[MUSIC] Welcome I'm Dr. Robert Pomeroy and I'm from the Department of Chemistry and Biochemistry at UC San Diego. I'm a faculty member, and I'm also the adviser of the Biofuels Action and Awareness Network on campus which converts waste vegetable oil into biodiesel. I'm also a member of CalCab and work and teach a class in the EDGE program here on chemistry and analytical chemistry of biodiesel. So I'm going to talk to you today about biodiesel chemistry and analysis. And the overview of what we're looking at is well, why do we use diesel engines, and, and how do they work, and what makes them different than gasoline engines? And then why biodiesel would be used instead of regular petroleum diesel, and what are the advantages and disadvantages of that? And we'll look at the, the benefits and then the concerns. We're also going to want to find out how we convert the waste vegetable oil, or lipids, into FAMEs, and then we do this by one of two methods. That's by a base or an acid catalyzed reaction, and we'll look quickly through both of those mechanisms. And then we'll walk our way through, in the production process, how we make the biofuel altogether, and what are the products, the by-products, and the artifacts of processing. And in the end we'll look at the instrumental and the chemical techniques so that we certify the quality of the fuel. And that's really the end game here, because if we're going to put it in people's engines, it has to meet a certain quality. So back in 1900 at the Paris World Fair, Rudolf Diesel introduced his diesel engine. And this engine works without spark plugs, and it's a compression engine, and it can run on vegetable oil. In fact the very first one was run, meant to run on peanut oil. And what he was trying to do was empower farmers to be able to have and grow their own fuel for the energy needs on a farm for tractors and things like this. And you can see here, here's Diesel and his patent and then the actual engine that was at the World's Fair is now in a museum in Munich. Why is this important to all of us? 90% of all the freight in the United States moves by diesel whether it's in long distance and short distance trucking, diesel locomotives or diesel cargo ships across the country. Almost all of our buses and heavy machineries run on diesel. And this moves a tremendous number of people, 14 million school children, 18 million tons of freight, 14 million consumers, cust, commuters via bus. Now what's important about this is why diesel engines get used for these big heavy engines, is that they're 30 to 200% more efficient than a regular gasoline engine. And they're more durable, meaning they'll last longer by 50 to almost 300% over a gasoline engine. They're heavier engines and so as a result it makes sense when you're hauling around heavy things. Because they are heavier and bigger engines it also takes longer for them to heat up, so there's also an issue of how quickly they can come to operating temperature. And so these are things that effect why we choose one sort of car and, and fuel in the United States versus another. So, in the true diesel engine, right, we bring the air into the combustion chamber. And so here's our garden variety picture of one piston. And on the intake stroke, air is drawn into the cylinder, and on the compression stroke, we get really high compression that results in temperatures up above 550 degrees Celsius. At these temperatures, if we were to inject the fuel through the fuel injector right here, right when the cylinder reaches top dead center, you're going to get automatic combustion of the fuel. There's no need for a spark, it's so hot in there the fuel automatically burns, and it's burning so hot, you get complete combustion or very close to complete combustion. And, then this drives the piston down during the power stroke. And then there's an exhaust stroke where we open the exhaust port push out the waste gasses and then bring back in the new gasses to start the next cycle. The amount of energy that we get out useful in this system is the area bounded by that curve there. And it turns out at these high compression ratios the diesel engine is the most thermally efficient engine, meaning that it gets the most workable energy out of the heat that we generate from this combustion reaction. So, what are the benefits and concerns about biodiesel, right? The most important one is that there's higher engine efficiency. It, it burns cleaner, it burns hotter, it burns smoother. There's less engine knock. It also provides improved lubricity. Biodiesel by itself actually helps lubricate the pistons in the engine so that we don't have to add any sulfur. As a result, there's no sulfur in the fuel, for the most part. It has very low sulfur content, and it is important from a pollution point of view. We have reduced hydrocarbon and carbon monoxide emissions because we get near complete combustion. The fuel's already partially oxygenated. So, like, in the summer blends