Applied Catalysis A: General 262 (2004) 111–120 Superficial characterization and hydroconversion of tetralin over NiW sulfide catalysts supported on zirconium doped mesoporous silica D. Eliche-Quesada, J. Mérida-Robles, P. Maireles-Torres, E. Rodr´ ıguez-Castellón, A. Jiménez-López ∗ Departamento de Qu´ ımica Inorgánica, Cristalograf´ ıa y Mineralog´ ıa (Unidad Asociada al Instituto de Catálisis y Petroleoqu´ ımica del CSIC), Facultad de Ciencias, Universidad de Málaga, Campus de Teatinos, 29071 Málaga, Spain Received in revised form 12 November 2003; accepted 14 November 2003 Abstract The influence of the W/Ni ratio and the phosphorous content as a promoter in the catalytic performance of NiW sulfide supported on zirconium containing mesoporous silica in the hydroconversion of tetralin has been studied. Three catalysts with a W loading of 20 wt.% and Ni loading of 2.5, 5 and 7.5 wt.% were prepared. To study the effect of phosphorous as promoter, prior to the metallic impregnation, 0.5, 1.5, 3.0 and 5.0 wt.% of P 2 O 5 was incorporated to the support. The catalysts were sulfided with a H 2 /H 2 S mixture at 400 ◦ C for 2 h, and finally tested in the hydrogenation (HYD)/ring-opening of tetralin at 6.0 MPa (4.5 MPa H 2 and 1.5 MPa N 2 ). Using IR and XP spectroscopies, a correlation has been established between the catalytic performance and the dispersion and type of compounds formed on the support. The formation of a highly dispersed NiWO 4 phase, easily sulfidable, and the high acidity of mild strength of the catalysts, could explain the good catalytic performance observed. The catalyst with 5 wt.% of Ni, 20 wt.% of W and 0.5 wt.% of P 2 O 5 shows an excellent catalytic performance and is higher than that observed with a sulfided commercial Ni-Mo/Al 2 O 3 , in the same experimental conditions. © 2003 Elsevier B.V. All rights reserved. Keywords: Hydroconversion; Sulfide catalysts; Tetralin 1. Introduction The term hydroprocessing includes a group of processes used in the petroleum refining industry. These processes are carried out owing to the ever increasing amounts of heavier feeds and the current trend in environmental regulations im- posed on the percentage of hetero-atoms as well as aromatic compounds allowed to be present in the different distillates. Hydroprocessing can be divided in two main groups [1]: (i) hydrotreating, focusing on eliminating hetero-atoms; (ii) hydroconversion, aimed at modifying the molecular weight and structure of organic feeds by hydrogenation (HYD), iso- merization, hydrocracking reactions, etc. These processes can convert heavy oils into fractions of high added value. However, the current demand for high quality diesel fuels is growing and, as a consequence, the environmental regula- tions of diesel emissions are more and more restrictive, and are intented to lower sulfur and aromatic content as well as ∗ Corresponding author. Tel.: +34-952131876; fax: +34-952137534. E-mail address: ajimenezl@uma.es (A. Jim´ enez-L´ opez). achieve a high cetane number. The aromatics in diesel fuels not only decrease the cetane number [2,3] but also produce undesired emissions in exhaust gases, such as carbonaceous particles with sizes ranging between 0.08 and 1 m with significant affects health. In order to hydrogenate the aromatic compounds and at the same time improve the cetane number of diesel fuels, the relatively new process of mild hydrocracking (MHC) is recommended. This process can be considered as inter- mediate between hydrotreating and hydrocracking [4] and is performed by employing hydrogen pressures lower than those for hydrocracking but working at temperatures slightly higher than those for hydrotreating. Although this process produces low sulfur contents in the fuels obtained, the hy- drogenation of aromatic molecules takes place only to a poor extent, due in particular to the low pressures of hydro- gen used. Even using severe operating conditions the diesel products obtained with a single stage-reactor do not comply with the stringent specifications [5]. Conventional sulfide catalysts, such as NiMo and NiW, which are active in hydrodesulfuration (HDS) and 0926-860X/$ – see front matter © 2003 Elsevier B.V. All rights reserved. doi:10.1016/j.apcata.2003.11.015