laboratory preparation of biodiesel
- 1. Objective: - To synthesize biodiesel Introduction:- Biodiesel is a cleaner burning renewable alternative to diesel fuel that is made from biological sources ; Namely vegetable oil or animal fats (triglycerides). It is mixable with diesel, stable in mixture, and can be burned in an unmodified diesel engine at any concentration. Biodiesel is made through a transesterification reaction. Transesterification is the chemical process through which one ester (a chemical having the general structure R’COOR’’) is changed into another. * Reactants:- vegetable oil or animal fats (an ester compound) methanol (an alcohol) Vegetable oil or animal fats is a triglyceride (or triacylglycerol), which is essentially a glycerine (or glycerol) molecule connected via ester bonds to three fatty acid molecules * Reaction:- During the reaction, the fatty acids of the triglyceride molecule are Cleaved and attach to the alkyl group (the part made of carbon and hydrogen) of the alcohol to form fatty acid alkyl esters (in our case, fatty acid methyl esters or FAME), which are biodiesel. In order to get the transesterification of vegetable oil going, we use a base catalyst (a substance that increases the rate of a chemical reaction but is not altered by the reaction). We can use potassium hydroxide (KOH) or sodium hydroxide as our base catalyst. This reaction is diagrammed below... When alkyl groups of fat are different like R1, R2, R3.....
- 2. When all alkyle groups are same...(as like given below only R alkyle group) The product is considered crude because it is contaminated with methanol, basic salts, and glycerine. All of these contaminants are water soluble. Therefore, we remove them using a water wash. The washing introduces water to the biodiesel, which decreases fuel quality and must be removed. We can bubble air through wet biodiesel to dry it. This process forces the evaporation or settling of water molecules remaining in the fuel and leaves you with a finished biodiesel fuel. Chemicals required Vegetable oil 60 mL Base (NaOH) (≈0 .5 g) Methanol ( 14 mL) Apparatus required: 50 mL Erlenmeyer flask stir bar 200 ml beaker 125 ml separatory funnel with ring stand 50 mL graduated cylinder Spray bottle with distilled water
- 3. Procedure:- 1. First of all we will calculate the free fatty acid amount in the bio mass sample by titration. 2. Take a 50 mL Erlenmeyer flask with a stir bar and add 14 ml of pure methanol. 3. Place the flask on a stir plate and set speed at a rate where it doesn’t splash but stirs vigorously. 4. Slowly add 0.50 g of NaOH. Do not go over this mass of the NaOH; add carefully. 5. Observe the NaOH being completely dissolved. Once this happens, sodium methoxide is formed, a very strong and dangerous base. 6. While the sodium methoxide is being formed, place 60 ml of pure vegetable oil in a 200 ml beaker on a hot plate and warm to 50°C. Then place it on a stir plate with a stir bar under medium agitation. 7. After step 4 is complete, SLOWLY the sodium methoxide add it to the warm vegetable oil. Make sure no residual NaOH gets into the oil. The solution will be cloudy. 8. Stir the reaction mixture for 20 minutes 9. We get the solution of biodiesel and Glycerol. Now separation of biodiesel and glycerol is done on the basis of difference in the density... 10. Transfer the solution to a 125 ml separatory funnel. Allow the solution to settle for 20 minutes using a ring stand; the glycerol layer will form on the bottom. If you do not see two layers, start over being sure to add no more than 0.50 g NaOH. 11. Once glycerol has stopped forming, drain the glycerol into a small graduated cylinder using the stopcock. Record the volume of glycerol. 12. Drain the biodiesel layer from the separatory funnel and measure the volume. 13. To get more pure biodiesel wash the biodiesel and allow the water and oil to separate .And when two different layers are obtained take out water layer. “ The whole procedure can be understood easily with the help of the fig. Below”
- 4. Thank you.…