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Making biodiesel with isopropyl alcohol

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November 12, 2012, 11:58 AM
Making biodiesel with isopropyl alcohol
I know that the reason that isopropyl alcohol isn't used as an ester in processing is the risk of soap content. Excess water is to be found in sufficient qualities in the store-bought isopropyl alcohol, but what if you use 99% isopropyl alcohol? Will this also lead to a higher risk of soap forming? 99% should have very little water in it, shouldn't it?
November 12, 2012, 02:17 PM
Isopropyl or 2-propanol is a secondary alcohol. Partly due to steric hinderance it reacts slower. Primary alcohols react faster in the transesterification reaction. It should react some, how much I don't know. Examples of primary alcohols are methanol, ethanol, 1-propanol, 1-butanol etc
November 13, 2012, 01:49 PM
Soap is produced from the free fatty acids in the vegetable oil and sodium or potassium hydroxide, even if the alcohol is dry. Water in the alcohol causes saponification, another soap producing reaction. There are several reactions going on at the same time, neutralization of free fatty acids, saponification, transesterification, and others. Drier alcohol to start helps the transesterification reaction to proceed more relative to saponification. Water in the alcohol also lessens the amount of 2-propoxide to be present in the reaction mixture. We want a drier reaction to produce biodiesel. The drier the better. Thanks
November 14, 2012, 03:32 PM
99% isopropyl alcohol should have less than 1% water in it. That's not much. Thanks
November 17, 2012, 08:31 PM
I used dry 1-propanol to make biodiesel using KOH as catalyst with new corn oil. These was no glycerine phase separation probably due to what I think is called a co-solvent effect. So I used hot distilled water with sodium chloride in it to wash out excess alcohol, glycerine and soap from the crude biodiesel reaction product. That worked. I dried the 1-propyl biodiesel with anhydrous sodium sulfate. On a lab scale it worked but on a larger scale a different procedure might be employed. I expect using dry isopropyl alcohol (2-propanol) might not get a phase separation (glycerine drop out) also, after the initial transesterification reaction. The biodiesel is in there under the right conditions, but purifying it is a bit of a problem, on a large scale. Thanks
December 07, 2012, 05:50 PM
where you able to determine the cloud point of the corn/IPA batch?
December 08, 2012, 05:48 AM
I don't have any corn oil based isopropyl ester biodiesel now. I've got some 1-propyl fatty acid ester biodiesel made from corn oil, but that's not the same thing. When I tried to make the isopropyl ester (2-propyl ester) I didn't use enough catalyst, years ago. I would have to buy more anhydrous 2-propanol (isopropyl alcohol) to try it again. I did not determine a cloud point. My ethyl stearate is a solid at room temperature, but my 1-propyl stearate is a liquid. Room temperature is about 73 degrees F in here plus or minus 2 degrees depending on which thermometer I believe. Stearic acid is a component of corn oil 1-4%, its a solid at room temperature. Stearic acid is one of the higher melting natural fatty acids.
December 08, 2012, 09:12 PM
Wesley, you ever mess with any other alcohols compounds like N-butanol or 2-methal 1-butanol?


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December 09, 2012, 08:25 AM
I've only made biodiesel with methyl, ethyl, 1-propyl alcohols. I tried to make it years ago with 2-propyl alcohol (isopropyl alcohol) but I didn't get it to work.
January 26, 2013, 04:25 AM
I made the Isopropyl Biodiesel (2-propyl biodiesel) from 400 millilitres new corn oil, 3.2 grams 85% KOH and 148 millilitres 99.8% Isopropyl Alcohol (2-propanol). Heated for about 7 hours with magnetic stirring at 72 to 78 degrees centigrade in a sealed round bottom boiling flask. Two phases (layers) formed. Removed the bottom layer. Washed the top layer twice with hot salt water, then twice with hot distilled water. Dried with anhydrous sodium sulfate. Then dry washed with magnesium silicate to get 105.64 grams of isopropyl biodiesel with a density of 0.940 grams per millilitre. I did a 3/27 test with methanol and it was a miserable failure. I'm not sure if I converted much vegetable oil to biodiesel or not. I did a 3/27 test with 99.8% isopropanol and it passed nicely. I don't know if a 3/27 test done with anhydrous isopropyl alcohol is a valid test.I checked the density of my liquid product again because it was too heavy. On my second test I got a density of 0.9145 grams per milliliter which matches the density I measured for new corn oil. It seems to me that I did not get any isopropyl biodiesel using this proceedure. I thought I made it, but I didn't. Two layers formed after the base catalysed transesterification reaction.

