Method for producing decomposition product

Abstract

To provide a method for obtaining a decomposition product from lignocellulosic biomass in a high yield.SOLUTION: A method for producing a decomposition product from lignocellulosic biomass, comprising a step of heating the lignocellulosic biomass in the presence of a metal element catalyst at 250 °C or more and 500 °C or less, wherein the step is performed in the absence of hydrogen under normal pressure or under reduced pressure, and the decomposition product contains at least one selected from the group consisting of an aromatic monomer and a product gas.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to methods for producing decomposition products. [Background technology]

[0002] Biomass, especially lignocellulosic biomass, has attracted attention from the viewpoints of preventing global warming and achieving carbon neutrality. Because lignocellulosic biomass is an abundant carbon source, producing carbon compounds from lignocellulosic biomass is important from the viewpoint of biorefinery.

[0003] Patent Document 1 (Japanese Patent Laid-Open Publication No. 2024-27327) discloses a method for obtaining aromatic monomers by decomposing lignin in the presence of a catalyst within a predetermined temperature range.

[0004] Non-Patent Document 1 (Energy & Environment Science, 2016, 9, pp. 2939-2977) discloses gasification from biomass (biomass gasification). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2024-27327 [Non-patent literature]

[0006] [Non-Patent Document 1] Energy & Environment Science, 2016, 9, p2939-2977 Summary of the Invention [Problem to be solved by the invention]

[0007] In the method of Patent Document 1, the decomposition is carried out in the presence of hydrogen, and therefore the reaction must be carried out in a closed system.

[0008] According to Non-Patent Document 1, the gasification of woody biomass usually requires a reaction at high temperatures of 700°C or higher. In addition, there are issues such as equipment malfunctions due to the by-product tar and catalyst deactivation.

[0009] The present disclosure has been made to solve the above-mentioned problems, and aims to provide a method for obtaining decomposition products from lignocellulosic biomass in high yield. [Means for solving the problem]

[0010] [1] A method for producing decomposition products from lignocellulosic biomass, comprising: heating the lignocellulosic biomass at 250°C or higher and 500°C or lower in the presence of a metal element catalyst; The process is carried out in the absence of hydrogen, at atmospheric pressure or at reduced pressure, A method for producing a cracked product, wherein the cracked product contains at least one selected from the group consisting of an aromatic monomer and a product gas.

[0011] [2] The method for producing a decomposition product according to [1], wherein the decomposition product contains the aromatic monomer and the product gas.

[0012] [3] The method for producing a decomposition product according to [1] or [2], wherein the decomposition product contains the aromatic monomer and carbon monoxide.

[0013] [4] The method for producing a decomposition product according to any one of [1] to [3], wherein the decomposition product contains the aromatic monomer, carbon monoxide, and hydrogen.

[0014] [5] The method for producing a decomposition product according to any one of [1] to [4], wherein the lignocellulosic biomass is woody biomass.

[0015] [6] The method for producing a decomposition product according to any one of [1] to [5], wherein the metal element catalyst is a palladium catalyst supported on solid carbon. [Effects of the Invention]

[0016] According to the present disclosure, a method for obtaining decomposition products from lignocellulosic biomass in high yield can be provided. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a schematic diagram showing reaction pathways for producing decomposition products from lignocellulosic biomass. [Figure 2] FIG. 2 is a schematic diagram showing an example of an apparatus used in the production method of the present disclosure. [Figure 3] FIG. 3 is a graph showing an example of the yield of aromatic monomers obtained by decomposition of lignocellulosic biomass. [Figure 4] FIG. 4 is a graph showing examples of yields of carbon monoxide and other gases obtained from the decomposition of lignocellulosic biomass. [Figure 5] FIG. 5 is a graph showing an example of the relative composition of carbon monoxide and other gases resulting from the decomposition of lignocellulosic biomass. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, embodiments of the present disclosure will be described in detail.

[0019] The method for producing decomposition products from lignocellulosic biomass disclosed herein includes a step of heating lignocellulosic biomass at 250°C to 500°C in the presence of a metal element catalyst. The step is carried out in the absence of hydrogen and under atmospheric pressure or reduced pressure. The decomposition products include at least one selected from the group consisting of aromatic monomers and product gases.

[0020] (lignocellulosic biomass) Lignocellulosic biomass is biomass whose main component is lignocellulose. Lignocellulose is a component of plant cell walls and contains lignin, cellulose, and hemicellulose. Examples of lignocellulosic biomass include woody biomass, herbaceous biomass, processed products thereof, and waste products thereof.

[0021] Examples of woody biomass include broad-leaved trees and coniferous trees. Examples of broad-leaved trees include maple, oak, sawtooth oak, yew, beech, and horse chestnut. Examples of coniferous trees include pine, cedar, cypress, hemlock, Abies sachalinensis, and larch. Coniferous trees are more difficult to decompose than broad-leaved trees. From this perspective, broad-leaved trees are preferred as woody biomass.

