Lignin Basis Research Articles

Comparative study of the electrochemical characteristics of activated carbons from biomass waste as symmetrical supercapacitor

Surface, structural and electrochemical analysis of a series of activated carbons obtained from biomass waste was carried out. It has been shown that the proportion of surface oxygen has a significant dependence on the type of feedstock. Minimum oxygen values are shown for activated carbons from precursors obtained as a result of deep processing of cellulose. Structural analysis carried out by two methods showed that the main differences between activated carbons are concentrated in the mesopore region, while the volumes of micropores for all samples are close to each other. For two samples with maximum surface areas, studies of the hydrophobic properties of the surface were carried out. Comparison of structural data with electrochemical impedance results showed a high correlation between mesopore surface area data and the effective conductivity of electrodes in the cells of a symmetrical supercapacitor. A comparison was made of the specific capacitance values obtained by cyclic voltammetry, impedance measurement and galvanostatic discharge. A study of the effect of charging time on the energy characteristics of cells showed an abnormally high power of an electrode made on the basis of lignin. The types of materials applicable to electrodes in electric energy storage devices have been determined.

Microwave Depolymerization of Lignin via Dynamic Vapor Flow Reaction System: HCOOH as Pretreatment Solvent or Reforming Solvent Vapor.

Different forms of HCOOH in the depolymerization system play an important role in governing the monomeric products from lignin. We reported two strategies for the introduction of HCOOH to enrich the monophenols from kraft lignin by microwave-assisted depolymerization. The reaction of lignin models showed that HCOOH was in favor of the cleavage of C-O bonds (β-O-4 typically) and partial C-C bonds (Cα-Cβ). Subsequently, Microwave-assisted depolymerization of lignin with two strategies was conducted via a designed dynamic vapor flow reaction system. Strategy A with HCOOH as pretreatment solvent showed excellent monophenols enrichment with total mass yields of 193.71 mg/g (lignin basis). Strategy B using HCOOH as reforming solvent vapor significantly increased the monophenols selectivity. It presented unique reforming and upgrading performance by generating catechol (42.59 mg/g, lignin basis) and homovanillic acid (17.58 mg/g, lignin basis). This study provided potential strategies for the efficient conversion of kraft lignin into high-value platform chemicals.

Lignin Hydrogenolysis: Phenolic Monomers from Lignin and Associated Phenolates across Plant Clades.

The chemical complexity of lignin remains a major challenge for lignin valorization into commodity and fine chemicals. A knowledge of the lignin features that favor its valorization and which plants produce such lignins can be used in plant selection or to engineer them to produce lignins that are more ideally suited for conversion. Sixteen biomass samples were compositionally surveyed by NMR and analytical degradative methods, and the yields of phenolic monomers following hydrogenolytic depolymerization were assessed to elucidate the key determinants controlling the depolymerization. Hardwoods, including those incorporating monolignol p-hydroxybenzoates into their syringyl/guaiacyl copolymeric lignins, produced high monomer yields by hydrogenolysis, whereas grasses incorporating monolignol p-coumarates and ferulates gave lower yields, on a lignin basis. Softwoods, with their more condensed guaiacyl lignins, gave the lowest yields. Lignins with a high syringyl unit content released elevated monomer levels, with a high-syringyl polar transgenic being particularly striking. Herein, we distinguish phenolic monomers resulting from the core lignin vs those from pendent phenolate esters associated with the biomass cell wall, acylating either polysaccharides or lignins. The basis for these observations is rationalized as a means to select or engineer biomass for optimal conversion to worthy phenolic monomers.

Stable Oligomer Formation from Lignin by Pyrolysis of Softwood in an Aprotic Solvent with a Hydrogen Donor.

Pyrolysis of Japanese cedar wood in diphenoxybenzene (an aprotic solvent) with a hydrogen donor was investigated between 270–380 °C. Under these conditions, re‐condensation via radical and quinone methide intermediates was efficiently suppressed and a thermally stable oligomer was obtained. The oligomer was stable even after the treatment time was extended. Yields of lignin‐derived products at 270 °C were limited to approximately 20 wt %, but increased to >80 wt % (lignin basis) at the higher temperatures. The oligomer yield increased directly with the extent of the cellulose degradation at 350 °C. Based on the NMR analysis results, the ether bonds in lignin were largely cleaved, but condensed linkages such as β‐aryl and β‐β and 5‐5’ types remained. The γ‐hydroxypropyl group was identified as a typical side chain, formed by hydrogenation of the double bond of a coniferyl alcohol‐type structure.

