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首页> 外文期刊>Catalysis science & technology >Insight into the performance of different Pt/KL catalysts for n-alkane (C6–C8) aromatization: catalytic role of zeolite channels
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Insight into the performance of different Pt/KL catalysts for n-alkane (C6–C8) aromatization: catalytic role of zeolite channels

机译：深入了解N-烷烃不同PT/KL催化剂的性能（C6 – C8）芳香化：沸石通道的催化作用

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Zeolite channel architecture is vital to catalytic activity and product distribution during naphtha reforming, which can be effectively utilized by designing the locations of active sites. Herein, uniformly dispersed Pt clusters were deposited on KL zeolite using atomic layer deposition (ALD) to elucidate the catalytic role of the zeolite channel architecture in n-alkane (C6–C8) aromatization. Various characterizations supported that Pt/KL-x catalysts with different Pt cluster positions (namely at the zeolite orifice and within the zeolite channels) were obtained successfully, and Pt clusters preferred to occupy the sites within the zeolite channels for Pt/KL-2 and Pt/KL-3 catalysts with prolonged diffusion time of Pt precursors (60 and 180 seconds, respectively) in ALD treatment. As a result, the aromatic selectivity of the Pt/KL-2 catalyst was up to 81.6%, 55.3% and 46.5% for n-hexane, n-heptane and n-octane aromatization, respectively. Comparatively, the selectivity was only 44.4% (n-hexane), 34.1% (n-heptane) and 34.8% (n-octane), respectively, for the Pt/KL-1 catalyst with Pt clusters at the zeolite orifice due to the Pt precursor diffusion time being limited to 5 seconds. This supported that Pt clusters inside the zeolite channels could facilitate n-alkane aromatization owing to the effective utilization of the channels. The superiority of the channel architecture for n-alkane aromatization decreased as the alkane size increased from C6 to C8. DFT calculation was used to further investigate the relationship between the catalytic role of the channels and carbon numbers, and indicated that primary dehydrogenation of larger-sized alkanes became difficult owing to the minor catalytic role of the channels. The cleavage of primary C–H bonds in n-octane adsorbed on a Pt cluster within the channels had an energy barrier of 1.05 eV (TS), which was higher than those for n-heptane (0.85 eV) and n-hexane (0.3 eV) dehydrogenation. Briefly, the KL zeolite channel architecture was favourable for n-alkane reforming, while the facilitating effect becomes less efficient with increasing alkane size. Our work could ultimately contribute to better understanding of the catalytic role of zeolite channels for n-alkane reforming with various carbon numbers, and understanding the different reaction behaviours of Pt/KL catalysts during C6–C8 dehydrocyclization.
机译：沸石通道体系结构对于NAPHTHA改革期间的催化活性和产品分布至关重要，可以通过设计活性位点的位置来有效利用。在此，使用原子层沉积（ALD）将均匀分散的PT簇沉积在KL沸石上，以阐明N-烷烃（C6 – C8）芳香化中沸石通道结构的催化作用。各种表征支持具有不同PT簇位置的PT/KL-X催化剂（即在沸石孔口和沸石通道内）成功获得了成功的PT簇，而PT簇则希望占据PT/KL-2和PT/KL-2和PT/KLITE通道内的地点PT/KL-3在ALD处理中具有长时间扩散时间（分别为60秒和180秒）的PT/KL-3催化剂。结果，N-己烷，N-己烷和N-辛烷芳香化的PT/KL-2催化剂的芳族选择性分别高达81.6％，55.3％和46.5％。相比之下，对于PT/KL-1催化剂，由于沸石孔的PT/KL-1催化剂，选择性分别为44.4％（N-己烷），34.1％（N-己烷）和34.8％（N-辛烷）（N-辛烷）。 PT前体扩散时间限制为5秒。这支持了由于通道的有效利用，沸石通道内的PT簇可以促进N-烷烃芳香化。随着烷烃尺寸从C6增加到C8，通道结构对N-烷烃芳香化的优势下降。 DFT计算用于进一步研究通道和碳数的催化作用之间的关系，并表明由于通道的较小催化作用，大尺寸烷烃的一级脱氢变得困难。在通道内的PT簇上吸附的N-辛烷中原代C – H键的裂解的能屏障为1.05 eV（TS），该屏障高于N-己烷（0.85 EV）和N-己烷的能量屏障（TS）（0.35 EV）脱氢。简而言之，KL沸石频道体系结构有利于N-Alkane改革，而随着烷烃尺寸的增加，促进效应的效率降低了。我们的工作最终可能有助于更好地理解沸石通道在不同碳数中进行N-烷烃改革的催化作用，并了解C6 – C8脱氢细胞化过程中PT/KL催化剂的不同反应行为。

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