Abstract:

CO hydrogenation was studied over zirconia catalysts. The catalysts, which were classed into three types of samples-the fresh, used and specially treated catalysts, were characterized by means of EPR spectroscopy. A strong signal at g⊥=1 .976 and g||=1.961, which was assigned to Zr3+ ion on the surface of ZrO2, was observed for the fresh catalysts. In contrast, unique strong and sharp signal at g=2.0024, which was assigned to dissociated H atom, also was observed for the used catalysts. Further verification of the assignments was carried out by EPR characterization of the specially treated catalysts. These results show that Zr3+ ion might involve in CO hydrogenation. Quantitative studies reveal that there is a close linear relation between Zr3+ ion and the selectivity to isobutene for the reaction over ZrO2. Finally, a possible mechanism of the catalytic reaction via a surface species Zr(Ⅲ)(CO)2 was proposed.

Key words: EPR spectra, ZrO₂ catalyst, Zr³⁺ ion