LignoBoost Process Research Articles

Purification and Fractionation of Lignin via ALPHA: Liquid-Liquid Equilibrium for the Lignin-Acetic Acid-Water System.

In order to effectively practice the Aqueous Lignin Purification with Hot Agents (ALPHA) process for lignin purification and fractionation, the temperatures and feed compositions where regions of liquid-liquid equilibrium (LLE) exist must be identified. To this end, pseudo-ternary phase diagrams for the lignin-acetic acid-water system were mapped out at 45-95 °C and various solvent: feed lignin mass ratios (S:F). For a given temperature, the accompanying SL (solid-liquid), SLL (solid-liquid-liquid), and one-phase regions were also located. For the first time, ALPHA using acetic acid (AcOH)-water solutions was applied to a lignin recovered via the commercial LignoBoost process. In addition to determining tie-line compositions for the two regions of LLE that were discovered, the distribution of lignin and key impurities (the latter can negatively impact lignin performance for materials applications) between the two liquid phases wasalso measured. As a representative example, lignin isolated in thelignin-rich phase was reduced 7x in metals and 4x in polysaccharides by using ALPHA with a feed solvent composition of 50-55% AcOH and an S:F of 6:1, with said lignin being obtained at a yield of 50-70% of the feed lignin and having a molecular weight triple that of the feed.

Cationization of Eucalyptus Kraft LignoBoost Lignin: Preparation, Properties, and Potential Applications.

Current changes toward a more biobased economy have recently created tremendous renewed interest in using lignin as a valuable source for chemicals and materials. Here, we present a facile cationization approach aiming to impart kraft lignin water-solubility, with similar good features as lignosulfonates. Eucalyptus globulus kraft lignin obtained from a paper mill black liquor by applying the LignoBoost process was used as the substrate. Its reaction with 3-chloro-2-hydroxypropyl-trimethylammonium chloride (CHPTAC) in an aqueous alkaline medium was studied to assess the impact of different reaction conditions (temperature, time, educt concentration, molar CHPTAC-to-lignin ratio) on the degree of cationization. It has been shown that at pH 13, 10 wt % lignin content, 70 °C, and 3 h reaction time, a CHPTAC-to-lignin minimum molar ratio of 1.3 is required to obtain fully water-soluble products. Elemental analysis (4.2% N), size-exclusion chromatography (Mw 2180 Da), and quantitative 13C NMR spectroscopy of the product obtained at this limit reactant concentration suggest introduction of 1.2 quaternary ammonium groups per C9 unit and substitution of 75% of the initially available phenolic OH groups. The possible contribution of benzylic hydroxyls to the introduction of quaternary ammonium moieties through a quinone methide mechanism has been proposed. Since both molecular characteristics and degree of substitution, and hence solubility or count of surface charge, of colloidal particles can be adjusted within a wide range, cationic kraft lignins are promising materials for a wide range of applications, as exemplarily demonstrated for flocculation of anionic dyes.

Upscaling of lignin precursor melt spinning by bicomponent spinning and its use for carbon fibre production.

Upscaling lignin-based precursor fibre production is an essential step in developing bio-based carbon fibre from renewable feedstock. The main challenge in upscaling of lignin fibre production by melt spinning is its melt behaviour and rheological properties, which differ from common synthetic polymers used in melt spinning. Here, a new approach in melt spinning of lignin, using a spin carrier system for producing bicomponent fibres, has been introduced. An ethanol extracted lignin fraction from LignoBoost process of commercial softwood kraft black liquor was used as feedstock. After additional heat treatment, melt spinning was performed in a pilot-scale spinning unit. For the first time, biodegradable polyvinyl alcohol (PVA) was used as a spin carrier to enable the spinning of lignin by improving the required melt strength. PVA-sheath/lignin-core bicomponent fibres were manufactured. Afterwards, PVA was dissolved by washing with water. Pure lignin fibres were stabilized and carbonized, and tensile properties were measured. The measured properties, tensile modulus of 81.1 ± 3.1 GPa and tensile strength of 1039 ± 197 MPa, are higher than the majority of lignin-based carbon fibres reported in the literature. This new approach can significantly improve the melt spinning of lignin and solve problems related to poor spinnability of lignin and results in the production of high-quality lignin-based carbon fibres. This article is part of the theme issue 'Bio-derived and bioinspired sustainable advanced materials for emerging technologies (part 2)'.

