Sciencemadness Discussion Board

PC - an otc source of formic acid ?

BASF - 15-7-2007 at 11:26

Hello all!- It´s been a while since my last post, so i´m glad to contribute again :)

The idea is to cook Polycarbonate from compact discs and the like with concetrated NaOH sol. and get valuable formic acid + bisphenol which could be seperated by extraction or recrystallization.

I am in an early stadium with this idea, so any ideas and suggestions are welcome!

Nerro - 15-7-2007 at 13:30

bisfenol-A is a nerve toxin. I believe it can screw up your reporductive system. Look out.

And you would be left with carbonate and not formate.

not_important - 15-7-2007 at 20:57

Nerro has it, polycarbonates are called that because they are polymeric esters of "carbonic acid" [-R-O-C(O)-O-R-]n , treatment with NaOH is going to yield sodium carbonate.

Bisphenol-A is a hormonal mimic, somewhat similar to diethylstilbestrol, it also appears to be able to trigger obesity (some other estrogen-like compounds act similarly) The only neurotoxicity reports that I know had to do with embryos, appearing to cause early cell death in undifferentiated nerve cells. I don't know if that's been confirmed, I suppose that if you're an embryo in fairly early stages of development it would be good idea to avoid exposure to bisphenol-A.

BASF - 16-7-2007 at 12:34

Thanks for the feedback,
i see it now, it should have been obvious :(

What about phenoplasts ? they are made of phenol + aldehyde.

A)Phenoplasts should directly break down into the aldehyde and the phenol upon thermal decomposition.

B)At least the phenol should be recovered via NaOH treatment of phenoplast and after acid workup of the phenolate.

A question is still where to get phenoplast-waste these days..

[Edited on 16-7-2007 by BASF]

not_important - 16-7-2007 at 15:02

No go - the basic reactions in the formation of phenol-aldehyde resins are (with Ar being a phenol)

Ar-H + COH2 => ArCH2OH, + Ar-H => Ar-CH2-Ar + H2O

so you've now methylene or other alkane bridges between the phenolic rings. Heating brings about decomposition, but no simple products.

Nick F - 17-7-2007 at 05:54

Here in the UK formic acid is sold OTC as a limescale remover, for kettles, boilers etc. I used it straight out of the bottle with semicarbazide to make triazolone, for NTO (3-nitro-1,2,4-triazol-5-one, a relatively insensitive high explosive comparable with RDX). I can´t remember the brand name, but it was sold in little yellow bottles in B&Q, near the "One Shot" drain cleaner that we all know and love. 250 mL bottles, I think. I also can´t remember the percentage (I did a titration, maybe I wrote the result down somewhere...), but I think, if I remember correctly, that it was about 60%. There may have been other crap in there, but as far as I could tell it was just a solution of formic acid. There was no soap.

DeAdFX - 17-7-2007 at 21:20

If you don't mind doing a little work I believe formic acid can be made from glycerin and oxalic acid. While not OTC per se it is possible to make it from fairly common chemicals. I believe organic synthesis(website) should have a procedure for this.

not_important - 17-7-2007 at 22:37

Alternatively make chloroform from ethanol and bleach, evaporate the aqueous part to get sodium format. If you don't want the CHCL3, after the ethanol has been consumed add excess NaOH and warm the mixture for a long time to convert the chloroform to additional formate.

Axt - 18-7-2007 at 06:03

Originally posted by DeAdFX... I believe formic acid can be made from glycerin and oxalic acid. While not OTC per se .... I believe organic synthesis(website) should have a procedure for this.

Oxalic acid is OTC as a "stain and rust remover" 2kg for cheap, distillation with glycerine gave me at best ~30% formic acid solution (from its density), never reached the theoretical concentration of ~56%. Though this worked fine for NTO, as brought up by Nick F.

The procedure is in Practical Organic Chemistry by Cohen in SM library.

