EP3997157A1

EP3997157A1 - Method for producing stabilized lignin having a high specific surface

Info

Publication number: EP3997157A1
Application number: EP20746890.1A
Authority: EP
Inventors: Tobias Wittmann; Jacob Podschun
Original assignee: Suncoal Industries GmbH
Current assignee: Suncoal Industries GmbH
Priority date: 2019-07-10
Filing date: 2020-07-10
Publication date: 2022-05-18
Also published as: WO2021005230A1; BR112022000235A2; CA3145637A1; KR20220034139A; JP2022539854A; US20220332744A1; CN114080413A

Abstract

The invention relates to a method for producing stabilized lignin from lignin-containing raw materials, comprising two process steps. The invention also relates to the stabilized lignin produced in this way.

Description

Process for the production of a stabilized lignin with a high specific surface

State of the art

Lignin from hardwood, coniferous wood and annual plants shows a high solubility in many polar and alkaline media after extraction / recovery in the form of, for example, kraft lignin, lignosulfonate or hydrolysis lignin. Lignins show a glass transition at temperatures of mostly 80 ° C - 150 ° C. Softening changes the microscopic structure of lignin particles even at low temperatures. Lignin-containing materials are therefore usually not resistant to elevated temperatures or change their properties. Furthermore, the solubility of lignin in polar solvents such as dioxane and acetone with e.g. 10% water or in alkaline solvents is usually> 95% (Sameni et al., BioResources, 2017, 12, 1548-1565; Podschun et al., European Polymer Journal, 2015, 67, 1 -1 1). Because of these and other properties, lignin can only be used to a limited extent in material applications (DE102013002574A1).

In the following, lignin means the sum of Klason and acid-soluble lignin. The dry matter also contains other organic and inorganic components.

In order to overcome these disadvantages, it was proposed to produce a stabilized lignin by hydrothermal carbonization, which is characterized by a softening temperature (glass transition temperature) of more than 200 ° C. (WO2015018944A1). A stabilized lignin with a defined particle size distribution can be obtained by adjusting the pH value (WO2015018944A1).

Improved processes use lignin as a raw material for the production of particulate carbon materials, which can be used, for example, as functional fillers in elastomers (WO2017085278A1). An essential quality parameter for functional fillers is the outer surface of the particulate carbon material, which is determined by measuring the STSA. Such processes make use of hydrothermal carbonization of a lignin-containing liquid, usually at temperatures between 150 ° C and 250 ° C. Due to the high reactivity of the lignin at such temperatures, a fine adjustment between pH-value, ionic strength and lignin content of the lignin-containing liquid as well as the temperature and the time of the hydrothermal is necessary to achieve high specific surface areas Carbonation required. This is achieved by setting the pH value in the alkaline range, usually to values above 7.

For such particulate carbon materials, different applications in materials open up compared to the respective starting lignins. For example, due to the low solubility of less than 40% and a specific surface area of more than 5 m ² / g and less than 200 m ² / g in elastomers, they can be used as reinforcing fillers and completely or partially substitute for carbon black.

The disadvantage of this process is the low yield, which is usually between 40% and 60%. A further disadvantage of this method is the high cost of adapting the properties of the lignin-containing liquid (pH value, ionic strength, lignin content) to the process parameters of the hydrothermal carbonization (temperature and residence time) in order to achieve ever higher specific surface areas. While it is easy to achieve surfaces in the range of 5 m ² / g up to 40 m ² / g, the achievement of specific surface areas above 40 m ² / g is more likely in the laboratory than on an industrial scale due to the required sensitivity of the above coordination possible. It can be assumed that such an adaptation with the aim of increasing the specific surface area leads to a reduction in the yield.

A known method for increasing the yield of solids and increasing lignin conversion for the production of fuels from a suspension of dried black liquor and water by hydrothermal carbonization at temperatures between 220 ° C and 280 ° C is the addition of formaldehyde [Bioressource Technologie 2012 , 1 10 715-718, Kang et al.]. Kang et al. suggests the addition of 37g formaldehyde based on 100g dry lignin at a solids concentration of 20% (100ml of a 2.8% formaldehyde solution based on 25 g dry matter obtained by drying black liquor with 30% lignin based on the dry matter). This increases the conversion of the lignin contained in the black liquor into solids from 60% - 80% to values between 90% and 100%, the highest values being achieved at temperatures between 220 ° C and 250 ° C. This prior art attributes the increase in yield to the polymerization between formaldehyde, the solid of the black liquor and the carbonization products formed from this solid (page 716, last paragraph). Disadvantage of this prior art is the high specific dosage of formaldehyde of 37g to 100g of lignin, the high ash content of the dry matter used and the products made from it, - the polymerization between formaldehyde, the solid of the black liquor and the carbonization products formed from this solid and the associated Restricting the use of the product to fuel applications.

description

The aim of the present invention is to find a process which leads to a stabilized lignin which is suitable for material applications with a high yield.

The object of the invention is to provide a method which reduces the solubility of the lignin in alkaline and / or polar media - increases or eliminates the glass transition temperature of the lignin, leads to a stabilized lignin with advantageous particle properties and has a high yield.

Accordingly, according to a first variant, a method for producing an undissolved stabilized lignin with an STSA surface area of at least 10 m ² / g from lignin-containing raw materials is provided, with a lignin dissolved in a liquid and a crosslinking agent being reacted in a first process step and so on a dissolved modified lignin is generated, and in a second process step the dissolved modified lignin is converted into an undissolved stabilized lignin. Preferred lignin-containing raw materials are in particular:

Black liquor from the force digestion of woody biomass or solids produced from it (e.g. LignoBoost Lignin, LignoForce Lignin), Solids from enzymatic hydrolysis of woody biomass,

Black liquor from the digestion of woody biomass with sulfites (lignosulfonates) or solids or liquids produced from them from the digestion of woody biomass with solvents or solids produced from it (e.g. Organosolv Lignin).

