Catalytic hydrogenation of Nitromethane.

anime · Sun Jul 17, 2005 11:23 pm

Look at Rhodium archives, there are two reductions of nitromethane, both performed by KrZ.

"
* 2500g CH3NO2
* 3000g CH3OH
* 20g Pd/C 5%

They were stirred and hydrogenated at 80psi, after 24 hours the heat subsided, and at 48 hours H2 uptake had long since ceased and the reaction was shut down. On depressurization, the ammonia-like odor was definitely evident. The catalyst was vacuum filtered off and collected, and the remainder still had a definite charcoal look to it. Filtering this through celite took care of most of that. The mix was split in half and each half sat with 1500g of Na2SO4 for an hour, with occasional stirring. The Na2SO4 was filtered off for a long time, until it was quite dry in appearance, the halves were combined and washed 2x with 1L of CH3OH, which was filtered off and added back to the solution. What was left was about ~7.5L of good loving. When 1L of this was converted to the HCl salt, 250g of salt was collected."

swim has a few questions.
1.) has anyone tried this proceedure,

2.) how hot does it run. Swim reduced nitromethane with zn/formic acid, the reaction was very exothermic.

3.) on the drying of the methanol, can it be properly dried by the Na2SO4 as posted in this method?

4.) if the methanol is not anhydrous, would predrying it with Na2SO4 sufficiently dry it?
thanks,
amine.

java · Consumer

There is a thread called question about methylamine by myself that was at the Hive where many posted and gave their advice, I hope it's of some help in SWIM's quest............java

https://www.synthetikal.com/arch/forum/topic/topic_129.html

KrZ · Mon Jul 18, 2005 5:14 pm

1) has anyone tried this proceedure

Yes. It's quite straightforward.

2) how hot does it run. Swim reduced nitromethane with zn/formic acid, the reaction was very exothermic.

It gets quite hot, the reactor shell generally reaches ~70C. However, using a small amount of catalyst makes it quite manageable, the reaction will proceed for quite some time at elevated temperature, but I would in no way describe it as violent.

3) on the drying of the methanol, can it be properly dried by the Na2SO4 as posted in this method?

Later it was discovered that Calcium Oxide seems to work a bit better. Na2SO4 seemed to reduce the yields several percent, maybe 10-15%, and the filtered and washed Na2SO4 had a noticeable methylamine smell to it. That could always be handled by heating the Na2SO4 and bubbling the released Metheylamine gas into methanol.

4) if the methanol is not anhydrous, would predrying it with Na2SO4 sufficiently dry it?

The drying is performed after the reaction because CH3NO2 + 3H2 -> CH3NH3 + 3H2O, you're generating significant quantites of water in the course of the reaction. One could always isolate the HCl salt of methylamine from the reaction mixture as an alternative to drying. That would also be an alternative to the titration one would normally perform to determine the yield.

anime · Tue Jul 19, 2005 1:54 am

KrZ, do you recommend cooling the reaction?. Also how much catalyst should be used when running a 500-100g batch of nitromethane? Scale accordingly?

java · Consumer

Well until KrZ responds , I will give you my unsolicited opinion based on many years use of the hydrogenator apparatus in my research...............

I would try 3/4-1 gr of Pd 10%/C in 100gr. of nitromathane and 4gr in the 500 load , and watch the hydrogen gauge see it's taking the Hydrogen......if it gets too hot just turn off the Hydrogen and allow to cool then proceed,......that's what I would do or get a cooling jacket for your hydrogenator bottle and buy the thermocuple to put inside the bottle to gauge your temp, this can be purchased from the manufacturer, this way you can see the temp and add more ice to your recirculating pump to cool your bottle to maintain a safe temp.............java