Pulp delignification with oxygen and copper(II)-polyimine complexes

Gueneau, Basile; Marlin, Nathalie; Deronzier, Alain; Lachenal, Dominique

doi:10.1515/hf-2013-0134

Cited by 5 publications

(4 citation statements)

References 17 publications

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“…In one study, Korpi et al screened 189 different metal–ligand combinations for the oxidation of veratryl alcohol to veratraldehyde and found that copper complexes of 2,2′-bipyridine and 1,10-phenanthroline were especially active [ 30 , 31 ]. These complexes were also reported to be effective delignification catalysts when H 2 O 2 [ 32 ], O 2 [ 33 , 34 ], or both [ 35 ] were used as the oxidant. All approaches exhibited concurrent cellulose depolymerization that, although detrimental in instances where the cellulose is to be utilized in materials applications in which fiber strength is a crucial property, may prove beneficial if the desired product is monomeric sugars.…”

Section: Introductionmentioning

confidence: 99%

Chemical and structural changes associated with Cu-catalyzed alkaline-oxidative delignification of hybrid poplar

Bansal

Azarpira

et al. 2015

Biotechnol Biofuels

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BackgroundAlkaline hydrogen peroxide pretreatment catalyzed by Cu(II) 2,2′-bipyridine complexes has previously been determined to substantially improve the enzymatic hydrolysis of woody plants including hybrid poplar as a consequence of moderate delignification. In the present work, cell wall morphological and lignin structural changes were characterized for this pretreatment approach to gain insights into pretreatment outcomes and, specifically, to identify the extent and nature of lignin modification.ResultsThrough TEM imaging, this catalytic oxidation process was shown to disrupt cell wall layers in hybrid poplar. Cu-containing nanoparticles, primarily in the Cu(I) oxidation state, co-localized with the disrupted regions, providing indirect evidence of catalytic activity whereby soluble Cu(II) complexes are reduced and precipitated during pretreatment. The concentration of alkali-soluble polymeric and oligomeric lignin was substantially higher for the Cu-catalyzed oxidative pretreatment. This alkali-soluble lignin content increased with time during the catalytic oxidation process, although the molecular weight distributions were unaltered. Yields of aromatic monomers (including phenolic acids and aldehydes) were found to be less than 0.2 % (wt/wt) on lignin. Oxidation of the benzylic alcohol in the lignin side-chain was evident in NMR spectra of the solubilized lignin, whereas minimal changes were observed for the pretreatment-insoluble lignin.ConclusionsThese results provide indirect evidence for catalytic activity within the cell wall. The low yields of lignin-derived aromatic monomers, together with the detailed characterization of the pretreatment-soluble and pretreatment-insoluble lignins, indicate that the majority of both lignin pools remained relatively unmodified. As such, the lignins resulting from this process retain features closely resembling native lignins and may, therefore, be amenable to subsequent valorization.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-015-0300-5) contains supplementary material, which is available to authorized users.

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Section: Introductionmentioning

confidence: 99%

Chemical and structural changes associated with Cu-catalyzed alkaline-oxidative delignification of hybrid poplar

Bansal

Azarpira

et al. 2015

Biotechnol Biofuels

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“…Moreover, integrating the published data on lignin removal and monomeric sugar yields during Cu-AHP pretreatment employing different H 2 O 2 loadings [0, 2, 4, and 6% (w/w)] with the results obtained in this study (Figures and ) indicates a synergistic effect of using both O 2 and H 2 O 2 as co-oxidants during the Cu-catalyzed alkaline–oxidative pretreatment of lignocellulosic biomass. Although there is literature precedence for enhancing O 2 -dependent delignification of pulp by the addition of H 2 O 2 or CuSO 4 , , to our knowledge, there are no published reports describing the simultaneous use of O 2 and H 2 O 2 as co-oxidants during the oxidative pretreatment of lignocellulosic biomass to recover both lignin and monomeric C-5 and C-6 sugars.…”

Section: Discussionmentioning

confidence: 99%

“…Molecular oxygen is a highly appealing oxidant that is widely utilized in the pulp and paper industry as a delignification and bleaching agent . During O 2 delignification of pulp, the free phenolic hydroxyl groups in lignin are ionized by the addition of alkali to generate phenolate ions, which are thought to initiate reactions with O 2 and result in the oxidation and solubilization of lignin into the liquid phase. − During this process, the addition of catalysts such as copper sulfate in the presence or absence of nitrogen-based ligands could further activate oxygen and promote the delignification performance. − Because H 2 O 2 is generally more reactive than O 2 and can generate hydroperoxide anions that oxidize carbonyl groups and cleave lignin aromatic rings, , H 2 O 2 has been utilized to improve the delignification performance of O 2 in pulp bleaching. , Therefore, employing both H 2 O 2 and O 2 as co-oxidants has the potential to improve delignification and the oxidation efficacy of the Cu-AHP pretreatment.…”

Section: Introductionmentioning

confidence: 99%

“…Although there is literature precedence for enhancing O 2 -dependent delignification of pulp by the addition of H 2 O 2 or CuSO 4 ,30,32 to our knowledge, there are no published reports describing the simultaneous use of O 2 and H 2 O 2 as cooxidants during the oxidative pretreatment of lignocellulosic biomass to recover both lignin and monomeric C-5 and C-6 sugars.…”

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Effective Biomass Fractionation through Oxygen-Enhanced Alkaline–Oxidative Pretreatment

Yuan

Klinger

Nikafshar

et al. 2021

ACS Sustainable Chem. Eng.

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The high recalcitrance of plant cell walls is an obstacle for effective chemical or biological conversion into renewable chemicals and transportation fuels. Here, we investigated the utilization of both oxygen (O2) and hydrogen peroxide (H2O2) as co-oxidants during alkaline–oxidative pretreatment to improve biomass fractionation and increase enzymatic digestibility. The oxidative pretreatment of hybrid poplar was studied over a variety of conditions. Employing O2 in addition to H2O2 as a co-oxidant during the two-stage alkaline pre-extraction/copper-catalyzed alkaline hydrogen peroxide (Cu-AHP) pretreatment process resulted in a substantial improvement in delignification relative to using H2O2 alone during the second-stage Cu-AHP pretreatment, leading to high overall sugar yields even at H2O2 loadings as low as 2% (w/w of the original biomass). The presence of H2O2, however, was both critical and synergistic. Performing analogous reactions in the absence of H2O2 resulted in approximately 25% less delignification and 30% decrease in sugar yields. The lignin isolated from this dual oxidant second stage had high aliphatic hydroxyl group content and reactivity to isocyanate, indicating that it is a promising substrate for the production of polyurethanes. To test the suitability of the isolated lignin as a source of aromatic monomers, the lignin was subjected to a sequential Bobbitt’s salt oxidation followed by a formic acid-catalyzed depolymerization process. Monomer yields of approximately 17% (w/w) were obtained, and the difference in yields was not significant between lignin isolated from our Cu-AHP process with and without O2 as a co-oxidant. Thus, the addition of O2 did not lead to significant lignin crosslinking, a result consistent with the two-dimensional heteronuclear single-quantum coherence NMR spectra of the isolated lignin.

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