Catalytic combustion performance of copper manganese catalyst for low concentration ethanol
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摘要:
乙醇汽油车尾气中除了传统汽油车的三大常规污染物（CO、NOx和HCs），还含有导致光化学烟雾和臭氧污染的醇醛类非常规有机物。采用共沉淀法制备了CuOx、MnOx和CuMnOx催化剂用于乙醇汽油车冷启动排放的低浓度乙醇的催化燃烧，同时采用氮气吸附脱附技术（BET）、X射线衍射（XRD）、氢气程序升温还原（H2-TPR）、扫描电子显微镜（SEM）、X射线光电子能谱（XPS）对催化剂进行了表征。研究表明，CuMnOx催化剂对低浓度乙醇具有较好的低温催化活性；当反应温度为185 ℃时，CO2产率可达86%，优于单一的CuOx催化剂（约20%）；同时，CuMnOx比MnOx具有较高的CO2选择性。Cu、Mn之间的相互作用改变了催化剂的织构、结构和氧化性能，引起了催化剂表面晶貌和电子环境的变化，使得CuMnOx催化剂表面具有大量的氧缺陷位，有利于氧分子在其表面的吸附，进而活化成表面活性氧物种。
Abstract:In addition to the three conventional pollutants (CO, NOx and HCs) of traditional gasoline vehicles, gasohol vehicle exhausts also contained alcohols and aldehydes which led to photochemical smog and ozone pollution. CuOx, MnOx and CuMnOx catalysts were prepared by the co-precipitation method for catalytic combustion of low-concentration ethanol emitted from gasohol vehicles in cold start. Moreover, the catalysts were characterized by BET nitrogen adsorption-desorption, X-ray diffraction (XRD), hydrogen temperature programmed reduction (H2-TPR), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The results showed that CuMnOx catalyst had a better low-temperature catalytic activity for low-concentration ethanol. When the reaction temperature was 185 °C, the yield of CO2 was as high as 86%, better than that of single CuOx catalyst (about 20%). Meanwhile, CuMnOx had a higher CO2 selectivity than MnOx. The interactions between Cu and Mn altered the texture, structure and oxidation performance of the catalyst, resulting in the changes in the crystal morphology and electronic environment of the catalyst. There were a large number of oxygen defect sites on the surface of CuMnOx, which was in favour of the adsorption of oxygen molecules, then turning into surface active oxygen species.
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图 1 反应装置流程
1—氮气钢瓶；2—空气钢瓶；3—乙醇气钢瓶；4—气体质量流量计；5—温控仪；6—混气瓶；7—催化剂；8—固定床反应器；9—气相色谱；10—热电偶；11—程序升温控制仪；12—尾气吸收装置。
Figure 1. Flow chart of reaction device
图 3 催化剂样品的N2吸脱附等温线
Figure 3. Nitrogen adsorption-desorption isotherms of the catalyst samples
图 8 乙醇催化燃烧活性测试
Figure 8. Test of catalytic combustion performance of catalysts for ethanol
表 1 催化剂样品的织构性能
Table 1. Texture properties of the catalyst samples
样品 比表面积/(m2/g) 总孔容/(cm3/g) 平均孔径/nm CuOx 18 0.16 28.6 MnOx 79 0.16 5.5 CuMnOx 47 0.18 7.9 
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表 2 催化剂样品O1s的XPS数据
Table 2. O1s XPS data of the samples
样品 Oα Oβ Oα/Oβ 能带/eV 相对含量/% 能带/eV 相对含量/% CuOx 531.4 28.77 529.6 71.23 0.40 MnOx 531.4 40.60 529.6 59.40 0.68 CuMnOx 531.4 65.46 529.9 34.54 1.90
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