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menchaca
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[*] posted on 14-3-2003 at 12:46
formaldehyde from methanol


i know that formahldehyde can be prepared by oxidysing methanol, would this reaction works?

CH3-OH + H2O2 + MNO2--->CH2=O + H2O + ........

Can you help me?

im not sure about how does manganese act in reaction
i know that MnO2+H2O2 poduces oxygen but i dont know the how does it work and i dont know either if this oxygen will be enough to oxydise methanol to formalhdehyde


Edited by Chemoleo: Corrected atrocious spelling in title and this post (it's about the worst I have seen)... people googling this very question won't ever find this thread because of terrible spelling! So yes, there is a point to keeping your spelling in check!!!

[Edited on 25-10-2004 by chemoleo]
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[*] posted on 14-3-2003 at 13:43


Erm...MnO2 is a catalyst for the decomposition of H-O-O-H, and H-O-O-H is also called a "meta"-stabile substance, it is thermodynamically unstable, but kinetically stable.

BTW, i think aqueous oxidizers won´t stop at the aldehyde-stage and generate huge amounts of carboxy acids as (by-)products.

Another possibility(quantitative :) ):

http://www.sciencemadness.org/library

[Edited on 14-3-2003 by BASF]




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[*] posted on 14-3-2003 at 13:50


I managed (quite by accident) to generate vast and unpleasant amounts of formaldehyde by oxidation of methanol with ammonium persulfate in hot aqueous solution.
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[*] posted on 14-3-2003 at 13:53


Some CH<sub>2</sub>O should bubble out; bubble that into water and you'll get aqueous formaldehyde solution.



I weep at the sight of flaming acetic anhydride.
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Organikum
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[*] posted on 16-3-2003 at 04:33
industrial


It is done in industry by the oxidative dehydrogenation of methanol. The process runs in a furnace tube at about 600°C to 700°C with a silverscreen as catalyst.

reaction is like this:



A newer process applies an catalyst consisting from 19% Fe2O3 and 81% MoO3 with Cr2O3/CoO as promotors. Temperatures are lowered to 350°C to 450°C and the process is run with large excess of oxygen/air.
In the older silver catalyst process the amount of air is critical to avoid overoxidation to formic acid or further.

What is this of interest for us?
A furnace tube, some silver catalyst (silverplated copper turnings are ok) at >500°C converts methanol to formaldehyde. The yields are not great, but as unconverted methanol can be feeded back and reused, who minds? By adjusting the air supplied right also good amounts of formic acid can be produced (together with formaldehyde).

I like the tube because no further reagents are needed and as I am more the chemical engineering geek....

there are some posts on furnace tubes on the board if interested.

ORG

[Edited on 16-6-2003 by Organikum]
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mad.gif posted on 16-3-2003 at 06:28


....and how are you planning to seperate formaldehyde from methanol-vapours to refeed the methanol ?

The two substances have very similar physical behaviour....




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[*] posted on 16-3-2003 at 13:03


It's nice you provide us with this information, but downscaling industry processes usually doesn't work out.

There's a reason why the industry goes from lab scale to batch scale and not the other way round.




One shouldn't accept or resort to the mutilation of science to appease the mentally impaired.
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[*] posted on 16-3-2003 at 13:28


Oh, but I think Organikum isn't just speculating here. I do believe he loves ye olde tube furnace and catalysts. There are a number of processes that you wouldn't necessarily think of as lab procedures - such as acetic anhydride synthesized from acetone pyrolysis - that nonetheless have been widely used, at least in the past, on a lab scale.

The dye chemistry book I'm scanning right now has yet another lab-scale tube furnace application: phthalic anhydride production, with electrostatic precipitation! This should provide some rainy day fun for a chemist once I have the book completed and online.

Of course in the old days people were willing to take more risks - often because they didn't know what risks they were taking. This dye book also contains syntheses for benzidine, alpha and beta napthylamine, and probably other nasties too. This is probably the first of my books that I'll attach safety warnings to, since the dangers are both potent and insidious.
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Organikum
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wink.gif posted on 17-3-2003 at 15:06
ehem...


thanks Polverone, also I would have loved to bite this leg my own. :D

Vulture, I hope you have the DJVU plugin already installed (www. lizardtech.com), if not you should do it now, it´s worth it.

