preperation of formaledhyde

[jfk]

Formaldehyde, or methanal can be produced by the first oxidation of a primary alcohol. Namely methanol, or methalyted spyrits.

This can happen just by leaving the bottle open to air for some time, or by chemical oxidation by a dichromate ion (Cr2O7 2-) or a permanganate ion (MnO4 1-).

Have you ever had sour white wine? this is the result of the second oxidation of a primary alcohol, namely ethanol.

first the alcohol is oxidised to its aldehyde (eth goes to ethanal, meth to methanal) then oxidised to its carboxylic acid.


Now, methanol is an odourless liquid, however if youve ever smelled formaldehyde, well it smells like rotting fish or something close...in New Zealand its rather hard to find formaldehyde due to its toxicity, and companies wont sell it unless you are a school or have a hazardous goods storage area.......so im going to embarke on making some out of methanol.

I know this can be done because i have the result of it in my cupboard, which i found today. I fould 1 litre of methanol in my cupboard which has been there for 5 years. (cap on) it smells like formaldehyde and also tests acidic so there is carboxylic acid there also.

So if you left it with the cap off, it would obviously oxidise faster. However, i was wondering what you guys think about this, would you be able to extract the formaldehyde from the mixture, if not would the small ammounts of carboxylic acids + left over methanol be a problem in reactions with it? I was thinking RDX but i cant figure out what the fuck paraformaldehyde is since para is telling you on which carbon the aldehyde is but formaldehyde (methanal) only has one carbon so it shouldnt matter........

and so its RDX, HMX actuayl those are the only ones i can find ATM

[Flake2m]

I was going to post a topic on this... you beat me to it.

I am currently doing basic organic chemistry ATM. While I was reading my chemistry text book on this module. A section on converting alcohols to aldehydes was brought up.

The textbook explained, that if you added a suitable oxidiser to a primary alcohol you can convert it to an aldehyde. The reaction would be something like this:

Alcohol + Oxidiser --H2SO4--> aldehyde + salt.
Or
CH3CH2OH + Cr2O72- --H2SO4--> CH3CH2O + Cr2-

The equation isn't balanced, but I think you get the idea. If you use KMnO4 it will oxidise again it into a caroboxylic acid.
This process does have advantages, the first one being that you have a cheap raw material; Methylated spirits (yes I do know its mainly ethanol, but it should not matter). The only problom would either
1. getting hold of some DiChromate
2. controlling the permangenate reaction so it only produces the aldehyde

[Mr Cool]

Check suppliers of photographic chemicals for potassium dichromate.
IIRC, potasssium permanganate in alkaline solution is less vigorous than in acidic solution, and since you're distilling the aldehyde out as it is formed (or in the case of formaldehyde, just allowing it to escape), it may be possible to use it. Even permanganate in acidic solution will yield some formaldehyde I would have thought, which will escape and be collected, and the formic acid can be processed as below.
If you end up with methanoic/formic acid, just neutralise it with calcium carbonate, collect it as crystals, dry, then thermally decompose it to produce formaldehyde gas. You lose half your methanol as calcium carbonate, but the formaldehyde produced should be pure and in high yield.

Also, it might be worth investigating other oxidisers, like manganese dioxide, hydrogen peroxide + catalyst, or even doing it electrochemically..?

[megalomania]

You really can’t use something like potassium dichromate or permanganate to oxidize a primary alcohol to an aldehyde. The aldehyde is readily oxidized further to a carboxylic acid. You have to use a special selective oxidizing agent like pyrindium chlorochromate (PCC) or pyrindium dichromate (PDC). You can make PCC by adding pyridine to chromium(VI) oxide with HCl. The PCC is added to the alcohol mixed with a solvent like dichloromethane. The PCC is insoluble in pyridine from which it can be isolated, and it is insoluble in dichloromethane in which it has to be stirred, and can later be removed by filtration.

You may also wish to consider a method similar to the industrial method, run methanol vapors through a heated pipe stuffed with copper. I have a lab method of making formaldehyde that involves heating a loop of copper wire in a burner to red heat and plunging the wire into methanol. The odor of formaldehyde is quite apparent after a few heats and dips. This method is not exactly conducive to production, but it serves to illustrate how theoretically easy it should be to use the catalytic system of alcohol vapors and a heated pipe. I wrote a post some months ago describing the process.

If anyone wants to know how to make PCC I think I have a lab procedure here somewhere…

[FadeToBlackened]

Please do post that procedure if it's not too much of a hassle.

On a further note, I noticed that www.sciencemadness.org claims heating moist calcium formate will yield formaldehyde, but I've read that heating formates decomposes them to oxalates (?)

[John Ashcroft]

If the aldehyde is removed as it is formed from oxidation of the primary alcohol, realizable yields can be achieved.

