铈铁复合氧化物制备及其甲烷选择性氧化制合成气催化性能

Preparation and Catalytic Performance of Cerium Iron Complex Oxides for Selective Oxidation of Methane to Synthesis Gas

用共沉淀法制备了CeO2-Fe2O3氧载体。在固定床反应器中研究了氧载体中晶格氧部分氧化甲烷的反应,并用空气为氧源进行了氧载体还原-氧化再生循环实验,通过XRD,O2-TPD,H2-TPR等手段对氧载体进行了表征。结果表明,CeO2-Fe2O3氧载体中的体相晶格氧适于部分氧化甲烷制合成气。新鲜的氧载体上存在二种氧:有强氧化性的吸附氧(包括弱吸附分子氧和表面晶格氧)和高选择性的体相晶格氧。在高温条件下(800℃),CeO2-Fe2O3氧载体在消耗掉吸附氧后能均匀地释放出体相晶格氧将甲烷高选择性的氧化为CO和H2。循环实验表明,可以通过循环来提高合成气的选择性,经长时间的循环CeO2-Fe2O3氧载体上有CeFeO3出现,但其并未对选择性造成不利影响。

The cerium iron complex oxides oxygen carrier was prepared by co-precipitation method. The reactions between methane and lattice oxygen from the complex oxides were investigated in a fixed micro-reactor system. The reduced oxygen carrier could be reoxidized by air and restored its initial state. The characterizations of oxygen carriers were studied using XRD, O2-TPD and H2-TPR. The results showed that the bulk lattice oxygen of CeO2-Fe2O3 was found to be suitable for partial oxidation methane to synthesis gas. There were two kinds of oxygen species on the oxygen carrier： the stronger oxygen species was responsible for complete oxidation of methane and the methane could be selectively oxidized to CO and H2 by the weaker oxygen specie （bulk lattice oxygen） at a higher temperature, then the lost bulk lattice oxygen could be selectively supplemented by air re-oxidation at an appropriate reaction conditions. There was CeFeO3 appeared on the oxygen carrier after 10 successive redox cycles but it was not bad for the selectivity of CO and H2.