Potential role of water and catalyst surface in pyrolysis of nitrogen-rings during catalyst regeneration

The evolution of H2O during temperature programmed pyrolysis (TPP) of pyridine and pyrrole deposited NiMo and CoMo catalysts and gamma-Al2O3 was investigated between room temperature and 1000 degrees C. gamma-Al2O3 influenced TPP of pyrrole but had little effect on that of pyridine. The oxidic and sulfided NiMo and CoMo catalysts influenced the TPP of both pyridine and pyrrole. This was supported by increased yields of H2O for the deposited catalysts compared to the undeposited catalysts. The mechanism of H2O formation involving one OH group, SH groups and ring hydrogens is proposed. The difference between the mechanisms of the TPP of pyrrole and pyridine, including a potential role of Bronsted acidic sites during the TPP of the latter, is discussed. (C) 2000 Elsevier Science B.V. All rights reserved.