Method for producing a modified lignin derivative, modified lignin derivative and biomass pellets thereof

Abstract

According to a method for producing a modified lignin derivative a lignin dispersion of lignin or a derivative thereof is acidified, mixed with a modifier and filtered off after ageing and optionally purified. The invention also relates to a modified lignin derivative of this type, to the use thereof and to biomass pellets containing same.

Description

[0001] Process for producing a modified lignin derivative, modified lignin derivative and biomass pellets therefrom

[0002] The present invention relates to a process for producing a modified lignin derivative in which lignin or a derivative thereof is used as a starting material, a modified lignin derivative produced according to a process for producing a modified lignin derivative and the use of a modified lignin derivative thus produced and biomass pellets containing the same.

[0003] Wood or biomass as such, especially woody biomass, has been used as a heating material for centuries, for example, because biomass is characterized by its relatively rapid growth and is therefore available in sufficient quantities. Wood or biomass as such as a fuel has undergone numerous modification processes in recent decades to enable the economical use of not only fresh wood, but also wood waste products and biomass such as reeds or grasses, and in particular to increase their calorific value as much as possible. Recent research aims to maximize the energetic value of wood, woody components, or biomass as such as an energy source, in order to burn them as completely as possible after increasing their calorific value.It was also determined that lignin, which is present in considerable quantities as a natural component of wood, represents a significant energy source that can be used not only in the paper industry, for example, but also as an energy source in fuels. In the paper industry, lignin, which is at least partially removed from the pulping process during the wood pulping process, is subjected to drying, among other processes, and then used as a fuel, for example, in a digester.

[0004] From CA 3 030 215 A1 it is known that water-resistant pellets which are simultaneously resistant to both moisture and compressive stress and have a high calorific value can be produced by mixing biomass, in particular torrefied wood, with a binder consisting of lignin and, for example, a plasticizer selected from fatty acids, rosin, vegetable oils, animal oils or glycerin. The pellets produced in this way are characterized by high strength and moisture resistance as well as a high calorific value. The binder used in the pellets is a two-component binder containing lignin and the plasticizer, since lignin per se cannot be used without a plasticizer. The use of lignin in fuel materials is known, for example, from Stevens, J., & Gardner, DJ.(2010); Enhancing the fuel value of wood pellets with the addition of lignin; Wood and Fiber Science, 42(4), 439-443, in which two different types of lignins were tested to increase the calorific value of wood pellets compared to pure wood. In this document, a high-purity lignin with an ash content of less than 1% and a lignin from black liquor were used, and it was shown that the calorific value of the pellets produced from them increased compared to untreated pellets.

[0005] From JP 2019073679 A, ​​a modified lignin product, preferably kraft lignin, as well as products containing it or mixtures therewith, have become known.

[0006] EP 3 910 029 A1 discloses a process for substituting at least one hydroxyl group of lignin, in particular an esterification of at least one hydroxyl group of lignin.

[0007] WO 2019 / 046704 A describes a process for separating or recovering lignin from biomass or biomass by-products using water or organic solvents, in which the composition of the lignin is altered per se. A problem typically associated with the combustion of pellets is the high fines content in the pellets, which, based on SS187120 (Solid bio fuel - fuel specifications and classes - part 2: graded wood pellet, 2014), must be < 0.8%, which can only be achieved with wood pellets by adding binders such as starch, resins, fatty acids, or DGI. An attempt to replace these binders with unmodified lignin has not led to satisfactory results, as, on the one hand, the quality of the pellets was reduced, and, on the other hand, the fines content could not be reduced.The use of lignosulfonates originating from paper production has also proven unsuitable, as they are not permitted to be used in fuels, especially wood pellets, due to their high sulfur content, which is converted to sulfur dioxide during combustion and thus contributes to the formation of so-called acid rain.

