Selective conversion of acetone to isobutene and acetic acid on aluminosilicates: Kinetic coupling between acid-catalyzed and radical-mediated pathways

Herrmann, Stanley; Iglesia, Enrique

doi:10.1016/j.jcat.2018.01.032

Cited by 44 publications

(53 citation statements)

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“…This is in agreement with a recent work of Herrmann and Iglesia, in which two likely reactions mechanisms are disclosed for this reaction. 41 They state that the prevalent mechanism involves the formation of C6 enols (from the C6-pool) on protons, which, subsequently, produce acetic acid and isobutene by radical-mediated pathways. According to them, the C6 β-scission selectivity increases as decreases the concentration of protons.…”

Section: Resultsmentioning

confidence: 99%

Effect of catalyst morphology and hydrogen co-feeding on the acid-catalysed transformation of acetone into mesitylene

Quesada

Faba

Dı́az

et al. 2020

Catal. Sci. Technol.

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Section: Resultsmentioning

confidence: 99%

Effect of catalyst morphology and hydrogen co-feeding on the acid-catalysed transformation of acetone into mesitylene

Quesada

Faba

Dı́az

et al. 2020

Catal. Sci. Technol.

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“…Herrmann and Iglesia have recently reported the selective conversion of acetone to isobutene and acetic acid over Brønsted acidic aluminosilicates and proposed a radical-mediated pathway for the formation of isobutene via an equilibrated pool of C 6 intermediates; however, the catalyst underwent rapid deactivation due to side product formation over the Brønsted acid sites, which produced coke. 20 Hutchings et al have also observed catalyst deactivation for the reaction of acetone to isobutene over Bronsted acidic zeolites BEA and ZSM-5. 21 Ponomareva et al have suggested that Brønsted acid sites on cesium-modified mordenite and MCM-41 were preferable for the synthesis of isobutene from acetone although these authors also observed catalyst deactivation due to coking.…”

Section: Introductionmentioning

confidence: 97%

Mechanism and Kinetics of Isobutene Formation from Ethanol and Acetone over Zn_xZr_yO_z

2019

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Isobutene is a specialty chemical used in the production of fuel additives, polymers, and other high-value products. While normally produced by steam cracking of petroleum naphtha, there is increasing interest in identifying routes to synthesizing isobutene from biomass-derived compounds, such as ethanol and acetone. Recent work has shown that zinc−zirconium mixed oxides are effective and selective catalysts for producing isobutene from ethanol. However, the reaction pathway, the roles of acidic and basic sites, and the role of water in promoting stability and selectivity are not yet clearly defined. In this study, a series of zinc− zirconium mixed oxides with tunable acid−base properties were synthesized and characterized with XRD, Raman spectroscopy, BET, CO 2 -TPD, NH 3 -TPD, and IR DRIFTS of adsorbed pyridine in order to probe the roles of acid and base sites for each step in the ethanol-to-isobutene reaction pathway. The observed reaction kinetics, supported by modeling of these kinetics, suggest that the reaction of ethanol to isobutene proceeds via a five-step sequence. Ethanol first undergoes dehydrogenation to acetaldehyde, which is then oxidized to acetic acid. This product undergoes ketonization to produce acetone, which dimerizes to form diacetone alcohol. The latter product either decomposes directly to isobutene and acetic acid or produces these products by dehydration to mesityl oxide and subsequent hydrolysis. The acetic acid formed undergoes ketonization to produce additional acetone. The dispersion of zinc oxide on zirconia was found to produce a balance between Lewis acidic and basic sites that prevent the loss of ethanol via dehydration to ethylene and promote the cascade reactions of ethanol and acetone to isobutene. Water, while inhibiting both isobutene and mesityl oxide formation, improves isobutene selectivity by suppressing side reactions such as unimolecular dehydration, acetone decomposition, and deactivation due to coke formation.

