Mechanism of Aromatic Hydrocarbon Formation in FCC Naphtha

Mota, Cláudio J. A.; Rawet, Raul

doi:10.1021/ie00039a024

Cited by 18 publications

(13 citation statements)

References 10 publications

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“…Aromatics may be formed directly by cracking of side chains in heavy aromatic molecules in the feedstock, or by secondary hydrogen transfer reactions after olefin cyclization in the complex network of chemical reactions in FCC. 6,7 The reaction of model compounds may help to understand mechanistic and accessibility issues. For example, bulky molecules such as tri-isopropylbenzene were used to test accessibility in commercial FCC catalysts and in aluminas used as FCC catalyst matrix, showing that a direct relationship exists between alumina activity and mean pore size and accessibility in those matrices.…”

Section: Introductionmentioning

confidence: 99%

Yield of aromatics from naphthenics upon catalytic cracking

Pujro¹,

Falco²,

Pedrosa³

et al. 2012

J. Braz. Chem. Soc.

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Cis-e trans decalina foram submetidas à reação com catalisadores de craqueamento, para estudar a formação de aromáticos numa fração particular de produtos líquidos do processo de craqueamento catalítico fluido (FCC). Um reator batelada em leito fluidizado, CREC, foi usado a 673 e 723 K com tempos de contato entre 3 e 15 s. Cis-decalina foi muito mais reativa. Apesar de diferenças induzidas e medidas na acessibilidade dos catalisadores, seus perfis de atividade foram similares, sugerindo que restrições difusionais não prevalecem. Os produtos foram hidrocarbonetos C 1 -C 12 , enquanto o coque foi muito baixo. Reações de isomerização, craqueamento, transferência de hidrogênio, abertura/contração de anel e alquilação ocorreram, e produtos das várias reações foram observados em tempos de reação muito baixos. Naftênicos bicíclicos C 10 e aromáticos alquilsubstituídos C 7 -C 11 ou nafteno-aromáticos foram os produtos mais importantes. Um mecanismo de reação com três rotas iniciais (isomerização, abertura de anel e reações de transferência de hidrogênio) foi proposto.Cis-and trans-decalin were reacted over cracking catalysts to study the formation of aromatics in a particular fraction of the liquid products obtained in the fluid catalytic cracking process (FCC). A batch, fluidized bed CREC riser simulator reactor was used at 673 and 723 K and contact times varied from 3 to 15 s. Cis-decalin was much more reactive. Despite differences induced and measured in their accessibility indices, the catalysts led to similar activity profiles, suggesting that diffusion restrictions do not prevail. Products were C 1 -C 12 hydrocarbons while coke was very low. Isomerization, cracking, hydrogen transfer, ring opening, ring contraction and alkylation reactions occurred and products from the various reactions were observed at very short reaction times. Bicyclic C 10 naphthenics and alkyl-substituted C 7 -C 11 aromatics or naphtheno-aromatics were the most important products. A reaction mechanism with three initial routes (isomerization, ring opening and direct hydrogen transfer reactions) was proposed.

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Section: Introductionmentioning

confidence: 99%

Yield of aromatics from naphthenics upon catalytic cracking

Pujro¹,

Falco²,

Pedrosa³

et al. 2012

J. Braz. Chem. Soc.

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“…This reaction is involved in the propagation of the catalytic cycle of cracking 1,2 and alkylation 3 of hydrocarbons, as well as in the formation of aromatic hydrocarbons 4 in gasoline and coke, 5,6 which are carbonaceous materials deposit over the catalyst surface that may lead to loss of activity. Conceptually, HT involves the bimolecular transfer of a hydride from an alkane to a carbenium ion (Scheme 1).…”

Section: Introductionmentioning

confidence: 99%

A theoretical study of the hydride transfer between 1-Adamantyl cation and isopentane

