BIODIESEL & SVO DISCUSSION FORUMS





Sponsors    Biodiesel and SVO Forums Home    Forums  Hop To Forum Categories  Biodiesel  Hop To Forums  Other uses for Glycerine by-product    Triacetin From glycerol
Page 1 2 3 

Moderators: Shaun, The Trouts
Go
New
Find
Notify
Tools
Reply
  
Triacetin From glycerol
 Login/Join
 
member
posted Hide Post
The last time I requested a Texas state government issued permit to buy a flask, it was four to six weeks before I actually had the flask in hand and was driving home. Most adults at a gun show can buy a handgun the same day they make the application to buy one. It is easier to buy a gun than a boiling flask. That's the system in Texas, USA. Anyway, since glycerine + acetic acid + sulfuric acid catalyst produces triacetin + water + heat, if I can remove the water while it is being produced, then the equilibrium shifts to the right (products side of the formula). Sometimes that can be done by fractional distillation of the reaction liquid so the water is slowly distilled out as the reaction proceeds. Maybe you already know that. The glycerol layer from biodiesel production, after its demethed, still has potassium soap in it. I expect that potassium soap when contacted by a stronger acid will make the potassium salt of the stronger acid, that is potassium sulfate and potassium acetate which would stop my sufuric acid as acting as catalyst. Maybe someone has overcome this problem. The production of triacetate is exothermic. I wonder how much? Figuring out that on paper, I don't know how to do. I hope when I mix it together, it doesn't all come out at once. Explosive boiling. An acid splatter type thing. I noticed the Chinese have been working on it also, from scientific papers on the internet. People have figured out how to do it on an industrial scale, this is for the home brewer I suppose. Thanks
 
Location: Texas | Registered: April 27, 2011Reply With QuoteReport This Post
Member
posted Hide Post
If we tested the glycerol before processing with a soap titration test to find out how much soap was present then we might be able to increase the quantity of sulphuric acid to compensate for this, in the same but opposite way that we make biodiesel.
I think the only safe approach is to add the sulphuric acid VERY SLOWLY. That way we might be able to make the still self sustaining without external heat. An accurate adjustable dosing pump would be useful but where would you get one that would withstand concentrated sulphuric acid
Boiling flasks are easy to buy on Ebay here but no chance with a firearm. Maybe we could do a swop, ill send you a boiling flask and you send me a Glock. ( for the various security agencies watching our emails etc that was a joke)
 
Location: Lismore Ireland | Registered: November 25, 2007Reply With QuoteReport This Post
Member
posted Hide Post
Having looked into the pump problem it seems that a peristaltic dosing pump with polyethlene or pvc tubes would be no problem with sulphuric acid. It could be controlled by a PID temp controller so that as soon as the temp of the reactants went above 120C the acid supply would stop. Simple automation like that would reduce the labour considerably.
 
Location: Lismore Ireland | Registered: November 25, 2007Reply With QuoteReport This Post
member
posted Hide Post
I would mix the acetic acid with sulfuric acid then add it to the cold glycerine, slowly. I've never done this one before though. I try to err on the side of caution. An exothermic reaction getting out of control can be bad. I reacted an alcohol with an acid before. The proceedure was to cool one or the other to ice cold, in an ice bath, then slowly over an hour add the other. That was nitro ethane but only a small quantity, maybe 50-100 milliliters. I did that at a government university laboratory. It was completely legal. Thanks
 
Location: Texas | Registered: April 27, 2011Reply With QuoteReport This Post
Member
posted Hide Post
I had thought that if using 80% acetic acid, which is the easiest to get here, I would demeth the glycerol first and then add the acetic acid, then dewater both.
The sulphuric acid would then be added in a very slow controlled way such as a peristaltic dosing pump.
 
Location: Lismore Ireland | Registered: November 25, 2007Reply With QuoteReport This Post
Member
posted Hide Post
I have modified the original drawing to reflect the use of sulphuric acid in liquid form. The acid mixes with the other reactants just below the circulation pipe to achieve rapid dilution and mixing. The peristaltic pump would be controlled by a PID temperature controller with a probe as close to the reaction site as possible.



