GB755534A - Catalytic cyclisation of pentamethylene diamine - Google Patents

Abstract

Piperidine is manufactured by a process comprising contacting pentamethylene diamine in the vapour state at elevated temperature with an acid heterogeneous catalyst of the type used for promoting alkylation of aromatic compounds. To prevent the formation of by-products an inert gas such as nitrogen or hydrogen may be passed through the reaction zone. If desired, the piperidine may be converted into pyridine by catalytic dehydrogenation almost simultaneously with the cyclization by mixing a dehydrogenation catalyst such as a platinum or palladium catalyst with the cyclisation catalyst and using hydrogen as the inert gas. Suitable catalysts for the cyclization reaction are, for example, silica gel, alumina-silica beads and boron phosphate. In the examples: (a) pentamethylene diamine is mixed with nitrogen and passed over (i) silica gel; and (ii) aluminasilica beads to give piperidine; and (b) pentamethylene diamine is mixed with hydrogen and passed over a catalyst consisting of platinum deposited on silica gel to give pyridine.