This message has been edited. Last edited by: WesleyB,
February 02, 2013, 07:00 PM
Stearic acid is one of the types of fatty acids in many types of vegetable oils. Another name for strearic acid is octadecanoic acid. I mixed 196.5 grams stearic acid with 150 milliliters isopropyl alcohol 99.8% anhydrous, and 5.2 milliliters concentrated sulfuric acid. Put in a 1 litre round bottom boiling flask with a ground glass stopper. Put a magnetic stirbar into the flask. heated with magnetic stirring for about 9 1/2 hours at 69-80 degrees centigrade. Two liquid layers (phases) formed. Poured off the upper layer into a 1 litre separatory funnel.Washed three times with 200 ml portions of distilled water at room temperature, then four times with very hot distilled water. Put the remaining organic layer into a 500 ml round bottom boiling flask with 40 grams anhydrous sodium sulfate. Heated the 500 ml stoppered flask about 6 hours without stirring at 44-70 degrees centigrade. Left the flask to cool to room temperature for about 9 hours. The liquid in the flask was colorless and transparent, then upon cooling and being left undisturbed a white solid appeared. I was able to pour off about 38 grams of what is probably isopropyl stearate with a little isopropyl ether in it. Not much product for all the trouble. Anhydrous isopropyl alcohol reacts with free fatty acids but not very completely. I got better results with primary alcohols when compared to secondary alcohols. Methanol works a lot better than isopropyl alcohol for making biodiesel. Isopropyl alcohol seems to me to work, but not very well. I put the isopropyl stearate in a freezer that was 0 degrees farenheit, it froze, which shows is not isopropyl ether. I measured the density of the liquid product at 0.85 grams per millilitre. Book value for Isopropyl stearate is about 0.84 grams per millilitre. There is a little white powder in the liquid product, that might account as to why the density is a little high. I suppose some sodium sulfate drying agent might have got through or the white powder is from the inside of the new 8 ounce storage bottle I put it in, the new storage bottle was not perfectly clean.

This message has been edited. Last edited by: WesleyB,
August 18, 2013, 03:10 AM
I tried to make biodiesel from anhydrous isopropyl alcohol, corn oil and potassium hydroxide, using the normal methods. My product was mostly unreacted corn oil, based on the density of the product. The transesterification reaction didn't proceed much, probably because of steric hinderance factors. But I was able to make the isopropyl fatty acid ester (biodiesel) from stearic acid, anhydrous isopropyl alcohol and concentrated sulfuric acid via the Fischer esterification method. So isopropyl biodiesel can be made by acid esterification of free fatty acids, with anhydrous isopropyl alcohol and concentrated sulfuric acid catalyst. I have read that isopropyl biodiesel has better cold flow properties.
September 21, 2013, 01:44 PM
Hello everybody

From comments above I can see that production of biodiesel from isopropyl via traditional (Oil+Alc+KOH) method in a large scale is not possible. Or is it? Smile I come from Ukraine, methanol here is forbidden to sell as extremely hazardous alcohol, while ethanol is quite expensive. Isopropyl one is good in price and access but is there a technology to make a diesel from oil and it? Or maybe some other alcohol, similar to isopropyl in price? I promise a 100$ for a working technology, cheap and possible to implement without super-hard efforts Smile

Good luck to everybody!
January 20, 2014, 09:23 PM
TAR_777; I apologise that I didn't notice your $100 reward for biodiesel produced with isopropyl alcohol before. This can be done but the price is higher than producing biodiesel from vegetable oil. Free fatty acids can be made from vegetable oil. This is old technology.
One of the fatty acids produced from vegetable oil is stearic acid.
I put 196.5 grams stearic acid (octadecanoic acid) and 150 millilitres anhydrous isopropyl alcohol and 5.2 millilitres concentrated sulfuric acid into a 1 litre round bottom boiling flask. Stoppered the flask. Heated the flask in a hot oil bath for about 10 hours at 70-76 degrees centigrade with magnetic stirring. Poured the reaction product into a separatory funnel Extracted with distilled water, and hot distilled water. Took the top layer of isopropyl stearate, put 40 grams of anhydrous sodium sulfate in it to dry it at about 70 degrees centigrade.After separating the isopropyl stearate from the drying agent I only got about 38 grams of the fatty acid ester. It had a measured density of 0.85 grams per milliliter, while book value is 0.84 grams per millilitre.
This is an example of the Fischer esterification, where carboxylic acid reacts with alcohol using sulfuric acid as a catalyst.
This could be used to make biodiesel using isopropyl alcohol, but making free fatty acids from vegetable oil would be energy expensive and probably not cost effective.
January 20, 2014, 10:14 PM
TAR_777;I looked at my lab notebook. You said you can't get methanol and dry ethanol is expensive, so can you use isopropanol to make biodiesel? Well, isopropanol is also named 2-propanol. But if you can get 1-propanol at a good price, it can be used to make biodiesel from vegetable oil+alcohol+ sodium hydroxide. You just use an equimolar amount of 1-propanol compared to the amount of methanol that you would have used for the transesterification reaction. I read there's a $100 reward for this information. Don't disappoint me. Oh yes, I made the biodiesel from 1-propanol+corn oil+ potassium hydroxide, it works. But the starting materials must be almost water free(anhydrous).

This message has been edited. Last edited by: WesleyB,
January 30, 2014, 08:36 PM
TAR_777; Based on reading and a few experiments, for the transesterification reaction of vegetable oil + caustic dissolved in alcohol----> biodiesel + glycerine, the alcohol should be a primary alcohol, not a secondary alcohol such as isopropanol. A tertiary alcohol will not work either according to a chemistry book I've got. But an ester can be made from a free fatty acid plus isopropanol with sulfuric acid catalyst + heat and stirring. I don't know how much chemistry education you've got, I'm trying to explain clearly.