Synthesis of methylamine hcl from formaldehyde (large scale)

[William D.]

1. 10 kg of 40% formaldehyde and 5 kg of ammonium chloride were mixed in a reactor with a distillation head.
2. The mixture was stirred with gradual heating, distilling primary products at 50 *C.
3. When the distillate stopped and removed the mixture was heated to 110 *C.
4. Heating the mixture was continued for 6 hours under stirring.
5. The vacuum was pumped into the reactor and the water was distilled as much as possible.
6. It was added 10 liters of n-butyl alcohol, heated to 100 *C and stirred until the precipitate decreased.
7. The mixture was filtered through a nutsche-filter to separate from an insoluble precipitate (ammonium chloride) and the alcohol solution was returned to the reactor.
8. The alcohol was as distilled as possible under vacuum, the obtained crystals were dried about vacuum and packaged in vacuum packaging in order to avoid hydration. Yield: ~3 kg.

 

[Power]

Thanks for this

 

[mithyl2]

what is the best way to purify the end product with this method?

 

[Ortist]

wash with chloroform or boil it in a dichloromethane to get rid of dimethylamine.

 

[CryoThio]

Any alternative for n butyl alcohol?

 

[Ortist]

They rely on a very low solubility of ammonium chloride in butyl alcohol. The reaction after step 4 will contain a huge amount of ammonium chloride.

You can cool it down after step 4, precipitate unreacted ammonium chloride, filter it out, then reduce liquid volume twice by gentle boiling, then cool down again, precepitate more ammonium chloride.

After that continue with step 5 but instead of n-butyl you can use ethanol or even isopropanol.

This write up doesn't mention that filtrations of alcohol must be done while hot and this is very tricky as methylamine will crystalize in a filter.

This reaction can be done at 98 degrees which reults in less dimethylamine. I add isopropyl alcohol to the RM in this case to get rid of formic acid which is produced and srays in the RM (at 98 degrees no much decomposition of formic acid)

 

[hunter12]

Can i increase the temperature above 110 C when distilling off the water after reaction(step 4). Or i should still distill off the water at 110C on step 5