Hydrogenation of naphthalene on NiMo- Ni- and Ru/Al 2 O 3 catalysts: Langmuir–Hinshelwood kinetic modelling Ana Cristina Alves Monteiro-Gezork a, * , Reyna Natividad b , John Mike Winterbottom a a Department of Chemical Engineering, School of Engineering, The University of Birmingham, Birmingham B15 2TT, United Kingdom b Department of Chemical Engineering, Faculty of Chemistry, Universidad Auto ´noma del Estado de Me ´xico, Paseo Colo ´n Esq. Tollocan, Toluca, Edo. de Me ´xico, Me ´xico CP 50120, Mexico Abstract 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 (Al 2 O 3 ) 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/Al 2 O 3 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/Al 2 O 3 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/Al 2 O 3 or the presulphided NiMo/Al 2 O 3 catalyst. # 2007 Elsevier B.V. All rights reserved. Keywords: Naphthalene hydrogenation; Kinetic modelling; NiMo/Al 2 O 3 ; Ni/Al 2 O 3 ; Ru/Al 2 O 3 1. Introduction Hydrotreatment is an important group of processes in the petroleum refining industry for (1) the protection of the catalysts used in latter stages of the refining process, (2) the abatement of NO x and SO 2 emissions that could arise from the combustion of organic molecules, (3) the improvement of the properties of the final products issued from refining (such as colour, smell and stability) and (4) the valorisation of heavy stocks. It is an extensively documented process and several reviews have been devoted to it during the last decades [1–5]. Due to the required use of new feedstocks and application of more severe environmental legislation [6], the interest on this subject is constantly renewed. During the hydrotreating process, the HYD of the aromatic rings prior to sulphur removal is considered to alleviate the steric hindrance of substituted dibenzothiophenes, considered the most unreactive towards hydrodesulphurisation (HDS), and therefore facilitate HDS reaction [5,7]. Moreover, nitrogen removal from polycyclic aromatics does not take place until ring saturation has occurred. A high aromatic content is associated with poor fuel quality, giving a low cetane number in diesel fuel and a high smoke point in jet fuel [8,9]. Consequently, from the viewpoint of environmental conservation, aromatics saturation is the key reaction to reduce NO x and particulate matter [10] in order to provide environmentally more acceptable reformulated fuels. Aromatic HYD in industrial feedstocks may be carried out over supported metal or metal sulphided catalysts. NiMo catalyst is a typical hydrotreating catalyst that is commonly used in industry to catalyse primarily HDA and secondly HDS reactions, whether in a single stage process or in the first stage of a two-stage process. In a two-stage process, the HDA is usually achieved in the second stage with Ni or noble metal catalysts [11]. Presulphided NiMo catalysts are reported to be resistant to sulphur and coke deposition, whereas supported Ni or noble metal catalysts should be used in a sulphur-free www.elsevier.com/locate/cattod Available online at www.sciencedirect.com Catalysis Today 130 (2008) 471–485 * Corresponding author. Present address: Stu ¨hlinger Straße 17, 79106 Freiburg, Germany. E-mail address: acm848@yahoo.com (A.C.A. Monteiro-Gezork). 0920-5861/$ – see front matter # 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.cattod.2007.10.102