CeTiOx脱硝催化剂的抗硫中毒性能

doi:10.7503/cjcu20180241

摘要/Abstract

摘要：

分别以Ce₂(C₂O₄)₃和Ce(SO₄)₂为Ce前驱体, 采用固相球磨法制备了Ce基选择性催化还原(SCR)脱硝催化剂CeTiO_x-A[以Ce₂(C₂O₄)₃为前驱体]和CeTiO_x-B[以Ce(SO₄)₂为前驱体]. 将2个催化剂分别在体积分数为0.15%的SO₂的气氛下反应40和60 h, 得到高硫条件下SCR反应后的CeTiO_x催化剂, 分别记为40CeTiO_x-A, 60CeTiO_x-A, 40CeTiO_x-B和60CeTiO_x-B. 考察了反应前后催化剂的NH₃-SCR反应活性. 采用X射线衍射(XRD)、 X射线荧光光谱(XRF)、比表面积(BET)测试、 H₂程序升温还原(H₂-TPR)、 X射线光电子能谱(XPS)、 NH₃程序升温脱附(NH₃-TPD)及SO₂程序升温脱附(SO₂-TPD)等技术对样品进行了表征. 结果表明, CeTiO_x-A系列催化剂比CeTiO_x-B系列催化剂具有更高的NH₃-SCR反应活性和更好的抗硫抗水性能. 与CeTiO_x-B系列催化剂相比, CeTiO_x-A系列催化剂具有更大的比表面积和孔容, 更多的Ce³⁺和吸附氧(O_α)物种有助于NO的吸附和活化; CeTiO_x-A系统催化剂还具有更多的Lewis强酸性位数量, 可以吸附更多的NH₃分子, 有利于催化剂上NH₃-SCR反应的进行, 提高了CeTiO_x-A系列催化剂的NO转化率.

关键词: 固相球磨法, CeTiO_x催化剂, 选择性催化还原, Lewis酸性位

Abstract:

Ceria-based catalysts(CeTiO_x-A and CeTiO_x-B) were prepared by solid state ball milling method with Ce₂(C₂O₄)₃ and Ce(SO₄)₂ as precursors, respectively. Then, the prepared ceria-based catalysts were treated in reaction atmosphere consisted of 0.15%SO₂ for 40 and 60 h, respectively. The obtained catalysts were designated as 40CeTiO_x-A, 60CeTiO_x-A, 40CeTiO_x-B and 60CeTiO_x-B. The performances of fresh and used catalysts for selective catalytic reduction(SCR) of NO with NH₃ as the reductant were investigated. The catalysts were also characterized using X-ray diffraction(XRD), X-ray fluorescence spectra(XRF), Brunner emmet teller(BET), H₂-temperature programmed reduction(H₂-TPR), X-ray photoelectron spectra(XPS), NH₃-temperature programmed desorption(NH₃-TPD) and SO₂-temperature programmed desorption(SO₂-TPD) techniques. The results indicated that the NH₃-SCR activity, SO₂ and H₂O resistance over the CeTiO_x-A catalysts were better than over the CeTiO_x-B samples. The reasons for this phenomenon are that CeTiO_x-A catalysts possess larger specific surface area and pore volume than CeTiO_x-B catalysts. Besides, CeTiO_x-A catalysts have plenty of Ce³⁺ and the surface adsorbed oxygen, which would benefit the adsorption and activation of NO. Furthermore, CeTiO_x-A catalysts also have numerous strong Lewis acid sites, which lead to the increasing adsorption of NH₃. Therefore, the NH₃-SCR reaction rate and the NO conversion of CeTiO_x-A catalysts was improved.

Key words: Solid state ball milling method, CeTiO_x catalyst, Selective catalytic reduction, Lewis acid site

中图分类号:

O643

TrendMD:

朱红太, 宋丽云, 何洪, 尹孟奇, 程杰, 孙炎明, 李世宁, 邱文革. CeTiO_x脱硝催化剂的抗硫中毒性能. 高等学校化学学报, 2019, 40(2): 350.

