KR20190096010A - Catalsy for depolymerization of lignin and method for depolymerization of lignin using the same - Google Patents

Abstract

Provided are a lignin decomposition catalyst and a lignin decomposition method using the same. The lignin decomposition catalyst can comprise a metal and zeolite supporting the metal. The lignin decomposition method can comprise a step of performing a lignin decomposition reaction using the lignin decomposition catalyst. The present invention can obtain a mono aromatic compound with a high yield.

Description

Lignin decomposition catalyst and lignin decomposition method using the same {CATALSY FOR DEPOLYMERIZATION OF LIGNIN AND METHOD FOR DEPOLYMERIZATION OF LIGNIN USING THE SAME}

The present invention relates to a lignin decomposition catalyst and a lignin decomposition method using the same.

In the chemical industry based on fossil fuels, new and renewable energy researches are being actively conducted to replace them due to environmental pollution and depletion of oil and coal resources. Lignocellulosic is a representative compound of biomass, a promising renewable energy source, and is a wood cellulose containing lignin.

Lignin compounds are the most abundant carbon compounds on the planet excluding cellulose. Currently, ethanol and fuel production technology through cellulose is commercialized, but lignin is difficult to decompose due to a very stable and stable bond, and thus lignin utilization technology has not reached the commercialization stage.

In order to solve the above problems, the present invention provides a lignin decomposition catalyst that can decompose lignin.

The present invention provides a lignin decomposition method using the catalyst.

Other objects of the present invention will become apparent from the following detailed description and the accompanying drawings.

The lignin decomposition catalyst according to the embodiments of the present invention may include a metal and a zeolite supporting the metal.

The metal may comprise copper.

The copper content may be 5 to 15 wt% based on the total weight of the lignin decomposition catalyst.

The zeolite may include silicon and aluminum, and the molar ratio (Si / Al ₂ ) of the silicon to the aluminum may be 20 to 40.

The zeolite may have an MFI structure.

Lignin decomposition method according to embodiments of the present invention may include the step of performing a reaction to decompose lignin using the lignin decomposition catalyst.

The lignin can be broken down to form a single aromatic compound.

The reaction can be carried out in a supercritical fluid.

The supercritical fluid may comprise supercritical ethanol.

The reaction may be carried out at a temperature of 400 to 500 ℃.

By using the lignin decomposition catalyst according to the embodiments of the present invention, it is possible to selectively decompose the lignin compound which is difficult to decompose and obtain a high yield of a single aromatic compound.

1 shows a distribution of a single aromatic compound according to an embodiment of the present invention.
Figure 2 shows the side chain region HSQC NMR spectrum of the protobind lignin according to an embodiment of the present invention.
Figure 3 shows the aromatic region HSQC NMR spectrum of the protobind lignin according to an embodiment of the present invention.
Figure 4 shows the HSQC NMR spectrum of the side branch region of THF soluble lignin after reaction with 10% by weight Cu / ZSM-5 (30) according to an embodiment of the present invention.
5 shows an XRD pattern of 10 wt% Cu / ZSM-5 (Non) catalyst according to one embodiment of the present invention.
6 shows SEM images of reduced 10 wt% Cu / ZSM-5 at various ratios according to one embodiment of the present invention.
Figure 7 shows the NH ₃ -TPD spectrum of 10 wt% Cu / ZSM-5 (Non) catalyst according to one embodiment of the present invention.
8 shows the yield of a single aromatic compound according to the acid density of various Si / Al _{2 ratio} catalysts according to one embodiment of the present invention.

Hereinafter, the present invention will be described in detail through examples. The objects, features and advantages of the present invention will be readily understood through the following examples. The invention is not limited to the embodiments described herein, but may be embodied in other forms. The embodiments introduced herein are provided so that the disclosure may be made thorough and complete, and the spirit of the present invention may be sufficiently delivered to those skilled in the art. Therefore, the present invention should not be limited by the following examples.

Lignin decomposition catalyst according to embodiments of the present invention may include a metal and zeolite.

The zeolite may include silicon and aluminum, and may have an MFI structure. For example, ZSM-5 zeolites can be used. The ZSM-5 zeolites have unique shape selectivity, ideal pore size and acidity and are therefore suitable for aromatization and decomposition reactions.