If the lignin-containing raw materials are solids, the lignin contained therein must be completely or partially dissolved in a liquid before the first process stage. Methods for dissolving lignin in liquids are state of the art.

In addition to the dissolved lignin, which is reacted with the crosslinker in the first process stage, undissolved lignin can also be present in the liquid in dispersion. For the present method it is therefore not necessary for all of the lignin to be dissolved in the liquid. Advantageously, however, more than 50%, particularly preferably more than 60%, furthermore preferably more than 70%, particularly preferably more than 80%, in particular more than 90% of the lignin is dissolved in the liquid.

A dissolved modified lignin is understood, in particular, to mean that the aromatics in the lignin are primarily connected via ether bonds; the proportion of para-substituted phenolic rings in the total proportion of aromatic rings is greater than 95%, preferably greater than 97%, particularly preferably greater than 99 %, and the content of free phenol is below 200 ppm, preferably below 100 ppm, moreover preferably below 75%, particularly preferably below 50 ppm

The content of clason lignin is at least 70%, preferably at least 75%, particularly preferably at least 80%, in particular at least 85%

The phenol content is determined in accordance with DIN ISO 8974. The content of clason lignin is determined as acid-insoluble lignin according to TAPPI T 222.

In the context of the present invention, the term “undissolved stabilized lignin” is understood to mean the solid which can be separated from the liquid following the second process stage. The undissolved stabilized lignin is difficult to dissolve in alkaline liquids and has a low porosity. The properties of the stabilized lignin obtained by the present process are described in detail below. According to this first variant, an improved method for producing an undissolved stabilized lignin from lignin-containing raw materials is advantageously provided, with a lignin dissolved in a liquid in a first process step, the lignin having phenolic aromatics, aromatic and aliphatic hydroxyl groups and / or carboxy groups as crosslinkable units ; and a crosslinker, the crosslinker having at least one functional group as a crosslinkable unit that can react with the crosslinkable units of the lignin, at a first temperature T1, which is between a first maximum temperature T 1 max and a first minimum temperature T1 min, via a a defined period of time to react and thus a dissolved modified lignin is generated, and in a second process stage the dissolved modified lignin at a second temperature T2, which is between a second maximum temperature T2max and a second minimum temperature T2min T2, over a defined period of time undissolved stabilized lignin is transferred.

The present method increases the yield of undissolved stabilized lignin significantly compared to a process control without the reaction with a crosslinker in a first process stage.

The two-stage process control can advantageously influence the conditions under which the respective process stage is carried out.

Through the reaction of the crosslinker with the lignin dissolved in the liquid in the first process stage, a high selectivity of the reaction can be guaranteed and a dissolved modified lignin can be obtained in a targeted manner, which is then converted into an undissolved stabilized lignin in the second process stage. By realizing the first process stage in the solution, the polymerization of the crosslinker with the lignin and, if applicable, the carbonization products formed from the lignin, is reduced or completely suppressed. By converting the modified, dissolved lignin into a stabilized, undissolved lignin in the second process step, the particle properties of the stabilized, undissolved lignin can be influenced in a targeted manner. In this way, advantageous particle properties can be set. The two-stage process control of the present process surprisingly results in a stabilized lignin whose yield and specific surface area is significantly higher than that of a stabilized lignin which is produced from the same starting material according to the prior art without reacting with a crosslinker in the first process stage has been.

Furthermore, a stabilized lignin is surprisingly obtained through the two-stage process management of the present method, the yield and specific surface area of which is significantly higher than that of a stabilized lignin, which reacts with a crosslinker, but in a one-stage process from the same starting material according to the prior art Technology was generated.

The yield of undissolved stabilized lignin based on the dissolved lignin is preferably more than 60%, preferably more than 70%, particularly preferably more than 80%, in particular more than 85%.

In one embodiment of the above process variant, the crosslinking compound is added in the first process stage.

The crosslinker is preferably metered in such that the amount is a maximum of 4 mol, preferably a maximum of 3 mol, more preferably a maximum of 2.5 mol, particularly preferably a maximum of 2 mol, furthermore preferably a maximum of 1.75, in particular a maximum of 1.5 mol of crosslinkable units of the crosslinker per mole of crosslinkable units of the lignin used.

The crosslinker is preferably metered in such that the amount is at least 0.5 mol, preferably at least 0.75 mol, more preferably at least 1 mol, particularly preferably at least 1.1 mol, especially at least 1.15 mol of crosslinkable units of the crosslinker per mole of crosslinkable units of the lignin used.

According to a second variant, a method for producing a stabilized lignin from lignin-containing raw materials is provided, wherein in a first process stage a lignin dissolved in a liquid, the lignin having phenolic aromatics, aromatic and aliphatic hydroxyl groups and / or carboxy groups as crosslinkable units; and a crosslinker, wherein the crosslinker has at least one functional group as a crosslinkable unit which can react with the crosslinkable units of the lignin and the amount of crosslinking compound is selected such that the crosslinkable units of the crosslinker between 0.5 and 4 mol / mol of crosslinkable units of the lignin are reacted and thus a dissolved modified lignin is generated, and in a second process step the dissolved modified lignin at a second temperature T2, which is between a second maximum temperature T2max and a second The minimum temperature T2min is T2, which is converted into an undissolved stabilized lignin over a defined period of time.