Lignin-Containing Coatings for Packaging Materials-Pilot Trials.

One severe weakness of most biopolymers, in terms of their use as packaging materials, is their relatively high solubility in water. The addition of kraft lignin to starch coating formulations has been shown to reduce the water solubility of starch in dry coatings. However, lignin may also migrate into aqueous solutions. For this paper, kraft lignin isolated using the LignoBoost process was used in order to examine the effect of pH level on the solubility of lignin with and without ammonium zirconium carbonate (AZC). Machine-glazed (MG) paper was coated in a pilot coating machine, with the moving substrate at high speed, and laboratory-coated samples were used as a reference when measuring defects (number of pinholes). Kraft lignin became soluble in water at lower pH levels when starch was added to the solution, due to the interactions between starch and lignin. This made it possible to lower the pH of the coating solutions, resulting in increased water stability of the dry samples; that is, the migration of lignin to the model liquids decreased when the pH of the coating solutions was reduced. No significant difference was observed in the water vapor transmission rate (WVTR) between high and low pH for the pilot-coated samples. The addition of AZC to the formulation reduced the migration of lignin from the coatings to the model liquids and led to an increase in the water contact angle, but also increased the number of pinholes in the pilot-coated samples.

Systematic Review on Isolation Processes for Technical Lignin

Technologies for the isolation of lignin from pulping process streams are reviewed in this article. Based on published data, the WestVaco process, the LignoBoost process, the LigoForce SystemTM and the SLRP process are reviewed and discussed for the isolation of lignin from Kraft black liquor. The three new processes that have now joined the WestVaco process are compared from the perspective of product quality. Further, isolation processes of lignosulfonates from spent sulfite liquor are reviewed. The limitation for this review is that data are only available from lab scale and pilot scale experiments and not from industrial processes. Key output of this paper is a technology summary of the state of the art processes for technical lignins, showing the pros and cons of each process.

Allocation in life cycle assessment of lignin

PurposeLignin extraction in pulp mills and biorefineries are emerging technologies. Lignin is always the product of a multi-output process. Assessing such processes using life cycle assessment (LCA) requires the environmental impacts to be divided between the co-products of the system, referred to as allocation. This article explores different allocation approaches for lignin and illustrates the influence of the choice of allocation approach on the climate impact in a case study.MethodTen different applicable allocation methods were found in literature and two more were developed. Lignin production in a Kraft pulp mill using the LignoBoost process for lignin extraction was selected as a study object for the case study, and due to limited data availability only climate impact was considered. A cradle-to-gate LCA was done for the study object, and all of the twelve allocation approaches were applied; for eight of the methods, factors that strongly influence the results were identified and varied. Finally, the results were put in the context of cradle-to-grave LCAs from literature for different possible uses of lignin to give an indication of how important the choice of allocation approach can be when assessing lignin as a substitute for other raw materials.Results and discussionResults show that all allocation approaches tested were applicable to the special case of lignin, but each one of them comes with inherent challenges. Factors that often have a large impact on the results are (1) market and price of different outputs; (2) what is seen as the main product or the driver of the system or system changes; (3) what the surrounding system looks like and hence what other products will be displaced by outputs. These factors can be particularly challenging in prospective studies as such studies are future-oriented and consider systems that do not yet exist. Finally, the results show that the choice of allocation could have a significant influence on the climate impact on the cradle-to-grave climate impact of the final product.ConclusionsWe recommend for LCAs of lignin-based technologies that allocation methods are very carefully selected based on the goal and scope of the study and that when relevant, several methods are applied and factors are varied within them in a sensitivity analysis. In particular, the driver(s) of the system’s existence or of changes to it, sometimes reflected in market prices of outputs, should be carefully considered.

