Hydrocracking of long-chain paraffins is a key process in petroleum refining. A fundamental understanding of the reaction on the bifunctional catalyst is of great importance for controllable cracking. In this work, a mechanism study on the hydrocracking of long-chain paraffins catalyzed by Pt/ZSM-23 has been carried out. The distribution and accessibility of acid sites on MTT channels are purposefully adjusted. Based on reasonable simplification, the reaction data are analyzed to reveal the shape selectivity, reaction path, and catalytic mechanism. The applicability of the pore-mouth mechanism in this system has been carefully verified by experiments. Both protonated cyclopropane (PCP) and β-scission paths occurred simultaneously at the pore mouths, accounting for 60 and 40%, respectively. The proportions of PCP and β-scission paths with different chain lengths inserted in the pore are quantitatively calculated, which are multimodal. Shape selectivity of the teardrop-shaped MTT skeletal structure is investigated by the joint experimental–theoretical method. The insertion of the paraffin chain in the MTT channel is discretely segmented by integral multiples of four sequential carbon atoms starting at one end of the chain, which is followed by cracking through the mixed PCP and β-scission paths at pore mouths.

中文翻译：

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MTT 通道中长链烷烃的四碳分段离散加氢裂化遵循孔口机理

长链烷烃的加氢裂化是石油精炼的关键过程。对双功能催化剂上的反应的基本了解对于可控裂化非常重要。在这项工作中，对 Pt/ZSM-23 催化的长链烷烃加氢裂化的机理进行了研究。有目的地调整 MTT 通道上酸性位点的分布和可及性。在合理简化的基础上，对反应数据进行分析，揭示形状选择性、反应路径和催化机理。孔口机制在该系统中的适用性已通过实验仔细验证。质子化环丙烷（PCP）和β-断裂路径同时发生在孔口处，分别占60％和40％。定量计算了插入孔中不同链长的PCP和β-断裂路径的比例，是多峰的。通过联合实验-理论方法研究了泪滴形 MTT 骨架结构的形状选择性。MTT 通道中石蜡链的插入被从链的一端开始的四个连续碳原子的整数倍离散分段，随后在孔口处通过混合的 PCP 和 β-断裂路径裂解。