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    CuZnAl−xZr催化剂在CO2加氢制甲醇反应中Zr对Cu/ZnO界面形成的调控作用

    Regulatory effect of Zr on formation of Cu/ZnO interface in CuZnAl−xZr catalysts during CO2 hydrogenation to methanol reaction

    • 摘要: 通过催化转化技术将CO2转化为甲醇,能够有效缓解其对气候环境的负面影响。然而,催化剂的组成和结构对催化反应的效率和选择性具有显著影响。为进一步提高CuZnAl工业催化剂在CO2加氢制甲醇反应中的活性,采用浸渍法将Zr4+引入CuZnAl催化剂体系,成功制备了CZA−xZr(不同质量分数Zr的CuZnAl)催化剂,系统探究了Zr对Cu/ZnO界面形成的调控作用。通过XRD、HRTEM、XPS、N2O滴定、ICP-OES、H2-TPR以及CO2-TPD测试对催化剂结构及表面电子状态进行表征。结果表明,在3 MPa,230 ℃,40000 mL/(g·h),φ(H2)∶φ(CO2) = 4,的反应条件下,CZA−2Zr催化剂的甲醇生成速率最高(25.4 mmol/(g·h)),相较于未改性的CZA催化剂提升了23.9%。各催化剂的表观活化能未发生显著变化,甲醇的合成活性取决于催化剂表面参与反应的活性位点数量。随着Zr质量分数的增加,Cu与Zr之间未发生电子间的相互作用;然而,由于Zn与Zr之间的相互作用,Zr的电子逐渐向Zn转移,促进了甲醇的选择性增加。值得注意的是,Zn与Zr在煅烧过程中就已发生相互作用。通过HRTEM结果可清晰地观察到催化剂中的金属−氧化物界面,并发现ZnO粒径呈现先减小后增大的变化趋势。而由于ZnO的分散作用,Cu0的分散度与之呈负相关关系。随着Zr质量分数的增加,催化剂中Cu/ZnO界面数量呈火山型变化趋势,CO2的有效吸附量呈现与之相同的变化趋势。其中,CZA−2Zr催化剂因具有最多的Cu/ZnO界面而表现出最高的反应物转化率。

       

      Abstract: The catalytic conversion of CO2 to methanol presents an effective approach to mitigate its adverse climatic and environmental impacts. The composition and structure of catalysts significantly influence the efficiency and selectivity of catalytic reactions. To enhance the activity of CuZnAl industrial catalysts in CO2 hydrogenation to methanol, Zr4+ was introduced into the CuZnAl catalyst system via impregnation, successfully preparing CZA−xZr (CuZnAl with different Zr contents) catalysts. The role of Zr in regulating the formation of Cu/ZnO interfaces was systematically investigated. The catalyst structure and surface electronic states were characterized using XRD, HRTEM, XPS, N2O titration, ICP-OES, H2-TPR, and CO2-TPD. Results indicate that under reaction conditions of 3 MPa, 230 ℃, 40000 mL/(g·h), φ(H2)∶φ(CO2) = 4, the CZA−2Zr catalyst exhibits the highest methanol production rate of 25.4 mmol/(g·h), representing a 23.9% increase compared to the unmodified CZA catalyst. The apparent activation energy of the catalysts remains unchanged, and the methanol synthesis activity is determined by the number of active sites on the catalyst surface. As the Zr content increases, no electronic interaction occurs between Cu and Zr. However, due to the interaction between Zn and Zr, electrons gradually transfer from Zr to Zn, promoting an increase in methanol selectivity. Zn and Zr species initiated mutual interactions during the calcination process. HRTEM results clearly reveal the metal-oxide interfaces in the catalysts and show that the ZnO particle size initially decreases and then increases. The dispersion of Cu0 is negatively correlated with ZnO dispersion. With increasing Zr content, the number of Cu/ZnO interfaces in the catalyst follows a volcanic trend, and the effective CO2 adsorption capacity exhibits the same variation pattern. the CZA−2Zr catalyst exhibits the highest reactant conversion rate due to the highest number of Cu/ZnO interfaces.

       

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