for gasoline, where we add ethanol. Here, there's already oxygens in the fuel and so we get complete combustion and very little carbon monoxide. This then remove, reduces the amount of particle emissions, particulate matter, PM. And so, with, this is a real health concern in this country, because we're all inhaling this stuff. And we're looking at all times to start expanding freeways and who lives near the freeways? They're usually the people who are at the biggest risks for the, with the poorest healthcare. The other upshot of that is that one of the things that gets made as particulates in an engine are aromatic compounds, in particular a class called parapolycyclic aromatic hydrocarbons, PAHs. And these are known cancer-causing agents. By using bio-diesel, we're reducing the net CO2 emissions because we captured that carbon from the atmosphere in the first place, and the material turns out to be non-toxic and bio-degradable. So all together, it's really just greener, mm-kay? Now, things we have to worry about. These are mostly operational. Material compatibility, most garden variety diesel engines, you may have to change some of the seals in the system, otherwise the biodiesel will wear away at those guys. Because of the oxygens in this that helps the benefits, it also then creates a problem for water consumption. Again water being incorporated into the fuel over time. Because it burns at a higher temperature and we're drawing air in from the atmosphere, you'll get increased NOx emissions, these are nitrogen oxides. But these emissions can be reduced by using a proper catalytic converter. We have a problem with low temperature utilization. So you're in southern California, it would not be much of a problem. But in winter in Minnesota the viscosity of these fuels would get so thick that it would probably clog all the filter systems and not be able to be used. There is a slight reduced energy content in this fuel compared to regular petroleum diesel. And it also is unstable with respect to oxidation, six months maybe unless you start adding additives for this stuff. Whereas on the other hand, petroleum diesel would last literally months, years, decades in storage without taking in on any water. Solvency? It's a great solvent and this also leads to the idea that it damages the paint. It also will take all the junk off the inside of the engine if you've been running regular petroleum diesel then this tends to clog all of the filter systems up in the car. And then ultimately why it probably doesn't get used all that much is because there's not enough feed stock and it has a higher cost. So why do we convert these things? In a modern diesel engine, right, that uses petroleum, then if we're going to use that engine with its fuel pumps and its injectors, then we need to better match the viscosity of the fuel. The first diesel engine by Rudolf Diesel actually ran on peanut oil. But that's got a much higher viscosity resistance to flow and so we need to better match the viscosity of the biodiesel to that of the petroleum diesel. And we do that through a process called transesterification. Right? This was invented and talked about by Chavanne in 1937. Who proposed to turn it into their fatty acid metal esters, also known as FAMEs. The process of transesterification is outlined right here. We take an triglyceride, or an, a TAG, a triacylglyceride, react it with three equivalents of an alcohol in the presence of a catalyst. We're going to get glycerol as a byproduct, but that's easy for us to separate, and we'll get three equivalents of methyl esters. These methyl esters are direct drop-ins for the diesel engine. We can put them right in there, the fuel pumps. The injectors work just fine. And so we can do a direct drop-in if we make them into the, the fatty acid methyl esters. So, here's that picture, again, for the process. And I've circled here where the glycerol backbone is. So that we can sort of watch this as we work our way through the, the mechanism. And so we're going to start off with an alcohol. And so R is standing for CH3, or any alkyl group. It almost always is methanol, but it can be ethanol. Reacts with a base like sodium hydroxide and you'll get an alkoxide in this case, that'd be methoxide. So any alkyl oxide with a negative charge is an alkoxide. And now this is going to come in with its negative charge, it's going to want to attack this carbon right there. Now, in these chains we've got our prime, our double prime and our triple prime and these are alkyl chains that are all carbon hydrogen bonds or carbon carbon bonds. These are very stable bonds that are fairly non polar, as a result this molecule here has very little affinity to get in and react there. On this carbon, on the other hand, it's attached to these two oxygens. And the electronegativity of those oxygens has pulled electron density away, making this carbon partially pos, positive and then vulnerable to attack. So, when that happens, the alkoxide comes