Comparative study of Au/ZrO2 catalysts in CO oxidation and 1,3-butadiene hydrogenation |
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Authors: | Xin Zhang Hui Shi Bo-Qing Xu |
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Affiliation: | aInnovative Catalysis Program, Key Lab of Organic Optoelectronics & Molecular Engineering, Department of Chemistry, Tsinghua University, Beijing 100084, China |
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Abstract: | This work investigates the effects of Au3+/Au0 ratio or distribution of gold oxidation states in Au/ZrO2 catalysts of different gold loadings (0.01–0.76% Au) on CO oxidation and 1,3-butadiene hydrogenation by regulating the temperature of catalyst calcination (393–673 K) and pre-reduction with hydrogen (473–523 K). The catalysts were prepared by deposition–precipitation and were characterized with elemental analysis, nitrogen adsorption/desorption, TEM, XPS and TPR. The catalytic data showed that the exposed metallic Au0 atoms at the surface of Au particles were not the only catalytic sites for the two reactions, isolated Au3+ ions at the surface of ZrO2, such as those in the catalysts containing no more than 0.08% Au were more active by TOF. For 0.76% Au/ZrO2 catalysts having coexisting Au3+ and Au0, the catalytic activity changed differently with varying the Au3+/Au0 ratio in the two reactions. The highest activity for the CO oxidation reaction was observed over the catalyst of Au3+/Au0 = 0.33. However, catalyst with a higher Au3+/Au0 ratio showed always a higher activity for the hydrogenation reaction; co-existance of Au0 with Au3+ ions lowered the catalyst activity. Moreover, the coexisting Au particles changed the product selectivity of 1,3-butadiene hydrogenation to favor the formation of more trans-2-butene and butane. It is thus suggested that for better control of the catalytic performance of Au catalyst the effect of Au3+/Au0 ratio on catalytic reactions should be investigated in combination with the particle size effect of Au. |
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Keywords: | Au/ZrO2 catalysts Gold catalyst Cationic gold CO oxidation Hydrogenation Catalytic sites 1 3-Butadiene |
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