The synthesis, characterization and catalytic performance of offretite with four distinct crystal morphologies (oval, hexagonal, broccoli-like, and spherical) are presented. As a member of the ABC-6 family of zeolite structures, offretite is likely to form intergrowths which can affect its shape-selective properties. Herein, a combination of experiments (SC-XRD, PXRD, benzene uptake and the methanol-to-hydrocarbon conversion) allows the determination of the mechanism and fraction of twinning. It is demonstrated that the catalysts with the same crystal aspect ratio (AR = 3) yield product spectra dominated by C₂–C₄ aliphatics. Such product selectivity is associated with zeolites with an 8-ring channel system. Interestingly, a significant production of bulky aromatics is seen for the catalyst with the spherical morphology (AS = 1.1) which is a manifestation of the 12-ring pore system of the OFF framework topology. This constitutes the first report of this behavior. The particular display of product shape selectivity can be ascribed to the catalyst particle morphology.

中文翻译：

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沸石的形态和催化剂性能：镁橄榄石将甲醇转化为碳氢化合物

提出了具有四种不同晶体形态（卵形，六边形，西兰花样和球形）的硅藻土的合成，表征和催化性能。作为ABC-6沸石结构家族的一员，贝氏体很可能形成共生体，这会影响其形状选择性能。在此，结合实验（SC-XRD，PXRD，苯吸收和甲醇至烃的转化）可以确定孪生的机理和分数。结果表明，具有相同晶体长宽比（AR = 3）的催化剂产生的产物光谱以C ₂ -C _4为主脂肪族。这种产物选择性与具有8环通道系统的沸石有关。有趣的是，对于具有球形形态（AS = 1.1）的催化剂，可以看到大量的芳烃大量生成，这是OFF骨架拓扑结构的12环孔系统的体现。这构成了此行为的第一个报告。产物形状选择性的特定显示可以归因于催化剂颗粒的形态。