Sciencemadness Discussion Board

Valorizing the Glycerol from Biodiesel Production

Ozone - 14-11-2006 at 18:28

Hello everyone!

This is a spin-off from Chemoleo's thread regarding the production of biodiesel. It became apparent that we will soon have more glycerol than we know what to do with.

Here, we shall address the issue of valorizing, or adding value to the glycerol produced during the manufacture of biodiesel. Other than nitration, I think that just about anything is fair-game.

So far, we have discussed fuel use, and why this is not such a good idea (acrolein, polymer fouling), and, ahem, laxatives.

This, however segues neatly into chemistry and biochemistry that can be performed to turn glycerol into more valuable material. Granted, acrolein is *extremely* toxic, but it is used as an industrial feedstock of value.

Attached is a mechanism outlining the E1 dehydration of glycerol under anhydrous conditions (hard to avoid at the boiling point of glycerol!). My apologies if there is a mistake in it, but I just whipped it out for this.

I have also noticed that vinyl dioxolanes result from the acetal formed with glycerol and product acrolein.

For the Biochemists amoung us, an interesting article with full text:

"METABOLISM OF GLYCEROL BY AN ACROLEIN-FORMING LACTO-BACILLUS"
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=27...

How about 1,3-propanediol?

Happy, er, greasling?

O3

acrolein.gif - 7kB

12AX7 - 14-11-2006 at 20:01

Esters with other things oughta make it a better fuel... how about...alkyl carboxylic acids, possibly long chain?

Oh...er...nevermind.

:P

Esters have a lot of oxygen in them, but how about ethers with alkyl-ols, how hard are those to stick to glycerin? (Probably not economical, but we're not minding that, huh?)

Tim

[Edited on 11-15-2006 by 12AX7]

unionised - 15-11-2006 at 11:29

I have worked with acrolein and I don't recommend it. They weren't kidding when they sugested it as a war gas.
Can ordinary yeast ferment glycerine to anything- alcohol would be useful but dull.
Come to think of it, what do mamals metabolise it to- would it be useful as animal food?

Chris The Great - 15-11-2006 at 15:56

Lube? It IS one of the main components in KY jelly AFAIK. Not only will we have cheap fuel from biodiesel, we'll be happy when not driving our cars as well :D

Dynamite and lube are really the only two easy uses I see coming from it.

Although, perhaps acrolein could be oxidized to acrylic acid and used as a starting material to make plastics? Does anyone know how easily such a reaction occurs, and how easy acrylic acid is to form an ester?

I guess one could react with a strong base to give a salt of acrylic acid and allyl alcohol, since if we have glycerin coming out of our ears from biodiesal production, we can afford to lose half of it to allyl alcohol, which I'm sure has some good uses as well.

Unfortunately we are still going through acrolien at one point in the procedure.

Ozone - 15-11-2006 at 16:34

Good evening!

Well, glycerine is an important side product from the ethanol fermentation of molasses using yeast. From what I understand, the ethanol fermentation is performed first, and then the osmotic pressure is kicked up and the stillage refermented to yield lots of glycerol (a process that led to a glut in the existing market). A full paper is given here:

http://www.pubmedcentral.nih.gov/picrender.fcgi?artid=168312...

Also, USDA (and Rice, it looks like) is looking at further fermentation of glycerol to yield, among other things, succinic acid (This is also the objective furthered by DOE). Please, see:

http://www.ars.usda.gov/research/publications/Publications.h...

As for nutritive value, it appears to be negligible as the body seems to quickly metabolize what it needs to make triacylglycerides and phospholipids; some gets shunted around via the glycerol phosphate shuttle to yield ATP in mitochondria. The rest is eliminated in urine and the excretory half-life is rather short, viz. 30min. For more information, see the pharmacokinetics subheading here:

http://www.pdrhealth.com/drug_info/nmdrugprofiles/nutsupdrug...

See also, glycolysis, where glycerol exists as an intermediate cycling from dihydroxyacetone. This is a small part of the lactic acid, or Cori cycle.

Oh yes, acrolein is foul. Even with an *efficient* hood, you can tell that something is bothering you.

Yes, acrylic acid and allyl alcohol have good industrial value. This is mostly for the manufature of acrylic polymers, etc., viz. poly-acrylic acid (fibers). It too stinks, and has been known to destructively polymerize under temperature gradient even when cold. I retrieved some from a freezer once, and read the container that said specifically, do not freeze--local heating can cause destructive polymerization... I realized that my fingers were locally heating it, and placed it *carefully* into the hood. Nothing bad happened. It warmed up and I went on with life. Stinky though.

It looks like it would probably oxidize in air, faster with a catalyst (but, that double bond is just looking for a reason to polymerize). Maybe addition of a heterogenous inhibitor like Cu filings would prevent this whilst enabling the oxidation?

'evening all,

O3

[Edited on 16-11-2006 by Ozone]

Tacho - 16-11-2006 at 02:13

Glycerol retains moisture. Wouldn't it be useful for agriculture if mixed to soil? Not for the water itself, but as a soil "softener".

Ozone - 16-11-2006 at 16:05

Do you mean "easier to dig"? I know that they sell special polymers that can hold many times their weight in water for use in soil.

Cheers,

O3

Tacho - 17-11-2006 at 04:15

Yes, that is the idea, but I was thinking about farming, not flower pots.

Can't glycerol be polymerized?

Ozone - 18-11-2006 at 08:42

Hmm. That might work, but would take a lot of glycerol. Glycerol is water soluble--wouldn't it eventually leach out during rains? What would be the potential environmental impact of the application of glycerol on this scale (it will definitely increase COD and likely, BOD as well)?

It can be step polymerized via esterification, I have done this with citric acid (with additional H2SO4 catalyst). It gets very thick, and you can pull fibers from it...But, it is hygroscopic and unstable (it dissolves and depolymerizes in contact with moist air, quickly). This could result from either remaining catalyst in the polymer (which is, itself hygroscopic) and/or relatively low molecular weight (99.+% conversion is kinetically required for HMW polycondensation).

Cheers,

O3

Tacho - 22-11-2006 at 09:36

Adding three halide atoms to glycerol should be easy. Trichloropropane is a nasty pesticide.
triiodopropane - 13 hits on google
tribromopropane - 564 hits

Any use for that?

Ozone - 23-11-2006 at 10:24

Happy Thanksgiving!

The triiodo species referred to online are predominantly 1,1,1; 1,1,2; and 1,2,2. This implies radical halogenation and/or addition across a double bond, not nucleophilic substitution (as we would see with an alcohol). Simply adding HCl (conc) to glycerol will yield via SN1 (mostly) the most stable (in this case 2°) carbocation which will then be attacked by X- (X=F<Cl<Br<I, in aqueous media) to yield mostly 2-iodo-1,3-dihydroxypropane. This might be interesting as the skies-the-limit on what you can do with a leaving group that is as good as I (very soft nucleophile). In order to carry out the SN2 required on the 1 and 3 hydroxyls, a polar aprotic solvent (acetone is a good one for this) will be preferred.

This is of course, assuming that the glycerol stays functionally intact thoughout the procedure.

At either rate, the idea is I think, is good-leading to further discussion, viz. where can we go from, say, 2-iodo-1,3-dihydroxypropane.

[edit] that's weird, the text window is correct, but the preview and post seem to cut off: - (X=F<Cl<Br<I, in aqueous media) to yield mostly 2-iodo-1,3-dihydroxypropane. This might be interesting as the skies-the-limit on what you can do with a leaving group that is as good as I (very soft nucleophile). In order to carry out the SN2 required on the 1 and 3 hydroxyls, a polar aprotic solvent (acetone is a good one for this) will be preferred.

[edit] let's try that again: to yield mostly 2-iodo-1,3-dihydroxypropane. This might be interesting as the skies-the-limit on what you can do with a leaving group that is as good as I (very soft nucleophile). In order to carry out the SN2 required on the 1 and 3 hydroxyls, a polar aprotic solvent (acetone is a good one for this) will be preferred. *the part the post did not like was an order of nucleophilicity in water where F is least and I is greatest which used "less-than" symbols.

Gobble Gobble,

O3

[Edited on 23-11-2006 by Ozone]

[Edited on 23-11-2006 by Ozone]

12AX7 - 23-11-2006 at 11:16

Quote:
Originally posted by Ozone
X- (X = F [lesser than] Cl [lesser than] Br [lesser than] I, in aqueous media)


Nothing to disable HTML parsing. "Lesser than" begins an HTML object...

Tim

Ozone - 23-11-2006 at 13:05

Thanks!

I narrowed that down as the cause, but was not quite sure why!

O3

Tacho - 23-11-2006 at 14:50

Ozone also doesn't seem to affect glycerol. That is sad, because if we could cheaply oxidize one or two of those OH groups to carboxilic acids there would be a huge crosslinking due to ester formations among molecules, wouldn't it?

I tried to add some acetic + sulfuric acids to glycerol, hoping to get the thickening you mentioned with citric acid, but nothing happened.

