Why do biodiesel and glycerol separate

That's the National Biodiesel Board website, lots of good information there. It won't really tell you as much how to make it, but hopefully, this will be one of the more informative sites that you'll actually be able to see somebody make one, make a batch. As our oil is heating up, we have to mix up our methanol potassium hydroxide mixture. So safety is paramount with the use of methanol or the strong caustic lye potassium hydroxide. Methanol can cause blindness or death, and it can be absorbed through the skin.

And the potassium hydroxide will burn your skin if it gets on you. So here's what we're going to do. We're going to take our methanol and we're going to pour this into a container. Face shields are good, too. We're going to use milliliters of the methanol.

Our next ingredient is our potassium hydroxide. That's our lye. Now, we have to do a quick calculation on how much of this we need to mix with our methanol in order for the reaction to take place. I've got a nice spreadsheet that I like to use. It's the Biodiesel-o-matic. You can usually find it online from different biodiesel websites. I'm going to pull that up. We want to use 7 grams of potassium hydroxide per each liter of veggie oil. So you take 7 divided by 0. And that gives you 6.

So we're going to use our scale. We're going to zero the container. And then we're going to put 6. Make sure you have your gloves on. That's our 6. Close this immediately. Keep it double bagged. Now, you're going to take your 6.

Again, you want to stir this. It's not necessary to heat it, though. Just stir. And stir this until at least the potassium hydroxide is completely dissolved into the methanol. You don't want to see any chunks of white potassium hydroxide flakes. All right. Our potassium hydroxide is fully mixed into our methanol. We want to remove the stir bar.

And then we're just going to slowly pour this into our oil as it's being stirred. Again, you don't have to have fancy equipment. Just pour it in as you're stirring it manually. But the key is to do it slowly. Glycerol is formed and has to be separated from the biodiesel. Both glycerol and biodiesel need to have alcohol removed and recycled in the process.

Water is added to both the biodiesel and glycerol to remove unwanted side products, particularly glycerol, that may remain in the biodiesel. After 15 minutes place the tube in a rack and allow the contents to settle. If possible allow the contents to settle overnight. Methanol is toxic when inhaled, ingested or absorbed through the skin.

Sodium hydroxide is corrosive, it is recommended that students wear gloves. If sodium hydroxide in the "methanol solution" is splashed on your skin, rinse immediately with copious amounts of running water. Sodium methanolate sodium methoxide reacts violently with water. Keep away from moisture.

If sodium methanolate sodium methoxide in the "methanol solution" is splashed on your skin, rinse immediately with copious amounts of running water. Decant gently pour off the top layer containing the biodiesel into a small mL clean, dry, conical Erlenmeyer flask. Label this flask "top layer: biodiesel". Tip the vial containing the remaining mixture on its side and position a pipette in the bottom of the mixture.

Carefully remove this dense bottom layer only using the pipette, and place this into a clean, dry test tube. If, on standing, the solution in the test tube separates into 2 layers, use a pasteur pipette to remove and discard the top layer. The top yellow layer has a volume about 10 times that of the bottom dark red layer. Play the game now! Confirm that the top layer, now contained in the conical Erlenmeyer flask, is biodiesel and that the bottom layer, now contained in a test tube, is the glycerol by determining their relative solubility in water.

Place 5 mL of water in each of two test tubes. Label one test tube "top layer" and label the other "bottom layer". To the water in the test tube labelled "top layer" use a pasteur pipette to add a few drops of solution from the conical Erlenmeyer flask. Swirl gently. To the water in the test tube labelled "bottom layer" use a pasteur pipette to add a few drops of solution from the test tube.

Substance Observations "top layer" immiscible with water "bottom layer" miscible with water. Glycerol contains 3 polar OH functional groups which allow it to hydrogen bond with water molecules. Glycerol is therefore miscible with water that is, it is soluble in water in all proportions.

Biodiesel, a mixture of methyl esters of long chain fatty acids, is effectively non-polar so it will not dissolve in water, that is, it is not miscible with water. Another way to say this is that it is immiscible with water. Take the test now! Confirm that the top layer, now contained in the conical Erlenmeyer flask, is more likely to be biodiesel than vegetable oil by measuring their relative densities.

Label one clean, dry, 10 mL measuring cylinder "top layer" and another one "vegetable oil". Pipette 5. Weigh and record the mass. The "top layer" biodiesel should be less dense than the vegetable oil used to make the biodiesel. Compare the energy released by combustion of the biodiesel produced above with that released by the combustion of conventional diesel.

