Interplay between pore size and nanoparticle spatial distribution: consequences for the stability of CuZn/SiO2 methanol synthesis catalysts
Interplay between pore size and nanoparticle spatial distribution: consequences for the stability of CuZn/SiO2 methanol synthesis catalysts
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DOI：
10.1016/j.jcat.2013.02.023
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发表时间：
2013-07
影响因子：
7.3
通讯作者：
Gonzalo Prieto;J. Meeldijk;K. P. Jong;P. Jongh
中科院分区：
文献类型：
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作者：
Gonzalo Prieto;J. Meeldijk;K. P. Jong;P. Jongh
颗粒生长是负载型金属催化剂的主要失活机制。这项研究表明，孔径对催化剂稳定性的影响对纳米级金属分布非常敏感。使用 SiO2-凝胶载体（孔径 5-23nm）合成了一组前硝酸盐 CuZn/SiO2 催化剂。调整催化剂组成以获得具有恒定孔体积（1.6Cunm-3）或表面（2.0Cunm-2）总金属负载量的催化剂系列。调整金属硝酸盐前体的热分解程序，以获得表现出明显不同纳米空间分布的<10 nm Cu颗粒，要么聚集在具有小颗粒间距的高金属密度域中，要么均匀分布在具有最大颗粒间距的载体上。在工业相关的甲醇合成条件下，对于具有高密度铜颗粒域的催化剂，观察到失活率随着载体孔径的增加而大幅增加。对于这些样品，局部纳米级 Cu 表面负载由孔径决定，而不是由总体金属含量决定，如 HAADF-STEM/EDX 所确定。相反，均匀分布在 SiO2 载体表面的 Cu 纳米颗粒显示出更高的稳定性，失活率主要与载体孔径无关。催化剂稳定性的差异归因于不同颗粒生长机制的主导。我们的研究强调了局部纳米级特性对于合理化结构参数（例如孔径大小与催化剂稳定性）的相关性的重要性。
Particle growth is a major deactivation mechanism for supported metal catalysts. This study reveals that the impact of pore size on catalyst stability is very sensitive to the nanoscale metal distribution. A set of ex-nitrate CuZn/SiO2catalysts was synthesized using SiO2-gel supports (pore size 5–23nm). The catalyst compositions were adjusted to attain series of catalysts with either constant pore volumetric (1.6Cunm−3) or surface (2.0Cunm−2) overall metal loading. The procedures of thermal decomposition of the metal nitrate precursors were adjusted to achieve <10-nm Cu particles displaying markedly different nanospatial distributions, either gathered in high-metal-density domains with small interparticle spacings or evenly distributed over the support with maximum interparticle spacings. Under industrially relevant methanol synthesis conditions, a large increase in the deactivation rate with the support pore size is observed for catalysts with high-density domains of Cu particles. For these samples, the local, nanoscale Cu surface loading is determined by pore size rather than by the overall metal content, as ascertained by HAADF-STEM/EDX. Conversely, Cu nanoparticles evenly spaced on the surface of the SiO2carrier show improved stability, the deactivation rate being chiefly independent of the support pore size. The differences in catalyst stability are ascribed to the dominance of different particle growth mechanisms. Our study highlights the significance of local, nanoscale properties for rationalizing the relevance of structural parameters such as pore size for catalyst stability.