Abstract: An improved process for the preparation of pyridines and/or hydrogened pyridines that have been substituted with a hydrocarbon group at one or more carbon atoms. .gamma.-cyanoketone, in a gaseous phase and in the presence of hydrogen, is passed over a first catalyst in a reaction zone to form a reaction mixture containing substituted pyridines and/or hydrogenated pyridines and hydrogen. A hydrogen-containing gas is separated from the reaction mixture and, prior to being recycled, is subjected to a two-step catalytic treatment. In the first catalytic treatment step, the hydrogen-containing gas is passed over an iron, nickel, cobalt, or platinum-containing catalyst at a temperature of between about 250.degree. and 550.degree. C. In the second catalytic treatment step, the hydrogen-containing gas is passed over an iron, nickel, or cobalt catalyst at a temperature of between about 550.degree. and 800.degree. C.

Abstract: An improved process for the preparation of pyridines and/or hydrogenated pyridines that have been substituted with a hydrocarbon group at one or more carbon atoms, .gamma.-cyanoketone, in a gaseous phase and in the presence of hydrogen, is passed in a reaction zone over a first catalyst containing a catalytically active metal or compound of a metal selected from the group copper, silver, gold, iron, nickel, cobalt, ruthenium, rhodium, palladium, osmium, iridium and platinum to form a reaction mixture. A hydrogen-containing gas is separated from the reaction mixture, passed over a second catalyst containing a catalytically active metal or compound of a metal selected from the group iron, nickel and cobalt at a temperature of between 300.degree. and 800.degree. C., and the hydrogen-containing gas so treated is recycled to the reaction zone.