Although we will be using very small amounts of diesel and biodiesel, the procedure is very similar to that for determining the heat of combustion of alcohols. Note that instead of using a spirit burner we will be using an evaporating basin and wick. Add 1 mL of the prepared biodiesel to the evaporating basin and record its total mass.

Position the tissue in the evaporating basin so that some of the tissue is touching the biodiesel in the bottom of the basin. The methyl route was performed under the same conditions as the ethyl route, and the quantities used were g of soy oil, g of methanol and 5.

After the first reaction step was complete, the mixture was transferred to a separatory funnel in which the separation of the two phases occurred spontaneously without the addition of water.

The glycerol was removed, and the second step was performed after the addition of an additional 39 g of methanol and 1. To evaluate the conversion of triacylglycerols TAGs to mono alkyl esters, 1 H NMR spectra were obtained after the first step, after the second step and after the final purification of the biodiesel with the cationic resin. The fatty acid compositions of the soy oil used for the experiments and the produced biodiesels were determined using GC.

For the oil sample, chromatographic analysis was performed as previously described using the method of saponification and esterification of fatty acids developed by Metcalfeet et al. The identification of the esters was performed according to the retention times of the previously analyzed standard substances. The quantitation was obtained through the normalization of the area of each chromatographic peak. The acid number was determined following the method proposed by Aricetti et al.

Slightly less than 5 mL of the sample was added to a calibrated 5 mL volumetric flask of known weight. The flask with the samples was thermostated in a water bath at Then, the flask was brought to volume at this temperature. The flask was dried with paper towels and weighed.

The alcohols used in the transesterification reaction methanol and ethanol in the present study act not only as reagents but also as surfactants because they are soluble in glycerol polar phase and in biodiesel non-polar phase. The carbon chain of the alcohol molecule is responsible for its solubility in biodiesel, whereas the hydroxyl group exhibits affinity for the glycerol.

When the interfacial tension between two liquids is reduced to a sufficiently low value due to the presence of a surfactant, the emulsification of these liquids occurs. Ethanol contains an additional CH 2 group in its molecule compared with methanol.

Therefore, ethanol is a more efficient surfactant and causes the emulsification of the glycerol-biodiesel mixture, indicating that separation of the phases will be more difficult. This situation presents a problem in the production of ethyl biodiesel because it results in a long wait for the decantation process and it provokes the retention of glycerol in the biodiesel, indicating that the concentrations of this byproduct can reach higher concentrations than that allowed by regulatory agencies.

The 1 H NMR spectra of the soy oil and the reaction mixtures after the transesterification steps, after separation of the phases, and after drying and purification with the cationic resin are presented in Figure 1 for ethyl and methyl biodiesels. The conversion of the triacylglycerides to mono alkyl esters is clearly observed in the 1 H NMR spectra by the disappearance of the double duplets at 4.

The conversion is also noted by the appearance of the singlet at 3. The signal at 3. In the spectra of the methyl biodiesel, the signal at 3. Purification through the resin removes the eventual alcohol molecules that are yet present in the biodiesel and removes substantial quantities of residual water, as observed by Karl Fischer analyses and by the absence of the signal at 1. The obtained conversion percentages of the transesterification reactions are presented in Table 1.

The fatty acid compositions of the soy oil and the produced biodiesels are shown in Table 2. Table 3 shows the obtained values for certain physical and chemical properties of the synthesized biodiesels. Importantly, when water was added for the separation of the glycerol and biodiesel phases, no soap formation was observed, the formation of which would result in a lower yield and a lower quality of the obtained product.

Nova , 30, The fatty acid compositions of the soy oil and the formed biodiesel are similar Table 2 , indicating the non-occurrence of side reactions as, for example, thermal degradation, oxidation, saponification, etc. Additionally, the two types of synthesized biodiesels exhibited similar properties, with values that were in accordance with the specifications of the regulatory agencies.

The separation of the glycerol and biodiesel phases is a critical point in the synthetic production of ethyl biodiesel through the transesterification reaction because a stable emulsion is formed. Although there was concern that the addition of water could cause soap formation, none was observed. The high rate of conversion of the soy oil to ethyl biodiesel Additionally, the physical and chemical properties of the ethyl and methyl derivatives are equivalent and are within the limits established by the regulatory agencies.