Effects of Thermal Treatment and Fluoride Ion doping on surface and Catalytic properties of NiO-ZrO2 catalysts.

12-05-2016 06:18

 a series of NiO/ZrO2 hydrogels (5-25 wt% NiO) were co-precipitated with the aid of NaOH-Na2C2O4 solution. Two fluorinated hydrogels were also prepared by
wet impregnation method. The samples were calcined in the temperature range 550-850oC.
The surface properties of the samples were determined using DTA, XRD and nitrogen
adsorption at 77 K. The conversion of isopropanol was tested using microcatalytic pulse
technique. DTA measurements showed that the addition of nickel oxide to zirconia influences
the phase transition of ZrO2. XRD reveals that the tetragonal phase was formed at ≤ 650oC
while a biphasic mixture was obtained at ≥ 750oC. No spinel structure was detected by both
DTA and XRD techniques and only traces of cubic NiO were detected for samples containing
≥ 15 wt% nickel oxide and calcined at ≥ 750oC. Significant changes in texture, surface acidity
and catalytic activity were found as a result of the effects of thermal treatment and chemical
composition. Incorporation of fluoride ion greatly increased the surface acidity and
consequently enhanced the dehydration activity. Dehydration activity is related to the amount
of surface acidity while the dehydrogenation of this alcohol is sensitive to NiO content.

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