Hydrogenation of naphthalene on NiMo- Ni- and Ru/Al2O3 catalysts:: Langmuir-Hinshelwood kinetic modelling

The importance of the hydrodearomatisation (HDA) is increasing together with tightening legislation of fuel quality and exhaust emissions. The present study focuses on hydrogenation (HYD) kinetics of the model aromatic compound naphthalene, found in typical diesel fraction, in n-hexadecane over a NiMo (nickel molybdenum), Ni (nickel) and Ru (ruthenium) supported on trilobe alumina (Al2O3) catalysts. Kinetic reaction expressions based on the mechanistic Langmuir-Hinshelwood (L-H) model were derived and tested by regressing the experimental data that translated the effect of both naphthalene and hydrogen concentration at a constant temperature (523.15 and 573.15 K over the NiMo catalyst and at 373.15 K over the Ni and Ru/Al2O3 catalysts) on the initial reaction rate. The L-H equation, giving an adequate fit to the experimental data with physically meaningful parameters, suggested a competitive adsorption between hydrogen and naphthalene over the presulphided NiMo catalyst and a non-competitive adsorption between these two reactants over the prereduced Ni and Ru/Al2O3 catalysts. In addition, the adsorption constant values indicated that the prereduced Ru catalyst was a much more active catalyst towards naphthalene HYD than the prereduced Ni/Al2O3 or the presulphided NiMo/Al2O3 catalyst. (C) 2007 Elsevier B.V. All rights reserved.