[VX]

Formaldehyde, or methanal can be produced by the first oxidation of a primary alcohol. Namely methanol, or methalyted spyrits

Methylated spirits is not methanol... in fact, hardly contains any methanol at all. Typically it is around 95% ethanol (although this varies) with only the remaining 5% consisting of methanol, Bitrex, dye and other denaturants.

Two years ago, whilst I was at college we actually made aldehydes from primary alcohols by using the above method of heating with potassium dichromate, the reaction vessel was attached to a condenser to collect the aldehyde as it was formed, and delivered it to a flask. Yields were high (cant remember how high) and because the boiling temperature of aldehydes is much lower than both their corresponding alcohols and acids, they hardly vaporise at all, hence the product is high purity. Come to think of it, I thing that the reaction was self sustaining as it was so exothermic, and no external heat was required.

[Einsteinium]

Indeed formaldehyde can be removed from the reaction mixture as soon as it's formed but it's often difficult to achieve when water starts to be present in noticeable amount in the alcohol; a large amount of anhydrous alcohol must be used to produce quite small amount of aldehyde (as water is produced in the oxidation steps). Water interferes with the reaction because it reacts with formaldehyde producing formaldehyde hydrate, which is very easily oxidized to formic acid (and two molecules of water). Formic acid is too easily oxidized, to carbon dixodide and water. Formaldehyde itself isn't very reactive toward oxidation; in PCC oxidations, which stops at the aldehyde, the solvent used is methylene chloride, where PCC is soluble and where water isn't, thus the hydrate cannot form. It you have some oxalyl dichloride, DMSO, methylene chloride and CaCO3 (or better Et3N), you may want to try Swern's oxidation as it gives excellent yield but that would be rather costly for formaldehyde...

Swern's Oxidation http://www.orgsyn.org/orgsyn/prep.asp?prep=v77p0064
diPyrimidium Chromate (similar to PCC) http://www.orgsyn.org/orgsyn/prep.asp?prep=cv6p0644

[jfk]

Well, i knew that using a catalyst like permanagmate or dichromeate would be far to vigourous, converting the aldehyde into a carboxylic acid once it had formed, but i hadn't thought of those catalyists Meglo. Also the fact that methylates spyrits isnt methanol, well pure methanol is easily obtainable anyways from a local Reidel de Haen supplier(for me anywayS). Also thanks for that interesting copper pipe proceedure there Meglo, ill search for that and post it here also.

Plus, i waswondering if you were planning any updates to your chemical weapons pages ?

[xyz]

I have seen formaldehyde solution (About 20-30% IIRC) for sale in camping shops. I think it is used to stop mould growing on damp tents. It was reasonably expensive though, $10AUD for 1 litre. Perhaps you could try camping stores if you are looking for a source of formaldehyde.

[megalomania]

Preparation of pyridinium chlorochromate (PCC)

Place 18.4 mL (0.11 mol) of 6M HCl in a 100-mL Erlenmeyer flask, add a magnetic stir bar, and stir the acid rapidly. Add 10.00 g (0.10 mol) of chromium (VI) oxide to the acid, and stir the mixture for 5 min at room temperature. Cool the solution to 0°C in an ice bath, and add 7.7 mL (0.1 mol) of pyridine dropwise over 10 minutes with the cooling bath in place. Re-cool the solution to 0°C and collect the orange-yellow solid by suction filtration. Dry the solid under vacuum over phosphorus pentoxide for at least 1 hour.

I do plan on adding some chemical weapons info to my website eventually. I am working on a sarin prep right now, but to be thorough I am also figuring how to make all the precursors. Incidentially the info applies to soman, cyclosarin, cyclosoman, and pretty much every alkyl derivitative of sarin. I have decided to do my chemical weapons part all in XHTML, which is causing me trouble as I learn it. Eventually my entire site will be XHTML.

I know I can get paraformaldehyde solid and formaldehyde solutions at Wal-Mart. I hear it is not a simple matter of heating paraformaldehyde to decompose it to formaldehyde, although I may be wrong on this. I have never tried it myself, so I can not say. Does simply heating paraformaldehyde make formaldehyde? If so the Wal-Mart stuff would be a good choice.

[Marvin]

Pyrolysis of zinc or calcium formates are supposed to be a good source of formaldehyde.

Manganese dioxide does ok for production of acetaldehyde, but I'm not sure how well it would work with methanol. As pointed out formic acid isnt the end product of this reaction, so there might not be much to reclaim for pyrolysis. Permanganate in alkaline medium is less agressive, but aldehydes in alkali are just going to get destroyed.

Anyhydrous methods, and exotic oxidisers are all very well for complex molecules where yeild is everything. hardly worth it for formaldehyde and acetaldehyde where cost and availability of the reagents is rather more important.