Development of a Black Liquor Electrolyzer for Lignin Extraction

Nowadays, the pulp and paper industry is looking for different biorefinery and bioproduct market areas, in order to turn the production more sustainable and improve the economic feedback from its biomass and secondary products [1]. One of the significant challenges for pulp mills is the development of technologies for separation and conversion of lignin from black liquor [2]. The black liquor is a by-product produced during the Kraft pulping, which consists in a complex mixture of inorganic and organic constituents [1,3]. Considering the organics, lignin is one of the most interesting biopolymers from wood [4], making up 30-45 wt.% of the total solid composition [5]. This compound has wide applications, namely as a substitute of phenol in phenolic resins, as adjunct crosslinker for epichlorohydrin reaction (used in epoxy resins production), as binder in construction systems and as biodegradable plastic additive [6]. Millions of tons of black liquor, and consequently of lignin, are produced every year in pulp mills. A ton of bleached Kraft pulp generates 400-500 kg of lignin (dissolved in black liquor) and only 2% of this amount is commercialized [5]. The pulping process begins with the cooking of the wood chips in a digester, containing NaOH and Na2S, in order to obtain a fiber suspension [1,7]. The raw pulp is then washed with water, generating pulp and black liquor. The latter is concentrated and then burned in a recovery furnace for energy generation and chemicals recovery. Therefore, the production capacity of pulp mills is limited by the recovery furnace capacity [6,8]. The present work deals with the use of electrolysis as an alternative for reducing the volume of black liquor sent to the recovery furnace. It should establish the fraction of lignin that an electrolyzer can remove from the liquor stream before it returns to the process. The electrolysis of black liquor leads to lignin recovery by anodic electrodeposition and to hydrogen generation at the cathode [7]. Herein, we first determine the physicochemical properties of Kraft black liquor samples from Eucalyptus globulus, such as conductivity, dry solids content, organic/inorganic ratio and lignin content. Then, electrolysis experiments using a laboratory electrolyzer are performed, in order to extract the lignin from the black liquor. We assess the effect of several cell operation parameters, such as the electrolysis time, the effect of the electrode surface treatment, the volume of black liquor, and working temperature. Different materials, such as nickel, stainless steel, iron and cadmium are tested as anodes/cathodes, in order to select the best electrodes. For each distinct electrodes’ combination, the individual cathode and anode potentials are measured versus a saturated calomel electrode, to ensure that the working potentials are enough to attain the lignin oxidation and the hydrogen evolution reaction processes with high kinetics. This procedure enables optimizing the cell operation and helps developing the most cost-effective and energy-efficient electrolyzer. Polarization curves are drawn for each experiment. The obtained lignin is analyzed by optical microscopy, SEM-EDS, TGA and FTIR, and compared with lyophilized lignin obtained from black liquor acidification and with lignin from LignoBoost process [9]. The results show that the proposed black liquor electrolyzer allows extracting the lignin contained in Kraft black liquor, enabling the pulping processes to be more sustainable. [1] Oliveira, R.C.P., Mateus, M., Santos, D.M.F., Black liquor electrolysis for hydrogen and lignin extraction, ECS Trans. 72, 1-11 (2016). [2] Ghatak, H.R., Kumar, S., Kundu, P.P., Electrode processes in black liquor electrolysis and their significance for hydrogen production, Int. J. Hydrogen Energy 33, 1-8 (2008). [3] Rowell, R., Handbook of wood chemistry and wood composites, 2nd ed. (2012), Boca Raton: CRC Press. [4] Cloutier, J.-N., Savadogo, O., Paris, J., Perrier, M., Labrecque, R., Kandev, N., Champagne, P., Effect of the basic electrochemical cell operating parameters on the performance of the electrolysis of kraft pulping black liquor, ECS Trans. 80, 1-21 (2017). [5] Jin, W., Tolba, R., Wen, J., Li, K., Chen, A., Efficient extraction of lignin from black liquor via a novel membrane-assisted electrochemical approach, Electrochim. Acta 107, 1-8 (2013). [6] Stewart, D., Lignin as a base material for materials applications: Chemistry, application and economics, Ind. Crops Prod. 27, 202-207 (2008). [7] Oliveira, R.C.P., Mateus, M., Santos, D.M.F., Chronoamperometric and chronopotentiometric investigation of Kraft black liquor, Int. J. Hydrogen Energy (in press) (2018), doi:10.1016/j.ijhydene.2018.01.046. [8] Pinto, P., Conversion of lignin to high added-value chemicals and materials: an opportunity to pulp and paper industry and biorefineries, XXIII Tec. - Int. For. Pulp Pap. Conf. 1-8 (2016). [9] Tomani, P., The lignoboost process, Cellul. Chem. Technol. 44, 53-58 (2010).

