolysis and oxidative attacks, poor low

temperature behaviour as well as very high price as compared to mineral and synthetic oils.

Actually, there are many petrobased lubricant alternatives available, such as synthetic or

animal fat lubricants, but lubricants derived from vegetable oil have received the most

attention due to a number of their useful physical properties. Firstly, biobased lubricants have

a higher lubricity and thus a much lower coefficient of friction when used when compared to

petrobased lubricants. Secondly, biobased lubricants have high flash points, which makes

then effective in high temperature environments to preclude evaporation or dissipation.

Thirdly, they have relatively stable viscosity indexes, so that they are useful over a large

range of temperatures. Fourthly, biobased lubricants are generally derived from vegetable

oils, and processing can be clean and renewable. Lastly, biobased lubricants are easily

disposed of as they are non-toxic and biodegradable. Conventional petroleum lubricants have

40% less lubricity than biolubricants, because of this biolubricants last four times as long. To

really understand the true value that biolubricants bring to the marketplace one as to look at

the life cycle of the fluids and the potential personnel and environmental liability that

petroleum products create that will no longer impact capital production. Image keeping

capital equipment in the field longer, longer maintenance schedules in between fluid changes,

and improved machine performance, with no human or environmental damage.

But bio-lubricant has some disadvantages too. Biolubricant can only be applied over a

moderate range of temperature as they have high pour point. Biolubricants have got worse

smell and partly compatiable with painting and sealings and it also has more flashing

tendency because of their lower viscosity.

Much research is being done to vegetable oils to improve the physical properties so that

they may compete as an economical alternative with petrobased lubricants. Currently there

are steps being taken towards creating an economy that prefers a biobased lubricant through

policy, but there are complications in the perception of biobased oil and the allocation of

arable land. The world cannot completely switch over to biobased lubricants; it must be a

gradual process requiring the collaboration of government support, agriculture, industry and

research. Most of this research is to improve physical properties of biobased lubricants

through bioengineering and chemical process or with the use of additives. Vegetable oils high

in oleic acid such as rapeseed, soybean, sunflower have become the preferred raw materials

for biobased lubricants. Vegetable oils with high concentration of oleic acids yield stable

lubricants that oxidise much more slowly (Castro, 2006). While conventional soybeans

contain approximately 20 percent Oleic acid, whereas Dupont has bioengineering a soybean

seed with a concentration of Oleic acid over 83 percent. This derived oil was shown to be 30

times more oxidatively stable than conventional soybean oil in hydraulic pump tests

(Honary, 2001). Additionally, the modified soybean seed does not differ nutritionally when

compared to a conventional soybean, but the seed is generally more expensive to purchase,

preventing it's widespread use (Castro, 2006).

Modification of plant oils for biolubricants is done in the following way-

Modification of the carboxylic acid group – esterification or transesterification.

Modification of the fatty acid chain – unsaturated fatty acids are common starting

points for chemical modification; they have been used for a long time in different

modifications for foodstuff chemistry,paints,dyes,hardeners.

Selective hydrogenation – it transforms the easily oxidisable compounds into more

stable compound.

Dimerisation / oligomerisation – it is a modification of the double bonds of

unsaturated fatty acids that engage two or more fatty acid molecules attached to the

residual alkyls.

Epoxidation – epoxidation is one of the most widely used double bond addition

reaction.

Oxidative cleavage – oxidative cleavage of the C=C double bonds of unsaturated

fatty acids produce ozonides which are transformed into mono- and dicarboxylic

acids. Azelaic acid is usually manufactured from oleic acid which is used in high

performance lubricants (Wagner, 2001; Rudnick ,2006).

Metathesis – it is applied usually in the petrochemical industry. This reaction can also

be transferred to plant-based oil chemistry. A reaction with fatty substances generates

often an unselective mixture of products; differentiation exists between self

metathesis (between the same olefins) and co-metathesis (between two different

olefins) (Wagner, 2001).

There are three major aspects of the biobased lubricant economy that must be considered in

order for it to be an effective alternative. Firstly, commercial businesses will choose biobased

lubricants as substitutes for petrobased only if they are cost effective. Secondly, available

arable land to grow raw materials for the lubricant is limited, and the amount of land

dedicated to growing lubricant must be carefully allocated to prevent food shortages. Lastly,

the world does not have the physical, social and political infrastructures that encourage and/or

make feasible a economy that prefers biobased lubricants.

