WO2015197048A1

WO2015197048A1 - Method for deodorizing lignin

Info

Publication number: WO2015197048A1
Application number: PCT/DE2015/100137
Authority: WO
Inventors: Carsten Zetzl; Christian Kirsch; Lilia Adriana ZENKER; Wienke Reynolds; Irina Smirnova
Original assignee: Technische Universität Hamburg-Harburg; Tutech Innovation Gmbh
Priority date: 2014-06-24
Filing date: 2015-03-31
Publication date: 2015-12-30
Also published as: DE112015002989A5; DE102014108841B3

Abstract

The invention relates to a method for deodorizing lignin. The aim of the invention is to make lignin-containing biological raw materials available for more efficient and larger-scale utilization. Said aim is achieved by a method for deodorizing lignin, comprising the step of extracting a lignin-containing substrate using a supercritical fluid or supercritical fluid mixture.

Description

PROCESS FOR THE DESODORATION OF LIGNIN

The invention relates to a process for the deodorization of lignin. Biomass is becoming increasingly important as a raw material, for example for the

Fuel production or as a source of basic and fine chemicals for the chemical industry. A major role is played by the extensive exploitation of lignocellulose with its main components cellulose, hemicellulose and lignin. Lignin has basically consumer potential application as starting material for phenol production in the basic industry, as an additive, injection molding substrate, fuel, source material for adsorbers and insulating materials. In conventional processes (e.g., so-called soda or pulp processes), lignin is usually by-produced by:

Lignocellulose with alkalis, acids or organic solvents, less often with steam or aqueous solutions, is digested. However, this lignin contains many volatile organic compounds (VOC), which severely limit its applicability in the consumer-related area. Due to these limitations, lignin is currently used mainly as a fuel and only in rare cases as a raw material for the basic industries (glues, vanillin). However, the value added when used as a fuel is economically unsatisfactory, and the isolation of fine chemicals is so far complex and requires the use of various environmentally harmful reaction aids, so that a sustainable recovery without waste materials is not possible. Due to the previously largely limited to the thermal energy recovery utilization of the lignin, which is rich in content, there is thus a considerable potential for untapped potential. Thus, the use of lignin-based moldings, e.g. for dashboards in interiors of motor vehicles, due to the unwanted odor further (bio-) chemical intermediate steps. A similar problem exists in the use of lignin as an adhesive aid, since the original odor note is distracting. Methods for deodorising lignin are known in principle. Kalliola et al. 2012

(Kalliola, A. et al., 2012, Reducing the content of VOCs of softwood Kraft lignin for material applications, BioResources 7 (3), 2871-2882), for example, describe the use of Laccases for the reduction of VOCs in Kraft lignins, ie lignins, which are produced by digestion via the so-called sulphate process. Also, King et al. 2010 (König, S. et al., 2010), Characterization of volatile organic compounds (VOC) in different lignin and their reduction by enzymatic modification for the production of fiber-reinforced biopolymers, Journal of

Biotechnology 150, 380-381. DOI: 10.1016 / j.jbiotec.2010.09.471) as well as the ERA-IB

Research group around Wilhelm. C. et al. 2014 (Project EU3 10.013, Warsaw presentation Feb. 2014: Development of a process for the utilization of the carbohydrates and the lignin content from lignocellulosic materials in annual plants for the production of valuable products) describe the enzymatic processing by means of laccases. An enzymatic

Treatment approach is also described in DE 102006057566 AI.

However, the previously known approaches lead to a significant modification and possibly also to the destruction of the lignin structure. In addition, the methods are relatively complex and must be adapted to the particular lignin composition. In addition, the odor reduction achieved is often not yet satisfactory.

The object of the present invention is to supply lignin-containing bio-raw materials for a more efficient and wider use. The object is achieved by a process for the deodorization of lignin, comprising the step of extracting a lignin-containing substrate with a supercritical fluid or a supercritical fluid mixture. In the process, the lignocellulosic substrate is contacted with a supercritical fluid or fluid mixture under conditions, e.g. in terms of pressure, temperature and extraction time, which are suitable for effecting a reduction of the volatile organic compound (VOC) content in the lignin-containing substrate.

