XRD and TEM investigation of NiMo/Al-HMS Nanocatalyst Synthesized via Supercritical Deposition

The conventional method for the preparation of Mo supported catalysts on silica or alumina is the incipient wetness impregnation with an ammonium heptamolybdate solution. There are several ways to synthesize supported nanoparticles including impregnation, deposition–precipitation, co-precipitation, sonochemical reduction, chemical vapor impregnation, sol–gel and microemulsion using organic stabilizing agents. The control over either particle dimensions, including the particle size and distribution, or metal concentration in the composites remains the major problems for these methods due to the high surface tension of the liquid solutions [1]. In recent years, supercritical fluids (SCFs) have been widely utilized in material science because their favorable of properties such as low viscosity, high diffusivity, near zero surface tension and strong solvency power for some small molecules [2-4]. The flexibility of SCFs, in terms of tunable salvation strength and access to high operating temperatures and pressures, enables the synthesis of a variety of nanostructured metal. Compared with conventional liquid solvents low surface tension of SCFs permit better penetration to the pores and wetting of the pores than liquid solvents and avoid the pore collapse. This process involves the dissolution of a metallic precursor in a supercritical fluid and the exposure of a substrate to the solution. Among the SCFs, supercritical carbon dioxide (SC CO2), is particularly attractive since it is abundant, inexpensive, non-flammable, non-toxic.HMS (Hexagonal Mesoporous Structure) is a mesoporous silica molecular sieve that is characterized by a hexagonal array of uniform mesopores, a narrow pore size distribution, and high surface area. It has distinct advantages as a catalytic support. Catalytic properties of HMS could be modified by incorporation of different amounts of Al into the HMS framework (Al-HMS) and by HNO3 ion exchange.In this work, synthesis of NiMo/Al-HMS nanocatalyst was performed. The catalysts were characterized by X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM).