Pyridine hydrodenitrogenation: An equilibrium limitation on the formation of piperidine intermediate

Equilibration between pyridine and piperidine, the first product formed in the overall series of hydrodenitrogenation (HDN) reactions of pyridine, can be a rate‐limiting factor under some conditions. Thus, on a commercial NiMo/Al 2 O 3 catalyst at 11 bars pressure, a maximum in the pyridine HDN rate occurs at about 400°C, caused by a thermodynamic limitation on the allowable concentration of piperidine. From studies with pyridine and with piperidine, NiMo/Al 2 O 3 appears to have greater hydrogenation‐dehydrogenation activity than CoMo/Al 2 O 3 but CoMo/Al 2 O 3 appears to have greater hydrogenolysis activity than NiMo/Al 2 O 3 , at least at about 300°C and below.