Applied Catalysis B: Environmental 107 (2011) 59–67 Contents lists available at ScienceDirect Applied Catalysis B: Environmental jo ur n al homepage: www.elsevier.com/locate/apcatb Effect of glycol on the formation of active species and sulfidation mechanism of CoMoP/Al 2 O 3 hydrotreating catalysts Thanh Son Nguyen a , Stéphane Loridant a , Lorentz Chantal a , Thierry Cholley b , Christophe Geantet a,∗ a Institut de Recherches sur la Catalyse et l’Environnement de Lyon (IRCELyon), UMR5256 CNRS – Université Lyon I, 2 avenue Albert Einstein, 69626 Villeurbanne cedex, France b Division Assistance Technique – Direction Technique – Total, BP 98-76700 Harfleur, France a r t i c l e i n f o Article history: Received 20 April 2011 Received in revised form 17 June 2011 Accepted 24 June 2011 Available online 30 June 2011 Keywords: Hydrotreating catalyst Sulphidation Additive TEG Raman spectroscopy QEXAFS 27Al NMR a b s t r a c t The present work is focused on the role of an organic promoter (triethyleneglycol – TEG) on the activity of hydrotreating catalysts. By impregnating such compound on oxidic industrial catalyst, an enhancement of the catalytic activity in the HDS conversion of 4,6-DMDBT as well as SRGO HDS was obtained. Using several physico-chemical techniques and in situ characterization (Raman, XAS), it was found that TEG affected the coordination of Co and Mo in the oxidic species. During the activation procedure, the presence of TEG slows down the sulfidation and allows the genesis of more active “CoMoS” species. © 2011 Elsevier B.V. All rights reserved. 1. Introduction In recent years, as legislation concerning the emission of sulfur- containing pollutants is becoming stricter, the HDS process has to be improved. One way to achieve this goal is to increase the activ- ity of CoMo and NiMo hydrodesulfurization (HDS) catalysts with new preparation routes or by adding doping agents. Several patents claimed the unusual effect of organic additives on the activity of hydrotreating catalysts [1–3]. Some of the organic compounds are almost infinitely water soluble and can be added during the incip- ient wetness impregnation of the active metals [2] or impregnated directly on the oxidic form of the catalyst in a second step [3]. In these patents, the organic additive is still present on the surface of the catalyst when the sulfidation starts. Despite the important number of industrial patents deposed in the last decade concerning the use of glycol-type additives in HDS catalysts, these additives are still a subject of current interest in the researches academic since no general agreement exists about the origin of the beneficial influence of these non chelating additives [4]. According to Nicosia and Prins [5,6], the catalyst impregnated with solution containing TEG showed a higher catalytic activity than the catalyst prepared without TEG. Raman and EXAFS spec- ∗ Corresponding author. E-mail address: Christophe.Geantet@ircelyon.univ-lyon1.fr (C. Geantet). troscopy demonstrated that the impregnation solution containing the metal salts and phosphoric acid contained HP 2 Mo 5 O 23 5- diphosphopentamolybdate and that this anion was not affected by the presence of TEG. 31 P NMR measurements of the impregna- tion solution showed a paramagnetic effect of cobalt, which proved that cobalt is complexed by the diphosphopentamolybdate, both in the presence and absence of TEG. Concerning the Mo species, by mean of UV–Vis and Mo X-ray absorption, they suggested the exis- tence of tetrahedral and octahedral coordination for molybdenum in presence of glycol. In the more recent study, Costa et al. [7] proposed the formation of PCoMo 11 O 40 7- species after additive impregnation in the case of CoMoP dried catalysts (P/Mo molar ratio ≥ 0.4) by mean of Raman spectroscopy characterization. Regarding the role of glycol-type additives on the sulfida- tion step, the academic literature showed controversial results. Nicosia and Prins [5,6] studied catalysts prepared from MoO 3 , H 3 PO 4 and CoCO 3 as reported in the literature [2]. EXAFS experiments showed that in presence of glycols, the sulfidation mechanism is modified and a faster sulfidation is observed. On the other hand, Mazoyer-Galliou et al. [8] have investigated the sulfidation of industrial calcined CoMo and CoMoP catalysts post- impregnated with diethyleneglycol monobutyl ether (DEGbe). They have shown, by elemental analysis on CoMo and DEGbe- impregnated CoMo/alumina catalysts, that the global sulfidation is delayed at temperature inferior to 473 K. In the same study, EXAFS 0926-3373/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.apcatb.2011.06.037