[0008] The present invention aims to provide a simple process for modifying lignin, with which it is possible to modify lignin in such a way that it can subsequently be used directly in various technical processes in order to contribute to improving the energy efficiency of the products containing it, while at the same time avoiding the disadvantages of the prior art. To achieve this object, the process according to the invention is essentially characterized by the steps: a) dispersing or suspending the lignin or the lignin derivative in water in a ratio between 1:3 and 1:10, preferably 1:5 and 1:9 and particularly preferably 1:7 and 1:8, b) adding at least one acidifying agent to the dispersion or suspension and adjusting a pH value of the dispersion or suspension.Suspension to values ​​of less than 4.5, preferably less than 2.5, particularly preferably 2; c) optionally heating the dispersion or suspension to temperatures between 25 °C and 90 °C and adding water as a diluent; d) adding at least one modifier selected from the group of sizing agents, fixing agents, dispersants, flocculating aids or drainage aids which can be used in paper production in an amount of between 0.01 and 3 wt.% of the absolutely dry amount of the lignin or the derivative thereof, preferably 0.5 to 2.5 wt.% of the absolutely dry amount of the lignin or the derivative thereof, wherein the modifier is optionally dissolved in a lower alcohol, such as ethanol; e) stirring the dispersion orSuspension and maintaining the temperature for a period of at least 2 minutes, preferably more than 20 minutes, more preferably at least 30 minutes, and most preferably more than 50 minutes; f) allowing to settle and separating the modified lignin derivative, and optionally g) washing with water and drying the modified lignin derivative.

[0009] In the present application, the term lignin is understood to mean the chemically and physically unaltered biopolymer that occurs naturally, for example, in wood. A lignin derivative, as used as starting material in the process of the present invention, is understood to mean a biological material, such as that which arises, for example, during pulp or paper production. Such lignin derivatives are modified by the cooking process compared to a native, naturally occurring lignin and are therefore no longer to be subsumed under the term lignin as such, but are derivatives of naturally occurring lignin, such as lignosulfonates, which derivatives can, however, also be used for the process and use according to the present invention.

[0010] By carrying out a combination of two steps during the process, namely an acidification step and a step of adding a modifier, it is surprisingly possible to change the surface properties of the lignin or derivative thereof used, or to attach the modifier to the surface of the lignin or derivative thereof used, in particular by means of Van der Waals forces, so that a lignin modified in this way, when used in pellets, for example, leads to a surprising increase in the calorific value of pellets, in comparison to pellets conventionally produced from lignin and wood components.In order to carry out this process for producing modified lignin quickly and reliably, in particular to completely modify the surface of the lignin, the process is optionally carried out at temperatures between 25 °C and 90 °C and with the addition of water as a diluent. Furthermore, by adding at least one acidifying agent to the dispersion or suspension and adjusting the pH of the dispersion or suspension to values ​​of less than 4.5, preferably less than 2.5, particularly preferably 2, to the dispersion or suspension of lignin or a lignin derivative, a so-called acid-washed lignin is produced, which after addition of the modifier, which is selected from the group of sizing agents, fixing agents, dispersants, flocculation aids or drainage aids that can be used in paper production in an amount of between 0.01 and 3 wt.-% of the absolutely dry amount of lignin or derivative thereof, preferably 0.5 to 2.5 wt.% of the absolutely dry amount of lignin or derivative thereof, wherein the modifying agent is optionally additionally dissolved in a lower alcohol, such as ethanol, for a period of at least 2 minutes, preferably more than 20 minutes, particularly preferably at least 30 minutes, while stirring and maintaining the temperature, causing the suspension to age, or by stirring the suspension for a predetermined period and maintaining it at the predetermined temperature, the surface modification of the formed lignin derivative becomes even more complete. After allowing the modified lignin derivative formed to settle and separating it, and optionally washing it with water and drying it, a modified lignin derivative is obtained which has an increased calorific value compared to unmodified lignin or the lignin derivative used.a lower specific energy of 1 kWh / t. With such a process, it is surprisingly possible to achieve a significantly increased calorific value of the lignin derivative formed compared to the starting product used, using extremely small amounts of a modifier, in particular significantly smaller amounts of a modifier than have been used to date, namely between 0.01 and 3 wt.% of the absolutely dry amount of the lignin or derivative used.

[0011] The fact that a significant improvement in the properties, in particular the calorific value and the specific work of the modified lignin derivative, is achieved by using minimal amounts of a modifier is likely to result from the fact that the intimate contact of the modifier with the lignin or lignin derivative to be modified in solution, suspension or dispersion results in an almost complete deposition of the modifier on the surface of the starting product to be modified and thus the use of excess amounts of the modifier can be avoided and, despite this, a maximization of the modification and, at the same time, a significantly improved energy efficiency can be achieved.

