Important Issues and Results from Knut Lundquist's Lignin Research at Chalmers

Lundquist, Knut; Parkås, Jim

doi:10.1080/15222055.2014.915161

Cited by 7 publications

(7 citation statements)

References 1 publication

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“…Due to the in situ evolution of acetic acid, the process may be regarded as autocatalytic . Importantly, under close to pH‐neutral conditions, lignin may undergo solvolysis via radical‐type reactions, in addition to acid‐catalysed transformations …”

Section: Upstream Processingmentioning

confidence: 64%

“…[239] Importantly, under close to pH-neutral conditions,l ignin may undergo solvolysis via radical-type reactions,i na ddition to acidcatalysed transformations. [240] Organosolv processing without added acid is often assumed to afford technical lignins retaining the majority of native b-ether linkages. [241] In this context, in the chemical literature dating from the 1960s to the mid-1990s,ithad been assumed that cleavage of non-cyclic a-O-4 linkages was the primary explanation for solvolytic release of lignin fragments.…”

Section: Reviewsmentioning

confidence: 99%

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Paving the Way for Lignin Valorisation: Recent Advances in Bioengineering, Biorefining and Catalysis

et al. 2016

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Lignin is an abundant biopolymer with a high carbon content and high aromaticity. Despite its potential as a raw material for the fuel and chemical industries, lignin remains the most poorly utilised of the lignocellulosic biopolymers. Effective valorisation of lignin requires careful fine‐tuning of multiple “upstream” (i.e., lignin bioengineering, lignin isolation and “early‐stage catalytic conversion of lignin”) and “downstream” (i.e., lignin depolymerisation and upgrading) process stages, demanding input and understanding from a broad array of scientific disciplines. This review provides a “beginning‐to‐end” analysis of the recent advances reported in lignin valorisation. Particular emphasis is placed on the improved understanding of lignin's biosynthesis and structure, differences in structure and chemical bonding between native and technical lignins, emerging catalytic valorisation strategies, and the relationships between lignin structure and catalyst performance.

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Section: Upstream Processingmentioning

confidence: 64%

Section: Reviewsmentioning

confidence: 99%

Paving the Way for Lignin Valorisation: Recent Advances in Bioengineering, Biorefining and Catalysis

et al. 2016

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“…With this in mind, an interesting approach consists in ‘perturbing’ acid‐catalysed reactions responsible for the release of both lignin oligomers and hemicellulose sugars by neutralisation of the released acetic acid. Under nearly neutral to slightly basic conditions, it is known that the hydrolysis of hemicellulose will be considerably suppressed; however, lignin's β‐ether linkages can still undergo solvolysis through radical reactions . Altogether, the neutralisation of released acetic acid allows for assessing the effect of hemicellulose sugars upon the reactivity of Raney Ni towards ECCL through hydrogen‐transfer reactions.…”

Section: Introductionmentioning

confidence: 99%

The Influence of Hemicellulose Sugars on Product Distribution of Early‐Stage Conversion of Lignin Oligomers Catalysed by Raney Nickel

et al. 2016

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We recently introduced catalytic upstream biorefining, a fractionation process performed on whole lignocellulosic materials, based on the early‐stage conversion of lignin by hydrogen‐transfer reactions (using Raney Ni as the catalyst and 2‐PrOH as a hydrogen‐donor). The process fractionates lignocellulose, isolating lignin as an extensively depolymerised oil, opening up new avenues in the catalytic upgrading of bio‐derived phenolic streams to chemicals and fuels. In addition, highly delignified holocellulose pulps are obtained, holding potential as a feedstock for the production of paper, chemicals, and biofuels. Herein, we report our first results on the chemistry underlying this process under nearly neutral to slightly alkaline conditions achieved by the addition of inorganic bases. This report sheds light on the influence of hemicellulose sugars on the product distribution obtained from the early‐stage catalytic conversion of lignin oligomers released from lignocellulose. The increase in the pH value of the medium suppressed the hydrolysis of xylans. As a result, a dramatic increase in the xylans retention from 10 % (at pH 4.5) up to 60 % (at pH>7.5) was achieved. Interestingly, the pH value of the liquor did not affect the delignification extent of lignocellulose or the absolute content of glucans retained in the holocellulose. By enhancing xylans retention, we provide evidence that hemicellulose sugars decrease the activity of Raney Ni towards full hydrogenation of the aromatic species composing the lignin stream. In fact, the yield of selected cyclohexanols increases from 0.8 % (no added bases) to 4.4 % (added NaOH), whereas the yield of selected phenols decreases from 12.9 % (no added bases) to 7.2 % (added NaOH).

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“…acetic acid, originated from hemicellulose deacetylation). [44][45] Summarised in Figure 5.4 are the initial steps of the reaction network triggered by the acid-catalysed hydrolysis of β-O-4 linkages, which produces Hibbert ketones (HK), as main intermediates. HK may be formed as molecular species (e.g.…”

Section: Processes Occurring On Lignin Dissolved In the Liquormentioning

confidence: 99%

Chapter 5. Early-stage Conversion of Lignin over Hydrogenation Catalysts

Rinaldi¹

2018

Energy and Environment Series

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The deconstruction of lignocellulosic materials producing high-quality pulps together with lignin streams of low molecular weight (Mw) with controlled molecular diversity constitutes the overarching objective of Catalytic Upstream Biorefining (CUB) based on the Early-stage Catalytic Conversion of Lignin (ECCL). The CUB process based on ECCL or, simply, a "lignin first" approach builds on the lignin extraction with organic solvents in the presence of a hydrogenation catalyst under hydrogen pressure or employing an H-donor solvent (e.g. 2-propanol). Subjected to a hydrogenation catalyst, the lignin fragments undergo reductive processes, which decrease their reactivity and propensity to recondensation, directly upon their release from the lignocellulosic matrix. As a result, the isolated lignin fraction is a mixture of compounds of Mw 100-600 Da, with a high content of individual components. Herein, key concepts required for the rational deconstruction of lignocellulose based on ECCL are addressed. Notably, catalysis is now applied to the 'pulping process' itself, opening up new horizons for the realistic valorisation of lignin and full utilisation of lignocellulose via downstream catalytic processing of better-defined lignin streams.

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Important Issues and Results from Knut Lundquist's Lignin Research at Chalmers

Cited by 7 publications

References 1 publication

Paving the Way for Lignin Valorisation: Recent Advances in Bioengineering, Biorefining and Catalysis

Paving the Way for Lignin Valorisation: Recent Advances in Bioengineering, Biorefining and Catalysis

The Influence of Hemicellulose Sugars on Product Distribution of Early‐Stage Conversion of Lignin Oligomers Catalysed by Raney Nickel

Chapter 5. Early-stage Conversion of Lignin over Hydrogenation Catalysts

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