Accordingly, an alternative method is also provided in which an optimal amount of crosslinker is selected in relation to the amount of lignin used, but a defined temperature control is not required in the first process stage. This is because it has surprisingly been shown that the yield and specific surface area of the stabilized carbonized lignin obtained can be significantly increased if an optimal amount of crosslinker is selected.

In one embodiment of the second process variant, the first process stage can be supplemented in analogy to the first process variant. According to such a combination of the first with the second process variant, an advantageous process for the production of a stabilized lignin from lignin-containing raw materials is provided, with a lignin dissolved in a liquid in a first process step, the lignin being phenolic aromatics, aromatic and aliphatic hydroxyl groups and / or carboxy groups as networkable units; and a crosslinker, wherein the crosslinker has at least one functional group as a crosslinkable unit which can react with the crosslinkable units of the lignin, and the amount of crosslinking compound is selected so that the crosslinkable units of the crosslinker between 0.5 and 4 mol / mol of crosslinkable units of the lignin are at a first temperature T1, which is between a first maximum temperature T1 max and a first minimum temperature T1 min, are reacted over a defined period of time and a dissolved modified lignin is thus generated, and in a second process stage the dissolved modified lignin at a second temperature T2, which is between a second maximum temperature T2max and a second minimum temperature T2min T2, is converted into an undissolved stabilized lignin over a defined period of time. Crosslinkers can react in the lignin with free ortho and para positions on phenolic rings (phenolic guaiacyl groups and p-hydroxyphenyl groups). Suitable crosslinkers for reaction at free ortho and para positions on phenolic rings are, for example, aldehydes such as formaldehyde, furfural, 5-HMF, hydroxybenzaldehyde, vanillin, syringaldehyde, piperonal, glyoxal, glutaraldehyde or sugar aldehydes. Preferred crosslinkers for the reaction on phenolic rings are formaldehyde, furfural and sugar aldehydes (ethanals / propanals) such as glyceraldehyde and glycolaldehyde.

Furthermore, crosslinkers can react with aromatic and aliphatic OH groups (phenolic guaiacyl groups, p-hydroxyphenyl groups, syringyl groups) in the lignin. For this purpose, for example, preferably bifunctional and also multi-functional compounds with epoxy groups such as glycidyl ether, isocyanate groups such as diisocyanate or oligomeric diisocyanate or acid anhydrides can be used. Preferred crosslinking agents for the reaction on aromatic and aliphatic OH groups are isocyanates and acid anhydrides.

Crosslinkers can also react with carboxyl groups. For example, diols and triols can be used for this purpose. Preferred crosslinkers for the reaction with carboxyl groups are diols.

Furthermore, crosslinkers can react with phenolic rings, aromatic and aliphatic OH groups and carboxyl groups. For this purpose, for example, preferably bifunctional and also multi-functional compounds with at least two of the above-mentioned functional crosslinking groups can be used.

When crosslinking agents that react with the phenolic ring are used, crosslinkable units of the lignin used are phenolic guaiacyl groups and p-hydroxyphenyl groups. The concentration of crosslinkable units (mmol / g) is determined, for example, via 31 P NMR spectroscopy (Podschun et al., European Polymer Journal, 2015, 67, 1 -1 1), with guaiacyl groups one crosslinkable unit and p-hydroxyphenyl groups two crosslinkable Units included.

With crosslinkable units of the lignin used, when crosslinkers are used that react with aromatic and aliphatic OH groups, all aromatic and aliphatic OH groups are meant. The concentration of crosslinkable units (mmol / g) is determined, for example, via 31 P NMR spectroscopy, with all groups containing a crosslinkable unit. When crosslinking agents that react with carboxyl groups are used, crosslinkable units of the lignin used mean all carboxyl groups. The concentration of crosslinkable units (mmol / g) is determined, for example, via 31 P NMR spectroscopy, with all groups containing a crosslinkable unit.

When using bi-functional crosslinkers, two moles of crosslinkable units are available per mole of bi-functional crosslinker. Accordingly, when using tri-functional crosslinkers, three moles of crosslinkable units are available per mole of tri-functional crosslinker, etc.

The amount of crosslinker is preferably a maximum of 35 g / 100 g lignin, preferably a maximum of 30 g / 100 g lignin, particularly preferably a maximum of 25 g / 100 g lignin.

The amount of formaldehyde is preferably a maximum of 25 g / 100 g lignin, preferably a maximum of 20 g / 100 g lignin, particularly preferably a maximum of 15 g / 100 g lignin, in particular a maximum of 12 g / 100 g lignin. The amount of formaldehyde added can thus be in a range between 1 -20 g / 100 g lignin, preferably between 5-15 g / 100 g lignin, particularly preferably between 6-10 g / 100 g lignin.

The temperature of the first process stage is advantageously more than 50 ° C., preferably more than 60 ° C., particularly preferably more than 70 ° C. and less than 180 ° C., preferably less than 150 ° C., more preferably less than 130 ° C., particularly preferred less than 100 ° C.

The average residence time in the first process stage is advantageously at least 5 minutes, more preferably at least 10 minutes, more preferably at least 15 minutes, particularly preferably at least 30 minutes, in particular at least 45 minutes, but less than 300 minutes.

An advantageous combination of time and temperature window for the first process stage is a minimum temperature of 50 ° C and a maximum temperature of 180 ° C with a residence time of at least 15 minutes, preferably at least 20 minutes, more preferably at least 30 minutes, particularly preferably at least 45 minutes . An alternatively advantageous combination of time and temperature window for the first process stage is a minimum temperature of 50 ° C and a maximum temperature of 130 ° C with a residence time of at least 10 minutes, preferably at least 15 minutes, more preferably at least 20 minutes, particularly preferably at least 30 minutes, especially at least 45 minutes. In a particularly preferred embodiment, the mixture of dissolved lignin and the at least one crosslinking compound is held in the first process stage at a temperature T1 between 50 ° C. and 180 ° C. for a residence time of at least 20 minutes, preferably at least 60 minutes.