Ozone - 26-11-2006 at 09:40

Tacho,

It's got to be pretty hot! Regulate the temperature at ~130-150°C and try first, a 1:1 molar equivalence (thick paste). Add the citric acid (I use anhydrous, but at these temperatures, it should be OK), then the glycerol. Begin heating, stirring with a glass rod. At about 60°C the mixture should "loosen-up". Add 1 drop of H2SO4 (conc.). Magnetic stirring can be done from here until the mixture reaches conversion sufficient to stop the bar. Try removing a drop with a glass rod, cooling slightly, touching it to the bottom of a beaker; try to pull a thread. It should do this. The fiber will then get wet and dissolve:(.

I am playing with this to try and get something that is not so hygroscopic. I've started taking photos, and should be able to post some soon.

Good luck,

O3

not_important - 26-11-2006 at 20:53

Quote:
Originally posted by Tacho

I tried to add some acetic + sulfuric acids to glycerol, hoping to get the thickening you mentioned with citric acid, but nothing happened.


You won't get thickening with acetic acid. Citric acid is a tribasic acid, it forms polymers with polyols. Acetic acid is monobasic, you just get esters of acetic acid, although in this case it would have the trival name "glycerol acetate" with 2 or 3 acetates combined with each gycerol (depending on how hard you wack the reation mix).

Organikum - 27-11-2006 at 02:56

IIRC glycerol through a hot tube with zinc catalyst produces predominantly pyruvic acid, but I might be wrong.

solo - 27-11-2006 at 17:21

Reference Information




Hydrogen or Syn Gas Production from Glycerol Using Pyrolysis and Steam Gasification Processes
Valliyappan, Thiruchitrambalam
Thesis Degree- Master of Science, Department Chemical Engineering

http://library2.usask.ca/theses/available/etd-01042005-14033...

Abstract
Glycerol is a waste by-product obtained during the production of biodiesel. Biodiesel is one of the alternative fuels used to meet our energy requirements and also carbon dioxide emission is much lesser when compared to regular diesel fuel. Biodiesel and glycerol are produced from the transesterification of vegetable oils and fats with alcohol in the presence of a catalyst. About 10 wt% of vegetable oil is converted into glycerol during the transesterification process. An increase in biodiesel production would decrease the world market price of glycerol. The objective of this work is to produce value added products such as hydrogen or syn gas and medium heating value gas from waste glycerol using pyrolysis and steam gasification processes.

Pyrolysis and steam gasification of glycerol reactions was carried out in an Inconel®, tubular, fixed bed down-flow reactor at atmospheric pressure. The effects of carrier gas flow rate (30mL/min-70mL/min), temperature (650oC-800oC) and different particle diameter of different packing material (quartz - 0.21-0.35mm to 3-4mm; silicon carbide – 0.15 to 1mm; Ottawa sand – 0.21-0.35mm to 1.0-1.15mm) on the product yield, product gas volume, composition and calorific value were studied for the pyrolysis reactions. An increase in carrier gas flow rate did not have a significant effect on syn gas production at 800oC with quartz chips diameter of 3-4mm. However, total gas yield increased from 65 to 72wt% and liquid yield decreased from 30.7 to 19.3wt% when carrier gas flow rate decreased from 70 to 30mL/min. An increase in reaction temperature, increased the gas product yield from 27.5 to 68wt% and hydrogen yield from 17 to 48.6mol%. Also, syn gas production increased from 70 to 93 mol%. A change in particle size of the packing material had a significant increase in the gas yield and hydrogen gas composition. Therefore, pyrolysis reaction at 800oC, 50mL/min of nitrogen and quartz particle diameter of 0.21-0.35mm were optimum reaction parameter values that maximise the gas product yield (71wt%), hydrogen yield (55.4mol%), syn gas yield (93mol%) and volume of product gas (1.32L/g of glycerol). The net energy recovered at this condition was 111.18 kJ/mol of glycerol fed. However, the maximum heating value of product gas (21.35 MJ/m3) was obtained at 650oC, 50mL/min of nitrogen and with a quartz packing with particle diameter of 3-4mm.

The steam gasification of glycerol was carried out at 800oC, with two different packing materials (0.21-0.35mm diameter of quartz and 0.15mm of silicon carbide) by changing the steam to glycerol weight ratio from 0:100 to 50:50. The addition of steam to glycerol increased the hydrogen yield from 55.4 to 64mol% and volume of the product gas from 1.32L/g for pyrolysis to 1.71L/g of glycerol. When a steam to glycerol weight ratio of 50:50 used for the gasification reaction, the glycerol was completely converted to gas and char. Optimum conditions to maximize the volume of the product gas (1.71L/g), gas yield of 94wt% and hydrogen yield of 58mol% were 800oC, 0.21-0.35mm diameter of quartz as a packing material and steam to glycerol weight ratio of 50:50. Syn gas yield and calorific value of the product gas at this condition was 92mol% and 13.5MJ/m3, respectively. The net energy recovered at this condition was 117.19 kJ/mol of glycerol fed.

The steam gasification of crude glycerol was carried out at 800oC, quartz size of 0.21-0.35mm as a packing material over the range of steam to crude glycerol weight ratio from 7.5:92.5 to 50:50. Gasification reaction with steam to glycerol weight ratio of 50:50 was the optimum condition to produce high yield of product gas (91.1wt%), volume of gas (1.57L/g of glycerol and methanol), hydrogen (59.1mol%) and syn gas (79.1mol%). However, the calorific value of the product gas did not change significantly by increasing the steam to glycerol weight ratio.

Ozone - 28-11-2006 at 17:05

Thank you, Solo.

The only problem with most Fisher-Tropsch and friends is the cost of energy (and, in the first case, carrier--N2 at rates required at industrial scale can rapidly offset the product value, particularly if the product(s) need be transported). In the US, most industrial energy (steam) is derived from natural gas (NG) powered boilers. NG has been floating between 4 and $12 US per mcf,viz. unless you are using CO or H2 directly in a process (insertion chemistries, hydrogenation) the price vs. NG will not likely work in your favor; this is why the NH3 industries in the US have gone four-legs-up-the cost of fueling the process with NG was too high for profit on operation to be achievable.

However :), These processes, particularly the hydrocracking, *might* be feasible at a sugar mill which is powered almost entirely on bagasse, which is free. The vertical integration of this mill with a nearby end user would be required, however.

Organikum, do you have a reference for the Zn/pyruvate reaction (this would be something I would try)?

I have found some methods (in the literature) whereby glycerol is treated with Zn/HCl to yield 1,3-propanediol (I will try to get the refs. tomorrow; I have them in the work-lab). Presumably, this must go through the dihydroxyacetone intermediate which then undergoes Clemmeson-type reduction to yield the product; it must take place in dilute solutions to prevent the facile dehydration of the 2° hydroxyl?

Most recently, I have tried the polycondensation in ionic fluids*. Something seems to happen (viscosity goes way up) in 1-ethyl-3-methylimidazolyl methanesulfonate, but the products are difficult to isolate, viz. ionic liquids seem to solvate fricking everything (except for solvents that I am trying to avoid in a "green" synthesis. Bummer. I did get some white crystalline ppt from a sample dissolved in water+Na2CO3 and partitioned with MeOH. I suspect this is a "worthless" salt. I'll filter it tomorrow and run it by some tests.
*these things have virtually no vapor pressure, and considerbale dipoles. As such they can be flash heated to great temperatures very quickly using a microwave! Watch it though, the violent boiling results from the flash boiling of the water evolved during the esterification (which is good, because it cannot reverse the reaction and bad, as it is a pain-in-the-ass to clean the stuff up when it spews everywhere).

The burning let's you know it's working:D,

O3

Jome - 28-11-2006 at 17:27

Most likely if biodiesel became economically feasible it would be based on algae-oil, something like caulerpa taxifolia (yes, killer algae) that kind of source beats everything else by a factor of ten.

Ideally, other parts of the plant would suffice both to be turned into CO and then the spare energy from burning the rest would be enough to make this into the methanol needed in the BD synthesis.

Therefore, the other chemical roles of old-time petroleum should be what we are after, such as lubricants, waxes, starting materials for plastics... Could perhaps a benzene ring be made from glycerol? That'd be immensely useful since most of those today come from petroleum.

[Edited on 29-11-2006 by Jome]

Tacho - 29-11-2006 at 02:38

If pyruvic acid can be turned into ethanol by yeast and glycerol is substantially cheaper than ethanol, then the glycerol-zinc path sounds very interesting.

Very interesting indeed. Thanks Organikum.

Ozone - 29-11-2006 at 17:13

Good day all!

Jome,

That is more or less what I am after--The means to produce chemical feedstocks from sources other than petroleum. For benzene rings, though, I would go after the lignin byproducts derived from pretreatment of biomass for cellulosic ethanol, or, from the paper industry. The average US sugar mill, for example, would produce ~70 tons (2000lb/ton) per day, if it were to be making cellulosic ethanol.

What is the mass balence for this algae you describe? Removing lots of water requires dealing with much latent heat and larger energy expenses. Still, good idea! Recycling the unused portions for fuel is always a winner (until you figure out something more lucrative to do with it)!

Attached are some pictures of the poly-glycerolcitrate amd the crystals I got from the crazy ionic liquid.

Cheers,

O3

[Edited on 30-11-2006 by Ozone]

p-glycerolcitrate panel_112906_small.jpg - 119kB

Tacho - 30-11-2006 at 08:21

Thank you not_important, I can see why I didn't get any thickening. I'll try oxalic acic. It will probably generate long chain polymers.