ZHU Hongtai,SONG Liyun,HE Hong,YIN Mengqi,CHENG Jie,SUN Yanming,LI Shining,QIU Wenge. Sulfur Tolerance of the CeTiO_x Catalysts for Selective Catalytic Reduction of NO with NH₃^†. Chem. J. Chinese Universities, 2019, 40(2): 350.

图/表 9

Fig.1 NH3-SCR activity(A) and N2 selectivity(B) over the catalystsReaction conditions: 0.1%NO+0.1%NH3+6%O2+0.0175%SO2+6%H2O, He balance, GHSV: 3×104 h-1. a. CeTiOx-A; b. CeTiOx-B; c. 40CeTiOx-A; d. 40CeTiOx-B; e. 60CeTiOx-A; f. 60CeTiOx-B.

Fig.2 NH3-SCR activity over CeTiOx-A(a) and CeTiOx-B(b) in the presence of SO2/H2O at 300 ℃Reaction condition: 0.1%NO+0.1%NH3+6%O2+0.0175%SO2+6%H2O, N2 balance, GHSV: 3×104 h-1.

Fig.3 XRD patterns of CeTiOx-A(a), CeTiOx-B(b), 40CeTiOx-A(c), 40CeTiOx-B(d), 60CeTiOx-A(e) and 60CeTiOx-B(f)

Table 1 Component content, BET surface area and pore volume of the catalysts

Sample	Component content(mass fraction, %)			BET surface area/(m²·g^-1)	Pore volume/(cm³·g^-1)
Sample	TiO₂	CeO₂	SO₃	BET surface area/(m²·g^-1)	Pore volume/(cm³·g^-1)
CeTiO_x-A	67.5	31.8	0.41	112	0.34
CeTiO_x-B	64.6	34.7	0.36	105	0.30
40CeTiO_x-A	61.5	31.8	6.32	66	0.26
40CeTiO_x-B	61.2	33.9	4.51	52	0.19
60CeTiO_x-A	62.1	31.7	5.83	60	0.25
60CeTiO_x-B	60.4	33.2	6.06	52	0.19

Fig.4 H2-TPR profiles of CeTiOx-A(a), CeTiOx-B(b), 40CeTiOx-A(c), 40CeTiOx-B(d), 60CeTiOx-A(e) and 60CeTiOx-B(f)

Table 2 H2 consumption of the catalysts

Sample	H₂ consumption/(μmol·g^-1)			Sample	H₂ consumption/(μmol·g^-1)
Sample	Peak 1	Peak 2	Total	Sample	Peak 1	Peak 2	Total
CeTiO_x-A	36	-	36	40CeTiO_x-B	270	163	432
CeTiO_x-B	30	-	30	60CeTiO_x-A	117	69	186
40CeTiO_x-A	106	53	159	60CeTiO_x-B	319	187	506

Fig.5 XPS results of Ti2p(A), S2p(B), Ce3d(C) and O1s(D) of the catalystsa. CeTiOx-A; b. CeTiOx-B; c. 40CeTiOx-A; d. 40CeTiOx-B; e. 60CeTiOx-A; f. 60CeTiOx-B.

Table 3 XPS results of the catalysts

Sample	Surface atomic concentration(%)				Surface atomic ratio(%)
Sample	Ce	Ti	O	S	Ce³⁺/(Ce³⁺+Ce⁴⁺)	O_α/(O_α+O_β)
CeTiO_x-A	2.6	32.6	63.6	1.2	22.8	35.9
CeTiO_x-B	1.6	34.2	63.2	1.0	19.8	35.1
40CeTiO_x-A	1.4	29.1	65.3	4.2	45.2	55.9
40CeTiO_x-B	1.3	31.4	64.3	3.0	42.0	52.1
60CeTiO_x-A	1.4	29.9	64.9	3.9	36.1	53.9
60CeTiO_x-B	1.0	30.8	64.5	3.7	35.1	37.5

Fig.6 NH3-TPD(A) and SO2-TPD(B) profiles of CeTiOx-A(a), CeTiOx-B(b), 40CeTiOx-A(c), 40CeTiOx-B(d), 60CeTiOx-A(e) and 60CeTiOx-B(f)

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