A lignin obtained by the process according to the invention has, in comparison to the starting substrate, i. the lignin-containing substrate before extraction with the supercritical fluid or the supercritical fluid mixture, a markedly reduced proportion of volatile organic compounds (VOC) in the lignin backbone, and is therefore in comparison to

Starting substrate odor-reduced or even substantially odorless. The

inventive method allows for the first time a sustainable and gentle Production of a largely natural lignin, that is, as far as possible unchanged in its original molecular structure, at least odor-reduced or odor-free lignin, without organic solvents, mineral acids and alkalis. Thus, it is possible, for example, to develop a lignin-based filler for the adhesive material production or odorless lignin-based moldings for example the automotive industry.

The term "lignin-containing substrate" is understood here to mean a material or a material mixture which contains lignin, for example, lignin-containing substrates are wood, straw, bagasse, bran, grass, etc. The lignin-containing substrate can also be a already pretreated substrate act, for example, waste from the at

Papermaking often used sulfate or Kraftverfahren, or waste from organic-aqueous solvents treated ligninhaltige substrates (Organosolv method). In connection with such waste is also spoken of "Kraft lignin", "Organosolv" lignin or hydrolysis lignin. The term "lignocellulosic substrate" also includes lignocellulose-containing biomass, a material in which lignin is incorporated into a framework formed of hemicelluloses and, above all, cellulose.

The term "lignin" refers to a complex polymer of aromatic alcohols as monomers, referred to as monolignols, which are substantially linked to each other via ether groups, for example, phenylpropanoids such as p-cumaryl alcohol, coniferyl alcohol and sinapyl alcohol, which may be, for example, methoxylated to varying degrees Lignin is a component of the secondary cell wall of plants and some algae, where it forms cross-linked macromolecules with molecular weights of more than 5000 U. Various species of wood or plants have lignins

different percentages of monolignols. For example, lignin from softwood contains predominantly coniferyl units which have a guaiacyl residue (3-methoxy-4-hydroxyphenyl residue), while the lignin from hardwood contains varying proportions of guaiacyl residues and sinapyle units which contain a syringyl residue (3,5-methoxy-4-hydroxyphenyl residue). having. Grassy lignin contains all three units.

The term "deodorization" is to be understood as meaning a reduction in the proportion of odor-forming compounds. Odor-forming compounds are generally volatile Organic compounds (VOC = volatile organic compounds), which can be perceived olfactorily or detected by measurements in the gas phase.

In particular, VOCs here are understood as meaning volatile organic compounds which already have a high vapor pressure at ambient temperature and can therefore preferably diffuse out of the substrate into the atmosphere. In the following, VOCs are understood in particular to mean organic components which have a boiling point of 50-260.degree. Examples of VOCs are guaiacol and reduced organic

Sulfur compounds such as dimethyl disulfide and dimethyl trisulfide. The term

Accordingly, "deodorization of lignin" refers to the reduction of the proportion of lignin-derived odor-causing volatile organic compounds (VOC) or residues thereof For clarification, it should be noted that the term "deodorization of a lignin-containing substrate" refers to the deodorization of the lignin portion of the substrate refers. The term "reducing the level of odoriferous compounds" preferably refers to a reduction in the total mass of odoriferous compounds that can be released from the lignocellulosic substrate compared to the starting substrate.