Ozone, removing water is not an issue in hot countries where there is plenty of sun. Nice pictures btw, thanks.

Twospoons - 30-11-2006 at 19:27

For a truly off-the-wall idea, how about using it in high altitude smoke machines, generating aerosols to combat global warming. And make pretty sunsets.

DeAdFX - 30-11-2006 at 20:34

I was just thinking.... Is it possible to oxidize the acrolein into glyoxal? The structures look pretty similar except glyoxal has an extra oxygen atom.

not_important - 30-11-2006 at 21:46

Acrolein is 3 carbons, glyoxal is 2; unless you meant oxidative cleavage. Ozone will cleave the double bond, if worked up under reducing conditions you'll get the aldehyde.

An alternative would be to oxidise one of the primary hydroxyl groups to the aldehyde, then cleave the remaining diol functionality with periodic acid.

I think that neither would be cost competative with the established routes to glyoxal.

Jome - 1-12-2006 at 08:39

Caulerpa taxifolia is a "macro algae" and consists of 60 mass percent oil, according to references I can't seem to find at the moment. I did a small essay on it in college (eq.). It's mentioned in Wikipedia, but I acknowledge that's not a good source.

Caulerpa taxifolia apparently reproduces extremely fast and is only eaten by very few organisms. Aquarium bred strains with the capability of surviving in subtropic (instead of tropic) waters where there is no natural enemy has led to the name "killer algae", it simply outbreeds everything else.

I'm thinking of something like a floating factory-platform (in tropical waters) and hydrostats* floating in a radial pattern a few hundred meters out from it, with the algae growing on these, simply pulled in when it's time to harvest.

*Device that "stands still" at a certain depth in water.

Tacho - 1-12-2006 at 09:42

Jome, are you saying that for every 100kg of dry algi we have 60kg of some triglyceride?

Could somebody confirm that? That would be THE most impressive thing I've heard lately.

Ozone - 4-12-2006 at 17:12

Hello all,

Attached is a paper giving the fatty acid breakdown of C. taxifolia. Unfortunately, they do not give the simple mass balance. Their numbers are reported as % on total fatty acid, of this some 45.2-73.6% are unsaturates, principally C16 (hexadecanoic or palmitic acid).

Another page, though, gives the following:

"...1.3% on fresh weight caulerpenyne (the active toxicant in the algae) or greater than 2% on dry weight."

http://www.sbg.ac.at/ipk/avstudio/pierofun/ct/ct-4.htm

This seems to indicate a moisture content of only ~50%. I this is the case, I would expect low cellulose and lignin (algae is not designed to stand upright in a gale). So, on this, certainly no more than say, 50% lipid would likely be found. This would still be a highly significant, profligate source, though.

Ah, here's some more info:

http://www.abovetopsecret.com/forum/thread198590/pg1
http://www.americanenergyindependence.com/biodiesel.html

I will attach the large NREL algae program report on the next post. It appears from this that, from certain strains, 50% or more (on biomass) of lipid can be obtained from algae...*amazing*.

Still, with all of that algae growing off-shore, we will sure be making one hell-of-a-lot of glycerol...

Happy Motoring,

O3

Attachment: C taxifolia_01.pdf (184kB)
This file has been downloaded 1253 times

Ozone - 4-12-2006 at 17:13

The NREL report for reading on the crapper!

O3

Twospoons - 4-12-2006 at 19:35

A more viable use might be as a fuel in fuel cells. Methanol, ethanol, and ethylene glycol can all be used in direct liquid fuel cells - so I'd imagine glycerol could be too.

chemrox - 10-2-2007 at 15:10

What is a macro algae? I think of kelp which is easily harvested. The ease of harvest is due not only to its size but its habitat along the coast, almost inshore....

Where does C. taxifolia live?

chemrox - 10-2-2007 at 15:13

Caulerpa taxifolia is a threat to the marine environment and is the subject of numerous eradication related articles (Google it). Perfect for biofuel projects!

Ozone - 10-2-2007 at 21:39

Hello all,

I keep trying to upload that NREL file (it's about 3Mb), but to no avail!

Micro=single cells (blue-greeners and friends)
Macro=organism constructed of single cells (kelp)

Unfortunately, the kelp is very high on the "moisture % biomass" end, and requires a lot of energy in drying (latent heat is heat when calculating fuel value). I do not mean a small scale operation whereby the material is dried in the sun. I am referring to a 3.5E10 gal (a Curie of fuel, in gallons, WOW, or ~1.3E11 L) of renewable liquid fuel by 2015. The biomass must be amenable to immediate processing with minimal pretreatment!

Although this is practically impossible, the algae route makes it at least worthy of discussion over beers (with the occasional napkin).

Sauron started another thread that I think is relevant to this discussion (that is, interesting things to do with glycerin):

http://www.sciencemadness.org/talk/viewthread.php?tid=7544

Where he pointed out the utility of HCl(g) which makes chlorination of the primary (1 and 3) positions feasible (in liquid phase the Sn1 predominates resulting in chlorination of the 2-position).

Still... I quote, "with all of that algae growing off-shore, we will sure be making one hell-of-a-lot of glycerol".

Cheers,

O3

Sauron - 10-2-2007 at 22:01

Triacetyl glycerin, or glycerol triacetate is a common industrial chemical called triacetin.

@O3, did you try my idea from another thread about oxidizing the center -OH of glycerol selectively with TCCA to form 1,3-acetonediol and then using TCT/DMF to chlorinate that to either chloroacetone or to sym-dichloroacetone?

Those are nasty unpleasant compounds (my specialty it seems) but of industrial significance (like acrolein).

Normally you'd use dry HCl to chlorinate glycerol to 1,3-dichloroglycerol then oxidize the remaining hydroxyl to carbonyl. Perfectly practicable and well trod, the new route just appears to be easier (avoids all that HCl generation). If it works of course.

[Edited on 11-2-2007 by Sauron]

Sauron - 10-2-2007 at 22:31

If you use dry HCl on liquid glycerin you never chlorinate anything but the 1 and 3 position (or at least, very rarely).

And if you oxidize glycerin with TCCA you will selectively transform only the 2-position to carbonyl, never forming any aldehyde.

(The rates being so different that stopping when all the 2 -OH has been oxidized does not allow time for aldehyde formation at 1 or 3.)

Those are first step in two different schemes, not same scheme, althpough you could combine then and use TCCA to oxidize 1,3-dichloropropane rather than the classical method.

Remember, TCCA is one of those reagents (too few) that are effectively recyclable. The cyanuric acid precipitated, can be chlorinated back to trichloroisocyanuric acid.

TCT also produces cyanuric acid quantitatively if all three of its chlorines are hydrolyzed, but AFAIK it is not so easy to reverse that. I think oxalyl chloride works for that but it's too costly to be practical for this purpose, it's far cheaper to depend on the cheap industrial process to make TCT from HCN and HCl (it's the trimer of cyanogen chloride.)

Ozone - 10-2-2007 at 23:00

Thanks Sauron, this is true!

Glycerol esters are viable products (as are the wacky ones I working on), but, my personal concern is...If we produce 35E9 gallons of, say, biodiesel (very simplistic, know, but I'm just making an example), well let's see...

With an average molecular weight of ~298 g/mol (ethyl stearate, glycerol is ~92 and stearic acid is ~284 g/m ol), assuming 3.5E10 gallons means 1.33E11L (which is approximately the same by weight as the density is very close to 1 g/cm3) some 1.7E12 moles of the ester or...5.7E11 moles of glycerol. This is amounts to about 5.7E7 tons (1 ton = 909kg or 2000lb).

By the gods that's a shitload,

O3

Sauron - 10-2-2007 at 23:16

@O3, I suspect biodiesel (like fuel ethanol) are at worst fads and at best small niches in the overall energy economy. Presently in fashion because they are allegedly "green" and "sustainable and mostly so the politicians can make the farmers and esp the agroindustry salivate over subsidies.

Back to TCT, which gives cyanuric acid as a waste product, while it can't be so easily cycled back into TCT it can be easily chlorinated back to TCCA and this is a definite plus in its favor.

Ozone - 11-2-2007 at 09:10

There is no doubt of that! It is a stop-gap at best. At the current goal level, we would be seeing ~11E9 gallons of fuel, this equates to roughly 1/4 of viable agrispace in the country. Cranking this up to 35E9 required roughly 3 times more agrispace, at the behest of food.

Mexico is operating as the canary in the mine (no offense) since the economy there is fragile (and corn is a primary foodstuff) enough to feel this fuel vs food dichotomy. A tiny shift in the trade value on commodity corn = more expensive tortillas.

This will happen here as well if more sensible alternatives are not persued. We need to look into cellulosic ethanol made from agriwaste and split stream that to say, make ethyl-algae-biodiesel. The current methods will be with us for a while though since industrial inertia is difficult to surmount.

Any process with the potential to back process is good. It seems to me that the cyanuric acid itself could be a product as well. How about going from cyanuric acid to atrazine? The oxidations required should be feasible electrochemically (now to make it cheaper than condensing HCN/cyanic acid).

Cheers,

O3

not_important - 11-2-2007 at 11:02

I think that simply switching back to using glycerol in existing applications can soak up a lot of the production. Industry moved away from it as petrochemicals became more widely produced.

