Vital roles of hydroxyl groups and gold oxidation states in Au/ZrO₂ catalysts for 1,3-butadiene hydrogenation
2011
Zhang, Xin | Shi, Hui | Xu, Bo-Qing
Hydrogenation of 1,3-butadiene over Au/ZrO₂ catalysts with different gold loadings and calcination temperatures was reported. The catalysts were characterized in depth to understand their structure–property relationship. Gold oxidation states and surface hydroxyl groups, which were found to be sensitive to the gold loading, calcination temperature, and treatment with water, were shown to play vital roles in the hydrogenation activity of Au/ZrO₂. Continued activity decrease was seen when the density of surface hydroxyl groups was lowered by elevating the pre-calcination temperature of ZrO₂. Fully dehydroxylated Au/ZrO₂ was essentially inactive, but became very active after partial regeneration of the hydroxyl groups by water treatment. Moreover, the activity of Au/ZrO₂ increased with increasing Au³⁺/Au⁰ ratio. Isolated Au³⁺ ions at the support surface showed up to two orders of magnitude higher activity than Au⁰ atoms on Au particles. Several models are proposed to address the structural features of active sites for H₂ activation in Au/ZrO₂ catalysts.
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