Producing elemental sulfur from SO2 by calcium loaded activated coke: Enhanced activity and selectivity
Producing elemental sulfur from SO2 by calcium loaded activated coke: Enhanced activity and selectivity
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通过负载钙的活性焦从 SO2 生产元素硫：增强活性和选择性
DOI：
10.1016/j.cej.2020.126022
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发表时间：
2020-12-01
影响因子：
15.1
通讯作者：
Liu, Hui
中科院分区：
文献类型：
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作者：
Pi, Xinxin;Sun, Fei;Liu, Hui
SO2碳热还原是将SO2转化为单质硫的一种很有前途的方法，但如何同时提高反应活性和选择性是长期的挑战。在这项工作中，我们展示了一种有效的方法来提高活性焦炭（AC）的活性和选择性SO2碳热还原通过可控负载催化Ca种。采用简单的超声辅助液相浸渍法制备了载钙活性炭，通过调整CaCl2的含量可以优化载钙活性炭的孔隙结构和CaCl2的分布。动态实验表明，与纯AC相比，cacl2负载的AC对SO2的去除率更高，表明Ca负载对SO2碳热还原活性有促进作用。根据随机孔隙模型（Random Pore Model， RPM）计算的动力学参数，cacl2负载活性炭活性的增强是由于活化能的降低。通过计算和关联反应物和反应产物的消耗量，负载30 wt% CaCl2的AC可以达到创纪录的80%的单质硫生产选择性。化学环境研究和密度泛函理论（DFT）计算进一步表明，载钙AC中的C-O- ca结构可以削弱反应中间体中的C-O键，从而降低O转移所需的能量，使SO2还原成为可能。此外，我们还评估了催化剂CaCl2的可回收性，证明CaCl2易于回收和再循环。本研究为提高SO2碳热还原的反应性和选择性提供了一种简便的策略，在烟气脱硫中具有很大的应用潜力。
SO2 carbothermal reduction is one of the promising strategies to convert SO2 to elemental sulfur, while the long-term challenge is to simultaneously improve the reactivity and selectivity. In this work, we demonstrate an effective approach for enhancing both the activity and selectivity of activated coke (AC) for SO2 carbothermal reduction by controllably loading catalytic Ca species. Ca-loaded ACs were prepared via a simple ultrasound assisted liquid phase impregnation method, in which the pore structure as well as CaCl2 distribution in Ca-loaded ACs can be optimized by tuning CaCl2 loading content. Dynamic experiments show that CaCl2-loaded ACs exhibit much higher SO2 removal rates as compared with pure AC, indicating the promoting role of Ca loading in SO2 carbothermal reduction activity. Such enhanced activity of CaCl2-loaded ACs is attributed to the decrease of activation energy according to the kinetic parameters calculated from Random Pore Model (RPM). By calculating and correlating the amounts of consumed reactants and reaction products, AC loaded with 30- wt% CaCl2 can achieve a record-high elemental sulfur production selectivity of 80%, which should be contributed by both the reactions of SO2 + C -> CO2 + S and 2CO + SO2 -> 2CO(2) + S. Chemical environment investigations and density functional theory (DFT) calculations further demonstrate that the C-O-Ca structure in Ca-loaded AC can weaken the C-O bond in reaction intermediates and thereby reduce the energy needed for O transfer, making SO2 reduction feasible to occur. In addition, we also evaluate the recyclability of catalyst CaCl2 that is proven to be easily recovered and recirculated. This work provides a facile strategy to improve the reactivity and selectivity for SO2 carbothermal reduction, holding great application potentials in flue gas desulfurization.