Unraveling the Role of Formic Acid and the Type of Solvent in the Catalytic Conversion of Lignin: A Holistic Approach

The co-production of xylose, fermentable glucose and β-O-4 linkage-rich lignin through efficiently dismantling sugarcane bagasse

As an "upstream" process in biorefinery, biomass dismantling can dismantle the natural stable structure of lignocellulosic biomass and separate its three major components. To increase the value of the entire biomass by fully utilizing the three main components (cellulose, lignin, and hemicellulose), this study proposes a two-step decomposition system combining formic acid (FA) pretreatment and ethylene glycol-NaOH (EGA) dismantling, aiming to effectively convert sugarcane bagasse into xylose, fermentable glucose, and high-value lignin. In the first step, FA pretreatment removed 79.85 % of hemicellulose at 140 °C for 90 min with 3 % FA. Based on the first step, further combination of EGA dismantling can achieve a hemicellulose removal rate of 92.05 % and a lignin removal rate of 95.90 %. In addition, the solid residue was hydrolyzed by enzymes, and the glucose conversion rate was close to 83.29 % when the cellulase dosage was 10 FPU/g. In addition, the lignin recovered by this system retained 83.62 % of the natural β-O-4 structure, which has the potential to catalyze the formation of aromatic monomers. In summary, this gentle two-step system simultaneously improves the efficiency of lignocellulose decomposition and produces different value-added products, demonstrating the potential for industrial-scale production.

Role of lignin removal on the properties of crude pulp fibers from corn stover via high-temperature formic acid pulping

An effective removal of lignin could reduce the chromogenic groups of lignin in pulp. Herein, corn stover was pulped via the formic acid to investigate the effects of cooking time and temperature on the crude pulp properties. The strong hydrogen ion action of formic acid helped inhibiting both the re-polymerization of degraded lignin molecules and the subsequent adsorption on fiber. The brightness of the crude pulp could reach 51.5 %ISO with the increased lightness and decreased yellowness. The effective lignin removal reduced the residual lignocellulosic bundles in the crude pulp with the increased cooking temperature and time. The lowest lignin content of 3.5 %, α-cellulose content of 94.0 %, and Kappa number of 9.3 were obtained. Meanwhile, the lignin and monosaccharide content in the black liquor could reach 13.3 % and 28.5 %, respectively. The number-average molecular weight of lignin was as low as 818 g/mol. These were helpful to form the hydrogen bonds between fibers, thus enhancing the tensile and burst index of paper sheets. The tensile, burst and tearing indices of the corresponding crude pulp were 47.5 N·m/g, 1.42 kPa·m2/g and 6.53 mN·m2/g, respectively. This work provided valuable practical significance for studying the performance of straw pulp by high temperature formic acid cooking.

Hydrogen-transfer strategy in lignin refinery: Towards sustainable and versatile value-added biochemicals

Lignin, the most prevalent natural source of polyphenols on Earth, offers substantial possibilities for the conversion into aromatic compounds, which is critical for attaining sustainability and carbon neutrality. The hydrogen-transfer method has garnered significant interest owing to its environmental compatibility and economic viability. The efficacy of this approach is contingent upon the careful selection of catalytic and hydrogen-donating systems that decisively affect the yield and selectivity of the monomeric products resulting from lignin degradation. This paper highlights the hydrogen-transfer technique in lignin refinery, with a specific focus on the influence of hydrogen donors on the depolymerization pathways of lignin. It delineates the correlation between the structure and activity of catalytic hydrogen-transfer arrangements and the gamut of lignin-derived biochemicals, utilizing data from lignin model compounds, separated lignin, and lignocellulosic biomass. Additionally, the paper delves into the advantages and future directions of employing the hydrogen-transfer approach for lignin conversion. In essence, this concept investigation illuminates the efficacy of the hydrogen-transfer paradigm in lignin valorization, offering key insights and strategic directives to maximize lignin's value sustainably.

