6-6 Transesterification reaction demonstration

okay so we're going to do the transesterification reaction to make biodiesel from vegetable oil right here I have 200 milliliters of just some vegetable oil this is actually peanut oil and it's in the stir or it's in a Erlenmeyer flask and it's on the stir plate that's heating the oil up to 60 degrees C we want to be very careful that we don't overheat the oil because it can start to break down and then we won't have a good reaction so needs to stay as close to 60 degrees C as possible if we let it go lower than that then the reaction slows down if we let it get above 70 degrees C then we have polymerization and we don't have the oil than the triglycerides for our transesterification to to work so first thing I'm going to do now that I've got my oil measured out in heating is measure out 50 milliliters of methanol use my graduated cylinder to do this the and I'm going to place this 50 milliliters into a beaker a 250 milliliter beaker and the reason I don't measure inside my beakers because it's not got enough accuracy so this is a less accurate method it kind of gives me an approximate and even says here are approximate volumes so I use a graduated cylinder that's much more accurate so pour that into my beaker and now I want to measure out 0.85 to 1.1 grams of sodium hydroxide now I always want to add a dry caustic in this case to my solution and not the other way around there's a heat that's generated when caustic or acid is dissolved into a liquid and so we don't ever want to add the liquid to the solid we want to add the solid to the liquid if we were to have that adding the liquid to the solid there might be enough heat generated that we would start splattering things and we don't want to splatter concentrated acids or bases this is a base here that we're adding so I'm going to measure out in my scale somewhere between 0.85 and 1.1 grams of the sodium hydroxide beads look there's a little bit too much there 1.1 exactly so go with that and add that to my methanol this is the catalyst that is going to make our reaction proceed at a rate that's fast enough for us to notice [Music] okay I'll stir get that dissolved once this is dissolved and once my oil is up to the sixty degrees C that I needed that then I can combine these two solutions so now my oil has gotten up to sixty degrees C that's hot enough for our the reaction to proceed at a reasonable rate like I said we've got to keep this in a certain range the range that we need to keep it in is between fifty five degrees C and sixty five degrees C below 55 the reaction just sort of slows - too slow for us to make it worthwhile and then above sixty five we start getting into that polymerization of the oil which we don't want to happen so I'm going to take my method side solution which is that sodium hydroxide mixed with methanol and I'm going to pour that into the oil and we can immediately see that there's a change in the color that's a good indication that we've got a reaction starting this reaction needs to proceed over about a half an hour's time so we're going to keep it on the the the heated plate while it's stirring vigorously so that it can get good contact between the methoxide and the oil so the reaction can happen and it needs about a half an hour for that reaction to proceed so go ahead and let this store for half an hour in the meantime we'll be careful to watch our temperature and make sure that it stays in that 55 to 65 degrees C range so at this point the reaction has been proceeding and we've got this mixing for a half an hour and now we need to neutralize the solution because we still have that sodium hydroxide sitting in there and so we're going to use a little bit of vinegar so I'm going to measure 50 milliliters of vinegar and that's how we'll neutralize it [Music] since vinegar is an acid it will react that sodium hydroxide to just become salts and it's water so when you try our solution and we can handle it without worrying about the the base causing problems with our equipment in our hand so once I've neutralized that that means that the reaction is going to stop and at this point I'm going to go ahead and turn everything off and I want to just let this sit and settle for at least a day if you had to have a centrifuge you can put this into centrifuge tubes and make it the settling process happen but basically we want to let this settle out into the two layers the hydrophobic layer which is our biodiesel and that's going to be floating on the top and the hydrophilic are aqueous or our water layer which will be down here at the bottom we should see about a hundred milliliters of that equi assayer so we'll go ahead and let this settle out for about a day and then we'll be ready to use the biodiesel for product testing

Channel: Engineering Principles Utah

Views: 33,655

Keywords: Engineering Principles Utah, transesterification, biodiesel

Id: pHB-3NbY2AY

Length: 7min 46sec (466 seconds)

Published: Tue Mar 13 2018