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Author: Subject: Formic acid from Hexamine/HCl?
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[*] posted on 6-12-2008 at 14:14


Formic acid forms a maximum bp azeotrope ( about 107C) so simple co-distillation not quite straight forward.
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[*] posted on 12-6-2011 at 18:49


Finally got around to trying this out. First I had a go at making formic via H2O2, CH20, CaO and some Sodium Metaborate as catalyst. I followed a combination of Patents that I'll discuss in another thread. The result was a doe like material that you have to knead by hand! and you need some formic as well.

I reacted Oxalic with Clycerol about 10 times. 110 - 120 deg C. I have about 4L and according to it's S.G, it's about 48% formic acid. How do I proceed from here?

I guess first I fractionally distill to get rid of any Allyl alcohol. How much of it should I expect?

Then I suppose I use vacuum, but I don't know what I'm doing from here on. I tried to find an article at my local university where the guy ends up with about 77%.

"The Vapour density and some other properties of formic acid" by A.S. Cooldige JACS 1928, 50, pp 2166-2178."

But they don't have the printed version available any more, just electronic access. To make things worse I don't have a credit card, or have a single friend any more. I used to get everything through my girl friend because he was a student there but now she's gone so is sex and access to any journal I wanted. I can't decide which one I miss more!

Anyway, does anyone have a copy of this article or point me in the right direction. I don't need to be spoon fed. I love doing my own research but I'm very dissapointed at what the university has done. Let's not throw away our real printed books!
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[*] posted on 4-10-2012 at 01:57


I thought I'd give Formic acid a good work out rather than talking about it. Please note that I am not a trained chemist so If you see some obvious errors or areas in need of improvement please say so. S.G was calculated using A grade volumetric flasks at temperature and referenced to a Formic Acid specific gravity table by CRC that I downloaded from this forum, so the concentrations I quote are approximate only.

All H2SO4 used was commercial grade. All temperatures are in deg celcius. This is what I did.

To start with, I chose 3 relatively easy sounding methods.

1) Calcium Formate + Sulphuric acid.
2) Sodium Formate + Sulphuric acid.
3) Glycerol + Oxalic acid.

I started by making Calcium formate via patent: US 5,248,818.
Ca(OH)2 + CH2O + H2O2 using Sodium Metaborate as catalyst.

Na2B2O4 was made via US 3,300,278. Borax + NaOH. MgO also used.

MgO was made via US 3,127,241. MgSO4 + 2NaOH. NaCl also used.

Sodium Formate was made via Glycerol AR and Oxalic acid commercial grade.

Formic acid was made using the following patents as a guide: US 1,666,437, US 2,886,425 and a German patent translated by a British agent. Can't remember where I got it from, I think from this forum. No 20,893. 1909. "Improved manufacture of concentrated formic acid from formates".



Synthesis of Sodium Metaborate Tetrahydrate.

190.7g Sodium Borate decahydrate. 0.5 moles
53.5ml 50% NaOH. 0.68 moles
24.2g dH2O
0.07g MgO
0.83g Na2B2O4.4H20 (for seeding) Didn't have this yet.

Borax was placed in a 500 ml beaker. Water added then NaOH. A mixture like wet sugar formed. Heated to 93 deg C with stirring. Added MgO. After 45 min it was vacuum filtered through a glass fibber filter. Transferred back to the beaker and heated. At 78 deg, a few drops of NaBO2 was added. (This was made by the classic method in a furnace, crushed and dissolved in water).

Cooled to 54 deg C but nothing crystallised. Added 25.4ml 50% NaOH and heated at 93 deg and added MgO again, filtered then kept at 54 deg all day. Nothing happened. Heated to 90 deg, evaporate some water then product started appearing. Cooled to 54 deg, till water seemed gone then broke up the pieces in a motor and pestle then back on the hot plate to dry the powder.

Yield 197.7g with an average of what appeared to be NaBO2*7.32 H2O). Very unhappy with what I did.


Synthesis of Calcium Formate.

(1)
CaO + 2CH2O + H2O2 --------- Ca(HCO2) + H2

36g CaO 96%. 0.617 moles. Lab grade.
108.9g CH2O 34-38% (assumed to be 34%)
76.9g 30% H2O2
0.44g Na2B2O4¥7.32H2O
369.6g dH2O

CaO, CH2O, Na2B2O4 and water was placed in a 1L RBF on a water bath. Used an overhead stirrer and a100ml dropping funnel loaded with H2O2. First the solution was heated to 55 deg C, then as the H2O2 was introduced, the temp went up fast so ice replaced the bath. Max 55 deg.

