| Summary: | 碩士 === 國立中央大學 === 化學工程研究所 === 88 === Recently much effort has been invested in the examination of the potential of microwave power for facilitating chemical reaction. The microwave-assisted synthesis of zeolites is a rather new field of research. In this study, we report the synthesis of SAPO-34 by combination of hydrothermal and microwave heating, to reduce the time of synthesis from 55 hours by hydrothermal heating to 30 hours by hydrothermal heating plus additional 2 hours by microwave heating.
Metal-substituted aluminophosphate molecular sieves have recently received extensive attention for researchers working in molecular sieve science and shape-selective catalysis. The incoporation of metals into the framework can generate Brønsted acidity and ion-exchange capacity on the neutral aluminophosphate molecular sieves and modify the activity and product selectivity on hydrocarbon reactions. In this study, the local environments about the cobalt atoms in as-synthesized, calcined and hydrogen-reduced CoAPO-5 and CoAPO-11 have been studied by X-ray absorption spectroscopy. Results indicate a considerable fraction of Co2+ was oxidized to Co3+ in the calcined samples. On reduction with hydrogen, Co3+ was reduced to Co2+.
Cerium oxide is widely used as a support for Pt and Rh based automobile catalysts. Ceria exhibits special features that make it a promising material for use as a support for such a redox catalyst. However, due to the ever increasing demand upon expensive PGMs, viable non-noble metal catalysts are alternative. CuO supported on ceria is an alternative. The CuO/CeO2 catalysts exhibit high catalytic activity in CO oxidation. The marked enhancement of catalytic activities is due to the combined effect of CuO and CeO2. CuO/CeO2 catalysts show a different behavior with respect to unsupported CuO. In this study, the local environment of copper is examined by means of X-ray absorption spectroscopic at the copper K-edge of CuO/CeO2 with various loading amount. From the results, it’s suggested that, in addition to the well dispersed Cu2+ species at low CuO loading, a small fraction of CuO clusters are formed above CuO loading of 0.8mmole/100m2_CeO2.
The higher emission standard for automobile and motorcycle requires the catalytic converter with high thermal stability and low light off temperature. The high thermal stability of Perovskite makes them good candidates as high thermal stable catalyst in catalytic converter. X-ray absorption spectra of LaCoO3 and LaMnO3 with La partially substituted by Sr and Mn, Co partially substituted by each other were studied in order to understand the local environment around Co and Mn. The oxidation state of Co decreases when Mn substitute a large amount of Co. The oxidation state of Mn increases when Co substitute a large amount of Mn. The coordination numbers of the first oxygen shell decrease upon substitution for LaCoO3 while increase upon substitution for LaMnO3.
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