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 → 2CO₂ + 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.

SO ₂碳热还原是将SO ₂转化为元素硫的有前途的策略之一，而长期的挑战是同时提高反应性和选择性。在这项工作中，我们演示了通过可控制地加载催化性Ca来增强SO ₂碳热还原活性焦（AC）的活性和选择性的有效方法。通过简单的超声辅助液相浸渍法制备Ca负载的AC ，其中可通过调整CaCl _2的负载量来优化Ca负载的AC中的孔结构以及CaCl _2的分布。动态实验表明，CaCl ₂负载的AC与纯AC相比，具有更高的SO ₂去除率，表明Ca负载在SO ₂碳热还原活性中的促进作用。加载CaCl _2的AC的这种增强的活性归因于根据随机孔模型（RPM）计算出的动力学参数，活化能的降低。通过计算和关联消耗的反应物和反应产物的量，负载了30 wt％CaCl _2的AC可以达到创纪录的80％的单质硫生产选择性，这应该由SO ₂  + C→ CO ₂  + S和2CO + SO ₂  →2CO ₂ + S.化学环境研究和密度泛函理论（DFT）计算进一步证明，载有Ca的AC中的CO-Ca结构可以削弱反应中间体中的CO键，从而减少O转移所需的能量，从而使SO ₂还原可行发生。此外，我们还评估了被证明易于回收和再循环的催化剂CaCl ₂的可回收性。这项工作提供了一种提高SO ₂碳热还原反应性和选择性的简便策略，在烟气脱硫中具有巨大的应用潜力。