| Due to the high mechanical strength and good stability,alumina is widely used as catalyst or support in petrochemical industry.However,the catalytic performance of supported Au/Al2O3 catalysts need to be further improved.A large quantity of literatures has shown that the textural properties,crystal structure,morphology,surface properties of alumina support have an impact on performances of catalysts.So,rational design and preparation of suitable alumina as support is significant for better catalytical performance.CO oxidation is an ideal model reaction to investigate the relationship between support and activity of catalysts.From the perspective of preparation routes,hydrothermal method,precipitation method and solid-state method was conducted to prepare alumina in this thesis,meanwhile,CO oxidation was as an model reaction to distinguish the differences among three methods,aiming at providing a new horizon achieving the large scale production.The specific research and content are as follows:（1）Al（NO3）3·9H2O and CO（NH2）2 were used as raw materials.The alumina precursor was obtained under mild hydrothermal condition by adjusting molar ratio of reactant.After thermal decomposition at 500℃,1D nanorod in regular morphology and good dispersity with a length of 2μm and a diameter of 400 nm approximately was able to be produced finally.Au/Al2O3was prepared by deposition-precipitation method.The catalytic performance for CO oxidation over it was evaluated.A 100%CO conversion at 40℃can be reached at the space velocity of12000 mL h-1 g-1cat.（2）Taking Al（NO3）3·9H2O as aluminum source NH4HCO3 as precipitator,The white precipitation was obtained by adding Al（NO3）3 solution into NH4HCO3 solution dropwise.Then the alumina nanosheet was prepared following by aging and calcination.The effect of aging time,aging temperature and calcination temperature on the crystal structure and morphology of the precursor were investigated systematically at the same time.The optimized reaction conditions were gotten after experiments and analysis:aging at 80℃for 12 h,calcinations at600℃for 2 hours.Alumina supported nanometer gold catalyst prepared by DP method shows excellent performance for CO oxidation.The semi conversion of CO is-11℃and CO can be fully converted into CO2 at 20℃.（3）Al（NO3）3·9H2O and NH4HCO3 were used as aluminum source and the precipitator respectively.Solid-state reaction occurs when both of them were ground together in agate mortar,then white solid was formed.After aging about 24 h in a 100℃oven following by calcination,rod-like nanometer alumina was obtained.In the experiment,the effect of molar ratios of NH4HCO3/Al on crystallinities and morphologies of AACH was investigated.The AACH with length of 100-150 nm and diameter of 30-50 nm can be obtained with molar ratio NH4HO3/Al=4:1.After thermal decomposition of AACH at 600℃,alumina was prepared as support for nanometer gold catalyst,which can convert CO at 120℃. |
