水热处理和钨添加对低钒催化剂高温脱硝性能的影响

doi:10.16085/j.issn.1000-6613.2019-1121

摘要/Abstract

摘要：

利用真空过量浸渍法在TiO₂和WO₃-TiO₂载体上负载0.5%钒（质量分数）制备了V₂O₅-TiO₂ （VTi）和V₂O₅/WO₃-TiO₂（VWTi）催化剂，并在含有10%（体积分数）水蒸气的空气氛下750℃水热处理24h得到处理态的VTi-A和VWTi-A催化剂。研究了水热老化和钨掺杂对催化剂脱硝效率的影响，并通过XRD、TEM、NH₃-TPD、H₂-TPR、XPS和Raman等表征方法对催化剂的结构和表面特性进行了表征分析。研究表明，水热处理和钨的协同作用使催化剂中产生更多的聚合态VO_x和低价态钒（V⁴⁺+V³⁺）。这两类活性物质所含有的氧物种具有较强SCR反应活性，可改善VWTi催化剂的高温脱硝性能，即使在酸性位数量减少的情况下仍有提升，这是低钒含量催化剂可满足燃气机组高温脱硝需求的主要原因。

关键词: 水热处理, 钨掺杂, 选择性催化还原, 催化剂, 钒物种

Abstract:

The V₂O₅-TiO₂ (VTi) and V₂O₅/WO₃-TiO₂ (VWTi) catalysts with 0.5% V₂O₅ were prepared by the impregnation method. The obtained catalysts were then treated under airflow with 10% H₂O (g) at 750℃ for 24h to form the hydrothermal aged catalysts (named as VTi-A and VWTi-A). The effects of hydrothermal aging and tungsten doping on the denitration efficiency were studied, and the structure and surface properties of the catalysts were analyzed by means of XRD、TEM、NH₃-TPD、H₂-TPR、XPS and Raman, etc. As a result, two types of the active species, the polymeric VO_x species and low valence vanadium species (V⁴⁺+V³⁺), were greatly produced under the synergistic effects of hydrothermal aging and tungsten doping. The oxygen species contained in these two active species have strong SCR reactivity, which can enhance the high temperature SCR performance of the VWTi catalyst， even when the number of acidic sites is reduced. This explains why the catalyst with low vanadium content can meet the high temperature de-NO_x demand of gas boiler.

Key words: hydrothermal aging, tungsten doping, selective catalytic reduction, catalyst, vanadium species

中图分类号:

刘雪松,汪澜,房晶瑞,陈洪锋,潘驰. 水热处理和钨添加对低钒催化剂高温脱硝性能的影响[J]. 化工进展, 2020, 39(4): 1363-1370.

Xuesong LIU,Lan WANG,Jingrui FANG,Hongfeng CHEN,Chi PAN. Synergistic effects of hydrothermal aging and tungsten addition on the high-temperature SCR performance of low vanadium catalysts[J]. Chemical Industry and Engineering Progress, 2020, 39(4): 1363-1370.

图/表 13

图1 全部催化剂的脱硝效率、N2选择性、NH3氧化和VWTi、VWTi-A硫老化前后的脱硝效率

图2 VTi、VTi-A、VWTi和VWTi-A的XRD谱图

表1 4种催化剂的晶粒尺寸、比表面积、平均孔径和孔容

催化剂	晶粒尺寸/nm	晶胞体积 /nm³	比表面积 /m²·g^-1	平均孔径/nm	孔容 /cm³·g^-1
VTi	19.4	0.1352	61.24	22.5	0.33
VTi-A	31.7	0.1337	29.56	44.1	0.21
VWTi	19.9	0.1351	67.53	18.3	0.34
VWTi-A	21.7	0.1353	59.15	27.4	0.29

图3 VTi、VTi-A、VWTi和VWTi-A的Raman谱图

图4 热处理前后催化剂的TEM图

图5 VTi、VTi-A、VWTi和VWTi-A的NH3-TPD曲线

图6 VTi、VTi-A、VWTi和VWTi-A的H2-TPR图

图7 VTi、VTi-A、VWTi和VWTi-A的Ti 2p谱图

图10 VTi、VTi-A、VWTi和VWTi-A的V 2p3/2谱图

图8 VWTi和VWTi-A的W 4f谱图

图9 VTi、VTi-A、VWTi和VWTi-A的O 1s谱图

表2 V5+、V4+和V3+的结合能、V4++V3+的表面浓度比和化学吸附氧比例

催化剂	结合能/eV			表面原子浓度比/%
催化剂	V⁵⁺	V⁴⁺	V³⁺	(V⁴⁺+V³⁺)/(V⁵⁺+V⁴⁺+V³⁺)	O_α/(O_α+O_β)
VTi	517.3	516.4	—	58.18	25.28
VTi-A	517.4	516.8	516.1	72.68	12.85
VWTi	517.2	516.3	—	62.38	20.05
VWTi-A	517.2	516.5	515.5	80.85	11.81

图11 各催化剂在850～1600cm-1范围内的Raman光谱图

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