The effect of crystallite size on low-temperature hydrothermal stability of Cu-SAPO-34
The effect of crystallite size on low-temperature hydrothermal stability of Cu-SAPO-34
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DOI：
10.1039/d0cy00414f
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发表时间：
2020-05
影响因子：
5
通讯作者：
Jinpeng Du;Xiaoyan Shi;Yulong Shan;Yingjie Wang;Wenshuo Zhang;Yunbo Yu;Wenpo Shan;Hong He
中科院分区：
文献类型：
--
作者：
Jinpeng Du;Xiaoyan Shi;Yulong Shan;Yingjie Wang;Wenshuo Zhang;Yunbo Yu;Wenpo Shan;Hong He
通过改变结晶条件，得到了两种化学成分相似但晶粒尺寸不同（10 μm和2 μm）的Cu-SAPO-34样品。比较研究了晶粒尺寸对Cu-SAPO-34低温水热稳定性的影响。结果表明，粒径越小的Cu-SAPO-34在70℃潮湿条件下具有更好的耐处理能力。在低温水热老化过程中，Cu- sapo -34中分离的Cu2+容易受到水蒸气的攻击形成Cu(OH)2, Cu(OH)2可以与框架外Al结合形成非活性CuAl2O4。晶粒尺寸较小的Cu- sapo -34具有优异的稳定性，主要是由于晶体表面的Cu浓度低于晶粒尺寸较大的样品。因此，低温热液时效后，小尺寸Cu- sapo -34表面保留了更多的活性Cu位点。
Two Cu-SAPO-34 samples with similar chemical compositions but different crystallite sizes of 10 μm and 2 μm, respectively, were obtained by modifying crystallization conditions. The effect of crystallite size on the low-temperature hydrothermal stability of Cu-SAPO-34 was comparatively investigated. The results showed that Cu-SAPO-34 with smaller particle size possessed better resistance to treatment at 70 °C in humid conditions. During low-temperature hydrothermal aging, isolated Cu2+ species in Cu-SAPO-34 tended to be attacked by water vapor to form Cu(OH)2 species, which can combine with extra-framework Al to form inactive CuAl2O4 species. The superior stability of Cu-SAPO-34 with smaller crystallite size is primarily attributed to the lower Cu concentration on the crystal surface compared with the sample with larger particle size. Thus, more active Cu sites were maintained on small-size Cu-SAPO-34 after low-temperature hydrothermal aging.