The Catalytic Cracking of Aliphatic Hydrocarbons

Egloff, Gustav; Morrell, J. C.; Thomas, Charles L.; Bloch, Herman S.

doi:10.1021/ja01267a104

Cited by 33 publications

(20 citation statements)

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“…Zeolite‐catalyzed cracking of alkenes is a long‐debated reaction that has a prominent—positive or negative—impact in refining, petrochemistry, natural gas and biomass conversions . It is generally assumed that cracking reactions proceed via sequence of steps involving protonation of the C=C bond by the zeolite's Brønsted site, β‐scissions, and proton transfer back to the zeolite.…”

Section: Methodsmentioning

confidence: 99%

Dynamic Features of Transition States for β‐Scission Reactions of Alkenes over Acid Zeolites Revealed by AIMD Simulations

et al. 2020

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Zeolite-catalyzed alkene cracking is key to optimize the size of hydrocarbons. The nature and stability of intermediates and transition states (TS) are, however, still debated. We combine transition path sampling and blue moon ensemble density functional theory simulations to unravel the behavior of C 7 alkenes in CHA zeolite. Free energy profiles are determined, linking p-complexes, alkoxides and carbenium ions, for B 1 (secondary to tertiary) and B 2 (tertiary to secondary) b-scissions. B 1 is found to be easier than B 2. The TS for B 1 occurs at the breaking of the CÀC bond, while for B 2 it is the proton transfer from propenium to the zeolite. We highlight the dynamic behaviors of the various intermediates along both pathways, which reduce activation energies with respect to those previously evaluated by static approaches. We finally revisit the ranking of isomerization and cracking rate constants, which are crucial for future kinetic studies. Scheme 1. b-scission mechanisms: a) type B 1 involving secondary 4,4dimethyl-penten-2-ium to tertiary tert-butylium cation. b) type B 2 involving tertiary 2,4-dimethyl-penten-2-ium to secondary propenium cation.

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Section: Methodsmentioning

confidence: 99%

Dynamic Features of Transition States for β‐Scission Reactions of Alkenes over Acid Zeolites Revealed by AIMD Simulations

et al. 2020

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“…These workers (14) found that a silica-alumina catalyst, similar to commercial cracking catalysts, produced about 59% of 2-methylbutene from ra-pentenes at 400°C. and a space velocity of 3.2 hours-1.…”

Section: + Hydrogen Chloridementioning

confidence: 99%

Review of Olefin Isomerization

Dunning¹

1953

Ind. Eng. Chem.

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“…Besides, the skeletal isomerization or oligomerization would require harder reaction conditions than those of the experiments carried out in this study. Rearrangement of atoms and bonds needs higher temperatures and stronger acid sites, therefore an increase in the formation of iso‐olefins is hardly noticeable 40 . On the other hand, the formation of these isomers is higher than what could be expected considering the transformation of α‐olefins into e‐olefins.…”

Section: Resultsmentioning

confidence: 91%

“…Rearrangement of atoms and bonds needs higher temperatures and stronger acid sites, therefore an increase in the formation of iso-olefins is hardly noticeable. 40 On the other hand, the formation of these isomers is higher than what could be expected considering the transformation of α-olefins into e-olefins. This may be due to the oligomerization reactions between short-chain olefins into larger molecules, 41 which then evolve by isomerization reactions.…”

Section: Catalytic Testmentioning

confidence: 90%

Potential pathways for syngas transformation towards kerosene range hydrocarbons in a dual Fischer‐Tropsch‐zeolite bed

Monte

Vizcaíno

Dufour

et al. 2021

Intl J of Energy Research

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Summary The Fischer‐Tropsch synthesis is considered to be an alternative process to produce liquid hydrocarbons in an environmentally sustainable way by using synthesis gas obtained from renewable resources. The combination of acid catalysts, such as zeolites, with Fischer‐Tropsch catalysts could lead to an increase in the selectivity to an specific range of hydrocarbons, such as synthetic paraffinic kerosene. Therefore, the conversion of synthesis gas in hydrocarbons within kerosene range using catalytic dual beds formed by a potassium‐cobalt‐promoted iron and zeolites H‐ZSM‐5 and H‐ZSM‐12 has been studied. The reactions have been carried out at 250°C, 20 bar in a stacked fixed dual bed using synthesis gas with a H2:CO molar ratio of 2 during 60 hours. The selectivity towards C9‐C16 hydrocarbons was increased from 25% using the FT catalyst without zeolite, and up to 30% by using zeolites H‐ZSM‐5 or H‐ZSM‐12 with a Si/Al of 30 and 60, respectively. The results allowed the development of a reaction scheme suitable to design a tunable process for the synthesis gas conversion.

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The Catalytic Cracking of Aliphatic Hydrocarbons

Cited by 33 publications

References 0 publications

Dynamic Features of Transition States for β‐Scission Reactions of Alkenes over Acid Zeolites Revealed by AIMD Simulations

Dynamic Features of Transition States for β‐Scission Reactions of Alkenes over Acid Zeolites Revealed by AIMD Simulations

Review of Olefin Isomerization

Potential pathways for syngas transformation towards kerosene range hydrocarbons in a dual Fischer‐Tropsch‐zeolite bed

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