Effects of SO2 on the low temperature selective catalytic reduction of NO by NH3 over CeO2-V2O5-WO3/TiO2 catalysts

doi:10.1007/s11783-017-0926-6

Front. Environ. Sci. Eng.

2017, Vol. 11

Issue (4) : 4 https://doi.org/10.1007/s11783-017-0926-6

RESEARCH ARTICLE

Effects of SO₂ on the low temperature selective catalytic reduction of NO by NH₃ over CeO₂-V₂O₅-WO₃/TiO₂ catalysts

Quanming Liang¹, Jian Li^1,²(

), Hong He^1,²(

), Wenjun Liang^1,², Tiejun Zhang¹, Xing Fan¹

¹. Key Laboratory of Beijing on Regional Air Pollution Control, Beijing University of Technology, Beijing 100124, China
². Beijing Key Laboratory for Green Catalysis and Separation, Beijing University of Technology, Beijing 100124, China

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Abstract

CeO₂ improved the De-NO_x activity and sulfur resistance of catalysts.

The De-NO_x activity of 3% CeO₂ -VWT catalyst reached 89.9 % at 140°C.

CeO₂ promoted the oxidation of NO to NO₂ and inspired the fast SCR reaction.

Active components content and BET decreased slightly after entering SO₂.

The largest loss rate was 0.024%/°C at 380°C–390°C in poisoned catalyst.

The CeO₂-V₂O₅-WO₃/TiO₂ (CeO₂-VWT) catalysts were prepared by one-step and two-step impregnation methods. The effects of different loading of CeO₂ and different preparation methods on De-NO_x activity of catalysts had been investigated. CeO₂ helped to improve the De-NO_x activity and sulfur resistance. The optimal loading of CeO₂ was 3% with the De-NO_x efficiency reached 89.9% at 140°C. The results showed that the De-NO_x activity of 3% CeO₂-VWT catalysts by one-step method was the same as two-step method basically and reached the level of industrial applications, the N₂ selectivity of catalysts was more than 99.2% between 110°C and 320°C. In addition, CeO₂ promoted the oxidation of NO to NO₂, which adsorbed on the Lewis acid site (V⁵⁺═O) to form V⁵⁺═NO₃ and inspired the fast SCR reaction. Not only the thermal stability but also the De-NO_x activity of catalysts decreased with excess CeO₂ competed with V₂O₅. Characterizations of catalysts were carried out by XRF, BET, XRD, TG and FT-IR. BET showed that the specific surface area of catalysts decreased with the loading of CeO₂ increased, the active components content and specific surface area of catalysts decreased slightly after entering SO₂. Ammonium sulfate species were formed in poisoned catalyst which had been investigated by XRF, BET, TG and FT-IR. The largest loss rate of weight fraction was 0.024%·°C⁻¹ at 380°C–390°C, which was in accordance with the decomposition temperature of NH₄HSO₄ and (NH₄)₂SO₄.

Keywords Low temperature SCR De-NO_x activity Sulfur resistance Ammonium sulfate

Corresponding Author(s): Jian Li,Hong He

Issue Date: 13 April 2017

Cite this article:

Quanming Liang,Jian Li,Hong He, et al. Effects of SO₂ on the low temperature selective catalytic reduction of NO by NH₃ over CeO₂-V₂O₅-WO₃/TiO₂ catalysts[J]. Front. Environ. Sci. Eng., 2017, 11(4): 4.

URL:

https://academic.hep.com.cn/fese/EN/10.1007/s11783-017-0926-6
https://academic.hep.com.cn/fese/EN/Y2017/V11/I4/4

Fig.1 De-NO_x activity of CeO₂-VWT catalysts: (a) CeO₂-VWT catalysts by one-step, (b) 3% CeO₂-VWT catalysts by one-step and two-step, (c) effects of 300 ppm SO₂ at 180℃

Reaction conditions: [NH₃] = [NO] = 700 ppm, [SO₂] = 300 ppm(when needed), [O₂] = 5%, N₂ balance, GHSV= 27000 h⁻¹

Tab.1 Trend lines about effects of SO₂ on De-NO_x activity of CeO₂-VWT catalysts at 180℃

Tab.2 The components of CeO₂-VWT catalysts by X-ray fluorescence patterns

Tab.3 Specific surface area of CeO₂-VWT catalysts

Fig.2 Characterization analysis of CeO₂-VWT catalysts: (a) X-ray diffraction patterns: (1) 0% CeO₂-VWT, (2) 1% CeO₂-VWT, (3) 2% CeO₂-VWT, (4) 3% CeO₂-VWT, (5) 4% CeO₂-VWT, (6) 7% CeO₂-VWT, (7) 0% CeO₂-VWT-SO₂, (8) 3% CeO₂-VWT-SO₂; (b) FT-IR spectra: (1) 3% CeO₂-VWT, (2) 3% CeO₂-VWT-SO₂

Fig.3 The circulation system between active components and activated oxygen in catalysts

Tab.4 The weight loss fraction of CeO₂-VWT catalysts at different stages

Fig.4 TG analysis of CeO₂-VWT catalysts: (1) 0% CeO₂-VWT, (2) 3% CeO₂-VWT, (3) 7% CeO₂-VWT, (4) 3% CeO₂-VWT-SO₂, (5) the weight fraction loss rate of 0% CeO₂-VWT catalyst, (6) the weight fraction loss rate of 3% CeO₂-VWT catalyst, (7) the weight fraction loss rate of 7% CeO₂-VWT catalyst, (8) the weight fraction loss rate of 3% CeO₂-VWT-SO₂ catalyst

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