For Acetaldehyde, one book recommends,
6 parts sulphuric acid.
4 parts az Ethanol
4 parts water,

Mixed and poured onto,
6 parts powdered manganese dioxide in a large container, with a reciver cooled by ice water.

Distill until 6 parts of liquid have passed over. The distillate is redistilled twice from calcium chloride, mixed with twice its volume of ether and saturated with ammonia gas, the adduct which ppts is then decomposed by distilling from 50% sulphuric acid, careful recification from calcium chloride, not exceeding 30.5C provides acetaldehyde pure and anhydrous.

I suspect simply knowing how much acetaldehyde is in the 6 parts distillate would suffice for most uses, the impurities being mainly water and alcohol.

Edit, Meg snuck in while I was typing.

Heating metaformaldehyde or paraformadehyde should be fine, possibly with a small amount of dilute sulphuric acid? Using them as is in most reactions is usually fine anyway.

On the subject of PCC, does anyone know an OTC source for pyridine? Currently the only OTC route I can think of, wouldnt be cost effective as I cant find niacin cheeply enough.

btw Meg, if you still need a synth for DDT, I have one.

[jfk]

Mega i was under the impression that you heated formaldehyde so it decomposed into paraformaldehyde..im sure i read that somewhere. I would be able to figure it out myself but all my links have been deleted (i wont go into it.....but boy it makes me mad).

Thanks for that camping store siggestion, would have never found it out my self. ill have to go check it out soon, as for $10 AUD / litre i think thats cheap !

[megalomania]

Thanks, Marvin, but I already have a synth for DDT. I do need to get around to writing that up…

I too have mulled on getting OTC pyridine the last few days. I wonder if it would be possible to make it from piperidine extracted from black pepper through some sort of dehydrogenation reaction? This would probably have to be some sort of industrial type reaction with high temperatures and a catalyst to work… Lets see, British patent 745,400 titled “Catalytic Dehydrogenation of Piperidine” uses platinum or palladium metal supported on silica gel. The piperidine is passed over the catalyst heated to 300-400 degrees with an excess of hydrogen. A similar US patent, 4,523,016, uses a copper/nickel/chromium catalyst under similar conditions. I wonder if either of these patents could be improvised on the lab scale. Neither patent mentioned industrial equipment, and indeed the second uses lab equipment, albeit of a more sophisticated nature.

[nbk2000]

Piperine is extracted from black (or white) pepper, then converted into piperidine, then finally pyridine.

I believe there's an electrolytic process for conversion mentioned in either Merck, or the C.A. index. That'd be the first place to start.

I (personally) think any process that relies on catalytic reactions is too hard, because there's so many variables involved, especially if it's a pyrolytic process.
Better to get results at low yeilds in wet chemistry, than to dink around wasting time and money aiming for perfect yeilds.

Also, if I remember correctly, if you continue the chlorination of DDT, you eventually get Dioxin. :)

[megalomania]

I agree that industrial caliber reactions tend to be a bit difficult to replicate on a lab scale, but I feel these types of reactions are just waiting to be explored by improvisational chemists. I think with the proper equipment one could feasibly do these kinds of reactions. It is just getting the equipment that is the hard part. I have noticed that the vast majority of these industrial reactions follow a common theme, pass chemical X through heated tube with catalyst Y and out pops chemical Z. Once someone works out a way to do this with one, all the others should work very much the same. I wish I had taken some chemical engineering classes, of course they probably only tell you about equations. I would prefer good old wet chemistry though. The unfortunate fact is most of your very basic common ubiquitous lab chemicals are best made through industrial type reactions.

The extraction of piperine from pepper is described in detail over at the Hive, or rather Rhodium’s website:
http://www.rhodium.ws/chemistry/3base/piperonal.pepper/piperine.pepper/index.html
The site also describes the conversion of piperine to piperidine here:
http://www.rhodium.ws/chemistry/3base/piperonal.pepper/degradation.piperine/index.html

I did see in the Merck that pyridine can be electrochemicially converted to piperidine. Perhaps that is what you saw nbk. Otherwise I think the only way to get pyridine would be from coal :(

[knowledgehungry]

I think that using potassium dichromate and sulfuric acid along with methyl alcohol will give formaldehyde. formaldehyde's BP is very low, as soon as it is formed it will boil off, or so i believe. Perhaps some of it will be further oxidized to formic acid but this synth is cheap enough that a slight loss in yeilds should not be a problem, you can reuse the dichromate over and over.

[vulture]

An even cheaper method, discovered by accident by polverone IIRC, is adding peroxodisulfate (persulfate) to methanol. The reaction did not need to be carried out in acidic environment IIRC.