The chemists before WWII have done it this way and not thought about industrial or not.
I cannot see what difference it makes for a methanol molecule if the catalyst and the heat are applied in a lab, at a industrial plant or your garage. I didn´t speak of hundreds of atmospheres pressure together with corrosive gases but of temperatures below 1000°C. My aunt, 74 years old makes pottery. Her oven is hotter.

With a little knowhow temperatures >2500°C can be reached quite easily with modificated microwaves from the scrapyard and a tuned waveduct/resonator for generating standing waves.

Back to the furnace tube. The tube was a standard laboratory device as the ketene lamp was also before chemists ordered everything from Sigma Aldrich but had the will, the ability and the need to make as much as possible from scratch.

They have actually been in the same situation we are today. So we should look back and learn from them.

The attached article is highly recommended for everybody who wants to dehydrogenate/oxidise alcohols and other compounds.

Sorry Vulture you got my nerv here, this sentence, written without any facts to back it up in this case got me real going.


other statements which "get me going":

- microwaves are dangerous, never put any metal in a microwave.....

- putting palladium, a inflammable solvent and hydrogen under pressure will cause an explosion!

- it is impossible to compress water!

... enough....

peace
ORG

PS: with the development of all these nice zeolithe and clay catalysts and the "Green Chemistry" much more "industry only" processes come in sudden reach. Or the possible substitution of crownethers by cyclodextrines......

Attachment: dehydes_by_tube.rar (58kB)
This file has been downloaded 1011 times

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[*] posted on 17-3-2003 at 15:23
BASF are you kidding?


or do you have anything against me?

Separation of formaldehyde and methanol by a so called "condensor" I would suppose, as:
bp formaldehyde: -19,5°C
bp methanol: 64,7°C
Quote:
The two substances have very similar physical behaviour....
not quite true BASF...

and:
Quote:
:mad:


whats up? don´t be as unfriendly, at least not when you are plain wrong.

ORG
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thumbup.gif posted on 17-3-2003 at 16:30
very good info.


Currently I am trying to build a tube furnace using more or less commonly found items and the file you attached is very helpful to me. The simplicity of the copper chromite catalyst is very interesting. Currently I am attempting to oxidize methanol to formaldehyde by producing a methanol/air mixture and running it through the tube furnace. I plan to use MoO2 which I have obtained by applying the fine black dust to fine steel wool. I have yet to try this catalyst design and am wondering what my chances of success will be. I am using a fish tank aerator for the air supply, which I measured has a flow rate of about 500ml/50sec. Some quick and rough calculations show that actually boiling the reservoir of methanol would provide an alcohol/air ratio that would be too high. Right now for a compromise I have extended the air input tube to the bottom of the alcohol reservoir so that the air bubbles through it, hopefully vaporizing a suitable amount of alcohol. Soon I should be aquiring some formaldehyde dosimeter tubes so I have a qualatative test other than using my nose. If I get some success, I'll try and get a digital cam to take some pics of the setup.
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[*] posted on 17-3-2003 at 17:16


@Organikum

sorry, nobody is perfect....it was a blackout

I did not think you might find this :mad: sign unfriendly......i use it, when i do it at all, to express heavy doubts.
But it seems everyone has its own interpretation of these tiny faces....

peace.

Back to the topic:

I still prefer making formaldehyde by decomposing calcium formate which is considerably cheap and high yielding.
Also, methanol is forbidden here in austria.-You need a special permission for buying poisons....arrrgh

The initially needed formic acid could eventually be made via NaOH + CO at 100°C, 0.8MPa or so, followed by freeing the formaldehyde with sulfuric acid, so not really beyond everyones possibilities!

The economy of the industrial dehydration of methanol may be better, but if you really think this process into d e t a i l you will soon realize your backyard would have to look like a refinery.

I mean blazters post above already shows some of the difficulties involved, so let´s not call this the easy way!

HLR


[Edited on 18-3-2003 by BASF]




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[*] posted on 18-3-2003 at 14:59


hey blazter, I guarantee you that it will work if you use same catalyst and apparatus as in the reference and run as slow as supposed. If you aim at more throughput you will need higher temperatures and a inert carrier gas like nitrogene or argon. The use of a more specialized catalyst is then preferable too, but how much formaldehyde do you need? The stuff is not healthy at least.

BASF, I didn´t want to say this is the only, not even this is the best way to do this. It was and is the best way for me and I like it as I regard this as true "Green Clandestine Chemistry" ;) , thats all.