Biobased lubricants can be superior to petrobased lubricants in many applications, but they

are generally about three times as expensive to purchase. This initial acquisition cost may

deter potential buyers, but is offset by reduced energy costs resulting from the high lubricity

of the biobased lubricants. Biobased lubricants lower the coefficient of friction at the pitch

point much more than petrobased lubricants. At higher temperatures, the coefficient of

friction at the pitch point drops dramatically in the presence of biobased lubricants indicating

increasing lubricity. Petrobased lubricants also increase in lubricity as temperature increases,

but they increase at a much less pronounced rate. This high lubricity makes biobased

lubricants an attractive alternative to use in various high temperature applications such as

injection moulding equipment or heated presses (Cliff, 2007). A tremendous demand for

plant based oil is expected in lubricant sector over the next few years, they will become an

important class of base stocks for lubricant formulations.

Methods and Materials:

Materials:

Oleic acid was purchased from Merck Specialities Private Limited, Worli. Mumbai. N-octyl

alcohol from Sisco Research Laboratory Pvt. Ltd., Mumbai. The specific enzyme NS-435

was used which was purchased from Novozyme A/S. Krogshoejvej, Denmark.

Methods:

The enzymatic esterification reaction involves Oleic acid, n-octyl alcohol and a specific

enzyme. Bio lubricant production involves the following reaction sequences.

1. Enzymatic esterification:

375 ml Octanol and 125 ml of oleic acid were taken in a round-bottom flask and then it is

mixed thoroughly under vacuum. Then the enzyme was added by 10% of total weight of the

initial mixture taken. Then the enzymatic reaction is carried out for almost 24 hours and

during the reaction, small quantities of sample was taken after 1 hour to measure the acid

value.

2. Acid value measurement:

Acid value (or "neutralization number" or "acid number" or "acidity") is the mass

of potassium hydroxide (KOH) in milligrams that is required to neutralize one gram

of chemical substance. The acid number is a measure of the amount of carboxylic acid groups

in a chemical compound, such as a fatty acid, or in a mixture of compounds. In a typical

procedure, a known amount of sample dissolved in organic solvent (often isopropanol),

is titrated with a solution of potassium hydroxide with known concentration and

with phenolphthalein as a color indicator.

The acid number is used to quantify the amount of acid present, for example in a sample

of biodiesel. It is the quantity of base, expressed in milligrams of potassium hydroxide that is

required to neutralize the acidic constituents in 1 g of sample.

ACID VALUE = (56.5 * STRENGTH OF NaOH * Volume of NaOH required)/

weight of the sample taken

3. Vacuum distillation:

After the complete esterification process, the mixture is centrifuged and the liquid part is

collected and vacuum distilled to get the pure ester free from Octanol. Distillation is a

method of separating mixtures based on differences in volatilities of components in a boiling

liquid mixture. Distillation is a unit operation, or a physical separation process, and not

a chemical reaction.60-70⁰c temperature is maintained and finally after complete distillation,

Octanol is collected in the distillate vessel and the residue is pure ester which is confirmed by

Thin Layer Chromatography (TLC).

4. Thin Layer Chromatography:

Thin layer chromatography (TLC) is a chromatography technique used to separate

mixtures. Thin layer chromatography is performed on a sheet of glass, plastic, or aluminum

foil, which is coated with a thin layer of adsorbent material, usually silica gel, aluminium

oxide, or cellulose (blotter paper). This layer of adsorbent is known as the stationary phase.

After the sample was applied on the plate, a solvent mixture (Hexane: Diethyl ether –

90:10) was added. After stage-1 (esterification) complete esterification was confirmed by

TLC as well as after vacuum distillation pure ester phase was also confirmed by TLC.

5. Characterisation:

IR analysis: IR of the products was recorded on a spectrophotometer in the range

650–4000 cm−1. A very thin film of the sample was applied to NaCl cells (25mm

i.d × 4mm thickness) for analysis.

Pour point: Pour point is an index of lowest temperature of its utility for low

temperature application.The sample was poured into the test jar to the marked

level. The test jar was closed and a thermometer was placed inside it. The disc,

gasket and inside of the jacket should be dry and clean. The appearance of the oil

was examined time to time. When the sample has ceased to flow, the temperature

is noted.

Viscosity : Viscosity of the sample was measured using Ford cup viscometer.

