9 replies to this topic

[jooniore]

Hi! I am a chemical engineering student and I want to work on Styrene polymerization and i need to separate inhibitor (4-tert-butylcatechol) from the styrene monomer. However I've found some papers in which they had another inhibitor (monomethyl hydroquinone (MEHQ))and used the following procedure:

The styrene should be purified by extracting twice with 10% sodium hydroxide to remove the monomethyl hydroquinone (MEHQ) inhibitor, washing three times with distilled water, drying over a calcium hydride, and distilling under reduced pressure using a nitrogen ebullator (b.p. 820/100 mm.Hg).

So i was wondering if you think that this method can be applied for 4-tert-butylcatechol as well? I also want to know what if i skip the distillation step, which materials i will separate in distillation because the purity of styrene i'm using is 99.9%


Thanks in advance

[Dazzler]

G'day Jooniore

I used to work in a styrene monomer manufacturing facility but I am a little less knowledgable on downstream polystyrene plants.

A few points I can make on SM inhibitors:
1. TBC inhibitor is normal temperature use and shelf life improvement of the SM. It needs a little O2 to be present to be effective.
2. Some plants to make various styrene based polymers do not remove the inhibitor or pretreat the SM. It goes stright into the reactor as received. I guess in these case the reactor is heated therefore overcoming the inhibition.
3. When purifying the SM in the distillation area of a plant we would use high temperature inhibitors. If you wish to distill SM or mixtures of it, vacuum is normally used so that the distillation temperature can be kept below 100dC. You still need the high temp inhibitors but less of it. The higher the temperature the more styrene tars are produced (tary, black long chain molecules, even polymer), which end up being a waste stream from distillation bottoms. Common modern high temp inhibitors are DNBP for example (di nitro butyl phenol).
3. I haven't heard of MEHQ.
4. I'm trying to find out from a friend how TBC is removed when that is necessary. If I find out I'll make another post.

Dazzler

[breizh]

Hi ,
Let you try this link :
http://www.porocel.c...rification.html
hope it helps
Breizh

[Dazzler]

Joonoire

Further to my earlier message:

I saw that friend I mentioned at a housewarming party tonight. He says for some polystyrene polymerisation plants the TBC is removed or neutralised by contact with alumina balls in twin (duplex) vessels. Then downstream there is a filter to perhaps catch any alumina fines. The Alumina concept seems the same as mentioned on the weblink provided by Breizh.

Dazzler

[jooniore]

Thanx guys

I will give it a try.

[bobo]

Hi, jooniore

I am also doing removal of 4-t-butyl catechol. I wonder if you succeeded by using the sodium hydroxide and water?

Please let me know.

Thanks.

[Chanwit S.]

Hi Jooniore,

On laboratory scale styrene monomer purification, styrene monomer was washed with two equal volumes of 5% (or 10%) aqueous sodium hydroxide to remove the inhibitor (t-butyl catechol, TBC).The inhibitor free styrene was washed with four equal volumes of water to make sure it was nutralize (check by litmus) , dried over anhydrous magnesium sulfate.

If you start with styrene monomer which have contaminate more than you need in the final (contaminate such as benzene, toluene and ethylbenzene). Additional step needed. Styrene free TBC from above step should be distilled under nitrogen through a 20 inch Vigreaux column at reduced pressure (31^oC., 5 mmHg.). A middle fraction boiling over a 0.2^o range was collected, stored under nitrogen in a refrigerator, and used within three days.

I hope this can help you

Edited by Chanwit S., 01 November 2010 - 10:46 PM.

[cutter]

In regards to TBC MEHQ and DNBP, which one is commonly used as inhibitors for styrene in the US. Which is better or does the type of process determine the type of inhibitor used? Who are users of TBC in the US. Thanks.

[breizh]

Hi ,

Did you try google ? (list of producers in the US)
http://www.atsdr.cdc...les/tp53-c5.pdf

When I was involved in the production of latex , Styrene monomer was inhibited using TCB , other monomers were inhibited using HQ .

Hope this helps


Breizh

[Elizabeth_I]

Thank you so much for help! It seems clearer to me now;)