Percipitate Formation in Propylene Glycol - Ethanol Solution

[bozroniancw]

I am conducting testing to find a fluid for a valve to be used in the petroleum industry; this fluid will consequently see exposure to gasoline and ethanol. Testing has consisted of bubbling ethanol vapor though a jar of propylene glycol, which is our leading candidate. Propylene glycol has all of the attributes we require for the proper operation of the valve, but as testing has progressed a white precipitation has formed in the propylene glycol-ethanol solution. The test setup actually bubbles air through ethanol fluid to pick up ethanol vapor and then bubbles through the glycol, as a result the solution is an open system with plentiful exposure to air.

I am wondering if anyone can tell me what this white precipitate most likely is. As the jars and fluid were clean when starting the testing, the most likely candidates are biological growth or chemical reaction precipitate. We are thinking chemical is more likely than biological, but have no basis for this. In either case we are also wondering if the development of this material, which is only small floating particles right now, will continue and become a problem by blocking flow passages. The test has been run for a week at a flow rate of about 15 SCFH, at 60F.

Any help will be appreciated.

 

[dcasto]

Can't you send it to a lab?

I'd guess it's a polymer of some form.

 

[bozroniancw]

I can send it off to a lab, but I thought I would try here first to see if anyone had any information at hand to save some time.

 

[aspearin1]

I did similar work for other reasons. I can't tell you exactly what it is, but it is possible that the precipate has more to do with the rapid cooling affect the air purge has on you fluid, rather than a chemical reaction. Does it go back into solution with heat? For me, it was a surfactant that precipitated out of a methanol solution. The house compressed air was very cold, coupled with the evaporative cooling of my solution. It was basically refrigerating itself.

Aaron A. Spearin
ASQ CSSBB
Engineering Six-S'$

http://www.Engineering6ss.com

"The only constant in life is change." -Bruce Lee

 

[bozroniancw]

aspearin1, I tried heating the solution, but the precipitate did not go back into solution. Thanks for the idea, but it appears i am not experiencing the same effect you saw with methanol solution. Do you have any other thoughts?