A series of carbide and sulfide catalysts comprising NbMo2C, Mo2C, NbC and MoS2/SiO2 was used to study the pyridine hydrodenitrogenation (HDN) network below at high pressure (3.1 MPa) as a function of temperature. pyridine-->(k1)piperidine-->(k2)n-pentylamine-->(k3)hydrocarbons All the catalysts showed the same trend in activities for the three molecules: the reactivity of n-pentylamine was high, while those of piperidine and pyridine were relatively low, especially at low temperatures. The carbide catalysts showed higher selectivity towards HDN products than the sulfide catalyst at the same conversion levels. The higher selectivity was related to the higher ratio (r = k(2)/k(1)) between the rate constants of the two consecutive reactions, hydrogenation of pyridine (k(1)) and ring opening of piperidine (k(2)) The order of activity of the carbides and sulfide differed considerably depending on the substrate. At the same temperature, the sulfide was more active for pyridine HDN when compared to the carbide catalysts, but it was much less active for quinoline HDN, suggesting that the HDN reaction mechanism depends greatly on the structure of the N-containing molecule. However, for the pyridine reaction network the similarity in product distribution suggested that the active surface of the carbides and sulfide was similar at reaction conditions.