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Enhancement of NO oxidation activity and SO2 resistance over LaMnO3+δ perovskites catalysts with metal substitution and acid treatment.

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Title: Enhancement of NO oxidation activity and SO2 resistance over LaMnO3+δ perovskites catalysts with metal substitution and acid treatment.
Authors: Lin, Fawei1 (AUTHOR), Shao, Jiaming1 (AUTHOR), Tang, Hairong1 (AUTHOR), Li, Yan1 (AUTHOR), Wang, Zhihua1 (AUTHOR) wangzh@zju.edu.cn, Chen, Guanyi1 (AUTHOR) chen@tju.edu.cn, Yuan, Dingkun1 (AUTHOR), Cen, Kefa1 (AUTHOR)
Source: Applied Surface Science. Jun2019, Vol. 479, p234-246. 13p.
Subjects: Metal catalysts, Catalytic oxidation, Oxidation, Flue gases, Toxicity testing, Perovskite
Abstract: Abstract NO x control by catalytic oxidation combined with wet absorption has been a promising technology for the flue gas treatment of industrial boiler and furnace. LaMnO 3+δ perovskites were investigated as catalysts for NO oxidation. The comparison between metal substitution of La and Mn cations was researched. The activity results indicated that La site substitution was more favorable for NO oxidation than Mn site substitution. LaCoMnO exhibited the highest activity in NO oxidation with maximum value of 83.74% at 250 °C. That value further increased to 89.96% after acid etching (LaCoMnO-A), and closely, such high value of 89.78% was achieved at 220 °C. The surface area was significantly improved by acid etching, i.e., from 47.0 m2/g to 212.0 m2/g, Tremendous changes in crystalline structure and morphology were taken place, i.e., perovskites phase disappeared and MnO 2 was detected instead; compact amorphous particle morphology was replaced by multiple layer structure. Even more, Mn4+ ions and oxygen vacancies accumulated on the surface were improved. Deservedly, the redox property was enhanced enormously, especially at low temperature. Subsequently, SO 2 poisoning tests were conducted at 250 °C under 20 ppm SO 2. Interestingly, no decrease was observed for LaCoMnO-A within 480-min SO 2 poisoning test, which was totally contrasted with the nearly complete deactivation results of LaCoMnO. In-situ DRIFTS measurements validated nitrate disappeared and replaced by sulfate formation on the catalyst surface. Merely, under low-concentration SO 2 atmosphere, the monodentate nitrate and bidentate nitrate were destroyed, while the free nitrates exhibited higher resistance. Overall, the acid etching improved the catalyst resistance to SO 2 , which may have the potential to apply in the flue gas treatment of low-sulfur and sulfur-free fuel fired boiler and furnace. Graphical abstract Unlabelled Image Highlights • LaMnO 3+δ perovskites catalysts were modified by metal substitution and acid etching. • Metal substitution in La site was more favorable for NO oxidation. • Acid etching treatment improved NO oxidation activity significantly. • High resistance to low-concentration SO 2 was achieved by LaMnO 3+δ after acid etching. [ABSTRACT FROM AUTHOR]
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Abstract:Abstract NO x control by catalytic oxidation combined with wet absorption has been a promising technology for the flue gas treatment of industrial boiler and furnace. LaMnO 3+δ perovskites were investigated as catalysts for NO oxidation. The comparison between metal substitution of La and Mn cations was researched. The activity results indicated that La site substitution was more favorable for NO oxidation than Mn site substitution. LaCoMnO exhibited the highest activity in NO oxidation with maximum value of 83.74% at 250 °C. That value further increased to 89.96% after acid etching (LaCoMnO-A), and closely, such high value of 89.78% was achieved at 220 °C. The surface area was significantly improved by acid etching, i.e., from 47.0 m2/g to 212.0 m2/g, Tremendous changes in crystalline structure and morphology were taken place, i.e., perovskites phase disappeared and MnO 2 was detected instead; compact amorphous particle morphology was replaced by multiple layer structure. Even more, Mn4+ ions and oxygen vacancies accumulated on the surface were improved. Deservedly, the redox property was enhanced enormously, especially at low temperature. Subsequently, SO 2 poisoning tests were conducted at 250 °C under 20 ppm SO 2. Interestingly, no decrease was observed for LaCoMnO-A within 480-min SO 2 poisoning test, which was totally contrasted with the nearly complete deactivation results of LaCoMnO. In-situ DRIFTS measurements validated nitrate disappeared and replaced by sulfate formation on the catalyst surface. Merely, under low-concentration SO 2 atmosphere, the monodentate nitrate and bidentate nitrate were destroyed, while the free nitrates exhibited higher resistance. Overall, the acid etching improved the catalyst resistance to SO 2 , which may have the potential to apply in the flue gas treatment of low-sulfur and sulfur-free fuel fired boiler and furnace. Graphical abstract Unlabelled Image Highlights • LaMnO 3+δ perovskites catalysts were modified by metal substitution and acid etching. • Metal substitution in La site was more favorable for NO oxidation. • Acid etching treatment improved NO oxidation activity significantly. • High resistance to low-concentration SO 2 was achieved by LaMnO 3+δ after acid etching. [ABSTRACT FROM AUTHOR]
ISSN:01694332
DOI:10.1016/j.apsusc.2019.02.104