In a further particularly preferred embodiment, the mixture of dissolved lignin and the at least one crosslinking compound is held in the first process stage at a temperature T1 between 70 ° C and 130 ° C for a dwell time of at least 10 min, preferably at least 50 min.

The liquid containing the dissolved lignin and the crosslinking agent can advantageously be heated during the first process stage. The heating rate is preferably less than 15 Kelvin per minute, more preferably less than 10 Kelvin per minute, particularly preferably less than 5 Kelvin per minute.

The temperature in the first process stage is advantageously kept largely constant over a period of at least 5 minutes, preferably at least 10 minutes, more preferably at least 15 minutes, particularly preferably at least 30 minutes.

A combination of heating and keeping the temperature constant in the first process stage is also advantageous.

The pressure is preferably at least 0.2 bar and preferably a maximum of 20 bar above the saturated steam pressure of the liquid containing the lignin.

The pH value of the liquid containing the dissolved lignin before the first process stage is advantageously above the pH value of the liquid containing the modified dissolved lignin after the first process stage.

The pH value of the liquid containing the dissolved lignin before the first process stage is advantageously more than 7, preferably more than 7.5, further preferably more than 8, particularly preferably more than 8.5 but less than 12.5.

The pH value of the liquid containing the dissolved modified lignin after the first process stage is advantageously more than 6.5, preferably more than 7, preferably more than 8 but less than 12.

The pH value of the liquid containing the dissolved modified lignin after the first process stage is preferably at least 0.2, preferably at least 0.5 units, particularly preferably at least 1 unit below the pH value of the liquid containing the dissolved lignin before the first process stage.

The proportion of lignin based on the total mass of the liquid containing the dissolved lignin in the first process stage is advantageously between 3% and 25%, preferably less than 20%, particularly preferably less than 18%.

The temperature of the second process stage is advantageously less than 270 ° C, preferably less than 260 ° C, more preferably less than 250 ° C, furthermore preferably less than 240 ° C, further preferably less than 230 ° C, furthermore particularly preferably at less than 220.degree. C., in particular at less than 215.degree.

In an advantageous embodiment, the temperature of the second process stage is at least 150.degree. C., preferably at least 160.degree. C., particularly preferably at least 170.degree.

The temperature of the second process stage can therefore vary within a wide range between 150 ° C and 250 ° C.

In a particularly preferred embodiment, the second reaction stage corresponds to a hydrothermal treatment, the temperature T2 of the hydrothermal treatment being between 150 ° C and 250 ° C, preferably between 170 ° C and 240 ° C, particularly preferably between 175 ° C and 235 ° C .

The average residence time in the second process stage is advantageously at least 10 minutes, more preferably at least 30 minutes, particularly preferably at least 45 minutes, but less than 600 minutes, preferably less than 480 minutes, particularly preferably less than 450 minutes.

The pH value of the liquid containing the modified, dissolved lignin before the second process stage is advantageously above the pH value of the liquid containing the undissolved stabilized lignin after the second process stage. The pH of the liquid containing the undissolved stabilized lignin after the second process stage is advantageously more than 5, preferably more than 6 but less than 11. The pH of the liquid containing the undissolved stabilized lignin after the second process stage is preferably at least 0.2, preferably at least 0.5 units, particularly preferably at least 1 unit below the pH value of the liquid containing the dissolved modified lignin before the second process stage.

The proportion of lignin based on the total mass of the liquid containing the modified, dissolved lignin is advantageously between 3% and 25% in the second process stage, preferably less than 20%, particularly preferably less than 18%.

The crosslinker is advantageously generated in situ during the first process stage. The advantage of generating a crosslinker in the first process stage is that the amount of crosslinker added in the first process stage can be reduced or omitted entirely.

The crosslinker is advantageously generated in situ from carbohydrates (preferably cellulose, hemicelluloses or glucose) which are dispersed or dissolved in the liquid containing the dissolved lignin during the first process stage. Carbohydrates, preferably cellulose, hemicelluloses or glucose, can preferably be added to the liquid containing the dissolved lignin, or these are already present. In such an advantageous procedure, for example - in a first process stage o a carbohydrate-based crosslinker, preferably aldehydes, preferably glyceraldehyde or glycolaldehyde, is obtained from carbohydrates dissolved or dispersed in the liquid containing the dissolved lignin, o the lignin and carbohydrate dissolved in the liquid -based crosslinkers are brought to reaction and thus a dissolved modified lignin is produced, and in a second process step the dissolved modified lignin is converted into an undissolved stabilized lignin.

During the first process stage, the crosslinking agent is advantageously generated in situ from the lignin that is dispersed or dissolved in the liquid containing the dissolved lignin. In such an advantageous procedure, for example, in a first process stage o a lignin-based crosslinker, preferably aldehyde, preferably methanediol or glycolaldehyde, obtained from carbohydrates dissolved or dispersed in the liquid containing the dissolved lignin, o the remaining lignin dissolved in the liquid and the lignin-based crosslinker reacted and so a produced dissolved modified lignin, and in a second process stage the dissolved modified lignin is converted into an undissolved stabilized lignin.

The undissolved stabilized lignin preferably has advantageous particle properties which enable use in material applications. The undissolved stabilized lignin preferably has a particle size distribution D50 of less than 500 g, preferably less than 300 gm, more preferably less than 200 gm, in particular less than 100 gm, particularly preferably less than 50 gm. The undissolved stabilized lignin preferably has a D50 Grain size distribution of more than 0.5 gm, preferably of more than 1 gm, particularly preferably of more than 2 gm.

