Study Of The Nano-Gold Catalyst Supported On Zeolite For CO Oxidation In Low Tempreture

It is common knowledged that the supported nano-gold catalysts are a sort of new type catalyst,and exhibited good catalytic activity for many reactions,including low temperature oxidation of CO,reduction of NOx, oxidation of volatile organic compounds,water-gas shift reaction as well as reaction in the fuel-cell. The potential application of these catalysts in the industrial and environmental protection results in a hot point for research in the catalysis field.In this work, zeolite was as a support,the CO oxidation was as a test reaction and as a probe to understand the relationship of structure of zeolite and the catalytic performance.Then the zeolite was modified by ions exchanging of Fe³⁺ and to be a new support.The effects of modifying on various zeolites were inspected.Finally, a series of catalysts have been prepared by different method under different condition, and the effects of various treatment on the catalytic performance were carried out.The obtained catalysts were characterized by BET, XRD, TPR, XPS, TEM, UV-vis DRS and AAS.The origin of activity as well as active site were discussed also.The experiment results indicate that:1.The structure of zeolite has the remarkable influence on the catalytic activity. When the Si/Al is smaller in the zeolite,the bigger specific area(BET) is obained, while the corresponding catalytic performance is better also.2.The influence of modification on zeolite's structure and catalyst activity is different for various zeolites.For example,using modifiedβ-zeolite which exchanging with Fe³⁺ as a support, the catalyst was preprared by deposition- -precipitation method, the obtained catalyst displayed the good catalyzed activity;whereas the Y-zeolite exchanged with Fe³⁺, the results of XRD and FTIR proved that the original structure of Y-zeolite has been destroyed irreversiblily, therefore the Y-zeolite can not be modified by exchanging with the Fe³⁺ ions.3.The influence of preparation method on the catalyzed activity was discussed. Preparation method is related to the isoelectric point of support, the deposition-precipitation method is suitable for the support which isoelectric point(IEP) is between 6 and 9; but the ion-exchange method is suitable for the acidic support.4 The influence of preparation condition on the catalyzed activity has been learned in this work. The Y-zeolite as support, the ion-exchange method was used for preparing a series of catalysts in which under the different pH value. The results showed that the condition of pH=6 was the optimum condition for preparation of this kind of catalysts.5.The results of the TPR and the XPS indicated that the existence of active component-gold is benefical for the reduction of the support and increase of catalytic activity.The ionic gold or the Au^δ+(0<δ≤3) species are active components in that catalysts.