The term "supercritical fluid" or "supercritical fluid", abbreviated also SCF, refers to a fluid substance in the near or supercritical state, ie at a temperature and a pressure near or above the critical point (T _c and P _c ) the substance. In this state, liquid phase and gas phase are no longer distinguishable. The term preferably refers to single-fluid, ie fluids, the except

inevitable impurities consist essentially of only one substance, eg C0 ₂ exist. A "supercritical fluid mixture" or "supercritical fluid mixture" is understood to mean multi-fluid fluids, ie mixtures of two or more substances, for example C0 ₂ and propane, or C0 ₂ and small amounts of ethanol or water. Under

"Supercritical C0 ₂ " or "supercritical C0 ₂ ", abbreviated "scC0 ₂ ", is understood to mean supercritical carbon dioxide, the critical point for carbon dioxide is one

Temperature of 304, 13 K (30.98 ° C) and a pressure of 7.375 MPa (73.75 bar). At temperatures and pressures above this point, supercritical results

Carbon dioxide. A "hot water extraction" is understood to mean a thermal treatment by means of water at a temperature of> 100 ° C. and a pressure above the vapor pressure of the water at the respective temperature, examples being temperatures of 100-250 ° C. at pressures of 1-50 bar, for example a temperature of 200 ° C. at a pressure of 30 bar. If the terms "hot water hydrolysis" or "hot water pretreatment" are also used here, they are used synonymously with the above term "hot water extraction".

In a preferred embodiment, the supercritical fluid is a single-fluid, and more preferably carbon dioxide (C0 ₂ ), wherein the SCF extraction in this

Embodiment preferably at a temperature of 20-90 ° C, preferably 30-80 ° C and more preferably 40-70 ° C, and a pressure of 80-800 bar, preferably 100-700 bar, 150-600 bar or 200-500 bar and more preferably 300-450 bar is performed. Alternatively, however, it is also possible to use a fluid mixture in which C0 ₂ preferably forms the main component, ie a proportion of at least 60% by volume, preferably at least 70, 80, 85, 90 or 95% by volume. Examples are fluid mixtures of C0 ₂ and ethanol or water, or from C0 ₂ and propane, with the former being preferred, for example C0 ₂ ethanol-, C0 ₂ - water or C0 ₂ propane mixtures in the ratio 80:20 or higher. The addition of ethanol, water or propane can increase the polarity of the C0 ₂ , which can reduce the required process pressure and, consequently, the process and investment costs.

The method according to the invention is preferably a fixed-bed method, wherein the fixed bed is formed by the lignin-containing substrate or comprises the lignin-containing substrate. In the fixed-bed process, the lignin-containing substrate is preferably opposite to

Direction of gravity flows through the supercritical fluid.

The extraction of the lignin-containing substrate with a supercritical fluid may be a suitable pretreatment, preferably a hot water extraction and / or a

enzymatic extraction using cellulase (s) (see Kirsch et al.

Enzymatic hydrolysis of lignocellulose in a fixed bed reactor, Chemie Ingenieur Technik 2011, 83 (6), 867-873). Preference is given to the lignin-containing substrate prior to extraction with the supercritical fluid at least one hot water extraction, which here also optionally as Hot water hydrolysis or thermal hydrolysis is subjected. The inventive combination of extraction with supercritical fluid with a

Pre-switched hot water extraction offers the possibility of producing a largely natural lignin using harmless aids while efficiently removing odorous substances. Lignin subjected to hot water extraction is also referred to herein as "Aquasolv solid lignin" or "AS lignin".

The hot water extraction is preferably carried out with pure water in a temperature range of 100-250 ° C, for example 200 ° C, and at pressures of 1-50 bar, for example 30 bar. The hot water extraction can be carried out in one or more stages, for example with gradually increasing temperature and increasing pressure.

Preferably, the ratio of water to lignin-containing substrate is 5-10: 1. In the case of the preferred fixed bed process, the hot water under pressure preferably flows through the lignin containing substrate in the direction opposite to the direction of gravity.

In a particularly preferred embodiment of the method according to the invention, the lignin-containing substrate is first a) a hot water extraction, then b) an enzymatic hydrolysis by means of cellulase (s), and then c) an extraction with a supercritical fluid or supercritical fluid mixture, preferably with supercritical carbon dioxide , subjected. The process steps a) to c) preferably follow

directly on each other. However, it is also possible that between the above

Process steps intermediate steps take place, for example washing steps, grinding steps or the like. For example, between step b) and step c) optionally a step of comminuting the lignin-containing substrate formed in step b) may be provided.

