Catalytic dealkylation of alkylaromatic compounds. V. Dealkylation kinetics of higher alkylphenols over an acidic catalyst

Schneider, Philippe; Kraus, M.; Bažant, V.

doi:10.1135/cccc19620009

Cited by 9 publications

(12 citation statements)

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“…This is in accord with the retro-Friedel−Crafts C−C cleavage carbocation mechanism in the presence of acidic catalysts and in agreement with earlier data on dealkylation of 4-alkylphenols over large pore fluoborate. 45 Higher diffusivity (e.g., of 4-EP vs. 4-n-BP) thus does not lead to higher conversion rates, corroborating the exclusion of diffusion limitation as perceived earlier by the diffusion criteria calculations (see Experimental Section) and the Koros− Nowak criterion (vide supra). Besides, the apparent activation energy of 4-n-PP is considerably higher than that of 4-EP, viz.…”

supporting

confidence: 70%

“…Iso-isomers are more reactive over ZSM-5-P than the linear propyl isomers, which is in agreement with the reported reactivity order over fluoborate catalysts. 45 The order of 4-iso-PP and 2-iso-PP, being 4-iso-PP > 2-iso-PP, is different though from that obtained over fluoborate catalysts in that the ortho isomer was always reported to be more reactive than its corresponding para-isomers. This difference might be due to reagent shape selectivity in the case of the bulky ortho iso substrate, whereas conversion of n-PP is less sensitive to such reagent pore constraint effect.…”

mentioning

confidence: 88%

“…For instance, dealkylation of alkylphenols, especially ethylphenols (EPs), has been investigated over 5 wt % of aluminum fluoborate on γ-Al 2 O 3 . 44,45 A simple extrapolation of the dealkylation chemistry from alkylbenzene to alkylphenol may not be justified. For example, phenolics have an hydroxyl group that may affect the electron density at distinct locations in the aromatic ring and that may direct the interaction with the acid sites of the catalyst.…”

Section: ■ Introductionmentioning

confidence: 99%

“…This phenomenon is consistent with the results of n-and iso-propylbenzene cracking over zeolites. 45,83,84 C−C cracking to form cresols appearing at high reaction temperature is more pronounced with the ortho isomers. For instance, conversion of 2-iso-PP and 2-n-PP at the highest temperature yields close to 20% cresols, whereas this value is below 5% in the case of 4-substituted PPs.…”

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confidence: 99%

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Propylphenol to Phenol and Propylene over Acidic Zeolites: Role of Shape Selectivity and Presence of Steam

et al. 2018

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This contribution studies the steam-assisted dealkylation of 4-npropylphenol (4-n-PP), one of the major products derived from lignin, into phenol and propylene over several micro-and mesoporous acidic aluminosilicates in gas phase. A series of acidic zeolites with different topology (e.g., FER, TON, MFI, BEA, and FAU) are studied, of which ZSM-5 outperforms the others. The catalytic results, including zeolite topology and water stability effects, are rationalized in terms of thermodynamics and kinetics. A reaction mechanism is proposed by (i) analyzing products distribution under varying temperature and contact time conditions, (ii) investigating the dealkylation of different regio-and geometric isomers of propylphenol, and (iii) studying the reverse alkylation of phenol and propylene. The mechanism accords to the classic carbenium chemistry including isomerization, disproportionation, transalkylation, and dealkylation, as the most important reactions. The exceptional selectivity of ZSM-5 is attributed to a pore confinement, avoiding disproportionation/transalkylation as a result of a transition state shape selectivity. The presence of water maintains a surprisingly stable catalysis, especially for ZSM-5 with low acid density. The working hypothesis of this stabilization is that water precludes diphenyl ether(s) formation in the pores by reducing the lifetime of the phenolics at the active site due to the high heat of adsorption of water on H-ZSM-5, besides counteracting the equilibrium of the phenolics condensation reaction. The water effect is unique for the combination of (alkyl)phenols and ZSM-5.