[0012] By conducting the process in such a way, as corresponds to a further development of the invention, that the lignin or lignin derivative used as starting material is selected from: alkaline lignin obtained by precipitation from black liquor, lignin enriched with enzymes or a mixture thereof, starting from an industrial waste product, namely the alkaline lignin from black liquor from paper production or lignin enriched with enzymes, which results, for example, from the phenylpropanoid biosynthesis of enzymatically produced lignin, it is surprisingly possible to convert industrial waste products without purification directly by the simple modification process according to the invention into high-quality lignin derivatives, which can be used in a wide variety of industrial processes, such as, for example, as sizing agents in paper production.They can be used as additives for the production of fuel pellets or as reinforcing material for polyolefins. This process achieves significant energy savings in the production of modified lignin, further improving the energy balance of the overall process.

[0013] According to a further development of the invention, the process according to the invention is carried out in such a way that the acidifying agent is selected from mineral acids, such as sulfuric acid, phosphoric acid, nitric acid, or hydrochloric acid; pH-reducing agents, such as carbon dioxide; carboxylic acids, such as acetic acid, lactic acid, oxalic acid, abietic acid, or citric acid, or mixtures of two or more thereof. The essential prerequisite for the selection of the acidifying agent is exclusively the pH achievable by using the selected acidifying agent, which, according to the invention, must be < 4.5.Mineral acids such as sulfuric acid or hydrochloric acid are particularly preferably used, in particular because these acids are strong acids which completely dissociate water in the dispersant used and, moreover, are required in the process, for example, in paper production, from which the starting material lignin or the lignin derivative can originate, so that, if necessary, waste products from industry can also be used directly.Such a procedure is preferred for reasons of sustainability. As corresponds to a further development of the process according to the invention, the process is carried out in such a way that the modifier is selected from fatty acids or chemically modified derivatives thereof, resin acids or chemically modified derivatives thereof, tall oils or tall oil soaps, softening at least one fatty or resin acid, or chemically modified derivatives thereof, terpenes and corresponding terpenoids or chemically modified derivatives thereof, synthetic paper sizing agents, aluminum sulfate, polyaluminum chloride or polymers and mixtures of polymers thereof, anionic polymers or mixtures of two or more thereof, it is possible to modify the lignin or the lignin derivative with agents commonly used in the paper industry, such as fixing agents, sizing agents, flocculation aids and the like.to treat and, surprisingly, to obtain a modified lignin derivative that has an increased calorific value and a lower specific energy of 1 kWh / t, thus positively impacting the energy balance of both paper production and the production of the modifier. Furthermore, the use of commonly used industrial products such as sizing agents, fixatives, or coagulation aids ensures that no substances are introduced into the modified lignin derivative that would be classified as environmentally harmful, for example, when fuel pellets or similar produced using this modified lignin derivative are burned, and thus may not be used or may only be used to a limited extent.

[0014] To reliably prevent the introduction of excess or potentially disruptive dispersants, solvents, modifiers, and the like into a product produced using the modified lignin derivative according to the invention, the process is essentially conducted such that the modified lignin derivative is filtered off from the suspension or dispersion in which it was formed and washed with water at least once, preferably several times. With such a process, the filtrate as well as the wash fractions can also be recycled or reused, for example, in paper production.

[0015] If, as is the case with a further development of the invention, the modified lignin derivative is not immediately subjected to further processing, such as mixing with wood fractions to produce pellets or fuels, or is used as a sizing agent in the paper industry, the filtered-off modified lignin derivative is dried with air, in particular in a possibly warm air stream, as is the case with a further development of the invention. A final product dried in this way can be stored for any length of time and can be used for final disposal either immediately or, preferably, after being reabsorbed in a suspending or dispersing agent, such as water, optionally mixed with ethanol.