The measurement of the grain size distribution of the stabilized lignin takes place in a suspension with distilled water by means of laser diffraction according to ISO 13320. Before and / or during the measurement of the grain size distribution, the sample to be measured is dispersed with ultrasound until a grain size distribution stable over several measurements is obtained.

The undissolved stabilized lignin preferably has an STSA of at least 10 m ² / g, more preferably at least 20 m ² / g. The STSA is preferably less than 200 m ² / g. STSA (Statistical Thickness Surface Area) is an indication of the outer surface of the stabilized lignin particles.

In a variant of the present stabilized lignin or particulate carbon material, the STSA surface has values between 10 m ² / g and 180 m ² / g, preferably between 20 m ² / g and 180 m ² / g, more preferably between 35 m ² / g and 180 m ² / g, particularly preferably between 40 m ² / g and 180 m ² / g.

The BET surface of the present stabilized lignin advantageously deviates from the STSA surface by only a maximum of 20%, preferably a maximum of 15%, more preferably a maximum of 10% from. The BET surface area is determined as the total surface area from the outer and inner surface using the nitrogen surface according to Brunauer, Emmett and Teller.

The undissolved, stabilized lignin is preferably present dispersed in water at the end of the second process stage.

The undissolved stabilized lignin is preferably not very porous. The pore volume of the stabilized lignin is advantageously <0.1 cm ³ / g, more preferably <0.01 cm ³ / g, particularly preferably <0.005 cm ³ / g. This distinguishes the present stabilized lignin from finely divided porous materials such as ground biogenic powdered activated carbon, which in addition to a BET surface area of generally more than 500 m ² / g can also have an STSA surface area of a maximum of 10 m ² / g.

The undissolved, stabilized lignin differs through the preferred advantageous particle properties, for example the D50 of the particle size distribution of less than 500 μm or the STSA of more than 10 m ² / g, preferably more than 20 m ² / g, of lignin-based resins, which by a reaction with formaldehyde was generated and converted from the solution into a duromer via the gel state.

The BET surface area and the STSA surface area are determined in accordance with the ASTM D 6556-14 standard. In the present invention, in deviation from this, the sample preparation / outgassing for the STSA and BET measurement takes place at 150.degree.

An undissolved stabilized lignin is the solid that can be separated from the liquid by solid-liquid separation after the second process stage. Such a solid-liquid separation is, for example, centrifugation or filtration.

The undissolved stabilized lignin is preferably only partially soluble in alkaline liquids. The solubility of the undissolved stabilized lignin is preferably less than 30%, preferably less than 25%, particularly preferably less than 20%.

The alkaline solubility of the undissolved stabilized lignin is determined as follows:

1 . The undissolved stabilized lignin is separated from the liquid by centrifugation and washed twice with distilled water. The supernatant is decanted off in each case.

2. The product from 1 is dried at 105 ° C. for 24 hours. 3. There is a suspension of the product from 2 with a concentration of 6.6 Ma. % and 0.1 M NaOH and thus an alkaline suspension. If the pH value is below 10 after the addition of the sodium hydroxide solution, further sodium hydroxide solution is added.

4. The alkaline suspension is stirred at 25 ° C. for 2 hours.

5. The alkaline suspension is then centrifuged at 6000 x g.

6. The supernatant from the centrifugation is filtered through a Por 4 frit.

7. The solid after centrifugation is washed twice with distilled water by repeating 4 to 6.

8. The solid after centrifugation and the residues on the Por 4 frit are dried at 105 ° C. and measured.

9. The alkaline solubility of the lignin-rich solid is calculated as follows:

Alkaline solubility of lignin-rich solid [%] = mass of the undissolved fraction from after centrifugation, filtration and drying [g] / mass of the product obtained in point 2 [g] ^* 100

The undissolved stabilized lignin preferably has a glass transition temperature of more than 160 ° C, more preferably more than 180 ° C, particularly preferably more than 200 ° C, in particular more than 250 ° C. Preferably, no glass transition temperature can be measured in the case of the undissolved stabilized lignin.

The glass transition temperature is measured after solid-liquid separation, washing and drying on dry, undissolved stabilized lignin in accordance with DIN 53765.

According to the invention, an undissolved stabilized lignin with: an STSA of at least 10 m ² / g, more preferably at least 20 m ² / g. The STSA is preferably less than 200 m ² / g a signal in the solid ¹³ C-NMR at 0 to 50 ppm, preferably at 10 to 40 ppm, particularly preferably at 25 to 35 ppm with an intensity compared to the signal of the methoxy groups at 54 to 58 ppm of 1-80%, preferably 5- 60%, particularly preferably 5-50% and a ¹³ C-NMR signal at 125 to 135 ppm, preferably at 127 to 133 ppm, which is increased compared to the lignin used

a ¹⁴ C content which corresponds to that of renewable raw materials, preferably greater than 0.20 Bq / g carbon, particularly preferably greater than 0.23 Bq / g carbon, but preferably less than 0.45 Bq / g carbon in each case

a carbon content based on the ash-free dry substance between 60% by mass and 80% by mass, preferably between 65% by mass and 75% by mass

a glass transition temperature of more than 160 ° C, more preferably of more than 180 ° C, particularly preferably of more than 200 ° C, in particular of more than 250 ° C. Preferably, no glass transition temperature can be measured in the case of the undissolved stabilized lignin.

a pore volume of the stabilized lignin of less than 0.1 cm ³ / g, more preferably less than 0.01 cm ³ / g, particularly preferably less than 0.005 cm ³ / g.