Flash point: Flash point of a sample is defined as the minimum temperature at

which the sample gives off sufficient vapour to ignite or to flash. Obel Close Cup

method was used with an apparatus of ASTM Pensky-Martens tester and

Thermometer.

The sample cup and the accessories was thoroughly cleaned. And the cup was

filled with the sample upto the mark. The airtight lid was fitted in position. The

thermometer was inserted into its hole in the lid. The pilot flame was adjusted to

the minimum (4 mm index.).The sample was heated slowly. The sample was

stirred continuously. The test flame was continuously applied. The temperature at

which flash occurs is known as flash temperature and it was recorded.

Fire point: The fire point is the minimum temperature at which the sample

vapours will continue to burn instead of just flashing. Here Cleveland Open Cup

method was used. The apparatus included cup thermometer heating plate, test

flame applicator and heater.

The cup was filled by sample upto the indication mark. First, the sample was

heated rapidly and then heated it slowly when the temperature was below the flash

point. And finally when the sample was ignited and continuously burnt for at least

5 seconds. The temperature was recorded as fire point temperature.

Results and Discussions:

1. Acid Value determination:

During esterification process, samples were withdrawn from time to time and their acid

values were measured. Acid value is an indication of the amount of unreacted free fatty acid.

Initially due to the presence of high amount of the reactant oleic acid, it is expected that a

high amount of free fatty acid will be detected in the medium, thus giving a high acid value

reading. In fact that is exactly what we observe here in table 1.

TABLE 1

TIME(hr.) ACID VALUE

0 42.61

1 18.64

2 4.904

3 2.72

24 1.19

FIGURE 1

Here we can see that with increase in time, the acid value decreases rapidly. It clearly

signifies that during the reaction, free fatty acid present in the mixture is gradually esterified.

So esterification reaction is gradually proceeds with time.

2. When the enzymatic esterification reaction is completed, it was centrifuged. The liquid

portion contains the ester part (detected by TLC). The image of the TLC plate is shown

below in figure 2.

FIGURE 2

To remove the excess alcohol, the liquid part is vacuum distilled. Then the remaining part is

solely ester (detected by TLC). The image of the TLC plate is shown below in figure 3.

FIGURE 3

The ester formation is thus confirmed.

3. Viscosity: Viscosity of the ester is 85.5 cP at 21.4⁰C. Good quality lubrication oil must

maintain sufficient viscosity at higher temperatures and it should not be too viscous at lower

temperatures.

4. Flash point: Almost every liquid has a flash point. However, it is a customary practice in

the industry that any chemical with a flash point above 100° C (212° F) is considered non-

flammable. The ester we prepared has a flash point of about 115°C. So it is very safe to use.

5. Fire point: Fire point of a lubricant is generally 8 to 10 percent above its flash point. It is

the temperature at which lubricant combustion will be sustained. To avoid the possibility of

fire, the flash point of oil must be higher than the temperatures likely to be developed in the

rubbing surfaces. In our case we achieved a fire point of 150°C, showing the ester prepared

has good combustion properties.

6. Pour point: Low ambient temperatures affect the flow characteristics of a lubricant.

Dropping below the pour point and the higher viscosity not only restricts oil flow to bearings

and other machine elements, but also translates into high startup torque. As a result, machines

often cannot start or excessive friction causes a complete failure. The low-temperature limit

for starting an oil- lubricated machine is often specified by the pour point of the oil which in

our case is -19°C.

Conclusion:

A tremendous demand for plant -based oils is expected in lubricant sector over the next few

years, they will become an important class of base stocks for lubricant formulations. After

improvement of their disadvantageous characteristics such as higher sensitivity to hydrolysis

and oxidative attacks, poor low temperature behavior and sometimes low VI coefficient they

can be used in almost all automotive and industrial applications. Due to their advantages of

being clean, biodegradable, nontoxic, the first applications for plant-based oils can be

applications for chain saws, railroads, etc., and application like hydraulic fluids in power

equipment, two stroke engines, boat engines etc. In this cases lubricants can be disposed

directly to the environment with little or no risk.

Bio-based oils are important part of the new strategies, policies, and subsidies, which aid to

reduce dependence on mineral oil and other non-renewable sources.

Here I have used Oleic acid and N-Octyl alcohol to produce bio-based lubricant. Produced

biolubricant has shown all the good chracteristics of a well defined lubricant. It can be used

in all industries, automobile survices etc.

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