After addition and at 40 deg, ice was removed. Temp rose to 51 deg and fell after 15 min. Colour was light brown. It was 46 deg after 25 min of stirring. Final temp was 44 deg. Filtered straight away but is better to wait till sediment settles. The filtrate wasn't clear so a GF/C filter was used. Poured into a 1L beaker and evaporated on a hot plate. As it was heating up, lots of bubbles was evolved. Excess H2O2?. Crystals were white but there was a brown sticky residue Yield 65g.

(2)
38.2g Ca(OH)2 97% 0.5 moles Lab grade.
81.3g 37% CH2O
62.4g 30% H2O2
300g dH2O
0.4g Na2B2O4*7.32H2O

Loaded Ca(OH)2, Na2B2O4, CH2O and water then dropped the H2O2 in 12 min. Max temp 55 deg. When filtered, there remained a lot of sediment, light tan/cream colour. Filtrate was slightly yellow. pH 14.

(3)
Repeated using more CH2O, 88.3g

Temp started dropping before the end of H2O2 addition as before, colour was the same. Final temp after ice was removed was 41.7 deg. Stirred for 40 min and temp was 33 deg. pH was 7.3. Very light yellow and hardly any residue. Again some bubbles were seen when heat was applied for evaporation. Crystals were pure white, no residue. Yield 64.2g. 95.9%

(4)
Repeated using plaster lime from hardware store.

43.6g Ca(OH)2 0.5 moles if it was 85%. Added H2O2 in 3min. No ice needed Temp max 47.2 deg. Failed. Dumped.

(5)
Repeated using Ca(OH)2 97% 0.5 moles Lab grade more H2O2 and Na2B2O4*7.32H2O.

68g 30% H2O2.
0.5g Na2B2O4*7.32H2O

Took 12 min to add the H2O2. Temp max 56 deg. Stirred for 30 min and left standing for 30 min. Filtered easily. Hardly any residue. pH 6.3. Yield 62g

(6)
Repeated using plaster lime from hardware store heated @ 1000 deg > 2hrs.

31.2g CaO 0.5 moles assuming 90%
88.3g CH2O 34%
62.4g 30% H2O2
300g dH2O
0.5g Na2B2O4*7.32H2O

H2O2 was added in 13 min. Stirred for 30 min. Turned orange. Failed and dumped.

(7)
Repeated using CaO from commercial CaCO3 as starting material.

29.3g CaO 0.5 moles if 96%.

CaC03 was heated @ 1000 deg > 2hrs and the resulting CaO was brown. Water was @ 40 deg when added. Temp rose over 10 min. Took 12 min to add H2O2. Reaction didn't appear to be as exothermic as when using Ca(OH)2. Some foaming developed as well which disappeared just before the end of addition. Temp max 55 deg. Colour was dark brown and a lot more residue than if using Ca(OH)2. Filtrate was pH10 and ultra clear. Pure white crystals

(8)
Repeated except for being a 4 mole run and using more H2O2.

544.2g 30% H2O2

Same procedure. Addition took 19.5 min. Max temp 60 deg. pH 10 and again very clean filtrate. Pure white crystals

(9)
Repeated the 4 mole run. Same amount of H2O2 but less Na2B2O4

2.7g Na2B2O4*7.32H2O
Same result.

In all experiments, the pH, if above 7 was adjusted with formic acid. Yield was very similar, between 95 and 96%.


Formic acid via Ca(CH2O)2 and H2SO4

(1)
1g Ca(CH2O)2
1.5g 95% H2SO4

Put 1.5g H2SO4 in a test tube with thermometer, sitting in an ice bath. When H2SO4 was @ 0 deg,
1g Ca(CH2O)2 was dumped in to see what would happen. Temp immediately rose to 60û then fell while mixing.

(2)
1g Ca(CH2O)2
1.5g 95% H2SO4
0.67g CH2O2

Test tube with 1g Ca(CH2O)2 and 0.7g CH2O2 was in an ice bath while 1.5g H2SO4 was dripped in keeping the temp below 10 deg. Became thick and pasty but more mobile.

