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Author: Subject: Paraformaldehyde from methanol
bmays
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[*] posted on 22-4-2016 at 17:36
Paraformaldehyde from methanol


I've been using this book as a ref.
http://library.sciencemadness.org/library/books/formaldehyde...

I've successful produced formaldehyde via oxidation of methanol in a 12 foot coil of 1/4" copper tubing glowing dull/cherry red probably about 600c. I don't think it was too hot, i ran with a faint red though and the production of white smokey gas remained almost constant. The air flow rate (slow bubbling) and methanol temperature seems to be important. My air was 5c (ambient) and methanol was about 50c

Anyway i ran about 150-200ml of methanol through this apparatus into 250ml of water cooled in an ice bath. I vacuum distilled, constantly stopping and checking for polymerization. I've let the last 5ml sit overnight and low and behold there is some paraformaldehyde. Still i was obviously expecting more.

Maybe a small amount of methanol is remaining and preventing polymerization could i use dcm to remove the methanol?. Maybe the air source must be hot, not just the methanol. Or possibly i must fit a water cooled condenser on the end before bubbling into 0c water. Maybe my coil is too hot or flow it too laminar within the tubing.

Any tips would be appreciated.

Edit: hopefully this section is for manufacture of reagents not just apparatus. Also my ac compressor pulls about 26" or 50c boiling water. Also, my methanol is wet, i don't see why the air or methanol would have to be dry though.

[Edited on 23-4-2016 by bmays]
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XeonTheMGPony
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[*] posted on 22-4-2016 at 20:03


to disrupt laminar flow you can partially flatten the copper to an oval shape, this increases the surface area for heat transfer and can help turbulize it by partial crimping alternating sides of the tubing.
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JJay
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[*] posted on 22-4-2016 at 20:31


You could get tremendously more surface area if you stuff a bigger tube with copper pot scratchers.
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XeonTheMGPony
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[*] posted on 22-4-2016 at 21:12


I was reading the article and yes better yet would be some copper screen, cut to disks and stack them then a bit of fiber glass befor hand to form a flash arrester!

I even dug out some fused quartz tubing I have and started to design a reactor.
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[*] posted on 22-4-2016 at 21:19


I just got some more nichrome, and this looks like an interesting project to try once I get another tube furnace built.
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nux vomica
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[*] posted on 23-4-2016 at 03:29


I get 28% to 32% formeldehyde useing a silver Catalyst on small soft firebrick pieces.
The methanol is heated to 55° and the airflow is 1.5 litres of air a minute .
You dont add water as it will dilute the solution too much as the equation ( 2 CH3OH + O2 → 2 CH2O + 2 H2O ) produces 2 H2O already.


20160423_204515-1200x2133.jpg - 300kB 20160423_204527-1200x2133.jpg - 330kB
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bmays
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[*] posted on 24-4-2016 at 16:05


Quote: Originally posted by nux vomica  
I get 28% to 32% formeldehyde useing a silver Catalyst on small soft firebrick pieces.
The methanol is heated to 55° and the airflow is 1.5 litres of air a minute .
You dont add water as it will dilute the solution too much as the equation ( 2 CH3OH + O2 → 2 CH2O + 2 H2O ) produces 2 H2O already.


Nice apparatus! Is the reaction self sustaining once hot? Maybe works for acetone as well.

I have a few rotameters from a gm camshaft lob measuring machine they junked many years ago. I might have to acquire some firebricks and fill my argon tank now.


[Edited on 25-4-2016 by bmays]
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nux vomica
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[*] posted on 24-4-2016 at 19:32


Once you have cacarfull heated the glass tube to start the catalyst up it is self sustaining until the methanol runs out.
You need o2 from a air compressor supplying air argon wont work.


20160425_131013-1200x2133.jpg - 292kB
Forgot to show the methanol heating setup, i use 2 meters of pvc tube coiled up to condence the product. Nux
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bmays
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[*] posted on 28-4-2016 at 11:09


Very nice. I use one of those controllers for a hotplate hot air bath. I was thinking of my argon welding gas, thinking out loud haha. If anyone else tries this note soft fire bricks are quite different then regular fire bricks.

Do you keep your tubing in a water bath to keep it cool or air cooled? I have a 1/2" x 18" copper water cooled condenser, due to the air stream i'm guessing a very long condenser like you used is required.
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