Don´t you have model-airplanes and car/motorcycle racing with methanol as fuel? (ok icespeedway probably not.....)
just curious

peace
ORG
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[*] posted on 18-3-2003 at 15:41


Hey you won´t believe it but....you cannot buy methanol a n y w h e r e here -without this fu***g permission.

The same applies to many substances such as 37% formaline(although you can buy 20% solution without poison-permission), soluble heavy metal salts, ferrocyanides and the like....

Methanol from model/planes etc. is available here.......but it is not an option, since very expensive.

BTW, i am also some kind of chem engineering geek, at the moment playing with C-Control which is a programmable electronic device module, for a small automatic liquid phase reactor i´m planning.....hopefully this won´t take my whole life......arrrrrgh

So i have much understanding for this attempt of you ;).
The only thing i´m actually lacking is......time.

-and methanol, of course ;)

P.S. Do you have a digicam? -Photos would be great...

[Edited on 18-3-2003 by BASF]




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sad.gif posted on 18-3-2003 at 16:05
Not sure if I have access to all chems in the doc


Unfortuneatly, I'm not sure if I can get access to the chems required to produce the catalyst described in the doc. Not to mention the exotic glasswares. One thing that could be very useful to me is the bits of pumice. Anyone know where I might be able to obtain some? I really don't plan to produce much formaldehyde, and I am aware of the health risks of producing it. As my plans stand right now I hope to produce the formaldehyde more or less in situ, and just bubble it though a strong ammonia solution to hopefully produce hexamine. Later on I may attempt to produce form. solution to attempt the synthesis of pentaerythritol. One idea I did find to be enlightening was a patent on the process that showed an absorbtion tower arrangement for capturing the formaldehyde in H2O solution. However, I do wish to be able to produce a few grams of hexamine, hopefully that is not an unreasonable expectation.

P.S - BASF if you live in a cold climate you must be able to buy methanol as gas line antifreeze. Unless of couse the only kind they sell there is the IPA type.
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[*] posted on 22-3-2003 at 02:04


Blazter, pumice should be available at your sanitary supply house - it is used to rub the horny skin from the feet. :D
But there are sure other sources. The exotic glassware isn´t needed, what you need is a tube for heating and a condensor. Both don´t have to be made from glass - a metal tube and condensor are even preferable for the better heat conduction. The reaction tube can also be made horizontal with a slight degree upwards and heated by a burner. This makes temperature control more difficult but works of course too. But careful, as in this case your apparatus has to be absolute gastight - methanol is dangerous in gaseous state. So I would advise to use the heating wire from some old electroheater and furnace cement around a metal (copper) tube for heating.

I will take some pics the next time the apparatus is assembled, promised. This will be a setup for ethanol to acetaldehyde but I hope this doesn´t matter. ;)

But for hexamine? Why don´t you use solid camping fuel tabs (ESBIT)?

ORG
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[*] posted on 22-3-2003 at 09:56


scaling up a lab-sized catalytic reactor to a fullscale industrial reactor is mostly about controling the heat and massflows.

The chemistry involved doesnt change much, however sometimes the different flows can create different conditions masstransfer conditions. But, if a reaction works in full scale, it will most likely work on a labscale, given similar temperatures and massflows of reactants.

In a lab scale reactor, you usually have to apply heat since the surface/heat ratio is much larger than for a typical full scale reactor.

A big difference is that in a typical industrial setup streams are recirculated to increase yield, but this is not so easy to do in a typical lab-setup described as here. Thus you need some way of separating the products and reactants.

Formaldehyde is quite easy to strip from methanol solutions. Formaldehyde solutions usually contain 0,5 -2 % methanol to prevent paraformaldehyd forming.

Methanol is dangerous, however with good ventilation there is very little risk of accumulating explosive or poisonous gas mixtures.

Temperature control is absolutely crucial, to much and oxidation will go to completion, giving only CO2 and H2O.

Materials of construction: stainless steel is prefered before any other.

Instead of pumice, Al2O3 or SiO2 or any inert porous material can be used.

/rickard
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thumbup.gif posted on 22-3-2003 at 12:54


yeah as rikkitivitavi mentioned bevore, diatomeous earth could be used(SiO2).

Glowed diatomeous earth is chemically very resistant and is able to resist temperatures ranging from 1200-1700°C!!