[0022] Examples of woody biomass waste and processed materials include bark, branches, fruit bunches, and fruit shells from broad-leaved and coniferous trees. Also, processed materials such as plywood and fiberboard made from broad-leaved and coniferous trees can be used. Also, dismantled parts after use can be used.

[0023] Examples of herbaceous biomass include rice, wheat, sugarcane, pineapple, sugarcane, oil palm, corn, bamboo, and bamboo grass.

[0024] From the viewpoint of ease of decomposition, pulverized lignocellulose biomass (for example, wood flour) is preferred.

[0025] (decomposition products) Cracking products in this disclosure include aromatic monomers and product gases.

[0026] Figure 1 is a schematic diagram showing the reaction pathway for producing decomposition products from lignocellulosic biomass. Referring to Figure 1, lignin contained in lignocellulosic biomass is converted into aromatic compounds with radicals and unsaturated side chains by heating. The converted aromatic compounds are mainly converted into aromatic monomers by the action of a metal catalyst. Meanwhile, cellulose and hemicellulose contained in lignocellulosic biomass are converted into product gases by heating in the presence of a metal catalyst. Cellulose and hemicellulose are polysaccharide components containing many hydroxyl groups, and they also generate active hydrogen species necessary for stabilizing and depolymerizing lignin-derived radicals and aromatic compounds with unsaturated side chains. Therefore, reactions that were previously performed in the presence of hydrogen can now be performed in the absence of hydrogen.

[0027] [Aromatic Monomers] An aromatic monomer is an aromatic compound having one aromatic ring. As described above, the aromatic monomer is an aromatic compound as a segment obtained by decomposing lignin contained in lignocellulosic biomass.

[0028] The aromatic monomer is not particularly limited as long as it is an aromatic compound having one aromatic ring, and examples thereof include aromatic monomers having a syringyl nucleus (S nucleus), aromatic monomers having a guaiacyl nucleus (G nucleus), and aromatic monomers having a catechol nucleus (C nucleus). Examples of aromatic monomers having an S nucleus include syringol (S) (boiling point: 261°C), methyl syringol (Me-S) (boiling point: 268°C), ethyl syringol (Et-S) (boiling point: 273°C), and propyl syringol (Pr-S) (boiling point: 285°C). Examples of aromatic monomers having a G nucleus include guaiacol (G) (boiling point: 205°C), methyl guaiacol (Me-G) (boiling point: 221°C), ethyl guaiacol (Et-G) (boiling point: 221°C), and propyl guaiacol (Pr-G) (boiling point: 264°C). Examples of aromatic monomers having a C nucleus include catechol (boiling point: 245°C), ethyl catechol (Et-C) (boiling point: 273°C), etc. These aromatic monomers can be separated into various aromatic monomers by conventional methods.

[0029] [Produced gas] The product gas is obtained by decomposition of the cellulose and hemicellulose contained in the lignocellulosic biomass.

[0030] Examples of the produced gas include carbon monoxide (CO), carbon dioxide (CO2), hydrocarbon gas, hydrogen (H2), etc. Examples of the hydrocarbon gas include methane gas (CH4), acetylene gas (C2H2), ethylene gas (C2H4), ethane gas (C2H6), propylene gas (C3H6), and propane gas (C3H8).

[0031] In this disclosure, the main product gases are CO and H. CO and H are expected to be used as raw materials for petroleum synthesis and methane synthesis, and biomass-derived CO in particular is expected to lead to a reduction in CO.

[0032] (Process) The method for producing decomposition products of the present disclosure includes a step of decomposing lignocellulosic biomass in the presence of a metal element catalyst at 250° C. to 500° C. The step is carried out in the absence of hydrogen and under atmospheric pressure or reduced pressure.

[0033] [Metal element catalyst] The metal element catalyst used in this step is not particularly limited as long as it can carry out the step. Examples of the metal element catalyst include catalysts containing metal elements such as palladium (Pd), platinum (Pt), and ruthenium (Ru). From the viewpoint of increasing the yield of the mixture, the metal element catalyst is preferably a catalyst supported on solid carbon, and more preferably a palladium catalyst (catalyst containing Pd) supported on solid carbon (Pd / C). Here, solid carbon refers to solid carbon, and from the viewpoint of increasing catalytic activity, porous carbon with a large surface area, such as activated carbon, is preferred.

[0034] [temperature] The temperature in this step is 250°C or higher and 500°C or lower. From the viewpoint of increasing the yield of decomposition products, particularly the yield of low-boiling-point aromatic monomers, the temperature in this step may be 300°C or higher, or 350°C or higher. Furthermore, from the viewpoint of suppressing thermal degradation of the apparatus and secondary decomposition of the aromatic monomers, the temperature in this step may be 450°C or lower, or 400°C or lower.

