Catalysts for the preparation of methylpyridine

#Subject of the invention is a dehydrogenation catalyst for dehydrogenating methylpiperidine to methylpyridine. Subject of the invention are also methods for preparing the catalysts and methods, in which the catalysts are used.

#3-methylpiperidine and 3-methylpyridine (3-picoline) are intermediates in the industrial production of nicotinic amide and nicotinic acid, which is an essential vitamin of the B-complex (vitamin B3). In this process, 3-methylpiperidine is converted to 3-methylpyridine in the presence of a dehydrogenation catalyst. The 3-methylpyridine is converted to 3-cyanopyridine by oxidative ammonolysis. The 3-methylpiperidine can be obtained by cyclization of 2-methyl-1,5-diaminopentane.

#Catalysts function to increase the rate of a chemical reaction at a given temperature by lowering the necessary amount of energy to reach the transition state. They can be present in the same phase as the reaction educts (homogenous catalysts) or in a different phase (heterogeneous catalysts).

#Subject of the invention is a process for the production of a catalyst for the dehydrogenation of methylpiperidine to methylpyridine, comprising in the order (a) to (d) the steps of (a) providing a carrier comprising 65-100 weight % silicon oxide and 0-35 weight % aluminium oxide, (b) impregnating the carrier with palladium, whereby the carrier is brought into contact with an aqueous solution of a palladium-ammonia-complex to obtain a catalyst, (c) drying the catalyst at a temperature below 80° C. and (d) calcinating the catalyst at a temperature below 200° C.

#In a specific embodiment of the invention, the steps (a) to (d) are carried out in one single reactor.

#In a preferred embodiment of the invention, the drying step (c) is carried out with air and/or at a temperature between 20° C. and 60° C., preferably between 25° C. and 50° C. or between 30° C. and 45° C. In a preferred embodiment, the drying step is carried out at 40° C. Preferably, the drying step is carried out under air. The drying step is finished when essentially all the water is removed from the catalyst. In an embodiment of the invention, the drying step is carried out for 5 hours to 7 days, preferably for 1 to 5 days.