Uploaded with ImageShack.us
 
Location: Lismore Ireland | Registered: November 25, 2007Reply With QuoteReport This Post



Member
posted Hide Post
Just had another thought. If you look at this drawing I have modified the still. When demething the top valve would be open and the bottom closed. This would mean that it would operate as a full reflux still producing high purity methanol. When dewatering the valves would be reversed and it would operate as a high output pot still.We are not concerned about the purity of the water, we just want to remove it using as little energy as possible. The condenser pipe would be vented for safety.
[IMG=http://img841.imageshack.us/img841/4919/triacetin.png][/IMG]

Uploaded with ImageShack.us
 
Location: Lismore Ireland | Registered: November 25, 2007Reply With QuoteReport This Post
member
posted Hide Post
I don't see a thermometer, to monitor the reaction temperature. Sulfuric acid reacts with most metals. What is the surface of the immersion heater made of? I etched my name on 440C stainless steel once using concentrated sulfuric acid. Looks interesting. What is the approximate volume?
 
Location: Texas | Registered: April 27, 2011Reply With QuoteReport This Post
Member
posted Hide Post
I left out the temperature probes and the controllers because drawings tend to get messy once you include wiring. there would be a probe at the top of the reflux column wired to a PID temp controller which would control the immersion heater while in demething mode.
Once in dewatering mode another probe in the main tank wired to a second PID controller would control both the heater and the catalyst pump. If the temp went below say 108C the heater would come on and if it went above 118 the pump would stop.I dont know if the exothermic heat of the reaction would be enough to maintain the still but it would be worth trying and if not the heater would take over.
The tank and the heater would have to be stainless steel (incalloy) capacity 200 litres, processing around 100 litres. If the sulphuric acid was dripped into the downward stream of the circulation pipe it should never contact the metal in a concentrated state.
Ill redo the drawing in the morning with temp probes etc.
 
Location: Lismore Ireland | Registered: November 25, 2007Reply With QuoteReport This Post
member
posted Hide Post
An exothermic reaction can run away, or get out of control, where turning off the mixing pump doesn't kill the reaction. There's a lot of unknowns. Did you hear about the dynamite factory that had a run away, out of control reaction, when mixing nitric acid with glycerine? That factory was near Wichita Falls, Texas. I saw the field where the dynamite factory used to be. The third shift went up. Now there's just a field there. With nitroglycerine I think they dump ice into the mix to try to kill the reaction.
 
Location: Texas | Registered: April 27, 2011Reply With QuoteReport This Post
member
posted Hide Post
I'm still waiting for Dr. Turner to answer about how to remove the sulfuric acid catalyst from the triacetin product. Consider, if the reaction works starting with 80% acetic acid then at some point the liquid sulfuric acid ought to be removed prior to putting the triacetin into the fuel tank of the diesel motor. Thanks, Dr Turner doesn't always answer.
 
Location: Texas | Registered: April 27, 2011Reply With QuoteReport This Post
Member
posted Hide Post
quote:
2

I have a few contacts in universities and colleges here in Ireland who might be able to advise us if your Dr Turner doesnt come back to you.

I agree 100% that we need to be cautious with an exothermic reaction. But we have a situation where the one part of the reaction produces heat while another part( water removal) needs heat and if we can match these two we can have a self sustaining process. The contents of the reaction vessel will be about 100 litres and a peristaltic pump can be controlled to deliver as little as 5 ml at a time.
Here is the updated drawing.


As you can see there is now a temp probe at the top of the reflux column. This will control the heater while in demeth mode. A PID temp controller will maintain the temp probe at exactly 70 degrees C to ensure very high purity methanol. This will produce about 90% methanol and the remaining water can be removed economically with molecular sieve to produce a valuable product that has a ready market.

Once the demeth cycle is over the acetic acid is added to the processor and it is switched to dewater mode. The heater is now controlled by the probe in the reaction vessel and is maintained at 100C and the reflux column is closed off by opening the lower valve. This will ensure fast removal of water.

Once the dewater cycle is finished the reaction mode begins. The sulphuric acid is added in tiny 5 ml pulses and the temp probe/ controller will stop the pulses if the temperature rises above say 118C.
If the exothermic heat is sufficient it will maintain the reaction and continue dewatering untill the conversion is complete.
 