and attacks this carbon. And forms this intermediate at number two here. And this is called a tetrahedral intermediate. So there are now four things attached to that carbon. So, while this is made, this is not the most thermodynamically stable configuration of the molecule. There's thermodynamic rationale for reestablishing the double bond. But there can only be four bonds to the carbon at one time, so one of these bonds has to go. Now, the bond to the R group is too strong, it's not vulnerable. If we sever this bond right here, we're basically just reversing the first step. And so that doesn't get us anywhere, all right? If we take and sever this bond, I've now taken the fatty acid methyl ester and cut it away from the glycerol backbone. That's where we want to go. In order to force that through, we're going to flood the system with methanol. So while it only takes three equivalents, we often times flood the system with methanol. And using Le Chatelier's principle, drive that reaction to completion by just having way more of these available in the system so that I sort of keep clipping off the backbone. So when we're all done, we wind up with our fatty acid methyl ester. And now what I'd have here is a diacylglyceride. And so we can repeat that process over, and over, and over again until I wind up having cleaved away all three fatty acids. And being left just with the glycerol, once I've done my acid, proton transfer in solution. Now, we did it in base just a minute ago. You can also do it in acid. The mechanism is very similar. The only difference being in order to make this carbon, so here's our carbon yield carbon from before. In order to make this carbon more vulnerable, we're first going to have a hydrogen in acidic media form this cation here then form this intermediate. Now if you look that intermediate looks a lot like what we proposed existed in the prior slide only now this time there's a formal charge there, which means this doesn't have to have the hydrogen removed. The lone pairs on that oxygen can attack that center and we go basically through the same process in forming the fatty acid methyl ester. So, we have choices. We can do it in acid or in base. So here's sort of a picture of what happens if we run this reaction. It, if you heat the oil up to about 40, 50 degrees Celsius, add in the methoxide, stir, and let it go for about 20, 30 minutes, and then let it sit, it will separate. In this top layer, you'll get the lighter color here is the fatty acid methyl esters. Now if they were absolutely pure it'd be colorless, but the pigments that are often in these oils are also soluble in both the FAMEs and in the glycerol. It's more soluble in the glycerol so you notice the glycerol layer which is depicted right here, is the darker layer on the bottom. The glycerol is not missable, means it does not dissolve well and mix well into the biodiesel. It's denser so it falls to the bottom. It's just like oil and water. So in principle the top layer should all be our fatty acids. And the bottom layer should take the all glycerol and it should've in principle, drug all the guys that I've got in the white box. Which is the methanol free fatty acids, leftover catalysts, calcium and magnesium which should've come from the pigments by exchange, water, glycerol, or unreacted mono and diglycerides. The good news is all the things in the white box are really fairly soluble in water. So after we drain the glycerol away from em, just by putting a valve in the bottom of the reactor, all we then have to do is wash the biodiesel, which will continually remove all the guys in the white box. Okay, so another way to look at this pictorially is, we'll take our methanol and our catalyst, and our oil and our fats, and we're going to preheat em, and filter them, and then put them into our reaction chamber. Once they're in our reaction chamber, right, when we're all done, we're going to draw off and drain off the glycerin. Once we've drained the glycerin away, then all we should have left is the dirty biodiesel, and we quite literally just wash with water. The water is heavier, sinks to the bottom, just keep draining it away. And when it's all done, what we have is biodiesel that is free of all the other contaminants inside that white box, but not the water. So the last step is to dry, and drive the water out. Or you can use dry wash beads and do an ion exchange sort of reaction. And then you're left with nice, clean, dry, biodiesel that you can put in your car. Mm-kay, now, to put it in your car, and not face any of the problems and liabilities with using lousy fuel, the ASTM has set up a set of requirements for what should be the purity of this fuel before it goes into anybody's car. And so they tell you how much calcium, magnesium, sodium, potassium can be there, right? The phosphorus content, the amount of total glycerine, free glycerine, carbon residues, Cetane number, sulfated ash, kinematic viscosity. All these parameters are