Chemical looping combustion (CLC) is a promising technology for fossil fuel combustion with inherent CO₂ separation from flue gases, circumventing high cost for CO₂ capture and NO_x elimination as in conventional combustion processes. Metal oxides are commonly used as oxygen carriers (OCs) in CLC. However, sintering and coking of OCs and the consequent degradation in their activity and durability during multiple cycles inhibit the practical applications of CLC technology. In the present study, we employed a silicalite-1 zeolite support to achieve OCs with high resistance against sintering and coking in CLC. Iron oxides (Fe₂O₃) with methane fuel were employed to demonstrate the approach and to quantify the influence of silicalite-1 support on conversion efficiency, durability, and selectivity of these OCs in CLC cycles. Two iron oxide–zeolite geometrical structures, a core–shell Fe₂O₃@silicalite-1 and a Fe₂O₃-impregnated silicalite-1 (Fe₂O₃/silicalite-1), were created to improve Fe₂O₃ stability. The CLC tests showed that both structures led to less aggregation of Fe₂O₃ OCs at 1223 K. A comparison between Fe₂O₃/silicalite-1 and Fe₂O₃@silicalite-1 in CLC tests illustrates that Fe₂O₃ impregnated in zeolite had higher durability than in the core–shell structure. The selectivity of CH₄ to CO₂ followed the order of Fe₂O₃/silicalite-1 > Fe₂O₃@silicalite-1 ≫ bare Fe₂O_3. The high selectivity of Fe₂O₃/silicalite-1 to CO₂ in CLC tests can be attributed to the encapsulation of Fe₂O₃ inside channels of silicalite-1 that provides physical barriers for aggregation of OCs in CLC cycles as well as coke deposition on OCs. In conclusion, our study of the structure–function relation for silicalite-1-supported Fe₂O₃ OCs can form the basis for the development of silicalite-1 as an efficient support in chemical looping applications.

中文翻译：

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沸石支持的氧化铁作为用于化学环流燃烧的耐用和选择性氧气载体

化学循环燃烧（CLC）是有前途的技术化石燃料燃烧与固有CO ₂从烟道气分离，绕过用于CO高成本₂捕获和NO _X消除如在常规燃烧过程。金属氧化物通常用作CLC中的氧载体（OCs）。但是，OC的烧结和结焦以及随之而来的它们在多个循环中的活性和耐用性降低，抑制了CLC技术的实际应用。在本研究中，我们采用了silicalite-1沸石载体来实现具有高抗烧结性和抗结焦性的OCs。氧化铁（Fe ₂ O ₃）与甲烷燃料一起被用来证明该方法并量化sillite-1载体对CLC循环中这些OC的转化效率，耐久性和选择性的影响。为了改善Fe ₂ O _3的存在，创建了两种氧化铁-沸石几何结构，即核-壳Fe ₂ O ₃ @ silicalite -1和Fe ₂ O ₃浸渍的silicalite-1（Fe ₂ O ₃ / silicalite -1）。稳定。CLC测试表明，这两种结构均导致在1223 K时Fe ₂ O ₃ OCs的聚集较少。Fe ₂ O ₃ / silicalite-1与Fe _2的比较CLC测试中的O ₃ @ silicalite-1表明，沸石中浸渍的Fe ₂ O ₃比核-壳结构具有更高的耐久性。CH的选择性₄至CO ₂随后Fe的顺序₂ ö ₃ /硅沸石-1>的Fe ₂ ö ₃ @硅沸石-1»裸露的Fe ₂ ö ₃的Fe的高选择性₂ ö ₃ /硅沸石-1至CO CLC测试中的₂可以归因于Fe ₂ O ₃的封装在silicalite-1的通道内部，它为CLC循环中OC的聚集以及OC上的焦炭沉积提供了物理屏障。总之，我们对silicalite-1负载的Fe ₂ O ₃ OCs的结构-功能关系的研究可以为silicalite-1的开发提供基础，而silicalite-1可以在化学环化应用中作为一种有效的载体。