Acid recycling/recovering

[stanfield]

I usually make PETN. At the end of the reaction, you have to precipitate the mix in 5L of water then filter the dilute solution, ok but it there a way to filter out the PETN directly from the concentrated acid for, after, distilling it with sulfuric acid to get back some 98-99% "new" acid ?

This step is impossible with normal filter paper... is there a technique ? I know the industry do this...

thanx !

[nbk2000]

Have you ever tried using a buchner funnel with vacuum? That's how the pro labs do filtrations of thick solutions.

[stanfield]

ok, but, on the buchner funnel, you have to place a *filter paper* and the concentration of the acid is about 70-80% (don't remember exactly), what the vacuum do ? Acid will "heat" paper, no ?

bye !

<small>[ December 11, 2002, 02:10 AM: Message edited by: stanfield ]</small>

[nbk2000]

That's why you use "acid resistant" filter paper. Or, you could nitrate a regular paper filter into nitrocellulose and use that instead.

What happens when you suck on a straw? That's what the vacuum does. :rolleyes:

[stanfield]

yeah, I found this filter paper in one of my catalog ! A bit expensive but producing nitric acid always takes me many hours ! This will help me...

All I have to do now is to invest in a buchner funnel... and a little pump.

thanx for all !

[zaibatsu]

For cheap acid-resistant filter paper try woven glassfibre matting from GRP (glass reinforced plastics (Fibreglass)) suppliers.

[stanfield]

If some milligrams of PETN passed through the filter, what effect will it have when redistilling with sulfuric acid ?

(sorry for my bad english !)

thanx.

[aster]

i have another question about H2SO4, my 98% H2SO4 turn dark on storage, i think it form some carbon that crust at the inside of the plastic bootle, how to prevent this happen? i closed the bottle tight and store them away from light. is the acid became weakened so much from this changes? thanks

[Mr Cool]

It sounds like it might be attacking the plastic, H2SO4 doesn't go brown if pure (I once got some 98% H2SO4 on the plastic housing of my scales, which turned it slightly brown in a few seconds).
I'd move it into a glass bottle if I were you, in case it does eat all the way through the plastic.
I doubt the concentration of your acid has been significantly affected.

[aster]

thanks, i will changes my container to glass, actually i have try to made picric acid with aspirin disolving in this (Brown)H2SO4, it's OK

[stanfield]

By filtering out PETN directly from concentrated HNO₃ at the end of the reaction with such buchner funnel, I have to know if PETN is soluble in concentrated nitric acid...
I wasn't able to find any information all over the net about this subject.

This is a major problem because :
when you've filtered out your PETN, you get back your nitric acid which has a concentration of about 80-85%. Ok, but to concentrate it again, you'll have to distill it with sulfuric acid and if some PETN still remains in the boiling flask, what will happend upon heating ? :confused:

thanx...

[rikkitikkitavi]

may I suggest the following:

vacuum distill the HNO3/H2O/PETN mixture until almost dryness (or rather a thick slugde in the flask. Low temperature will probably not trigger a reaction with the PETN, and the PETN will of course not distill over.

The remaining sludge in the flask can be dispered, burned or something similar suitable to do with it (really I have no clue how to do this safely :)

If you search there are many patents covering recovery of nitration acids, most of them considering a mixture of HNO3/H2SO4/H2O/nitrationproducts.

Generally the idea is to heat the mixture so that any organic matter is decomposed by the nitric acid but the patents doesnt cover the possible dangers involved .

/rickard

[stanfield]

ok, thanx, I'll search...
Do you think I could loose many grams of PETN by filtering it out with this method ? The yield is impressive each time I make PETN but anyway, I don't want to loose too much product !

EDIT : huh... I did some search and it's hard to find something... I goto this site : <a href="http://www.uspto.gov/patft/" target="_blank">http://www.uspto.gov/patft/</a> then did many search with words like "recovering" "recycling" "nitration acids"...
So, if you already found/know a patent cevering the subject, could you give me the number please ?
thanx.

<small>[ February 05, 2003, 04:32 PM: Message edited by: stanfield ]</small>

[rikkitikkitavi]

Stanfield I recommend :
<a href="http://ep.espacenet.com/espacenet/ep/en/level1.htm" target="_blank">http://ep.espacenet.com/espacenet/ep/en/level1.htm</a>
european patent database since it is much better than uspto

Unfortunately I dont have any patents right now but,

it covers all patents world wide,and is searchable for keywords back in time (which usptp isnt only 1975 onwards, they are slow scanners :)

you can also search for classification (click on classpat), i e you can find all patents covering a topic

C01B17/94 Recovery of sulfuric acid from nitration acids
C01B21/46 Nitric acid , purification, separation
C06B25/32 explosives, composition... the compound beeing nitrated pentaeritritol

as a few exampels.

/rickard

edit/ a quick search for "nitric acid + recovery + nitration" gave 30+ answers :=

<small>[ February 07, 2003, 01:07 PM: Message edited by: rikkitikkitavi ]</small>