In addition, the zeolite may have various molar ratios (Si / Al ₂ ) of the silicon to the aluminum. The lignin decomposition efficiency may vary depending on the Si / Al ₂ ratio. The Si / Al ₂ ratio may be 20 to 40, more precisely 30, and at this time, the yield of a single aromatic compound formed by decomposition of the lignin may be high.

The zeolite may be supported by a metal, and the metal may include transition metals such as cobalt, nickel and copper. The copper may be supported on the zeolite to promote depolymerization of the lignin compound. The copper content relative to the total weight of the lignin decomposition catalyst may be supported on the zeolite at 5 to 15% by weight, more precisely 10% by weight. That is, a 10 wt% Cu / ZSM-5 catalyst having a Si / Al ₂ ratio of 30 may exhibit a high yield of at least 90%.

Lignin decomposition method according to embodiments of the present invention may include the step of performing a reaction to decompose lignin using the lignin decomposition catalyst. That is, depolymerization of the lignin compound composed of three main phenylpropane units (guaiayl alcohol, siringyl alcohol and p-comaryl alcohol) connected by carbon-carbon (CC) and carbon-oxygen (CO) bonds is carried out. Can be done. The lignin can be decomposed to form a single aromatic compound having a high added value.

The reaction can be carried out in a supercritical fluid. The supercritical fluid can effectively decompose lignin with the lignin decomposition catalyst using active hydrogen generated in the supercritical fluid itself without the addition of additional hydrogen gas.

The supercritical fluid may comprise supercritical ethanol. Ethanol is a solvent having good solubility not only in supercritical conditions but also in atmospheric conditions because of its low dielectric constant. For this reason, the product dissolved in ethanol can be maintained after separation without separation or condensation at atmospheric conditions. In addition, the bio-oil produced for this reason can form a single liquid phase and can be more easily recovered from the ethanol.

Lignin generally has many hydroxyl groups, which are highly reactive and are likely to repolymerize during the reaction. However, the supercritical ethanol that produces in-situ hydrogen can act as a nucleophile to alkylate the hydroxyl group and prevent repolymerization. As a result, the supercritical ethanol may exhibit higher yields than other supercritical fluids such as supercritical carbon dioxide or supercritical water.

That is, the depolymerization reaction may be carried out at 400 ℃ to 500 ℃ by putting 10 wt% Cu / ZSM-5 lignin decomposition catalyst, the ethanol and lignin in a stainless steel high pressure autoclave, more precisely performed at 430 ℃ to 450 ℃ Can be. The ethanol is heated above the critical point (about 214 ° C., 60.6 atm), and the ethanol may be in a supercritical state to generate active hydrogen therein. The lignin may be decomposed due to the active hydrogen, and in this process, copper supported on the ZSM-5 zeolite may serve to mediate the active hydrogen to access the lignin compound more easily. This method allows the lignin compound to be selectively degraded and to form a single aromatic compound in high yield.

EXAMPLE

[Materials and Chemicals]

Protobind 1000 alkaline lignin (PL) was supplied by Eindhoven University. The lignin was produced in straw (sulfur-free lignin containing less than 4% by weight carbohydrates and less than 2% by weight ash) using a soda pulping process. Cu (NO ₃ ) ₂ .3H ₂ O, Ni (NO ₃ ) ₂ .6H ₂ O, Co (NO ₃ ) ₂ .6H ₂ O was purchased from Alfa Aesar for catalyst synthesis. For catalyst supports, commercial NH ₄ form ZSM-5 zeolites were purchased from Alpha Eisa (Si / Al ₂ = 30, 50, 80 and 200). Ethanol was chosen as the reaction medium for depolymerization of lignin under supercritical conditions (Sigma-Aldrich, 200 proof, ACS reagent, ≧ 99.5%). Tetra-hydrofuran (reagent plus ≥99.0%, stabilized with butylated hydroxytoluene) and deuterated dimethyl sulfoxide-d ₆ (containing TMS) were added after the liquid product, respectively. Purchased from Sigma-Aldrich for processing and NMR analysis.

