物理化学学报

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钾对CuSO4/TiO2脱硝催化剂的失活效应

于艳科1, 耿梦荞1, 魏德胜1, 何炽1,2,3   

  1. 1 西安交通大学能源与动力工程学院环境科学与工程系,西安 710049;
    2 西安交通大学动力工程多相流国家重点实验室,西安 710049;
    3 中国科学院大学挥发性有机物污染控制材料与技术国家工程实验室,北京 101408
  • 收稿日期:2022-06-22 修回日期:2022-07-12 录用日期:2022-07-13 发布日期:2022-07-18
  • 通讯作者: 何炽 E-mail:chi_he@xjtu.edu.cn
  • 基金资助:
    国家自然科学基金(21906127, 21876139, 21922606), 中国博士后科学基金(2021M692550), 王宽诚教育基金会和西安交通大学分析测试中心资助

Effect of Potassium on the Performance of a CuSO4/TiO2 Catalyst Used in the Selective Catalytic Reduction of NOx by NH3

Yanke Yu1, Mengqiao Geng1, Desheng Wei1, Chi He1,2,3   

  1. 1 Department of Environmental Science and Engineering, School of Energy and Power Engineering, Xi’an Jiaotong University, Xi’an 710049, China;
    2 State Key Laboratory of Multiphase Flow in Power Engineering, Xi'an Jiaotong University, Xi’an 710049, China;
    3 National Engineering Laboratory for VOCs Pollution Control Material & Technology, University of Chinese Academy of Sciences, Beijing 101408, China
  • Received:2022-06-22 Revised:2022-07-12 Accepted:2022-07-13 Published:2022-07-18
  • Contact: Chi He E-mail:chi_he@xjtu.edu.cn
  • Supported by:
    The project was supported by the National Natural Science Foundation of China (21906127, 21876139, 21922606), General Financial Grant from the China Postdoctoral Science Foundation (2021M692550), K.C. Wong Education Foundation and Instrumental Analysis Center of Xi’an Jiaotong University.

摘要: 为了减少碳排放,在世界各地兴建了越来越多的生物质电厂。钾元素是生物质电厂烟气中的一种典型元素并且可以引起脱硝催化剂的失活。具有优异抗SO2性能的CuSO4/TiO2催化剂被认为是一种有前景的非钒基脱硝催化剂。但是,钾对CuSO4/TiO2催化剂的影响仍不清楚。本文研究了钾对CuSO4/TiO2催化剂的影响并且与商业V2O5-WO3/TiO2(VWTi)催化剂作了比较,采用多种表征方法对催化剂样品进行了表征。钾可以引起CuSO4/TiO2和VWTi催化剂的失活,但是CuSO4/TiO2催化剂对钾的抵抗能力明显高于商业VWTi催化剂。钾会与CuSO4/TiO2催化剂中的CuSO4发生反应生成CuO和K2SO4。CuO的形成会引起催化剂上NOx转化率和N2选择性的下降。另外,钾还会与催化剂上的Brønsted酸性位(S-OH)结合从而阻碍NH3在催化剂表面的吸附。再者,高浓度的钾还会引起催化剂比表面积的下降。值得注意的是,丰富的酸性位和表面吸附氧含量应该是CuSO4/TiO2催化剂对钾具有较高抵抗力的原因。本工作的研究结果表明CuSO4/TiO2催化剂是一种适用于生物质电厂烟气脱硝的潜在催化剂。

关键词: NH3-SCR催化剂, 氮氧化物, Brønsted酸性位, 氧化铜, 生物质电厂

Abstract: Owing to its renewability, abundance, and low environmental impact, biomass is considered to be a viable eco-friendly fuel. Various biofuel-fired power plants have been built worldwide to reduce carbon emissions. Potassium (K) is a typical impurity in the flue gas from biofuel combustion that can deactivate the catalyst used in the selective catalytic reduction of NOx by ammonia (NH3-SCR). CuSO4/TiO2, with excellent sulfur dioxide tolerance, is thought to be a promising vanadium-free catalyst for NH3-SCR; however, the influence of K on the CuSO4/TiO2 catalyst is still unknown. Therefore, in this study, the effect of K on the NH3-SCR performance of CuSO4/TiO2 were investigated and compared with the effect on the performance of the commercial V2O5-WO3/TiO2 (VWTi) catalyst. K-poisoned catalysts were prepared via wet impregnation using potassium acetate as the K source. Nitrogen (N2) adsorption-desorption, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), NH3-temperature programmed desorption (NH3-TPD), H2-temperature programmed reduction (H2-TPR), and in situ diffuse reflectance infrared Fourier-transform spectroscopy (in situ DRIFTS) were used to characterize the prepared catalysts. The NOx conversion over CuSO4/TiO2 with 1.0% (w) K was 92.1% (at 350 °C), which was higher than the conversion (75.1%) achieved over the commercial VWTi catalyst with the same K content. The XRD, XPS, and H2-TPR results suggested that K reacted with the CuSO4 in the CuSO4/TiO2 catalyst to form CuO and K2SO4. The presence of CuO enhanced the oxidation of NH3 to N2O, NO, and NO2 during NH3-SCR, thereby decreasing the NOx conversion and N2 selectivity over CuSO4/TiO2. Moreover, based on the results from NH3-TPD and in situ DRIFTS of NH3 adsorption, it can be concluded that the Brønsted acid sites (S-OH) were poisoned by K, which restrained the adsorption of NH3 on CuSO4/TiO2. Additionally, the high K content altered the pore structure of the catalyst, leading to a decrease in the specific surface area. However, according to the in situ DRIFTS results, NH3-SCR over K-poisoned CuSO4/TiO2 still followed the Eley-Rideal mechanism: First, NH3 was adsorbed on the Lewis and Brønsted acid sites of the catalyst, and then gaseous NO and O2 reacted with the adsorbed NH3/NH4+ on the acid sites, resulting in the formation of N2 and H2O. Notably, the abundance of acid sites and surface-adsorbed oxygen species on CuSO4/TiO2 could be the main reason for its higher resistance to K-poisoning. In conclusion, our current findings suggested that CuSO4/TiO2 might be a suitable NH3-SCR catalyst for use in the flue gas streams from biofuel-fired power plants.

Key words: NH3-SCR catalysts, NOx, Brønsted acid sites, CuO, biofuel-fired power plants

MSC2000: 

  • O643