Catalytic dealkylation of alkylaromatic compounds. VI. Reactions of dialkylphenols over an acidic catalyst

Kraus, M.; Bažant, V.

doi:10.1135/cccc19631877

Cited by 10 publications

(7 citation statements)

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“…Dealkylation of diEPs leads to 3-and 4-EP. This is consistent with earlier findings showing preferential cracking of 2,4-diEP at the ortho position to the hydroxyl group [38]. This might be explained by a specific adsorption geometry of phenols leading to the ortho position close to the active sites, but we have not studied this further here.…”

Section: Effect Of Pore Structure Of Zeolitessupporting

confidence: 93%

“…The reactivity of EPs is expected to be substantially higher than that of ethylbenzene over the same acidic catalyst. The presence of the phenolic group is likely beneficial for substrate adsorption and formation of the activated complex [38]. It also adds on reaction complexity due to the potential formation of positional isomers.…”

Section: Introductionmentioning

confidence: 99%

“…Dealkylation of EPs to phenol has been reported over an acidic fluoborate catalyst and a silica-alumina catalyst [38,39]. Catalytic conversion of alkylphenols in gas phase to phenol and alkenes was recently proposed over acidic zeolites [4], representing an outstanding opportunity to upgrade depolymerized lignin streams with the use of zeolites [40][41][42].…”

Section: Introductionmentioning

confidence: 99%

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Shape selectivity vapor-phase conversion of lignin-derived 4-ethylphenol to phenol and ethylene over acidic aluminosilicates: Impact of acid properties and pore constraint

Liao

d’Halluin

Makshina

et al. 2018

Applied Catalysis B: Environmental

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Selective dealkylation of alkylphenols, the opposite reaction of the more commonly studied phenol alkylation, may represent an important reaction in the production of base chemicals like phenol and olefins from fossilized and raw lignocellulosic matter. This study reports the first thermodynamics and kinetics studies of the vaporphase conversion of ethylphenol (EP) over acidic γ-Al2O3, amorphous (ASA) and crystalline aluminosilicates (like ferrierite, ZSM-22, ZSM-5, beta, and USY) in the absence of hydrogen and noble metals, as a way to produce phenol and ethylene. The reaction was studied deliberately in presence of steam to get stable time on stream catalysis. The thermodynamic analysis shows an endothermal EP conversion to phenol and ethylene, favoured at high reaction temperature, while isomerisation, disproportionation and transalkylation are thermodynamically preferred at low temperature. The kinetic study examines the role of the catalytically active sites; it reveals the importance of site constraint on the activity, selectivity and stability, and shows the complex temperature dependency of the dealkylation. Both Brønsted and Lewis acid sites are active, but multifactor dependency (such as acid strength and site accessibility) complicates the establishment of simple quantitative relationships with the acid type. EP does not enter the micropores of ferrierite and ZSM-22, as suggested by adsorption experiments. Kinetics without significant diffusion limitations were obtained with ZSM-5, beta and USY. Thus, in absence of intracrystalline diffusion limitation (as verified by calculations using reported effective diffusivities, and substantiated by a comparably high apparent activation energy for all zeolites), the increased reaction turnover rate with increasing pore size from medium to large pore zeolites is largely explained by a change in reaction pathway (from monolecular to bimolecular) to convert EP to phenol and ethylene. A pathway proceeding through fast thermodynamically favourable bimolecular reactions occurs in the spatially non-constrained pores and crystal surface, whereas monomolecular reactions take place in the micropores of ZSM-5. Despite the lower rate, the selectivity over ZSM-5 strongly benefits from active site confinement, being responsible to achieve quantitative formation of phenol and ethylene from ethylphenol. The excellent performance of ZSM-5 thus accords with its shape selective property that avoids undesired side reactions such as the sterically demanding bimolecular reactions like disproportionation, transalkylation and CC cracking, and severe cokes formation.

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Section: Effect Of Pore Structure Of Zeolitessupporting

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Shape selectivity vapor-phase conversion of lignin-derived 4-ethylphenol to phenol and ethylene over acidic aluminosilicates: Impact of acid properties and pore constraint

Liao

d’Halluin

Makshina

et al. 2018

Applied Catalysis B: Environmental

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“…at 0.5 mm.) (22). 5-Fluoro-2-hydroxyacetophenone gave 2-ethyl-4-fluorophenol (20), which was distilled in a short-path distillation apparatus (b.p.…”

Section: Methodsmentioning

confidence: 99%

Preparation and spectral characterization of substituted 2-hydroxyacetophenones and 2-ethylphenols

Givens¹,

Venuto²,

Alexakos³

1969

J. Chem. Eng. Data

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Preparation of substituted 2-hydroxyacetophenones and 2-ethylphenols is reported, along with their mass spectra and NMR data. 2-Hydroxyacetophenones were prepared by the Fries rearrangement of aryl acetates. 2-Ethylphenols were prepared by Clemmensen reduction of these hydroxyacetophenones or direct halogenation of 2-ethylphenol. Both types of compounds fragment under electron impact, predominantly with loss of methyl radical. The loss of acetyl group (m/e 43), either as cation or radical, is of less importance for the hydroxyacetophenones. Chemical shifts and coupling constants for these compounds have been calculated. Intramolecular hydrogen bonding in the 2-hydroxyacetophenones gives rise to low-field hydroxyl proton resonances.

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“…The reaction mechanism of pure alkyl phenols over cracking catalysts was studied (179,180,186). The kinetics of dealkylation of alkyl phenols over aluminum fluoborate on alumina were reported (187) and the influence of the structure of the alkyl phenols on the dealkylation reaction was also discussed (187)(188)(189).…”

Section: Catalytic Cracking Of Tar Acidsmentioning

confidence: 99%

Cracking and hydrogenation of low-temperature coal tars and alkyl phenols

Janardanarao¹

1982

Ind. Eng. Chem. Prod. Res. Dev.

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The deactivation of Ai203-supportéd NI, Nl-Ru, Ni-Mo, and Ni-Mo-Cu catalysts during high-temperature, combined shift/methanatlon was Investigated. Activity-time measurements were conducted for each catalyst over a period of 24 h at 723 K, 138 and 2600 kPa in a fixed bed reactor and at 138 kPa in a fluidized bed reactor. Effects of carbon deposits and regeneration treatments in air or oxygen on metal surface area and specific intrinsic activity were measured for each catalyst. The results establish that Ni and Ni-Ru are significantly more resistant to deactivation by carbon deposits than Mo-containing catalysts. Ni-Mo-Cu deactivates more rapidly than Ni-Mo in a fluidized bed at 138 kPa and in a fixed bed at 2600 kPa. Regeneration of these catalysts in air at 573 K restores specific intrinsic activity but causes significant loss of metal surface area. A model for deactivation is proposed which can be used to estimate catalyst life under carbon-depositing conditions. Mechanisms of deactivation are discussed.

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Catalytic dealkylation of alkylaromatic compounds. VI. Reactions of dialkylphenols over an acidic catalyst

Cited by 10 publications

References 0 publications

Shape selectivity vapor-phase conversion of lignin-derived 4-ethylphenol to phenol and ethylene over acidic aluminosilicates: Impact of acid properties and pore constraint

Shape selectivity vapor-phase conversion of lignin-derived 4-ethylphenol to phenol and ethylene over acidic aluminosilicates: Impact of acid properties and pore constraint

Preparation and spectral characterization of substituted 2-hydroxyacetophenones and 2-ethylphenols

Cracking and hydrogenation of low-temperature coal tars and alkyl phenols

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