[Catalytic preparation]

Commercial NH ₄ ZSM-5 was used after calcining at 550 ° C. for 3 hours to induce H ZSM-5 morphology. All catalysts were synthesized by applying wet impregnation. The metal precursor was dissolved in deionized water and the solution was placed in a support and stirred for 30 minutes at room temperature. The metal was impregnated into each support using a rotary evaporator and the catalyst was dried in an oven overnight. All prepared catalysts were calcined at 500 ° C. (cobalt catalyst) and 460 ° C. (copper and nickel catalysts) in muffle for 2 hours each. Prior to the reaction, the calcined catalyst was reduced under the same conditions of 15% hydrogen / nitrogen flow. The reduced catalyst is represented by X wt% M / ZSM-5 (ratio). (X = loading of metal, M = transition metal, ZSM-5 ratio = 30, 50, 80 and 200)

[Characteristic analysis]

Inductively coupled plasma-atomic spectroscopy (ICP-AES) was used to confirm the metal content (Si, Al and Cu) of the prepared catalysts (SHIMADZU / ICPE-9000). Samples were analyzed using acid warm needles (aqua regia and perchloric acid, a mixture of concentrated nitric acid and concentrated hydrochloric acid). The physical properties of the catalyst were analyzed using a nitrogen physical adsorption apparatus (Micro-metritics ASAP 2010) at constant temperature (77K). Prior to analysis, all samples were pretreated at 250 ° C. for at least 4 hours in vacuum.

Powder X-ray diffraction (XRD) analysis was performed on a high power X-ray diffractometer (Rigaku Corp.) using Cu Kα as the radiation source at 40 kV and 30 mA. The scan step was fixed at 0.02 degrees in the 10-90 degree range.

Ammonia elevated desorption (TPD) was performed using BEL CAT II, JAPAN. Prior to analysis, 0.03 g of sample was heated at 300 ° C. for 1 hour under helium flow to remove adsorbed impurities. After cooling to 60 ° C., the sample was saturated with 4.96% ammonia / helium. Physically adsorbed ammonia was removed by purifying the helium flow at 100 ° C. After the sample was cooled to 60 ° C. and the TCD signal stabilized, the TCD signal was recorded by increasing the temperature from 60 ° C. to 550 ° C. at a rate of 10 ° C./min under helium flow.

The surface morphology of the reduced catalyst was investigated using field emission scanning electron microscopy (FE-SEM, MERLIN compact, ZEISS). Heteronuclear signal quantum coherence (HSQC) analysis was performed using 850 MHz Cryo NMR (AVNACE III HC, Bruker, German). Protobind lignin raw material and THF soluble lignin were dried overnight in a 105 ° C. oven and dissolved in 900 μL of deuterated dimethyl sulfoxide-d ₆ before HSQC-NMR analysis.

[Experiment setup and procedure]

Catalytic depolymerization of lignin was carried out in a 50 mL stainless steel high pressure autoclave. The reactor was charged with 25 g of ethanol in 0.5 g of protobind lignin. 0.3 g of sieved catalyst (425 μm-600 μm) was placed in a designed 500 mesh stainless steel basket. As an internal standard, 0.0013 g of fluoranthene was also added to the reactor. The reactor was sealed several times with nitrogen to seal off oxygen. Prior to the reaction, 10 bar of nitrogen was pressurized into the reactor at room temperature. The reaction mixture was then heated to 440 ° C. (12 ° C./min) for 5 hours with stirring at 500 rpm. After the reaction, the reactor was rapidly quenched to 130 ° C. or lower using an ice water vessel. The yield (Y) of the monoaromatic compound was calculated by the following equation.

[Product analysis]

GC-MS (Agilent 6890N, DB-5 ms, 30 m × 0.25 mm × 0.25 μm) and GC-FID (Agilent 6890A, DB-5, 60 m × 0.25 mm × 0.25 μm) analysis of the liquid product were performed without dilution. Fluoranthene was used as the internal standard (ISTD). The injector and detector temperatures were 310 ° C and 320 ° C, respectively. The initial oven temperature of GC was 50 ° C. for 5 minutes, increased from 10 ° C./minute to 90 ° C., then 130 ° C. (1 ° C./minute), 220 ° C. (5 ° C./minute) and 325 ° C. (10 ° C.) for 10 minutes. 10 ° C./min). The gas product was analyzed by GC to quantify hydrogen. GC-TCD (Agilent 6890N, Carboxen 1000, 30m × 0.53mm × 0.25μm) was used for the analysis. The initial oven temperature was 35 ° C. for 2 minutes and the oven was heated to 250 ° C. at a rate of 10 ° C./min for 1 minute. The injector temperature was 183 ° C, and the detector temperature was 250 ° C.