Glycerol can be used as a sweetener, one that doesn't promote plaque forming bacteria. It can replace propylene glycol, which displaced glycerol, in many food and medical applications.

Fermentation processes can be used to convert glycerol to 1,3 propylene diol. It can be used in deicing fluids, where it replaces the toxic ethylene glycol. Other fermentations produce chiefly propionic acid with smaller amounts of succinic and acetic acids; different bacteria will chiefy produce succinic acid, or formic acid and ethanol.

Ozone - 11-2-2007 at 12:28

Indeed. Good call, not_important!

Here is a nice biodeisel blog:
http://www.trianglebiofuels.com/blog/index.php?paged=2

From here is quoted:

Columbia, Missouri - In addition to topping off your gas tank with biodiesel, a new advance could let you fill your vehicle’s cooling system with a biomass-derived antifreeze. A new process developed at the University of Missouri-Columbia (MU) creates a valuable secondary product from the biodiesel manufacturing process that makes the production cycle both profitable and affordable.

Galen Suppes, chief science officer of the MU-based Renewable Alternatives, developed a process for converting glycerin, a byproduct of the biodiesel production process, into propylene glycol, which can be used as nontoxic antifreeze for automobiles. Suppes said the new propylene glycol product will meet every performance standard, is made from domestic soybeans and is nontoxic.

Suppes said this technology can reduce the cost of biodiesel production by as much as $0.40 per gallon of biodiesel. The market for propylene glycol already is established, with a billion pounds produced a year.

“The price of propylene glycol is quite high while glycerin’s price is low, so based on the low cost of feed stock and high value of propylene glycol, the process appears to be most profitable,” Suppes said. “The consumers want antifreeze that is both renewable and made from biomass rather than petroleum from which propylene glycol currently is produced.”

The creation of a valuable secondary product could help mainstream the use of biodiesel. In 2004, biodiesel producers sold 30 million gallons of fuel, up from 500,000 gallons in 1999. It’s still, however, a relatively niche fuel.

“At best, right now biodiesel production is only part of the solution,” Suppes said. “Current biodiesel production in the United States is about 0.03 billion gallons per year as compared to distillate fuel oil consumption of 57 billion gallons per year.”

Renewable Alternatives is currently licensing this technology to three biodiesel plants. The National Science Foundation and Missouri Soybean Farmers are helping to fund the research.

Definitely an option!

O3

[Edited on 11-2-2007 by Ozone]

Glycerol fermentation.

Welder - 13-1-2008 at 01:22

Hello everyone.

I'm only a humble tradesman (welder), not a scientist, but I joined this forum hoping that more chemically competant folks could help advise me on chemistry issues. I'm predominantly interested in biofuels issues, but may need help in other chemical specialties as well.

Anyway, I read most of this thread and although I understood a lot of it, there were also many areas where I just couldn't follow strongly along. I understand that the thread started out trying to find profitable, viable ways to use biodiesel brewing byproduct (glycerol), but near the end it was pointed out that there may be existing uses that have been abandoned in favour of other more viable chemical substitutes. For example, it was mentioned that glycerol can be used as a sweetener or after conversion to propylene glycol it may be used in place of the more toxic ethylene glycol.

My question is regarding the potential of using glycerol as feedstock in ethanol fermentation.

Can glycerol be profitably fermented to produce cheap ethanol? By cheap, I don't mean cheaper than cellulosic ethanol, but cheaper than grain ethanol.

If glycerol can be used to ferment and distill anhydrous ethanol, it may be a practical co-solvent along with methanol in transesterification. It could be produced on-site wherever larger commercial biodiesel breweries can afford to run an ethanol brewery/distillery and combine their own ethanol with purchased methanol.

If what I propose is technically viable, it is likely more practical than a biodiesel brewery using their glycerol to feed their own in-house methane digesters and then using the methane as process heat, or converting it into methanol as process solvent.

Any input?

not_important - 13-1-2008 at 21:42

There's been a lot of effort put into finding useful and practical fermentations of glycerol; a few have been developed in the last couple of years.

There's other uses for some of the glycerol in regards to biodiesel. Convert some ethanol to acetaldehyde and react that with glycerol to for the cyclic acetals, which are useful as oxygenates in the biodiesel.

Remember that there is very roughly 16 times as much carbon in the fatty acids part of oils as in the glycerol part. This means that while increasing the utility of the glycerol, it's not going to be a big boost in fuel production.

One problem with fermenting the glycerol wastes from based catalysed do-it-in-the-basement biofuels is that the salt content inhibited fermentation. Going to acid catalysed transesterfication using reactive distillation eliminates the salt problem. It also allows the use of feedstocks with considerable amounts of free fatty acids, meaning waste/used oils and fats can be used. For the US the amount of waste oils from industrial and commercial users would allow the production of biodiesel amounting to 5 to 10 percent of the current fuel consumption of the US.

Two references, the first is

doi:10.1016/j.copbio.2007.05.002
Current Opinion in Biotechnology
Volume 18, Issue 3, June 2007, Pages 213-219

Anaerobic fermentation of glycerol: a path to economic viability for the biofuels industry

Syed Shams Yazdania and Ramon Gonzaleza

and the second is the attached PDF

Attachment: Hydrogen and Ethanol Production from Glycerol Wastes.pdf (354kB)
This file has been downloaded 2147 times

Welder - 14-1-2008 at 04:28

Thank you very_important. I really appreciate your informative reply. It's nice having some friendly and chemically competant guidance.

I'll pass the info you gave along to the other biofuels people I know. If glycerol based ethanol production is an economically viable way of disposing of biodiesel produced glycerol, then perhaps some small commercial biodieselers I know may test it in their operations.



I don't really want to take this thread off topic, but I have two other biofuels related questions:

Although I think biodiesel is a great fuel and fuel additive, lately I've been looking into a biofuel option called SVO. The acronym SVO stands for straight vegetable oil. Basically, instead of transesterfication, vegetable oils are heat thinned until the viscosity approaches that of diesel oil. This is typically accomplished on board through the use of heat exchangers tapping waste engine coolat heat as well as supplementary electric heating.

Anyway, most svo users are actually burning WVO (waste vegetable oil) recieved from restaurants. This supplies the svo/wvo users with cheap fuel, but the quality of wvo varies widely and significant refinement is required to come up with a usable fuel.

Aside from filtering out food particles and washing away salts, sugars and water based acids, the WVO users are also faced with free fatty acids, as you already mentioned earlier regarding used oils.

Although FFAs are an issue for home biodiesel brewers using WVO as feedstock, most svo users simply ignore the FFAs and just burn the WVO along with the FFAs already present.

My first question relates to the potential of fuel system corrosion in WVO fuelled vehicles. Some WVO users think FFAs are acidic enough to corrode the steel injection pumps and injectors while others feel that FFAs aren't acidic enough to do any damage, even over long-tern exposure. If WVO has been filtered down to 1 micron and has also been water washed to remove salts, sugars and water based acids, then dewatered to less than 700 PPM, is there still a significant risk of corrosive action from the FFAs being in long term contact with steel fuel system components? Simply restated, are FFAs corrosive to steel?

Those who feel that FFAs pose no corrosive threat to injection systems believe that reports of corrosion are more likely related to inadequate dewatering and/or failure to water wash the salts and water based acids from WVO. As salts, sugars and water based acids are hygroscopic, miost air drawn into a fuel tank as the fuel level drops could easilly condense on fel tank walls and dribble down into the WVO making salt residue and previously dehydrated water based acids more corrosive.

If FFAs are not corrosive to regular steel, then they can likely be left in WVO and burned as fuel.





My second question is regarding polymerization. Again, due to economics, WVO is the material in question. As I understand it, polymerization of WVO starts in the fryer due to heat and exposure to oxygen and possibly metal ions acting catalytically. I've heard that unless the oil is damaged by oxygen, it won't likely polymerize. There are a number of potentially suitable antioxidants to use as vegetable fuel stabilizers so I won't ask you to recommend any, but lately I've heard of fairly extreme examples of polymerization occurring in WVO bearing high levels of FFAs. I assume the FFAs are elevated due to greater use before being discarded into the waste oil bin, but I'm not sure if there are any other causes of FFA formation, or if higher FFA levels mean a greater likelyhood of WVO polymerization. I also am unaware of whether or not antioxidants can help prevent FFAs from polymerizing, or even whether or not FFAs even polymerize at all.

Do you think antioxidants or any other potential fuel additive may likely help prevent FFAs from polymerizing?

Thank you in advance for any advice you may have.

not_important - 14-1-2008 at 23:41

Not an area that I've experience in, but I've read on it.

The FFA problem seems to be real. The mention here http://journeytoforever.org/biodiesel_svo.html#gnl matches what I've heard elsewhere - pump corrosion can be a problem. Water is likely an important factor, really drying the oil will take some work. Di- and mono-glycerides in the oil may draw in some water too, undoing the drying. And even dry fatty acids are still acid and can attack metals.

Polymerisation is quicker when hot, but proceeds at any normal temperature. It's the same as the drying oils used to make oil-based paint, those are more unsaturated than food oils but the process is the same. And as the unsaturation is in the fatty acid part of the oil, the free acids will polymerise as well. Water wash, chelating agents to inactivate traces of metal ions, and anti-oxidants all help.

