Manufacturing Process
The catalyst is prepared by suspending 5 kg of catalyst grade charcoal in 200
liters of water, in a pressure vessel, and adding thereto 25 liters of 4% (as Pd
metal) aqueous palladous chloride. Air is displaced from the vessel and then
hydrogen is passed into the aqueous mixture at a pressure of 3 to 5 psi, while
stirring, until no further absorption is noted and the chloride is completely
reduced to metal.
To the aqueous suspension of the palladized charcoal catalyst thus obtained
are added 20.8 kg of 3-cyano-pyridine (96% purity); and then are added 70 liters of a hydrochloric acid solution prepared by diluting 30 liters of 36% HCl
with 40 liters of water. This represents approximately 1.75 mols of HCl for
each mol of 3-cyano-pyridine. The suspension is maintained at 10° to 15°C
and stirred continuously while introducing a current of hydrogen at a pressure
of 3 to 5 psi. When absorption of hydrogen ceases and the 3-cyanopyridine is
completely reduced, the reaction mixture is filtered to remove the catalyst.
The filter cake is washed with 40 liters of water in two equal portions, and the
wash water is added to the filtrate.
The combined liquors, which comprise an aqueous hydrochloric acid solution
of 3-aminomethyl-pyridine hydrochloride, are then heated to a temperature of
60° to 65°C, and ethyl nitrite gas is passed into the heated solution. The ethyl
nitrite is generated by placing 20 liters of 90% ethyl alcohol in a suitable
vessel, diluting with 200 liters of water, and, while stirring, adding to the
dilute alcohol 18.3 kg of nitrosyl chloride at the rate of 2.25 kg per hour. (The
process using methyl nitrite is carried out by substituting a stoichiometrically
equivalent quantity of methyl alcohol for the ethyl alcohol.)
When all the ethyl nitrite has been added, the reaction mixture is refluxed for
approximately one hour, then concentrated to dryness under reduced pressure
(25 to 30 mm Hg) and at a maximum temperature of 70°C. The crystalline
residue is dissolved in 35 liters of water and adjusted to a pH of 8 to 9 by
addition (with cooling and stirring) of 11 to 12 kg of caustic soda. The sodium
chloride formed is filtered off, and the filter cake is washed with 20 liters of
normal butyl alcohol. This wash liquid is used for the first extraction of the
product from the aqueous filtrate. The filtrate is then further extracted with
four successive 20-liter portions of n-butyl alcohol.
All the extracts are combined and concentrated in vacuo (100°C/20 mm) to
remove the n-butyl alcohol. The residue is submitted to fractionation under
reduced pressure. The forerun (up to 112°C/2 to 3 mm) consists of a small
amount of n-butyl alcohol and some 3-pyridylcarbinol. The main fraction,
boiling at 112° to 114°C/2 to 3 mm, consists of 3-pyridylcarbinol.