The present invention is explained in more detail below on the basis of exemplary embodiments with reference to the figures. Show it:

FIG. 1 shows a diagram with the results of a first embodiment according to FIG

Embodiment 1;

FIG. 2 shows a 13C-NMR spectrum of a stabilized lignin obtained in accordance with embodiment 1;

FIG. 3 shows a diagram with the results of a second embodiment according to

Embodiment 2,

FIG. 4 shows a diagram with the temperature profiles from exemplary embodiments 1 and 2;

Figure 5 is a diagram to illustrate the influence of the amount of used

Crosslinker for yield and BET value of a stabilized Lingnis produced according to embodiment 3; and

FIG. 6 13C-NMR spectrum of a stabilized lignin obtained in accordance with embodiment 3; Embodiments

In the following examples, the BET is given instead of the STSA. However, BET and STSA do not differ from one another by more than 10% for the undissolved stabilized lignins produced here.

Example 1 The raw material for this example is the solid from an enzymatic hydrolysis of woody biomass (hardwood). The solid was converted into a liquid containing dissolved lignin by adding water and sodium hydroxide solution.

To each 30 g of the dissolved lignin-containing liquid with a dry matter content of 15% and a pH value of 10.9, an amount of 23.5% formaldehyde solution defined in Table 1 was added in the first process stage for the reaction with the crosslinker formaldehyde. The liquid containing the dissolved lignin and the formaldehyde solution were homogenized and treated for the times and temperatures given in Table 1 in the first process step and a modified dissolved lignin was produced and then treated in the second process step and an undissolved stabilized lignin was produced. The undissolved stabilized lignin was recovered by centrifugation. After washing twice with demineralized water and drying in a circulating air drying cabinet, the yields given in Table 1 and FIG. 1 were obtained. The specific surface area (BET) in Table 1 and FIG. 1 was determined after heating at 150 ° C. in a vacuum).

The dry mass used has a lignin content of 88%. The lignin content of the dry matter used has 1.3 mmol / g phenolic guaiacyl groups and 0.1 mmol / g p-hydroxyphenyl groups and thus 1.5 mmol / g crosslinkable units.

The formaldehyde used has 66.6 mmol crosslinkable units / g dry formaldehyde.

Table 1: Variants of the experiments under Example 1 with different additive concentrations

As can be seen from Table 1 above, the yield and BET of the lignin material produced depend on the amount of crosslinker used and the use of an upstream, first reaction stage.

The examples with the numbers D, E and F show that the use of a first process step leads to an increase in the BET of the material obtained with the amount of crosslinker remaining the same. If the first reaction stage is carried out over a period of 71 min or 85 min, the BET value (No. E) is doubled compared to a shortened first reaction stage.

The BET (No. B-F) also initially increases as the amount of crosslinker increases, but falls as the amount of crosslinker increases further (No. G).

A similar effect can be seen in exemplary embodiment 2 (see Table 2 below). Here, doubling the amount of crosslinking agent leads to a reduction in the BET and the yield of the stabilized lignin (No. I and L). This clearly results in an optimum amount of crosslinker used.

¹³ C-formaldehyde was used in No. E2 and analyzed by means of solid-state NMR spectroscopy. The spectra of the lignin and stabilized lignin used are shown in FIG. 2 and show at 11 to 36 ppm the preferred formation of methylene groups with the central signal at 24 to 32 ppm with two guaiacyl units as the structure of the stabilized lignin

Example 2

The raw material for this example is LignoBoost Lignin obtained from a black liquor from a Kraft digestion. The solid was converted into a liquid containing the dissolved lignin by adding water and sodium hydroxide solution. To each 30 g of a liquid containing dissolved lignin with a dry matter content of 15% and a pH value of 9.2, an amount of 23.5% formaldehyde solution as defined in Table 2 was added in the first process stage for the reaction with the crosslinker formaldehyde. The liquid containing the dissolved lignin and the formaldehyde solution were homogenized and treated for the times and temperatures given in Table 2 in the first process step and a modified dissolved lignin was produced and then treated in the second process step and an undissolved stabilized lignin was produced. The undissolved stabilized lignin was recovered by centrifugation. After washing twice with demineralized water and drying in a circulating air drying cabinet, the yields given in Table 2 and FIG. 3 were obtained. The specific surface area (BET) in table 2 and FIG. 3 of the undissolved stabilized lignin was determined after baking at 150 ° C. in a vacuum.

The lignin used has 1.9 mmol / g phenolic guaiacyl groups and 0.3 mmol / g p-hydroxyphenyl groups and thus 2.5 mmol / g crosslinkable units.

The formaldehyde used has 66.6 mmol of crosslinkable units 1 g of dry formaldehyde.

Table 2: Variants of the experiments under Example 2 with different additive concentrations In the diagram in FIG. 4, the temperature curves from Examples 1 and 2 are summarized.

Example 3 The raw material for this example is LignoBoost Lignin obtained from a black liquor from a Kraft digestion. The solid was converted into a liquid containing the dissolved lignin by adding water and sodium hydroxide solution.

To each 30 g of a liquid containing dissolved lignin with a dry matter content of 15% and a pH of 8.7, an amount of a 23.5% formaldehyde solution as defined in Table 3 was added in the first process stage for the reaction with the crosslinking agent formaldehyde. The liquid containing the dissolved lignin and the formaldehyde solution were homogenized and treated for the times and temperatures given in Table 3 in the first process step and a modified dissolved lignin was produced and then treated in the second process step and an undissolved stabilized lignin was produced. The undissolved stabilized lignin was recovered by filtration. After washing with twice the amount of the filtrate in demineralized water and drying in a circulating air drying cabinet, the yields given in Table 3 and FIG. 5 were obtained. The specific surface area (BET) in Table 3 and FIG. 5 of the undissolved stabilized lignin was determined after baking at 150 ° C. in a vacuum. The lignin used has 1.9 mmol / g phenolic guaiacyl groups and 0.3 mmol / g p-hydroxyphenyl groups and thus 2.5 mmol / g crosslinkable units.

