Zeolite morphology is crucial in determining their catalytic activity, selectivity and stability, but quantitative descriptors of such a morphology effect are challenging to define. Here we introduce a descriptor that accounts for the morphology effect in the catalytic performances of H-ZSM-5 zeolite for C₄ olefin catalytic cracking. A series of H-ZSM-5 zeolites with similar sheet-like morphology but different c-axis lengths were synthesized. We found that the catalytic activity and stability is improved in samples with longer c-axis. Combining time-resolved in-situ FT-IR spectroscopy with molecular dynamics simulations, we show that the difference in catalytic performance can be attributed to the anisotropy of the intracrystalline diffusive propensity of the olefins in different channels. Our descriptor offers mechanistic insight for the design of highly effective zeolite catalysts for olefin cracking.

沸石形态对于确定其催化活性、选择性和稳定性至关重要，但这种形态效应的定量描述符难以定义。在这里，我们介绍了一个描述符，该描述符解释了 H-ZSM-5 沸石对 C ₄烯烃催化裂化的催化性能的形态效应。合成了一系列具有相似片状形态但c轴长度不同的H-ZSM-5分子筛。我们发现具有较长c轴的样品的催化活性和稳定性得到改善。结合时间分辨原位FT-IR 光谱与分子动力学模拟，我们表明催化性能的差异可归因于烯烃在不同通道中的晶内扩散倾向的各向异性。我们的描述符为设计用于烯烃裂化的高效沸石催化剂提供了机理见解。