Step b, that is, the enzymatic hydrolysis using a cellulase or a mixture of cellulases, is preferably carried out at a temperature of 30-70 ° C, preferably 45-60 ° C, more preferably 45-55 ° C, particularly preferably 50 ° C , and a pH of 4.5-5.5, preferably 4.8, performed. Suitable cellulases are known to the person skilled in the art (see, for example, Kirsch et al., 2011, Enzymatic hydrolysis of lignocellulose in a fixed bed reactor, Chemie Ingenieur Technik 2011, 83 (6), 867-873). The cellulases can be used, for example, in a concentration of 10-15 FPU / g of cellulose.

For example, in the above embodiment of the method according to the invention - step a at a temperature of 200 ° C and a pressure of 30 bar,

Step b at a temperature of 50 ° C and a pH of 4.8, and

- Step c with supercritical carbon dioxide at a temperature of 40-70 ° C and a pressure of 300-450 bar are performed. In a further particularly preferred embodiment of the method according to the invention, a sequential flow through the lignin-containing substrate takes place in step a

Hot water increasing temperature and increasing pressure, i. the hot water extraction takes place in several stages, whereby the temperature and pressure are increased from stage to stage. In this case, the hot-water extraction in step a preferably comprises the successive substeps al to a3. Step al performed at a temperature of 100-120 ° C and a pressure of 1-5 bar. The aim here is the extraction or extraction of proteins from the raw biomass. Step a2 carried out at a temperature of 150-190 ° C and a pressure of 5-20 bar. The aim of this second step is the removal or extraction of

Hemicellulose from the residue of step al. Step a3 carried out at a temperature of 190-220 ° C and a pressure of 20-50 bar. The goal of this third step is the

Pretreatment of remaining in the residue of a2 cellulose for a subsequent enzymatic attack. This embodiment of the method is particularly gentle, i. the natural lignin structure is largely retained, while at the same time a very substantial odor reduction takes place.

The substeps al to a3 are preferably followed by a step b at a temperature of 30-70.degree. C., preferably 45-60.degree. C., more preferably 45-55.degree. C., particularly preferably 50.degree. C. and a pH of 4.5. 5.5, preferably 4.8, and a step c with supercritical carbon dioxide at a temperature of 20-90 ° C, preferably 30-80 ° C, more preferably 40-70 ° C and a pressure of 80-800 bar, preferably 100-700 bar or 150-600 bar, more preferably 200-500 bar and particularly preferably 300-450 bar. The temperature and pressure ranges can be selected independently. In a particularly preferred embodiment of the method according to the invention, the lignin-containing substrate is comminuted with the supercritical fluid before extraction,

preferably to a mean particle diameter of <100 μπι. This makes the lignocellulosic substrate more accessible to the supercritical fluid used for extraction.

The inventive method preferably leads to a reduction of the

mass fraction of volatile organic compounds (VOC) of the lignin-containing substrate by at least 50%, preferably at least 60%, 70%, 80% or at least 90%, more preferably at least 95%, 96%, 97%, 98% or 99%. Methods for determining the content of volatile organic compounds (VOC) in a lignin-containing substrate are the

Specialist familiar. The person skilled in the art can determine the desired degree of deodorization by means of the process parameters pressure, temperature, residence time (or hydrodynamics) in the fixed bed and given fixed-bed geometry (ratio length / diameter, porosity, particle size and shape), as well as by suitable choice of the supercritical fluid or the supercritical fluid

Influence and adjust fluid mixture.

In a further aspect, the present invention also relates to the use of a supercritical fluid, preferably supercritical carbon dioxide, or a supercritical fluid mixture for deodorizing a lignocellulosic substrate. Preferably, supercritical carbon dioxide (scC0 ₂ ) is used as the supercritical fluid. Particularly preferred is supercritical carbon dioxide at a temperature of 20-90 ° C, preferably 30-80 ° C, more preferably 40-70 ° C, and a pressure of 80-800 bar, preferably 100-700 bar or 150-600 bar, furthermore preferably used 200-500 bar and particularly preferably 300-450 bar. Pressure and temperature can be selected independently.

