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This paper studied the effect of temperature ramping rate during calcination on characteristics of nanoscale zirconia and its catalytic performance for isosynthesis. The physical properties, i.e. BET surface area, cumulative pore volume, cumulative pore diameter and the phase composition in zirconia, acid-base properties and surface properties such as Zr 3+ quantity, were characterized. Increase in the temperature ramping rate of calcination resulted in a higher composition of the tetragonal phase, but it showed insignificant influence on the other physical properties. Considering the catalytic activity, the acid sites did not affect the activity, but the basic sites depended on the fraction of the tetragonal phase in zirconia which was related to the selectivity to isobutene. The intensity of Zr 3+ on the surface varied with the change in the heating rate of calcination. Both the tetragonal phase composition in zirconia and the quantity of Zr 3+ were the key factors affecting the selectivity to isobutene in hydrocarbons. Moreover, the maximum value of the product selectivity to isobutene on the ZrO 2 (5.0) catalyst was attained at the highest concentration of Zr 3+ . |
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