烧结烟气中Zn对V2O5−WO3/TiO2催化剂脱除NOx和二噁英性能的影响

丁龙; 钱立新; 杨涛; 张洪亮; 余正伟; 张晓霞; 龙红明

doi:10.13374/j.issn2095-9389.2020.10.08.001

烧结烟气中Zn对V₂O₅−WO₃/TiO₂催化剂脱除NO_x和二噁英性能的影响

doi: 10.13374/j.issn2095-9389.2020.10.08.001

丁龙¹,
钱立新¹,
杨涛¹,
张洪亮^{1, 2},
余正伟²,
张晓霞²,
龙红明^{1, 2, ,}

1.
安徽工业大学冶金工程学院，马鞍山 243032
2.
冶金工程与资源综合利用安徽省重点实验室，马鞍山 243002

基金项目: 国家自然科学基金资助面上项目（51674002）；国家自然科学基金资助青年项目（51704009）

详细信息

通讯作者:
E-mail：yaflhm@126.com

中图分类号: O643.3
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出版历程
- 收稿日期: 2020-10-08
- 网络出版日期: 2020-11-26
- 刊出日期: 2021-08-25

Influence of Zn in the iron ore sintering flue gas on the removal of NO_x and dioxins by V₂O₅–WO₃/TiO₂ catalyst

1.
School of Metallurgical Engineering, Anhui University of Technology, Ma’anshan 243032, China
2.
Anhui Province Key Laboratory of Metallurgy Engineering & Resources Recycling, Ma’anshan 243002, China

More Information

Corresponding author: E-mail: yaflhm@126.com

摘要

摘要: V₂O₅−WO₃/TiO₂（VWTi）催化剂可以同时脱除铁矿烧结烟气中的NO_x和二噁英，但复杂的烟气成分会导致催化剂失活。本文采用浸渍法对VWTi 催化剂进行ZnCl₂、ZnO和ZnSO₄中毒实验。模拟烧结烟气条件，研究了在VWTi催化剂表面负载不同形态Zn对其同时脱除NO_x和二噁英（以氯苯作为模拟物）性能的影响，分析了中毒前后催化剂表面活性物质的理化性质，并对中毒催化剂开展了再生实验。结果表明：不同Zn物种对VWTi催化剂同时脱除NO_x和氯苯（CB）均具有失活作用。Zn物种会引起催化剂表面颗粒轻微团聚，表面酸性位点数量减少，表面V的还原性减弱，表面化学吸附氧比例，以及V⁵⁺和V⁴⁺的物质的量比值降低。再生实验结果表明：酸洗可以在一定程度上恢复中毒催化剂的催化活性，但水洗不能恢复中毒催化剂的活性。研究发现Zn盐中毒作用机理为：Zn²⁺与催化剂表面酸性位点V=O和V−OH反应形成V−O−Zn，对NH₃与CB的吸附产生不利影响，造成催化剂中毒失活，ZnSO₄中的${\rm{SO}}_4^{2-} $可以为NH₃和CB的吸附转化提供新的酸性位点，减轻中毒效果，ZnCl₂中的Cl⁻会在反应后产生副产物HCl，造成催化剂表面更多活性位点中毒，加深中毒效果。
- V₂O₅–WO₃/TiO₂ /
- Zn物种 /
- 中毒 /
- NO_x /
- 二噁英
Abstract: Iron ore sintering is a process in which fuel, flux, and iron ore powders are mixed and sintered into a block under incomplete melting conditions. The flue gas from iron ore sintering process is one of the largest sources of nitrogen oxide (NO_x) and dioxin emissions in industries. The V₂O₅–WO₃/TiO₂ (VWTi) catalyst can simultaneously remove NO_x and dioxins, but the presence of the complex flue gas results in the deactivation of the catalysts. In response to this challenge, this study carried out experiments for ZnCl₂, ZnO, and ZnSO₄ poisoning over the VWTi catalyst via wet impregnation method. The effects of the different Zn species on the simultaneous removal of NO_x and dioxins (chlorobenzene was used as the simulant for dioxins) by the VWTi catalyst were studied under simulated conditions of the iron ore sintering flue gas. The surface physicochemical properties of the fresh and poisoned catalysts were characterized to reveal the deactivation mechanism, and the regeneration experiments of the poisoned catalysts were investigated. Results showed that deactivation through catalytic denitrification and chlorobenzene (CB) catalytic degradation processes could be observed in different Zn-containing catalysts. The poisoning effect was more obvious with the increase of Zn content, and the effects of deactivation were as follows: ZnCl₂>ZnO>ZnSO₄. Results from physical and chemical analyses indicated that Zn species had a significant influence on the chemical environment of the active substances on the surface of the catalysts. Zn species caused a slight agglomeration of particles on the surface of the catalysts, a decrease in the number of surface acid sites, a reduction in the reducibility of surface V species, and a decrease in the chemisorbed oxygen ratio and the molar ratio of n(V⁵⁺)/n(V⁴⁺). The regeneration experiments confirmed that employing the dilute sulfuric acid solution washing method was effective for recovering the catalytic activity, whereas the water washing method failed to restore the catalytic activity. The mechanism of Zn salt poisoning is as follows: Zn²⁺ reacts with the acid sites V=O and V−OH on the surface of the catalyst to form V−O−Zn, which adversely affects the adsorption of NH₃ and CB, resulting in the catalyst poisoning and deactivation. The ${\rm{SO}}_4^{2-} $ in ZnSO₄ provides a new acidic site for the adsorption and transformation of NH₃ and CB alleviating the poisoning effect. The Cl⁻ in ZnCl₂ produces HCl as a by-product after the reaction, resulting in more active sites poisoning on the surface of the catalyst and deepening the poisoning effect.
- V₂O₅–WO₃/TiO₂ /
- Zn species /
- poisoning /
- NO_x /
- dioxin