A third issue that you mention is the viscosity, vegetable oils at 80 C still have a much higher viscosity than diesel. The temperature needed varies from source to source, I've seen numbers ranging from 110 to 150 C to reach compatible viscosities.

My personal opinion is that going the transesterfication route to biodiesel, using the glycerol to build oxygenates and thinners for the simple biodiesel esters, and perhaps convert some to mono-alcohols, is the best bet. Using reactive distillation ordinary rendering methods can be used to strip the feedstocks of salts and other water solubles, there's no need to dry the oils, and you cam mix the oil with the esterfication alcohols to make the filtering stages easier.

Welder - 15-1-2008 at 04:02

Thanks again for replying.

Drying WVO has been a challenge, but a WVO user named Sunwizard has proven that by using cheap automotive centrifuges (CF), adequate dewatering is possible. Of course settling and decanting preceed the CFing of the WVO, but the CF has proven to do the job acceptably.

Of particulat interest to me is your mention that FFAs are the unsaturated part of the oil. Does this mean that FFAs can be saturated chemically, such as through hydrogenation? If so, then I would wonder if hydrogenated fatty acids would still be able to corrode steel or not?

Wouldn't saturation via hydrogenation make a more stable and less corrosive molecule? Don't worry, I know trans fats are not healthy to eat, but as completely combusted fuel they should be safe...and carbon neutral!

I understood your advice steering me toward transesterification, but with methanol being a dangerous and expensive factor in biodiesel production, I'd rather perfect running diesel engines on free WVO. Methanol isn't free, but WVO usually is



[Edited on 15-1-2008 by Welder]

[Edited on 15-1-2008 by Welder]

not_important - 15-1-2008 at 08:20

Saturation brings higher melting points and increased viscosity problems - you end up with shortening instead of oil. Won't affect their ability to work as acids.

It's the fatty acids, free or esterified with glycerol or methanol, that are unsaturated. Both the free and esterified acids can polymerise. Used oil also likely has had some acrolein formed, and that easily polymerises to gorp as well as forming lighter weight water extractable acids. The free acids are likely to increase corrosion, bringing fresh metal ions into the oil, making polymerisation more likely.

How bad the corrosion problem with dried WVO is will take field experience to learn, the sample size is rather small right now and the sample population has a lot of boosters who tend to overlook problems they may meet. Water certainly makes things worse, I believe the real question will be in regards to how much water tends to accumulate in the processed oil.

WVO may be free or very low in cost, but the processing and modifications to the vehicle add to that. Replacing stressed or corroded parts adds even more cost. I must also comment that "...4 passes seems to get most of the particles out, so it takes 2-3 hours for a 40-50 gallon batch." That's filtering hot oil, which also means additional costs in the heating and pumping, and spending time doing the work - time that isn't included in the costs.

This reminds me so much of the late `60s through mid `70s, with people building housing out of metal sheet from abandoned automobiles, cut open and flatted drink cans, and so on. The problems with leaky roofs in the rainy season tended to to be discussed nearly as much as the joys of those alternative sources of building supplies. There's alway been the tinkerers, often putting more effort into their alternative methods than they'd expend to buy the mainstream item, just as there's been hobos and the like, avoiding settling down into a conventional life. Fine and good, but hardly a solution for society at large.

And not a low cost solution likely to last, as cheap WVO will become something of value. A friend was describing a grocery store that fueled their backup generator with diesel to get the engine up to heat, and WVO after that. They buy the WVO from someone who has sewn up most of the larger producers of WVO in the area, partially by switching to paying a small amount for the oil rather than just hauling it off. Cleans the oil up in a plant built for the task. That guy is in competition with the biodiesel people for VO supplies, as petroleum prices go up they may be getting in bidding wars for the WVO. And leaves the amateur SVO crowd hunting for their stocks from the smaller producers of WVO, the ones where it's not worth the big players time to collect a couple of gallons of WVO a week from.

Welder - 15-1-2008 at 14:23

The higher melting poiints and increased viscosity aren't a problem as many folks have found success running on lard, tallow, and palm oil. The key is to start the engine on either biodiesel or petrodiesel and tap into the waste engine heat to liquify the solid fuel.

I thought that saturating the WVO through the use of an indusrial enzymatic hydrogentor (available by lease) would help prevent polymerization. Saturated oils don't easilly polymerise, do they?

The conversion costs of preparing a diesel vehicle to SVO/WVO operation are a one-time cost, while methanol is a substantial recurring cost to biodiesel brewers. A local engineer I know brews biodiesel for about 35-46 cents/gallon. The costs to adequately dewater esters or WVO are the same. Esters may dewater more easilly due to the reduced viscosity, but since heat is required in both instances, the difference is unimportant. A kilowatt hour of heating and centrifuge pumping costs the same regardless of fluid processed.

Yes, biodiesel is easier than WVO/SVO, but petrodiesel is easier still. Out of the three, SVO/WVO is cheapest by far, providing that corrosion and other obstacles don't bring repair costs onto the ledger. That's why I'm asking these questions, I'm trying to bring SVO/WVO into a point of full maturity in the same way that biodiesel people worked over their problems in the early days of biodiesel.

While there are never WVO refinery explosions, there have been a substantial number of biodiesel breweries that have suffered fires and/or explosions. Safety and economy favour SVO/WVO.

Yes, the bidding wars will inevitably come. Staying ahead of the pack is the key to sustainability there.

microcosmicus - 15-1-2008 at 14:31

To follow up points being raised above and see how important vegetable
oil might be in the grand scheme of things, I had a look at some data.
While these may not be the best numbers, they should at least be good
enough for back-of-the envelope estimation.

The total world production of vegetable oil is 5.5E10 kg per annum
(http://findarticles.com/p/articles/mi_m3819/is_1991_July/ai_...)

The total world production of petroleum is something like 2.3E10 barrels
per annum (http://www.eia.doe.gov/emeu/cabs/topworldtables1_2.htm)

Each barrel yields 74L of gasoline.

Given that gasoline has a density of 0.68 g/cc, that all amounts to
something like 1.1E12 kg gasoline per annum.

So it seems that, whilst vegetable oil alone cannot do as
an alternative fuel, there is at least a large niche market.
Quote:

WVO may be free or very low in cost, but the processing and modifications to the vehicle add to that. Replacing stressed or corroded parts adds even more cost. I must also comment that "...4 passes seems to get most of the particles out, so it takes 2-3 hours for a 40-50 gallon batch." That's filtering hot oil, which also means additional costs in the heating and pumping, and spending time doing the work - time that isn't included in the costs.


Of course, the energy needed to heat the oil so as to filter it can come
from burning the oil, so that can be calculated into the yield.

Should this yield be unacceptably low, there are applications
less demanding than internal combustion engines where minimally
purified oil will do just fine. For instance, look at the waste oil
burner which Lionel Oliver uses to melt metal:

http://www.backyardmetalcasting.com/oilburners01.html
http://www.backyardmetalcasting.com/oilburners02.html

I could imagine a similarly designed burner used for home heating or
for boiling steam to run a turbine and generate power.

Sure, the fatty acids are going to be as corrosive, but the costs are going
to be smaller if one is dealing with a simple burner than an engine. Because
the parts need not be as precise, they will cost less and can take more
abuse from corrosion before needing replacement.

Welder - 16-1-2008 at 04:49

Hi Microcosmicus.

I agree that the obstacles to using WVO as heater fuel are less than those pertaining to auto fuel, but although I certainly plant to build a WVO boiler/furnace eventually, for now, I want to reduce my auto fuel costs.

As mentioned earlier, there are industrial enzymatic hydrogenators available for lease, but I can't seem to find the source. I know I read the article somewhere, I'll just have to keep searching. I'm assuming of course, that hydrogenating filtered/dewatered WVO will reduce the polymerization activity of the WVO cheaper or more effectively than an antioxidant would.

Is there any way to de-acidify the FFAs without having to make them into soaps? If not, would such FFA soaps make safe, envirinmentally friendly fuel? I hear of biodiesel brewers converting their FFAs to biodiesel through a process called an acid-base reaction (at least I think that's the term). Biodiesel is great, but I'm just trying to avoid requiring methanol in the production of a cheap, reliable and sustainable biofuel.

Even if FFA soaps are highly hygroscopic, that's no problem as long as they are still flammable liquids when fully dried. ASVO/WVO users are comfortable with extensive modifications so dessicant breather on the fuel tank can prevent water contamination affordably.

Any other ideas?

microcosmicus - 16-1-2008 at 09:07

Hi Welder,

Sorry if I came across in a negative way --- it was not my intention to
rain on your parade. Unless people try things out, however implausible
they might seem, there is not going to be any progress in science or
technology. Rather, all I intended was to point out that, even in the worse
case scenario where processes for converting waste oil to IC engine
fuel turn out to be too costly, there are still uses for WVO as a fuel.
Having said that, I wish you luck with your research and hope that things
turn out better than the worst case scenario.

As for what to do about fatty acids, here is a thought . Would an strongly basic ion
exchange resin remove them? Since the acids are not going to be dissociated
in oil solution, maybe not, does someone here know for sure? If so, then one
could first pass the oil through an ion exchange column and then a dessicator
to remove the water from neutralization as well as moisture already in the oil.

Maybe one could adapt the procedure the brewers use to neutralize their product,
but using the resin in place of alkali or at least look to that process for inspiration.