[Marvin]

Looked at the black pepper stuff, primary extracting a 3,4 methylene dioxy phenyl compound. Gee what could they be planning to do with that :D

Unfortunatly I dont own a black pepper plantation, or it might be worth extracting the few percent of piperadine to convert to pyridine. Compaired to what should be a very easy synthasis from niacin, and with the current bulk price (for 25Kg ish) of black peppercorns, theres not a lot in it.

A few hundred grams of pyridine is fairly easily obtainable, but I need about a litre of pyridine to convert to the hydrochloride to use as reactant and solvent. >100US is
prohibitive for this amount for me. The cheepest Niacin I can find is about $15US for 100g.

[jfk]

ok i know that this thread is slightly old, but i have been inactive of late and i just read the recent post.

i wanted to recap on the posts about formaldehyde here.

if you use a slightly basic solution of potassium permangamate with sulphuric acid (reas high % ?) and methyl alcohol, formaldehyde will be produced, and because of its low boiling point (and using high conc chems) it will boil off hopefully before it becomes oxidised to formic acid.

and you can collect it in your condensor. now what i was hacing trouble with is getting high concentrations of sulphuric acid to do this (i could look around for battery acid and boil it, but i think there would be to many impurities? am i right?) that aside i have a bottle thats got mrthyl alcohol, formaldehyde and formic acid in it - does any one know if the boiling points of methyl alcohol and formic acid are higher / lower than formaldehyde?

or what they are exactly. ? because i might consider distilling this if i can get the right temperatures going. which would be good, then i would be back in RDX business.

[Tuatara]

jfk, you said you couldn't get formaldehyde here in NZ. Wrong!:D Try your nearest farm store, eg Wrightsons, or RDI. Formaldehyde is sold in 10l packs for disinfecting milking sheds. Theres lots of yummy things to be had in farm stores - go check it out

[vulture]

if you use a slightly basic solution of potassium permangamate with sulphuric acid (reas high % ?)

You cannot have a basic solution with free sulfuric acid in it. I think you got something wrong there.

There's a simple trick to avoid production of the carboxylic acid. Add it to the reaction mixture!
Carry out the oxidation in a solution of formic acid. Why? If one of the products is already available, this will shift the equilibrium to the left, to the aldehyde also.

Only possible problem would be an acid catalyzed condensation between formaldehyde and formic acid, but I'm not really sure of that.

[rikkitikkitavi]

vulture, about your last question, I wouldnt worry to much. At work we do have formaldehyde and formic acid together -no problem.

Beware that formaldehyde undergoes selfcondensation in alkaline solutions, and happily with other aldehydes. I am not 100 % certain about kinetics though, but I believe that it is quite a fast reaction.

Caustic + acetaldehyde is much faster and exothermic, which one of our storage tanks at work disovered when it found itself 600 m away .with its bottom valve blown out, beacause there was a backflow of caustic into the acetaldehyde. Strangely there was no fire. (this was in the 70s)

/rickard

[jfk]

ok thanks for that vulture. :) wasn't my mistake :P that post was like a summary of the posts in this thread.

ok living in rural NZ like i do, farm shops are close and plentiful :) thanx for that tuatara. i had been looking in the wrong place. supliers wouldnt sell to me because i dont got no dangerous goods liscence (bs you need one for it) and the only camping stores that sell it are in AUS

[Marvin]

Do the oxidation in formic acid and discover a great new way to make carbon dioxide. Formic acid isnt really an 'end product' as its a very good reducing agent itself, unlike the higher carboxylic acids. I'm also not convinced that simple product concentrations will have much of an effect on redox reactions, it doesnt seem to fit what we know about canizzaro reactions for example. In order to have any real bearing the reaction that produces the carboxylic acid, this would have to be usefully reversable under the same conditions, which it isnt.

If anyone can get hold of the large amounts of formic acid anyway, they would be better making zinc or calcium formate and making formaldhyde from these by pyrolysis.

[blindreeper]

Why would you want the stuff in camping stores? It comes in brown (what appears to be brown HDPE) 1L bottles for $9 and is of 23% concentration and is dyed blue. Honestly it has no uses. Is there any way to maybe boil off the formaldehyde and lead it into some ethanol to make a stronger solution?

[jfk]

uhm apparently those crazy australians use it to stop mould growing on tents.

i think static_firefly or someone else told me.

[blindreeper]

Aussies are not crazy, we took an airfield in the Iraq war and helped the USA out heaps. Well anyway thats OT. We don't use it to keep mould off tents it's for portable toilets.
Can anyone answer my question about making the formaldehyde more "useful"?

[0EZ0]

blindreeper, don't assume that because a chemical is dilute or it's appearance is startling, that it has no use. Formaldehyde solutions are actually rather useful for the production of hexamine.

