Hydrocracking of phenanthrene over bifunctional Pt catalysts

Hydrocracking of phenanthrene was studied in a fixed bed continuous flow re actor under 60 bar total pressure using a bifunctional catalyst constituted of Pt deposited on silica-alumina. GC-MS analysis was utilised in order to identify the numerous products formed during phenanthrene hydrocracking. F ollowing a kinetic study, a reaction pathway was proposed based on a multi- step mechanism: hydrogenation of aromatic rings, isomerisation and cracking of naphtenic rings, and rearrangements. Reaction temperature showed a grea t effect in terms of selectivity and catalysts comparison was therefore don e at a temperature of 300 degreesC. Three bifunctional catalysts: platinum supported on silica-alumina, on H-Y zeolite and on H-beta zeolite were comp ared in terms of activity and selectivity A close examination of product di stribution indicated that the major contributing factor was the pore struct ure of the support. Zeolite structures favoured overcracking because of the numerous collisions with acid sites that perhydrophenanthrene could underg o during its diffusion. (C) 2001 Elsevier Science B.V. All rights reserved.