Fatty acid soap dissoved in oil is the recipe for grease. Burning the
soap would have the problem that it will form ash just like when burning wood.

not_important - 16-1-2008 at 09:20

Again, hydrogenation increases the melting point of the oil - turns it into Crisco.

Soaps are neutralised fatty acids, the common and low cost bases give soaps. Soaps based on metallic elements result in the formation of the oxides of those metals when the fuel is burned, in most cases not good for the engine. Ammonium and amine soaps don't have this problems, but form NOx.

The soaps tend to be solids or pastes, higher viscosity and melting point than the FFA or glycerol esters (fats) of those fatty acids. Clogging of the fuel system could be a problem, and water that gets in will tend to form emulsions and foams with the soaps.

That biodiesel use of FFA is likely acid based or acid catalysed esterification, giving the same esters the standard base catalysed route does. Because the catalyst is also an acid, it doesn't react with the FFA the way alkaline catalysts do. Current thrust with acid catalysts is toward reactive distillation, fractional distillation with the acidic catalyst as part of the fractionating column packing. This can give near 100% conversion, handle wet feedstocks giving dry product, and gives high quality glycerol (able to be used in fermentation without further cleanup); all with no waste salts production - unlike most base catalysed routes.

Ethanol can be used in place of methanol, and methanol can be made from CO2 and H2 - either from electrolysis using 'green' power or possibly by direct electrochemical routes using CO2 and water.

not_important - 16-1-2008 at 09:24

Quote:
Originally posted by microcosmicus
...
As for what to do about fatty acids, here is a thought . Would an strongly basic ion
exchange resin remove them? ...


Yes, but then you have the cost of the resin, it's regeneration, and the disposal of the FFA effluent from them in what is likely to be a mostly alcohol solution of FFA soaps and excess base.

[Edited on 16-1-2008 by not_important]

microcosmicus - 16-1-2008 at 11:48

Let me start with a question --- what is the concentration of fatty acids
in a typical batch of waste oil?

While it's hard to say too much without such a figure in hand, here are
some tentative possibilities.

The cost of the resin is offset by the fact that it is regenerated. In the
long run, all one pays for is the cost of replacing resin which has been
worn out. The figure I usually see cited here is that a resin is usually
good for a few years or so due the stability issues.

As for the remains of regeneneration, couldn't one regenerate using
an aqueous solution and avoid the alcohol? However, if there needs
to be alcohol, maybe reclaim it by distillation for reuse in the procedure.
Of course, alcohols + base make EtOX,. so there may be problems with that.

Also, I have read that organic acids (tannic acid has been specifically cited)
can foul resins by dissolving inside the bead. However, since the solution
for this problem was regeneration with a base like NaOH, that might only
be a problem in applications like water softeners where one would prefer not
to use strong base. A more serious problem is clogging of resins with oil ---
that might blow this suggestion of using ion exchangers for oil out of the water.

http://www.sybronchemicals.com/service/pdf/reprints/Maintain...

Soaps and excess base don't sound like a liability to me. Add extra oil
to saponify the excess base and sell the soap.

[Edited on 16-1-2008 by microcosmicus]

Welder - 17-1-2008 at 04:50

Hi guys. Thanks for your continued interest in the problems I've mentioned.

Lime seems to be the best bet for creating insoluble FFA soaps. I assume that drying the WVO after saponifying the FFAs will cause them to conglomerate and fall out, right? I'm hoping it should at least make it easier to spin the FFA soaps out in a centrifuge rotor. The FFA soaps will dry into solids right?

not_important - 17-1-2008 at 08:30

The calcium soaps are usually described as "fatty powders", fairly soft and friable. I believe they also disperse fairly well in warm oils; if so that could present problems. On the other hand, that centrifuges are being used to dry the oil might result in the soaps sticking to the water droplets and separating nicely - experiment time.

A possibly problem with using 'lime', either CaCO3 or Ca(OH)2, is that you're forming a solid product in a reaction with a solid reactant. This would seem likely to result in the lime being quickly coated in calcium soaps, slowing down the reaction and requiring more lime.

The limit on FFA for VO fuel seems to be 0,5%, while the amount of FFA in WVO is typically several percent and can run as high as 5% in the overused oils typical from small producers who try to squeeze as much use out of the oil as they can.

That "acid-base reaction" may be a method where an acidic catalyst is used to esterify the FFA, then a basic catalyst is used to do the transesterification of the glycerol esters - the fats. The complexity of that is in part what has been driving the research in reactive distillation.


The solubilization of calcium soaps by fatty acids
Journal Lipids
Publisher Springer Berlin / Heidelberg
ISSN 0024-4201 (Print) 1558-9307 (Online)
Issue Volume 26, Number 3 / March, 1991
Category Communications
DOI 10.1007/BF02543981
Pages 250-253
Quote:
The solubilization of the calcium soaps of long chain fatty acids by liquid fatty acids was observed. The solubilities of calcium palmitate, calcium laurate, and calcium oleate were 15.6, 22.8, and 53.3 wt%, respectively, in oleic acid at 40°C. The formation of an acid-calcium soap complex was demonstrated by x-ray diffraction studies of calcium laurate, lauric acid, and a mixture of these compounds that had been heated. Similar evidence was obtained for a calcium oleate-oleic acid complex. The solubility of calcium oleate in a bile salt micellar system was enhanced by obeic acid. The solubilization of calcium soaps by liquid fatty acids may explain the unexpectedly high bioavailability of some calcium soaps.

Welder - 17-1-2008 at 13:04

Quote:
Originally posted by not_important
The calcium soaps are usually described as "fatty powders", fairly soft and friable. I believe they also disperse fairly well in warm oils; if so that could present problems. On the other hand, that centrifuges are being used to dry the oil might result in the soaps sticking to the water droplets and separating nicely - experiment time.

A possibly problem with using 'lime', either CaCO3 or Ca(OH)2, is that you're forming a solid product in a reaction with a solid reactant. This would seem likely to result in the lime being quickly coated in calcium soaps, slowing down the reaction and requiring more lime.

The limit on FFA for VO fuel seems to be 0,5%, while the amount of FFA in WVO is typically several percent and can run as high as 5% in the overused oils typical from small producers who try to squeeze as much use out of the oil as they can.

That "acid-base reaction" may be a method where an acidic catalyst is used to esterify the FFA, then a basic catalyst is used to do the transesterification of the glycerol esters - the fats. The complexity of that is in part what has been driving the research in reactive distillation.


The solubilization of calcium soaps by fatty acids
Journal Lipids
Publisher Springer Berlin / Heidelberg
ISSN 0024-4201 (Print) 1558-9307 (Online)
Issue Volume 26, Number 3 / March, 1991
Category Communications
DOI 10.1007/BF02543981
Pages 250-253

Quote:
The solubilization of the calcium soaps of long chain fatty acids by liquid fatty acids was observed. The solubilities of calcium palmitate, calcium laurate, and calcium oleate were 15.6, 22.8, and 53.3 wt%, respectively, in oleic acid at 40°C. The formation of an acid-calcium soap complex was demonstrated by x-ray diffraction studies of calcium laurate, lauric acid, and a mixture of these compounds that had been heated. Similar evidence was obtained for a calcium oleate-oleic acid complex. The solubility of calcium oleate in a bile salt micellar system was enhanced by obeic acid. The solubilization of calcium soaps by liquid fatty acids may explain the unexpectedly high bioavailability of some calcium soaps.


Good info, Important! Thanks!

What about saponifying the FFAs with lye? I understand that the risk involved there is that loss of oil may result due to the lye indiscriminately saponifying anything it touches.

Is there any way to make lye saponification target the FFAs more accurrately? Maybe less lye diluted in more water?

[Edited on 17-1-2008 by Welder]

12AX7 - 17-1-2008 at 13:07

Sodium carbonate?

Typical carboxylic acid pKa ~ 5, CO3(2-) ~ 10...

Running through a bed of soda ash would probably do it.

Tim

Ozone - 17-1-2008 at 17:41

Good evening!

It's been a while since I have had time to post.

You can wash the oil with potassium carbonate (soda ash will likely work too) solution. The K salt will extract into the aqueous layer where it can be separated. This method can also be used to remove organic acids from their "parent" aldehydes (so you can use that ancient aldehyde found in your graduate lab:)).

I have made Calcium "lardate" from lard (Armour brand manteca) and Ca(OH)2 at reflux (the solubility is poor and the rxn is slow) for about 4 hr. The resulting mess can be extracted with hexane from which the (mostly) calcium distearate can be recrystallized. It is a white powder, sparingly soluble in water, without suds. It is, however, an excellent antifoam agent (which is what I made it for, and it can break hydrogels).

We routinely run organic acid analysis on an anion exchange column eluted with a NaOH gradient (but this is done from aqueous media). But...Oil will absolutely trash (foul) your resin. no go.

I (et al) have made some notes regarding baterial fermentation of glycerol here:

http://www.sciencemadness.org/talk/viewthread.php?tid=9557&a...

Please see, specifically, the Gonzalez group paper (Rice), which I posted there (IIRC).

Cheers,

O3

Welder - 18-1-2008 at 05:08

[Edited on 25-1-2008 by Welder]

Welder - 25-1-2008 at 17:38

Hi again.