One-Pot Catalytic Conversion of Lignin-Derivable Guaiacols and Syringols to Cyclohexylamines.

Cyclic primary amines are elementary building blocks to many fine chemicals, pharmaceuticals, and polymers. Here, a powerful one-pot Raney Ni-based catalytic strategy was developed to transform guaiacol into cyclohexylamine using NH3 (7 bar) and H2 (10 bar) in up to 94 % yield. The methodology was extendable to the conversion of a wider range of guaiacols and syringols into their corresponding cyclohexylamines. Notably, a crude bio-oil originating from the reductive catalytic fractionation of birch lignocellulose was transformed into a product mixture rich in 4-propylcyclohexylamine, constituting an interesting case of catalytic funneling. The isolated yield of the desired 4-propylcyclohexylamine reached as high as 7 wt % (on lignin basis). Preliminary mechanistic studies pointed at the consecutive occurrence of three key catalytic transformations, namely, demethoxylation, hydrogenation, and amination.

Fully lignocellulose-based PET analogues for the circular economy

Polyethylene terephthalate is one of the most abundantly used polymers, but also a significant pollutant in oceans. Due to growing environmental concerns, polyethylene terephthalate alternatives are highly sought after. Here we present readily recyclable polyethylene terephthalate analogues, made entirely from woody biomass. Central to the concept is a two-step noble metal free catalytic sequence (Cu20-PMO catalyzed reductive catalytic fractionation and Raney Ni mediated catalytic funneling) that allows for obtaining a single aliphatic diol 4-(3-hydroxypropyl) cyclohexan-1-ol in high isolated yield (11.7 wt% on lignin basis), as well as other product streams that are converted to fuels, achieving a total carbon yield of 29.5%. The diol 4-(3-hydroxypropyl) cyclohexan-1-ol is co-polymerized with methyl esters of terephthalic acid and furan dicarboxylic acid, both of which can be derived from the cellulose residues, to obtain polyesters with competitive Mw and thermal properties (Tg of 70–90 °C). The polymers show excellent chemical recyclability in methanol and are thus promising candidates for the circular economy.

Enhancing α-etherification of lignin in Eucalyptus diol pretreatment to improve lignin monomer production

In this work, α-etherification of lignin in diol pretreatment was selectively enhanced at mild temperature for lignin isolation and subsequent valorisation. More than 90 % of lignin was removed from Eucalyptus at 120 °C in diol (ethylene glycol and 1,4-butanediol) pretreatment, resulting in >90 % cellulose conversion in 24 h at 7.5 FPU/g glucan cellulase loading. Subsequent catalytic transfer hydrogenolysis of the isolated lignins with Ru/C in ethanol gave 15 % monomer yield on native lignin basis, 5 times of that from the technical ethanol process (170 °C). HSQC NMR analysis revealed that diol pretreated lignin (120 °C) contained ∼23 % α-etherified β–O–4 interunit bonds, indicating that lignin degradation (i.e. cleavage of β–O–4 bonds) was suppressed via etherification by grafting a hydroxyl group at the α position of lignin. This finding was consistent with the isolated lignin (120 °C) had less number of phenolic OH and higher molecular weight via31P NMR and GPC analysis. 31P NMR analysis also revealed that diol isolated lignin contained more number of aliphatic OH than ethanol-isolated lignin, which increased lignin solubility and maintained the high yield (>80 %) of isolated lignin from Eucalyptus at 120 °C as expected. In summary, diol pretreatment of woody biomass can effectively isolate more lignin for hydrogenolysis to valued-added monomers without compromising the isolated yield of lignin and hydrolysis yield of remained cellulose.

