Hydrogen transfer reactions in the catalytic cracking of paraffins

Abbot, J.; Wojciechowski, B. W.

doi:10.1016/0021-9517(87)90309-5

Cited by 50 publications

(19 citation statements)

References 13 publications

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“…The relative activity of FCC catalysts for generating secondary reactions can be estimated using the hydrogen transfer index (HTI) for catalysts tested under constant conditions with the same feed [1,8,27,36,60,91,107]. Catalysts with lower HTIs generate fewer secondary reactions, preserving a greater quantity of the gasoline boiling range olefins, which can be subsequently cracked to lighter olefins.…”

Section: Effect Of Hydrogen Transfer Indexmentioning

confidence: 99%

Maximizing propylene production via FCC technology

2015

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This review looks at the main processes available for the production of light olefins with a focus on maximizing the production of propylene. Maximization of propylene production has become the focus of most refineries because it is in high demand and there is a supply shortage from modern steam crackers, which now produce relatively less propylene. The flexibility of the fluid catalytic cracking (FCC) to various reaction conditions makes it possible as one of the means to close the gap between supply and demand. The appropriate modification of the FCC process is accomplished by the synergistic integration of the catalyst, temperature, reaction-residence time, coke make, and hydrocarbon partial pressure. The main constraints for maximum propylene yield are based on having a suitable catalyst, suitable reactor configuration and reaction conditions.

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Section: Effect Of Hydrogen Transfer Indexmentioning

confidence: 99%

Maximizing propylene production via FCC technology

2015

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“…The extent to which these processes occur depends on the acidity of the catalyst and on the shape and concentration of the olefins. Several groups including ourselves showed that di-and oligomerization requires high concentrations of the olefins (2,(16)(17)(18). High reactant pressures, high conversions, and low temperatures favor these processes.…”

Section: Introductionmentioning

confidence: 99%

Dehydrogenation of Light Alkanes over Zeolites

Narbeshuber

Brait

Seshan

et al. 1997

Journal of Catalysis

112

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The conversion of light paraffins to olefins and the secondary reactions of the unsaturated compounds were investigated on H-ZSM5 and H-Y zeolites between 733 and 823 K. Steady stateand transient response-isotope tracing studies revealed that two mechanisms of dehydrogenation are operative. The main pathway is represented by monomolecular, protolytic dehydrogenation. This reaction contributes most to steady state olefin production. Additionally, at the initial stages of the reaction, extra framework aluminum moieties are speculated to participate in high dehydrogenation activity. This pathway is blocked at later stages of the reaction by product (hydrogen) inhibition. The intrinsic rates of protolytic dehydrogenation and olefin desorption range in the same order of magnitude. At high protolytic dehydrogenation rates, olefin desorption represents the rate determining step. Depending on the process conditions, olefins undergo secondary cracking, oligomerization, or isomerization. The latter proceeds via intramolecular rearrangement, possibly via a cyclopropylcarbenium ion at high temperatures and low conversions. At reaction conditions where bimolecular cracking prevails, isomerization is concluded to occur via secondary cracking of di-or oligomers.

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“…It should be noted that methane is formed here as a primary cracking product. This was not observed for cracking of ethylcyclohexane or cyclooctane at 400°C (Abbot and Wojciechowski, 1987a), nor for n-paraffins at this temper- ature (Abbot and Wojciechowski, 1987b). At 500°C methane is observed during the cracking of n-hexane, but its formation there is due to thermal cracking (Abbot and Wojciechowski, 1987d).…”

Section: Initial Product Distributionmentioning

confidence: 82%

Reactions of cyclopentane on HY Zeolite

Abbot

Wojciechowski

1988

Can J Chem Eng

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The reaction of cyclopentane has been studied on HY zeolite at 500°C. Initial reaction processes included ring cleavage to acyclic C5 species, and cracking to produce fragments in the range C1 ‐ C4. Hydrogen transfer accompanied those processes, so that paraffins as well as olefins were observed as initial products. Cyclopentene was formed as an unstable initial product by the dehydrogenation of the feed, although molecular hydrogen was not found as a primary product. Other dehydrogenated species initially formed included coke and aromatics in the range C6 ‐ C10.

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Hydrogen transfer reactions in the catalytic cracking of paraffins

Cited by 50 publications

References 13 publications

Maximizing propylene production via FCC technology

Maximizing propylene production via FCC technology

Dehydrogenation of Light Alkanes over Zeolites

Reactions of cyclopentane on HY Zeolite

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