Effect of Cr doping on hydrogen production via methanol steam reforming over Cu-Ce composite catalysts
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摘要: 采用浸渍法制备了不同Cr含量的Cr/Cu-Ce催化剂,通过N2O滴定、H2-TPR和XPS等表征,对其结构、性质和催化性能进行了探究。结果表明,Cr助剂会改变Cu-Ce催化剂的铜比表面积、CuO还原温度以及氧空穴含量。其中,添加3%Cr的催化剂的Cu比表面积较大,CuO还原温度较低,氧空穴较多,进而表现出优良的催化性能。当反应温度为533 K,n(水):n(甲醇)=1.2:1,甲醇和水的进料量为0.072 mL/min时,其催化效率达100%,重整气体组分中的CO体积分数为0.15%。与未掺杂Cr助剂的催化剂相比,其催化效率提高了10%,重整气体组分中的CO体积分数降低了0.34%。Abstract: Cr/Cu-Ce catalyts with different Cr contents were prepared by impregnation method, and their structures, properties and catalytic performance were investigated using N2O titration, H2-TPR and XPS techniques. It is found that the Cr doping changs the specific surface area of copper, the reduction temperature of CuO and oxygen vacancies of the Cu-Ce catalysts. In addition, the catalyst with 3% Cr addition has larger Cu specific surface area, lower CuO reduction temperature and more oxygen vacancies, thus exhibits excellent catalytic performance. The catalytic efficiency reaches 100% and CO volume fraction in outlet gas is 0.15% when the reaction temperature is 533 K, n(water):n(methanol) is 1.2:1 and the feeding rate of methanol and water is 0.072 mL/min. Compared with the un-doped Cr catalyst, the catalytic efficiency increases by 10% and the volume fraction of CO in the outlet gas decreases by 0.34%.
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Key words:
- Cr content /
- oxygen vacancy /
- Cu-Ce catalyst /
- reduction temperature
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表 1 不同Cr含量的催化剂中元素含量
Table 1 Elemental content of the catalysts with different Cr contents
Catalyst Elemental content w/% Cu Ce O Cra Crb Cu-Ce 7.9 73.4 18.7 - - 1%Cr/Cu-Ce 7.8 72.5 18.9 0.8 1.0 3%Cr/Cu-Ce 7.3 70.7 19.3 2.7 2.9 5%Cr/Cu-Ce 7.0 69.2 19.5 4.3 4.8 7%Cr/Cu-Ce 6.9 67.5 19.8 5.8 6.5 a: test value; b: designed value 表 2 催化剂的H2产率和物化性质
Table 2 H2 production rate and physicochemical properties of the catalysts
Catalyst Surface areaA/(m2·g-1) Pore volumev/(cm3·g-1) dCuO /nm Cu dispersion /% Cu surface areaaA/(m2·g-1) H2 production rateb /(cm3·g-1·min-1) CeO2 37.4 0.10 - - - - Cu-Ce 21.9 0.09 29.9 15.3 8.8 20.4 1%Cr/Cu-Ce 20.3 0.06 28.1 15.4 8.9 24.6 3%Cr/Cu-Ce 18.6 0.08 20.2 16.8 9.7 35.5 5%Cr/Cu-Ce 18.2 0.06 21.6 16.6 9.6 32.7 7%Cr/Cu-Ce 14.3 0.05 24.8 15.8 9.1 30.4 a: measured by N2O titration; b: reaction conducted at 533 K 表 3 CuO还原温度
Table 3 CuO reduction temperature
Catalyst Peak positionT/K α β γ Cu-Ce 451 495 522 1%Cr/Cu-Ce 445 492 523 3%Cr/Cu-Ce 423 478 508 5%Cr/Cu-Ce 436 490 524 7%Cr/Cu-Ce 441 479 503 表 4 催化剂的Ce 3d拟合
Table 4 Ce 3d fitting results of the catalysts
Catalyst Ce(III)/(Ce(III)+Ce(IV))/% Cu-Ce 18.5 1%Cr/Cu-Ce 20.5 3%Cr/Cu-Ce 34.4 5%Cr/Cu-Ce 33.9 7%Cr/Cu-Ce 27.4 表 5 催化剂的CO、CO2以及H2选择性
Table 5 Selectivity of CO, CO2 and H2
Catalyst Selectivityas/% CO CO2 H2 Cu-Ce 0.59 25.04 74.37 1%Cr/Cu-Ce 0.14 25.43 74.43 3%Cr/Cu-Ce 0.15 25.46 74.39 5%Cr/Cu-Ce 0.23 25.48 74.29 7%Cr/Cu-Ce 0.33 25.23 74.44 a: reaction conducted at 533 K -
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