[0016] Such a drying process can, as corresponds to a further development of the invention, be carried out in such a way that the filtered-off modified lignin is dried in an air stream for at least 8 hours at a temperature of at least 25°C, preferably at least 35°C. By drying the filtered-off modified lignin for a period of at least 8 hours at a temperature of at least 25°C, preferably at least 35°C, in an air stream, it is possible to allow the product to age further and to further advance the surface modification of the starting material used with the aid of the modifier also used, without softening or even oxidizing the product.Surprisingly, it has been shown that in such an aging process not only is residual solvent removed from the modified lignin derivative formed, but in particular the deposition of the modifier on the surface of the modified lignin derivative is improved, in particular the deposition via Van der Waals forces can be further enhanced.

[0017] According to a further development of the invention, the process is conducted such that step d) of adding at least one modifier before steps b) and c) surprisingly leads to an absolutely identical result with respect to the modified lignin derivative as if the process had been conducted such that the acidification is carried out first and only then the addition of the modifier. From this, it can be seen that the acidification step is essential for obtaining the modified lignin derivative.

[0018] The invention further aims to provide a modified lignin derivative which leads to an improvement in the energy balance of products containing it or in the processes for producing these products. To achieve this object, the modified lignin derivative is essentially characterized in that it contains at least 85% by weight, preferably at least 90% by weight, of lignin or a derivative thereof, as well as between 0.01 and 3% by weight of the absolute dry amount of the lignin or a derivative thereof, preferably between 0.5 and 2.5% by weight.-% of the absolute dry amount of lignin or a derivative thereof, one from the group of fatty acids or chemically modified derivatives thereof, resin acids or chemically modified derivatives thereof, tall oils or tall oil soaps containing at least one fatty or resin acid, or chemically modified derivatives thereof, terpenes and corresponding terpenoids or chemically modified derivatives thereof, synthetic paper sizing agents, aluminum sulfate, polyaluminum chloride or polymers and mixtures of polymers thereof, anionic polymers or mixtures of two or more modifiers selected from these, and the remainder water. By using a modified lignin derivative which contains at least 85% by weight, preferably at least 90% by weight of lignin and between 0.01 and 3.

[0019] % by weight, preferably between 0.5 and 2.5 wt. % of the absolutely dry amount of the lignin or a derivative thereof, of a modifier and the remainder water, the waste product lignin or a derivative thereof, which originates, for example, from paper production, in particular from black liquor, can essentially be activated with extremely small amounts of a product which is also commonly used, for example, in the paper industry as a modifier and by using the product formed therefrom, for example, the calorific value of fuels produced therewith, such as pellets, can be increased or the modified lignin derivative can in turn be used as a sizing agent in the paper industry, which also has a positive effect on the overall energy balance, since only extremely small amounts of a conventional sizing agent have to be used and the remainder of the modified lignin derivative is a waste product from paper production.

[0020] A lignin derivative modified in this way is even more effective if, as is the case with a further development of the invention, the modified lignin derivative has a molecular weight of 200 g / mol to 2500 g / mol measured by gel permeation chromatography. Lignin derivatives with such low to medium molecular weights are insoluble in cold water and only poorly soluble in warm water. However, they can be easily dissolved with the addition of solubilizers such as ethanol or the like. This allows them, unlike higher-molecular-weight products, to be easily and evenly applied and distributed onto substances to which they are to be added, such as a paper surface, fuel, or the like.In particular, a modified lignin derivative with a molecular weight of 200 g / mol to 2500 g / mol makes it possible to obtain completely uniformly coated surfaces, while at the same time only requiring extremely small amounts of the modified lignin derivative, which further improves the overall energy balance of both the products containing it and the modified lignin derivative itself. Surprisingly, it has been shown that such a modified lignin derivative can be used without further processing, either after drying and re-dissolving or re-dispersing, or directly from the process in dry form as an additive in biomass pellets, as a sizing agent in the paper industry, or as a reinforcing material in polyolefins.Surprisingly, all products containing the modified sizing agent exhibit significantly improved properties after the addition of the modified sizing agent. For example, the calorific value of biomass pellets produced in this way can be significantly increased, allowing sized paper to be hydrophobized with small amounts of the modified lignin derivative, or making polyolefins significantly stronger and, in particular, more hydrophobic than without the modified lignin derivative.

