Selective modification of hydroxyl groups in lignin model compounds by ruthenium-catalyzed transfer hydrogenation

Badazhkova, Veronika D; Savela, Risto; Leino, Reko

doi:10.1039/d2dt00267a

Cited by 5 publications

(3 citation statements)

References 27 publications

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“…For example, maximally oxidized C α (i.e., a ketone) yields highly conjugated systems capable of absorbing UV light, lending light-blocking capabilities. 54 On the other hand, a C α hydroxyl group provides a chemical platform to access new small molecules 55 or polymer compounds 56 through judicious chemical modification. The C α oxidation state is sensitive to lignin isolation procedures, whereby an oxidizing acid (e.g., H 2 SO 4 ) can oxidize the naturally occurring alpha-hydroxy group to a ketone.…”

Section: ■ Introductionmentioning

confidence: 99%

Catalytic Transfer Hydrogenolysis of Switchgrass Lignin with Ethanol Using Spinel-Type Mixed-Metal Oxide Catalysts Affords Control of the Oxidation State of Isolated Aromatic Products

Godwin,

Babusci,

Wonderling

et al. 2024

ACS Sustainable Chem. Eng.

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Chemical reductions of lignin are useful to remove oxygen and create product slates that can function as renewable platform molecules for new fuels and chemicals. Catalytic transfer hydrogenolysis (CTH) is an underexplored method to reduce lignin that obviates the use of dangerous and nonrenewable hydrogen gas. While noble metals are used extensively as catalysts for transfer hydrogenation, sustainability remains a major challenge to their deployment. In this work, we synthesized mixed-metal oxides of earth-abundant Co and Ni and characterized the catalysts using powder X-ray diffraction (XRD). Catalyst reactivity for the CTH of acetophenone was also assessed. Among the catalysts tested, spinel NiCo 2 O 4 demonstrated the highest conversion of acetophenone (75%) and the highest selectivity for ethylbenzene (90%); thus, we applied it to valorize switchgrass lignin, extracted under mild operating conditions by cosolvent enhanced lignocellulosic fractionation (CELF). The catalytically depolymerized lignin showed an increase in the number of selectively deoxygenated monomeric compounds. As demonstrated using 2D-NMR spectroscopy, the lignin displayed highly reduced aliphatic carbons, resulting from the catalyst-mediated reduction reaction at the Cα sites. These results are critical to the further development of the lignin-first biorefinery as they demonstrate the use of sustainable catalyst materials and mild transformation conditions to generate and refine a suite of new bioproducts.

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Section: ■ Introductionmentioning

confidence: 99%

Catalytic Transfer Hydrogenolysis of Switchgrass Lignin with Ethanol Using Spinel-Type Mixed-Metal Oxide Catalysts Affords Control of the Oxidation State of Isolated Aromatic Products

Godwin,

Babusci,

Wonderling

et al. 2024

ACS Sustainable Chem. Eng.

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show abstract

“…For example, maximally oxidized Cα (i.e., a ketone) lends light blocking capabilities to lignin, as this affords highly conjugated systems capable of absorbing UV light. 54 On the other hand, a hydroxyl group at Cα affords a chemical platform whereby new small molecules 55 or polymer compounds 56 can be accessed by judicious chemical modification. The oxidation state of Cα is sensitive to lignin isolation procedures, whereby oxidizing acid (e.g., H2SO4) can oxidize the naturally occurring alphahydroxy group to a ketone.…”

Section: Introductionmentioning

confidence: 99%

Catalytic transfer hydrogenolysis of switchgrass lignin with ethanol using spinel-type mixed-metal oxide catalysts affords control of the oxidation state of isolated aromatic products