[result]

[ZSM-5-Supported Catalysts for Lignin Depolymerization]

The lignin depolymerization reaction was carried out in 440 ° C. supercritical ethanol for 5 hours without catalyst (blank reaction) and through a ZSM-5 supported catalyst. Total yields of mono-aromatic compounds are phenol, toluene, m-xylene, benzyl alcohol, 2-ethylphenol, ethylbenzene, Guiacol, syringol, o-cresol, 4-ethylphenol, benzaldehyde and 1,2,4-trimethoxybenzene (1 It is obtained by summing the yields of 12 monoaromatic compounds containing 2,4-trimethoxybenzene).

Table 1 shows the yield of monoaromatic compounds quantified using GC-FID.

Entry
Catalyst Yield of monoaromatic compounds
(wt.%) One None 5.0 2 10 wt.% Ni / ZSM-5 (200) 12.5 3 10 wt.% Co / ZSM-5 (200) 14.8 4 5 wt.% Cu / ZSM-5 (200) 11.3 5 30 wt.% Cu / ZSM-5 (200) 10.8 6 ZSM-5 (30) 89.4 7 10 wt.% Cu / ZSM-5 (30) 98.2 8 10 wt.% Cu / ZSM-5 (50) 84.9 9 10 wt.% Cu / ZSM-5 (80) 39.5 10 10 wt.% Cu / ZSM-5 (200) 15.3

For the blank reaction of item 1, the yield of a single aromatic compound is 5.0% by weight. On the other hand, the yield of the monoaromatic compound through the ZSM-5 supported catalyst is also shown in Table 1. First, of the various transition metals (nickel, cobalt and copper) supported on the ZSM-5 (200), 10 wt.% Cu / ZSM-5 (200) exhibits the highest yield (15.3 wt.%) Of a single aromatic compound. Since the optimal metal is considered copper, the loading of copper for the ZSM-5 (200), as in items 4 and 5, varies from 5% to 30% by weight. As a result, the maximum yield of a monoaromatic compound is obtained by applying Cu / ZSM-5 (200) carrying 10% by weight of copper. This result indicates that the presence of a catalyst clearly improves the mono aromatic yield.

Finally, the Si / Al ₂ ratio of ZSM-5 was changed from 30 to 200, but the amount of copper supported was fixed at 10% by weight. By varying the Si / Al ₂ ratio of ZSM-5 as in the case of items 7 to 10, the yield of monoaromatic compounds increases dramatically. The highest yield of a monoaromatic compound can be obtained via 10 wt% Cu / ZSM-5 (30) at 98.2 wt% among the catalysts. In addition to the ZSM-5 (30) supported catalyst, 10 wt% Cu / ZSM-5 (50) and 10 wt% Cu / ZSM-5 (80) also yield 84.9 wt% and 39.5 wt% of relatively high monoaromatic compounds, respectively. Shows. Thus, an in-depth analysis with 10 wt% Cu / ZSM-5 was performed as a function of the Si / Al ₂ ratio to explain the results.

1 shows a distribution of a single aromatic compound according to an embodiment of the present invention.

Referring to FIG. 1, as a single aromatic compound selected through a catalyst at 440 ° C. for 5 hours, benzaldehyde, ethylbenzene, m-xylene and toluene were mainly produced through the depolymerization reaction of protobind lignin. The monoaromatic compounds were identified and quantified by GC-MS and GC-FID analysis. By decreasing the Si / Al ₂ ratio, the amount of monoaromatic compound is gradually increased, which can be related to the yield of monoaromatic compound.

Figure 2 shows the side chain region HSQC NMR spectrum of the protobind lignin according to an embodiment of the present invention, Figure 3 shows the aromatic region HSQC NMR spectrum of the protobind lignin according to an embodiment of the present invention. HSQC NMR analysis was performed to observe changes in chemical binding of raw lignin and THF soluble lignin after lignin depolymerization.

Referring to FIG. 2, methoxy (-OCH ₃ ), β-O-4 bond (A), β-β bond (B), and β-5 bond (C) are clearly observed in the protobind lignin in the side chain region. . By the ¹³ C- ¹ H correlation for the α, β and γ positions, the presence of β-O-4 represented by (A) is confirmed. The ¹³ C- ¹ H correlation of the resinin substructure is represented by β-β (B) and the phenylcoumarane substructure is represented by β-5 (C). In addition, ρ-hydroxylcinnamyl alcohol terminal group (I) and β-D-xylopyranoside are observed. The latter observation implies the formation or presence of furan compounds.

