Tilly; I did the calculations in the past to determine the stoichiometric amount of biodiesel produced and the volume of methanol required to make biodiesel from new corn oil. But when I titrated new corn oil the sodium hydroxide titration number was 0.6 grams/litre. That's a little fly in the ointment. A 100% stoichiometric amount of biodiesel produced from 1 litre of new corn oil with no free fatty acids in it is 1056.5 milliliters. That requires 127.2 milliliters of 100% of anhydrous alcohol. That's figuring corn oil with a density of 0.915 grams per litre (I measured it) and biodiesel with a density of 0.87 grams per millilitre. The average molecular weight of the methyl fatty acid ester from corn oil is about 292 grams per mole.
There are a few flies in this ointment.
It is true that we do not know what type of oil was being reacted, but it is common practice to consider 12.5% methanol (125ml methanol/ litre WVO) to be the stoicheometric amount of methanol required for the reaction.
Dgs claims to have used 12% methanol (120 ml methanol/ litre WVO) to perform the reaction which is pretty close to stoicheometric.
HOWEVER The first fly in the ointment is that this is NOT A stoicheometric reaction, it is an Equilibrium reaction
As I am sure you know, that means that it requires More than the stoicheometric amount of methanol to achieve a complete reaction.
The second fly in the ointment is that my conversion chart shows that in a single stage reaction, if you perform the reaction using the stoicheometric amount of methanol you would achieve about an 81% conversion.
Do you see the flies?
It's amazing what you find when you Google your name. I haven't visited this forum for some time, and there have been several pages of discussion since I last visited.
I'll plough through them when I get a chance, and answer as many questions as are appropriate. In saying that I face the problem that most of you don't understand much chemistry (exception is WesleyB). This is complicated by the fact that a couple of self-styled experts have popped up who think that they do, and have done nothing but confuse people with their uninformed comments.
The bottom line is this - the explanations I have given will make perfect sense to a chemist. If they don't, then I'm afraid I don't have the time or inclination to conduct online chemistry tutorials. The method was written for the layman. All you have to do is follow the method and it will work. I'll happily answer any questions directly arising from the method, like this one.
Also, I have now simplified the method even further, but I'll get to that later.
To answer this specific question, if you got soap in the batch, it's because the oil wasn't dry. This method is anhydrous, and will work best with dry oil.
I once got lazy with this, but never again. I had a batch that I knew had some water in the oil, but went ahead anyway. The result was that the method didn't proceed at room temperature - a bit of a problem when you make 1000L at a time.
So I whacked a water heater in it overnight, and by the time the temperature got to about 30C it commenced.
Afterwards when it settled there was a yellow layer of soap sitting on top of the glycerol, which I guess is what dgs is referring to. The problem that this caused was it greatly increased the settling time when I tapped off the raw product into one of my settling tanks. Never again.
Shortly I'll repost my method modification. Also, for those of you living in Perth WA I'll be doing a public demonstration of this method soon.
Hello Minder/ Dr Mark/ Mark Imisidies,
You are acquiring more and more online names all the time
I understand your problem and that you are way to busy to try to explain what you are talking about.
We will just struggle on the best we can.
I am afraid that some of us on this forum have been well and truley spoiled.
At one time we had an Industrial Research Chemist (PhD) on the forum who went by the name of Neutral who was really really knowledgeable about the chemistry involved in making biodiesel and was outstanding at explaining complicated things so that us chemically ignorant people actually understood what he was talking about.
He should have been a teacher!
As I recall, he had been involved in alternate fuel research in the 70's and had actually made biodiesel way back then.
Of course it was not called biodiesel in the 70's.
That is a worry.
When I use just the standard method of making biodiesel it processes at room temperature. It just takes longer.
In fact, Dgs has reported that he normally processes everything at Ambient temperature and the reaction is finished in 45 Minutes!!!
I am eager to see your modified method!
Isn't it a coincidence, the chemist Neutral also lives in Perth!!!
OH!!! It just twigged,
you need to go on to the Australia biofuel forum and tell everyone there you are doing a demonstration in Perth.
From freshman university chemistry, professor Bramer said, for some organic chemistry reactions a ten degree celcius increase in temperature doubles the reaction rate. But at a inadequate temperate the reaction will not proceed. I am sceptical of this room temperature reaction proceeding to form our desired product.
I promise when you post your revised anhydrous processing method I will certainly try it over here in the UK. I tried the first method you posted, but like dgs, found that it produced calcium soap which could only be removed using wood chips. Made lovely bio though, which is in my car now! No explanation of the chemistry involved is fine for me. I'm only grateful that you are prepared to share your findings here.
One thing I would like to ask - you say that you process your own oil in 1000 litre batches. Which method do you use to dry that quantity of oil?
I don't dry the oil. I use dry oil to begin with. I don't have a Karl Fischer unit handy to measure it, but my test is simply whether the oil is transparent - ie free of any murkiness. I have found in the past that drying oil that contains water is simply not practical in the volumes I am using. The reason is that normally if there is water in the drum I am collecting oil from, it is because they have put washings into the drum, and this involves surfactants of some sort. Hence it will sit there as an emulsion and never actually settle out.
If the oil is dry the reaction will begin in a couple of minutes, and no soap will be formed.
