Production of amines by hydrogenation of nitrile compounds
View Patent ↗A method for producing amines by the hydrogenation of nitrile compounds in the presence of a catalyst, notably a method for producing diamines by the continuous hydrogenation of dinitrile compounds in the presence of a Raney-metal catalyst, includes controlling the molar flow of nitrile compounds and the mass flow of catalyst in a hydrogenation piston reactor in order to minimize the occurrence of impurities and deterioration of the catalyst.
1. A continuous process for the synthesis of compounds containing at least one amine functional group by hydrogenation of compounds containing at least one nitrile functional group, comprising:
feeding a gas which comprises hydrogen and a nitrile compound to a plug-flow reactor in which circulates a reaction medium comprising suspended particles of catalyst based on Raney metal, an inorganic base and water;
withdrawing, at the outlet of the plug-flow reactor, a portion of the reaction medium comprising the amine compound after separation of the catalyst and recycling the other portion to the plug-flow reactor;
recycling the separated catalyst to the plug-flow reactor;
feeding a stream of fresh catalyst to the plug-flow reactor;
and further wherein the flow rates for feeding nitrile compounds and/or catalyst to the plug-flow reactor are controlled as to maintain a ratio P of the number of moles of nitrile compounds fed per unit of time to the flow rate by weight of catalyst in the plug-flow reactor of from 0.02 to 0.15 mol of nitrile compounds per kg of catalyst for a catalyst exhibiting an initial activity of from 15×10 −5 to 35×10 −5 mol of H 2 /g of catalyst.
2. The continuous process as defined by claim 1 , wherein the reaction medium comprises a solvent.
3. The continuous process as defined by claim 2 , wherein the solvent comprises the amine produced by the hydrogenation reaction.
4. The continuous process as defined by claim 1 , wherein the nitrile compound is adiponitrile and the amine synthesized is hexamethylenediamine.
5. The continuous process as defined by claim 1 , whereat the outlet of the plug-flow reactor is a region for decantation of the catalyst particles, the supernatant phase being recycled to the plug-flow reactor via a first external loop comprising a withdrawal of the medium comprising the amine, the decanted phase being recycled to the plug-flow reactor via a second external loop.
6. The continuous process as defined by claim 5 , comprising withdrawing spent catalyst from the second external loop and feeding fresh catalyst at the inlet of the plug-flow reactor or to the second external loop.
7. The continuous process as defined by claim 6 , wherein the fresh catalyst comprises virgin catalyst, regenerated catalyst or mixture thereof.
8. The continuous process as defined by claim 5 , comprising a determination of the concentration of catalyst in the second external loop in order to calculate the total weight of catalyst in the plug-flow reactor.
9. The continuous process as defined by claim 1 , wherein the catalyst is based on Raney nickel or Raney cobalt.
10. The continuous process as defined by claim 9 , wherein the catalyst comprises a promoter selected from the elements of Groups IIB and IVB to VIIB of the Periodic Table of the Elements and combinations thereof.
11. The continuous process as defined by claim 1 , wherein the inorganic base is selected from the group consisting of LiOH, NaOH, KOH, RbOH, CsOH and mixture thereof.
12. The continuous process as defined by claim 11 , wherein the inorganic base is selected from the group consisting of KOH and NaOH and mixture thereof.
13. The continuous process as defined by claim 11 , wherein the amount of base in the reaction medium ranges from 0.1 mol of base per kg of catalyst to 2 mol of base per kg of catalyst.
14. The continuous process as defined by claim 1 , wherein the reaction temperature ranges from 50° C. to 150° C. and the hydrogen pressure ranges from 0.1 MPa to 10 MPa.