Structural properties and antioxidation activities of lignins isolated from sequential two-step formosolv fractionation

In order to investigate the solubility behavior of lignin in formic acid (FA) solution Phragmites australis biomass was subjected to a sequential two-step formosolv fractionation using 88% FA followed by 70% FA to obtain four specific lignin fractions, designated as IFL-88%, IFSL-70%, IFIL-70% and IFL-EtAc. The structures of the four isolated lignin fractions were successfully characterized by gel permeation chromatography (GPC), Fourier transform infrared (FTIR) spectroscopy, two-dimensional heteronuclear single quantum coherence nuclear magnetic resonance spectroscopy (2D-HSQC NMR), thermogravimetric analysis (TGA), and gas chromatography-mass spectroscopy (GC/MS). Furthermore, the total phenolic content of the four isolated lignin samples was assessed by Folin-Ciocalteu analysis. The data from structural properties revealed that depolymerization of the isolated lignin fractions occurred via β-O-4 cleavage, accompanied by competitive condensation reaction. Interestingly, 70% aqueous FA could separate specific lignin fractions with different antioxidant capacities of ABTS˙+ and DPPH radical scavenging activity. Due to the high total phenolic hydroxyl content (25%) and low molecular weight (Mw = 2760 Da) and polydispersity index (PDI = 1.5), IFL-EtAc lignin showed excellent antioxidant activity at the same concentration of 2.0 mg mL-1 in comparison with three other isolated lignin fractions, and it was even equal to that of commercial antioxidant butylated hydroxytoluene (BHT). These findings are helpful to separate specific lignins with higher value as potential antioxidants by sequential two-step formosolv fractionation in lignin chemistry.

The Consistency of Yields and Chemical Composition of HTL Bio-Oils from Lignins Produced by Different Preprocessing Technologies

This work evaluates the effect of feedstock type and composition on the conversion of lignin to liquid by solvolysis with formic acid as hydrogen donor (LtL), by analyzing the yields and molecular composition of the liquid products and interpreting them in terms of both the type and the preprocessing of the lignocellulosic biomass using chemometric data analysis. Lignin samples of different types and purities from softwood, hardwood, and grasses (rice straw and corn stover) have been converted to bio-oil, and the molecular composition analyzed and quantified using GC-MS. LtL solvolysis was found to be a robust method for lignin conversion in terms of converting all samples into bio-oils rich in phenolic compounds regardless of the purity of the lignin sample. The bio-oil yields ranged from 24–94 wt.% relative to lignin input and could be modelled well as a function of the elemental composition of the feedstock. On a molecular basis, the softwood-derived bio-oil contained the most guaiacol-derivatives, and syringol was correlated to hardwood. However, the connection between compounds in the bio-oil and lignin origin was less pronounced than the effects of the methods for biomass fractionation, showing that the pretreatment of the biomass dominates both the yield and molecular composition of the bio-oil and must be addressed as a primary concern when utilization of lignin in a biorefinery is planned.

Effect of Two-Step Formosolv Fractionation on the Structural Properties and Antioxidant Activity of Lignin

The formosolv fractionation process has been demonstrated to be an effective approach toward lignin recovery as an antioxidant from lignocellulosic biomass. In this study, four lignin fractions, FL-88%, FSL-70%, FIL-70% and FL-EtAc, were isolated from Phragmites australis biomass through two-step formosolv fractionation (88% formic acid delignification followed by 70% aqueous formic acid fractionation). To better understand the structural properties of the lignin obtained from this fractionation process, four isolated lignins were successfully characterized by gel permeation chromatography (GPC), Fourier transform infrared (FT-IR), two-dimensional heteronuclear single quantum coherence nuclear magnetic resonance (2D-HSQC NMR) spectroscopy, thermogravimetric analysis (TGA) and gas chromatograph-mass spectroscopy (GC/MS). It was found that lignin depolymerization via β-O-4 cleavage occurred via a formylation, elimination and hydrolysis mechanism, accompanied by a competitive condensation reaction. Noteworthily, two-step formosolv fractionation can produce specific lignin fractions with different ABTS and DPPH radical scavenging activities. The FL-EtAc fraction with low molecular weight (M_w = 2748 Da) and good homogeneity (PDI = 1.5) showed excellent antioxidant activity, compared with the other three isolated lignin fractions, even equal to that of commercial antioxidant BHT at the same concentration of 2.0 mg·mL⁻¹. These findings are of great help for specific lignin from biomass as a natural antioxidant in the future.

