1. INTRODUCTION:

Biodiesel refers to a vegetable oil- or animal fat-based diesel fuel consisting of long-chain alkyl (methyl, propyl or ethyl) esters. Biodiesel is typically made by chemically reacting lipids (e.g., vegetable oil, animal fat (tallow)) with an alcohol.

Biodiesel is a clean burning recycled fuel made from vegetable oils. It is chemically called Free Fatty Acid Alkyl Ester. Even though "diesel" is part of its name, there is no petroleum or other fossil fuels in biodiesel. Biodiesel is 100% vegetable oil based. Biodiesel is made up of almost 10% oxygen, making it a naturally "oxygenated" fuel. It is obtained by reaction of vegetable oil with alcohol in presence of catalyst.

Burning fuels derived from vegetable oils does not contribute any additional CO₂ to the atmosphere, as the carbon released is the same as the carbon absorbed by the plants as they grow. Using vegetable oils is therefore beneficial to the environment, economy and to the atmosphere¹.

Different raw materials available for producing Biodiesel are Jatropha oil, Pongamia oil, Rapeseed Oil, Mahuva oil, Olive oil, Rice Bran oil, Linseed oil, Soya bean oil, Palm oil, Cotton Seed oil, Sunflower oil, Beef Tallow, Lard, and Guang-Pi. The use of particular raw material depends upon the availability, price and policy.

Biodiesel is meant to be used in standard diesel engines and is thus distinct from the vegetable and waste oils used to fuel converted diesel engines. Biodiesel can be used alone, or blended with petro diesel. Biodiesel can also be used as a low carbon alternative to heating oil

Blends of less than 20% biodiesel can be used in diesel equipment with no, or only minor modifications, although certain manufacturers do not extend warranty coverage if equipment is damaged by these blends. The B6 to B20 blends are covered by the ASTM D7467 specification. Biodiesel can also be used in its pure form (B100), but may require certain engine modifications to avoid maintenance and performance problems. Blending B100 with petroleum diesel may be accomplished by:

· Mixing in tanks at manufacturing point prior to delivery to tanker truck

· Splash mixing in the tanker truck (adding specific percentages of Biodiesel and petroleum diesel)

· In-line mixing, two components arrive at tanker truck simultaneously.

· Metered pump mixing, petroleum diesel and Biodiesel meters are set to X total volume, transfer pump pulls from two points and mix is complete on leaving pump.

1.1. Properties of Biodiesel:

Biodiesel has better lubricating properties and much higher cetane ratings than today's lower sulfur diesel fuels. Biodiesel addition reduces fuel system wear, and in low levels in high pressure systems increases the life of the fuel injection equipment that relies on the fuel for its lubrication. Depending on the engine, this might include high pressure injection pumps, pump injectors (also called unit injectors) and fuel injectors².

· Older diesel Mercedes are popular for running on biodiesel.

· The calorific value of biodiesel is about 37.27 MJ/L. This is 9% lower than regular Number 2 petro diesel. A variation in biodiesel energy density is more dependent on the feedstock used than the production process. Still these variations are less than for petro diesel. It has been claimed biodiesel gives better lubricity and more complete combustion thus increasing the engine energy output and partially compensating for the higher energy density of petro diesel.

· Biodiesel is a liquid which varies in color between golden and dark brown depending on the production feedstock. It is immiscible with water, has a high boiling point and low vapor pressure. The flash point of biodiesel (>130 °C, >266 °F)^[32] is significantly higher than that of petroleum diesel (64 °C, 147 °F) or gasoline (−45 °C, -52 °F). Biodiesel has a density of ~ 0.88 g/cm³, higher than petro diesel (~ 0.85 g/cm³).

· Biodiesel has virtually no sulfur content, and it is often used as an additive to Ultra-Low Sulphur Diesel (ULSD) fuel to aid with lubrication, as the sulfur compounds in petro diesel provide much of the lubricity.

1.2. Material compatibility in Biodiesel:

· Plastics: High density polyethylene (HDPE) is compatible but polyvinyl chloride (PVC) is slowly degraded. Polystyrenes are dissolved on contact with biodiesel.

· Metals: Biodiesel has an effect on copper-based materials (e.g. brass), and it also affects zinc, tin, lead, and cast iron. Stainless steels (316 and 304) and aluminum are unaffected.

· Rubber: Biodiesel also affects types of natural rubbers found in some older engine components. Studies have also found that fluorinated elastomers (FKM) cured with peroxide and base-metal oxides can be degraded when biodiesel loses its stability caused by oxidation. Commonly used synthetic rubbers FKM- GBL-S and FKM- GF-S found in modern vehicles were found to handle biodiesel in all conditions³.

