CuO/ZrO₂ catalysts for the production of H₂ through the water-gas shift reaction: Effect of calcination temperature of ZrO₂

A series of CuO/ZrO₂ catalysts were prepared by a deposition-precipitation method using ZrO₂ calcined at various temperatures (120, 250, 350 and 450℃) as supports. The water-gas shift (WGS) reaction was carried out on these catalysts using H₂ rich reactant gas (15% CO, 55% H₂, 23% N₂, 7% CO₂). It was shown that the catalytic activity of the catalysts increased at first and then decreased with increasing calcination temperature of ZrO₂. The catalyst supported on ZrO₂ calcined at 250℃ showed the highest catalytic activity. The structure and reducibility of CuO/ZrO₂ catalysts were studied by various techniques, such as XRD, N₂-physisorption, N₂O titration, H₂-TPR and CO-TPR-MS. The results show that the Cu dispersion and the proportion of catalytically active Cu-O-Zr species ("" represents an oxygen vacancy on ZrO₂ support) decrease with the increase of ZrO₂ calcination temperature. The calcination of ZrO₂ at higher temperature leads to an improvement of the reducibility of Cu-O-Zr species and hydroxyl groups on the CuO/ZrO₂ catalysts, resulting in an easier onset of the surface WGS reaction between surface hydroxyl groups and CO reductant. The two factors reach a balance for the catalyst supported on ZrO₂ calcined at 250℃ (moderate temperature), as is thought to be responsible for the highest WGS activity of this catalyst.