Role of ZrO₂ in Cu/ZnO/ZrO₂ catalysts prepared from the precipitated Cu/Zn/Zr precursors

Abstract

In Cu/Zn/Zr precursors prepared by coprecipitation, Zr ions showed no effect on a substitution level of Cu2+ by Zn2+ in the zincian malachite (zM) and were not incorporated into zM lattice upon precipitation and subsequent ageing. As hydroxyl-rich Zr aggregates were precipitated independent of mixed Cu/Zn precipitates, they served as a barrier to formation of larger Cu/Zn particles during precipitation and transformation into Cu/Zn needles during ageing. After calcination of Cu/Zn/Zr precursors with higher Zr contents, smaller CuO/ZnO particles were produced in between which amorphous ZrO2 was situated. Upon reduction of CuO/ZnO/ZrO2 with more Zr, this type of ZrO2 resulted in formation of smaller Cu-0 particles yielding the higher Cu dispersion. However, the specific copper surface area and catalytic activity of the reduced Cu/ZnO/ZrO2 exhibited a volcano-type relationship with the Zr/( Cu + Zn) ratio. This could be a combined result between the lower amount of total Cu and the higher Cu dispersion.