Carbon fibres from precursors produced by dry-jet wet-spinning of kraft lignin blended with kraft pulps

Abstract A part of kraft lignin (KL) can be used as a value-added product without detracting the chemical recovery and the energy balance of the kraft mill. The focus of this study is the production of light-weight carbon fibres (CFs) from KL obtained by the LignoBoost process. For this purpose, crude KL and various cellulose products from kraft pulping of hardwood (HW) and softwood (SW) were dissolved in 1-ethyl-3-methylimidazolium acetate ([EMIm][OAc]) and submitted to dry-jet wet-spun to obtain precursor fibres containing 70% KL and 30% cellulose, which were thermally stabilised and further converted by thermal treatments into CF. The initial and final products were characterised with respect to, e.g. mole mass distribution, thermal properties, tensile strength and tensile modulus determination. The optimised precursor fibres are smooth and flexible with similar mechanical properties as commercial textile fibres. The best CFs made had a tensile strength of 780 MPa and a tensile modulus of 68 GPa and are thus stronger and stiffer than those produced by melt-spinning of SW-based lignins alone. The new CFs based on dry-jet wet-spun precursors still have a high potential for further improvements.

Melt-blown compostable polyester films with lignin

Compostable films for such uses as packaging and agricultural soil covering materials were first produced on commercial scale from blends of biodegradable polyesters and a modified kraft lignin. The lignin consisted of an industrial product isolated according to the LignoBoost process. The lignin modification involved homogeneous phase reaction with propylene oxide, and the films were melt-blown from a pelletized compound consisting of up to a 30% blend of lignin derivative with commercial biodegradable polyester. The 12–93 μm thick films combined the characteristics of lignin as modulus-building and environmentally degradable polymer with those of the strength-building thermoplastic polyester. Although the modified lignin paralleled the behavior of native lignin in wood by resisting rapid and full conversion to carbon dioxide in a simulated composting environment, two thirds of the film mass biodegraded within 12 weeks of composting, with the remainder turning into (humus-like) water-soluble solids and particles <2 mm in size. The lignin derivatives suffered from the release of trace amounts of malodorous volatiles containing reduced sulfur when subjected to melt-blowing. The objectionable odor was virtually unnoticeable in injection-molded solid parts.

