Synthesis, characterization and cyclohexene hydrogenation activity of high surface area molybdenum disulfide catalysts M. Soto-Puente, a M. Del Valle, a Eric Flores-Aquino, b M. Avalos-Borja, b S. Fuentes, b and J. Cruz-Reyes a, * a Facultad de Ciencias Quı´micas e Ingenierı´a, Universidad Auto ´noma de Baja California, Tijuana, BC, Mexico b Centro de Ciencias de la Materia Condensada, Universidad Nacional Auto ´noma de Me ´xico, Ensenada, BC, Mexico Received 5 November 2006; accepted 21 December 2006 An ammonium tetrathiomolybdate (ATTM) catalyst precursor is synthesized and then thermally decomposed at different temperatures in N 2 or H 2 atmosphere. Characterization of the resulting compounds by powder X-ray diffraction (XRD) and surface area analysis indicates the formation of MoS 2 –2H with a surface area of 5–9 m 2 /g. When ATTM is treated with cetyltrimethylammonium chloride and then decomposed in N 2 at 723 K, the resulting material has a surface area nearing 200 m 2 /g. If treatment also includes hydrazine, the surface area of the resulting MoS 2 –2H reaches 215 m 2 /g. Analysis by XRD and electron microscopy shows a noticeable dispersion in the layers of the resulting MoS 2 . The catalytic activity of the materials is tested in a batch reactor for cyclohexene hydrogenation, where the highest activity sulfides are those obtained by thermal decomposition of the chemically treated precursors in N 2 . KEY WORDS: high surface area MoS 2 ; hydrogenation; cyclohexene. 1. Introduction The field of solid state chemistry has produced numerous studies on the optical, electrical, electro- chemical and catalytic properties of transition metal sulfides (TMS). In general, TMS with layered structures exhibit similar catalytic behavior in hydrotreating reac- tions [1]. While some preparation methods yield highly crystalline, low surface area compounds [2,3], others lead to materials with poor crystallinity and greater surface area, along with appreciable catalytic activity. Such methods include co-maceration [4], precipitation [5, 6], and thiosalt decomposition [7]. In the search for new catalysts, some in situ methods have been developed which yield high surface area sulfides. The introduction of alkyl ammonium thiometallate precursors, for example, has produced compounds with greater surface areas than earlier generations of sulfide catalysts [8,9]. The synthesis of MoS 2 by a hydrothermal route also leads to the formation of a highly dispersed compound. Thus, the decomposition of ATTM in water under 20 bar N 2 or H 2 S atmosphere has been studied at 15 min intervals for up to 4 h and at different temper- atures in the region of 473–573 K, yielding catalysts with areas between 50 and 95 m 2 /g [10]. Increasing attention has been paid to the role of carbon in the stability of MoS 2 and RuS 2 catalysts, with some studies suggesting that the active phase of these compounds involves a high surface area MoS 2- x C x compound. The first claims of the importance of carbon in these catalysts are made with regard to the synthesis of RuS 2-x C x compounds, where carbon atoms substituting surface sulfur atoms were detected [8,9]. Catalysts obtained from carbon-containing salts of the type (NR 4 ) 2 MoS 4 (where R= alkyl group) have greater catalytic activities than those obtained from the ammonium thiomolybdate salt [8,11–13]. Studies also indicate a noticeable increase in the surface area of the catalyst obtained from carbon-containing ammonium thiosalts, like in the case of MoS 2-x C x which has a surface area of 152 m 2 /g when prepared from an ethylene-diamine thiosalt, and a surface area of 243 m 2 /g when prepared from a tetrabutyl ammo- nium salt [12,14]. Prior synthesis of this type of catalyst has been done in situ by decomposing ATTM in a reactor containing sulfur and H 2 [10]. In a recent study, in situ catalysts are found to yield greater surface areas than those prepared by conventional ex situ thiosalt decomposition, where the thiosalt is treated with a mixture of H 2 S/H 2 at 673 K for 4 h [15]. A recent proposal takes aqueous solutions of ATTM, then adds reducing agents such as hydrazine (HZN) or hydroxylamine and in some cases a surfactant agent like cetyl-trimethylammonium chloride (CTAC), to produce molybdenum sulfides with surface area as high as 211 m 2 /g [16]. In this work, the effect of using non-stoichiometric quantity of CTAC and/or HZN to treat ATTM *To whom correspondence should be addressed. E-mail: juancruz@uabc.mx Catalysis Letters, Vol. 113, Nos. 3–4, February 2007 (Ó 2007) 170 DOI: 10.1007/s10562-007-9030-z 1011-372X/07/0200–0170/0 Ó 2007 Springer Science+Business Media, LLC