Ni12P5/P-N-C Derived from Natural Single-Celled Chlorella for Catalytic Depolymerization of Lignin into Monophenols

Lignin is exceptionally abundant in nature and is regarded as a renewable, cheap, and environmentally friendly resource for the manufacture of aromatic chemicals. A novel Ni₁₂P₅/P-N-C catalyst for catalytic hydrogenolysis of lignin was synthesized. The catalysts were prepared by simple impregnation and carbonization using the nonprecious metal Ni taken up by the cell wall of Chlorella in Ni(NO₃)₂ solution. There were only two steps in this process, making the whole process very simple, efficient, and economical. Ni₁₂P₅ was uniformly distributed in the catalyst. During the hydrogenolysis of lignin, after 4 h reaction at 270 °C, the yield of bio-oil reached 65.26%, the yield of monomer reached 9.60%, and the selectivity to alkylphenol reached 76.15%. The mixed solvent of ethanol/isopropanol (1:1, v/v) is used as the solvent for the hydrogenolysis of lignin, which not only had excellent hydrogen transferability but also improved the yield of bio-oil, inhibiting the generation of char. No external hydrogen was used, thus avoiding safety issues in hydrogen transport and storage.

Enhanced production of hydrocarbons from lignin isolated from sugarcane bagasse using formic acid induced supercritical ethanol liquefaction followed by hydrodeoxygenation

This study involves the production of hydrocarbons from lignin extracted from sugarcane bagasse using Hydrothermal Liquefaction (HTL) followed by Hydrodeoxygenation (HDO). HTL of the lignin was studied under different solvents-methanol, ethanol and isopropanol in the presence of formic acid as an effective H-donor under varying lignin to solvent ratios (L:S = 1:15,1:30,1:40 g/mL), reaction temperatures (200 °C - 320 °C), reaction times (15, 30, 45,60 min) and ZnCl₂ catalyst concentrations (30, 40, 50, 60 wt%). A maximum of 86% lignin derived phenolics was obtained when ethanol was used as solvent at 250 °C under L:S = 1:30 at 30 min reaction time with 60 wt% ZnCl₂. The lignin-oil was upgraded by HDO process in the presence of Ni/Al₂O₃ catalyst and a maximum hydrocarbon yield of 73.5% was obtained with a HHV value of 48 MJ/kg. The hydrocarbons had excellent properties with a carbon range of C₆-C₁₂ with a purity of 51.2%.

Two-Step Esterification–Hydrogenation of Bio-Oil to Alcohols and Esters over Raney Ni Catalysts

Fast pyrolysis bio-oil is very difficult to be used because of its acidity, instability, high degree of unsaturation, etc. Processes for property upgrading are necessary and required. In this study, three kinds of Raney Ni catalysts were prepared and used to investigate two-step esterification–hydrogenation (TEH) to upgrade the light fraction of bio-oil. The results show that the first step in esterification markedly decreased the content of active compounds such as acids and ketones and aldehydes and increased the content of alcohols and esters (from 10.53% to 47.55%), which improved the bio-oil stability and was favorable for the following hydrogenation reaction. The second step of TEH (hydrogenation) further improved the quality of the bio-oil over Raney Ni and metal-modified Raney Ni catalysts at 140 °C. In particular, the Mo-RN catalyst displayed the best hydrogenation effect, with only 5.44% of acid content, and the stable component content reached 90.16%. This may be attributed to the higher hydrogenation activity from Raney Ni combined with acid MoOx species and the thermal stability of the catalyst. Moreover, the obtained upgraded bio-oil mixture could be used as a solvent for raw bio-oil’s esterification. Therefore, it has the potential to reduce methanol solvent usage and energy consumption for solvent separation during the two-step treatment of raw bio-oil in this context. Compared with the OHE (one-step esterification-hydrogenation) process, THE showed a better performance for raw bio-oil upgrading with higher alcohols and stable compounds, which is more favorable for the saturation and stability of bio-oil’s complex components step by step.

Effect of catalyst and reaction conditions on aromatic monomer yields, product distribution, and sugar yields during lignin hydrogenolysis of silver birch wood

The impact of catalyst choice and reaction conditions during catalytic hydrogenolysis of silver birch biomass are assessed for their effect on aromatic monomer yields and selectivities, lignin removal, and sugar yields from enzymatic hydrolysis. At a reaction temperature of 220 °C with no supplemental H₂, it was demonstrated that both Co/C and Ni/C exhibited aromatic monomer yields of >50%, which were close to the theoretical maximum expected for the lignin based on total β-O-4 content and exhibited high selectivities for 4-propylguaiacol and 4-propylsyringol. Pd/C exhibited a significantly different set of products, and using a model lignin dimer, showed a product profile that shifted upon inclusion of supplemental H₂, suggesting that the generation of surface hydrogen is critical for this catalyst system. Lignin removal during hydrogenolysis could be correlated to glucose yields and inclusion of lignin depolymerizing catalysts significantly improves lignin removal and subsequent enzymatic hydrolysis yields.

