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Removing Mehq Inhibitor From Methyl Acrylate Monomer

mehq methylacrylate inhibitor purification

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#1 koraltptp


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Posted 29 August 2017 - 10:37 AM



I am mechanical engineer but need to do some work with chemicals. Since, i am not chemical engineer, i am very far for procedures here, and i need some helps.


• I want to remove mono-methyl ether hydroquinone, MEHQ, inhibitor from 10 ml Methyl-acrylate MA monomer. 

• The MA bottle contains >%99 MA, and about 100 ppm MEHQ.

• I read from an article that they did by washing MA three times with 0.1N aq sodium hydroxide NaOH to remove the MEHQ. I also read other sources, they use either column chromatography (I guess this option is very slow procedure for MA ), or washing. 

Since i am not chemist, I don't know exactly how to perform this "washing" operation. 


For example, MA is "liquid", aq solution of NaOH is also "liquid".

How you can wash liquid with a liquid ? 

I guess they will become mixture of 2 liquids. 

But as i know both MEHQ and NaOH are solid particles floating within liquid.

So, does NaOH and MEHQ subside as soon as both liquid is mixed ? 


So, Can someone describe me the procedure and physics behind ?

Then, i can have more sense about how to perform this action.



Edited by koraltptp, 29 August 2017 - 11:55 AM.

#2 latexman


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Posted 29 August 2017 - 11:39 AM

What scale are you talking?  Lab scale - mL's of MA.  Plant scale - millions of m3.

#3 koraltptp


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Posted 29 August 2017 - 11:55 AM

I would like to use 10 ml of MA.

#4 MrShorty


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Posted 29 August 2017 - 12:44 PM   Best Answer

MA and H2O are mostly immiscible. Not as immiscible as oil and water, but they will form two liquid phases when mixed.


Going back to Chem 101 (or maybe even secondary school chemistry), you should recall that NaOH is a strong base. The one phenolic OH group in MeHQ (MeO-benzene ring-OH), is weakly acidic. Recall from those earliest chemistry classes that mixing a strong base (in excess) with a weak acid will yield a salt. The phenolate salt, like NaOH, is insoluble in the MA rich phase, but will be very soluble in the aqueous phase. The caustic wash takes advantage of the acid-base neutralization reaction to pull the MeHQ out of the organic into the aqueous phase. Decant off the organic phase to get the MA (plus whatever water gets dissolved in the MA).


Basic lab procedure I would expect.


Add 10 mL of MA to a suitable vial, test tube, whatever.

Add enough caustic to completely react with the MeHQ (at 100 ppm, it should not take a lot).

Agitate and wait until reaction is complete (should not take long).

Decant off organic phase.

Remove water from organic phase, if needed.

#5 koraltptp


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Posted 24 September 2017 - 07:07 AM

So, now i will have two liquid phases, 1) MA is pure, and 

2) water phase containing MeHQ and NA+, and OH- ions.


I can separate them via separator funnel and get MA out of mix. Now, Water left with contaminants.


How can i separate water from contaminants ?

Is distillation a suitable method to take water out, and left behind MeHQ and NaOH ?


By the way, water feed to system initially is Deionised, i wanna get "Deionised water" at the end as well.

Edited by koraltptp, 24 September 2017 - 07:08 AM.

#6 MrShorty


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Posted 25 September 2017 - 10:06 AM

One small quibble -- the MA is not quite pure, because there will be some water dissolved in the MA phase. I can't say from this side of the internet exactly how much water will be present in the organic phase, but there will be some. Likewise, there will be some MA in the aqueous phase. You don't indicate if that "mutual solubility" is important to what you are doing, but I will remind you that it is there.


I don't see any reason you could not distill the aqueous phase to recover the water. You would need to decide if you want to run the distillation all the way to dryness, leaving the dried salt crystals behind, or if you want to leave enough water behind to keep the salts in solution. There will also be some MA in your distillate, so you may need to consider whether or not you need to keep the first "cuts" from the distillation separate from later cuts -- depending on how much MA contamination of your final deionised water you can tolerate.

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