Location: Lismore Ireland | Registered: November 25, 2007Reply With QuoteReport This Post



member
posted Hide Post
Doesn't methanol boil at 65 degrees centigrade at atmospheric pressure? Then the still head thermometer ought to read 65 degrees during demething. Shouldn't it?
 
Location: Texas | Registered: April 27, 2011Reply With QuoteReport This Post
Member
posted Hide Post
You are right about the boiling temp of methanol 64.5C. But I find when distilling methanol if you set the reflux temp a little higher the output of methanol is greatly increased with only a small loss of purity.
 
Location: Lismore Ireland | Registered: November 25, 2007Reply With QuoteReport This Post
Member
posted Hide Post
The crude glycerol may contain up to 30% ffas and I think they should be separated before trying to make triacetin. There is a thread on this very subject here on the forum so I am trying to absorb that now.
 
Location: Lismore Ireland | Registered: November 25, 2007Reply With QuoteReport This Post
member
posted Hide Post
Free fatty acids are a carboxylic acid like acetic acid. With sulfuric acid catalyst + carboxylic acid + alcohol + heat should yield the ester plus water. That's a general formula. Glycerol is a tri-alcohol. So with long chain free fatty acids present + acetic acid + glycerol + sulfuric acid catalyst should yield a mixed product of esters plus water, not just triacetin.
 
Location: Texas | Registered: April 27, 2011Reply With QuoteReport This Post
Member
posted Hide Post
So do you think it would be better to leave the FFAs in and then separate the products after reaction? I would certainly save time and energy.
 
Location: Lismore Ireland | Registered: November 25, 2007Reply With QuoteReport This Post
member
posted Hide Post
By saying, a mixed product I mean that acetic acid might bond with two of the three carbons in the glycerine chain, and a long chain fatty acid might bond to the other carbon. I would be called something like glycerol-1-stearate-2,3-diacetate. I'm not sure how to purify the mixed product. It would be easier to figure out how to get a fairly pure end product by starting with purer glycerine. I think, here a person can buy glacial acetic acid by the drum (5 gallons, 40 gallons?). I wonder why it is difficult to get in Ireland. Thanks
 
Location: Texas | Registered: April 27, 2011Reply With QuoteReport This Post



Member
posted Hide Post
Im looking into separating FFAs from glycerol and it seems straightforward enough. I have done a couple of small samples with sulphuric acid and they worked ok so I think it should be possible to use the reactor to do this as a first stage. The ffas can be mixed with kerosene and burned in my heating system or added to veg oil and converted into biodiesel. The potassium sulphate can be used as a fertilizer. I use AE from time to time but I have no experience with pure FFAs.
 
Location: Lismore Ireland | Registered: November 25, 2007Reply With QuoteReport This Post
member
posted Hide Post
I made isopropyl stearate from fairly pure stearic acid and anhydrous 2-propyl alcohol by (sulfuric) acid esterification. It worked. I expect methanol could be used instead of 2-propanol in AE of fairly pure fatty acids. I don't have a lot of experience making biodiesel starting with free fatty acids, but I did it three times with stearic acid. Stearic acid is one of the fatty acids commonly in vegetable oil. I calculated that for about 1 litre of fatty acids from vegetable oil, that when acid esterification is done it produces about 58 grams per litre of water. I used an average fatty acid molecular weight (canola oil) of about 278 grams per mole to do the calculation, and a density of 0.895 grams per millilitre for the approximate density of the fatty acids. Making biodiesel using AE from 100%? fatty acids by acid esterification produces wet product, as water is produced in the reaction. Using a lot of anhydrous methanol makes it work better, but costs more. Then the problem comes up again of how to remove all the sulfuric acid catalyst from the product? The ethyl stearate that I made is a solid at room temperature. That was from anhydrous ethyl alcohol + stearic acic + sulfuric acid catalyst + heat yields ethyl stearate + water. The fatty acid (stearic acid) was fairly dry when I did the reaction. The alcohol was anhydrous. The dryer the better when doing acid esterification.
 
Location: Texas | Registered: April 27, 2011Reply With QuoteReport This Post
  Powered by Social Strata Page 1 2 3  
 

Sponsors    Biodiesel and SVO Forums Home    Forums  Hop To Forum Categories  Biodiesel  Hop To Forums  Other uses for Glycerine by-product    Triacetin From glycerol

© Maui Green Energy 2000 - 2014