Photocatalytic Conversion of Lignin into Chemicals and Fuels

Lignin, an underutilized component of lignocellulosic biomass, is regarded as a rich reservoir for the production of aromatic chemicals and fuels. Despite extensive research in recent years, lignin's potential is far from being fully unlocked. Photocatalysis that uses sustainable solar energy to drive lignin conversion under mild conditions has been identified as a promising strategy and received growing research interest. This review aims to present a critical introduction to the photocatalytic conversion of lignin, including a summary of lignin conversion pathways and mechanisms, as well as the latest cutting-edge innovations on photocatalyst design and reactor construction. Moreover, the screening of solvents and regulation of other key factors that are involved in photocatalytic lignin conversion are also elucidated and future perspectives and challenges for photocatalytic conversion of lignin into valuable products are discussed.

Effects of the novel catalyst Ni-S2O8 2--K2O/TiO2 on efficient lignin depolymerization

To improve the utilization of lignin, much effort has been devoted to lignin depolymerization with the aim to decrease waste and enhance profitability. Here, a dual property (acid and base) catalyst, namely S₂O₈²⁻–K₂O/TiO₂, was carefully researched. Upon loading S₂O₈²⁻ and K₂O onto TiO₂, acid and base sites emerged, and S₂O₈²⁻ and K₂O mutually enhanced the acid and base strengths of the catalyst enormously; this indeed facilitated lignin depolymerization. Under appropriate conditions, the yields of liquid product, petroleum ether soluble (PE-soluble) product and total monomer products were 83.76%, 50.4% and 28.96%, respectively. The constituents of the PE-soluble fraction, which are mainly monomers and dimers, can be used as liquid fuels or additives. In addition, after the catalyst was modified by Ni, better results were obtained. Surprisingly, it was found that the Ni enhanced not only the hydrogenation capacity but also the acidity. The highest high heating value (HHV) of the liquid product (33.6 MJ kg⁻¹) was obtained, and the yield of PE-soluble product increased from 50.4 to 56.4%. The product can be utilized as a fuel additive or be converted to bio-fuel. This catalysis system has significant potential in the conversion of lignin to bio-fuel.

To improve the utilization of lignin, much effort has been devoted to lignin depolymerization with the aim to decrease waste and enhance profitability.

Effect of Reaction Conditions on Catalytic and Noncatalytic Lignin Solvolysis in Water Media Investigated for a 5 L Reactor

The high content of oxygen in the lignin polymer and the prevalence of phenolic functional groups make the conversion of lignin to fuels and value-added products with well-defined chemical properties challenging. The lignin-to-liquid process using a water/formic acid reaction medium has been shown to convert the lignin polymer to monomers with a molecular weight range of 300-600 Da. The bio-oil comprises a complex mixture of monomeric phenols, aromatics, and aliphatic hydrocarbons with a high H/C and low O/C ratio. This study investigates the effect of the stirring rate, level of loading, and catalyst at 305 and 350 °C in a 5 L pilot scale reactor. The oil yields are found to be highest for experiments conducted using the maximum stirring rate, maximum level of loading, and Ru/Al₂O₃ catalyst with yields of more than 69 wt % on lignin intake. Goethite as a catalyst does not show good conversion efficiency at either reaction temperatures. The carbon recovery is highest for products produced at 305 °C. Furthermore, results from solid phase extraction on a DSC-CN solid phase show that 65-92 wt % the bio-oils can be recovered as fractions separated based on polarity.

Rapid Nondestructive Fractionation of Biomass (≤15 min) by using Flow-Through Recyclable Formic Acid toward Whole Valorization of Carbohydrate and Lignin

Whole valorization of carbohydrate and lignin from biomass was achieved by rapid flow-through fractionation (RFF) within 15 min. Wheat straw was effectively deconstructed into its principle components without degradation by using easily recyclable aqueous formic acid (72 wt %) at 130 °C. The obtained cellulose-rich solid showed a nearly complete glucan recovery and 73.8 % glucose conversion after enzymatic hydrolysis. Xylan also reached full recovery with negligible furfural formation with a sum of 80 % of oligo/mono xylose in spent liquor and 20 % of xylan remaining in the solid. Up to 75.4 % lignin was dissolved in the spent liquor and further fractionated into water-insoluble (WIL) and water-soluble lignin (WSL) by dilution with water. WIL showed a non-condensed and well-preserved structure with 84.5 % β-O-4 remaining, which is believed to be beneficial for catalytic conversion into low-molecular-weight chemicals and fuels. The concentration of employed formic acid was below the formic acid/water azeotrope, and therefore the reaction medium could be restored through simple distillation. Together with the joint valorization of lignin and carbohydrates, the presented RFF is a promising process for sustainable biorefinery.