Since Formaldehyde is a gas I assume that a solution of it can be heated to give off the gas. Or possibly the heat may evapourate some of the water giving a stronger solution, but I would think the formaldehyde would evapourate first. Be aware that without stabilisers the solution may form crystalline paraformaldehyde with prolonged storage. Commercially a few percent methyl alcohol is added to the solution to prevent such crystals from forming. Formaldehyde solutions are used widely in industry and can be found in most laboratories usually labelled under 'Formalin'. Solubility of formaldehyde in water can reach approximately 55grams per 100ml of water.

Maybe another avenue to explore is to produce a solution of formaldehyde from solid paraformaldehyde in an alkaline solution. Place powdered paraformaldehyde in distilled water and add a drop or two of NaOH/KOH solution to dissolve it. Heat the solution to de-polymerise paraformaldehyde back into formaldehyde?...

[blindreeper]

I thought that the formaldehyde had to be dissolved ion methanol so it wouldn't polymerise. So if I led the formaldehyde into water I'd be left with some nice paraformaldehyde crystals, which I would use for RDX.

[0EZ0]

I think you misunderstood my previous post blindreeper. Only prolonged storage of formaldehyde solutions will it polymerise, not all the formaldehyde polymerises into paraformaldehyde at once. I think it's only a gradual process.

Leading formaldehyde into water to get paraformaldehyde is not going to be as productive as you might think. In any case, paraformaldehyde is already available as a cheap OTC item that has wide use. Use 'Trioxane' as the keyword in a search should you want to explore that path.
I would advice you that to answer any more questions, first do a bit of searching on the topic, as it's most likely already been discussed. Bringing up the same thing over and over again is not productive for the forum and only serves to waste time and bandwidth.

On another note about the RDX, as a wise man once said, "You must first learn to learn to walk before you can run;) ......", as is the case in this hobby, trying to run without first learning to walk can very easily get you killed:( .

[blindreeper]

Not meaning to be disrespectful to you 0EZ0, but I think I am quite capible of walking. I have made several things like AP, HTMD, HDN, TNP and heaps of LE stuff. I know it's a slow process. And I don't intend to start making RDX in the next 6 months but it would be good to have the precursors on hand. I mean if you see a special on drain cleaner you don't just say to yourself "I'm not making any nitric acid today, nope I'm not buying it"

[Chade]

Has anyone looked into possible alternative methods of oxidising the methanol in this 'home-brew' formaldehyde method? If things like permanganates are too vigourous, there are loads of other oxidising compounds. Heck, we seem to spend most of our time discussing them. Would something like a chlorate work?
Given that Methanol oxidises if just left for a long time, the problem would appear (to me, a non-chemist) to be increasing the oxidation rate a bit, but not so much that you oxidise the formaldehyde in excess. Perhaps bubbling air, or even oxygen through the methanol would increase the rate of oxidation to a useful amount. I'd imagine that such a setup can be left running for days without too much trouble.
For example: Maybe set the meths in a bottle with a two-holed cork. A glass tube runs from one hole to the bottom of the meths, allowing air to bubble through when a low pressure is applied to the second hole. A tube runs from the second hole to a second bottle full of water, so any gaseous formaldehyde bubble into the water, where it dissolves. (Just like HCL, water can hold large quantities of dissolved formaldehyde) The second bottle also has a double cork, with the second hole in this case simply connected to a low pressure source. If you want it as simple as possible, just attach it to a T-junction of a tube connected to a tap. The tap water flows slightly faster at the t-junction and creates suction. (I'd be suprised if this method of suction hasn't been mentioned somewhere on the forum before)

I'll try this myself when I have time, but not before I've figured out a method of analytically testing formaldehyde that doesn't involve how strong it smells.

Just to clarify, formaldehyde bubbled through water dissolves and is often known as Formalin, or simply as formaldehyde. It seems quite possible to get 37-40% solutions without too much trouble. At such concentrations it won't form paraformaldehyde in the short term (e.g. weeks)
It's recommended you store Formaldehyde solutions in the dark and above 4 degrees C to inhibit paraformaldehye formation. You can always reverse this if you actually want paraformaldehyde, I suppose, but it's still not a quick process, and it's tricky to store something in a cold, light place. (Leave the fridge light on?)

Vogel's 'textbook of practical organic chemistry' includes a method for producing dry gaseous formaldehyde as heating paraformaldehyde at 180-200 degrees C. Or, if reaction temperatures top this, it says to just add paraformaldehyde and let it be produced in situ. I include this, as some people seem to be more easily able to access paraformaldehyde.

[kingspaz]

chade, the problem is, if i remember correctly, that aldehydes oxidise easier than alcohols.

