Surface and catalytic properties of pure CeO 2 and MoO 3-doped NiO/TiO 2 system

Abstract

Isopropanol conversion was carried out over TiO 2 and pure and variously MoO 3- and CeO 2-doped NiO/TiO 2 solids calcined at 300 and 500 °C. The concentration of NiO was varied between 9 and 23 mol% and those of dopants were changed within 1–6 mol%. 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 °C and isopropanol conversion at 200–300 and 200–350 °C for the solids heated at 300 and 500 °C, respectively, using flow method. The results revealed that TiO 2 (anatase) existed as major phase besides TiO 2 (rutile), nickel titanate (major phase), NiO and NiMoO 3 (minor phase) in heavily MoO 3–NiO/TiO 2 system. The rutile/anatase ratio was varied between 18% and 36% depending on calcination temperature and dopant concentration. Doping NiO/TiO 2 decreased the crystallite size of anatase phase which varied between 7 and 23 nm depending on the amount of dopant added and calcination temperature of doped solids. The catalytic activity of TiO 2 much decreased by increasing its calcination temperature from 300 to 500 °C. Opposite trend manifested in case of NiO/TiO 2 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 °C. MoO 3 and CeO 2 doping of the system investigated resulted in a considerable increase in its catalytic activity. The increase was, however, more pronounced in case of MoO 3-doping. The selectivity of various solids was only influenced by the reaction temperature reaching >90% at temperatures ≥250 °C.