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Author: Subject: Extraction of urea CO(NH2)2 from DEF (diesel exhaust fluid) – AdBlue
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[*] posted on 28-4-2021 at 04:53
Extraction of urea CO(NH2)2 from DEF (diesel exhaust fluid) – AdBlue


Hi!
This post is made as an addition to my youtube video Extraction of Urea CO(NH2)2 from AdBlue
link: https://www.youtube.com/watch?v=7Ubbt2Pp5zg

Here is my lab report of sorts:

Materials:
DEF (diesel exhaust fluid) – AdBlue

Procedure of extraction process:
300ml of AdBlue was measured out in a 400ml beaker using the approximate volume marks.
It was then brought to a boil, with a 12V/DC computer fan set to blow over the beaker. In 3hrs, the volume was reduced to roughly 75ml.
Some decomposition already had occurred, causing NH3 evolution. At that time, what I I had in the beaker was just molten almost anhydrous urea. There was no longer condensation on the sides of the beaker, and the solution reached a temperature a few degrees less than 140C. I didn't measure the temperature too precisely trouought the process, but it never got to 140C. I was lucky, because heating of urea without the pressence of water over 150C causes the formation of biuret, and that would mean signifficant loss of yield and impure product. The reaction still probably happened, but the product failed to form any color change when it should've been complexed to form the copper(II) biuret in my later test.

I found this great scheme on a pdf, however I'm unable to gain access: https://pubs.acs.org/doi/abs/10.1021/ie50580a035 it shows the reaction requirements and equilibriums which is super understandable.

After 3 hours the heat was turned off and the beaker was left on the hot plate to cool slowly. Nice wide plate crystals formed and in about 30min. the solution froze solid. I chiselled the solid cake out and put to storage in an airtight container.

Yield:
Using 300ml of AdBlue (which is written to be 32,5% solution of urea in deionized water) I expected a yield of 97,5g of CO(NH2)2. I got 97,44g of anhydrous CO(NH2)2, (97,44/97,5.(100%) = 99,94%) which is 99,94% yield! (I used approximate volume on the beaker, so that is very unlikely true) I lost alteast a gram or more to mechanical losses.

Product is stored in an air tight jar, and when opened still has a strong smell of ammonia.
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Fyndium
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[*] posted on 28-4-2021 at 05:04


When I recovered urea and AN, I poured the stuff into large oven pans and put a fan blowing air over them. It evaporated most of the water, leaving a slurry, which could be concentrated further. On a good day, one can evaporate 1mm of water per hour, and this translates to 1L per 1m2 per hour. In very dry and hot climates this number is multiplied and most likely by far the best and cheapest method to remove water from stuff. Debris does not matter that much, as it can be filtered out easily.

Just an idea, as urea is very cheap low-level stuff that is usually used more in kg than g quantities. I've though AdBlue as well, but have had otc urea granules sold few € a kg so haven't had the need.

My urea does not smell of anything, though.
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RustyShackleford
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[*] posted on 28-4-2021 at 08:28


Overheating is very likely the cause of the ammonia smell. When evaporated AdBlue i boiled it in a large pot untill it was a slurry, then i evaporated it dry on some large trays at room temperature, no smell of ammonia at all.

[Edited on 28-4-2021 by RustyShackleford]
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[*] posted on 28-4-2021 at 19:28


Take the Adblue and slowly add drop wise to a container of acetone or ethanol. You should get urea crystals.

The solvent should be soluble in water and the urea should be mostly insoluble in the solvent for it to precipitate out.




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Fyndium
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[*] posted on 30-4-2021 at 06:28


How much solvent do you need per mL of adblue?

The presumption is that the stuff is sold in 10 and 20L canisters, so you will likely need ~100 liters of acetone to precipitate few kg of urea out.

It reminds me of NileRed video where he used acetone to precipitate remnants of some forgotten compound from a solution, and he ended up using 3 liters of acetone for few hundred mL of solution to crash it all out.

Remember, that what can be demonstrated in a test tube, seldom works scaled up, due to kinetics, economics, or usually both.
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