Significance of the surface silica/alumina ratio and surface termination on the immersion freezing of ZSM-5 zeolites
Significance of the surface silica/alumina ratio and surface termination on the immersion freezing of ZSM-5 zeolites
复制标题
表面硅铝比和表面终止对ZSM-5沸石浸泡冷冻的意义
DOI：
10.1039/d2cp05466c
复制
发表时间：
2023
影响因子：
3.3
通讯作者：
Freedman, Miriam Arak
中科院分区：
文献类型：
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作者：
Marak, Katherine E.;Nandy, Lucy;Jain, Divya;Freedman, Miriam Arak
大气中的非均匀冰成核影响气候，但冰云对辐射强迫的影响程度尚不确定。促进冰成核的表面是多种多样的。由于O、Si和Al是地壳中最丰富的元素，因此通过探索合成ZSM-5样品来了解Si：Al比率如何影响铝硅酸盐的冰成核活性提供了良好的模型系统。 本文研究了不同硅铝比的ZSM-5分子筛样品的浸渍冷冻。 冰的成核温度随着表面Al含量的增加而增加。此外，当铵（气溶胶颗粒中的常见阳离子）被吸附到沸石表面时，与质子封端的沸石表面相比，初始冻结温度降低高达6 °C。在铵存在下冰成核活性的这种大幅降低表明阳离子可以与表面相互作用以阻断或修饰活性位点。我们的合成样品的表面成分是可调的结果提供了深入了解在大气中的非均质冰成核过程中的表面的作用。我们强调检查表面化学异质性的重要性，在冰成核颗粒，可能会导致从各种老化途径的冷冻机制的更深入的了解。
Heterogeneous ice nucleation in the atmosphere impacts climate, but the magnitude of the effect of ice clouds on radiative forcing is uncertain. Surfaces that promote ice nucleation are varied. Because O, Si, and Al are the most abundant elements in the Earth's crust, understanding how the Si : Al ratio impacts the ice nucleation activity of aluminosilicates through exploration of synthetic ZSM-5 samples provides a good model system. This paper investigates the immersion freezing of ZSM-5 samples with varying Si : Al ratios. Ice nucleation temperature increases with increasing surface Al content. Additionally, when ammonium, a common cation in aerosol particles, is adsorbed to the zeolite surface, initial freezing temperatures are reduced by up to 6 °C in comparison to proton-terminated zeolite surfaces. This large decrease in ice nucleation activity in the presence of ammonium suggests that the cation can interact with the surface to block or modify active sites. Our results on synthetic samples in which the surface composition is tunable gives insight into the role of surfaces in heterogeneous ice nucleation processes in the atmosphere. We emphasize the importance of examining surface chemical heterogeneities in ice nucleating particles that could result from a variety of aging pathways for a deeper understanding of the freezing mechanism.