Applied Catalysis A: General 399 (2011) 211–220 Contents lists available at ScienceDirect Applied Catalysis A: General journal homepage: www.elsevier.com/locate/apcata Hydrodesulfurization catalyst bodies with various Co and Mo proﬁles John Vakros a , Christina Papadopoulou a , Alexis Lycourghiotis a , Christos Kordulis a,b,∗ a Department of Chemistry, University of Patras, GR-26500, Patras, Greece b Institute of Chemical Engineering and High Temperature Chemical Processes (FORTH/ICE-HT), GR-26500, Patras, Greece article info Article history: Received 17 January 2011 Received in revised form 22 March 2011 Accepted 3 April 2011 Available online 12 April 2011 Key words: CoMo/-Al2O3 catalysts HDS catalysts Proﬁles Macro-distribution Hydrodesulfurization DRS XRD TPR Effectiveness factor Hydrogenation Hydrotreatment Thiophene abstract We have achieved the preparation of ﬁve catalysts with various Co and Mo radial proﬁles in -Al 2 O 3 extrudates and loadings similar to the industrial hydrotreatment catalysts. EDS microanalysis was used for determining the proﬁles achieved. The catalyst bodies prepared were powdered and characterized using N 2 adsorption–desorption, temperature programmed reduction, X-ray powder diffraction, UV–vis diffuse reﬂectance spectroscopy and NO adsorption. The hydrodesulfurization of thiophene under atmo- spheric pressure was used as a probe reaction. The selectivity for the butane produced was taken as a measure of the hydrogenation ability of the catalysts. The different procedures inevitably used for the preparation of the different proﬁles affect somewhat the microscopic characteristics of the catalysts (Co and Mo dispersion, concentration of the coordinatively unsaturated sites, cobalt species formed) and to some extent their intrinsic catalytic behavior (determined in the powdered samples). The catalytic activity of the catalyst bodies depends on the aforementioned microscopic characteristics and the internal mass transfer resistance associated with the location of active phases and pores blocking. The combination of these factors becomes the sample with uniform Co and Mo proﬁles the most active one. DRS, TPR and XRD results indicated high Co dispersion in this sample. The hydrogenation ability of the CoMo/-Al 2 O 3 catalysts is higher over the catalyst bodies than over the powdered samples and enhanced on the catalysts with egg-shell Co proﬁles. © 2011 Elsevier B.V. All rights reserved. 1. Introduction The nowadays stringent legislation concerning automotive exhaust emission has reaccelerated research devoted to the preparation of more active hydrotreatment catalysts for destroy- ing sulfur-, nitrogen-, and metal-compounds in diesel fuels. For instance, new guidelines have been established by the US Environ- mental Protection Agency (EPA) that restrict the amount of sulfur allowed in diesel fuels to 1.3 × 10 -2 g/dl 3 by the year 2010 [1]. Achieving this limit requires major improvement or redesign of the catalysts employed for hydrodesulfurization (HDS) and related processes [2,3]. These catalysts usually consist of (Co/Ni)MoS 2 slabs supported on -Al 2 O 3 extrudates [4]. Improvement of these cat- alytic systems is based on new chemical formulations [5,6] and synthesis methods [7]. The relevant studies are usually focused on the increase of their intrinsic activity and thus most of them are performed on powdered catalysts. However, as these catalysts are employed in ﬁxed-bed reactors they are extruded into millimeter-sized catalyst bodies to mini- ∗ Corresponding author at: Department of Chemistry, University of Patras, GR- 26500, Patras, Greece. Tel.: +30 2610 997 125; fax: +30 2610 994 796. E-mail address: kordulis@upatras.gr (C. Kordulis). mize pressure drops across the reactor bed [8]. Thus, their efﬁciency depends on both; their intrinsic activity determined by the nature and dispersion of the active phases and the mass transfer limita- tions appearing upon the HDS processes. The latter are determined by the process conditions, catalyst body size and proﬁles of the active components in each catalyst extrudate [9]. Moreover, the performance (activity, selectivity, resistance to poisoning) of a sup- ported catalyst can be improved by achieving an appropriate proﬁle of the active phase within the support grain [9]. Theoretical and experimental studies reported so far may help achieving such a proﬁle in a particular system [10–51]. In this point it is important to stress the recent development of methodologies allowing the determination of proﬁles in terms of Co and Mo species instead of the elements proﬁles traditionally determined [35,38–47,49,50]. To our best knowledge, in spite of the above referenced very interesting studies there is not any systematic work concern- ing the preparation, characterization and catalytic evaluation of CoMo/Al 2 O 3 catalysts with all possible Co and Mo proﬁles having Co and Mo contents close to that industrially used. This is the goal of the present work. Based on the results reported in previous publications we attempted to prepare sam- ples with various Co and Mo radial proﬁles in -Al 2 O 3 extrudates. EDS microanalysis was used to investigate the type of the proﬁle achieved. Then all catalyst bodies were powdered and 0926-860X/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.apcata.2011.04.001