Effect of catalyst surface on decomposition of nitrogen heterorings during regeneration of hydroprocessing catalysts

Commercial CoMo/Al2O3 and NiMo/Al2O3 catalysts and gamma-Al2O3 were deposited with pyrrole, pyridine and quinoline. The deposits were decomposed during the temperature-programmed experiments (from room temperature to 1000 degrees C) in the gas mixture containing between 0 and 4 vol% O-2. For both catalysts (oxidic and sulfided), patterns in the formation of NH3 and HCN indicate on participation of the Bronstedt acid sites during decomposition of the deposits contrary to a little involvement of these sites on gamma-Al2O3. The pyrrole deposits were more reactive than pyridine and quinoline deposits. Also, the mechanism of decomposition of the latter differed from that of pyrrole, especially on gamma-Al2O3. (C) 1998 Elsevier Science B.V. All rights reserved.