[0021] A preferred use of the modified lignin derivative according to the invention is essentially characterized in that the modifier selected from fatty acids or chemically modified derivatives thereof, resin acids or chemically modified derivatives thereof, tall oils or tall oil soaps containing at least one fatty or resin acid, or chemically modified derivatives thereof, terpenes and corresponding terpenoids or chemically modified derivatives thereof, synthetic paper sizing agents, aluminum sulfate, polyaluminum chloride or polymers and mixtures of polymers thereof, anionic polymers or mixtures of two or more thereof is present in an amount of between 0.2 and 3% by weight of the absolutely dry amount of the modified lignin derivative, preferably between 0.5 to 1.5% by weight.-% of the absolutely dry amount of the modified lignin derivative is contained, wherein the modified lignin derivative is contained in the biomass pellets in an amount of 0.2 to 2.9 wt.% of the biomass pellets, preferably 0.4 to 1.5 wt.% of the biomass pellets and that the remainder consists of sawdust, wood chips, reeds, miscanthus, shrubs or deciduous or coniferous trees with a size of less than or equal to 10 mm, preferably less than or equal to 7 mm, particularly preferably less than or equal to 5 mm.Compared to known products according to the prior art, biomass pellets produced with the modified lignin derivative contain an extremely low amount of the modifying agent while simultaneously containing comparatively high amounts of lignin. They can therefore be added to the pellets in small quantities. This can be done either directly in dried, powdered form or in liquid form, with the modified lignin derivative being dispersed or suspended in a dispersion or solvent. The dispersion medium used for this purpose is preferably water, optionally with the addition of small amounts of lignin.

[0022] Amounts of ethanol or propanol.

[0023] The invention is explained in more detail below using exemplary embodiments. These show:

[0024] Example 1

[0025] Process for the preparation of a modified lignin derivative from black liquor

[0026] Alkaline lignin or a derivative thereof is obtained from black liquor from paper production by filtration of the black liquor. 100 g of this solid alkaline lignin or a derivative thereof are mixed with water in a ratio of 1:8 (lignin:water), and the resulting dispersion is acidified with the addition of aqueous sulfuric acid until a pH of 2 is reached. The resulting dispersion can be subjected to fractional filtration, in particular to remove impurities, and the filter cake can be redissolved in filter water in a ratio of 1:8. However, this step is not mandatory for further processing. The acidified dispersion of lignin or a derivative thereof, adjusted to a pH of 2, is heated to a temperature of 80°C, and a solution containing 1.8 g of a modifier is added to the dispersion of lignin or a derivative thereof with vigorous stirring.Water is generally used as the solvent for the modifier. Only for modifiers that are insoluble or only slightly soluble in water can either a mixture of water and ethanol or pure ethanol be used as the solvent. The resulting dispersion is stirred for 30 minutes at a preselected temperature, in this case 80°C.

[0027] QC, stirred. The resulting modified lignin derivative is then allowed to settle from the dispersion and washed twice with 250 ml of water each time until the wash liquor reaches an approximately neutral pH. Based on this basic experimental design, various modifications were made. In a further experiment, the dispersion containing lignin derived from black liquor acidified with sulfuric acid or a derivative thereof, heated to 80 °C, was allowed to age for one hour before the addition of the dissolved modifier.

[0028] In further modifications to the basic process described above, the amount of modifier used was varied. The following modifiers were used: tall oil resin, concentrations: 0.4, 0.7, and 1%; polyaluminum chloride (a fixative used in the paper industry), concentrations: 0.4, 0.7, and 1%; a mixture of fatty acid and tall oil: concentrations of 0.4, 0.8, and 1%; and a mixture of alkyl ketene dimers and rosin, concentrations of 0.3, 0.7, and 1.2%. All modifiers were dissolved in ethanol or a mixture of ethanol and water.

[0029] Example 2 In a modification of the process of Example 1, the alkaline lignin or a derivative thereof filtered from the black liquor is dispersed in water in a ratio of 1:9, and the modifier is first added to this dispersion, and then the dispersion containing lignin or a derivative thereof and modifier is acidified to a pH of 2 with the addition of mineral acid (H2SO4 or HCl). The acidic mixture is stirred for 45 minutes at a temperature of 70 °C, the modified lignin derivative formed is allowed to settle and separated. The product can be used to produce fuel pellets without any further purification. If the modified lignin derivative formed is to be used as a sizing agent in the paper industry, the purification and drying step described in Example 1 follows after separation.The following modifiers were used: tall oil resin (concentrations of 0.4, 0.7, and 1%); polyaluminium chloride (a fixative used in the paper industry) (concentrations of 0.5, 0.7, and 1.1%); a mixture of fatty acid and tall oil (concentrations of 0.4, 0.8, and 1%); and a mixture of alkyl iketene dimer and rosin (concentrations of 0.3, 0.7, and 1.2%). All modifiers were dissolved in ethanol or a mixture of ethanol and water.