[Chade]

Right, I had a good look into this. I've asked three professional chemists and three biochemists. It comes in handy to have scientist mates.
You can add certain oxidising agents to methanol to make methanal. potassium and sodium dichromate in acidified solution, and potassium permanganate (otc at the chemist) in acidic solution. Heat the solution to assist the oxidation. If there is any excess oxidiser than that required to make the formaldehyde, it then starts to oxidise the aldehyde to formic acid then carbon dioxide and water. So if you measure out the molarities correctly, you should be able to convert most of your methanol to methanal. Bubble this liberated gas through water to make a saturated solution and that's it.
My idea of bubbling air through methanol was not as far fetched as it seems, as it turns out that's the industrial method of making methanal. They use methanol at 400 degrees C, with a catalyst. As before, you stop when you run out of methanol. The catalysts used include silver (let's not, shall we?) or the more reasonable copper (yay!) at just 300 degrees C in the vapour phase with air. A method could be worked out with simple copper piping.
I'd also imagine H2O2 might work as an oxidising agent as well as it shouldn't give any nasty byproducts, other than adding oxygen to the equation.

I did say i was waiting for a titrimetric test, and I think I've found one. Just titrate potassium permanganate solution against the sample until it turns purple. That'll mean you've oxidised all the remaining methanol to methanal, then all that to formic acid. It won't take any more oxygen in the compounds in the solution.

Most of the essential info is here.
http://www.wikipedia.org/wiki/Methanal

[frogfot]

I found a very promicing method of formaldehyde preparation in one Russian book (Preparation of chemo-pharmaceptical substances M.M.Kacnelson 2:nd ed)

Method gives 160 ml of 40% formaldehyde from 200 g methanole, with very simple copper catalyst. Got some time to translate it, maby there are some members that want to try it out (I'll try it out hopefully in newyear holidays..).

Ok, here we go..
..my comments goes after //

"
Process:
CH3OH + O ==> H2CO + H2O

Following equipement is used to prepare formaldehyde:
http://www.geocities.com/frogfot/stuff/methanalapp.png (copy&past)

It consists of:
1. Washer with conc. H2SO4
//washer is probably optional, some air humidity shouldn't be a problem, else NaOH filter would be sufficient IMO

2. 500 ml round-bottomed flask with side output.
Flask is loaded with 200 ml pure methanole and closed with cork with dropping funnel (for additional methanole) and a pipe connected to washer. Flask is placed into 45-48*C water-bath.
//we don't need dropping funnel cause it would be easier to reload methanole "manually"

3. 30 cm heat resistant pipe, 1 cm in diameter. Copper coil, 3 cm in length, is located in lower part of pipe.
//any metal would do as a pipe, however I'm eager to test out my quarz pipe.

4. Two long necked 200 ml flasks. Both are immerced into ice-bath and connected in series as shown on picture.

When apparatus is set up, first, whole heat-resistent pipe is heated by a gas burner and then it's heated only where copper coil lies. Apparatus is connected to a good pump through flask (5), and strong air flow is sucked through.
//don't know what is a "good pump", but I would test 10 torr water jet pump

Air from H2SO4 washer will enter heated flask and mix with methanole fumes, produced gas mixture will pass hot copper catalyst where methanole will be majorly oxidised producing formaldehyde and water.
Reaction will produce great ammount of heat, if burner is removed, copper coil will continiue to glow for a long time.

Ubtained formaldehyde thogether with water and unreacted methanole collects in flask (4).
Described procidure usually yields 160 ml 40% formaldehyde, dissolved in mixture of water and methanole.
Formaldehyde that did not condence in flask (4), will condence in flask (5).

Yield depends on heating of copper catalyst. To strong heating may convert methanole partially to formic acid.

Paraformaldehyde (CH2O)n is ubtained by evaporating aqueous solution of formaldehyde in exicator above H2SO4.
"

Also, as a note they mentioned to use copper oxide, ubtained by following method:
Usual asbest is soaked in concentrated solution of copper acetate and then heated. Copper oxide will form on asbestoes fibers as very fine particles.

Comments/suggestions are more than welcome.

[megalomania]

As a matter of fact I have the exact same thing, but in English. I was writing it up a couple of weeks ago but I forgot about it. I will finish it off and post it in the next few days (with pictures).

EDIT: I guess I already had most of it written, so here it is...

Ahh sweet vindication, I have found a published procedure just like my proposed copper oxidation of methanol. Indeed this procedure passes copper vapors through a heated copper catalyst, and the best thing the reaction is a lab scale one! Without further ado I will reproduce this gem in its entirety.


