Abstract Zeolites have a vital role in the conversion of naphtha to more valuable products, especially when the price of crude oil is falling down. Medium-pore zeolites such as MTW zeolite, for instance, require further modification to produce more valuable products with higher selectivity and conversion. ZSM-12 (MTW) zeolite was synthesized and modified using an impregnation method by adding extra-framework elements, namely, cerium, boron, and lanthanum with different loadings to visualize the role of these extra-framework elements on the catalytic cracking. It was observed that impregnation has a negligible effect on the zeolitic phase of MTW zeolites as confirmed by XRD patterns. Weak and strong acid sites were affected by the presence of extra-framework elements. However, impregnation of ZSM-12 with extra-framework elements led to the decrease in Bronsted and increase in Lewis acid sites as observed from pyridine FTIR. The catalytic performance of impregnated ZSM-12 zeolite was applied in n-hexane cracking at 650 °C under atmospheric pressure. Despite the decrease in the catalytic conversion in the presence of the extra-framework, impregnation slightly enhanced the selectivity towards light olefins and depress the selectivity of the paraffin. The highest selectivity to olefins was observed over B-ZSM-12 zeolite with 2 wt.% of boron with an average selectivity of 69% and average conversion of 64% after 240 min.

中文翻译：

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镧、铈和硼掺入 ZSM-12 沸石用于正己烷催化裂化

摘要 沸石在将石脑油转化为更有价值的产品方面起着至关重要的作用，尤其是在原油价格下跌时。例如，MTW 沸石等中孔沸石需要进一步改性以生产具有更高选择性和转化率的更有价值的产品。ZSM-12 (MTW)​​ 沸石采用浸渍法合成和改性，通过添加不同负载量的额外骨架元素，即铈、硼和镧，以可视化这些额外骨架元素对催化裂化的作用。观察到浸渍对 MTW 沸石的沸石相的影响可以忽略不计，正如 XRD 图案所证实的那样。弱酸和强酸位点受到额外骨架元素的影响。然而，从吡啶 FTIR 观察到，用额外的骨架元素浸渍 ZSM-12 导致布朗斯台德的减少和路易斯酸位点的增加。浸渍ZSM-12沸石的催化性能应用于650℃常压正己烷裂解。尽管在存在额外骨架的情况下催化转化率降低，但浸渍略微提高了对轻烯烃的选择性并降低了链烷烃的选择性。在硼含量为 2 重量％的 B-ZSM-12 沸石上观察到对烯烃的最高选择性，240 分钟后平均选择性为 69％，平均转化率为 64％。尽管在存在额外骨架的情况下催化转化率降低，但浸渍略微提高了对轻烯烃的选择性并降低了链烷烃的选择性。在硼含量为 2 重量％的 B-ZSM-12 沸石上观察到对烯烃的最高选择性，240 分钟后平均选择性为 69％，平均转化率为 64％。尽管在存在额外骨架的情况下催化转化率降低，但浸渍略微提高了对轻烯烃的选择性并降低了链烷烃的选择性。在硼含量为 2 重量％的 B-ZSM-12 沸石上观察到对烯烃的最高选择性，240 分钟后平均选择性为 69％，平均转化率为 64％。