Lignin depolymerization and monomeric evolution during fast pyrolysis oil upgrading with hydrogen from glycerol aqueous phase reforming

• Upgrading of Bio-oil with hydrogen from glycerol aqueous phase reforming. • 34.6% of lignin derived compounds were converted to hydrocarbon. • Pt/C and H-ZSM-5 catalysts were effective for hydrodeoxygenation reaction. • n-Decane as a co-solvent prevents condensation reaction. • Series of demethoxylation, hydrogenation, and hydrodeoxygenation were observed. A novel approach to Fast Pyrolysis Oil (FPO) upgrading with hydrogen from glycerol aqueous phase reforming (APR) was conducted in a biphasic solution. FPO contains both monomer and polymer compounds which rich in oxygen, giving high acidity and low stability. Hydrogen demanding reaction of depolymerization and hydrodeoxygenation (HDO), often called upgrading, is required to improve FPO properties by converting these compounds to hydrocarbon monomers. APR reaction of glycerol where glycerol is reacted with water to produce hydrogen is one of the renewable choices to obtain hydrogen. Prior to upgrading of FPO, catalyst screening and reaction optimization were studied using phenol as a model compound. Upgrading of FPO with in situ glycerol APR was conducted with Pt/C, facilitating hydrogen production (APR) and utilization (hydrogenation), and H-ZSM-5, facilitating dehydration reaction. n-Decane was added to the reaction as a co-solvent to prevent the condensation of the non-polar fragments of FPO which led to coke formation. Upon upgrading the weight average molecular weight (Mw), polydispersity index (PDI), and oxygen to carbon (O/C) ratio of FPO decreased. The highest hydrocarbon yield (7.7% FPO basis or 34.6% lignin basis) was obtained by combining Pt/C and H-ZSM-5 catalysts with n-decane as a co-solvent. Evidence of progressive depolymerization and sequential demethoxylation, hydrogenation, and deoxygenation during upgrading were observed in the products.

Fast Pyrolysis of Lignin Pretreated with Magnesium Formate and Magnesium Hydroxide

Kraft lignin (Indulin AT) pretreated with magnesium formate and magnesium hydroxide was fast-pyrolyzed in a continuously fed, bench-scale system. To avoid fouling issues typically associated with lignin pyrolysis, a simple laboratory test was used to determine suitable ranges of magnesium hydroxide and formic acid to lignin for feeding without plugging problems. Various feedstock formulations of lignin pretreated with magnesium hydroxide and formic acid were pyrolyzed. For comparison, calcium formate pretreated lignin was also tested. The organic oil yield ranged from 9% to 17% wt % on a lignin basis. Carbon yields in the oil ranged from 10% to 18% wt % on a lignin basis. Magnesium formate pretreatment increased oil yield and carbon yield in the oil up to 35% relative to the higher 1:1 g magnesium hydroxide/g lignin pretreatment. However, a lower magnesium hydroxide pretreatment (0.5:1 g magnesium hydroxide/g lignin) resulted in oil yields and carbon yields in the oils similar to the magnesium formate pretreatments. Magnesium formate pretreatment produced more oil but with a higher oxygen content than calcium formate under the same conditions. The GC-MS analysis of product oils indicated that phenols and aromatics were more prevalent in pyrolyzed magnesium-formate-pretreated lignin.

Biopolymer bindings for casting manufacturing processes on the technological lignin basis

The paper analyzes the problem of using technological lignins to make new bindings for casting manufacturing processes. The reasons, restraining their application in casting manufacture, are considered. The objective (based on the physical nature of the material) and subjective (based on commercial benefit) reasons are presented. The paper considers the perspectives of application of technological lignins by the example of technological lignosulfonates use which is the main representative of the technological lignins family on the Russian market of bindings.

A lignin-first strategy to recover hydroxycinnamic acids and improve cellulosic ethanol production from corn stover

The goal of this research is to develop a partial delignification process for corn stover that simultaneously improves accessibility of enzymes to cellulose and recovers hydroxycinnamic acids (HCA) as a value-added product from the lignin. We recover HCAs from corn stover with a mild base extraction employing sodium hydroxide, ethanol, and water. The total HCA yield was 33.5 wt% on a lignin basis and approximately 6 wt% on a corn stover basis. This partial delignification pretreatment allowed 85 wt% of total available glucose to be recovered by enzymatic hydrolysis using an enzyme loading that is only 10% of the level recommended for recovering sugars from lignocellulosic biomass. Technoeconomic analysis indicates that recovery of HCAs could reduce the selling price of ethanol by $0.26 L-1. That part of the lignin not removed as HCA becomes a co-product of enzymatic hydrolysis suitable for thermochemical processing into additional biofuels and/or chemicals.

