Biodiesel Lab Experiment - BTC
Biodiesel Lab Experiment
Biodiesel production from different feedstocks
In lab groups of 4 – 5, prepare biodiesel from different feedstocks including Canola vegetable oil, Crisco, and spent fryer grease. Each group will be assigned one feedstock. We will use methanol as the alcohol and sodium hydroxide as the catalyst. We will do the reaction in two steps, with 80% of the methanol/catalyst added in the first step.
Procedure:
1. Weigh out 100 grams of the oil or fat into a 250 milliliter flask.
2. Weigh out 23 grams of methanol in a 125 milliliter flask.
3. Weigh out 0.4 grams of sodium hydroxide and add it to the methanol.
4. Add a stirring bar and dissolve the sodium hydroxide. Some heat may help the process.
5. After the sodium hydroxide has dissolved, add about 80% of the alcohol/catalyst solution (with stirring bar) to the 250 ml flask containing the oil
6. Place the 250 ml flask cont aining the oil, methanol/catalyst mixture, and stirring bar on the hot plate.
7. Place a watch glass with ice cube or tin foil over the top of the flask to contain and condense the methanol vapors.
8. Turn on the hot plate and stirrer and raise the temperature to 60 – 65 deg C.
9. Maintain the temperature for 45 minutes.
10. Transfer the mixture to a separatory funnel and allow it to settle for 15 minutes.
11. Remove the glycerin (lower) layer.
12. Return the upper layer to the 250 ml flask and add the remaining 20% of the alcohol/catalyst mixture. Stir at 60 – 65 deg C for 45 minutes.
13. Transfer the mixture to a separatory funnel and allow it to settle for 15 minutes.
14. Remove the glycerin (lower) layer – if any.
15. The upper layer should be biodiesel and can be purified by washing with warm water at a volume equal to the volume of biodiesel. Gently wash the biodiesel and let the water settle out for about 10 minutes so you can remove it from the bottom of the separatory funnel.
16. The biodiesel should be clear. If it is cloudy, you can heat it to 60 – 80 deg C to remove the water.
Laboratory safety
Everyone must wear safety glasses or goggles while working in the laboratory.
Lab coats or aprons will be provided to those involved with pouring or mixing chemicals.
If a fire occurs, leave the building immediately.
No smoking in BTC buildings.
Biodiesel Lab Experiment
Measuring free fatty acid of the feedstock (American Oil Chemist’s Society)
In lab groups of 4 – 5, measure free fatty acids from different feedstocks including Canola vegetable oil, Crisco and spent fryer grease. Each group will be assigned one feedstock.
Procedure
1. Prepare two 250 ml beakers by adding 75 ml of solvent to each. The solvent contains 50% isopropyl alcohol/50% toluene (or just isopropanol).
2. Add 5 grams of the weighed sample to one of the beakers. The beaker without the sample is called the blank.
3. Add 2 ml of phenolphthalein indicator to both beakers (or use litmus paper).
4. Titrate both beaker with 0.1 N potassium hydroxide (or other base) to the first permanent pink color in each.
5. Calculate the acid value from: Acid value = (ml of base to neutralize sample – ml of base for blank) x normality of base (0.1) x molecular weight of base/sample weight
a. The molecular weight of sodium hydroxide is 40.
b. The molecular weight of potassium hydroxide is 56.1
The acid value is the mg of base needed to neutralize a gram of the sample. The percentage of free fatty acids can be determined by 0.1 (100/1000) times the acid number times the ratio of the molecular weight of the fatty acid divided by the molecular weight of the base. For potassium hydroxide (mw of 56.1) and a fatty acid molecular weight of 280 (typical of soybean oil and similar oils) the formula is
% FFA = acid value / 2
The amount of catalyst you will need to add will equal the amount necessary to catalyze the reaction in addition to that necessary to esterify the FFA. The amount necessary to catalyze the reaction varies from 0.2 – 0.5% based upon the weight of oil. Total amounts of base range from 0.2 – 2% for free fatty acid concentrations less than 2%.
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