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“…Since McAllister et al first reported on DAA and MSO conversion to isobutene, 4 extensive studies have been conducted on the direct acetone-to-isobutene conversion (ATIB). 4 − 11 This ATIB cascade reaction, including enolization, C–C coupling (aldol-addition), dehydration, C–C bond scission, and ketonization, may occur depending on the type of active sites (i.e., Brønsted acid sites 5 , 10 , 11 vs Lewis acid–base pairs 8 , 12 ). Over zeolites with Brønsted acid sites, the cascade ATIB via aldol condensation of acetone followed by deoxygenation have been widely accepted.…”

Section: Introductionmentioning

confidence: 99%

“…Over zeolites with Brønsted acid sites, the cascade ATIB via aldol condensation of acetone followed by deoxygenation have been widely accepted. 10 , 11 Recent mechanistic insights reveal that the ATIB over Brønsted acid sites 5 , 6 , 9 , 11 generally starts with the protonation of acetone followed by C–C coupling to form acetone dimers (e.g., DAA, MSO, isomesityl oxide, etc. ); the formed dimers then undergo facile β-scission to produce isobutene ( Scheme 1 ).…”

Section: Introductionmentioning

confidence: 99%

“… 22 Recent studies conducted by Herrmann et al confirmed that water could slow down the deactivation of aluminosilicate catalysts in the ATIB reaction. 5 They also discovered two β-scission pathways, the anhydrous and H 2 O-mediated pathways, to produce isobutene. In the absence of water, dehydrated dimers are the only direct precursor of isobutene (anhydrous β-scission).…”

Section: Introductionmentioning

confidence: 99%

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Elucidating the Cooperative Roles of Water and Lewis Acid–Base Pairs in Cascade C–C Coupling and Self-Deoxygenation Reactions

Guo

Ulumuddin

et al. 2021

JACS Au

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Water plays pivotal roles in tailoring reaction pathways in many important reactions, including cascade C–C bond formation and oxygen elimination. Herein, a kinetic study combined with complementary analyses (DRIFTS, isotopic study, 1 H solid-state magic angle spinning nuclear magnetic resonance) and density functional theory (DFT) calculations are performed to elucidate the roles of water in cascade acetone-to-isobutene reactions on a Zn x Zr y O z mixed metal oxide with balanced Lewis acid–base pairs. Our results reveal that the reaction follows the acetone–diacetone alcohol–isobutene pathway. Isobutene is produced through an intramolecular rearrangement of the eight-membered ring intermediate formed via the adsorption of diacetone alcohol on the Lewis acid–base pairs in the presence of cofed water. OH adspecies, formed by the dissociative adsorption of water on the catalyst surface, were found to distort diacetone alcohol’s hydroxyl functional group toward its carbonyl functional group and facilitate the intramolecular rearrangement of diacetone alcohol to form isobutene. In the absence of water, diacetone alcohol binds strongly to the Lewis acid site, e.g., at a Zr 4+ site, via its carbonyl functional group, leading to its dramatic structural distortion and further dehydration reaction to form mesityl oxide as well as subsequent polymerization reactions and the formation of coke. The present results provide insights into the cooperative roles of water and Lewis acid–base pairs in catalytic upgrading of biomass to fuels and chemicals.

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Selective conversion of acetone to isobutene and acetic acid on aluminosilicates: Kinetic coupling between acid-catalyzed and radical-mediated pathways

Cited by 44 publications

References 50 publications

Effect of catalyst morphology and hydrogen co-feeding on the acid-catalysed transformation of acetone into mesitylene

Effect of catalyst morphology and hydrogen co-feeding on the acid-catalysed transformation of acetone into mesitylene

Mechanism and Kinetics of Isobutene Formation from Ethanol and Acetone over Zn_xZr_yO_z

Elucidating the Cooperative Roles of Water and Lewis Acid–Base Pairs in Cascade C–C Coupling and Self-Deoxygenation Reactions

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Selective conversion of acetone to isobutene and acetic acid on aluminosilicates: Kinetic coupling between acid-catalyzed and radical-mediated pathways

Cited by 44 publications

References 50 publications

Effect of catalyst morphology and hydrogen co-feeding on the acid-catalysed transformation of acetone into mesitylene

Effect of catalyst morphology and hydrogen co-feeding on the acid-catalysed transformation of acetone into mesitylene

Mechanism and Kinetics of Isobutene Formation from Ethanol and Acetone over ZnxZryOz

Elucidating the Cooperative Roles of Water and Lewis Acid–Base Pairs in Cascade C–C Coupling and Self-Deoxygenation Reactions

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Mechanism and Kinetics of Isobutene Formation from Ethanol and Acetone over Zn_xZr_yO_z