Godwin,

Babusci,

Wonderling

et al. 2023

Preprint

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Chemical reductions of lignin are useful to remove oxygen and create product slates that can function as renewable platform molecules for new fuels and chemicals. Catalytic transfer hydrogenolysis (CTH) is an underexplored method to conduct reductions of lignin that obviates the use of dangerous and non-renewable hydrogen gas. While noble metals are used extensively as catalysts for transfer hydrogenation, one major challenge for their deployment is related to their sustainability. In this work, we synthesized mixed-metal oxides of earth-abundant Co and Ni. We characterized these catalysts using powder x-ray diffraction (XRD) and tested their reactivity for CTH of acetophenone. Among the catalysts we tested, we noted that the spinel NiCo2O4 demonstrated the highest conversion of acetophenone (75%) and highest selectivity for ethylbenzene (90%), so we applied it to valorization of switchgrass lignin extracted under mild operating conditions by cosolvent enhanced lignocellulosic fractionation (CELF). The catalytically depolymerized lignin showed an increase in selectively deoxygenated monomeric compounds. Using 2D-NMR spectroscopy, we demonstrated the lignin displayed highly reduced aliphatic carbons resulting from the reduction reaction at the Cα sites mediated by our catalyst material. These results are critical to the further development of the lignin-first biorefinery as they demonstrate the use of sustainable catalyst materials and mild transformation conditions to generate and refine a suite of new bioproducts.

show abstract

Section: Introductionmentioning

confidence: 99%

Catalytic transfer hydrogenolysis of switchgrass lignin with ethanol using spinel-type mixed-metal oxide catalysts affords control of the oxidation state of isolated aromatic products

Godwin,

Babusci,

Wonderling

et al. 2023

Preprint

View full text Add to dashboard Cite

Chemical reductions of lignin are useful to remove oxygen and create product slates that can function as renewable platform molecules for new fuels and chemicals. Catalytic transfer hydrogenolysis (CTH) is an underexplored method to conduct reductions of lignin that obviates the use of dangerous and non-renewable hydrogen gas. While noble metals are used extensively as catalysts for transfer hydrogenation, one major challenge for their deployment is related to their sustainability. In this work, we synthesized mixed-metal oxides of earth-abundant Co and Ni. We characterized these catalysts using powder x-ray diffraction (XRD) and tested their reactivity for CTH of acetophenone. Among the catalysts we tested, we noted that the spinel NiCo2O4 demonstrated the highest conversion of acetophenone (75%) and highest selectivity for ethylbenzene (90%), so we applied it to valorization of switchgrass lignin extracted under mild operating conditions by cosolvent enhanced lignocellulosic fractionation (CELF). The catalytically depolymerized lignin showed an increase in selectively deoxygenated monomeric compounds. Using 2D-NMR spectroscopy, we demonstrated the lignin displayed highly reduced aliphatic carbons resulting from the reduction reaction at the Cα sites mediated by our catalyst material. These results are critical to the further development of the lignin-first biorefinery as they demonstrate the use of sustainable catalyst materials and mild transformation conditions to generate and refine a suite of new bioproducts.

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Selective modification of hydroxyl groups in lignin model compounds by ruthenium-catalyzed transfer hydrogenation

Abstract: Selective ruthenium-catalyzed oxidation of lignin diol model compounds and lignin was accomplished by a transfer hydrogenation methodology. The developed procedure allows to selectively oxidize the benzylic secondary alcohol in the...

Cited by 5 publications

References 27 publications

Catalytic Transfer Hydrogenolysis of Switchgrass Lignin with Ethanol Using Spinel-Type Mixed-Metal Oxide Catalysts Affords Control of the Oxidation State of Isolated Aromatic Products

Catalytic Transfer Hydrogenolysis of Switchgrass Lignin with Ethanol Using Spinel-Type Mixed-Metal Oxide Catalysts Affords Control of the Oxidation State of Isolated Aromatic Products

Catalytic transfer hydrogenolysis of switchgrass lignin with ethanol using spinel-type mixed-metal oxide catalysts affords control of the oxidation state of isolated aromatic products

Catalytic transfer hydrogenolysis of switchgrass lignin with ethanol using spinel-type mixed-metal oxide catalysts affords control of the oxidation state of isolated aromatic products

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