<br>歧化反应在利用甲烷还原 SO2 以灵活回收元素硫或硫化物中的作用,Environmental Science & Technology

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歧化反应在利用甲烷还原 SO2 以灵活回收元素硫或硫化物中的作用
Environmental Science & Technology ( IF 10.8 ) Pub Date : 2023-12-27 , DOI: 10.1021/acs.est.3c08714
Xiaoming Sun _{1,

2} , Wenjun Huang ₁ , Xiangyu Jia ₁ , Zhisong Liu ₁ , Xi Feng ₃ , Haomiao Xu ₁ , Zan Qu ₁ , Naiqiang Yan _{1,

2}

Affiliation

由于高能垒和SO ₂引起的催化剂中毒，用CH ₄还原SO ₂产生元素硫(S ₈ )或其他硫化物通常具有挑战性。在此，我们报道了由H ₂ S再循环引起的歧化反应(CR)显着加速了反应，改变了反应途径并使得能够灵活地将产物从S ₈调整为硫化物。结果表明，与直接还原（DR）所需的800℃相比，SO ₂在650℃的较低温度下即可完全还原为H ₂ S，有效消除了催化剂中毒。动力学速率常数显着提高，650 °C 时的 CR 值比 750 °C 时的 DR 高约 3 倍。此外，H ₂ S 的表观活化能从 128 kJ/mol 降低至 37 kJ/mol，从而改变了反应路线。该 CR 解决了与强大的硫氧键活化相关的挑战并增强了 CH ₄解离。在此过程中，具有Co促进剂的分散良好的层状MoS ₂微晶(CoMoS)充当活性物质。 H ₂ S促进歧化反应，将SO ₂还原成初生硫(S _x *)。随后，CH ₄在不存在SO ₂的情况下有效地激活CoMoS，形成H ₂ S。这将机制从DR中的Mars-van Krevelen (MvK)转变为CR中的连续Langmuir-Hinshelwood (LH)和MvK。此外，它还通过这种快速活化反应途径减轻硫酸化中毒。这种独特的歧化反应为硫资源的高效利用提供了新的策略。

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Roles of the Comproportionation Reaction in SO2 Reduction Using Methane for the Flexible Recovery of Elemental Sulfur or Sulfides

SO₂ reduction with CH₄ to produce elemental sulfur (S₈) or other sulfides is typically challenging due to high energy barriers and catalyst poisoning by SO₂. Herein, we report that a comproportionation reaction (CR) induced by H₂S recirculating significantly accelerates the reactions, altering reaction pathways and enabling flexible adjustment of the products from S₈ to sulfides. Results show that SO₂ can be fully reduced to H₂S at a lower temperature of 650 °C, compared to the 800 °C required for the direct reduction (DR), effectively eliminating catalyst poisoning. The kinetic rate constant is significantly improved, with CR at 650 °C exhibiting about 3-fold higher value than DR at 750 °C. Additionally, the apparent activation energy decreases from 128 to 37 kJ/mol with H₂S, altering the reaction route. This CR resolves the challenges related to robust sulfur–oxygen bond activation and enhances CH₄ dissociation. During the process, the well-dispersed lamellar MoS₂ crystallites with Co promoters (CoMoS) act as active species. H₂S facilitates the comproportionation reaction, reducing SO₂ to a nascent sulfur (S_x*). Subsequently, CH₄ efficiently activates CoMoS in the absence of SO₂, forming H₂S. This shifts the mechanism from Mars–van Krevelen (MvK) in DR to sequential Langmuir–Hinshelwood (L-H) and MvK in CR. Additionally, it mitigates sulfation poisoning through this rapid activation reaction pathway. This unique comproportionation reaction provides a novel strategy for efficient sulfur resource utilization.

更新日期：2023-12-27

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