A study on the simultaneous catalytic conversion of greenhouse gases CO2 and CH4 over nano-scale Ni-Ce-ZrO2 catalysts

• Main Authors: Ming wang.Lin, 林明旺
• Other Authors: 王清輝
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/64860415217930536798

碩士 === 高苑科技大學 === 化工與生化工程研究所 === 98 === The greenhouse effect as a result of carbon dioxide (CO2) causes the raise of earth temperature and unusual climate phenomenon. Nowadays it is an important topic to find the way of CO2 reduction or conversion. Carbon dioxide can be converted to CO, H2, CH4, and other organic compounds by catalytic reduction under mild conditions. The key factors for developing a successful catalytic reduction process for CO2 mitigation are preparing a highly active catalyst, employing a proper reduction mode and designing a feasible and high performance reactor. In this study, the nano Ni-Ce-ZrO2 catalysts will be prepared by the sol-gel method and used for the conversion of CO2 and CH4. A proper catalyst will be selected by comparing the performances of those catalysts. We will further investigate the effect of reaction conditions, such as catalyst loading, Ni concentration, Ce concentration, Zr concentration, CO2 concentration, CH4 concentration, O2 concentration and reaction temperature, etc., on the conversion of CO2. The surface properties of those catalysts will be characterized (including XRD, TEM and SEM) in order to understand the roles they play in this catalytic reaction. NiO/CeO2 is conformed as the most active catalyst among CeO2-supported metal oxide catalysts（Fe2O3, NiO, MnO2, MoO3, Cr2O3 and Co3O4） for the conversion of CO2 and CH4. With NiO as the active species, NiO /CeO2 was found to be the most suitable support of those tested (CeO2, Al2O3, TiO2 and V2O5). The results of activity test indicate that with Ce1-XZrXO2 (X=0、0.1、0.2、0.4、0.6、0.8、1) as the support for the conversion of CO2 and CH4. Partire substitution of Ce with Zr increases the activity and an optimal substitution fraction (X=0.2) exists in the NiO/Ce1-XZrXO2 catalysts. When changing Ni loading in NiO/Ce0.8Zr0.2O2, we discover that the NiO/Ce0.8Zr0.2O2 catalyst with 15 wt % Ni is the most active. NiO/Ce0.8Zr0.2O2 does not decay and has a high activity at 700℃ for a long-time operation. For the catalytic conversion of CO2 and CH4, nanosized Ce0.8Zr0.2O2 was coated to honeycomb support and used as the support to prepare NiO/Ce0.8Zr0.2O2 catalysts by incipient wetness impregnation method. The results of activity test indicate that coating a Ce0.8Zr0.2O2 layer with citric acid sol-gel coating method and loading 15 wt% Ni with incipient wetness impregnation method give the highest activity. At the end of this study, the activities and stabilities of the powder catalyst and the monolithic catalyst were compared. The results show that monolithic catalyst has a better performance and hence has a potential for being applied to conversion of CO2 and CH4.