Direct conversion of CH4 to oxy-organics by N2O using freeze-drying FeZSM-5

Abstract

Direct conversion of CH4 to oxy-organics with N2O is a promising technique for greenhouse gas elimination and chemicals production, and iron-supported zeolite is a common catalyst. However, traditional impregnation method is apt to obtain adverse aggregations rather than active centers due to precursor movement caused by evaporation drying. In this work, freeze drying is applied to restrict iron species movement in preparing FeZSM-5. Compared with traditional evaporation-drying catalyst, uniformly distributed iron species are observed in freeze-drying catalyst. And the iron distributions imposes a strong impact on iron structure and property of ZSM-5. In freeze-drying catalyst, more extraframework iron species, including more active centers, and fewer deep reaction centers (large α-Fe2O3 particles and Bronsted acids) are obtained. At 573 K, the oxy-organics yield in freeze-drying catalyst is 60% higher than that in evaporation-drying catalyst. Additionally, active centers are found to contain Fe2+-O-Al structure, formed by interaction of iron species with tetrahedral aluminum in ZSM-5 framework.