Many people - most people? - will recall that the first Diesel engine, the one built by, um, well, Rudolf Diesel, ran on peanut oil, which may offer some explanation for Jimmy Carter's somewhat hyperbolic expectations for what biofuels can do, although everyone knows that Jimmy Carter was an ethanol guy in the end.
Rudolf Diesel died - probably a suicide - in 1913. (He should have died hereafter, there would have been time for such a word.)
Biodiesel thus is not new. It may now be considered "an alternative fuel" but we should all keep in the back of our mind that petroleum started out as an alternative to peanut oil.
Some eighty years after Diesel's death and the abandonment of "renewable" peanut oil in favor of petroleum the common modern enthusiasm for biodiesel has begun to rise both on an industrial scale and, to a lesser extent, in backyard production facilities. Germany, for instance, has a "renewable portfolio standard" that requires the addition of biodiesel to petroleum diesel. This is great if you're into "renewable portfolio standards" and maybe less than great if you're an organgatan or Sumatran tiger or rhino whose habitat has been rototilled to make a monoculture palm oil plantation so Germans can feel all renewally. (Renewally?) Organatans and sumatran rhinos and tigers aside, biodiesel can also be made out of waste oil cooking oil as well as waste industrial vegatable oils left over from things like the fractionation of soy bean oil to make lineoleic acid used to make some varnishes and paints. Indeed, in theory at least, biodiesel can be made from waste sewage grease and oils.
Fats and plant oils, such as canola oil, soybean oil, palm oil, tallow, etc, etc are all esters of fatty acids - long straight chain carbon molecules with a carboxylic acid function on the end - esterified to the three oxygen and three carbon trialcohol that glycerol is, we refer to these oils as triglycerides, or "triesters."
The biodiesel industry has lead to a huge glut of glycerol in modern times, and generally as a value added chemical, glycerol doesn't cut it, there isn't much demand for it except in specialty uses (in certain pharmaceutical applications for instance). The demand for glycerol cannot match the production of it: Often glycerol is simply dumped, usually along with all kinds of excuses and rationalizations about how it's "biodegradable."
Despite Rudolf Diesel's direct use of peanut oil in his early diesel engine, the natural triester oils are less than ideal as a fuel. In most biodiesel preparations, the triacyl glycerol ester is replaced by monomethyl esters. Fatty acid methyl esters have much better properties as fuels than native vegetable oils. If you buy biodiesel or biodiesel blends, it is almost certain that they are methyl esters.
So we have a lot of glycerol on our hands.
Now some excerpts from the paper, beginning with a less sarcastic statement of what I have already said:
Fast depletion of oil reserves and the continuing increase of the prices of petroleum products initiated major research for the development of nonpetroleum transportation fuel alternates.1,2Measures taken in Europe necessitated that the biocomponent content of the transportation fuels should be increased up to5.75% in 2010.3,4 Biodiesel, which consists of alkyl esters derived through trans-esterification of oils with alcohols, is considered as one of the most promising nonpetroleum transportation fuel alternates. It is considered as a nontoxic, renewable compression engine fuel with a cetane number as high as petroleum derived diesel fuel. Glycerol (G) is the main byproduct of biodiesel production. One mole of glycerol is produced per three moles of methyl esters, in the trans-esterification of oils with methanol. This is equivalent to about 10% (wt) of the product stream in biodiesel production. Recent increasing trends in the use of biodiesel as a transportation fuel alternate has the potential to create significant surplus of glycerol. Overall economics of the biodiesel production through the trans esterification process strongly depends upon the effective utilization of the side product glycerol.
Let's be clear on something though. If we rototilled all of Java, all of Sumatra, all of Borneo and put in palm oil plantations, there would still
not be enough biodiesel on this planet to support the European version of the car CULTure.
This would even be true if there were no major tsunamis in Indonesia like the one that killed a quarter of a million people in Indonesia and the surrounding area in 2004, not that anyone remembers that tsunami, since that tsunami didn't offer the very enjoyable opportunity for millions of anti-nukes to have thousands, if not millions of tons of coal burned to power their computers so they can all wonder, interminably, about the question of whether one, two, or even maybe ten people might conceivably someday die from exposure to radiation at Fukushima.
That's one of the few joys of being an Orangatan, I would suppose, you don't have to think about these kinds of things.
Now for some interesting stuff from the paper:
Alternative conversion processes of glycerol to value-added products was reviewed by Pagliaro et al.5 Selective oxidation of glycerol to glyceric acid, dihydroxyacetone, mesoxalic acid, etc.;hydrogenolysis to propylene glycol; dehydration to acrolein,etc.;6 and reforming to synthesis gas and acetylation to esters7are some of the possible alternative routes to convert glycerol to valuable products. One other highly attractive process for the conversion of glycerol to value added products is its etherification with iso-butene (IB) or alcohols to produce fuel oxygenates.4,5,8
So you see a lot of other work has been done to find something useful to do with glycerol. The rest of this paper is about the latter products, the "etherification" products with isobutene.