So I just wanted to make sure which reagent would be best to creat non soluble FFA soaps that will dry when heated under vacuum then seperate easilly in a centrifuge.

Would it make sense to try calcium hydroxide? Would calcium carbonate diluted in water be better?

I'm not sure whether I'm understanding this properly.

When it was mentioned that it was possible to make non soluble soaps from FFAs, I thought that would be good in order to avoid creating soluble soaps that might emulsify with the used oil and any excess water making removal more difficult. Does this make sense, or are non soluble soaps likely to be difficult to seperate from the WVO?

microcosmicus - 25-1-2008 at 18:43

Lubricating grease is made by mixing calcium soap with oil. Given that
the soap in this type of grease does separate out when heated, your
method might work. According to the following reference, it seems
that the grease starts drying out at 160F, presumably the vacuum
would lower the temperature significantly:

http://www.reliabilityweb.com/art04/understanding_grease.htm

However, bear in mind that the usual grease has the soap dissolved
in mineral oil, not vegetable oil, so things might not go exactly
the same way. However, your idea sounds like its worth a shot.

Calcium carbonate only dissolves in water in trace amounts (14 mg
per liter, to be precise). Given that hard water is basically a solution
of calcium carbonate and that rings on bathtubs are calcium soap,
this method would work but, depending on how much fatty acid
you have in your oil, it might require an inordinate amount of water.

I don't know, this is only a thought, but maybe reacting the oil
at lower temperature (say mixing at room temperature as opposed
top cooking it as when manufacturing soap) would result in relatively
less the oil being turned in to soap.

Welder - 26-1-2008 at 20:04

Thanks Microcosmicus.

14 mg/L sounds like a pretty low concentration. I'm not sure that much FFA could be soaped without using far too much water. Maybe lye would be better, I'm just concerned that the lye soap may not want to settle out to easilly. I've heard that thoroughly drying the partly soaped WVO will really help the dry soap to settle out making seperation (decating, filtering, CFing etc) much easier.

Ultimately, the goal is to remove FFAs from the WVO based on the concern that FFAs may cause corrosion.

If very dry (under 500 PPM water) WVO has FFAs that need water to corrode the steel surfaces of diesel injection systems, then maybe WVO that has FFAs still in it would be okay.

I'm only, a welder, not a chemist and I've heard conflicting opinions on the subject of whether dry FFAs are corrosive, so I'd love to hear more input on this.

Thanks again for all your guys advice!

microcosmicus - 26-1-2008 at 21:34

Quote:

I've heard conflicting opinions on the subject of whether dry FFAs are corrosive,


Sounds like time for an experiment to me. Put some freshly polished metal
in a sample of your oil, heat it to the sorts of temperatures you expect to
encounter in use, wait some time and see exactly how much corrosion occurs.
Then maybe repeat the experiment with oil that has been processed with
alkali, dried, etc. to see how much of an improvement comes from these
various treatments. Likewise experiment with different alkalis (lye, quicklime)
to see exactly how much work is needed to remove the fatty acids using
different processes.

Ultimately, I expect that it all will come down to a tradeoff between the cost of
preprocessing the fuel and of replacing corroded parts. Having the experimental
data on how different processing of the oil affects amount of corrosion will help
one make a informed decision as to where to strike the balance. Also, if the
corrosion is a problem, maybe look into the possibility of replacing some critical
parts of the engine (say fuel injectors) with parts made from a more inert metal
or doing some sort of a surface treatment on the metal (e.g. bluing steel or plating
it) to make it less prone to corrosion.

Finally, do you know how much free fatty acid is contained in a given amount
of your oil? If not, that would also be worth measuring.

Welder - 27-1-2008 at 03:57

Yes, I agree that experimentation is likely needed. I had just hoped that maybe data already existed. Maybe I should at least do an advanced Google search using "free fatty acids" as a search phrase and "corrosion" as a search word. Maybe throwing the search word "anhydrous in there would help too as water content is likely a factor in any FFA corrosion that may occur.

One of the reasons I wanted to avoid having to do a physical experiment is that I'm not sure exactly how long it might take for FFAs to effect corrosion on bare steel. Polymerization of vegetable oil may take a relatively long time, but under certain conditions may also be quite rapid, relatively speaking. If any corrosion caused by FFAs takes as long as some slower forming polymerization sometimes takes, I may not even notice any corrosion forming for a fairly long time. I'd hate to pull the plug on an expirement after getting a false negative after not waiting long enough to see corrosion forming. It may be a long term experiment.

There's an antioxidant called TBHQ that's ben tossed around a little as a possible preventative for polymerization formation. If TBHQ efffectively prevents polymerization by preventing oxidation, then perhaps it may also effectively prevent FFA related corrosion. Another control group to add to the expirement, I guess.

The FFA content in WVO can vary widely. I think I may have heard of very hard used oil with up to 15% FFA content, but I'm not sure if I'm remembering that correctly. I know the biodiesel folks consider FFAs to be important sometimes.

Ozone - 27-1-2008 at 08:01

Most of what I see, re. FFA involves an initial titration of the material (WVO) so that the amount of catalyst will exceed the amount of FFA. THis insures that there is actually free catalyst present (rather than the stable salt).

The salt should be quite water soluble, and should end up (mostly) in your glycerol layer, along with any excess alcohol. Acid catalysis avoids this as the FFA will form esters as well (but, removal of the catalyst becomes the issue with corrosivity).

It seems to me that the corrosivity of the FFA in WVO shouldn't be a huge problem unless that FFA is dissociated; this requires a polar solvent, like water. I would also be concerned about polymerized glop (which can eventually result from polymerization of autooxidation products such as malondialdehyde) which can foul sprayers, lines, etc. This can be assayed using thiobarbiuturic acid; the measure is given as ppm TBARS (Thiobarbiturate reactive substances).

Unfortunately, in many climates, it can be unusual for your BD to be *bone-dry*.

I think that the oil-soluble inhibitor seems like a good idea--just keep in mind that the inhibitor reacts when it does its job (it is s temporary fix, and this should be considered for long-terms storage). Over time, TBHQ will dimerize (giving that red color to old solutions). While this may not effect the function of the fuel, it may blow the color specifications.

For a sensitive assay of the slow reaction, the Fe-o-phenanthroline method is very sensitive. I imagine that your sample of metal in the oil could be shaken and sampled. THe sample would be extracted with a bit of water, reduced with hydroxylamine (or, IIRC bisulfite; the complex forms with Fe2+) and treated with o-phenanthroline in an acetate buffer at pH 5. Absorbance measured at 510nm can give a good measure of Fe taken up into the mixture. The effective calibration range is up to about 5 or 6 ug/mL before the absorbance exceeds 2. This might yield quicker results than waiting long enough (which might be very long, indeed) to detect a loss in mass of the test coupon (gravimetry).

Cheers,

O3

O3

Welder - 31-1-2008 at 03:14

My only interest in WVO is in burning it straight, as diesel fuel in a modified fuel system with line heaters etc. This fuel method is called SVO, for Straight Vegetable Oil (animal fats work fine too).

The question I have about FFAs is a concern over whether they will cause corrosion in a fuel system even after thorough dewatering (under 500 PPM water in oil).

I mean, I know they are called acids for a reason, but triglycerides are really only a glycerol molecule with three chains of fatty acids attached, right? So if the fatty acids don't cause corrosion when bound to the glycerol, are they likely to cause corrosion when free? I know that water based acids are formed when cooking oil is used, but knowledgeable SVO users water wash the water based acids out of their WVO before drying it and filtering it.

It looks like I may have to do a little more research and maybe even do a little experiment.

I know this thread was originally intended to explore glycerol usage, but since my questions were biofuel chemistry related, I thought maybe asking them here might get responses from chemists more specialized in oleochemistry etc. Sorry to hijack.

[Edited on 31-1-2008 by Welder]

not_important - 31-1-2008 at 06:38

As fats or oils they aren't acids, but rather esters with no really acidic hydrogen. They really haven't any reactive groups to interact with metals, and they are less hygroscopic than the free acids.

Even a very small amount of corrosion of metal while in storage, including fuel tanks, results in metallic ions that tend to increase the rate of reaction of unsaturated bonds with oxygen; this leads to cross-linking and the formation of gums and 'varnish'. You've addressed this a bit with the mention of TBHQ.

On the other hand, the saturated FFA have been used as lubrication enhancers in fuels, so they may not be that bad. However fuel blends like that likely included corrosion inhibitors and so on.

One other aspect is that carboxylic acids tend to form weakly bound dimers through hydrogen bonding, these could increase viscosity.

a couple of reports that may be of interest

http://www.abqaltenergies.com/documents/Vegetable%20Oil%20as...

http://www.greencarcongress.com/2007/04/german_research.html

Ozone - 31-1-2008 at 15:42

Well...

I suppose burning the oil intact is, in fact, a way to mitigate the glycerol glut! You will have to start the engine on diesel range organic (preferable biodiesel) before kicking the WVO in (and also before shutting down). Even this application pushes (in however small a way) the use of biodiesel.

Might I suggest biodiesel WVO blends?

I would also consider blends with ethanol to lower gelling point and to help manage flow viscosity.

Cheers,

O3

Welder - 1-2-2008 at 02:47

NOT_IMPORTANT:

Thanks for the technical info.

When you mentioned the "free acids", did you mean FFAs or water based acids?

