Experimental study on Mn-doped VWTi catalyst for denitrification in wide temperature range
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摘要: 采用溶胶凝胶法制备了一系列锰掺杂VWTi催化剂,在固定床反应装置上测试了催化剂宽温区脱硝性能,同时考察了催化剂的制备工艺、烟气组分、反应温度、空速等因素对催化剂宽温区脱硝活性的影响,并借助BET、XRD、XPS、SEM和H2-TPR等手段对催化剂进行表征分析。结果表明,Mn掺杂显著提高了催化剂在200–300 ℃的脱硝效率,较低的干燥温度有利于提升催化剂的脱硝活性。催化剂的表征表明,随着干燥温度的上升,催化剂表面的TiO2由锐钛矿晶型向金红石晶型转变、催化剂表面的化学吸附氧占比明显减少、高价锰占比减少、催化剂表面活性组分锰元素和钒元素的占比明显减少、催化剂的低温还原峰逐渐消失,从而降低了催化剂的催化氧化活性。Abstract: A series of manganese-doped VWTi catalysts were prepared by the sol-gel method, and the denitrification performance of the catalysts in a wide temperature range was tested on a fixed bed reactor to examine the influences of catalyst preparation process, flue gas components, reaction temperature, gas hourly space velocity on denitrification activity of the catalyst. The catalyst was characterized and analyzed by means of BET, XRD, XPS, SEM and H2-TPR. The results show that Mn doping significantly improves the denitrification efficiency of the catalyst in the range of 200–300 ℃, and a lower drying temperature is beneficial to improve the denitrification activity of the catalyst. The characterization results of the catalyst show that with the drying temperature increase, the TiO2 on the catalyst surface changes from anatase crystal form to rutile crystal form, the proportion of chemically adsorbed oxygen on the surface of the catalyst is significantly reduced, the proportion of high valence manganese is reduced, the proportion of manganese and vanadium as the active components of the catalyst surface is significantly reduced, and the low-temperature reduction peak of the catalyst gradually disappears. These all reduce the catalytic oxidation activity of catalysts.
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Key words:
- catalyst /
- manganese /
- denitrification /
- drying temperature
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表 1 催化剂的比表面积及孔结构
Table 1 Specific surface area and pore structure parameters of the catalyst
Sample Specific surface area $A/({{\rm{m}}}^{2}\cdot {{\rm{g}}}^{-1})$ Average pore volume $v/({{\rm{cm}}}^{3}\cdot {{\rm{g}}}^{-1})$ Average aperture $ d/{\rm{nm}} $ VWTi(20 ℃ dry) 53.889 0.0753 5.5893 VWTi3%Mn(20 ℃ dry) 53.8208 0.07 5.2024 VWTi3%Mn(50 ℃ dry) 24.2863 0.0496 8.1692 VWTi3%Mn(80 ℃ dry) 94.1657 0.1736 7.3742 表 2 不同干燥温度下催化剂的表面锰原子物质的量分数
Table 2 Fraction of manganese atomic species on the surface of the catalyst at different drying temperatures (%)
Sample Mn 2p Mn2+/MnT Mn3+/MnT Mn4+/MnT VWTi3%Mn(20 ℃ dry) 47.72 46.10 6.18 VWTi3%Mn(40 ℃ dry) 52.77 29.96 17.27 VWTi3%Mn(80 ℃ dry) 54.26 25.66 20.08 表 3 不同干燥温度下催化剂的表面氧原子物质的量
Table 3 Amount and fraction of oxygen atoms on the surface of catalysts at different drying temperatures (%)
Sample O 1s OH/OT O*/ OT OL/OT VWTi(20 ℃ dry) 7.96 17.16 74.88 VWTi3%Mn(20 ℃ dry) 3.30 34.64 62.06 VWTi3%Mn(50 ℃ dry) 7.67 19.98 72.36 VWTi3%Mn(80 ℃ dry) 9.52 18.97 71.51 表 4 不同干燥温度下催化剂的表面元素的质量百分比和原子百分比
Table 4 Weight percentage and atomic percentage of the surface elements of the catalyst at different drying temperatures (%)
Sample Mn V W Ti O VWTi(20 ℃ dry) 0/0 0.67/0.34 5.39/0.75 47.78/25.45 46.16/73.46 VWTi3%Mn(20 ℃ dry) 2.09/1.00 0.66/0.34 5.51/0.78 47.92/26.19 43.82/71.69 VWTi3%Mn(40 ℃ dry) 1.66/0.80 0.45/0.23 5.74/0.83 49.37/27.30 42.78/70.84 VWTi3%Mn(80 ℃ dry) 1.68/0.74 0.45/0.21 5.72/0.76 41.45/21.08 50.71/77.21 -
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