•93.44% of the lignin was converted into liquid product at 320°C for 6h.•Maximally 67.58% of monomeric and dimeric degradation products was obtained.•The HHV of liquid product was increased from ...27.54MJ/kg to 34.40MJ/kg.•The char formation was almost eliminated at 320°C for 6h.
In this study, a novel catalyst, S2O82−-KNO3/TiO2, which has active acidic and basic sites, was prepared and used in lignin hydrocracking with a co-catalyst, Ru/C. Ru/C is an efficient hydrogenation catalyst and S2O82−-KNO3/TiO2 is a dual catalyst, which could efficiently degrade lignin. This catalytic hydrogenation system can reduce solid products to less than 1%, while giving a high liquid product yield of 93%. Catalytic hydrocracking of kraft lignin at 320°C for 6h gave 93% liquid product with 0.5% solid product. Most of this liquid product was soluble in petroleum ether (60% of 93%), which is a clear liquid and comprises mainly of monomeric and dimeric degradation products. These results demonstrated that the combination of the two catalysts is an efficient catalyst for liquefaction of lignin, with little char formation (∼1%). This concept has the potential to produce valuable chemicals and fuels from lignin under moderate conditions.
Kraft lignin as an emerging renewable feedstock can be used to produce fuels, chemicals, and materials. Hardwood kraft lignin bears intrinsic variation due to wood species and the isolation process. ...The structure and property variation of hardwood kraft lignin could introduce new challenges and opportunities for its application. To better understand such variation, seven kraft lignin samples, originated from southern mixed hardwood (North America), northern mixed hardwood (North America), and Asian mixed hardwood, were isolated from commercial kraft pulping black liquor using both LignoBoost and LignoForce processes. Modern analytical techniques were used to elucidate the characteristics of mixed hardwood kraft lignins, including chemical composition, molecular weight, functional groups, and thermal properties. All lignin samples had a lignin content over 90% (92% to 96%) with one exception, which was northern mixed hardwood kraft lignin with 86% of lignin content and 6% polysaccharides. The elemental and methoxy analyses revealed the expected variation of hardwood kraft lignins with the methoxy content ranging from 0.85 to 1.20 per C9 unit. The weight average molecular weight exhibited a higher variation (from 4800 to 1895 Da) with a descending order of southern mixed hardwood kraft lignins, northern mixed hardwood lignins, and Asian mixed hardwood lignins. The aliphatic hydroxy groups ranged from 14 to 25 per 100 C9 units, and phenolic hydroxy groups ranged from 65 to 112 per 100 C9 units. The catecholic group content ranged from 12 to 34 per 100 C9 units, which is higher than softwood kraft lignin. The lignins isolated from the rapid displacement heating (RDH) pulping process were more condensed than from the regular kraft pulping process. 2D HSQC and quantitative
13
C NMR revealed the drastic structure change upon kraft pulp with the low abundance of native lignin linkages and formation of new interunit linkages, such as stilbene, enol ethers, and 1-1'/5'. The S/G ratio was calculated using 2D HSQC spectra correcting for signal shift caused by the catecholic groups.
Display omitted
•Optimized first of two-stage process to jet fuel-range hydrocarbons from lignin.•Three well-characterized technical lignins depolymerized using three customized catalysts.•Ru ...suppressed coking and promoted hydrogenolysis of pine kraft lignin compared to Co.•Sweetgum biorefinery lignin efficiently fragmented over dual acid-base catalyst.•Ru-Zn converted 79% hardwood kraft lignin to oligomers ideal for hydrotreatment.
One-pot conversion of technical lignins to jet fuel is limited by recondensation of unstable intermediates. A two-stage process that first generates stabilized fragments by reductive depolymerization, then upgrades oligomers to hydrocarbons may increase yield. Insights into factors affecting initial depolymerization of industrially relevant lignins were revealed, whereas many studies have focused on upgrading bio-oil or model compounds. Feedstocks, catalysts, and process conditions were varied to identify effects on product composition. Hydrogen and temperature synergistically suppressed coking during pine kraft depolymerization to increase monomer production. Ruthenium was more effective than cobalt at limiting solid residue and improving liquid product yield by promoting hydrogenation and hydrogenolysis. Besides ruthenium, a strong acid-base catalyst effectively deconstructed hardwood biorefinery lignin, targeting alkyl-aryl ether bonds. Ruthenium and zinc converted hardwood kraft lignin to oligomers most suitable for upgrading to jet fuel-range hydrocarbons based on yield (79 % on dry lignin), weight-average molecular weight (1290 g/mol), and chemical structure.
Display omitted
•Maximally 64.5% of monomeric and dimeric degradation products was obtained.•The HHV of liquid product was increased from 24.9 MJ/kg to 32.0 MJ/kg.•Ni/DeAl-beta catalyst exhibits good ...recyclability in lignin depolymerization.
In this study, a novel modified nickel/H-beta (Ni/DeAl-beta) catalyst, which has active acidic sites and hydrogen binding sites, was prepared and used to produce liquefied fuel from lignin. The bifunctional Ni/DeAl-beta catalyst efficiently converted kraft lignin into liquefied fuel due to the synergistic effect of aluminum Lewis acid sites and nickel hydrogen binding sites. At a nickel content of 0.6 mmol/gzeolite, the Ni/DeAl-beta catalyst gave a high liquid product yield of 88.6% at 300 °C for 36 h. Most of the liquid product was dissolved in petroleum ether (73% of 88.6%), which was mainly composed of monomeric and dimeric degradation products. Under these conditions, the higher heating values (HHV) increased from 24.9 MJ/kg for kraft lignin to 32.0 MJ/kg for the liquid product. These results demonstrated the bifunctional Ni/DeAl-beta catalyst could be an efficient catalyst for lignin to liquefied fuel conversion.