Short-Time Hydrothermal Treatment of Poplar Wood for the Production of a Lignin-Derived Polyphenol Antioxidant.

Artificial antioxidants are synthesized from fossil sources and are now widely used in the polymer, food, and cosmetics industries. The gradual depletion of fossil resources makes it practically significant and necessary to produce green antioxidants from renewable lignocellulosic resources. Herein, short-time hydrothermal (STH) treatment was developed for production of lignin-derived polyphenol antioxidants (LPAs) from poplar wood under conditions of high temperature and high pressure. LPA yields from 21.5 to 37.6 % on the basis of lignin in untreated wood were obtained by STH treatments as result of lignin depolymerization at 190-200 °C and 10 MPa in 5-8 min. Depolymerization reactions were confirmed by the much lower molecular weight of LPA (1076 g mol-1 ) than that of native lignin (4094 g mol-1 ). NMR spectroscopy revealed the structural features of lignin in the isolated LPA, namely syringyl and guaiacyl units with well-preserved interunit linkages. A Folin-Ciocalteu assay indicated that each LPA molecule contained 5.4 phenolic hydroxyl groups on average, much more than other technical lignins. The remarkable antioxidant ability of LPA was verified by the radical-scavenging index of 53.5-67.3, much higher than 0.2-11.1 of the commercial antioxidants butylated hydroxytoluene (BHT) and butylated hydroxyanisole (BHA). STH treatment only requires water and heat for production of high-value antioxidant, which provides a green and sustainable method for the utilization of lignocelluloses.

Experimental Technology for the Production of Polymer–Humate Drilling Reagents

The raw materials base of brown coals for the production of heat-resistant polymer–lignite chemical reagents was selected based on a comparison of the technological parameters of water-based drilling fluids treated with various nanomodified powdered complex polymer–lignite chemicals. On the basis of lignin–alkaline reagents, a highly heat-resistant fluid-loss reducer, a complex low-thixotropic thinning agent, a complex inhibitor of shales, clays, and clay minerals, and a stabilizer of unstable clay and argillite deposits were developed.

The evaluation of possibilities of modern level casting bindings on the technological lignin basis practical appliance

Nowadays the ways of overcoming a problem of resource deficit include rationalization of the existing resource potential. In this respect it is expedient to use the secondary products of vegetable raw material processing due to expansion of lignosulfonate materials application.

Promising bulk production of a potentially benign bisphenol A replacement from a hardwood lignin platform

A unique, bulk-scale lignin-to-chemicals valorisation chain converts economically feasible 4-n-propylsyringol into low-oestrogenic bisphenols suitable for aromatic polyesters.

Efficiency Estimation and Improvement of the 1,3-Butadiene Production Process from Lignin via Syngas through Process Simulation

Three processes for the production of 1,3-butadiene (1,3-BD) from lignin via syngas were proposed, and their 1,3-BD yields and input energy, such as electric power and heat loads, were estimated through process simulation. These processes consisted of lignin gasification, conversion of syngas to light olefins (LOs) via (1) dimethyl ether (DME), (2) methanol, or (3) direct synthesis, and isomerization/dehydrogenation of n-C4H8. The process capacity was 200 t/d on a wet lignin basis. The electric power was largely dependent on the process (4777–6073 kWe), while the minimum external heat was 97 kW, according to pinch analysis. When each reaction proceeded ideally, the process featuring the conversion of syngas to LOs via DME was the most promising. The high electric power (6008 kWe) for the process was attributed to excess N2 production through a cryogenic air separation method. A decrease in the amount of N2 supplied to the DME-to-LOs unit led to a decrease in the electric power to 5381 kWe, and the 1,3-BD ...

