| As is known that, the support determines the performance of supported Au catalysts, especially its morphology and size. With the advantages such as high mechanical strength thermal stability and chemical stability, aluminas have been widely used in industry as support materials. While the enhanced catalytic is also expected for Au loaded on alumina support. Therefore, controllable synthesis of alumina materials has become a challenging issue.Firstly, with Al(NO3)3·9H2O or KA1(SO4)2·12H2O as precursor and urea as precipitant, high dispersed hollow alumina microspheres composed of nanosheets with4-6μm in diameter were prepared by adjusting the concentration of sulfate in reaction system. Due to such novel nanostructure, Au catalysts prepared by deposition precipitation (DP) method show excellent catalytic performance for CO oxidation with the complete conversion at0℃(T50%=-25℃), which is much higher than other Au catalysts.Secondly, with Al(NO3)3·9H2O as precursor and (NH4)2CO3as precipitant, external mesoporous γ-Al2O3nanorods with an aspect ratio of2-4were template-free prepared by the hydrothermal approach and followed by the calcination. The growth process of nanorods was investigated by adjusting hydrothermal time. The results suggest the best hydrothermal condition is24h and100℃. The corresponding Au catalyst exhibits excellent activity and long-term stability with the complete CO conversion at18℃(T50%=-11.2℃) and reactive stability over166h under a space rate of134,000mL h-1gcat-1Finally, a general synthesis of sheet-like γ-Al2O3was proposed by using Al(NO3)3·9H2O as precursor, urea as precipitant and amino compounds as templates after hydrothermal treatment at100℃for24h and followed by a calcination step. When using lysine, thin porous γ-Al2O3sheets with the average thickness～15nm and length680nm can be obtained. Remarkably, Au catalysts can achieve complete conversion at2℃and show extraordinary thermal stability at high annealing temperature up to700and900℃. |
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