ACTIVITY AND SELECTIVITY OF NANO-CRYSTALLINE NIO AND NI-METAL SUPPORTED ALUMINA SYSTEM AS BEING INFLUENCED BY MOO3 DOPING (Published)
The catalytic conversion of cyclohexane was carried out on NiO and Ni-metal supported on alumina doped with MoO3. The extent of NiO loading was 13 weight % and 8 weight %, the amount of dopant was fixed at 2 weight %. Pure and doped solids were prepared by wet impregnation method using a known weight of γ-Al2O3 with known amount of nickel nitrate and molybdic acid dissolved in a least amount of distilled water making paste, dried, then calcined in dry air at 500 0C. Nickel alumina doped with MoO3 were readily obtained by heating the calcined solids in a current of H2 at 500 0C. Physicochemical surface and catalytic property of different solids investigated were characterized by XRD, N2 adsorption at –196 0C and catalytic conversion of cyclohexane using flow system under normal pressure at a temperature range of (400 – 480) 0C. The results revealed that NiO supported alumina existed as nanocrystalline Ni and aluminum oxides, and the H2 treatment at 500 0C resulted in the formation of big sized nickel crystals. The SBET of NiO-alumina suffered a measurable decrease upon doping with 2 weight % of MoO3. The concentration of MoO3 being far below the detection limit of X-ray diffractometer and its intense existence in the diffractograms of the doped solids calcined at 500 0C suggested on effective migration of Mo- species from the bulk to the surface of the solids. The activity and selectivity of different solids were found to be dependent on Ni- content, the presence of Mo- as dopant, and the oxidation state of the nickel present. The main catalytic reaction products were, mainly, dehydrogenation products whose content are dependent on the nature of the catalyst used. The increase in Ni- content increased the catalytic activity. The co-existence of MoO3 and NiO showed catalytic activity much bigger than those measured for the individual supported NiO and MoO3 catalysts.
Keywords: Alumina System, Moo3 Doping, Nano-Crystalline Nio. Ni-Metal