Ephoton - 9-3-2008 at 03:47

"Alternatively make chloroform from ethanol and bleach, evaporate the aqueous part to get sodium format"

does the haloform reaction work on alcohols I thought it only worked on methyl ketones.

not_important - 9-3-2008 at 05:21

Alcohols are oxidised by hypochlorites to the corresponding aldehyde or ketone. Ethanol give acetaldehyde, which undergoes the haloform reaction, isopropanol gives acetone. Ethanol has the advantage that it directly gives formate and CHCl3, which can be hydrolised primarily to more formate.

Ephoton - 10-3-2008 at 00:16

got you so instead of three moles of hypochlorite per mole of ketone you need four moles per mole
of alcohol.

I have been told that the reaction requires heat then once it starts it is extreamly exothermic. I would guess this means that to create the aldehyde heat is needed to be put into the system but to do the classic haloform heat is given off.

[Edited on 10-3-2008 by Ephoton]

Aqua_Fortis_100% - 19-5-2008 at 15:27

But how to obtain high concentration formic acid from formates?

The only way my little brain can think is, like acetate, reacting the anhydrous formate high % H2SO4 and destill to make it concentrated.. But IIRC, does not formic react with H2SO4 to give out CO ??? :o

Nick F - 19-5-2008 at 15:35

Indeed it does. Maybe phosphoric acid could be used? I'm not sure...

S.C. Wack - 19-5-2008 at 15:56

Formic acid is slightly difficult to make from formates and H2SO4 due to decomposition of the acid in the heat of the reaction. In the example given in GB190920893, 300 parts of around 84% H2SO4 is cooled and 340 parts of dry sodium formate is added with stirring and the temperature maintained at 10-15°. After the addition is complete, the temperature is allowed to rise to 30°, when the temperature suddenly rises, and is kept below 85-90°. The mixture is stirred for 30 min. at 75°, and is then vacuum distilled, giving 280 parts 81% formic acid in 98% yield. By using 93-96% acid and keeping the temperature at addition below 10°, and by using serious cooling on the exothermic part of the reaction, they claim 249 parts 90.3% formic acid, yield 97%.

US1666437 suggests the use of calcium formate, which unlike sodium formate is not hygroscopic, and does not react so quickly with H2SO4 and therefore does not have such an exotherm to deal with. Even so they use cooling, even though their formate contains almost an equal amount of NaCl due to their process of making it, and formic acid is added as diluent (60:40:40). The formation of calcium sulfate coating and solids slows down the reaction but also makes it more difficult for the formate and sulfuric acid to mix. They speak of kneading the mixture!

Aqua_Fortis_100% - 19-5-2008 at 21:48

S.C. Wack , thank you for this info.. I will check out these patents. It seems to be a good way, although I still like the oxalic/glycerin method.. Oxalic acid can be made from sawdust, NaOH, lime and dilute H2SO4 (according with very great papers you and not_important attached in another thread), and with this you can recover the NaOH (using lime) and use that several more times what make it still more OTC. Also, a small amount of formate is produced in this process along with oxalate, but I dont know how to better stract it, since is usually a small amount. I have tried it.. The procedure is somewhat tiresome and messy, but is also easy and finding the reactants are even more.

I just dont remember so well, but in megalomania page he recommend to use anhydrous precursors to get better concentrations of formic..I'm just wondering how strong the destilate can be, since a small amount of water is either produced or present with reactants even in an "anhydrous" state (just guessing :P )..

little off-topic:
Nick F , how much % is your limescale remover and how much TO you produced using this product (yield)? Do you make your own SCA*HCl or just buy it? Also, what was your yield of NTO?
Long time ago I have heard (microtek, IIRC) that using lower conc. formic to make TO will give poorer results in overal yield... Did you find this true with your experiment?


[Edited on 20-5-2008 by Aqua_Fortis_100%]

Picric-A - 18-8-2008 at 01:11

one could use sodium hydrogen (bi)sulphate to distill of formic acid from formate salts.
One problem of making formate slats via the bleach/ethanol haloform route is there will be a significant quantity of NaCl impurity in it form the hypochlorite so as well as distilling of formic acid you will be distilling of HCl:o:(