Table 3: Variants of the experiments under Example 3 with different additive concentrations

As can be seen from Table 3 and FIG. 5 above, the yield and BET of the lignin material produced depend on the amount of crosslinker used.

The examples with numbers M to Q show that the BET initially increases with increasing amount of crosslinker (numbers M to P); a further increase in the amount of crosslinker does not lead to any further increase in BET (number Q).

This clearly results in an optimum amount of crosslinker used. ¹³ C-formaldehyde was used in No. P2 and analyzed by means of solid-state NMR spectroscopy. The spectra of the lignin and stabilized lignin used are shown in FIG. 6 and show at 11 to 35 ppm the preferred formation of methylene groups with the central signal at 24 to 32 ppm with two guaiacyl units as the structure of the stabilized lignin.

Example 4

The raw material for this example is LignoBoost Lignin obtained from a black liquor from a Kraft digestion. The solid was converted into a liquid containing the dissolved lignin by adding water and sodium hydroxide solution. To each 30 g of a liquid containing dissolved lignin with a dry matter content of 15% and a pH value of 9.0, an amount of 40% glyoxal solution defined in Table 4 was added in the first process stage for the reaction with the crosslinker glyoxal. The liquid containing the dissolved lignin and the glyoxal solution were homogenized and treated for the times and temperatures given in Table 4 in the first process stage modified dissolved lignin is produced and then treated in the second process stage and an undissolved stabilized lignin is produced. The undissolved stabilized lignin was recovered by centrifugation. After washing twice with demineralized water and drying in a circulating air drying cabinet, the yields given in Table 4 were obtained. The specific surface area (BET) in Table 4 of the undissolved stabilized lignin was determined after baking at 150 ° C. in a vacuum.

The glyoxal used has 68.9 mmol crosslinkable units / g.

Table 4: Variants of the experiments under Example 4 with different additive concentrations Example 5

The raw material for this example is LignoBoost Lignin obtained from a black liquor from a Kraft digestion. The solid was converted into a liquid containing the dissolved lignin by adding water and sodium hydroxide solution. To each 30 g of a liquid containing dissolved lignin with a dry matter content of 15% and a pH of 9.0, an amount defined in Table 5 was added in the first process stage for the reaction with the crosslinker glyceraldehyde. The liquid containing the dissolved lignin and the glycrinaldehyde were homogenized and treated for the times and temperatures indicated in Table 5 in the first process stage and a modified dissolved lignin was produced and then treated in the second process stage and an undissolved stabilized lignin produced. The undissolved stabilized lignin was recovered by centrifugation. After washing twice with demineralized water and drying in a circulating air drying cabinet, the yields given in Table 5 were obtained. The specific surface area (BET) in Table 5 of the undissolved stabilized lignin was determined after baking at 150 ° C. in a vacuum.

The glyceraldehyde used has 22.2 mmol of crosslinkable units / g.

Table 5: Variants of the experiments under Example 5 with different additive concentrations

Example 6 The raw material for this example is a lignosulfonate as black liquor from the digestion with sulfite. The starting material was converted into a liquid containing the dissolved lignin by adding water and sodium hydroxide solution. To each 30 g of a liquid containing dissolved lignin with a dry matter content of 12.4% and a pH value of 10.4, an amount of a 23.5% formaldehyde solution as defined in Table 6 was added in the first process stage for the reaction with the crosslinker formaldehyde. The liquid containing the dissolved lignin and the formaldehyde solution were homogenized and treated for the times and temperatures given in Table 6 in the first process step and a modified dissolved lignin was produced and then treated in the second process step and an undissolved stabilized lignin was produced. The undissolved stabilized lignin was recovered by centrifugation. After washing twice with demineralized water and drying in a circulating air drying cabinet, the yields given in Table 6 were obtained. The specific surface area (BET) in Table 6 of the undissolved stabilized lignin was determined after baking at 150 ° C. in a vacuum.

The dry matter of the black liquor used has a lignin content of 70%. The lignin content of the dry matter used has 0.6 mmol / g phenolic guaiacyl groups and thus crosslinkable units.

The formaldehyde used has 66.6 mmol crosslinkable units / g dry formaldehyde.

Table 6: Variants of the experiments under Example 6 with different additive concentrations

Claims

Expectations

1 . A method for producing an undissolved stabilized lignin with an STSA surface area of at least 10 m ² / g from lignin-containing raw materials, characterized in that

- in a first process stage, a lignin dissolved in a liquid and a crosslinker are brought to react and a dissolved modified lignin is thus produced, and

- in a second process step the dissolved modified lignin is converted into an undissolved stabilized lignin ..

2. The method according to claim 1, characterized in that

- In a first process stage, a lignin dissolved in a liquid, the lignin having phenolic aromatics, aromatic and aliphatic hydroxyl groups and / or carboxy groups as crosslinkable units; and a crosslinker, wherein the crosslinker has at least one functional group as a crosslinkable unit that can react with the crosslinkable units of the lignin, at a first temperature T1, which is between a first maximum temperature T 1 max and a first minimum temperature T1 min, via a a defined period of time are made to react and so a dissolved modified lignin is generated, and

- In a second process stage, the dissolved modified lignin at a second temperature T2, which is between a second maximum temperature T2max and a second minimum temperature T2min T2, is converted into an undissolved stabilized lignin over a defined period of time.