Referring to FIG. 3, in the aromatic region, etherified syringyl unit (S), oxidized (Cα = O) siring unit (S ′), guiacyl unit (G), and ferulate ( ferulate (FA) (H) and ρ-hydroxyphenyl units (H) and ρ-coumarate (ρCA) are observed in the raw protobinding lignin.

Figure 4 shows the HSQC NMR spectrum of the side branch region of THF soluble lignin after reaction with 10% by weight Cu / ZSM-5 (30) according to an embodiment of the present invention.

Referring to FIG. 4, the product containing the ethyl group is identified by HSQC NMR as evidenced by the signal for the ethylated product marked with an asterisk (*). This result means that ethylation between the monoaromatic compound and ethanol occurs during the reaction. Indeed, ethylation products such as 2-ethylphenol, o-cresol and ethylbenzene are also detected by GC in the liquid product.

On the other hand, in order to confirm the role of copper, lignin depolymerization was performed under the same conditions using a copper-free catalyst, ZSM-5 (30). As a result, the yield of a single aromatic compound is 89.4% by weight as in item 6 of Table 1, which is lower than the yield of 10% by weight Cu / ZSM-5 (30). Based on the results, it can be assumed that lignin depolymerization occurs mainly through ZSM-5 (30), which has the highest acidity. On the other hand, the addition of copper metal to the ZSM-5 (30) support slightly increases the yield. This means that copper metal plays a role in promoting depolymerization of lignin. The hydrogen atom can be adsorbed onto the surface of the copper metal which breaks the ether bond of lignin.

[Physical Properties of 10 wt.% Cu / ZSM-5 (Non) Catalysts]

Table 2 shows the results of the ICP-AES and N ₂ physical adsorption of ZSM-5 (non) supported catalysts.

Entry Catalyst ICP-MS N ₂ physisorption Cu
(%) Si / Al ₂ S _BET
(m ² / g) S _External
(m ² / g) One 10 wt.% Cu / ZSM-5 (30) 7.54 34 331 98 2 10 wt.% Cu / ZSM-5 (50) 7.44 60 365 135 3 10 wt.% Cu / ZSM-5 (80) 7.45 84 426 141 4 10 wt.% Cu / ZSM-5 (200) 7.26 227 355 237

As shown in Table 2, there is a difference in copper loading between the experimental and theoretical values. However, the experimental value for copper loading between samples is almost the same, from 7.26% to 7.54%. On the other hand, the experimental value of the Si / Al ₂ ratio of ZSM-5 is slightly larger than the theoretical value. All catalysts have an almost similar BET surface area between 331 m ² / g to 365 m ² / g and 10 wt% Cu / ZSM-5 (80) is expected to have a maximum BET surface area of 426 m ² / g. However, BET surface area is not related to catalytic activity. On the other hand, the external surface area increases from 98m ² / g to 237m ² / g by increasing the Si / Al ₂ ratio of ZSM-5.

5 shows an XRD pattern of 10 wt% Cu / ZSM-5 (Non) catalyst according to one embodiment of the present invention.

Referring to FIG. 5, XRD analysis shows that the pattern of XRD assigned to ZSM-5 is displayed on all catalysts, indicating that the structure of ZSM-5 is well maintained even after copper is supported. In addition, XRD patterns corresponding to copper metals (43 ° and 51 °) were observed in all catalysts. On the other hand, although not shown, when comparing the copper crystal sizes of the catalyst, the copper crystal size at 43 ° is between 41.3 nm and 51.1 nm (error range is about ± 10%) Cu / ZSM-5 having various Si / Al ₂ ratios. There is no significant difference in the crystal size of copper between samples.

6 shows SEM images of reduced 10 wt% Cu / ZSM-5 at various ratios according to one embodiment of the present invention. SEM analysis was performed to understand the form of the catalyst.