(3)
50g Ca(CH2O)2
75g 95% H2SO4

H2SO4 was in a 250 ml beaker in an ice bath. Formate was added while stirring by hand. Temp was kept mostly @ 10 deg. Addition had to be very slow and careful at the start but faster towards the end. Towards the middle, it became very mobile then very thick at the end. Kneaded with a spoon for about 15 min. Kept in the ice bath for a few hours. Temp never rose after.

(4)
Repeated

Added slowly, kept temp below 8 deg this time it became very thin and mobile towards the end. Temp started to climb with only a fraction of formate to add. Removed from ice bath and watched it rise to 60 deg. Once again it had to be kneaded like doe.

(5)
150g Ca(CH2O)2
225g 95% H2SO4

1L beaker, ice bath, kept temp below or at 6 deg. Addition took 47 min. Stirred by hand. 45 min after the end of addition, when temp was above 25 deg, the reaction took off and reached 100 deg. Cooled in an ice bath and vacuum distilled. Yield 30.7 g. Didn't check concentration.

(6)
Repeated

Addition took 65 min, kept below 6 deg, then after 5 min temp rose rapidly as before. Distilled. Yield 34.9g. Didn't check concentration. Forget using an overhead stirrer.


Formic acid via NaCH02 + HCL

Dilute Formic acid was made with Glycerol and Oxalic acid, neutralised with NaOH and evaporated to dryness.

A 1L reaction flask was loaded with 169.3g NaCHO2 and 282.1g 85% CH2O2. Overhead stirrer and condenser was used.

(If you don't have any formic on hand, you can start with a small amount of formate and enough water to dissolve it. It won't affect the concentration that much, especially of you have a lot of formate.)

Became strongly heated as formate dissolved and gas was passed through it. More formate was added as gassing progressed. I thought a pH probe might give me an indication of when to stop but it didn't, in any case I stopped when it was at pH 0. Yield was 291.4g, it's S.G. was 1.2035 so the concentration was 89 - 90% according to the CRC table. Overall yield was about 63%, so I stopped too early.

I supposed I could have used scales while gassing, but what about if you were gassing 4 or 5kgs worth. How would you know when to stop otherwise? The patent just says that they add some more formate to account for the excess HCL. They also say that Formic acid is a good solvent for HCL.

If I had easy access to a tank of HCL I would probably like this method. It's fast and you get good concentration, but otherwise you have to use way too much H2SO4 for my taste. I tried using Ca(CH2O)2 but it didn't appear to dissolve in formic acid. I maybe mistaken.


Formic acid via NaCH02 + H2SO4

(1)
136g NaCHO2
230.6g 85% H2SO4

1L reaction flask (100mm opening), condenser, temp probe, overhead stirrer all a pot with a heating element and loaded with ice. H2SO4 was loaded in the flask and when @ 0 deg, formate addition commenced keeping temp under 5ûC. Removed ice and heated the flask. When reaction temp was over 70 deg, it took off and reached 97 deg and was kept between 75 and 80 deg for 2 hrs. It was very easily stirred. Left standing overnight. Removed stirrer and vacuum distilled.

Collected 107.1g. S.G. 1.1168. About 71% concentration. Overall yield about 82.6%

I made a mistake and used twice as much H2SO4. That's why stirring was so easy and also it didn't evolve much heat while adding formate and addition was really fast. I thought the formic acid would be all but destroyed but I got 82%.

(2)
544g NaCHO2
435.9g 90% H2SO4

Reaction was done in a stainless steel pot (304 grade). There was some reaction with the sulphuric acid and the pot. Kept temp under 10 deg. Used the overhead stirrer, then when more than half way, stirred by hand. Took 1hr 45min. Transferred to a 2L RBF and heated. When the reaction temp reached 60 deg, it took off up to 114 deg. The mass became rock solid. Vacuum distilled and collected 376.5g. S.G. 1.1945. Concentration about 85%. Yield about 86.9%


(3)
544g NaCHO2
412.8g 95% H2SO4

Reaction was done in a 2L reaction flask. Kept temp under 10ûC. When more than half way, Disconnected the overhead stirrer and using the same stir rod and paddle, stirred by hand. At the end of addition, the mixture had the same texture as slightly damp sand. Took 1hr 30min. Removed ice and temp rose over 1hr 30min to 40 deg. Heated then reaction temp reached 106 deg. Refluxed for 2 hours. Yield was 334.7g. S.G. 1.2010. Concentration about 88%. Yield about 80%

(4)
4,316.7g NaCHO2
3,383.6g 92% H2SO4

I wanted to see how this would scale up and how difficult it would be to get 2.5kg of formic in one go, so the H2SO4 was loaded in a 25L S/S pot (316 grade) and in an ice bath and a 1m long PE paddle. Started out easy enough, kept the temp mostly under 10 deg but when it got to more than half way the work load increased exponentially.