BTW the modification I have made is to substitute General Purpose Grey Cement as the drying agent, as quicklime is unavailable over the counter here in WA. Note, it is the grey cement powder only, not the Concrete that also contains gravel and sand. It's a mixture of dry silicates, along with some quicklime and other salts that does a nice job of dehydrating the meth solution.
I'm going to get a website set up at some stage complete with vids that'll simplify any questions rthat people may have
That is interesting,
I looked up the MSDS for Boral General Purpose Cement and it lists the content of Calcium Oxide/ Quick lime as "<3%"
Considering there is such a minimal amount of quick lime available in General Purpose grey cement, how much do you recommend people use?
I'm not so sure about that Tilly. I've had a look to find out and it seems that Ordinary Portland Cement (what we mostly use here in the UK) consists of 63% CaO
Now I may have got a bit mixed up, and maybe that is the CaO level before the cement is finished. It might start at this level but be much lower in the finished product.
The exact components of the cement don't matter. The only requirements of the drying agent are
1. That it be insoluble in MeOH
2. That the aqueous adsorption equilibrium lie to the right. This is the beauty of the CaO, as it forms hydrated lime, and pulls it further to the right than you'd normally get with a purely adsorptive mechanism.
The fact that the cement is so fine also helps, as it provides a large surface area for adsorption.
One factor that I didn't mention in the initial method is that the methoxide solution needs to be sealed from the atmosphere as far as is possible while it's settling. As a highly alkaline, dry methanolic solution it will rapidly absorb both water and CO2 from the atmosphere very quickly, both of which will degrade it. In my case I put a tarp over the drum with some ocky straps
Correct. And for some it will triple it. And for some it will quadruple it. And for some it will make no (measurable) difference. The nature of catalysis is that it lowers the Ea by providing an alternative mechanistic pathway to the products. That mechanism may be heterogenous, such as the catalytic converter in your car where the function of the catalyst is simply to immobilise the reactants in the solid phase, or homogenous, as in this case.
In the case of a homogenous catalyst the relationship between temp and reaction rate is far more nebulous, as it is dependent on a whole lot of factors that are often not known, most notably (and obviously) the order of the reaction. Evidently you don't understand as much chemistry as I thought you did.
I'm pleased you are back posting after all this time to help us with your method.
When I added the calcium oxide to my mixed potassium methoxide, I probably added too much in an attempt to make sure it was as dry as possible. Someone on the UK forum suggested that this could have formed some calcium methoxide and this was the reason that the calcium soaps were present in the resultant bio.
'sooty', who has posted on this thread has been doing this method for some time and in one of his last posts says that passing his biodiesel 3 times through woodchips is normal to remove the calcium soaps.
Don't get me wrong here, I think the method is really good, but any comments you have about keeping those calcium soaps to a minimum would be appreciated.
Many thanks, Dave.
After more research, it appears that the list of chemicals you linked to are the chemicals that go into the cement kiln which is then heated to a fusion temperature, which is about 1,450 °C (2,640 °F) for modern cements, to sinter the materials into clinker
Typical constituents of Portland clinker plus gypsum
Dicalcium silicate................7- 32%
Tetracalcium aluminoferrite...0- 18%
So it appears that once the CaO goes into the Kiln it is fused with other chemicals to produce Portland Cement Clinker which is something all together different.
The Cement Australia SDS for Portland cement gives-
Portland Cement Clinker....<97%
Hexavalent Chromium.......<20 ppm
Crystalline Silica (Quartz)..<1%
So it appears that cement is not a good source of Calcium Oxide/ CaO
Dgs et. al.
Let me clarify I have not been using this method and never dried my NaOH methoxy using CaO. The three chip passages I needed was using pretreat/no titration and whole batch demeth to get rid of "regular" soaps.
What I did test was a method first used in Mexico where CaOH was used as the catalyst instead of NaOH or KOH, with the goal of both converting oil and acting as a drying agent. The CaOH I used was a high CaO containing Garden Lime and it does produce biodiesel BUT
1.the fine CaOH catalyst remained visibly suspended in the finished biodiesel (prior to any filtering) and
2.the final cost of the CaOH when used as a catalyst was the same as NaOH
Didn't mean to mislead.
However, the brand of garden lime I used in those tests was “Hi-Yield” garden lime which has 72.5% CaO in it.
Might be a candidate for drying the methoxide and any fines might come out with the glycerin phase.
Now you have done it. You have well and truly blotted your copy book.
I think you have been relegated to the chemically challenged along with the rest of us.
Thanks for the clarification Sooty.
Whereas the CaO content of Ordinary Portland Cement may be low, it doesn't seem unreasonable that the manufactured product contains other dessicants that would dry the methoxide.
We have a product in the Uk called quick drying cement that I would imagine has a higher CaO content.
You certainly could be correct.
I am giving the MSDS of the product General Purpose Grey Cement which Minder recommends and Portland cement which is what you linked to in your earlier post.
There may be other products out there that contain more CaO, but I imagine that if they are called cement they will all be mostly Portland cement Clinker with relative tiny amounts of other contents.
Tilly - have you ever conducted any experiments involving attempts to dry the methoxide prior to processing and if so, did you have any success? What sort of yield do you achieve with your current process?
No I have not.
As I do not make biodiesel commercially, I have never bothered to go to the time and expense required to install the equipment necessary to accurately measure the finished amount of biodiesel I produce after washing and drying.
My eyeball measuring tells me that my yield is usually over 90% and less than 100%
|Powered by Social Strata||Page 1 2 3 4|