The side tube (length about 10 cm) of a distilling flask (capacity 250-mL) is bent upwards at the junction with the neck of the flask. The end of the side tube, drawn out into a capillary (internal diameter 1.0-1.5 mm), is then inserted through a cork into a piece of combustion tubing about 30 cm long (fig 53). Within the tubing and about 6 cm from the point of the capillary is a copper spiral 4 cm long. The tubing slopes upwards at a small angle and its upper end is connected with a vertical condenser, preferably of the coil type. To the lower end of the condenser there are attached two communicating receivers which, during the experiment, are almost completely immersed in a freezing mixture. The short side tube of the second receiver is connected to the pump. Into the distilling flask, which is lowered as deeply as possible into a water bath kept exactly at 46-47 degrees C, 100 mL of methyl alcohol are poured. The flask is then closed with a rubber stopper, through which is inserted a glass tube reaching nearly to the bottom. Through this tube air is drawn in, and when the air is passing, the copper spiral is warmed in the flame, cautiously at first, until, when red heat is reached, the reaction sets in. The air current must now be so regulated that the spiral continues to glow quite feebly without further application of heat. If the experiment is carried out in this way there will be complete freedom from explosions. The region within which methyl alcohol-air mixtures explode is indeed reached when the temperature of the bath is too low (42-44 degrees C), but the flame strikes back no further than the capillary tube, since the rapid current in the latter prevents further striking back.

The two receivers contain 110-115 mL of a 30-32% formaldehyde solution after all the methyl alcohol has been evaporated. A further small quantity of formaldehyde may still be collected in a third receiver containing a little water.

The following paragraph contains some points which should be considered in carrying out gaseous reactions.

In order to dehydrogenate one mole of methyl alcohol 0.5 mole of oxygen is required, and hence for one volume of the alcohol half as much oxygen or two and a half times as much air. The stoicheiometrical must therefore contain methyl alcohol and air in the proportions (by volume) 1 : 2.5, ie. 28.5% of methyl alcohol. Since the volumes vary as the partial pressures the temp of evaporation (of the alcohol) must be so chosen that its vapor pressure shall be 28.5% of the atmospheric pressure, ie. About 210 mm of mercury. With the simple type of apparatus here described complete saturation of the air with methyl alcohol vapor is not reached, and hence a temperature somewhat higher than the theoretical is used.

[frogfot]

Never thoat about choosed temperature that way :) So, concentration of methanole can be estimated from its partial pressure, if air flow is not too high.

Autoignition made me worry.. for some reason my book doesn't mention this! But what if we pass large excess of air into apparatus, to lower methanole concentrations below danger? or, if we doesn't dip air inlet tube into methanole..

Wonder if 200 ml thick-walled filtering flask will hold explosion of air/methanole, else it wouldn't affect yields much, but it would be a scary synthesis..

[Marvin]

If you alter the air/methanol mix you screw up what you are trying to make. The problem isnt really autoignition as this happens in the combustion tube, the problem is striking back into the methanol flask, and this is prevented by the capillary. Provided the actual amount that can ignite is small, explosion shouldnt be a problem. It is always a risk with these sorts of catalyctic oxidations though. In any case this oxidation operates with a level of methanol above the explosive limit, so adding more air or forcing less to evaporate would make the system more likley to explode, not less.

Edit, I'm fairly sure the 1:25 needs changing to 1:2.5 btw.

[frogfot]

Well, it would probably ignite occasionaly, that still wouldn't affect yields much. Though there could maby settle a continious flame in methanole flask :eek:
How could chanses of explosion increase if we decrease methanole concentration (say, decrease it 10 times less than stochiometric). Reason I don't wanna use capillary is because I'm afraid to implode my recieving flasks (by water jet pump). I have only thin walled (measuring flasks), and capillary wouldn't be enough to eaven up vacuum, or?

In any case this oxidation operates with a level of methanol above the explosive limit

You mean, that stochiometric mix of methanole/air is unable to ignite in described conditions? I really hope that's true.

[megalomania]

Yes, the concentration of methanol is indeed supposed to be above the upper explosive limit in this reaction. That's why it is important to keep the water bath heating the methyl alcohol at exactly 46-47 degrees C, this keeps the evaporation rate of methyl alcohol just right.

That ratio of methyl alcohol to air was supposed to be 1 : 2.5 not 1 : 25, I edited it above to reflect that fact.

[frogfot]

Finally tested that synthesis, couple of minutes ago, luckily no autoignitions. I used setup nearly as on pic posted before (without H2SO4 washer). As combustion pipe I used 28 cm quartz pipe 8 mm (inner diameter). Copper coil was clutched together by plyers to fit inside pipe, total lengh of coil was 4 cm.
I had totally 100 ml MeOH and temperature in water-bath was always between 46,3 and 46,7 *C (temp control was provided by my experimental termostat circuit). After I heated coil, air was sucked through apparatus by water jet pump (suktion was regulated by a homemade clamp).
It was actually really easy to keep the coil glowing by its own. 2 cm was glowing steady. Closer to the end, glowing increased to 3 cm of coil, this was noticed when MeOH level was below air inlet pipe (air wasn't bubbling through MeOH). I think this increased oxygene concentration and reaction become more vigorous (autoignition was expected.. but there was none).

