Surface and catalytic properties of pure CeO2 and MoO3-doped NiO/TiO2 system

Isopropanol conversion was carried out over TiO2 and pure and variously MoO3- and CeO2-doped NiO/TiO2 solids calcined at 300 and 500 deg C. The concentration of NiO was varied between 9 and 23mol% and those of dopants were changed within 1-6mol%. The effects of calcination temperature, dopant concentration and NiO content on the activity and selectivity of various solids were investigated. The techniques employed were XRD, nitrogen adsorption at -196 deg C and isopropanol conversion at 200-300 and 200-350 deg C for the solids heated at 300 and 500 deg C, respectively, using flow method. The results revealed that TiO2 (anatase) existed as major phase besides TiO2 (rutile), nickel titanate (major phase), NiO and NiMoO3 (minor phase) in heavily MoO3-NiO/TiO2 system. The rutile/anatase ratio was varied between 18% and 36% depending on calcination temperature and dopant concentration. Doping NiO/TiO2 decreased the crystallite size of anatase phase which varied between 7 and 23nm depending on the amount of dopant added and calcination temperature of doped solids. The catalytic activity of TiO2 much decreased by increasing its calcination temperature from 300 to 500 deg C. Opposite trend manifested in case of NiO/TiO2 solids. All solids investigated were selective in isopropanol conversion which proceeds, mainly, via dehydration yielding propene. Small amounts of acetone were produced via dehydrogenation of alcohol investigated specially at reaction temperature below 250 deg C. MoO3 and CeO2 doping of the system investigated resulted in a considerable increase in its catalytic activity. The increase was, however, more pronounced in case of MoO3-doping. The selectivity of various solids was only influenced by the reaction temperature reaching > 90% at temperatures > =250 deg C.