Catalytic Transfer Hydrogenolysis Reactions for Lignin Valorization to Fuels and Chemicals

Lignocellulosic biomass is an abundant renewable source of chemicals and fuels. Lignin, one of biomass main structural components being widely available as by-product in the pulp and paper industry and in the process of second generation bioethanol, can provide phenolic and aromatic compounds that can be utilized for the manufacture of a wide variety of polymers, fuels, and other high added value products. The effective depolymerisation of lignin into its primary building blocks remains a challenge with regard to conversion degree and monomers selectivity and stability. This review article focuses on the state of the art in the liquid phase reductive depolymerisation of lignin under relatively mild conditions via catalytic hydrogenolysis/hydrogenation reactions, discussing the effect of lignin type/origin, hydrogen donor solvents, and related transfer hydrogenation or reforming pathways, catalysts, and reaction conditions.

Origins of complex solvent effects on chemical reactivity and computational tools to investigate them: a review

Origins of solvent-induced enhancement in catalytic reactivity and product selectivity are discussed with computational methods to study them.

From lignin to valuable products-strategies, challenges, and prospects

The exploration of effective approaches for the valorization of lignin to valuable products attracts broad interests of a growing scientific community. By fully unlocking the potential of the world's most abundant resource of bio-aromatics, it could improve the profitability and carbon efficiency of the entire biorefinery process, thus accelerate the replacement of fossil resources with bioresources in our society. The successful realization of this goal depends on the development of technologies to overcome the following challenges, including: 1) efficient biomass pretreatment and lignin separation technologies that overcomes its diverse structure and complex chemistry challenges to obtain high purity lignin; 2) advanced chemical analysis for precise quantitative characterization of the lignin in chemical transformation processes; 3) novel approaches for conversion of biomass-derived lignin to valuable products. This review summarizes the latest cutting-edge innovations of lignin chemical valorization with the focus on the aforementioned three key aspects.

Solvent and catalyst effect in the formic acid aided lignin-to-liquids

The effect of the type of solvent, ethanol or water, and a Ru/C catalyst were studied in the formic acid aided lignin conversion. The best results were obtained in the presence of the Ru/C catalyst and using ethanol as solvent at 300 °C and 10 h (i.e. 75.8 wt% of oil and 23.9 wt% of solids). In comparison to the water system, the ethanol system yields a significantly larger amount of oil and, at 300 °C and 10 h, a smaller amount of solids. The main reasons for this positive effect of the ethanol solvent are i) the formation of ethanol-derived esters, ii) C-alkylations of lignin fragments and iii) the generation of more stable lignin derivatives. The Ru/C exhibits significantly higher lignin conversion activity compared to other Ni-based catalysts, especially at 300 °C, which is related to the enhanced activity of the Ru⁰ sites towards hydrogenolysis, hydrodeoxygenation and alkylation reactions.

BBr3-Assisted Preparation of Aromatic Alkyl Bromides from Lignin and Lignin Model Compounds

For the first time, BBr₃-assisted nucleophilic substitution was applied to a variety of β-O-4 and α-O-4 model compounds for the highly effective cleavage of different C-O bonds, including C-O_α-OH, C_β-O/C_α-O and C_Me-O bonds (<0.5 h and >99% conversion for most cases). Without any pretreatment, the substitution proceeds at room temperature in the absence of any catalyst, or additive, selectively affording phenols and important organic synthesis reagents, aromatic alkyl bromides, in high to excellent yields (up to 98%). Preliminary studies also highlight the prospect of this method for the effective cleavage of different types of C-O bonds in real lignin. A total 14 wt % yield of aromatic alkyl bromide, 4-(1,2-dibromo-3-hydroxypropyl)benzene-1,2-diol (10), has been obtained from an extracted lignin through this method.

Microwave-assisted efficient depolymerization of alkaline lignin in methanol/formic acid media

Microwave-assisted degradation of alkaline lignin in methanol/formic acid media was investigated, concerning the effect of formic acid (FA) amount, reaction temperature, and reaction time on lignin depolymerization. The highest bio-oil yield of 72.0 wt% including 6.7 wt% monomers was achieved at 160 °C and a FA-to-lignin mass ratio of 4 after a reaction time of 30 min. Among the monomers, the yield of 2,3-dihydrobenzofuran was the highest (3.00 wt%), followed by p-coumaric acid (1.59 wt%). Formic acid acted mainly through acid-catalyzed cleavage of the linkages in lignin. Oligomers in bio-oil were mainly composed of dimers (molecular weight: 253-378) and trimers (molecular weight: 379-510) according to the Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF MS) analysis. A possible mechanism about microwave-assisted depolymerization of lignin in methanol/formic acid media was proposed. This study will provide an efficient approach for lignin depolymerization.