Referring to FIG. 6, (A) shows a Si / Al ₂ ratio of 30, (B) shows a Si / Al ₂ ratio of 50, (C) shows a Si / Al ₂ ratio of 80, and (D) a Si / Al ₂ ratio of 200. SEM micrographs of phosphorous 10 wt.% Cu / ZSM-5 showed that the morphology of the catalyst was significantly changed by changing the Si / Al ₂ ratio of ZSM-5. For low Si / Al ₂ ratios such as 30 and 50, the particles exhibit a nearly cubic and / or schist (irregular) shape with a particle size of about 200 nm, but high Si / Al ₂ ratios such as 80 and 200. In the case, the particles were found to have a spherical shape with a size greater than 1 μm. Based on the results, the form and particle size of the catalyst can be said to vary considerably by changing the Si / Al ₂ ratio of Cu / ZSM-5.

[Acid Characterization of 10 wt.% Cu / ZSM-5 (Non) Catalysts]

Figure 7 shows the NH ₃ -TPD spectrum of 10 wt% Cu / ZSM-5 (Non) catalyst according to one embodiment of the present invention. NH3-TPD was performed to investigate the acidic properties of the catalyst.

Referring to Figure 7, two major desorption peaks were observed in the catalyst. The first peak below 350 ° C. is due to the weakly acidic site of the catalyst, while the second peak above 350 ° C. comes from the strongly acidic site. The density of the scattering point in the hot zone is determined, which is normalized by the outer surface area since lignin is expected to approach only the outer surface of Cu / ZSM-5. Table 3 shows the density of acid sites in high temperature catalysts.

Entry
Catalyst Acid density
(mmol / m ² ) One 10 wt.% Cu / ZSM-5 (30) 3.2 2 10 wt.% Cu / ZSM-5 (50) 2.5 3 10 wt.% Cu / ZSM-5 (80) 1.8 4 10 wt.% Cu / ZSM-5 (200) 0.6

The acid density (mmol / m ² ) of the catalyst is 10 wt% Cu / ZSM-5 (30) 3.2 mmol / m ² > 10 wt% Cu / ZSM-5 (50) 2.5 mmol / m ² > 10 wt% Cu / ZSM-5 (80) 1.8 mmol / m ² > 10 wt% Cu / ZSM-5 (200) 0.6 mmol / m ² Si / Al ₂ ratio increased by decreasing from 200 to 30.

8 shows the yield of a single aromatic compound according to the acid density of various Si / Al ₂ ratio catalysts according to one embodiment of the present invention. Yield and acid density data of monoaromatic compounds were obtained from Tables 1 and 3, respectively.

Referring to FIG. 8, the yield of monoaromatic compounds increases as the acid density of the catalyst increases. 10 wt% Cu / ZSM-5 (30) in the catalyst exhibited the highest acid density (3.2 mmol / m 2) with the highest yield of single aromatic compound. The acid density of Cu / ZSM-5 plays a crucial role in promoting the depolymerization of lignin in supercritical ethanol.

So far, specific embodiments of the present invention have been described. Those skilled in the art will appreciate that the present invention can be implemented in a modified form without departing from the essential features of the present invention. Therefore, the disclosed embodiments should be considered in descriptive sense only and not for purposes of limitation. The scope of the present invention is shown in the claims rather than the foregoing description, and all differences within the scope will be construed as being included in the present invention.

Claims (10)

metal; And
Lignin decomposition catalyst comprising a zeolite supporting the metal. The method of claim 1,
The lignin decomposition catalyst, characterized in that the metal comprises copper. The method of claim 2,
For the total weight of the lignin decomposition catalyst,
The content of copper is lignin decomposition catalyst, characterized in that 5 to 15% by weight. The method of claim 1,
The zeolite includes silicon and aluminum,
Lignin decomposition catalyst, characterized in that the molar ratio (Si / Al ₂ ) of the silicon to the aluminum is 20 to 40. The method of claim 1,
The zeolite lignin decomposition catalyst, characterized in that it has an MFI structure. A lignin decomposition method comprising the step of performing a reaction for decomposing lignin using the lignin decomposition catalyst according to any one of claims 1 to 5. The method of claim 6,
Lignin decomposition method characterized in that the lignin is decomposed to form a single aromatic compound. The method of claim 6,
And the reaction is carried out in a supercritical fluid. The method of claim 8,
And the supercritical fluid comprises supercritical ethanol. The method of claim 6,
Lignin decomposition method characterized in that the reaction is carried out at a temperature of 400 to 500 ℃.

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