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图 1 催化剂活性测试设备图

Figure 1. Schematic of the equipment for testing catalytic activity

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图 2 新鲜催化剂与Zn²⁺中毒催化剂的脱硝活性（a）和CB降解率（b）

Figure 2. Denitrification (a) and chlorobenzene degradation (b) of activity of fresh and Zn²⁺-poisoned catalysts

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图 3 新鲜催化剂和Zn²⁺中毒催化剂XRD图谱

Figure 3. X-ray diffraction spectra of fresh and Zn²⁺-poisoned catalysts

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图 4 新鲜催化剂和Zn²⁺中毒催化剂N₂吸附曲线

Figure 4. N₂ adsorption curves of fresh and Zn²⁺-poisoned catalysts

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图 5 （a）Fresh catalyst，（b）ZC2，（c）ZO2 and （d）ZS2 的扫描电镜图谱

Figure 5. Scanning electron microscopy images of (a) fresh (b) ZC2, (c) ZO2, and (d) ZS2 catalysts

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图 6 新鲜催化剂和Zn²⁺中毒催化剂NH₃−TPD图谱

Figure 6. NH₃−TPD profiles of fresh and Zn²⁺-poisoned catalysts

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图 7 新鲜催化剂和Zn²⁺中毒催化剂H₂−TPR图谱

Figure 7. H₂−TPR profiles of fresh and Zn²⁺−poisoned catalysts

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图 8 不同催化剂O1s XPS图谱

Figure 8. X-ray photoelectron spectroscopy (XPS) spectra of O1s in different catalysts

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图 9 不同催化剂V2p_3/2 的XPS图谱

Figure 9. XPS spectra of V2p_3/2 in different catalysts

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图 10 新鲜催化剂和Zn²⁺中毒催化剂拉曼光谱图

Figure 10. Raman spectra of fresh and Zn²⁺-poisoned catalysts

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图 11 再生催化剂脱硝（a）和CB降解活性（b）

Figure 11. Denitrification activity (a) and CB degradation activity (b) of the regenerated catalysts

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图 12 WVTi催化剂 ZnO、ZnCl₂ 和 ZnSO₄中毒机理图

Figure 12. Schematic of the mechanism of poisoning of the WVTi catalyst by ZnO, ZnCl₂, and ZnSO₄

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表 1 新鲜催化剂和Zn²⁺中毒催化剂的BET表面积、孔容积和孔径

Table 1. Brunauer–Emmett–Teller surface area, pore volume, and pore size of fresh and Zn²⁺-poisoned catalysts

Samples	Surface area / (m²·g⁻¹)	Pore volume / (cm³·g⁻¹)	Pore size / nm
Fresh	38.25	0.185	19.38
ZC2	37.35	0.179	19.19
ZO2	37.44	0.181	19.39
ZS2	33.26	0.172	20.45

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表 2 新鲜催化剂和Zn²⁺中毒催化剂V XPS结果

Table 2. X-ray photoelectron spectroscopy results of V in fresh and Zn²⁺-poisoned catalysts

V2p_3/2	Fresh		ZC2		ZO2		ZS2
V2p_3/2	E_bv/eV	ω/%	E_bv/eV	ω/%	E_bv/eV	ω/%	E_bv/eV	ω/%
V³⁺	515.3	6.22	515.4	8.25	515.2	7.14	515.4	5.88
V⁴⁺	516.5	31.56	516.5	40.36	516.5	38.09	516.4	35.29
V⁵⁺	517.4	62.21	517.2	51.37	517.3	54.76	517.1	58.82
V⁵⁺/V⁴⁺	1.97		1.27		1.43		1.67

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表 3 中毒催化剂再生前后XRF结果

Table 3. X-ray fluorescence results of the poisoned catalysts, before and after regeneration %

Samples	Mass content of different elements/%
Samples	Ti	Si	Al	W	S	V	Ca	Zn
Fresh	42.43	6.11	2.00	2.11	0.84	1.08	1.37	—
ZC2	41.8	5.66	1.88	2.05	0.969	1.07	1.35	1.03
ZC2−W	43.41	5.89	1.91	2.14	0.314	1.08	1.20	0.78
ZC2−A	44.87	5.95	1.75	2.17	0.32	0.75	1.18	0.06
ZO2	42.44	5.80	1.91	2.06	0.756	1.08	1.35	1.27
ZO2−W	43.62	5.86	1.94	2.14	0.305	1.08	1.22	0.98
ZO2−A	44.68	5.91	1.73	2.22	0.31	0.77	1.20	0.05

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