In a further aspect, the present invention also relates to an odor-reduced or odor-free lignin obtainable by a method according to the invention. The invention will in the following be purely illustrative with reference to a

Embodiment and the attached figures explained in more detail. Figure 1 Schematic flow diagram of an embodiment of the invention

Process.

Figure 2 Schematic representation of a device suitable for carrying out the method according to the invention.

Figure 3 A) FID-GC-MS diagram of a lignocellulosic material after hot water extraction (step a) and enzymatic hydrolysis (step b), ("AS-lignin") The VOC spectrum was measured after hexane extraction of the lignin-containing material in a Soxhlet apparatus Figure 3B) FID-GC-MS diagram of a supercritical fluid extract of the lignin-containing substrate from step (c).

FIG. 1 shows schematically a flow chart for an embodiment of the method according to the invention. A lignin-containing starting material is first subjected to a hot water extraction (a). The hot water extraction, for example, can be increased gradually

Temperature of 110-210 ° C and a corresponding stepwise increased pressure of 1.5-30 bar are performed. The extracts recovered from the fixed bed, which may optionally be removed from the system and otherwise utilized, contain essentially proteins, C5 sugars from hemicellulose and soluble lignin. The lignin-containing residue a remaining after the hot water extraction is subsequently subjected to enzymatic hydrolysis using suitable cellulases (b). For this purpose, the lignin-containing residue a is first cooled to about 50 ° C. The hydrolysis can then be carried out, for example, in the same fixed bed at a pH of 4.8 and a cellulase loading of 10-15 FPU / g of cellulose. The hydrolyzate contains mainly C6-sugars, which in turn can be fed to a separate recycling. The lignin-containing residue b now obtained is optionally washed, dried and / or comminuted, preferably to particles having an average diameter of on average less than 100 μm, whereby a lignin-containing residue would be obtained bl. The crushing can be done for example by means of a ball mill. The lignin-containing residue b, also called AS-lignin, or optionally the washed, dried and / or comminuted lignin-containing residue bl are then subjected to extraction with supercritical C0 ₂ at temperatures of for example 40-70 ° C and a pressure of, for example 300-450 bar subjected. The extract can in turn be precipitated by simply relaxing the C0 ₂ and optionally utilized, for example as a flavoring agent. The VOC spectrum of the C0 ₂ extract is Der in this last step after the supercritical

Fluid containing hgninhaltige residue is considerably less odor than that

Starting material, or even odorless.

Figure 2 shows schematically an embodiment of a device which is suitable for carrying out the method according to the invention. The device comprises an autoclave 3, in which ligninhaltiges material can be introduced. By means of a high-pressure pump 5 and valves 9, 10 carbon dioxide from a corresponding template 1, water from a template 2 and an enzyme-containing solution from a template 4 in the autoclave 3 are passed. A heater 6 is used to heat the autoclave, a cross-flow filter 8 for separating the enzymes from the hydrolyzate. Extracts or hydrolysates can be collected in a container 7.

Leader of the game

1000 g of ground, pelleted wheat straw were placed in a 3 L autoclave and subjected to hot water hydrolysis with pure water at 200 ° C and 30 bar. The

What water / substrate ratio was between 5 and 10. The hydrolyzate (C5 sugar from

Hemicellulose and soluble lignin) was purified as a side stream and recycled. 50% of the solid was dissolved in the reactor. After completion of the hot water extraction, the fixed bed was cooled. The biomass was then in a batch reactor with a