Lignin Structural Variation in Hardwood Species Santos, Ricardo B; Capanema, Ewellyn A; Balakshin, Mikhail Yu ...
Journal of agricultural and food chemistry,
05/2012, Volume:
60, Issue:
19
Journal Article
Peer reviewed
A comprehensive lignin structure analysis of ten industrially relevant hardwood species is presented. Milled wood lignin (MWL) was isolated from each species using a modified protocol and all milled ...wood lignin preparations were analyzed through quantitative 13C NMR spectroscopy, elemental analysis, methoxyl analysis, sugar analysis, and nitrobenzene oxidation. Nitrobenzene oxidation and ozonation were carried out on extractive-free wood, alkali-extracted wood, milled wood lignin, and alkali-extracted lignin. Milled wood lignin isolated by the modified protocol was found to be representative of the total lignin in alkali-extracted wood. Significant variations in lignin structures, such as syringylpropane/guaiacylpropane ratio (S/G ratio), arylglycerol-β-aryl ether (β-O-4), degree of condensation, and elemental and methoxyl contents, were found among the hardwood species studied. These structural variations among species appear to be correlated to a single factor, the syringyl/guaiacyl ratio. A new method to predict the S/G ratio of total lignin in wood was developed, using a calibration line established by the syringaldehyde/vanillin (S/V) ratio (nitrobenzene oxidation) and the S/G ratio (13C NMR) of milled wood lignin (MWL).
The domestication of forest trees for a more sustainable fiber bioeconomy has long been hindered by the complexity and plasticity of lignin, a biopolymer in wood that is recalcitrant to chemical and ...enzymatic degradation. Here, we show that multiplex CRISPR editing enables precise woody feedstock design for combinatorial improvement of lignin composition and wood properties. By assessing every possible combination of 69,123 multigenic editing strategies for 21 lignin biosynthesis genes, we deduced seven different genome editing strategies targeting the concurrent alteration of up to six genes and produced 174 edited poplar variants. CRISPR editing increased the wood carbohydrate-to-lignin ratio up to 228% that of wild type, leading to more-efficient fiber pulping. The edited wood alleviates a major fiber-production bottleneck regardless of changes in tree growth rate and could bring unprecedented operational efficiencies, bioeconomic opportunities, and environmental benefits.
•Dilute hydrochloric acid followed by Fenton oxidation is an effective pretreatment process.•Fenton oxidation pretreatment has significant effect on lignin removal under mild conditions.•Fenton ...oxidation pretreatment can decrease enzyme dosage with high sugar recovery.
A two-stage pretreatment process is proposed in this research in order to improve sugar recovery from corn stover. In the proposed process, corn stover is hydrolyzed by dilute hydrochloric acid to recover xylose, which is followed by a Fenton reagent oxidation to remove lignin. 0.7wt% dilute hydrochloric acid is applied in the first stage pretreatment at 120°C for 40min, resulting in 81.0% xylose removal. Fenton reagent oxidation (1g/L FeSO4·7H2O and 30g/L H2O2) is performed at room temperature (about 20°C) for 12 has a second stage which resulted in 32.9% lignin removal. The glucose yield in the subsequent enzymatic hydrolysis was 71.3% with a very low cellulase dosage (3FPU/g). This two-stage pretreatment is effective due to the hydrolysis of hemicelluloses in the first stage and the removal of lignin in the second stage, resulting in a very high sugar recovery with a low enzyme loading.
A resorcinol-formaldehyde resin carbon (RFC) catalyst with a well-developed, ordered, mesoporous framework was prepared using a soft template method at room temperature. The carbon was sulfonated in ...water using sulfanilic acid under mild atmospheric conditions. The sulfonated RFC (S-RFC) was characterized by N 2 adsorption–desorption, elemental analysis, TEM, XPS, and FT-IR. It was determined that S-RFC is an efficient solid acid catalyst for furfural production from xylose and corn stover in γ-valerolactone (GVL). The effects of reaction time, reaction temperature, catalyst loading, substrate dosage and water concentration were investigated. 80% furfural yield and 100% xylose conversion were obtained from xylose at 170 °C in 15 min with 0.5 g catalyst. Comparatively, 68.6% furfural yield was achieved from corn stover at 200 °C in 100 min when using 0.6 g catalyst. Since there was no discernable decrease in furfural yield after multiple conversions utilizing the same catalyst, the recyclability of the catalyst is considered good.
•Autohydrolysis severity affects the chemical composition of pretreated wheat straw.•The enzymatic hydrolysis efficiency was strongly related to pretreatment severity.•Mechanical refining improved ...enzymatic hydrolysis efficiency of wheat straw.•The levels of sugar recovery are comparable to other pretreatment methods.
Wheat straw was pretreated using an autohydrolysis process with different temperatures (160–200°C) and times (10–20min) in order to allow the recovery of hemicellulose in the filtrate and help open up the structure of the biomass for improved accessibility of enzymes during enzymatic hydrolysis. Autohydrolysis at 190°C for 10min provided the highest overall sugar (12.2/100g raw wheat straw) in the autohydrolysis filtrate and recovered 62.3% of solid residue. Before enzymatic hydrolysis, the pulps obtained from each pretreatment condition were subjected to a refining post-treatment to improve enzyme accessibility. Enzymatic hydrolysis was performed for all the pretreated solids with and without refining post-treatment at the enzyme loadings of 4 and 10FPU/g oven dry substrate for 96h. A total of 30.4g sugars can be recovered from 100g wheat straw at 180°C for 20min with 4FPU/g enzyme charge.
PDF
