Preparation Of The New Types Of Iron And Nickel-based Catalysts For The Oxidation Of Light Alkanes

This thesis mainly focuses on adopting a new way-vapor deposition to prepare iron and nickel-based supported catalysts and applying them to the oxidation of light alkanes. The research work can be divided into several aspects: set up the equipment for vapor deposition, prepare the iron and nickel-based supported catalysts using this method, explore the impact of the preparation conditions for iron and nickel content, learn more about the deposition process, study their catalytic performance for ODHE reactions, and then compare them with catalysts prepared by impregnation.After improving the previous devices for vapor deposition, the iron-based supported catalysts were prepared using ferrocene as the precursor compounds. The reason why the precursor could be fixed on the support was maily due to physical adsorption. With the increase of the flow rate of the carrier gas and the deposition temperature, the content of iron gradually reached the top point then began to decrease. XRD revealed that a high dispersion of iron species was found in catalysts prepared by vapor deposition and no bulk Fe2O3 appeared when calcinated under higher temperature. By contrast, in catalysts with the same iron content prepared by impregnation, when iron loadings exceeded a certain value or catalysts were calcinated under higher temperature, iron species were easy to aggregate.The activities of these catalysts(iron content was 2% to 8%) were explored under steady-state conditions between 370℃ and 490℃, with oxygen/ethane 1:2 and 1:1 ratio. Research found that ethane conversion, average turnover frequency of ethane and ethylene yield of catalysts prepared by vapor deposition for ODHE reactions were much more superior than those prepared by impregnation. The apparent activation energy of the former was less than the latter. Investigation on the catalytic performance of samples prepared by vapor deposition at 400℃ showed that higher iron loadings were not always better, the maximum ethane conversion and ethylene yield appeared when iron content was about 4%.The nickel-based supported catalysts were prepared through vapor deposition using nickel acetylacetonate as the precursor compounds. The nickel loading could be raised by increasing the deposition temperature, unilateral deposition times and precursor concentration. The activities of these catalysts(nickel content was 1% to 2%) were explored under steady-state conditions between 400℃ and 500℃, with oxygen/ethane 1:2 ratio. Research found that ethane and oxygen conversion of catalysts prepared by vapor deposition for ODHE reactions were much more superior than those prepared by impregnation. The apparent activation energy of catalysts prepared by two different methods for ODHE reactions were calculated respectively. These values have attached great importance to the mechanism studies in the future.