Probing NH3-SCR catalytic activity and SO2 resistance over aqueous-phase synthesized Ce-W@TiO2 catalyst
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摘要: 采用水相法制备了Ce、W、Ti复合氧化物催化剂并用于氨选择性催化还原NO (NH3-SCR) 过程。TiO2包裹型Ce-W@TiO2催化剂表现出最佳的催化活性。205-515℃ NO转化率超过90%。SO2的存在造成所有催化剂低温段NO催化转化率的降低和高温段 (425-540℃) NO催化转化率的升高, TiO2@Ce-W表现出优越的低温抗SO2性能。通过普通共沉淀法向Ce-W复合氧化物中引入Ti会导致催化剂表面W丰度、酸性位点的减少和低温NO转化率、耐SO2性能的降低。通过水相法制备的TiO2包裹型的Ce-W@TiO2型催化剂, 有利于表面W丰度、酸性位点、低温抗SO2性能和催化活性的提高。Abstract: A series of mixed Ce, W and Ti oxides catalysts have been prepared and employed to selective catalytic reduction of NO with ammonia (NH3-SCR).It was found that Ce-W@TiO2 exhibited the optimal catalytic activity.Over 90% of NO conversion could be obtained by the surface TiO2-coated Ce-W@TiO2 catalyst at 205-515℃.The presence of SO2 leads to a decrease of low-temperature NO catalytic conversion and an increase of NO conversion above 425℃ over various catalysts, while Ce-W@TiO2 exhibits the optimal low-temperature SO2 resistance.It is noted that introducing Ti into Ce-W mixed oxide via the conventional co-precipitation method attributed to the decrease of surface W atomic abundance and acidic sites as well as inferior low-temperature NO conversion and SO2 resistance.In contrast, the surface TiO2-coated Ce-W@TiO2 catalyst prepared via a modified aqueous-phase method exhibit increased surface W atomic abundance and acidic sites as well as the superior low-temperature NO conversion and SO2 resistance.
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Key words:
- aqueous-phase method /
- NH3-SCR /
- Ce-W@TiO2 /
- NO conversion /
- SO2 resistance
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图 1 Ce-W、Ce-Ti-W、Ce-W@TiO2催化剂的SCR活性评价 (a) 及抗硫性测试 (b)
Figure 1. Catalytic activity over Ce-W, Ce-Ti-W and Ce-W@TiO2 catalysts in the presence (a) and abesence of SO2(b)
(reaction condition: 0.080% NO, 0.080% NH3, 5%O2, 0.020% SO2, N2 balanced, GHSV=60000h-1)
图 2 不同浓度SO2对Ce-W@TiO2催化剂的NH3-SCR活性的影响
Figure 2. Influence of different SO2 concentrations on NH3-SCR activity over Ce-W@TiO2 catalyst
(reaction condition: 0.080% NO, 0.080% NH3, 5% O2, 0.005% to 0.020% SO2, N2 balanced, GHSV=60000h-1)
图 3 Ce-W、Ce-W@TiO2、Ce-Ti-W催化剂的XRD谱图
Figure 3. XRD patterns of Ce-W, Ce-Ti-W and Ce-W@TiO2 catalysts
图 4 Ce-W、Ce-Ti-W、Ce-W@TiO2催化剂的Ce 3d XPS谱图
Figure 4. XPS spectra of Ce 3d over Ce-W, Ce-Ti-W and Ce-W@TiO2 catalysts
图 5 Ce-W、Ce-Ti-W、Ce-W@TiO2催化剂的O 1s XPS谱图
Figure 5. XPS spectra of O 1s over Ce-W, Ce-Ti-W and Ce-W@TiO2 catalysts
图 6 Ce-W、Ce-Ti-W、Ce-W@TiO2催化剂的W 4f XPS谱图
Figure 6. XPS spectra of W 4f over Ce-W, Ce-Ti-W and Ce-W@TiO2 catalysts
图 7 Ce-W、Ce-Ti-W、Ce-W@TiO2催化剂的Ti 2p XPS谱图
中文注解
Figure 7. XPS spectra of Ti 2p over Ce-W, Ce-Ti-W and Ce-W@TiO2 catalysts
英文注解
图 8 Ce-W、Ce-Ti-W、Ce-W@TiO2催化剂的H2-TPR谱图
Figure 8. H2-TPR profiles of Ce-W, Ce-Ti-W and Ce-W@TiO2 catalysts
图 9 Ce-W、Ce-Ti-W、Ce-W@TiO2催化剂的NH3-TPD谱图
Figure 9. NH3-TPD profiles of Ce-W, Ce-Ti-W and Ce-W@TiO2
表 1 Ce-W、Ce-Ti-W、Ce-W@TiO2催化剂表面原子丰度
Table 1. Surface atomic concentration of Ce-W, Ce-Ti-W and Ce-W@TiO2
Sample Surface atomic concentrations w/% Ce Ti W O Ce4+/(Ce3+ + Ce4+) Oα/(Oα+ Oβ) Ce-W 18.04 - 19.52 62.44 76.6 65.2 Ce-W@TiO2 7.47 15.77 11.91 64.85 68.4 62.7 Ce-Ti-W 16.94 12.46 8.61 61.99 63.2 60.8 
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