Nanometric bimetallic sulfides prepared via thermal decomposition of Ni and Fe heteropolymolybdate emulsions
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Catalysis Letters Vol. 112, Nos. 3–4, December 2006 (Ó 2006) DOI: 10.1007/s10562-006-0207-7
Nanometric bimetallic sulfides prepared via thermal decomposition of Ni and Fe heteropolymolybdate emulsions Emir E. Escalona,a Pedro R. Pereira-Almao,b Jimmy Castillo,c Jeannette Hung,d Carmelo Bolı´ var,a and Carlos E. Scotta,* a
Centro de Cata´lisis, Petro´leo y Petroquı´mica, Escuela de Quı´mica, Facultad de Ciencias, Universidad Central de Venezuela, Apartado, 47102, Los Chaguaramos, Caracas, Venezuela b Department of Chemical and Petroleum Engineering, University of Calgary, Calgary, Canada c Escuela de Quı´mica, Facultad de Ciencias, Universidad Central de Venezuela, Caracas, Venezuela d Centro de Fı´sica, Instituto Venezolano de Investigaciones Cientı´ficas, Caracas, Venezuela
NiMo and FeMo nanometric particles were prepared by thermal decomposition of water in oil emulsions, where the aqueous phase was a solution of iron or nickel heteropolymolybdates. Decomposition experiments were carried out at 573 K and 70 Bar of hydrogen, with carbon disulfide added to the emulsions. Solids were characterized by X ray diffraction, confocal microscopy and BET surface area. Thiophene hydrodesulfurization was performed in a continuous flow microreactor at 553 K and 1.0 Bar. Particles with diameters between 370 and 560 nm were obtained, and thiophene HDS was in the order NiMoS > MoS FeMoS > NiS > FeS. The feasibility of using thermal decomposition of emulsions to obtain nanometric bimetallic sulfides particles was shown. KEY WORDS: nanometric sulfides; HDS; thiophene; NiMoS; FeMoS.
1. Introduction Due to actual and forthcoming stringent legislation concerning sulfur content in fuels [1] there is a strong incentive for much more active and selective hydrodesulfurization (HDS) catalysts. Also, as light crude oils reserves dwindle there is a need for processing and upgrading heavy an extra heavy crude oil and tar sands, which are found in vast abundance in different places, thus, for instance the heavy oil and tar sands bitumen in the Alberta Province of Canada and in the Orinoco Belt of Venezuela are each as large as the oil deposits in Saudi Arabia [2]. The use of unsupported catalysts, which could be used either dispersed on a heavy feedstock [3], or in the preparation of bulk metal catalyst for a conventional process, is considered to be a promising way to improve hydrotreatment (HDT) process efficiency [4]. Then, the preparation of nanoparticles of Mo sulfide has gathered great attention recently, and different methods have been reported for its synthesis [5–9]. However, in spite of the well known promotion of Mo by Ni or Co leading to more active HDT catalysts, there are not reports in the literature on the preparation of NiMo or CoMo nanometric sulfides. All preparations of NiMo or CoMo bulk
sulfides, where particle sizes can be estimated, lead to particles of several microns or higher in diameter [10– 12]. Only Ye et al. [12] have synthesized NiMoO2S2 nanoparticles ( 13 nm), using a microemulsion systems, but they were intended to
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