Catalytic oxidation of elemental mercury over CuO modified commercial SCR catalyst

doi:10.16085/j.issn.1000-6613.2017-2428

Abstract

Abstract: Efficient oxidation of elemental mercury (Hg⁰) in coal-fired flue gas is the key technology to control the mercury emission in coal-fired power plants. To improve the Hg⁰ oxidation activity of the traditional SCR catalyst, the CuO-SCR catalysts were prepared by an improved impregnation method and then were used for simultaneous NO removal and Hg⁰ oxidation to evaluate the catalytic performance. BET, XRD and XPS were used to characterize the catalysts. The results showed that the Hg⁰ oxidation activity and low-temperature NO removal activity of the commercial SCR catalyst were significantly improved by the addition of CuO. The presence of NO and NH₃ could inhibit the Hg⁰ oxidation activity over CuO-SCR catalyst at 200-400℃, and the effect was enhanced with increased temperature and NH₃ content. At 350℃, the Hg⁰ oxidation activity over CuO-SCR catalyst was remarkably enhanced with the decrease of GHSV under simulated coal-fired flue gas, and the inhibiting effect of NH₃ was also diminished. The characterization results suggested that there could be a redox cycle of V⁴⁺+Cu²⁺?V⁵⁺+Cu⁺ in the CuO-SCR catalyst which enhanced the catalytic activity. Moreover, the Hg⁰ oxidation on the CuO-SCR catalyst agreed with the Mars-Maessen mechanism.

Key words: selective catalytic reduction, catalyst, Hg⁰ oxidation, simultaneous removal, flue gas

摘要： 燃煤烟气中单质汞（Hg⁰）的高效氧化是提高燃煤电厂脱汞效率的关键，为提高传统选择性催化还原（SCR）催化剂氧化Hg⁰的性能，本文采用溶液浸渍法制备了CuO-SCR催化剂，在固定床反应装置上考察了其脱硝协同氧化单质汞性能，并借助BET、XRD和XPS等分析技术对催化剂进行表征。结果表明，CuO的掺杂显著提高了商用SCR催化剂的Hg⁰氧化性能和低温脱硝活性；在200~400℃内，随着反应温度升高和NO+NH₃浓度增大，NH₃对CuO-SCR催化剂的Hg⁰氧化性能抑制作用加强；在350℃、模拟燃煤烟气条件下，随着空速比的减小，催化剂的Hg⁰氧化性能显著提高，NH₃对Hg⁰氧化的抑制作用明显减弱。催化剂表征结果表明，CuO-SCR催化剂表面存在氧化还原反应V⁴⁺+Cu²⁺?V⁵⁺+Cu⁺，增强了催化剂的催化活性。Hg⁰在CuO-SCR催化剂表面的氧化过程遵循Mars-Maessen机制，能够有效增强催化剂的Hg⁰氧化性能。

关键词: 选择性催化还原, 催化剂, Hg⁰氧化, 协同脱除, 烟道气

CLC Number:

TQ032

CHEN Chuanmin, JIA Wenbo, LIU Songtao, CAO Yue. Catalytic oxidation of elemental mercury over CuO modified commercial SCR catalyst[J]. Chemical Industry and Engineering Progress, 2018, 37(10): 3903-3910.

陈传敏, 贾文波, 刘松涛, 曹悦. CuO改性商用选择性催化还原催化剂催化氧化单质汞性能[J]. 化工进展, 2018, 37(10): 3903-3910.

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