Physicochemical characterization of residue from the enzymatic hydrolysis of sugarcane bagasse in a cellulosic ethanol process at pilot scale

One of the major obstacles to use lignin as feedstock for value-added products at industrial scale is that its physicochemical characteristics can widely vary. Thus, it is necessary to know such characteristics before applying in the synthesis of products. In this study, we produce a lignocellulosic biomass in pilot scale composed of lignin (47%w/w) and cellulose fibers (40%w/w). This biomass was obtained from the enzymatic hydrolysis of sugarcane bagasse that was pretreated by a hydrothermal process (190°C/10min). After obtaining this residue, which is listed here as “Enzymatic Hydrolysis Residue Lignin” (EHRL), its physicochemical and thermal characterization was performed. A highly concentrated lignin from the LignoBoost process in Kraft pulp mill, lignin LignoBoost (LBL), was also evaluated in order to compare it with the EHRL. The C9-formulae of the lignin extracted from the EHRL is C9.0H11.2O4.3S0.08N0.17(OCH3)0.9(OHphenolic)0.7(OHaliphatic)0.6 and the C9-formulae of the LBL is C9.0H7.9O1.4S0.16N0.01(OCH3)1.1(OHphenolic)0.7(OHaliphatic)0.5. By the 2D Heteronuclear Single-Quantum Correlation Spectroscopy (HSQC) technique, syringyl/guaiacyl ratios for the EHRL and the LBL are 1.8 and 4.8, respectively. Thus, the EHRL appears to be promising for phenolic composite, for instance, since it has lower methoxyl content. The EHRL showed larger range of fiber particle sizes (<4.05mm–0.4μm) than the LBL (0.4–1090μm).

Kraft Lignin - an Alternative Sustainable Binder Material for Green Li-Ion Batteries

The binder material plays an important role in the electrodes for Li-ion batteries, keeping good electrochemical stability and adhesion with the current collectors. The conventional binder for the commercial Li-ion batteries is poly vinylidene fluoride (PVDF). However, it requires dissolving in an organic solvent, typically N-methyl-2-pyrrolidione (NMP), which is toxic and expensive. Kraft lignin is a byproduct which is extracted from pulp and paper industries by the LignoBoost process [1]. Its utilization has gained considerable attention due to its reasonable cost, relatively high purity and being renewable. In this work, kraft lignin was used for the first time as a binder material in Li-ion batteries [2]. It is more environmental friendly and potentially less expensive compared to the PVDF binder. Electrodes, LiFePO4 positive and graphite negative electrodes bound by kraft lignin, were characterized using scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and galvanostatic charge-discharge cycles. Results show that the electrodes have good reversible capacities about 150 mAh g-1 for positive electrode and 300 mAh g-1 for negative electrode cycled at C/10, and fairly good rate capabilities. The negatives have a very high cycling stability with about 98% retention after 50 cycles cycled at C/4. It illustrates that lignin is a promising alternative sustainable binder material for green Li-ion batteries. Reference 1. Tomani, P., The lignoboost process. Cellulose Chemistry & Technology, 2010. 44(1): p. 53. 2. Lu, H., et al., Lignin as a Binder Material for Eco-Friendly Li-Ion Batteries. Materials, 2016. 9(3): p. 127. Figure 1

Lignin Prepared by Ultrafiltration of Black Liquor: Investigation of Solubility, Viscosity, and Ash Content

Technical lignin, which can be potentially obtained in large amounts as a by-product from kraft pulping, represents a potential resource for manufacturing fuels and chemicals. Upgrading of lignin, by lowering its molecular weight, is a valuable alternative to precipitation from black liquor, which occurs in the Lignoboost process. The solubility properties of Lignoboost lignin and filtered lignin in a number of technically feasible solvents were compared, and it was found that both lignins were dissolved in similar solvents. With the exception of furfural, the best lignin solvents generally were organic solvents miscible with water, such as methanol. It was possible to dissolve more filtered lignin in higher concentrations than Lignoboost lignin; additionally, the viscosities of the filtered lignin solutions were also considerably lower than those of Lignoboost lignin, especially at higher concentrations. Methods for non-organic component removal from filtrated lignin were tested, and it was concluded that several cold acidic treatments after dewatering can lower the ash content to values below 0.5% by weight.

