LaNixFe1–xO3−δ as a Robust Redox Catalyst for CO2 Splitting and Methane Partial Oxidation
LaNixFe1–xO3−δ as a Robust Redox Catalyst for CO2 Splitting and Methane Partial Oxidation
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DOI：
10.1021/acs.energyfuels.1c02258
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发表时间：
2021-09
期刊：
影响因子：
5.3
通讯作者：
Sherafghan Iftikhar;Qiongqiong Jiang;Yunfei Gao;Junchen Liu;Haiming Gu;Luke M. Neal;Fanxing Li
中科院分区：
文献类型：
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作者：
Sherafghan Iftikhar;Qiongqiong Jiang;Yunfei Gao;Junchen Liu;Haiming Gu;Luke M. Neal;Fanxing Li
目前的研究报告LaNi0.5Fe0.5O3−δ作为一种稳定的氧化还原催化剂，用于在相对较低的温度（约700 °C）下进行CO2裂解和甲烷部分氧化。具体而言，制备并研究了具有九种不同组成（x= 0.05-0.5）的钙钛矿结构的LaNixFe 1-xO 3 −δ（LNF）。在评估的样品中，LaNi0.4Fe0.6O3−δ和LaNi0.5Fe0.5O3−δ显示出上级的氧化还原性能，CO2和甲烷转化率> 90%，合成气选择性>90%。独立的LNF也表现出与混合导电Ce0.85Gd0.1Cu0.05O2−δ（CGCO）促进的LNF相当的性能。LaNi0.5Fe0.5O3−δ的长期测试表明，氧化还原催化剂在重复的氧化还原循环中逐渐失去活性，平均500次循环，每次循环的活性损失约为0.02%。发现这种逐渐失活通过用空气深度氧化是可逆的。进一步的表征表明，活性的损失是由于缓慢积累的碳化铁（Fe 3C和Fe 5C 2）相，这不能有效地去除过程中的CO2裂解步骤。再氧化与空气中除去的碳化物相，通过固态反应与La 2 O3的氧化还原反应增加了Fe的可用性，并降低了La 2 O3的平均晶粒尺寸。周期性地再活化氧化还原催化剂，例如，每40个循环一次，显示出是高度有效的，如通过操作氧化还原催化剂超过900个累积循环同时保持令人满意的氧化还原性能所证实的。
The current study reports LaNi0.5Fe0.5O3−δas a robust redox catalyst for CO2splitting and methane partial oxidation at relatively low temperatures (∼700 °C) in the context of a hybrid redox process. Specifically, perovskite-structured LaNixFe1–xO3−δ(LNFs) with nine different compositions (x= 0.05–0.5) were prepared and investigated. Among the samples evaluated, LaNi0.4Fe0.6O3−δand LaNi0.5Fe0.5O3−δshowed superior redox performance, with ∼90% CO2and methane conversions and >90% syngas selectivity. The standalone LNFs also demonstrated performance comparable to that of LNF promoted by mixed conductive Ce0.85Gd0.1Cu0.05O2−δ(CGCO). Long-term testing of LaNi0.5Fe0.5O3−δindicated that the redox catalyst gradually loses its activity over repeated redox cycles, amounting to approximately 0.02% activity loss each cycle, averaged over 500 cycles. This gradual deactivation was found to be reversible by deep oxidation with air. Further characterizations indicated that the loss of activity resulted from a slow accumulation of iron carbide (Fe3C and Fe5C2) phases, which cannot be effectively removed during the CO2splitting step. Reoxidation with air removed the carbide phases, increased the availability of Fe for the redox reactions via solid-state reactions with La2O3, and decreased the average crystallite size of La2O3. Reactivating the redox catalyst periodically, e.g., once every 40 cycles, was shown to be highly effective, as confirmed by operating the redox catalyst over 900 cumulative cycles while maintaining satisfactory redox performance.