It took one person to hold the pot still and one doing the stirring and taking it in turns. The work out was sweaty and brutal. It was truly difficult to stir and mix this amount by hand for 4 hours. It became especially hard to keep the temp down when it got to the wet sand stage and had to mix fast in order to get the heat transfer happening.

Kept mixing the damp sandy stuff for another 1hr 30 min then transferred to a 12L RBF. Temp rose slowly over 2.5 hrs to a max of 81.6 deg. Let stand overnight. Next day it appeared to be semi solid so it was broken up, crushed and moved around with a PP rod. Heated to reflux for about 6 hrs then distilled. Yield was 2,897.3g. S.G. 1.2020. Concentration about 88%. Yield about 87.3%.


I didn't like the idea of having to use formic acid as a solvent just so you could stir the stuff. What if you didn't have any? Then I thought, does it have to be a solvent, why not something that has slight polar qualities that the formate can float around in and that won't react with anything? Why not the good old work horse DCM.


Formic acid via NaCH02 + H2SO4 + DCM

136g NaCHO2
102.2g 96% H2SO4
200ml DCM

200ml DCM was in a 1L reaction flask and the formate was spooned in. Floated around freely with no lumping. H2SO4 was dripped in via an equalising funnel and reaction was kept below 7 deg. Took 45 min. Removed ice at about 13 deg and temp went up slowly to 20 deg. Vacuum distilled and collected 86.6g. S.G. 1.206. Concentration about 87.5%. Overall yield about 82.3%.


Formic acid via NaCH02 + H2SO4 + CH202

(1)
272g NaCHO2
206.4g 95% H2SO4
107.1g approx 82.6% formic acid

Heat was very evident with even small amounts of formate addition. When more than half way through, it became to thick to stir with the stirrer so 20g for formic acid from the previous run was added. Temp immediately rose up to 40 deg. Cooled and slowly more acid. Total of 107.1g. Stirring was possible again and added the rest of the formate. Final heat of reaction didn't occur.

Heated to 75 deg for 1 hour then vacuum distilled. Yield was 175g. S.G. 1.1955. Concentration about 85%. Overall yield about 80.8%

(2)
544g NaCHO2
435.9g 90% H2SO4
426g 88% CH2O2

A 2L sealed reaction flask was loaded with CH202 and NaCHO2. Cold H2SO4 was dripped in using a pressure equalising funnel. Stirring was difficult but became easier as H2SO4 was added. A crust start develop on the flask wall that made heat transfer difficult. Kept under 10 deg. Took over 4 hrs. Stirred for 1 hr. Temp rose to 14 deg then fell. Mixture was a very smooth past. Yield was 390g. S.G. 1.2040. Concentration about 89.5%. Yield about 96.5%. Difficult method.

(3)
544g NaCHO2
435.9g 90% H2SO4
315.8g 89.5% CH2O2

Loaded H2SO4 in an open reaction flask. As formate addition progressed, more and more could be added without as much temp rise. When more than half way, mixture became thick and was sticking to the flask wall. CH2O2 @ -4 deg was slowly dripped in. As it became more mobile, formate addition continued, which resulted in a small temp rise and formic addition, in an acute rise. Towards the end, this reversed.

Max temp 10.1 deg. Sandy texture but very mobile. Took 3hr 45min. Removed ice. Temp rose slowly to 41.9 deg. Stirred for 6 hrs. Let stand overnight. Next day, texture seemed very smooth. Heated @ 80 deg for 1hr 30min. Became thick like porridge. Vacuum distilled. Yield was 392.9g S.G. 1.2025. Concentration about 89.5%. Yield about 95.3%. Easier method.

(4)
816.1g NaCHO2
639.7g 92% H2SO4
495g 89.5% CH2O2

Same setup but used a larger teflon stir paddle and drilled some large holes through it 6 X 16mm. Took 3hrs, stirred for 2hr 30min. Removed ice. Temp rose to 28 deg and became a thin liquid. Distilled next day. Yield was 569.5g S.G. 1.2054. Concentration 90 - 91%. Yield about 93.3%. Easy.

