Wet oxidation of lignin model compounds and acetic acid production

Suzuki, Hiroo; Cao, Jianxun; Jin, Fangming; Kishita, Atsushi; Enomoto, Heiji; Moriya, Tsuyoshi

doi:10.1007/s10853-006-4653-9

Cited by 48 publications

(45 citation statements)

References 8 publications

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“…In fact, vanillin is one of the low-molecular-weight chemicals produced industrially in large quantities from technical lignins by alkaline oxidation in air [2,81]. The possibility of acetic acid production by wet oxidation of lignin has also been studied using model compounds [82]. However, wet oxidation of guaiacol, syringol, and phenol as lignin model compounds resulted in low values of acetic acid yield.…”

Section: Oxidationmentioning

confidence: 99%

Lignin Depolymerization and Conversion: A Review of Thermochemical Methods

2010

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The structure of lignin suggests that it can be a valuable source of chemicals, particularly phenolics. However, lignin depolymerization with selective bond cleavage is the major challenge for converting it into value-added chemicals. Pyrolysis (thermolysis), gasification, hydrogenolysis, chemical oxidation, and hydrolysis under supercritical conditions are the major thermochemical methods studied with regard to lignin depolymerization. Pyrolytic oil and syngases are the primary products obtained from pyrolysis and gasification. A significant amount of char is also produced during pyrolysis. Thermal treatment in a hydrogen environment seems very promising for converting lignin to liquid fuel and chemicals like phenols, while oxidation can produce phenolic aldehydes. Reaction severity, solvents, and catalysts are the factors of prime importance that control yield and composition of the product. IntroductionThe depleting stocks of fossil fuels and the growing concern over the excessive emission of greenhouse gases have forced researchers to investigate renewable, abundant and comparably cleaner alternatives to liquid fuels and chemicals produced from petroleum [1][2][3]. Biomass appears to be a promising alternative and a renewable source for fuels and chemicals. Significant achievements have already been made in the production of ethanol fuel from biomass, primarily starch and sugarrich components. However, research on second-generation bioethanol is focused on a more abundant [4,5] and often relatively cheap [6][7][8] biomass feedstock known as lignocellulosic biomass. Lignocellulosic biomass consists of three basic components: cellulose, hemicellulose, and lignin. Cellulose is a linear polymer of glucose consisting of parts with crystalline structure and parts with amorphous structure [9], while hemicellulose is an amorphous, heterogeneously branched polymer of pentoses and hexoses, mainly xylose, arabinose, mannose, galactose, and glucose. Lignin is an amorphous and highly branched polymer of phenylpropane units, which can account for up to 40 % of the dry biomass weight [10]. The concept of a biorefinery that integrates processes and technologies for biomass conversion demands efficient utilization of all three components [11]. Most of the biorefinery schemes, however, are focused on utilizing easily convertible fractions while lignin remains relatively underutilized to its potential [11]. The lignocellulosics-to-ethanol process makes use of the cellulose and hemicelluloses, leaving lignin as waste. In addition, pulp and paper refineries also generate huge amounts of lignin. Presently, lignin is being utilized as a low-grade boiler fuel to provide heat and power to the process [3]. However, the chemical structure of lignin suggests that it may be a good source of valuable chemicals if it could be broken into smaller molecular units [7].Several studies have been done to convert lignin to more value-added products. These include attempts to convert lignin to liquid fuel additives and commercially important chem...

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Section: Oxidationmentioning

confidence: 99%

Lignin Depolymerization and Conversion: A Review of Thermochemical Methods

2010

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“…10,11 More recently, Stahl and co-workers showed that targeted oxidation of enzymatically extracted lignin could dramatically increase the yield of monomers obtained during depolymerization by formic acid. Wet oxidation under hydrothermal conditions has shown that simple compounds such as acetic acid could be produced from lignin.…”

Section: Textmentioning

confidence: 99%

Lignin monomer production integrated into the γ-valerolactone sugar platform

Luterbacher

Azarpira

Motagamwala

et al. 2015

Energy Environ. Sci.

