采用不同浸渍顺序制备了三种Ir-Fe催化剂,其CO选择氧化(PROX)反应活性差别很大,其中共浸渍的Ir-Fe催化剂活性最高.吸附量热研究表明,三种催化剂的H2和CO吸附存在差别.通过对三种催化剂还原后、再氧化和反应后准原位57Fe穆斯堡尔谱的研究,得到各种Fe物种信息.结果表明,三种制备方法影响催化剂中Ir-Fe相互作用强度,导致催化剂中Fe物种的氧化还原性能不同.催化剂中Fe2+(a)的含量与CO转化率呈正比关系,Fe2+(a)是PROX反应过程中活化氧的活性中心.浸渍顺序改变了Ir-Fe间相互作用强度,从而改变Fe2+(a)物种含量,影响PROX反应活性.Ir-Fe间的相互作用可以稳定活化氧的Fe2+(a)物种,为今后研究金属-金属间的相互作用提供借鉴.
New insights on the interaction between Ir and Fe oxide are reported. Three Ir-Fe catalysts were prepared by different impregnation sequences of an Al2O3 support. Co-impregnation gave a better catalyst for the preferential CO oxidation in H2 (PROX) reaction. Micro-calorimetry data showed that the adsorption of CO and H2 were different. Quasi in situ M(o)ssbauer data of the three catalysts after reduction, reoxidation, and PROX reaction showed that a strong interaction between Ir and Fe affected the redox properties of the Ir-Fe catalysts. CO conversion was proportional to the concentration of the Fe2+(a) species, thus, Fe2+(a) was an active site in the PROX reaction. The impregnation sequence influenced the interaction between Ir and Fe and consequently, the amount of the active Fe2+(a) species. A strong Ir-Fe interaction stabilized the active Fe2+ sites for activating O2.
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