Cobalt doping modification for enhanced methane conversion at low temperature in chemical looping reforming systems
Cobalt doping modification for enhanced methane conversion at low temperature in chemical looping reforming systems
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DOI：
10.1016/j.cattod.2019.06.016
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发表时间：
2020-06
期刊：
影响因子：
5.3
通讯作者：
Mengqing Guo;Zhuo Cheng;Yan Liu;L. Qin;Josh W. Goetze;Jonathan A. Fan;L. Fan
中科院分区：
文献类型：
--
作者：
Mengqing Guo;Zhuo Cheng;Yan Liu;L. Qin;Josh W. Goetze;Jonathan A. Fan;L. Fan
化学循环重整（CLR）是一种低成本、低环境影响的甲烷制合成气方法。化学环转化体系面临的主要挑战是开发具有高反应活性、高携氧能力和长期耐用性的氧载体。研究表明，在铁基氧载体中加入低浓度的钴掺杂剂可以显著提高低温CLR工艺的反应活性，同时保持其可回收性。从600 °C到800 °C，与纯氧化铁氧载体相比，共掺杂氧化铁的甲烷转化率提高了约300%。结果表明，在不同温度下，Co掺杂浓度为2%对甲烷转化率和氧载体成本影响最大。密度泛函理论（DFT）计算表明，Co掺杂剂对氧空位的形成有短期影响。共掺杂诱导的氧空位显著降低了氧化铁氧载体表面ch4重整的能垒，导致反应性增强。我们的研究结果为降低化学环系统中的甲烷重整温度，同时提高合成气收率和期望的氧载体可回收性提供了一条途径。
Chemical looping reforming (CLR) is a promising strategy of methane conversion to syngas with low cost and minimal environmental impact. A major challenge for chemical looping reforming systems is the development of oxygen carriers that have high reactivity, high oxygen carrying capacity, and long-term durability. We demonstrate that the addition of a low concentration of cobalt dopant to iron-based oxygen carriers can dramatically enhance the reactivity in CLR processes at low temperatures while maintaining the recyclability. The methane conversion increased by around 300% for Co-doped iron oxide compared to pure iron oxide oxygen carriers from 600 °C to 800 °C. It was found that 2% Co dopant concentration is optimal for methane conversion rate and cost of oxygen carriers at different temperatures. Density functional theory (DFT) calculations reveal that the Co dopant has a short-range effect on the formation of oxygen vacancies. The Co-doping-induced oxygen vacancy significantly reduces energy barriers of CH4reforming on the surface of iron oxide oxygen carriers, leading to the reactivity enhancement. Our findings provide a pathway to lower the methane reforming temperature in chemical looping systems, while improving the syngas yield with desired oxygen carrier recyclability.