Lab 4ab (2 Week) - Biodiesel from Seeds_2024 (1)

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Biodiesel from Seeds | Lab 4 Biodiesel from Seeds Introduction Experts believe that the world has surpassed peak oil production and that additional supplies will be harder and harder to extract from the ground. The search for alternative sources of hydrocarbons to use for fuel is an ongoing investment from academic, industrial and government agencies. When Rudolph Diesel first invented the engine named after him in 1893, one of the fuels that he used for combustion was peanut oil. Natural vegetable oils (such as peanut oil) are produced by plants and are usually have the chemical structure of a glycerol with three long chain fatty acids attached through an ester linkage, a triglyceride (see Figure 1 ). These long chains may have the same or different lengths and as well as variations in the number of double bonds contained within the chain. Figure 1. Triacyl glycerides (a.k.a. – Triglyceride) Modern vehicles cannot use vegetable oil like Diesel did; it is much too viscous to move efficiently through carburetors and fuel injectors. We can however use chemistry to convert the triglyceride ester into three molecules of a simple alkyl ester (see Figure 2 ); a chemical with nearly the same energy derived from combustion, but with a much lower viscosity. If the esters we make are the methyl or ethyl esters, this material has come to be known as biodiesel. Figure 2. Transesterification and formation of FAME / BioDiesel We have studied various ways to make esters in class; Fischer esterification, as well as the reaction of an alcohol with an acid chloride or anhydride. In this experiment, we’ll be converting one type of ester (the triglyceride) into another type of ester (a F atty A cid M ethyl E ster or FAME ). This reaction is called a transesterification or an ester exchange. The reaction will require anhydrous methanol and a small amount of a basic catalyst; in this case we’ll use potassium hydroxide. When these two are combined, a small amount of potassium methoxide (CH 3 O - K + ) is produced and it is this that attacks a carbonyl group of the triglyceride.

Biodiesel from Seeds | Lab 4 Overview 1. This is a 2 week experiment 2. Week 1 – You will isolate the triacyl glycerides (Oil) from seeds. 3. Week 2 – You will convert the triacyl glycerides into biodiesel (i.e. – FAME ) Experimental Procedure ( CAUTION : Heptanes are a flammable organic solvent; Methanol is toxic; KOH is caustic and cause burns) Week 1 – Isolation of Triacyl Glycerides 1. Grab a 250 mL beaker and add water to the halfway mark. Place the beaker on a heating mantle and begin heating the water to an almost boil. This water will be used to reflux our seed and heptane mixture later. 2. Weigh out about 10-12 g of the seed of your choice and record it in your notebook. The exact amount is not important however you should determine the mass to two decimal places. 3. Using an electric coffee grinder, grind your seeds to a fine powder. Grind in short 2-3 second bursts, do not over grind your material into a butter. It is acceptable if the ground material sticks together somewhat, however a “peanut butter” consistency will be difficult to extract. 4. Add all of your ground material to a 100 mL round bottom flask and support it with a clamp. Add a stir bar to the round bottom flask. 5. Fit the flask with a reflux condenser. Turn on a gentle trickle of water to the condenser. 6. Add 50 mL of heptanes, wipe the outside of the flask to ensure there are no heptanes spilled on it, and submerge the round bottom flask in the water bath. Once the heptane has begun to reflux, continue heating for 1 hour. 7. Turn off the heat and with the condenser still in place, raise the flask & condenser, 8. Setup a Buchner filtration apparatus - 1) wet the filter paper with a mL or two of heptanes, 2) turn on the water to engage the vacuum 3) pour the contents of your round bottom into the Buchner while trying to keep as much seed residue in the round bottom flask as possible. 9. Place the ground seed residue from your filtration into the regular trash. 10. Add the filtrate to a pre-weighed round bottom flask. Using the rotary evaporator, concentrate the liquid to an oil. 11. Record the new mass of your flask with the oil.

Biodiesel from Seeds | Lab 4 Week 2 - Transesterification 1. Heat a large beaker that is nearly full with water on your hot plate. Adjust the heat so the water is between 50-60 o C. Temperatures above 60 o C are super bad and you should avoid them at all costs! It may take a few minutes to reach a steady temperature. 2. Transfer ~5 grams of oil to a dry plastic 10 mL Corning tube. Make certain you have recorded the mass of oil to 2 decimal places. 3. Calculate how much of the KOH/methanol solution you will need by multiplying the mass of oil you placed in the test tube by 0.4. If you have 2 g of oil, you would use 2 x 0.40 = 0.80 mL; similarly, 5 g of oil would require 2.0 mL of KOH/methanol solution. 4. Place the test tube containing the oil into the warm water bath for 5 minutes, then add the amount of KOH/methanol solution that you calculated in step 3. Mix the solution well by rapidly pulling it into and pushing it out of a disposable pipette a few times. Do this once a minute for the first 5 minutes then once every 10 minutes for the next 30 minutes. a. *During this down-time*, please try to go ahead and perform a viscosity measurement (procedure is at the end of this section) on your starting material oil. b. *During this down-time*, please try to go ahead and perform a calorimetry measurement (procedure is at the end of this section) on a sample of commercial biodiesel. 5. Once you reach 45 minutes of reaction, mix once more with your pipette and remove the test tube from the heat. Allow to cool for ~5 minutes 6. Find another group that has finished step 5 and find me. We’ll walk over to the Nursing Chem Lab (Hobbs 320) and use the centrifuge there as a group. Don’t use it without me . Centrifuge your samples for 5 minutes on max setting. 7. Walk back over to the OChem Lab. Remove samples of biodiesel (top layer) for viscosity and calorimetry measurements. AVOID mixing the two layers and AVOID the bottom layer at all costs! It is full of glycerol and soap side-products. Viscosity Measurements 1. Take a short disposable glass pipette and measure the distance from the bottom tip of the pipette to near the top of the pipette where you should see a horizontal indentation. 2. Gently plug the bottom of the pipette with a gloved finger, and add your oil up to the mark that you identified near the top of the pipette. 3. Remove your finger, and measure how long it takes the meniscus to travel from the top mark to the bottom mark.

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