Synergistic effects of hydrothermal aging and tungsten addition on the high-temperature SCR performance of low vanadium catalysts

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

Abstract

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

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

CLC Number:

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.

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.

Figures/Tables 13

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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

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

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

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

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