Preparation and characterization of nanocatalysts containing HPW

Heteropoly acids (HPAs) containing Cs have had rapid growth in the last decade as solid acid ‎catalysts. They can offer several advantages in terms of catalytic performance as well as strong acid ‎and redox sites. Among various types of heteropolyacid structures, Keggin-type structure has ‎significantly high acidity and thermal stability. In particular, the Cs-exchanged Keggin-type ‎heteropolyacid is well maintained at high temperatures, usually over 500°C. Conventionally, a ‎suitable transition metal (M = Pt, Pd, Ni, Mo and Co) has been applied as the main active metal ‎component, which is deposited on the acidic supports. For example, it is of great interest to develop ‎new hydrocracking catalysts composed of H3PW12O40, as acid sites and M as the metal sites.‎In this research, Ni-Mo-Cs/HPW/Al2O3 nanocatalysts were prepared by impregnation method. First, ‎alumina support (specific surface area 273 m2g-1, 35–70 mesh) was impregnated with a solution ‎containing the desired quantities of Ni(NO3)2 (98%, BDH), (NH4)6Mo7O24.4H2O (99.9%, Merck) ‎and Cs2CO3 (99.9% Merck) and then the samples were impregnated with a solution containing the ‎desired quantity of H3PW12O40 (99.9%, Merck). The synthesized samples were characterized by X-‎ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDX). Morphology of the ‎samples was studied by scanning electron microscope (SEM) and the surface area, pore volume and ‎pore size of the catalysts were determined by BET method. The obtained results indicate that the ‎size of prepared samples are in nano-scale range, in addition, the synthesized samples have spherical ‎shape. The surface area of the sample that contain Mo and Ni is more than that of contain only Ni ‎or Mo.‎