1.3. Low temperature gelling:

When biodiesel is cooled below a certain point, some of the molecules aggregate and form crystal. The fuel starts to appear cloudy once the crystals become larger than one quarter of the wavelengths of visible light this is the cloud point (CP). As the fuel is cooled further these crystals become larger. The lowest temperature at which fuel can pass through a 45 micrometer filter is the cold filter plugging point (CFPP). As biodiesel is cooled further it will gel and then solidify. Within Europe, there are differences in the CFPP requirements between countries. This is reflected in the different national standards of those countries. The temperature, at which pure (B100) biodiesel starts to gel, varies significantly and depends upon the mix of esters and therefore the feedstock oil used to produce the biodiesel. For example, biodiesel produced from low erucic acid varieties of canola seed (RME) starts to gel at approximately −10 °C (14 °F). Biodiesel produced from tallow tends to gel at around +16 °C (61 °F). There are a number of commercially available additives that will significantly lower the pour point and cold filter plugging point of pure biodiesel. Winter operation is also possible by blending biodiesel with other fuel oils including #2 low sulfur diesel fuel and #1 diesel / kerosene⁴.

Another approach to facilitate the use of biodiesel in cold conditions is by employing a second fuel tank for biodiesel in addition to the standard diesel fuel tank. The second fuel tank can be insulated and a heating coil using engine coolant is run through the tank. The fuel tanks can be switched over when the fuel is sufficiently warm. A similar method can be used to operate diesel vehicles using straight vegetable oil.

2. EXPERIMENTAL WORK:

2.1. Production of neem oil using solvent extraction:

The most used method for extracting neem oil is solvent extraction. It uses a solvent, preferably a petroleum solvent/alcohol solvent for processing oil. It ensures maximum extraction of oil. Neem seeds have water content of 7.8% and oil content of 49.58%. Prior to use, the Neem seeds were repeatedly washed to remove dirt and other impurities material, and subsequently dried in oven at 50°C until it reached constant moisture content. Then, Neem seeds were ground to get fine particle size.

Neem seeds were extracted using two solvents (n-hexane and methanol) for 3 hours with ratio Neem seed powder weight to solvent volume of 1:5. Filtrate was heated and evaporated to obtain solvent-free oil. Then the oil was weighed to calculate the concentration of oil in the solution⁵.

2.2. Processing of Biodiesel from non edible oil (Neem Oil):

Transesterification (alcoholysis) is the chemical reaction between triglycerides and alcohol in the presence of catalyst to produce mono-esters. The long and branched chain triglyceride molecules are transformed to mono-esters and glycerin. Transesterification process consists of a sequence of three consecutive reversible reactions. That is, conversion of triglycerides to diglycerides, followed by the conversion of diglycerides to monoglycerides. The glycerides are converted into glycerol and yielding one ester molecule in each step. The properties of these esters are comparable to that of diesel. The overall transesterification reaction can be represented by the following reaction scheme⁶.

Stichometrically, three moles of alcohol are required for each mole of triglyceride, but in practice a higher molar ratio is employed in order to displace the equilibrium for getting greater ester production. Though esters are the desired products of the transesterification reactions, glycerin recovery also is important due to its numerous applications in different industrial processes. Commonly used short chain alcohols are methanol, ethanol, propanol and butanol. The yield of esterification is independent of the type of alcohol used. Therefore, the eventual selection of one of these three alcohols will be based on cost and performance considerations. The methanol is used commercially because of its low price. Alkaline hydroxides are the most effective transesterification catalysts as compared to acid catalysts. Potassium hydroxide and sodium hydroxide are the commonly used alkaline catalysts. Alkaline catalyzed transesterification of vegetable oils is possible only if the acid value of oil is less than 4. Higher percentage of FFA in the oil reduces the yield of the esterification process.

Free fatty acid (FFA) percentage in neem oil is very high. There are many methods to find out the free fatty acid percentage content in oil. Simple titration with the KOH is a simple method.

2.3.1. Titration:

In order to determine the percent of FFA in the oil, a process called titration is used. The vegetable oil is first mixed with methanol. Next, a mixture of Sodium Hydroxide (NaOH) and water is added until all of the FFA has been reacted. This is confirmed by checking the pH of the mixture. A pH of about 9 signifies all of the FFA has been reacted. Virgin vegetable oil from the same feed stock will usually titrate at approximately the same level, so checking every batch is not necessary. Waste Vegetable oil feed stocks will vary greatly. Every batch must be titrated⁷.

The NaOH water mixture can be prepared by adding 1 gram of NaOH to 1000ml distilled water. The mixture will be more accurate if it is first made as a 1% solution (10grams NaOH to 1000ml water). Next, add 100mL of the 1% solution to 900ml of distilled water. This will make a 0.1% NaOH solution.

The process for titration is as follows:

1) Place 10mL of Methanol in a 50ml flask.

2) Add 1mL of vegetable oil (mix the oil thoroughly prior to drawing 1ml).

3) Mix the oil with the Methanol using the squirting action of the dropper.

4) Add the ph indicator solution (usually 3 drops, check instructions).

5) Place 15ml 0.1% NaOH (known as titrant) solution in a 50ml flask.

6) Draw exactly 5ml of the NaOH solution into the graduated pipette.

7) Add 0.1% NaOH to the methanol/oil mixture one drop at a time. Mix the solution using a swirling action between the drops. Using the eyedropper to mix the solution may help if the oil forms drops in the bottom of the flask.

8) Continue to add 0.1% NaOH until a pH of 9 (blue-green color) is reached. This may require more than 5ml. Refill the pipette and continue. Note the amount in ml that was required.

9) Look up the corresponding amount of NaOH required for the entire batch in Table 3. Multiply the amount by the number of gallons of oil to obtain the required amounts.

Table 2.1. Titration information

Titration (ml)	% FFA	NaOH (gm) per gallon
0	0	13.25
0.5	0.3578222	15.15
1	0.7156445	17.025
1.5	1.0734667	18.925
2	1.431289	20.825
2.5	1.7891112	22.7
3	2.1469334	24.6
3.5	2.5047557	26.5
4	2.8625779	28.3875
4.5	3.2204002	30.28
5	3.5782224	32.1725

2.3.2. Acid number calculation for the sample:

Acid value = 56.1×N×V/M

Where,

V is the number of ml of KOH,

N is the normality of KOH,

M is the mass (in g) of sample.

Acid number for neem oil is 52.generally FFA value is half of the acid value so percentage of free fatty acid (FFA) in neem oil is 26% it is very high so we cannot use directly alkaline esterification before that we do acid pretreatment method ‘acid– base’ process Acid-pretreatment followed by main base-transesterification reaction; using methanol as reagent and H₂SO4 and KOH as catalysts for acid and base reactions, respectively, was followed to produce biodiesel from crude neem oil.

2.3.3. Esterification procedure:

Methodology

The objective of this study is to develop a process for producing biodiesel from non edible neem oil. The process consists of two steps namely, acid esterification and alkaline esterification.

(a) Acid Esterification: The firsts step reduces the FFA value of crude neem oil to about 2% using acid catalyst

(b) Alkaline Esterification: After removing the impurities of the product of first step, it is transesterified to mono-esters of fatty acids using alkaline catalyst. The parameters affecting the process such as alcohol to oil molar ratio, catalyst amount, reaction temperature and duration are analyzed.

Esterification Setup:

A round bottom flask is used as laboratory scale reactor for these experimental purposes. A hot plate with magnetic stirrer arrangement is used for heating the mixture in the flask. The mixture is stirred at the same speed for all test runs. The temperature range of 50– 60 °C is maintained during this experiment.

Acid Esterification:

One liter of crude neem oil requires 250 ml of methanol for the acid esterification process. The neem oil is poured into the flask and heated to about 50 °C. The methanol is added with the preheated neem oil and stirred for a few minutes. 1% of sulphuric acid is also added with the mixture. Heating and stirring is continued for 30 min at atmospheric pressure. On completion of this reaction, the product is poured into a separating funnel for separating the excess alcohol. The excess alcohol, with sulphuric acid and impurities moves to the top surface and is removed. The lower layer is separated for further processing (alkaline esterification).

Effect of reaction temperature:

At room temperature the conversion efficiency is noted to be very low, even after 2 hrs of stirring. With increase in temperature the conversion takes place at a faster rate. The optimum temperature for this reaction is found to be in the range of 50±5 °C. At higher reaction temperatures, there is a chance of loss of methanol and increase in darkness of the product. High reaction temperature increase the production cost of biodiesel also.

Alkaline Esterification:

Alkaline catalyzed esterification process uses the experimental setup of acid catalyzed pretreatment process. The products of first step are preheated to the required reaction temperature of 50±5 °C in the flask. Meanwhile, 5 gm of KOH is dissolved in 250 ml methanol and is poured into the flask. The mixture is heated and stirred for 30 min. The reaction is stopped, and the products are allowed to separate into two layers. Glycerin which is heavier deposits at the bottom and the esterified neem oil is obtained at the top portion.

