Microwave-Assisted Catalytic Cleavage of C–C Bond in Lignin Models by Bifunctional Pt/CDC-SiC

Wang, Wenliang; Wang, Min; Li, Xinping; Cai, Liping; Duan, Chao; Ni, Yonghao

doi:10.1021/acssuschemeng.9b06606

Cited by 23 publications

(15 citation statements)

References 38 publications

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“…The selective activation of sp 3 –sp 3 carbon‐carbon (C−C) bonds is a major challenge in organic chemistry, and has recently emerged as a critical step in plastic waste deconstruction and biomass valorization [1–7] . However, the inertness of the C−C linkages hinders the selective and energy‐efficient bond activation in these substrates [8–10] .…”

Section: Introductionmentioning

confidence: 99%

Electrochemical Activation of C−C Bonds through Mediated Hydrogen Atom Transfer Reactions

et al. 2022

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Activating inert sp 3 -sp 3 carbon-carbon (CÀ C) bonds remains a major bottleneck in the chemical upcycling of recalcitrant polyolefin waste. In this study, redox mediators are used to activate the inert CÀ C bonds. Specifically, N-hydroxyphthalimide (NHPI) is used as the redox mediator, which is oxidized to phthalimide-N-oxyl (PINO) radical to initiate hydrogen atom transfer (HAT) reactions with benzylic CÀ H bonds. The resulting carbon radical is readily captured by molecular oxygen to form a peroxide that decomposes into oxygenated CÀ C bond-scission fragments. This indirect approach reduces the oxidation potential by > 1.2 V compared to the direct oxidation of the substrate. Studies with model compounds reveal that the selectivity of CÀ C bond cleavage increases with decreasing CÀ C bond dissociation energy. With NHPI-mediated oxidation, oligomeric styrene (OS 510 ; M n = 510 Da) and polystyrene (PS; M n � 10 000 Da) are converted into oxygenated monomers, dimers, and oligomers.

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Section: Introductionmentioning

confidence: 99%

Electrochemical Activation of C−C Bonds through Mediated Hydrogen Atom Transfer Reactions

et al. 2022

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“…However, relative to those of PA/Wood, the | R max1 | values of PS/Wood were decreased (21.5% reduction in nitrogen and 21.7% reduction in air), whereas the T max1 values were increased, suggesting that PS/Wood degradation slowed down at the second pyrolysis stage. Decreases in | R max | and delays in T max were in favor of reduced C-C bond cleavages to allow the formation of more stable char residues during the thermal degradation of wood [ 58 ]. At the third stage, further oxidation of PS/Wood was markedly reduced.…”

Section: Resultsmentioning

confidence: 99%

Construction of a Phytic Acid–Silica System in Wood for Highly Efficient Flame Retardancy and Smoke Suppression

et al. 2021

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The intrinsic flammability of wood restricts its application in various fields. In this study, we constructed a phytic acid (PA)–silica hybrid system in wood by a vacuum-pressure impregnation process to improve its flame retardancy and smoke suppression. The system was derived from a simple mixture of PA and silica sol. Fourier transform infrared spectroscopy (FTIR) indicated an incorporation of the PA molecules into the silica network. Thermogravimetric (TG) analysis showed that the system greatly enhanced the char yield of wood from 1.5% to 32.1% (in air) and the thermal degradation rates were decreased. The limiting oxygen index (LOI) of the PA/silica-nanosol-treated wood was 47.3%. Cone calorimetry test (CCT) was conducted, which revealed large reductions in the heat release rate and smoke production rate. The appearance of the second heat release peak was delayed, indicating the enhanced thermal stability of the char residue. The mechanism underlying flame retardancy was analyzed by field-emission scanning electron microscope coupled with energy-dispersive spectroscopy (SEM-EDS), FTIR, and TG-FTIR. The improved flame retardancy and smoke-suppression property of the wood are mainly attributed to the formation of an intact and coherent char residue with crosslinked structures, which can protect against the transfer of heat and mass (flammable gases, smoke) during burning. Moreover, the hybrid system did not significantly alter the mechanical properties of wood, such as compressive strength and hardness. This approach can be extended to fabricate other phosphorus and silicon materials for enhancing the fire safety of wood.

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“…The selective cleavage of sp 3 -sp 3 carbon-carbon (C-C) bonds is a major challenge in organic chemistry, and has recently emerged as a critical step in plastic waste deconstruction and biomass valorization. [1][2][3][4][5][6] However, the inertness of the Csp3-Csp3 linkages hinders the selective and energy-efficient bond scission in these substrates. [7][8][9] Indeed, Csp3-Csp3 bond activation is difficult due to several thermodynamic and kinetic constraints, [10][11][12][13][14] including high bond dissociation energies (BDEs) of ~90 kcal mol −1 , 10 steric inaccessibility caused by surrounding C-H bonds, and unfavorable orbital directionality towards cleavage which requires the rotation of two carbon sp 3 orbitals.…”

Section: Introductionmentioning

confidence: 99%

Breaking C–C Bonds via Electrochemically Mediated Hydrogen Atom Transfer Reactions

Yan¹,

Shi²,

Beckham³

et al. 2021

Preprint

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Cleaving inert sp3-sp3 carbon-carbon (C-C) bonds selectively remains a major challenge in organic chemistry and a main bottleneck in the chemical upcycling of recalcitrant polyolefin waste. Here, we present an electrochemical strategy using redox mediators to activate and break C-C bonds at room temperature and ambient pressure. Specifically, we use N-hydroxyphthalimide (NHPI) as a redox mediator that undergoes electrochemical oxidation to form the <a>phthalimide-N-oxyl (PINO) radical </a>to initiate hydrogen atom transfer (HAT) reactions with benzylic C-H bonds. The resulting benzylic carbon radical is readily captured by molecular oxygen to form a peroxy radical that decomposes into oxygenated C-C bond-scission fragments. This indirect, mediated approach for Csp3-Csp3 bond cleavage reduces the oxidation potential by > 1.2 V compared to the direct oxidation of the substrate, thereby eliminating deleterious side reactions, such as solvent oxidation, that may occur at high potentials. Studies with a bibenzyl model compound revealed a bifurcated reaction pathway following the initial HAT step. At a bibenzyl conversion of 61.0%, the C-C bond cleavage pathway generates benzaldehyde and benzoic acid products at 38.4% selectivity, and the C-H bond oxygenation pathway leads to 1,2-diphenylethanone and benzil products at 39.2% selectivity. Changes in reaction selectivity were investigated with various model compounds, including bibenzyl, 1,3-diphenylpropane, 1,4-diphenylbutane, and their derivatives. Product selectivity is correlated with the C-C bond strength of the reactant, with weaker C-C bonds favoring the C-C bond cleavage pathway. We also evaluated the mediated oxidation of oligomeric styrene (Mn = 510 Da, OS510) which were converted into oxygenated products. Lastly, proof-of-concept depolymerization of polystyrene (PS, ~10,000 Da) into oxygenated monomers, dimers, and oligomers was demonstrated using NHPI-mediated oxidation.

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Microwave-Assisted Catalytic Cleavage of C–C Bond in Lignin Models by Bifunctional Pt/CDC-SiC

Cited by 23 publications

References 38 publications

Electrochemical Activation of C−C Bonds through Mediated Hydrogen Atom Transfer Reactions

Electrochemical Activation of C−C Bonds through Mediated Hydrogen Atom Transfer Reactions

Construction of a Phytic Acid–Silica System in Wood for Highly Efficient Flame Retardancy and Smoke Suppression

Breaking C–C Bonds via Electrochemically Mediated Hydrogen Atom Transfer Reactions

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