Evaporation of lignin-lean black liquor

Many of the pulp mill biorefinery concepts recently presented include removal of lignin from black liquor. In this work, the aim was to study how the change in liquor chemistry affected the evaporation of kraft black liquor when lignin was removed using the LignoBoost process. Lignin was removed from a softwood kraft black liquor and four different black liquors were studied: one reference black liquor (with no lignin extracted); two ligninlean black liquors with a lignin removal rate of 5.5% and 21%, respectively; and one liquor with maximum lignin removal of 60%. Evaporation tests were carried out at the research evaporator in Chalmers University of Technology. Studied parameters were liquor viscosity, boiling point rise, heat transfer coefficient, scaling propensity, changes in liquor chemical composition, and tube incrustation. It was found that the solubility limit for incrustation changed towards lower dry solids for the lignin-lean black liquors due to an increased salt content. The scaling obtained on the tubes was easily cleaned with thin liquor at 105°C. It was also shown that the liquor viscosity decreased exponentially with increased lignin outtake and hence, the heat transfer coefficient increased with increased lignin outtake. Long term tests, operated about 6 percentage dry solids units above the solubility limit for incrustation for all liquors, showed that the heat transfer coefficient increased from 650 W/m2K for the reference liquor to 1500 W/m2K for the liquor with highest lignin separation degree, 60%.

Production of a pure lignin product, Part 3: Distribution and removal of inorganics from softwood lignin

Future high value lignin-based products, such as carbon fibers, require a lignin raw material essentially free from inorganic impurities. Lignin of low inorganic content can be separated from kraft black liquor by the LignoBoost process. This laboratory scale study focuses on the effect of process parameters, such as pH and retention time in re-suspension, on the content of inorganic impurities in the LignoBoost lignin. Black liquor from pulping of softwood was used in this study. Specific attention was paid to the elements Na, K, Al, Ba, Ca, Fe, Mg, Mn and Si. It was found that the softwood lignin contained significantly less Ca, resulting in lower ash content, than eucalyptus lignin separated in earlier studies made in this series. Inorganic particles, containing for example Ca-O and Na-Al-Si, were observed in the washed lignin. Prolonged retention time in the re-suspension stage reduced the content of Ca, Mn, Mg, Fe and Si in the washed lignin. A reduction of the content by 30-50% after 24 h was possible. The rate at which these elements are removed from the agglomerates was found to be dependent on the mixing conditions, which indicates that the mass transfer in the liquid film around the particles is of importance for the total mass transfer resistance.

Local and average filtration properties of kraft softwood lignin

The extraction of lignin from black liquor is of interest in order to increase the overall material yield when producing paper pulp by the kraft process. The extracted lignin can be used either as a solid biofuel or a potential alternative raw material to fossil oil for the production of various green chemicals and high valuable products such as carbon fibres. The LignoBoost process is a new approach in which the kraft lignin extracted reaches a high level of purity. In this study, the local and average dead-end filtration properties during dewatering of a softwood lignin extracted from black liquor using the LignoBoost process were investigated; the material was also characterized. It was found that the investigated lignin was an easy to filter material that formed weakly compressible filter cakes in the solid compressive pressure range of 0.03 to 1.5 MPa. The concentration of the lignin slurry did not influence the filtration properties; the resulting cakes final heights were in the industrial size range. Moreover, the two different filter media used yielded similar results. Semi-empirical relationships were fitted successfully to the experimental local data and a good estimation of the average filtration properties was also obtained using the relationships fitted parameters. This indicates a good agreement between the local and average experimental data.