Here, IMO, one would have a clear indication that autoignition is coming: whole coil starts to glow. This overheating can be the only cause of autoignition. Basically, non-glowing part of coil will be as a safety heat-sink. Or?

Results:
Synthesis proceeded about 2 hours. In the end I had 64 ml liquid in first recieving flask and about 4 ml in second, no strong smell was detected. Both liquids was mixed and excess of 25% ammonia was added. I'll report how that will go after couple of hours in an edit...

Additionally, coil was examined after the experiment. It became much softer, and, 0,5 cm from one end was fused together! (end closest to MeOH fumes inlet) It was probably above 1000*C...

EDIT
Well, excess ammonia was destilled away and HMTA was dryed at 100*C. 16 g (+/-1 g) dry solid was ubtained.
Assuming HMTA formation is 100% (is it??), formaldehyde yield is 26-29%. Thats crappier than book claims primarily because there was some difficulties since this is first attempt, (had some troubles with crappy pipe connections) :P Next experiment will give better yield.

I also forgot to mention that pipes leading from second recieving flask to pump had small ammounts of white crystalline solid substance on walls. I dunno if that can be paraformaldehyde.. it didn't melt from lighter (though it gave a sharp smell)

[Hang-Man]

I admit, I didn't read the whole thread, but platinum is only mentioned once so I think I can post this without worry of overlap. I was doing some research on catalysts and discovered that platinum, a well known catalyst, has the wonderful property of converting methanol to formaldehyde. A thin wire suspended in methanol vapor will quickly glow red hot and oxidize the methyl alcohol to formaldehyde. (It is also used to convert ammonia to nitric acid)

[frogfot]

If I understood correctly, platina begins to glow without external heat provided in beginning?

Had a very nice idea for those who don`t have access to heat-resistent pipes. Using a thin walled iron pipe, one can indicate temperature with a homemade thermocouple (copper/iron) to see if catalyst is glowing. The copper wire is fused directly on iron pipe near catalyst, with help of a car battery (i found that copper wire must be thick enough to make a good fuse spot). On heating of fuse-spot with lighter, voltage across it got from 0,0mV to 1,5 mV
And ofcaurse I drawed a pic of what I mean:
http://www.geocities.com/frogfot/stuff/ironpipecat.png

As you can see iron pipe is slightly clutched to keep the catalyst coil in place, since in first experiment with quartz pipe it moved (cause coil become very soft)

Temperature that`ll affect thermocouple can be regulated by distance between fuse-spot and catalyst coil, this way one will avoid overheating of thermocouple.

If one worries about heat loss from catalyst, heat dissipation of iron is not that high. However, it would be adviseable to use long iron pipe (>50 cm) to avoid overheating of connection pipes.

I would test this thing if there was more time.. any idea if this will work?

[megalomania]

Do you happen to know of any calibrated voltage tables for iron-copper thermocouples available on the net? It would not do much good if people can't measure the temperature of the improvised thermocouple to begin with as the voltages would be meaningless.

[frogfot]

Nope, I don't have it. But, one don't have to know exact temperature. The important thing is to know that copper coil inside is "hot".
One can determine this value by experimenting. After heating/removing the gas burner from pipe without methanole/air flow, and, heating/removing burner from pipe with methanole/air flow. By comparing voltage changes, this way one can probably indicate when heat of pipe is maintained by catalyst..
Though that table would be sure very useful, I learned about what thermocouples was from Tuataras post in "Setting up a lab" thread. He mentioned several different compositions. (never thoat that temperature probes was so simple to make)

[Dave Angel]

I came across a product called Cool Glass in the garden centre the other day. It's a white powder that is moistened and painted onto greenhouses to... keep them cool. Turns out that it is titanium dioxide.

Apparantly this can be used as a photocatalyst in the oxidation of methanol to formaldehyde. I happen to have some pretty pure methanol lying around doing nothing so if I get a sunny day or some kind of decent light source I will do a few qualitative experiments. And maybe ethanol to acetaldehyde?

Also, the Japanese have tiles along the sides of some of their roads which contain or are coated with TiO2. This photocatalytically converts NOx pollution from exhausts and water vapour into nitric acid, which is then washed safely away when it rains. If I get round to doing some experiments in that area, I'll make sure to post them in the nitric acid section.

Imagine replacing the catalytic converter in your car with a TiO2 cat and UV bulbs, making nitric acid whilst you drive!

As for calibrating thermocouples, I think that fairly cheap (£30) IR thermometers can be bought these days and they go up to something like 500 degrees C.