State-of-the-art catalytic hydrogenolysis of lignin for the production of aromatic chemicals

Catalytic hydrogenolysis of lignin is overviewed, concerning the cleavage of typical inter-unit linkages and the production of aromatic chemicals.

Elucidating the reactivity of methoxyphenol positional isomers towards hydrogen-transfer reactions by ATR-IR spectroscopy of the liquid–solid interface of RANEY® Ni

In the presence of Raney® Ni and 2-propanol, guaiacol is orientated parallel to the catalyst surface, whereas 3- and 4-methoxyphenol forms a titled adsorption surface complex.

Catalytic Depolymerization of Lignin and Woody Biomass in Supercritical Ethanol: Influence of Reaction Temperature and Feedstock

The one-step ethanolysis approach to upgrade lignin to monomeric aromatics using a CuMgAl mixed oxide catalyst is studied in detail. The influence of reaction temperature (200-420 °C) on the product distribution is investigated. At low temperature (200-250 °C), recondensation is dominant, while char-forming reactions become significant at high reaction temperature (>380 °C). At preferred intermediate temperatures (300-340 °C), char-forming reactions are effectively suppressed by alkylation and Guerbet and esterification reactions. This shifts the reaction toward depolymerization, explaining high monomeric aromatics yield. Carbon-14 dating analysis of the lignin residue revealed that a substantial amount of the carbon in the lignin residue originates from reactions of lignin with ethanol. Recycling tests show that the activity of the regenerated catalyst was strongly decreased due to a loss of basic sites due to hydrolysis of the MgO function and a loss of surface area due to spinel oxide formation of the Cu and Al components. The utility of this one-step approach for upgrading woody biomass was also demonstrated. An important observation is that conversion of the native lignin contained in the lignocellulosic matrix is much easier than the conversion of technical lignin.

Analysis of the effect of temperature and reaction time on yields, compositions and oil quality in catalytic and non-catalytic lignin solvolysis in a formic acid/water media using experimental design

The catalytic solvolysis of Norway spruce (Picea abies L.) lignin in a formic acid/water media was explored at different temperatures and reaction times (283-397°C and 21-700min, respectively). Non-catalyzed experiments were compared with the effect of three different type of bifunctional catalysts (Pd/Al₂O₃, Rh/Al₂O₃ and Ru/Al₂O₃) and a solid Lewis acid (γ-Al₂O₃). We demonstrated that surface response methodology (RSM) and principal component analysis (PCA) were an adequate tool to: (i) evaluate the effect of the catalysts, temperature and reaction time in the oil yield, oil quality (H/C and O/C ratios, and M_w) and composition of the oil, (ii) establish the differences and/or similarities between the three bifunctional catalyst and (iii) to determine the role of the noble metal and the alumina support in the reaction system. In addition, the most active catalysts, Ru/Al₂O₃, and the optimum reaction conditions were determined (i.e. 340°C and 6h).

Composition of Lignin-to-Liquid Solvolysis Oils from Lignin Extracted in a Semi-Continuous Organosolv Process

The interest and on-going research on utilisation of lignin as feedstock for production of renewable and sustainable aromatics is expanding and shows great potential. This study investigates the applicability of semi-continuously organosolv extracted lignin in Lignin-to-Liquid (LtL) solvolysis, using formic acid as hydrogen donor and water as solvent under high temperature-high pressure (HTHP) conditions. The high purity of the organosolv lignin provides high conversion yields at up to 94% based on lignin mass input. The formic acid input is a dominating parameter in lignin conversion. Carbon balance calculations of LtL-solvolysis experiments also indicate that formic acid can give a net carbon contribution to the bio-oils, in addition to its property as hydrogenation agent. Compound specific quantification of the ten most abundant components in the LtL-oils describe up to 10% of the bio-oil composition, and reaction temperature is shown to be the dominating parameter for the structures present. The structural and quantitative results from this study identify components of considerable value in the LtL-oil, and support the position of this oil as a potentially important source of building blocks for the chemical and pharmaceutical industry.