Is there a way to affordably saturate the FFAs to reduce their reactivity?

Is saponification/neutralization the only way?

Can FFAs be hydrogenated? (increased viscosity is no problem with heated fuel systems) If FFAs can be hydrogenated along with the other components of WVO, then an industrial hydrogenator would seem to be a possible way to prevent fuel degradation.

I once saw an article announcing the development commercial/industrial enzymatic hydrogenation units meant to be made availabe through long-term leases. If I can find that again, I'll try to post a link.





OZONE:

Yes, I'm aware of blends, but I prefer the idea of running SVO over both blends and biodiesel. Safer and cheaper.

Tacho - 1-2-2008 at 03:14

I agree with ozone. Blends may be the optimal solution.

IIRC, the main problems with SVO as fuel are high viscosity, tarry (carbon) deposits on the injectors, aging (polymerizaton, oxidation, etc) and pollution (acrolein). I can't give you references, but I remember reading somewhere that most of these problems are solved by blending with regular diesel. It makes sense, diesel would reduce viscosity and maybe "wash" the injectors. Aging may be a problem for the industry, but not for a DIY operation. We are left with acrolein.

Im sure you read the biofuels thread here.

don't miss the by Adam Kahn (pdf) work.

not_important - 1-2-2008 at 06:52

Quote:
Originally posted by Welder

When you mentioned the "free acids", did you mean FFAs or water based acids?

FFA
Quote:

Is there a way to affordably saturate the FFAs to reduce their reactivity?

Is saponification/neutralization the only way?

Extraction from the oils, as by forming salts (neutralisation) and washing them out, or by converting to esters.
Quote:

Can FFAs be hydrogenated? (increased viscosity is no problem with heated fuel systems) If FFAs can be hydrogenated along with the other components of WVO, then an industrial hydrogenator would seem to be a possible way to prevent fuel degradation.

This will not affect the acidity, just the viscosity and polymerisation issue. Well, unless you reduce the carboxylic -CO2H to alcohol -CH2OH, which with most hydrogenation processes will have reduced the oils (glycerol esters) to alcohols first. Not cheap, not DIY unless you're into high pressure plumbing.

From what I've read on using SVO, keeping the heating to a minimum reduces the corrosion any poly problems. This includes not heating the fuel tank or heating as little as possible, the higher viscosity of more saturated fats would be a problem given that minimised heating goal. This would seem to be even more of a problem in climates where you can use lard bricks as hammers in the winter; having to wave a blowtorch over your fuel system to get it functional may have been OK with the Antarctic station folk, but doesn't excite me.
Quote:
I once saw an article announcing the development commercial/industrial enzymatic hydrogenation units meant to be made availabe through long-term leases. If I can find that again, I'll try to post a link.


I'd be interested in that. While alkene double bonds are hydrogenated biologically, and the double bonds in oils are removed enough from the acid function to be considered simple alkenes, I've not heard of any industrial process to do so.

There was a push to use lipases to interesterify fats/oils to change their melting points. In a recent process stearin, the tri-stearic acid glycerol ester, from palm oil or full hydrogenation via the normal catalytic method, is enzymatically interesterified with ordinary vegetable oils to produce fats with melting points in the desired range for butter-like products. It replaces the older partially hydrogenated fats, the fatty acids in the new product are either fully saturated or the natural unstaturated ones which are mostly cis-.

Quote:

Yes, I'm aware of blends, but I prefer the idea of running SVO over both blends and biodiesel. Safer and cheaper.

Cheaper maybe, if the potential corrosion and polymerisation problems do not arise or can be overcome inexpensively enough, and if the time spent in doing so is little enough or discounted enough. But the possible problems with emissions of nasties doesn't automatically make the process safer. And using ethanol in place of methanol removes that toxicity issue.

Welder - 2-2-2008 at 05:28

The issues of corrosion and polymerisation were why I started asking questions here in the beginning.

Heat is essential to svo and while it can certainly be a factor in oxidation, and polymerization, it is still the heart of svo technology. It's something used on transoceanic vessels so they can burn bunker fuel instead of diesel.

Saturated (high visc) svo fuel melts fine with waste engine heat and after mel;ting, it burns just fine too. Many svo people are running around on lard or hydrogenated veggie, they just heat their tanks to liquify their fuel (no blow torch required). The heat doesn't seem to cause any polymerization problems because the oil is already saturated.

Maybe FFAs can be dealt with easier with using additives than processing into soaps.

froot - 26-5-2008 at 06:10

Another link regarding the conversion of glycerol to ethanol using E. coli:

http://biopact.com/2007/11/scientists-convert-biodiesel-bypr...

Skrinkle - 23-6-2008 at 13:33

Quote:
Originally posted by Tacho
Glycerol retains moisture. Wouldn't it be useful for agriculture if mixed to soil? Not for the water itself, but as a soil "softener".


What about the soil dwelling fauna? Wouldn't it suffocate the earthworms that aerate and fertilize the soil? I'm just guessing.
I agree about the lubricant thing, but maybe it could also be used to lubricate engines?

[Edited on 23-6-2008 by Skrinkle]

UnintentionalChaos - 23-6-2008 at 18:00

Glycerol, in a non-oxidizing, hot environment such as use as engine grease would lead to dehydration forming awful smelling, toxic acrolein which would polymerize and gunk up the engine. Not only that but its hygroscopic and would promote corossion.

It probably would not be good for soil dwelling organisms....I've been wondering if you can chlorinate only one of the alchohol groups and use it to modify cellulose producing a thickening agent similar to hydroxyethyl cellulose.

Ritter - 26-7-2008 at 13:01

Glycerol from biodiesel must compete with synthetic glycerol.
And derivatives such as acrolein, allyl alcohol, etc., must compete with petrochemicals.

The most interesting use of waste glycerol that I've run into is reacting it with oxygen & superheated steam to create synthesis gas (CO + H2) for manufacture of methanol, F-T liquid fuels & basic petrochemicals such as butyraldehydes from propylene (the 'oxo' process). In this way it replaces fossil fuels so that they can be used for more critical applications.

[Edited on 26-7-2008 by Ritter]

not_important - 27-7-2008 at 05:06

Quote:
Originally posted by Ritter
...
The most interesting use of waste glycerol that I've run into is reacting it with oxygen & superheated steam to create synthesis gas (CO + H2) ...


That syngas is going to have a lot of CO2 in it, until scrubbed out, unlike syngas from coal or hydrocarbons.

(COH2)3H2 ==> 3 CO + 4 H2 if you could make it happen

(COH2)3H2 + xO2 => 2x CO2 + 3-2x CO + 4H2 or combinations with some water

(COH2)3H2 + xH2O => x CO2 + 3-x CO + 4+x H2
&ct

Those lower yields of CO, combined with the relatively low energy content of glycerol, will make for fairly expensive syngas.

Ritter - 27-7-2008 at 06:03

Quote:
Originally posted by not_important
Quote:
Originally posted by Ritter
...
The most interesting use of waste glycerol that I've run into is reacting it with oxygen & superheated steam to create synthesis gas (CO + H2) ...


That syngas is going to have a lot of CO2 in it, until scrubbed out, unlike syngas from coal or hydrocarbons.

(COH2)3H2 ==> 3 CO + 4 H2 if you could make it happen

(COH2)3H2 + xO2 => 2x CO2 + 3-2x CO + 4H2 or combinations with some water

(COH2)3H2 + xH2O => x CO2 + 3-x CO + 4+x H2
&ct

Those lower yields of CO, combined with the relatively low energy content of glycerol, will make for fairly expensive syngas.


As I pointed out in another thread, there are developing technologies for reducing CO2 to either methanol or F-T liquid fuels.

gsd - 22-8-2008 at 00:10

Future of Glycerol: New Usages for a Versatile Raw Material (RSC Green Chemistry Series)
by Mario Pagliaro, Michele Rossi

http://ecx.images-amazon.com/images/I/41rgHZ46MDL.jpg

This book aims to inform chemistry professionals, including managers and technologists, on the large potential of glycerol as versatile biofeedstock for the production of a variety of chemicals, polymers and fuels. Whilst filling a gap in the current literature, this nicely illustrated book is written in a clear, concise style and presents the numerous uses of glycerol as a new raw material which are starting to have an impact on industry worldwide. Elucidation of the principles governing the new chemistry of glycerol goes along with updated industrial information that is generally difficult to retrieve.

Through its 10 chapters, the monograph tells the story of a chemical success that of converting glycerol into value added products and highlights the principles that made it possible. Whether as solvent, antifreeze, detergent, monomer for textiles or drug, new catalytic conversions of glycerol have been discovered that are finding application for the synthesis of products whose use range from everyday's life to the fine chemical industry.

Readers are also shown how a number of practical limitations posed by glycerol chemistry, such as the low selectivity encountered employing traditional stoichiometric and older catalytic conversions, were actually solved based on the understanding of the fundamental chemistry of glycerol and by application of catalysis science and technology.

Readers also find a thorough discussion on the sustainability issues of bioglycerol production covering societal, environmental and economic dimensions to reflect the needs of politicians and citizens of today who require cross border research. By explaining the advantages and problems as well as offering solutions the book aids understanding as to whether biodiesel and glycerol refineries are convenient and economically sound.

Link posted in the : The New Book Thread (Organic Chemistry)

gsd