Abstract: A novel Fe-based oxygen carrier/coal ash was proposed for CO oxidation in CLC system in this paper.Its activity and thermal stability as well as the synergistic effect between oxygen carrier and coal ash were studied by TGA and combustion experiments in a small fluidized bed and density functional theory calculations also performed.It is found that the novel oxygen carrier is more active for CO oxidation in CLC system,because of greater porosity and synergistic effect between them.At 850℃ and with 10.0%(mass) foamer,the maximum conversion is much higher for the novel Fe-based ash oxygen carrier(84.9%)than for Fe₂O₃/Al₂O₃(54.3%),and the former is of preferable thermal stability in 30 cycles test.The activity of novel oxygen carrier is influenced significantly by the content of foamer and reaction conditions.Suitable foamer content(about 10%(mass))is favorable,whereas high reaction temperature causes its sintering. Furthermore,the effect of interfacial interaction and electronic properties related to the synergistic effect between them on CO oxidation were studied by density functional theory(DFT).The calculation results indicate that total charge population in the Fe₂O₃ particles is positive due to interfacial charge transfer between coal ash and Fe₂O₃,which could be favorable for reaction of CO and oxygen carrier.Synergistic effect between coal ash and Fe₂O₃ could cause a decrease of their frontier orbital energy difference,hence promote reactions between CO and Fe₂O₃.

Key words: CLC, Fe-based oxygen carrier, coal ash, density functional theory(DFT)

摘要： 提出了一种以粉煤灰为载体制备的新型铁基载氧体。采用同步热重分析仪、小型流化床以及DFT分别研究了新型载氧体的活性与热稳定性,发泡剂含量与反应温度以及粉煤灰主要组分之间的协同作用对新型载氧体性能的影响。研究结果表明,新型载氧体在以CO为燃料的化学链系统中具有较高的活性;新型载氧体较大的孔隙率以及粉煤灰多组分间的协同作用促使850℃下发泡剂含量为10.0%(质量)的新型铁基载氧体的最大转化率(84.9%)比Fe₂O₃/Al₂O₃的最大转化率(54.3%)高30%,且新型铁基载氧体在30个循环测试中表现出良好的热稳定性。载体制备采用的发泡剂含量以及反应温度对新型铁基载氧体性能影响很大,适当的发泡剂含量(约10%(质量))可提高新型载氧体性能。此外,高温下会造成载氧体的烧结现象。最后,采用密度泛函理论(DFT)研究了粉煤灰与载氧体之间的界面作用以及协同氧化CO的电子特性。计算结果表明,粉煤灰和Fe₂O₃之间的界面电荷转移使Fe₂O₃为电正性,促使CO在表面的相互作用,载体和活性组分之间的协同作用降低了载氧体与CO前线轨道能量差,进而促进了CO与Fe₂O₃的反应。

关键词: 化学链燃烧, 铁基载氧体, 粉煤灰, 密度泛函理论(DFT)