Isobutene is a very important commodity chemical around the world, with somewhere in the neighborhood of a million tons, plus or minus a few hundred thousand tons, being manufactured each year. The main use is to make so called "butyl rubber" which is a copolymer of isobutene and isoprene, and which is the main material in nearly all of the tires on earth. As it happens, butyl rubber, which is synthetic, is very close to the biological product obtained from rubber trees. Isobutylene occurs in trees - when Ronald Reagan made his insipid remarks about how air pollution is caused by trees - he was mangling this information about the release of isobutylene from trees, where it serves as a precursor to various kinds of terpenes associated with the odors that trees generate. However almost all of the isobutylene in commerce is derived from dangerous fossil fuels, primarly petroleum. (Methanol is also generally made from the dangerous fossil fuel natural gas, although it is relatively straight forward to obtain it via the hydrogenation of carbon dioxide or carbon monoxide.)
The United States industrialized the production of synthetic butyl rubber because during World War II, Japan controlled most of Indonesia and Malaysia, where the rubber trees grew (and still grow). The United States at that time had lots of oil, and was, in fact, the world's main exporter of oil and had, in 1941, cut off oil supplies to Japan. So Japan, wanting Indonesian oil, attacked the US fleet which threatened its flanks, giving Japan, albeit temporarily, all the oil and rubber it could use.
And the United States, then without rubber trees but with lots of oil, abandoned "renewable" rubber in favor of petroleum rubber.
Cute, I think.
Watch out you damn Orangatans, "natural" "renewable" rubber could come back.
But not to worry, we have lots of glycerol on our hands now that we're making lots of "renewable" biodiesel and according to the paper, we could use this to make even more fuel:
As a result of etherification of glycerol with iso-butene or with tert-butyl alcohol (TBA) over solid acid catalysts, a mixture of monotert-ethers of glycerol (3-tert-butoxy-1,2-propanediol (MTBG1)and 2-tert-butoxy-1,3-propanediol (MTBG2)), ditert-ethers of glycerol (2,3-ditert-butoxy-1-propanol (DTBG1) and 1,3-ditertbutoxy-2-propanol (DTBG2)), and tritert ether of glycerol(1,2,3-tritert-butoxy-propane (TTBG)) are expected to be produced.9,10,12,13 These ethers were reported to have very high-octane numbers9 and can be considered as alternative gasoline blending oxygenates to MTBE and ETBE. They were also reported to have good burning properties with reduced pollutant and particulate matter emissions, when blended to diesel fuel.8,10,14Due to their higher solubility in diesel fuel, diethers of glycerol were preferred over monoethers, as fuel additives.
MTBE, famously, was widely used in gasoline formulations and was spectacularly successful at reducing air pollution, which kills, on average, 3.3 million people per year.
Unfortunately, it also led to some intractable issues with ground water, leading to a high level of excitement that caused it to be banned. The ethers being proposed here are similar to MTBE, but also are different, probably with respect to their water solubility and biodegradability. It may - and I'm not sure that it would be fair to say will
instead of may
be far less noxious than MTBE, although, as someone who's worked with MTBE a fair amount, it does seem possible to me that MTBE is probably not as bad as advertised, certainly not as bad as air pollution itself.
Nevertheless, the MTBE case represents a case where an "environmental" solution to an "environmental" problem is itself an "environmental" problem.
Lucky for you you're not an orangatan.
The rest of this paper is fairly technical, and concerns the issue of substituting t-butyl alcohol - the four carbon alcohol where three of the carbons are bonded to 3 hydrogen atoms each, and one is bonded to the other three carbons and a single oxygen that is bonded to a single hydrogen - for isobutylene.
This kind of chemistry is relatively rare: Most butyl ethers, and for that matter, many butyl esters are made using isobutylene which is acid catalyzed to give the fairly stable corresponding cation, resulting in a classic SN1 type of chemical reaction.
Looking back on the tenor of this diary, I might seem a little bit overly negative. I do believe that this type of biofuel has a niche, and, if careful attention is paid to its sources and best efforts are used to use waste oil from commercial operations, biodiesel would make an excellent transition tool for the conversion from a very dirty fuel, petroleum diesel (or Fischer-Tropsch diesel) to a much cleaner fuel, DME, or dimethyl ether, which can, although to my knowledge the issue is not industrial - be made by the direct hydrogenation of carbon dioxide, using, in the best case, nuclear hydrogen.
I have written about this before in this space.
DME is an outstanding fuel and runs diesel engines, and spark ignition engines, quite well, as well as filling all the niches now using dangerous LPG and dangerous natural gas. However, there are some issues in the diesel case with lubricity, and formulations of DME with biodiesel, dimethyl carbonate (also obtainable from hydrogen and carbon dioxide) or more exotic species like these glycerol butyl mono, di, and tri ethers, might help reduce the time and effort in making a transition to a pure DME culture.
But a pure DME culture will not occur most likely, because what is wise is seldom what is obtained.
Other papers relating to biodiesel and glycerol in this same issue are these:
Biphasic Model Describing Soybean Oil Epoxidation with H2O2 in Continuous Reactors
Glycerol Chlorination in Gas–Liquid Semibatch Reactor: An Alternative Route for Chlorohydrins Production This paper shows how to make the very important chemical epichlorohydrin from a biological source.
Biodiesel Process Intensification by Using Static Mixers Tubular Reactors
Influence of Hydrogen in Catalytic Deoxygenation of Fatty Acids and Their Derivatives over Pd/C
This may be dry stuff - I'm sure it is - but I thought it interesting, and decided to babble a bit about it.
I certainly hope I didn't annoy anyone.
Have a wonderful day tomorrow.