Copper Manganese Oxide Catalysts:Synthesis And CO Oxidation Property

The development of catalysts for low temperature carbon monoxide oxidation has been researched hotly due to the potential areas of application in industrial, environmental and domestic fields. Compared to the noble metal catalyst, copper manganese oxide is one of the catalysts with relatively good catalytic activity but low cost. The process of conventional co-precipitation method has been optimized aiming to obtain copper manganese oxide catalyst with high performance of CO oxidation at ambient temperature. The deactivation mechanism of copper manganese oxide catalyst was also investigated.Ammonia was introduced in the conventional co-precipitation method (inverse), and the influence of its concentration and adding time on the physicochemical property of the copper manganese oxide catalyst by was discussed. The result showed that ammonia perceptively etched copper species rather than manganese species, thus a controllable surface Cu/Mn ratio could be obtained. The selective etching improved the specific surface area of copper manganese oxide catalyst and the catalytic performance of copper species. O2-TPD and H2-TPR indicated that the improvement of catalytic activity of the etched catalyst could be attributed to the enhanced mobility of lattice oxygen and synergy between copper species and manganese species.We invested the difference between catalyst calcined in a reactor and that calcined in a muffle oven, and the calcination conditions included moisture addition, oxygen content and calcination temperature were taken into consideration. It is found that moisture can poison the catalyst, whereas a high oxygen content of the calcination atmosphere promotes catalytic activity. The catalyst calcined in the reactor at300℃for2h under an atmosphere of20%O2and80%N2shows a complete oxidation of CO at30℃.We designed a parallel-flow instrument for the preparation of active catalysts. In this way, the catalyst displayed a larger specific surface area and improved catalytic performance compared to the one prepared using an inverse co-precipitation method. CO2-TPD and CO pulse technique indicated the existence of reactive oxygen species on the catalyst surfaces. Furthermore, the catalyst deactivation at low temperature was ascribed to deep reduction of the catalyst surface by CO, which leading to a shortage of active oxygen species. Meanwhile, the overdue desorption of CO2(CO32-) generated during the reaction also played an important role in catalyst deactivation since it blocked catalytic cycle of CO oxidation.