230

198

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We demonstrate an experimental approach for upgrading lignin that has been isolated from corn stover via biomass fractionation using γ-valerolactone (GVL) as a solvent. This GVL-based approach can be used in parallel with lignin upgrading to produce soluble carbohydrates at high yields (≥70%) from biomass without the use of enzymes, ionic liquids, or concentrated acids. The lignin was isolated after an initial hydrolysis step in which corn stover was treated in a high-solids batch reactor at 393 K for 30 min in a solvent mixture consisting of 80 wt% GVL and 20 wt% water. Lignin was isolated by precipitation in water and characterized by 2D HSQC NMR, showing that the extracted lignin was similar to native lignin, which can be attributed to the low acid level and the low extraction temperatures that are achievable using GVL as a solvent. This lignin was upgraded using a two-stage hydrogenolysis process over a Ru/C catalyst. The isolated lignin was first dissolved to form a mixture of 10% lignin, 80% THF, 8.5% H 3 PO 4 and 1.5% H 2 O, and treated at 423 K under hydrogen. The THF was removed by evaporation and replaced with heptane, forming a biphasic mixture. This mixture was then treated at 523 K in the presence of Ru/C and H 2 . The resulting heptane phase contained soluble lignin-derived monomers corresponding to 38% of the carbon in the original lignin. By adding 5% methanol during the second catalytic step, we produced additional monomers containing methyl esters and increased carbon yields to 48%. This increase in yield can be attributed to stabilization of carboxylic acid intermediates by esterification. The yield reported here is comparable to yields obtained with native lignin and is much higher than yields obtained with lignin isolated by other processes. These results suggest that GVLbased biomass fractionation could facilitate the integrated conversion of all three biomass fractions. Broader contextLignocellulosic biomass represents an attractive source of renewable carbon and could be used as a feedstock to substitute fossil-based fuels and chemicals. In addition, lignocellulosic biomass comprises non-edible plants that can grow on marginal lands and thus compete minimally with food production. In the context of increasing environmental issues related to climate change and because of increasing petroleum costs due to diminishing fossil reserves, it is urgent to find sustainable carbon-based substitutes to petroleum. However, growing, harvesting and processing biomass is often costly. Because of the expense of the raw material, the yield for conversion of biomass to useful products must be maximized. Lignocellulosic biomass typically contains about 50-70% polysaccharides (cellulose and hemicellulose) and 15-30% lignin by weight. Lignin is an irregular polymer composed of phenolic subunits. Given the relative uniformity of the carbohydrate polymers compared to lignin and the well-established chemical and biological upgrading pathways developed for sugar production and processing, much research and develop...

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“…According to the authors, this two-stage process maximizes acetic acid production, with a good yield of 40 % from a carbon base. Suzuki et al [19] have used lignin model compounds to study the possibility of acetic acid production by wet oxidation. However, wet oxidation of guaiacol, syringol, and phenol as lignin model compounds resulted in low acetic acid yields [19].…”

Section: Introductionmentioning

confidence: 99%

Alkaline Partial Wet Oxidation of Lignin for the Production of Carboxylic Acids

et al. 2015

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The production of carboxylic acids by partial wet oxidation of alkali lignin was studied experimentally. The factors influencing the different types of products, their yields and concentrations were investigated. Formic, acetic, succinic, oxalic, and glutaconic acid were the main identified products. Both the temperature and oxygen partial pressure are shown to have direct effects on the product yields whereas the lignin concentration has an indirect effect. At low lignin concentrations, the yield of products was relatively high. However, at higher concentrations, the yield decreased. By measuring the lignin molecular weight distributions, it is shown that this decrease is linked to repolymerization/condensation reactions of lignin fragments which compete with oxidative lignin depolymerization.

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Wet oxidation of lignin model compounds and acetic acid production

Cited by 48 publications

References 8 publications

Lignin Depolymerization and Conversion: A Review of Thermochemical Methods

Lignin Depolymerization and Conversion: A Review of Thermochemical Methods

Lignin monomer production integrated into the γ-valerolactone sugar platform

Alkaline Partial Wet Oxidation of Lignin for the Production of Carboxylic Acids

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