3. The method according to any one of the preceding claims, characterized in that the addition of the crosslinker takes place in the first process stage and that the amount is a maximum of 4 mol, preferably less than 3 mol, more preferably less than 2.5 mol of crosslinkable units of the Crosslinker per mole of crosslinkable unit of the lignin used.

4. The method according to any one of the preceding claims, characterized in that the metering of the crosslinking agent is carried out such that the amount is at least 0.5 mol, preferably at least 0.75 mol, more preferably at least 1 mol, particularly preferably at least 1.1 mol in particular at least 1.15 mol of crosslinkable units of the crosslinker per mole of crosslinkable units of the lignin used.

5. A process for the production of a stabilized lignin from lignin-containing raw materials, wherein

- In a first process stage, a lignin dissolved in a liquid, the lignin having phenolic aromatics, aromatic and aliphatic hydroxyl groups and / or carboxy groups as crosslinkable units; and a crosslinker, wherein the crosslinker has at least one functional group as a crosslinkable unit which can react with the crosslinkable units of the lignin and the amount of crosslinking compound is selected such that the crosslinkable units of the crosslinker between 0.5 and 4 mol / mol crosslinkable units of the lignin are made to react and so a dissolved modified lignin is produced, and

6. The method according to any one of the preceding claims, characterized in that the amount of crosslinker is a maximum of 35 g / 100 g lignin, preferably a maximum of 30 g / 100 g lignin, particularly preferably a maximum of 25 g / 100 g lignin, in particular a maximum of 20 g / 100 g lignin.

7. The method according to any one of the preceding claims, characterized in that aldehydes or bifunctional compounds are added as crosslinking agents.

8. The method according to any one of the preceding claims, characterized in that the temperature of the first process stage is advantageously more than 50 ° C, preferably more than 60 ° C, particularly preferably more than 70 ° C and less than 180 ° C, preferably less than 150 ° C , more preferably less than 130 ° C, particularly preferably less than 100 ° C.

9. The method according to any one of the preceding claims, characterized in that the average residence time in the first process stage is at least 5 minutes, more preferably at least 10 minutes, more preferably at least 15 minutes, particularly preferably at least 30 minutes, in particular at least 45 minutes, however less than 300 minutes.

10. The method according to any one of the preceding claims, characterized in that the temperature of the second process stage is advantageously less than 270 ° C, preferably less than 260 ° C, more preferably less than 250 ° C, particularly preferably less than 240 ° C , especially at less than 235 ° C.

1 1. Method according to one of the preceding claims, characterized in that the average residence time in the second process stage is at least 10 minutes, more preferably at least 30 minutes, more preferably at least 45 minutes, but less than 600 minutes, preferably less than 480 minutes, particularly preferably at less than 450 minutes.

12. The method according to any one of the preceding claims, characterized in that the pH value of the liquid containing the dissolved lignin before the first process stage is at least 7.5 and above the pH value of the liquid containing the modified dissolved lignin after the first process stage .

13. The method according to any one of the preceding claims, characterized in that the pH value of the liquid containing the modified, dissolved lignin before the second process stage is at least 7 and above the pH value of the liquid containing the undissolved stabilized lignin after the second process stage.

14. The method according to any one of the preceding claims, characterized in that

- in a first process stage o a carbohydrate-based crosslinker, preferably aldehydes, preferably glyceraldehydes or glycolaldehyde obtained from carbohydrates dissolved or dispersed in the liquid containing the dissolved lignin, o caused the lignin dissolved in the liquid and the carbohydrate-based crosslinker to react and thus generated a dissolved modified lignin, and

- In a second process stage, the dissolved modified lignin is converted into an undissolved stabilized lignin.

15. The method according to any one of the preceding claims, characterized in that

- in a first process stage o a lignin-based crosslinker, preferably aldehydes, preferably methanediol or glycolaldehyde, obtained from carbohydrates dissolved or dispersed in the liquid containing the dissolved lignin, o the remaining lignin dissolved in the liquid and the lignin-based crosslinker for Brought reaction and so a dissolved modified lignin is generated, and

16. Undissolved stabilized lignin, in particular obtainable in a method according to one of the preceding claims, characterized by an STSA surface area of at least 10 m ² / g, more preferably at least 20 m ² / g.

17. Undissolved stabilized lignin according to claim 16, characterized by a pore volume of <0.1 cm ³ / g, more preferably <0.01 cm ³ / g, particularly preferably <0.005 cm ³ / g.

18. Undissolved stabilized lignin according to one of claims 16-17, characterized by a solubility in alkaline liquids of less than 30%, preferably less than 25%, particularly preferably less than 20%.

19. Undissolved stabilized lignin according to one of claims 16-18, characterized by a glass transition temperature of more than 160 ° C, more preferably more than 180 ° C, particularly preferably more than 200 ° C, in particular more than 250 ° C.

20. Undissolved stabilized lignin according to one of claims 16-19, characterized by an STSA of at least 10 m ² / g, more preferably at least 20 m ² / g. The STSA is preferably less than 200 m ² / g

A signal in the solid state ¹³ C-NMR at 0 to 50 ppm, preferably at 10 to 40 ppm, particularly preferably at 25 to 35 ppm, with an intensity of 1-80%, preferably 5, compared to the signal of the methoxy groups at 54 to 58 ppm -60%, particularly preferably 5-50% and a ¹³ C-NMR signal at 125 to 135 ppm, preferably at 127 to 133 ppm, which is increased compared to the lignin used

a carbon content based on the ash-free dry substance between 60% by mass and 80% by mass, preferably between 65% by mass and 75% by mass.