Preparation of Ni, Mo and NiMo Nanoparticles From Transient W/O Emulsions

Abstract:

The preparation of hydrodesulphurization HDS catalysts constitutes an interesting topic of research due to the stringent environmental regulations and economic challenges that the refining industry is facing. To meet present and future demands for cleaner fuels, more active and selective catalysts are needed. In addition, the conventional oil reserves are depleting at a high rate, the characteristics of new hydrocarbon sources, more sour and heavy, represent another challenge that is turning the attention on developing better and more efficient HDS catalysts (1). Several possible ways for improving the catalysts activity have been envisaged, including the use of new supports, novel active phases, or optimizing the preparation procedure. Commercial catalysts used in upgrading are supported and used in a fixed or ebullated bed reactor. These catalysts have a tendency to deactivate due to pore plugging (2). A good alternative to supported catalysts are highly dispersed transition metals (3); their use may offer an appealing solution for upgrading heavy feedstock and petroleum residues without the difficulties presented by commercial catalysts due to their greater surface area and increase in the reactive site-to-mass ratio (4). Furthermore, nanoparticles are recommended since they show higher catalytic activities and better navigate and/or further penetrate the porous media, if they are intended for insitu upgrading. Different methods have been used to produce nano scaled structured materials but often are of not practical industrial application (5-10). There are many publications on the preparation of nanoparticles from microemulsions but these present the disadvantage of requiring large amounts of surfactants and not being stable under HDT conditions. One industrially convenient methodology that can be used for the production of nanoparticles is to employ transient emulsions. We describe transient emulsions (TEs) as those emulsions sustained by the energy supplied to create them, but when the energy source is cut off, the emulsion tends to brake in a short frame of time. In the present work, the preparation of inorganic nanoparticles of Ni, Mo, NiMo was carried out using thermal decomposition of transient emulsions. A study was done taking into consideration different parameters for the preparation of the transient emulsions, like the concentration of the precursor molecules, water percentage, use of surfactant, and manner of mixing the various solutions. The characterization of such minute particles is of great importance since the characteristics of these materials depends largely on particle size. Physicochemical characterization was done via DLS, TEM (EDAX). Also, we evaluated the performance of the catalyst particles produced for the hydrotreating of VGO.

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