Investigation and Characterization of Lignin Precipitation in the LignoBoost Process

Lignin of high purity can be separated from black liquor using the LignoBoost process, of which the overall efficiency is largely dependent on the precipitation yield of lignin, which depends on the properties of black liquor and process conditions. In this paper, the influences of process conditions on the precipitation yield of lignin from mixed hardwood/softwood black liquor were investigated. The Klason and standard UV method were used to determine lignin concentration. The chemical and structural properties of lignin were also analyzed. The results showed that the precipitation yield of lignin increased along with a decrease in pH and temperature, or with an increase in the ion strength of black liquor, and the yield was lower when mixed softwood/hardwood black liquor was used. It also showed that at a higher precipitation yield the precipitated lignin had a lower average molecular weight but had higher methoxyl and phenolic hydroxyl content.

Evaluation of industrial lignins for biocomposites production

Following important market changes to the pulp and paper industry, the interest in valorization of industrial lignins has significantly increased. Recent advancements with the LignoBoost process in Europe have made the availability of Kraft lignins a realistic prospective. The objective of the present study was to identify industrial lignins that have the potential to replace a portion of polyolefins, such as polyethylenes within composites. In order to identify the best lignin candidates for applications in biomaterials, five industrial lignins were compared. Softwood and hardwood Kraft lignins were precipitated by CO2 from black liquor obtained from two Quebec pulp mills. The isolated lignins were characterized along with the commercial Kraft lignin Indulin, Soda (from wheat straw) and pyrolytic lignin obtained from pyrolysis of hardwood biomass. Elementary composition and purity of the studied lignins were determined. Phenolic contents were studied by UV-spectrophotometry, while additional structural characteristics and molecular mass distribution were analyzed by FT-IR, pyrolysis-GC–MS and by GPC. Thermal properties were determined by TGA and TMA. The results obtained confirmed that the major differences between the studied lignins were related to the plant origin and to the industrial process from which they were issued. The properties of Kraft lignins compared to the other lignins samples studied seem to be the best suited for use in biocomposites based on polyolefins. Such application of Kraft lignins could promote new pathways to the value added products based on by-products of pulp and paper industry, while simultaneously contributing to the decrease of greenhouse gases by replacing a part of petroleum origin materials by natural products.

Pyrolysis oils from CO2 precipitated Kraft lignin

A common goal in present and future forestry, biofuels and biomaterials practices, is the need to valorize lignocellulose processes to maximize value and optimize autonomic economy. Consequently, a key focus of modern biorefining is the on-site utilization of all residual materials generating products of the highest possible value. The LignoBoost process, recently demonstrated on the pilot-scale at Kraft pulp mills, injects CO2 into pulping liquors which results in a lower solution pH and thereby precipitates lignin. The present paper compares and evaluates the pyrolysis of pulping liquor lignins precipitated by sulfuric acid (pH 3) and the aforementioned CO2 method (pH 10.5 and 9.5). The CO2 based process yielded lignin that showed superior pyrolysis properties including low gas formation and increased bio-oil yields, close to 40%, consisting primarily of low (∼150 g mol−1) molecular weight compounds. Subsequent NMR analysis showed that the oils exhibit favorable changes in functionalities, e.g. loss of aromatic and gain in aliphatic carbon percentages as well as decrease in carboxyl and methoxyl (oxygen containing) groups. Moreover, NMR results further confirmed previously hypothesized lignin pyrolysis reactions, while at the same time showed the potential of CO2 precipitated lignin for pyrolysis and subsequent liquid biofuel production.

Correlations for the viscosity of lignin lean black liquor

In this study, experimental results from earlier work on viscosity measurements of black liquors with different lignin contents were used to develop an empirical model describing viscosity as a function of temperature, dry content and concentration of lignin and hemicellulose. The liquors studied were taken from six different lignin extraction runs, according to the LignoBoost process, at different mills. The viscosity data was available at a wide range of temperature (40-130 degrees C) and dry content (30-70 w/w-%): this data was used to calculate the parameters in the model. Furthermore, one of the general correlations was developed by taking the concentrations of lignin and hemicellulose into account. The results of this study showed that a much better fitting of the model could be obtained by taking the influence of the organic content in the black liquor into account.