(5)
1632.2g NaCHO2
1279.4g 92% H2SO4
947.4g 89.5% CH2O2

This was done in a 4L beaker with an overhead stirrer. Took 6 friggin hrs. Kemp temp under 10 deg. Collected 2030.7g. S.G. 1.2046. Concentration about 90%. Yield about 89.1%.

6)
5000g NaCHO2
3,919.2g 92% H2SO4
3202.5g 89.% CH2O2

A 25L S/S pot covered with plastic wrap was used and a 4 vertical blade S/S stirrer was made and driven by an industrial geared motor. A larger pot was used as a bath and loaded with Ice/salt at -16 deg C. H2SO4 was added and allowed to cool to about -2 deg. Then NaCHO2 addition started slowly. After 2 kg of NaCHO2 was added, it became to thick to stir properly so formic acid was added via a sep and silicon hose in 500 ml lots, alternating with NaCHO2. Addition became faster with time and the Ice/salt bath made the whole thing really easy. Keeping the temp under 5 deg C was a snap and was mostly below 0 deg. The stirrer did a great job. Speed was only 2 to 2.5 rev per sec. Only took 4 hours. Very easy.

Only 3,027.5g formic acid was actually used in the addition. The other 175g was placed in a squeeze bottle and used to wash down. Transferred to a 12L RBF and placed it in the same cold bath and left overnight. Temp never rose above 7 deg C. No mixing, heating, nothing until actual distillation. Once again, simple vac distilled. Density 1.2076 about 91.5%. Yield about 90%.


Still to come are some experiments using Calcium Formate with sulphuric and formic.

So in conclusion, it was interesting, most of it was enjoyable but no matter how you look at it, it's a lot of hard and expensive work to get was is incredibly cheap to buy. So If you can buy it, buy it! That's what I do. On the other hand my lab supplier who used to be customer friendly and service oriented was bought up by a multi-national corporation. Now, they are impersonal and increasingly arrogant and tend to blame the client if they fuck up their accounting, so sometimes I make it as well as other things instead of contributing to the CEO's 2 million dollar kitchen make over.

Something I'd like to know. Does formic acid of any concentration degrade over time?



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[*] posted on 4-10-2012 at 02:02




[Edited on 4-10-2012 by angelhair]
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[*] posted on 4-10-2012 at 02:17


Quote: Originally posted by angelhair  

Something I'd like to know. Does formic acid of any concentration degrade over time?

Highly concentrated (99%) decomposes over time to CO among other compounds, which can make the bottle containing it explode.




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[*] posted on 4-10-2012 at 02:29


That's quite a lot of experimental work - thanks for posting it! Couple comments:
- you mention synthesis of sodium formate via glycerol and oxalic acid. Where does the sodium come in? I'm familiar with the synthesis of formic acid by heating of oxalic acid in glycerol; is the formate prepared simply by also having some base (sodium hydroxide, carbonate...) present or is there more to it?
- you had a failed run using plaster lime. That stuff is mostly CaSO4 and the temperature you treated it at (1000C) is not sufficient to decompose it to CaO. No surprise that it didn't work.

As regards degradation, I recall reading that at or over 95% concentration there is a slow decomposition to water and carbon monoxide.




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[*] posted on 13-11-2012 at 10:58


I noticed a couple other easy looking ways to make formic acid/formates.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2976561/
Oxidative degradation of reducing carbohydrates to ammonium formate with H2O2 and NH4OH
Looks way easy.

This way is not so easy, but has some really neat implications.
http://pubs.rsc.org/en/Content/ArticleLanding/2011/EE/C0EE00...
High-yield reduction of carbon dioxide into formic acid by zero-valent metal/metal oxide redox cycles
They reduce the iron oxide back to iron with glycerol, very cool!




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[*] posted on 13-1-2014 at 19:26


Fantastic work Anglehair!

I tried your last 25L synth and my results are on par with yours. Easier to buy if you can but very satisfing to make.

You say that you're not a trained chemist, but I can tell you that many college educated people will never do the kind of experimenting you have done.

One word of advice if I may, I've been reading your posts and in the one about H2O2 you were labeled as inept by someone feeling negative and bitter and probably has a short dick, who knows.

If you respond to these people you will only succeed in derailing your own thread as happened. Ignor these people and continue with your question. No one knows everything, some elitest here and everywere pretend that they do.

Any way, good work and thanks. I for one do not think you are inept.
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