[0030] Example 3

[0031] Using the modified lignin derivatives described above, biomass pellets were produced and tested to determine how the modified lignin derivatives behave in comparison to unmodified lignin, which was added to the fuel pellets in comparable amounts.

[0032] The modified lignin derivatives obtained from Examples 1 and 2 were added to the biomass pellets in amounts between 0.5 and 2 wt.% of the biomass pellets, and the resulting biomass pellets were compared with biomass pellets to which the same amounts of unmodified lignin were added. It was shown that pellets containing unmodified lignin had a significantly increased surface free energy of 48.5 mJ / m². 2 compared to biomass pellets to which modified lignin derivatives were added according to Examples 1 and 2. Lignin derivatives modified according to Example 1 had a free surface energy of 45.77 mJ / m with the addition of tall oil resin as a modifier. 2 or a free surface energy of 42.8 mJ / m 2with the addition of AKD and rosin as modifiers. Lignin samples produced using the method according to Example 2 had a surface free energy of 44.8 mJ / m 2 with the addition of tall oil resin as a modifier and a free surface energy of 45.8 mJ / m 2 with the addition of a modifier based on fatty acid and tall oil resin.

[0033] It was shown that the addition of tall oil resin at a level of 1% had a positive effect on throughput in tonnes / hour and energy consumption in kWh / t, while maintaining consistent mechanical strength compared to pellets produced using cereal starch. Compared to pellets produced with unmodified lignin, throughput increased by 30%, mechanical strength increased by approximately 33% at a modifier concentration of 1% compared to unmodified lignins, and the impact on specific energy in kWh / t, i.e., energy consumption during production, was most pronounced with the addition of 1% of the modifier obtained according to Example 1, resulting in an improvement of 28% compared to the addition of unmodified lignin and an improvement of approximately 20% compared to the addition of conventional starch.Finally, a tall oil...

[0034] Lignin modified with resin according to the invention was investigated in comparison with pellets produced with a mixture of tall oil and lignin and it was found that in particular an energy saving of at least 15% could be achieved compared to pellets produced by merely mixing tall oil and lignin with the biomass.

[0035] The following table shows physical properties of biomass pellets produced with two concentrations of starch, unmodified lignin and modified lignin (modifier: tall oil, concentrations of 0.4 and 1% each) according to the invention.

[0036] From the table it can be seen that the throughput could be significantly increased compared to conventionally produced pellets and thus a particularly efficient process can be provided, both in terms of yield and energy consumption.

Claims

Patent claims 1 , Process for producing a modified lignin derivative, in which lignin or a derivative thereof is used as a starting material, which process is characterized by the steps: a) dispersing or suspending the lignin or the lignin derivative in water in a ratio between 1:3 and 1:10, preferably 1:5 and 1:9 and particularly preferably 1:7 and 1:8, b) adding at least one acidifying agent to the dispersion or suspension and adjusting a pH of the dispersion or suspension to values less than 4.5, preferably less than 2.5, particularly preferably pH 2; c) optionally heating the dispersion orSuspension to temperatures between 25 °C and 90 °C and adding water as a diluent; d) adding at least one modifier selected from the group of sizing agents, fixing agents, dispersants, flocculating agents or dewatering agents usable in paper production in an amount between 0.01 and 3 wt.% of the absolutely dry amount of the lignin or the derivative thereof, preferably between 0.5 to 2.5 wt.-% of the absolutely dry amount of the lignin or derivative thereof, wherein the modifying agent is optionally dissolved in a lower alcohol, such as ethanol; e) stirring the dispersion or suspension and maintaining the temperature for a period of at least 2 minutes, preferably more than 20 minutes and more preferably at least 30 minutes and especially preferably more than 50 minutes; f) allowing to settle and separating the modified lignin derivative and optionally g) washing with water and drying the modified lignin derivative.