Oliveira¹,

Rosenbach²,

Santos³

et al. 2010

J. Braz. Chem. Soc.

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Foi realizado um estudo teórico da transferência de hidreto entre o cátion 1-adamantila e isopentano, usando a teoria do funcional da densidade em nível PBE1PBE/6-31G (d,p). Os resultados indicaram que há formação de um íon carbônio como intermediário, que é mais estável que os complexos de van der Waals entre os íons carbênios e os alcanos. Os fatores entrópicos são bastante importantes e sobrepujam o termo entálpico à temperatura ambiente.A density functional teory study of the hydride transfer between 1-adamantyl cation and isopentane has been performed at the PBE1PBE/6-31G(d,p) theoretical level. The results indicate that a carbonium ion is involved as intermediate and is more stable than the van der Waals complexes between the carbenium ions and the alkanes. Entropic factors are important and overcome the enthalpic term at room temperature. Keywords: hydride transfer, carbocations, adamantane, isopentane IntroductionIntermolecular or bimolecular hydride transfer (HT) is a crucial step in acid-catalyzed hydrocarbon transformations. This reaction is involved in the propagation of the catalytic cycle of cracking 1,2 and alkylation 3 of hydrocarbons, as well as in the formation of aromatic hydrocarbons 4 in gasoline and coke, 5,6 which are carbonaceous materials deposit over the catalyst surface that may lead to loss of activity. Conceptually, HT involves the bimolecular transfer of a hydride from an alkane to a carbenium ion (Scheme 1). R⊕ + R'-H → R-H + R'⊕ Scheme 1. Schematic representation of hydride transfer reactions.In the gas phase, HT is much slower than proton transfer 7 and shows a negative temperature dependence. [8][9][10] The reaction is believed to occur via formation of a "tight" complex, 11,12 whose structure may resemble a carbonium ion, 13 formed by the interaction of the empty p-orbital of a carbenium ion with the C-H bond of the alkane. The reaction is used 14,15 to assess the carbenium ion stability in the gas phase.In condensed phase, especially on zeolites and other solid acid catalysts, there are few studies regarding hydride transfer. 16,17 Product distribution obtained from bimolecular alkane reactions is potentially interesting for the evaluation of the HT capability of solid acids. However, the validity of the results depends on the system chosen as model reaction. Indeed, variation of the hydride acceptor seems to affect the rates of hydride transfer to a considerably greater extent, than an equal change of the thermodynamic driving force caused by variation of the hydride donor. 18 In addition, some systems involve simultaneous reactions competing with HT, and may significantly affect the interpretation of the results.The 1-adamantyl cation is a stable species 19 and can be synthesized from the 1-adamantanol and fluorosulfonic acid-antimony pentafluoride. 20 On the zeolite surface, this species can be also generated from its halide. 21 In addition de Oliveira et al. 2181 Vol. 21, No. 12, 2010 to the stabilization by sC-C bond hyperconjugation, the 1-adamantyl cation has a cage ...

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“…Typically, FCC units are operated to maximize gasoline yield in refinery operations. Therefore, operation in the gasoline overcracking region is avoided. − …”

Section: Case Studymentioning

confidence: 99%

“…FCC reactor operating conditions such as the operating temperature can be adjusted to maximize the yield of desired products. It is often required to maximize gasoline yield to increase refinery profit margin. − The effect of reaction temperature on the yield of different products and oxygen content is investigated through sensitivity analysis using the developed kinetic model. Reaction temperature is varied from 470 to 550 °C.…”

Section: Case Studymentioning

confidence: 99%

Molecular Modeling of Coprocessing Biomass Fast Pyrolysis Oil in Fluid Catalytic Cracking Unit

Jamri

Smith

2020

Ind. Eng. Chem. Res.

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Integration of renewable sources into transportation fuels production system through FCC units in an oil refinery has gained increased attention. For better understanding of the effect of reaction conditions, blending ratios and feed properties on product yields and qualities, kinetic modelling of FCC units is necessarily required. In this paper, a novel framework for molecular-level modelling of co-processing biomass pyrolysis oil with VGO in an oil refinery FCC unit is developed, which includes molecular-level characterisation of biomass pyrolysis oil and VGO feed blends, synthesis of large-scale and complex reaction network, molecularlevel kinetic modelling and parameter estimation. The rule "same type of reactions has similar activation energies" is employed to significantly reduce the number of kinetic parameters. The kinetic parameters in the proposed model are estimated using a hybrid solution algorithm combining deterministic and stochastic optimisation methods. The computational results demonstrate an overall good agreement between measured and predicted yields using the developed kinetic model for VGO: FPO blending ratio, C/O ratio and reaction temperature of 95:5, 5 and 530 °C, respectively. PONA composition in each layer of product stream (e.g. gasoline, diesel, gasoil, etc.) as well as oxygen compounds compositions and oxygen content are also successfully predicted. The proposed framework can be easily to be extended for modelling of other refinery processes and creates potentials for rigorous simulation and optimisation of refinery operations in order to achieve maximisation of refinery profit or better product quality control.

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Mechanism of Aromatic Hydrocarbon Formation in FCC Naphtha

Cited by 18 publications

References 10 publications

Yield of aromatics from naphthenics upon catalytic cracking

Yield of aromatics from naphthenics upon catalytic cracking

A theoretical study of the hydride transfer between 1-Adamantyl cation and isopentane

Molecular Modeling of Coprocessing Biomass Fast Pyrolysis Oil in Fluid Catalytic Cracking Unit

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