Effect of reaction temperature:

The maximum yield of ester is obtained at the temperatures of 50±5 °C. The decrease in yield is observed when the reaction temperature goes above 55 °C. The reaction temperatures greater than 60 °C should be avoided, in the case of neem oil, because they tend to accelerate saponification of the glycerides by the alkaline catalyst before completion of the alcoholysis⁸.

3. RESULTS:

The final product that obtained is analyzed in order to determine several properties like flash point, fire point, density, calorific value, viscosity etc. The results are tabulated and compared as follows:

Table 3.1. Comparison of properties of Biodiesel, Diesel, Crude neem oil

Property	Diesel	Crude neem oil	Neem Biodiesel
Flash point (⁰C)	55	214	120
Fire point (⁰C)	62	222	128
Density (kg/m³)	822	918	868
Calorific value (MJ/kg⁰K)	42.2	34.1	35.2
Viscosity at 40⁰C (mm²/sec)	2.2	4.4	4.3

The crude neem oil, however, was found to have much higher values of fuel properties especially viscosity, way above any of these standard limits thus restricting its direct use as a fuel for diesel engines.

4. CONCLUSION:

Based on the results of this study, the following specific conclusions were drawn:

1. A two-step transesterification process is developed to convert the high FFA Non edible oils to its esters. The first step (acid catalyzed transesterification) reduces the FFA content of the oil to less than 2%. The alkaline catalyst transesterification process converts the products of the first step to its monoesters and glycerol.

2. Factors effecting the biodiesel production (reaction temperature, reaction rate & catalyst) are analyzed.

3. The fuel properties of neem biodiesel were within the limits and comparable with the conventional diesel. Except calorific value, all other fuel properties of neem biodiesel were found to be higher as compared to diesel⁹.

Ongoing alarming changes in the environment and global warming are causing very dangerous effects in the universe. This may be due to various human activities. One of such activities is extensive usage of fossil fuels. It is known that fossil fuels are causing not only pollution but also remaining in the environment without any degradation. Therefore, an attempt is made to find out and produce at least a small alternative to the fossil fuels. With low process cost, biodiesel is produced using catalysts. The yields and properties of the biodiesel is very satisfactory. The conversion increases with increasing time of heating. So, in future by optimizing cost of production and other variables biodiesel can be better alternative for diesel especially keeping environmental effects in view bearing cost. Since, demand for edible oils is more in our country the production of biodiesel using non-edible oil neem seeds will be definitely more effective¹⁰.

5. REFERENCES:

1. A.S. Ramadhas, S. Jayaraj and C. Muraleedharan, Use of vegetable oils as I.C. engine fuels—a review, Renewable Energy 29 (2004), pp. 727–742.

2. A. Srivastava and R. Prasad, Triglycerides-based diesel fuels, Renew Sust Energ Rev 4 (2000), pp. 111–133.

3. H. Raheman and A.G. Phadatare, Diesel engine emissions and performance from blends of karanja methyl ester and diesel, J Biomass Bioenerg 27 (2004), pp. 393–397.

4. A.S. Ramadhas, C. Muraleedharan and S. Jayaraj, Performance and emission evaluation of a diesel engine fueled with methyl esters of rubber seed oil, J Renew Energ 30 (2005), pp. 1700–1789.

5. Puri H.S. 1999. Neem-The Divine Tree. Harwood Academic Publishers, Amsterdam.

6. Ragasa C.Y., Nacpil Z.D., Natividad G.M., Tada M., Coll J.C. and Rideout J.A. 1997. Tetranortriterpenoids from Azadirachta Indica. Journal of Phytochemistry. 46: 555-558.

7. Johnson S., Morgan E.D. and Peiris C.N. 1996. Development of the Major Triterpenoids and Oil in the Fruit and Seeds of Neem (Azadirachta indica). Journal of Annals Botany. 78: 383-388.

8. Mongkholkhajornsilp D., Douglas S., Douglas P.L., Elkamel A., Teppaitoon W. and Pongamphai S. 2004. Supercritical CO2 Extraction of Nimbin from Neem Seeds-A Modeling Study. Journal of Food Engineering. 71: 331-340.

9. P. Bangaraiah and P. Ashok Kumar, Bioethanol as an alternative energy resource, International Journal of Pharma and Biosciences, 5(1), 2014, 1005 – 1009.

10. P. Bangaraiah, P. Ashok Kumar and V. Madhusudhanrao, Biological fuel cells, Research Journal of Pharmaceutical, Biological and Chemical Sciences, 5(3), 2014, 1769 – 1778.

Received on 07.09.2016 Modified on 28.09.2016

Research J. Pharm. and Tech 2016; 9(10):1663-1667.

DOI: 10.5958/0974-360X.2016.00335.8