化学链燃烧技术是一种新型的近“零碳”排放燃烧技术,载氧体在化学链燃烧反应过程中发挥着载氧和传热的双重作用。以活性催化组分为载体,通过调谐微观结构提高Fe基载氧体的反应性能是目前化学链领域的研究热点之一。基于密度泛函理论,以CeO2为活性催化载体,对Fe基载氧体进行催化调谐。通过优化构建组合物模型,系统分析了组合物模型中Fe2O3团簇不同点位吸附CO的态密度、吸附能、差分电荷密度和活化能等电子结构特性参数。研究结果表明,Fe2O3团簇的电子向CeO2(111)表面转移,Fe2O3团簇的吸附能为-3.92eV,Fe2O3团簇与CeO2(111)表面稳定结合;态密度(DOS)分析发现负载后的Fe2O3团簇p和d轨道在-8~0eV电子向费米能级方向迁移,表明吸附作用增强。Fe2O3团簇p和d轨道中电子减少,现存电子向高能级跃迁,Fe2O3团簇电子活性增强,CO分子在Fe2O3/CeO2复合载氧体的Fe2O3团簇3个吸附位反应的活化能均降低。此外,CeO2(111)增强了CO在Fe2O3团簇Fe顶位的吸附作用,吸附能由-0.33eV增至-1.78eV;同时,削弱了在O顶位的过强吸附作用,吸附能由-2.69eV降至-2.32eV,有利于后期CO2分子脱离Fe2O3团簇表面,从而有效调谐Fe2O3团簇整体对CO的吸附效果,为Fe基载氧体的设计制备和优化调谐提供理论指导。

Chemical looping combustion technology is a new type of combustion technology with near zero carbon emission. Oxygen carrierplays the dual role of oxygen carrying and heat transfer in chemical looping combustion reaction. Improving the reaction performance of Febased oxygen carrier by tuning microstructure has been one of research focuses in the field of chemical looping technology. In this study,CeO2 was used as the active catalytic support to catalyze and tune of Fe-based oxygen carrier based on density functional theory. The electronic structural characteristic parameters of CO adsorption, such as state density, adsorption energy, differential charge density, and activation energy at the different sites of Fe2O3 clusters, were systematically analyzed by optimizing the constructed composite model. The results show that the electrons of Fe2O3 clusters are transferred to CeO2(111) surface, and the binding energy is -3.92 eV, and Fe2O3 clusters can be bonded on the CeO2(111) surface stably. Density of states (DOS) analysis show that the p and d orbitals of Fe2O3 clusters after loading migrate to the Fermi level at -8-0 eV, indicating that the adsorption is enhanced. The electrons in the p and d orbitals ofFe2O3 clusters decrease, the existing electrons transition to higher energy levels, and the electronic activity of Fe2O3 clusters increases.Therefore, the activation energies of CO molecules at three adsorption sites of Fe2O3 clusters in Fe2O3 / CeO2 complex oxygen carrier decrease. Furthermore, CeO2(111) enhances the adsorption of CO at the Fe top of Fe2O3 clusters, increasing the adsorption energy from-0.33 eV to -1.78 eV. Then the over-strong adsorption at the O top is weakened, and the adsorption energy is reduced from -2.69 eVto -2.32 eV, this also facilitates the subsequent release of CO2 molecules from the surface of Fe2O3 clusters, thus effectively tuning theoverall adsorption effect of Fe2O3 clusters on CO. It provides theoretical guidance for the design, preparation, and optimal tuning ofFe-based oxygen carrier.

0 引言

1 计算模型及方法

   1.1 计算模型

   1.2 计算方法

   1.3 模型建立

2 结果与讨论

   2.1 CO在Fe2O3团簇表面吸附的机理

   2.2 CO在纯Fe2O3团簇表面的反应路径

   2.3 Fe2O3团簇负载CeO2(111)表面后的微观结构特性

   2.4 CO的吸附及电荷差分密度分析

   2.5 CO在Fe2O3/CeO2组合物模型表面的反应路径

3 结论