Universal buffer solution at pH 4.8 (eg carbon dioxide) flows through. Subsequently, cellulases (Cellic CTec2, Novozymes A / S, Denmark) with a loading of 10-15 FPU / g cellulose were used. By means of FID-GC-MS after hexane extraction, a VOC spectrum was determined from the as-lignin obtained in this way (see Fig. 3A). The enzymatic hydrolyzate was rich in C6 sugars through the breakdown of cellulose and can subsequently be degraded to bioethanol or other C6 degradation products and commodity chemicals (HMF, levulinic acid). The hgn-containing solids residue after enzymatic hydrolysis was separated from the resulting C6 sugar solution by means of the fixed-bed flow-through method, washed and dried. This residue contained up to 80% by weight of lignin as well various carbohydrate and enzyme residues or inorganic constituents. The lignin was ground to a particle size of <100 μm, which significantly increased the surface available for mass transfer. The lignin-containing residue was flowed through at a pressure of 450 bar and a temperature of 45 ° C with supercritical C0 ₂ .

Here, free VOC components were leached out of the lignin, the lignin lost its severe wood odor. The extract precipitated by C0 ₂ relaxation, and was available for other applications, for example, as a natural flavoring agent in cases where smoking smell is desired. The VOC spectrum of this extract is shown in Fig. 3B. It essentially corresponds to that after hot water hydrolysis and thus shows that at least a major part of the VOC has been removed from the lignin-containing starting material.

Claims

PATENT CLAIMS

A process for deodorising lignin, comprising the step of extracting a lignocellulosic substrate with a supercritical fluid or supercritical or

near-critical fluid mixture.

2. The method of claim 1, wherein the supercritical fluid is carbon dioxide.

3. A method according to any one of claims 1 or 2, wherein the method is a fixed bed process, and wherein the fixed bed is formed by the lignin-containing substrate or comprises the lignin-containing substrate.

4. The method according to any one of the preceding claims, wherein the extraction of the

Ligninhaltigen substrate with a supercritical fluid, a hot water extraction and / or an enzymatic extraction by means of cellulase (s) is connected upstream.

5. The method of claim 3, wherein the lignocellulosic substrate

a. a hot water extraction, then

b. an enzymatic hydrolysis by means of cellulase (s), and subsequently

c. extraction with a supercritical fluid, preferably supercritical carbon dioxide.

6. The method of claim 5, wherein

Step a is carried out at a temperature of 100-250 ° C and a pressure of 1-50 bar,

- Step b at a temperature of 30-70 ° C, preferably 45-60 ° C, more preferably 45-55 ° C, more preferably 50 ° C, and a pH of 4.5-5.5, preferably 4 , 8, and

- Step c with supercritical carbon dioxide at a temperature of 20-90 ° C, preferably 30-80 ° C, more preferably 40-70 ° C, and a pressure of 80-800 bar, preferably 100-700 bar or 150-600 bar , more preferably 200-500 bar and particularly preferably 300-450 bar, is performed.

7. The method according to claim 5 or 6, wherein step a comprises successive substeps al to a3, in which the temperature and pressure of the hot water are gradually increased, and wherein

Step al is carried out at a temperature of 100-150 ° C and a pressure of 1-5 bar,

- Step a2 is carried out at a temperature of 150-190 ° C and a pressure of 5-20 bar, and

- Step a3 is carried out at a temperature of 190-220 ° C and a pressure of 20-50 bar.

8. The method according to any one of claims 5 to 7, wherein the ratio of water to

lignin-containing substrate is 5-10: 1.

9. The method according to any one of the preceding Anprüche, wherein the lignin-containing substrate is comminuted prior to extraction with the supercritical fluid, preferably to an average particle diameter of <100 μιη.

10. The method according to any one of the preceding claims, wherein the proportion of volatile

organic substances VOC of the lignin-containing substrate by at least 50%, preferably at least 60%, 70%, 80% or at least 90%, more preferably at least 95%, 96%, 97%, 98% or 99% is reduced.

11. Use of a supercritical fluid or supercritical fluid mixture, preferably supercritical carbon dioxide, for deodorizing a lignocellulosic substrate.

12. Odor-reduced or odor-free lignin obtainable by a process according to any one of claims 1 to 10.