Highly active Y-promoted CuO/ZrO2 catalysts for the production of hydrogen through water-gas shift reaction
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摘要: 采用水热法制备了具有不同Y掺杂量的单分散ZrO2纳米粒子（n（Y）/n（Y+Zr）=0-5%），并以其为载体采用沉积-沉淀法制得CuO/ZrO2催化剂；考察了富氢气氛下上述催化剂的水煤气变换反应（WGS）催化性能。结果表明，掺杂Y后催化剂的活性明显提高，其中，载体掺杂2% Y的催化剂具有最佳的催化活性，在270℃时的CO转化率高达91.4%，明显高于研究较多的CuO/ZnO和CuO/CeO2催化剂。X射线粉末衍射、N2物理吸附-脱附、N2O滴定、扫描电镜和CO程序升温还原等表征结果表明，Y3+掺入了ZrO2的晶格并对催化剂的结构和还原性能产生直接影响。Y助剂的引入一方面促进了CuO在ZrO2表面的分散，提高了催化剂表面活性Cu-[O]-Zr物种的含量；另一方面，改善了催化剂的颗粒单分散性和织构性能。载体掺杂2% Y助剂的样品具有较高的Cu-[O]-Zr物种含量、较佳的颗粒单分散性和织构性能，且其表面的Cu-[O]-Zr物种和活性羟基具有较佳的还原性能，因而表现出较高的催化活性。
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关键词:
- CuO/ZrO2催化剂 /
- 水煤气变换反应 /
- Y助剂 /
- 氧空位 /
- 表面羟基
Abstract: ZrO2 doped with various concentrations of yttrium(0-5%) was prepared by a hydrothermal homogeneous co-precipitation method and CuO was then deposited on ZrO2 by a deposition-precipitation method to get the yttrium promoted CuO/ZrO2 catalyst; its performance in the water-gas shift reaction for producing hydrogen was then investigated. The results indicate that the catalytic activity of CuO/ZrO2 can be effectively improved by yttrium modification; over the yttrium promoted CuO/ZrO2 catalyst with an yttrium concentration of 2%, the CO conversion reaches 91.4% at 270℃, much higher than those over the conventional CuO/ZnO and CuO/CeO2 catalysts. The XRD, N2-physisorption, N2O titration, SEM and CO-TPR characterization results reveal that Y3+ is successfully incorporated into the lattice of ZrO2, which has a great influence on the structure and reducibility of the CuO/ZrO2 catalysts. Y3+ doping into ZrO2 introduces oxygen vacancies, improving the dispersion of CuO and increasing the proportion of catalytically active Cu-[O]-Zr species. In addition, the introduction of yttrium improves the monodispersity and modifies the texture properties of the CuO/ZrO2 catalysts. As a result, the superior activity of 2% yttrium promoted CuO/ZrO2 catalyst is probably attributed to the abundance of Cu-[O]-Zr species, high reducibility of Cu-[O]-Zr species and surface hydroxyl groups, high monodispersity and proper textural properties. -
图 1 掺杂不同含量Y助剂的CuO/ZrO2催化剂的XRD谱图
Figure 1 XRD patterns of Y-doped CuO/ZrO2 catalysts a: Cu/Zr; b: Cu/Zr-2Y; c: Cu/Zr-5Y
图 2 掺杂不同含量Y助剂的CuO/ZrO2催化剂的SEM照片
Figure 2 SEM images of Y-doped CuO/ZrO2 catalysts
(a): Cu/Zr; (b): Cu/Zr-2Y; (c): Cu/Zr-5Y
图 3 掺杂不同含量Y助剂的CuO/ZrO2催化剂的N2物理吸附-脱附曲线(a)和孔径分布(b)
Figure 3 N2 adsorption-desorption isotherms (a) and pore size distribution (b) of Y-doped CuO/ZrO2 catalysts
图 4 掺杂不同含量Y助剂的CuO/ZrO2催化剂的CO-TPR谱图
Figure 4 CO-TPR profiles of Y-doped CuO/ZrO2 catalysts
a: Cu/Zr; b: Cu/Zr-2Y; c: Cu/Zr-5Y
图 5 掺杂不同含量Y助剂的CuO/ZrO2催化剂的WGS活性图
Figure 5 Activity of Y-doped CuO/ZrO2 catalyst in the WGS reaction
reaction condition: feed gas, 15%CO/7% CO2/55% H2/23% N2; steam/gas ratio, 0.4:1; space velocity, 4 000 cm3/(g·h)
图 6 Cu/Zr-2Y、CuO/ZnO和CuO/CeO2催化剂的WGS活性图
Figure 6 Activity of Cu/Zr-2Y, CuO/ZnO and CuO/CeO2 catalysts in the WGS reaction
reaction condition: feed gas, 15%CO/7% CO2/55% H2/23% N2; steam/gas ratio, 0.4:1; space velocity, 4 000 cm3/(g·h)
表 1 掺杂不同含量Y助剂的CuO/ZrO2催化剂的结构性质
Table 1 Structural properties of Y-doped CuO/ZrO2 catalysts
Sample Cu contentaw/% dCub /% Vtc /% Crystallite sized d/nm Surface area A/(m2·g-1) Pore volume v/(cm3·g-1) CZ 8.32 54.8 0 6.1 84.8 0.214 CZY2 8.27 59.3 3 5.0(4.5) 98.3 0.312 CZY5 8.40 64.7 31 4.3(3.9) 93.0 0.274 a：measured by ICP-OES; b：Cu dispersion calculated from N2O titration results;
c：the mole fraction of tetragonal phase ZrO2 in the sample;
d：cystallite size of m-ZrO2, value in parenthesis is the crystallite size of t-ZrO2
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表 2 掺杂不同含量Y助剂的CuO/ZrO2催化剂的还原性能
Table 2 Reducibility of Y-doped CuO/ZrO2 catalysts
Sample CO-TPR peak temperature t/℃ peak β peak γ peak δ Cu/Zr 154.2 132.8 241.2 Cu/Zr-2Y 152.2 127.1 234.6 Cu/Zr-5Y 165.2 130.1 246.5
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