Preparation of methylpentamethylenediamine and methylpiperidine
Methyl-2-pentamethylenediamine and methyl-3-piperidine are prepared by hydrogenation of methylglutaronitrile in the presence of a catalyst including cobalt, chromium, and nickel, especially a catalyst based on Raney cobalt doped with nickel and chromium.
1. A process for the preparation of 2-methylpentamethylenediamine and 3-methylpiperidine, comprising hydrogenating methylglutaronitrile in the presence of a catalyst which comprises cobalt doped with nickel and chromium, under an absolute hydrogen pressure of less than 50 bar.
2. The process as defined by claim 1 , wherein the hydrogenation reaction is carried out under an absolute hydrogen pressure ranging from 10 to 35 bar.
3. The process as defined by claim 1 , wherein the hydrogenation is carried out in the presence of a solvent selected from the group consisting of alcohols, water or mixture thereof.
4. The process as defined by claim 1 , wherein the hydrogenation is carried out in the presence of a strong basic inorganic compound selected from the group consisting of alkali metal hydroxides and ammonium hydroxide.
5. The process as defined by claim 1 , wherein the hydrogenation is carried out at a temperature ranging from 60 to 160° C.
6. The process as defined by claim 1 , wherein the percentage by weight of cobalt in the catalyst, expressed as Co, ranges from 85% to 98%, with respect to the weight of catalyst.
7. The process as defined by claim 1 , wherein the percentage by weight of nickel in the catalyst, expressed as Ni, ranges from 0.1% to 4%, with respect to the weight of catalyst.
8. The process as defined by claim 1 , wherein the percentage by weight of chromium in the catalyst, expressed as Cr, ranges from 0.1% to 4%, with respect to the weight of catalyst.
9. The process as defined by claim 1 , wherein the cobalt present in the catalyst comprises a Raney cobalt.
10. A process for the synthesis of β-picoline, comprising dehydrogenating the mixture of 2-methylpentamethylenediamine and 3-methylpiperidine prepared according to the process as defined in claim 1 .
11. A process for the preparation of 2-methylpentamethylenediamine and 3-methylpiperidine, comprising hydrogenating a mixture of dinitriles comprising methylglutaronitrile, ethylsuccinonitrile and adiponitrile, in the presence of a catalyst which comprises cobalt doped with nickel and chromium, under an absolute hydrogen pressure of less than 50 bar.
12. The process as defined by claim 11 , wherein the mixture of dinitriles has the following composition by weight:
Methylglutaronitrile ranging from 70% to 95%
Ethylsuccinonitrile ranging from 5% to 30%
Adiponitrile ranging from 0% to 10%.
13. The process as defined by claim 11 , wherein the mixture of dinitriles is enriched in methylglutaronitrile prior to the hydrogenation stage.