硫化氢对钴改性活性焦脱除煤气中汞的影响机理

doi:10.11944/j.issn.1000-0518.2018.12.180016

摘要/Abstract

摘要：

采用等体积浸渍煅烧法制备钴改性活性焦(Co-AC),并采用BET、XRD等分析手段进行表征。利用固定床吸附实验台,研究了模拟煤气(N₂、H₂、CO、H₂S)气氛下汞的吸附特性,重点关注H₂S对汞吸附的影响。结果表明,5%负载量的Co-AC在120 ℃和H₂S作用下具有优异的脱汞能力,2 h内平均脱汞效率高达97.8%。此外基于密度泛函理论,首先计算了H₂S、HS及S在Co₃O₄(110)表面的吸附能及键长,通过比较H—S键键长的变化得出H₂S会逐步解离成HS与S,然后将优化后的S-Co₃O₄(110)作为Hg的吸附基底,研究其吸附特性,得出Hg与S反应生成稳定的HgS,吸附能为-3.503 eV,证明了汞的吸附遵循Eley-Rideal机制。 Co-AC吸附剂在高温下脱汞性能受到极大的抑制,因为随吸附温度升高,表面活性硫的减少及硫和汞的反应平衡常数下降显著,导致汞的脱除能力下降。本文采用了实验加模拟的手段,探明了H₂S存在时Hg⁰在钴基吸附剂表面的反应机理,为协同脱除煤气中的H₂S和Hg⁰提供了理论指导。

关键词: 钴改性, 活性焦, 脱汞效率, 密度泛函理论, H₂S

Abstract:

Activated coke modified with cobalt(Co-AC) were prepared through impregnation and high temperature calcination method, and then characterized by BET(Brunauer-Emmett-Teller), XRD(X-ray diffraction) analysis. The adsorption of gas-phase elemental mercury by Co-AC under nitrogen and simulated syngas(N₂, H₂, CO, H₂S) was studied on a bench-scale fixed-bed apparatus and focus on the influence of H₂S. The results show that 5%Co-AC exhibits excellent Hg⁰ removal capacity at 120 ℃ and 97.8% of Hg⁰ can be removed in the presence of H₂S. In addition, based on the density functional theory, the adsorption energy and bond length of H₂S, HS and S on Co₃O₄ (110) surface were calculated. Firstly, H₂S will dissociate into HS and S in turn by comparing the bond length of H—S. Secondly the adsorption characteristic of Hg was calculated on S-Co₃O₄(110 ). The results indicate that Hg reacts with S to form a stable HgS with an adsorption energy of -3.503 eV and the adsorption of Hg follows Eley-Rideal mechanism.With an elevated temperature, mercury removal is suppressed, because the amount of active sulfurs on the surface decreases and the interaction between Hg and S is weakened. The reaction mechanism of Hg⁰ removal on the surface of cobalt-based adsorbents in the presence of H₂S was proved. This provides a theoretical guidance for synergistic removal of H₂S and Hg⁰ in coal gas.

Key words: cobalt modification, activated coke, removal efficiency, denstiy functional theory, H₂S

茅珏榛, 周劲松, 李学谦, 周启昕, 曹辉. 硫化氢对钴改性活性焦脱除煤气中汞的影响机理[J]. 应用化学, 2018, 35(12): 1497-1506.

MAO Juezhen, ZHOU Jinsong, LI Xueqian, ZHOU Qixin, CAO Hui. Mechanism of Mercury Removal in Syngas by Co-modified Activated Coke with H₂S[J]. Chinese Journal of Applied Chemistry, 2018, 35(12): 1497-1506.

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