about checking how well the fuel will combust, what the emissions will look like, and what impact it will have on the wear of the engine. So all of these parameters are things that as chemists we need to check before the fuel should go in anybody's car. So how do we determine those things? So energy content is determined through a bomb calorimeter, the oxidative stability through the rancimat. The name is derived from being rancid like mayonnaise that's left to oxidize and sit out in the room. These oils go bad, the double bonds in the alkyl chains can react with oxygen and, and, create the compounds that are not as stable. There's the Pensky Martin Flash Cup, we want to figure out what the flash point of this fuel is. This is important for wa, the way the engines are designed. We want to make sure they meet a minimum value. Typically though, our biodiesel flashes at a much higher elevated temperature than regular petroleum diesel. As a result, this is what leads to it being cleaner and better as a, from a emissions point of view. And then last, all right, we on this slide we have our Karl Fissure Titration, which is a means of determining the amount of water in the biodiesel. Determining the amount of trace water is not very straightforward because you can't drive it off by, by physical means and there are very few chemical reactions because water is pretty stable. So this is a very unique cocktail of reagents in order to find the react, the water that's in the sample. We also need to monitor the viscosity. This is probably the most important parameter because it affects the way the fuel injections work and their spray pattern. And viscosity is the measure of resistance to flow. So the way that we monitor that, there are a series of capillary viscometers. This is one way to determine the viscosity where we just pass the sample through a small capillary, and we measure the time it takes to do that, and that tells us the relative viscosity of the sample. And if it's in a certain range, then it ought to work with our fuel pumps, which are expecting how much wear and drag the viscosity is going to impart. And then for the fuel injectors to, to figure out what the spray pattern will be, and how smoothly and efficiently the oil, the fuel, pardon me, will combust inside the engine. So, we also use gas chromatography, mass spectrometry, to monitor the reactions and the yields. And we can also look at for impurities like the glycerol, and we use internal standard. And so the beauty of GC mass spec is it takes complex mixtures and separates them out into their individual components. And that's the chromatography part. And then the mass spectrometry part allows us to look at the molecules that come out of the chromatograph, fragment them into pieces, and through the analysis of those fragments we can determine what the molecules were in terms of, of structure. We're also interested in elemental analysis, the sodium, potassium, magnesium, and calcium that can come from the catalysts or the exchange of ions from the pigments. Also the phosphorus and the sulfur content have an impact on what happens to the engine and the catalytic converters. And so we do that by inductively coupled plasmum optical or mass spectrometry. An inductively coupled plasma is just a really hot source, so when we put the fuel inside this, this hot burning flame, it basically breaks everything down to atoms. Every atom has its own, unique emission pattern, so it creates a fingerprint. So the analysis of all these lines, a little bit like looking at a, a starry night, we can actually tell what elements are in there. Another way to do it that we've been using in our lab recently is using X-ray fluorescence. This is a nondestructive technique that also works very well for sulfur and then metals. And so this is going to be, allow us to, to monitor what's maybe happening in waste streams as we try to recycle elements in the, in the process of rub growing algae. And so here's sort of a summary of all the ASTM specifications and what their property is and why they're important. And you'll notice once again, it's all about how well does it burn. What would the particulates or the emissions look like? How does it flow and will it basically become a maintenance problem for you? And so this is why we have to keep track of all these different parameters in order to be able to put this fuel in your car. And so, what you see here is a slide just to, basically conclude the talk today. Where we've actually taken some algae grown here at the university using hexane extraction to separate out and draw out the lipids in this process, so that we can then turn those into FAMEs. In fact we've done this on a larger scale, both by press and chemical extraction where we created biofuel that went into a diesel powered motorcycle that ran in the Baja 1000. So there are, you know, tangible, outcomes of this kind of work. So if there's anything else I'd like to thank you for your attention.