It has been used as carrier in the ammonoxidation for HNO3, as far as i know.

HLR




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[*] posted on 22-3-2003 at 14:32


I wouldnt recommend using a carrier for the catalyst within 500 C of it s melting point, since the porous structure of the carrier will sinter slowly. This means that the efficency of the catalyst decreases by time. But in the formaldehyde production this is of no importance.

Comercial formaldehyde catalysts use ceramic rings with a melting point of about 1300 C, filled with catalyst.

HNO3 reactors uses a mesh of platinummetals, because short contact time is essential for good yield. A carrier based catalyst would not work well here.

Havinga large contact surface is the key to heterogenic catalysis.

Heterogenic catalysis is probably one of the hardest areas of chemical engineering to master.

/rickard
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[*] posted on 22-3-2003 at 14:32


I wouldnt recommend using a carrier for the catalyst within 500 C of it s melting point, since the porous structure of the carrier will sinter slowly. This means that the efficency of the catalyst decreases by time. But in the formaldehyde production this is of no importance.

Comercial formaldehyde catalysts use ceramic rings with a melting point of about 1300 C, filled with catalyst.

HNO3 reactors uses a mesh of platinummetals, because short contact time is essential for good yield. A carrier based catalyst would not work well here.

Havinga large contact surface is the key to heterogenic catalysis.

Heterogenic catalysis is probably one of the hardest areas of chemical engineering to master.

/rickard
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[*] posted on 25-3-2003 at 10:20
and if i oxide methanol to formic acid and lather i use Ca(OH)2?


the problem is how to reduce it with househol available chemicals i´ve thought in bleanch and an acid as hidrocloric acid the only problem i think this can have is chlorine gas with maybe desprended, is it so?
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[*] posted on 27-3-2003 at 18:05


rikkitikkitavi, the process described in the attached file is developed and optimized for laboratory use. So I recommend to follow the authors and to use coppertube. Also it is not right that the methanol is further oxidized in the process as it is no oxidation but a dehydrogenation. Further decomposition takes place thats right.
Instead of pumice Celite aka diatomeous earth/kieselguhr can be used but SiO2 is shit as it has not the necessary structure/surface area.

I beg anyone here to difference between the oxidative dehydrogenation and the the plain dehydrogenation processes. To mix the two up is very common but leads to bad yields in the best or accidents in the worst case.
The dehydrogenation without oxidation is to prefer as endothermic easy to control process. Unreacted methanol is feeded back so it is very easy to take the temperature up slowly until the reaction takes place (seen by the hydrogen evolving). As the wanted reaction comes as first one has to force things to ruin it. And even when done so nothing bad will happen. What do you expect more for heavens sake?

ORG

(next is the ketene-lamp, or better tube to come. We will have fun :D)
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[*] posted on 1-4-2003 at 11:19


can i oxide methanol to formic acid with NaClO and the make this react with Ca(OH)2 to form Ca(COO)2, and heat it to get CaCO3+CH2O?
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smile.gif posted on 1-4-2003 at 15:23
interesting news


Well after a few failed runs with my tube furnace project I think I may have had some success. The catalyst configuration that I used was some fine steel wool that i had "dabbed" on some of the MoO2 that I have. It was probably a couple inches long and fit inside the .5" galvanized steel pipe nipple. Anyways, I heated it up to around 290C, turned on the fishtank aerator to get the air flowing through it, and gently warmed up the methanol "boiler".

At the end of the tube there were some white fumes! Now the interesting part is that once the temp of the catalyst dropped down to around 230 the vapors stopped. I assume that the vapors were formaldhyde but really have no way to test it (I'm not about to huff the output).

Anybody care to speculate if what I got is a working setup here?
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[*] posted on 15-6-2003 at 22:19


No formaldehyde.
If it had been formaldehyde you would have smelled it immediately - no need to huff it - it comes to you.
You MUST vent the outlet of ANY tube through scrubbers! It is more than unhealthy and dangerous to let it open. Gases like formaldehyde are poisonous at roomtemperatur - if you get hit by formaldehyde with +100°C - I won´t imagine.
A tube needs: A flameback arrestor between boiler and tube and scrubbers after the tube. (A aspirator sucking at the end of the line is preferable)
There is no way to run a tube furnace without these simple, easy to make and zero-cost safety parts.
Without there will be not the slightest support at least by me. The games name is chemistry and not selfmutilation.
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