DEF storage info and Life chart.

[dickandlois]

Can not remember seeing a chart and information on how long DEF will remain viable related to time and temperature so this link might help answer that question.

     The general information reminds users to store it out of sun light, below 77deg. and in a closed container; an to clean up any areas pron to evaporation and crystal formation. 

https://www.fcsdchemicalsandlubricants.com/main/additionalinfo/DEF Shelf Life and Fluid Quality.pdf

 

     Rich.

[wayne77590]

The article had me worried there at the beginning as I was wondering how thr DEF in the tank would be affected.  I find it strange that DEF stored in its original container is affected but DEF in the vehicles DEF tank is not.

[dickandlois]

36 minutes ago, wayne77590 said:

The article had me worried there at the beginning as I was wondering how thr DEF in the tank would be affected.  I find it strange that DEF stored in its original container is affected but DEF in the vehicles DEF tank is not.

Wayne, The Def in the Tank is affected. By temps over 77 degs. and degrades over time  per the original post. 

Rich.

[jleamont]

Anyone running DEF, I strongly recommend purchasing one of these and keeping an eye on the DEF quality.

https://www.etrailer.com/Tools/Performance-Tool/PTW16500.html?feed=npn&gclid=EAIaIQobChMI4K20qZr94QIV3lcNCh11aQh1EAQYAyABEgKXRPD_BwE

They also make test strips, those are more for identifying contamination. I.e. fuel, washer fluid etc. 

 

[fagnaml]

This is a fun topic for the chemical engineer in the group.   The DEF fluid is prepared by mixing urea with water which is the "carrier" fluid.  At low temperatures, the urea remains as urea in the urea / water mix.  However, as the temperature of the mix increases, the urea will begin to hydrolyze to form ammonia and carbon dioxide as follows:

CO(NH2)2 + H2O >> CO2  + 2(NH3)   --> or urea + water >> carbon dioxide + ammonia

As the temperature of the urea/water mix in storage continues to increase, more ammonia and carbon dioxide begin to form and evolve out of solution (i.e. become vapor).  As more urea converts to ammonia and CO2, the urea concentration in the DEF decreases which results in using more DEF in the selective catalytic reduction (SCR) "reactor" in the exhaust system to convert nitric oxides (NOx) to nitrogen in water.

In the SCR, when the DEF is initially injected it quickly converts to ammonia and carbon dioxide due to the high exhaust gas temperature.   In the presence of the SCR catalyst, the ammonia reacts to convert nitric oxides (NOx) in the exhaust to nitrogen an water via these steps:

Urea to ammonia --> CO(NH2)2 + H20 + heat >> CO2 + 2(NH3)

NOx to Nitrogen -->  NOx + NH3 + heat + catalyst >> N2 + H2O

The SCR reactor will use the DEF it needs to use to convert the NOx in the exhaust to nitrogen and water.   "Degraded" DEF (i.e. DEF with lower concentration of urea) means that more of that "weaker" DEF will be used.

For reference, below is a good image of a 2008 or newer diesel exhaust system.  The "CO Reduction" step is the traditional "catalytic converter" all vehicles have had for the last 25+ years.   Hope you find this info useful.

 

 

[dickandlois]

Mike, Thanks for the information and the chemical formula . This information would ex plain -I thinking, why the DEF looks milky as it ages ?

Glad you found a post right in your sweet spot.  Kind of like Chemistry 102 on this end. 

Like learning how transistors worked way back when they where more of a curiosity then the main stream item of today. 

Rich.