CuO/ZrO₂ catalysts for water-gas shift reaction: Nature of catalytically active copper species

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• 作者：Yanjie Zhang ; Chongqi Chen ; Xingyi Lin ; Dalin Li ; Xiaohui Chen ; Yingying Zhan ; Qi Zheng
• 关键词：Water&ndash ; gas shift reaction ; Copper ; Zirconia ; Active species ; Surface hydroxyl groups
• 刊名：International Journal of Hydrogen Energy
• 出版年：6 March, 2014
• 年：2014
• 卷：39
• 期：8
• 页码：3746-3754
• 全文大小：1591 K

文摘

A series of CuO/ZrO₂ catalysts with different Cu loadings (4.1, 6.1 and 8.4聽wt.%) were synthesized by a deposition-precipitation method and evaluated with the water-gas shift (WGS) reaction. In order to distinguish the different supported copper oxide species, (NH₄)₂CO₃-leaching process was conducted on the three CuO/ZrO₂ catalysts. The parent and leached catalysts were characterized by ICP-OES, XPS, XRD, N₂-physisorption, N₂O titration, UV-Vis DRS, H₂-TPR and CO-TPR. The results reveal that three types of copper oxide species are present on the parent CuO/ZrO₂ catalysts: (伪) highly dispersed CuO that is weakly bound with ZrO₂; (尾) strongly bound Cu-[O]-Zr species, which can not be leached by (NH₄)₂CO₃ solution and is possibly associated with the surface oxygen vacancy of ZrO₂; (纬) crystalline CuO. The XRD and TEM results of the freshly reduced catalysts disclose that the three types of CuO species are transformed into their corresponding metallic states after the H₂-pretreatment. It is found that the reaction rate correlates well with the amount of Cu-[O]-Zr species, indicating the metallic Cu derived from this species should be the catalytically active copper species for the WGS reaction. Moreover, CO-TPR results disclose that the Cu-[O]-Zr species play a significant role in promoting the reactivity of the surface hydroxyl groups, as is thought to be responsible for the high WGS activity of the CuO/ZrO₂ catalysts.