Simultaneous catalytic de-polymerization and hydrodeoxygenation of lignin in water/formic acid media with Rh/Al2O3, Ru/Al2O3 and Pd/Al2O3 as bifunctional catalysts

The catalytic solvolysis of 3 lignins of different sources in a formic acid/water media using bifunctional Ru/Al2O3, Rh/Al2O3, Pd/Al2O3 catalysts was explored in a batch set-up at different temperatures and reaction times (340–380°C and 2–6h, respectively). Blank experiments using only gamma–alumina as catalysts and non-catalyzed experiments were also performed and compared with the supported catalysts results. All the supported catalysts significantly improved the oil yields on a lignin basis, with yields up to 91.5wt% using the Ru catalyst. The main components phenol, cresol, guaiacol, methylguaiacol, catechol, ethylcatechol, syringol and o-vanillin are found in different concentrations depending on the catalytic system. The stable Lewis acidity in the alumina support has been found to be active in terms of de-polymerization of lignin, leading to lower average molecular weight oils. In addition, it was found that alumina plays a significant role in the re-polymerization mechanism of the monomers. The effect of the type of lignin on the final oil and solid yields was also established, demonstrating that lignins produced by basic pretreatment of biomass do not show significant increase in oil yield when catalysts on an acid support like alumina are used. The interpretation is that acid conditions are needed for efficient de-polymerisation of the lignin.

The effect of temperature on the catalytic conversion of Kraft lignin using near-critical water

The catalytic conversion of suspended LignoBoost Kraft lignin was performed in near-critical water using ZrO2/K2CO3 as the catalytic system and phenol as the co-solvent and char suppressing agent. The reaction temperature was varied from 290 to 370°C and its effect on the process was investigated in a continuous flow (1kg/h). The yields of water-soluble organics (WSO), bio-oil and char (dry lignin basis) were in the ranges of 5–11%, 69–87% and 16–22%, respectively. The bio-oil, being partially deoxygenated, exhibited higher carbon content and heat value, but lower sulphur content than lignin. The main 1-ring aromatics (in WSO and diethylether-soluble bio-oil) were anisoles, alkylphenols, catechols and guaiacols. The results show that increasing temperature increases the yield of 1-ring aromatics remarkably, while it increases the formation of char moderately. An increase in the yields of anisoles, alkylphenols and catechols, together with a decrease in the yield of guaiacols, was also observed.

Production of carboxymethylcellulose fibers from waste lignocellulosic sawdust using NaOH/NaClO2 pretreatment

In this study, waste lignocellulosic sawdust was converted to carboxymethylcellulose (CMC) by the combination process of an inorganic base (NaOH) and a weak acid (monochloroacetic acid, MCA). Optimum conditions for the pretreatment were studied on the basis of lignin and hemicellulose removal. NaOH and MCA concentration, reaction time, and operating temperature were the parameters studied to acquire the optimized conditions for the production of CMC. Degree of substitution (DS) and solubility were greatly influenced by the changes in the experimental conditions. DS increased on increasing the concentration of NaOH and MCA but the effect was more profound during the NaOH loading. A maximum DS of 0.5 was obtained on the treatment with 20 % NaOH and 20 % MCA concentration at 50 °C, 150 rpm for 4 h. 1.28 g CMC/g cellulose was obtained at the optimized set of conditions. Structural information of cellulose and CMC was obtained using IR spectroscopy and the surface morphology was studied using field emission scanning electron microscopy (FESEM). Carboxymethylcellulose showed lower crystallinity than the native cellulose extracted from sawdust which was studied using X-ray diffraction.

Catalytic depolymerisation and conversion of Kraft lignin into liquid products using near-critical water

A high-pressure pilot plant was developed to study the conversion of LignoBoost Kraft lignin into bio-oil and chemicals in near-critical water (350°C, 25MPa). The conversion takes place in a continuous fixed-bed catalytic reactor (500cm3) filled with ZrO2 pellets. Lignin (mass fraction of approximately 5.5%) is dispersed in an aqueous solution containing K2CO3 (from 0.4% to 2.2%) and phenol (approximately 4.1%). The feed flow rate is 1kg/h (reactor residence time 11min) and the reaction mixture is recirculated internally at a rate of approximately 10kg/h. The products consist of an aqueous phase, containing phenolic chemicals, and a bio-oil, showing an increased heat value (32MJ/kg) with respect to the lignin feed. The 1-ring aromatic compounds produced in the process are mainly anisoles, alkylphenols, guaiacols and catechols: their overall yield increases from 17% to 27% (dry lignin basis) as K2CO3 is increased.