2. The process according to claim 1, characterized in that the lignin or lignin derivative used as starting material is selected from: alkaline lignin obtained by precipitation from black liquor, lignin treated with enzymes, or mixtures thereof.

3. The process according to claim 1, characterized in that the acidifying agent is selected from mineral acids, such as sulfuric acid, phosphoric acid, nitric acid, or hydrochloric acid; pH-reducing agents, such as carbon dioxide; carboxylic acids, such as acetic acid, lactic acid, oxalic acid, abietic acid, or citric acid, or mixtures of two or more thereof.

4. A process according to claim 1, 2 or 3, characterized in that the modifying agent is selected from fatty acids or chemically modified derivatives thereof, resin acids or che- chemically modified derivatives thereof, tall oils or tall oil soaps, softening at least one fatty or resin acid, or chemically modified derivatives thereof, terpenes and corresponding terpenoids or chemically modified derivatives thereof, synthetic paper sizing agents, aluminum sulfate, polyaluminum chloride or polymers and mixtures of polymers thereof, anionic polymers or mixtures of two or more thereof.

5. Process according to one of claims 1 to 4, characterized in that the modified lignin derivative is filtered out of the suspension or dispersion and washed at least once, preferably several times, with water.

6. Process according to one of claims 1 to 5, characterized in that the filtered-off modified lignin derivative is dried with air, in particular in an air stream.

7. The method according to claim 6, characterized in that the filtered-off modified lignin is dried in an air stream for at least 8 hours at a temperature of at least 25 °C, preferably at least 35 °C.

8. The method according to claim 1, characterized in that step d) is carried out before steps b) and c).

9. Modified lignin derivative, produced according to a process according to one of claims 1 to 8, characterized in that it contains at least 85% by weight, preferably at least 90% by weight of lignin or a derivative thereof and between 0.01 and 3% by weight of the absolutely dry amount of the lignin or a derivative thereof, preferably between 0.5 and 2.5% by weight.-% of the absolute dry amount of lignin or a derivative thereof selected from the group of fatty acids or chemically modified derivatives thereof, resin acids or chemically modified derivatives thereof, tali oils or tall oil soaps containing at least one fatty or resin acid, or chemically modified derivatives thereof, terpenes and corresponding terpenoids or chemically modified derivatives thereof, synthetic paper sizing agents, aluminum sulfate, polyaluminum chloride or polymers and mixtures of polymers thereof, anionic polymers or mixtures of two or more of these selected modifiers, and the remainder being water.

10. Modified lignin derivative according to claim 9, characterized in that the modified lignin derivative has a molecular weight of 200 g / mol to 2500 g / mol measured by gel permeation chromatography.

11. Use of a modified lignin derivative prepared according to any one of claims 1 to 8 as an additive in biomass pellets, sizing agent in the paper industry, or reinforcing material in polyolefins. 12.Biomass pellets containing a modified lignin derivative obtained by modifying lignin or a derivative thereof according to one of claims 1 to 8, characterized in that the modifying agent selected from fatty acids or chemically modified derivatives thereof, resin acids or chemically modified derivatives thereof, tall oils or tall solder soaps containing at least one fatty or resin acid, or chemically modified derivatives thereof, terpenes and corresponding terpenoids or chemically modified derivatives thereof, synthetic paper sizing agents, aluminum sulfate, polyaluminum chloride or polymers and mixtures of polymers thereof, anionic polymers or mixtures of two or more thereof, in an amount of between 0.2 and 3% by weight of the absolutely dry amount of the modified lignin derivative, preferably 0.5 to 1.5% by weight.-% of the absolutely dry amount of the modified lignin derivative is contained, that the modified lignin derivative is contained in the biomass pellets in an amount of 0.2 to 2.9 wt.% of the biomass pellets, preferably 0.4 to 1.5 wt.% of the biomass pellets and that the remainder consists of sawdust, wood chips, reeds, miscanthus, shrubs or deciduous or coniferous trees with a size of less than or equal to 10 mm, preferably less than or equal to 7 mm, particularly preferably less than or equal to 5 mm.

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