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confidence: 70%

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confidence: 88%

Section: ■ Introductionmentioning

confidence: 99%

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confidence: 99%

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Propylphenol to Phenol and Propylene over Acidic Zeolites: Role of Shape Selectivity and Presence of Steam

et al. 2018

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“…Washing the base-treated catalyst with HCl (0.1 M) selectively removes (extraframework) Al (related to Lewis acid sites), and that clearly reduces the catalytic activity. This result accords with previous observation, suggesting that Lewis acids, which are removed here by the acid washing, are also able to catalyze the dealkylation of alkylphenols. , Although the total acidity and the corresponding acid strength of ZSM-5- H -0.2M-HCl are fairly similar to those of the parent sample ZSM-5- P , ZSM-5- H -0.2M-HCl gives higher conversion rates (Figure a).…”

Section: Results and Discussionsupporting

confidence: 92%

Aromatics Production from Lignocellulosic Biomass: Shape Selective Dealkylation of Lignin-Derived Phenolics over Hierarchical ZSM-5

Liao

Zhong

d’Halluin

et al. 2020

ACS Sustainable Chem. Eng.

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The selective conversion of lignin or lignin-derived products into bulk chemicals is the foremost challenge for nearfuture lignocellulosic biorefineries. This study investigates the production of phenol and propylene from lignin-derived 4-npropylphenol (4-n-PP) via gas-phase dealkylation over hierarchical ZSM-5 zeolites in the presence of steam. A series of hierarchical ZSM-5 zeolites with different degrees of mesoporosity and acid properties were prepared by alkaline treatment and mild acid washing. The catalytic evaluation reveals a predominant contribution of the strong acid sites to the dealkylation catalysis. Hierarchization of ZSM-5 zeolites via desilication in alkaline generates Lewis acid sites and reduces the amount of strong Brønsted acid sites. Despite their higher activation energy for dealkylation, reactions on the Lewis acid sites are faster at the thermodynamically required high temperature due to a larger entropic contribution to activation on these sites. In addition to the high catalytic activity, the hierarchical zeolites preserve the high phenol and propylene selectivity as bimolecular side reactions such as disproportionation, transalkylation and some C-C cleavage pathways were inhibited. This observation suggests that both the strong Lewis and Brønsted acid sites are located in confined spaces in which selectivity is determined by transition state shape selectivity. The catalytic stability is improved upon hierarchization as the results of lowering of the total amount of strong acid sites and prevention of substantial product diffusion issues (caused by shortening of diffusion paths). Therefore, dealkylation over mesoporous zeolites can be processed under lower water partial pressure. ASSOCIATED CONTENT Supporting informationThe experimental details, N2 sorption isotherms and pore size distribution, X-ray diffraction patterns, NH3-TPD profiles, TGA analysis, supporting catalytic data. This material is available free of charge via the Internet at http://pubs.acs.org.

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Brønsted Acid Catalyzed Tandem Defunctionalization of Biorenewable Ferulic acid and Derivates into Bio‐Catechol

et al. 2020

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An efficient conversion of biorenewable ferulic acid into bio-catechol has been developed. The transformation comprises two consecutive defunctionalizations of the substrate,t hat is,C ÀO( demethylation) and CÀC( de-2-carboxyvinylation) bond cleavage,occurring in one step.The process only requires heating of ferulic acid with HCl (or H 2 SO 4 )a s catalyst in pressurized hot water (250 8 8C, 50 bar N 2 ). The versatility is shown on av ariety of other (biorenewable) substrates yielding up to 84 %di-(catechol, resorcinol, hydroquinone) and trihydroxybenzenes (pyrogallol, hydroxyquinol), in most cases just requiring simple extraction as work-up.

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Catalytic dealkylation of alkylaromatic compounds. V. Dealkylation kinetics of higher alkylphenols over an acidic catalyst

Cited by 9 publications

References 0 publications

Propylphenol to Phenol and Propylene over Acidic Zeolites: Role of Shape Selectivity and Presence of Steam

Propylphenol to Phenol and Propylene over Acidic Zeolites: Role of Shape Selectivity and Presence of Steam

Aromatics Production from Lignocellulosic Biomass: Shape Selective Dealkylation of Lignin-Derived Phenolics over Hierarchical ZSM-5

Brønsted Acid Catalyzed Tandem Defunctionalization of Biorenewable Ferulic acid and Derivates into Bio‐Catechol

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