Thermal resistance effect on anomalous diffusion of molecules under confinement

Yuan, Jiamin; Liu, Zhiqiang; Wu, Yimo; Han, Jingfeng; Tang, Xiaomin; Li, Chengbin; Chen, Wei; Yi, Xiaoyan; Zhou, Jian; Krishna, Rajamani; Sastre, Germán; Zheng, Anmin

doi:10.1073/pnas.2102097118

Cited by 31 publications

(22 citation statements)

References 41 publications

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“…For n -hexadecane with a longer chain, C 4–5 -PCP, C 8 -PCP, and C 12 -PCP were the main reaction paths, in which C 8 -PCP had the highest proportion. The dominant C 8 -PCP path can be interpreted by the “thermal resistance effect (TRE)” theory, which was proposed by the Zheng group . According to the TRE theory, the penetration of the carbon chain can be hindered and deeper adsorption is suppressed due to the deformation of the reactant at high temperature.…”

Section: Resultsmentioning

confidence: 99%

“…For cracking n- The dominant C 8 -PCP path can be interpreted by the "thermal resistance effect (TRE)" theory, which was proposed by the Zheng group. 60 According to the TRE theory, the penetration of the carbon chain can be hindered and deeper adsorption is suppressed due to the deformation of the reactant at high temperature. Therefore, the C 8 -PCP path was much more dominant than the C 12 -PCP path in the hydrocracking of nhexadecane.…”

Section: Analysis Of the Cracking Paths Figure S22mentioning

confidence: 99%

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Four-Carbon Segmented Discrete Hydrocracking of Long-Chain Paraffins in MTT Channels Following a Pore-Mouth Mechanism

et al. 2022

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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.

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Section: Resultsmentioning

confidence: 99%

Section: Analysis Of the Cracking Paths Figure S22mentioning

confidence: 99%

Four-Carbon Segmented Discrete Hydrocracking of Long-Chain Paraffins in MTT Channels Following a Pore-Mouth Mechanism

et al. 2022

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“…The molecular dynamics (MD) simulation has been chosen as a widely used technique in the study of diffusion properties of porous materials. 46–48 And to simplify the system, only a few typical model molecules were simulated, and their diffusion behavior was used to reflect differences in steric constraints during isomerization reactions.…”

Section: Resultsmentioning

confidence: 99%

Shape selectivity of zeolite for hydroisomerization of long-chain alkanes

et al. 2023

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“…Figure 9a,b displays the configuration of C 5 and C 9 moving into the zeolite. Due to the thermal resistance effect, 79 the longer carbon chain will make greater the diffusion resistance to the molecules under confinement, especially at high temperatures. Thus, the number of molecules adsorbed into zeolite follows the order C 2 > C 5 > C 8 > C 9 (Figure 9c).…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Pore-Confined and Diffusion-Dependent Olefin Catalytic Cracking for the Production of Propylene over SAPO Zeolites

Liu

et al. 2022

Ind. Eng. Chem. Res.

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Higher-olefin cracking into propylene is an ideal process to meet the increasing demand for propylene driven by polymer industries. However, this process is usually stuck in poor propylene selectivity owing to the complicated reaction routes for facile side reactions and evident catalyst deactivation from severe coking. In this work, various SAPO zeolites with moderate acidity were synthesized for the 1-hexene cracking reaction. Among them, SAPO-41 exhibited an excellent propylene selectivity of ∼90% at a super high 1-hexene conversion of ∼95% and superior stability. It is ascribed to the dominant monomolecular cracking mechanism derived from the pore-confined effect with elliptical channels (10membered ring, 4.3 × 7.0 Å) and shorter diffusional distance with nanosheet-like morphology, which could effectively suppress the side reactions such as hydrogen transfer and coking. In contrast, fast deactivation and obviously lower propylene selectivity were found over SAPO-5 and SAPO-41/5 with larger circular channels (12-membered ring, 7.3 × 7.3 Å), resulting from much longer diffusional distance and enhanced bimolecular cracking route to give more undesired light alkanes, butenes, aromatics, and cokes. Especially, a systematic experimental investigation combined with molecular dynamics simulation demonstrates that medium chain length alkenes (C 6 −C 8 ) are more suitable for a stable cracking process along with a high conversion level, owing to the synergistic effects between moderate diffusion ability and higher cracking activity.

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Thermal resistance effect on anomalous diffusion of molecules under confinement

Cited by 31 publications

References 41 publications

Four-Carbon Segmented Discrete Hydrocracking of Long-Chain Paraffins in MTT Channels Following a Pore-Mouth Mechanism

Four-Carbon Segmented Discrete Hydrocracking of Long-Chain Paraffins in MTT Channels Following a Pore-Mouth Mechanism

Shape selectivity of zeolite for hydroisomerization of long-chain alkanes

Pore-Confined and Diffusion-Dependent Olefin Catalytic Cracking for the Production of Propylene over SAPO Zeolites

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