[0035] [time] The time for this step is not particularly limited, but may be 10 minutes or more, 30 minutes or more, or 60 minutes or more from the viewpoint of increasing the yield of the decomposition product, and may be 180 minutes or less, 150 minutes or less, or 120 minutes or less from the viewpoint of suppressing thermal degradation of the device.

[0036] [hydrogen] This process is carried out in the absence of hydrogen, under atmospheric pressure or reduced pressure. In this process, aromatic monomers are obtained by decomposition of lignin as described above. It is believed that the decomposition of lignin involves thermal decomposition followed by hydrocracking. Therefore, it is believed that the presence of hydrogen promotes hydrocracking.

[0037] On the other hand, decomposition of lignin in the presence of hydrogen requires a closed system. Carrying out this process in a closed system poses limitations, such as the need to pressurize the hydrogen and the need to use equipment that can be used in closed systems. Furthermore, hydrogen has issues such as being easily ignited, embrittling metal materials, and being expensive.

[0038] As described above, lignocellulosic biomass contains cellulose and hemicellulose, which are polysaccharides containing hydroxyl groups. Because these hydroxyl-containing components are decomposed and function as active hydrogen species, this process can be carried out in the absence of hydrogen. Furthermore, because hydrogen is not present, this process does not need to be carried out in a closed system. In other words, this process is carried out under normal pressure or reduced pressure, eliminating the above-mentioned limitations.

[0039] This step may be carried out in the absence of hydrogen, for example, in an inert atmosphere or in the air, such as in the presence of nitrogen or argon.

[0040] [solvent] This step may be carried out by immersing the lignocellulosic biomass and the metal catalyst in a solvent. Examples of the solvent include organic solvents that dissolve the aromatic monomers. From the viewpoint of separation from the aromatic monomers, the organic solvent preferably has a boiling point higher than that of the aromatic monomers, and aprotic organic solvents are more preferred. Examples of such organic solvents include eicosane (boiling point: 343°C), triacontane (boiling point: 450°C), 1,3-diphenoxybenzene (boiling point: 375°C), and 1,3,5-triphenylbenzene (boiling point: 460°C).

[0041] However, the use of a solvent in this step may lead to a decrease in efficiency, since it is necessary to separate the aromatic monomer from the solvent, and it is necessary to distill and remove the solvent each time this step is carried out, etc. Therefore, even when a solvent is used in this step, it is preferable to reduce the amount used.

[0042] [Device] The apparatus for carrying out this process is not particularly limited as long as it can carry out this process. For example, referring to FIG. 2, apparatus 10 includes a gas bag 1, a reactor 2, and a heating mechanism 3. Lignocellulosic biomass, a metal element catalyst, and optionally a solvent are added to reactor 2, and the mixture is heated by heating mechanism 3 to obtain a decomposition product. The aromatic monomer is contained in the solution obtained by recovering the residue in reactor 2 after the reaction is completed, filtering, and extracting with an organic solvent. The gas product is contained in gas bag 1.

[0043] From the viewpoint of promoting the reaction, a rotor may be placed in the reactor 2 and the contents may be stirred by a magnetic stirrer 4. When this step is carried out in the presence of nitrogen, the reactor 2 may be closed with a lid 5. When this step is carried out in the atmosphere, the reactor 2 may be open.

[0044] (effect) From the above, the present disclosure is expected to have the following effects. Specifically, all components contained in lignocellulosic biomass can be converted into aromatic monomers and useful chemicals such as CO and H. By using lignocellulosic biomass as a feedstock, the reaction can proceed in the absence of a hydrogen catalyst. Because hydrogen is not required, the reaction can be carried out under normal or reduced pressure, and as a result, the products can be volatilized and recovered while lignocellulosic biomass is continuously introduced. [Example]

[0045] The following examples are provided to illustrate, but not to limit, the scope of the claims.

[0046] (No.1) A decomposition apparatus with the configuration shown in Figure 2 was prepared. 100 mg of beech wood flour was prepared as lignocellulosic biomass, and 0.6 g of 1,3-diphenoxybenzene was prepared as a solvent. The beech wood flour and 1,3-diphenoxybenzene were added to the reactor, a rotor was inserted, and the reactor was then filled with nitrogen to create a closed environment. The reactor was heated to 350°C using the heating mechanism, and the contents were stirred for 30 minutes using a magnetic stirrer, allowing the beech wood flour to be decomposed.

[0047] Nitrogen was introduced into the bottom of reactor 2, and the gas remaining in reactor 2 was transferred to gas bag 1 containing neon as an internal standard. The composition and yield of each gas in the gas product were measured by micro gas chromatography. The obtained heat-denatured beech wood flour was filtered and extracted with an ethyl acetate-containing aqueous solution (ethyl acetate:water = 1:1 (volume ratio)) to obtain an ethyl acetate-soluble product, a water-soluble product, and a solid residue. The molecular weight of each aromatic monomer in the ethyl acetate-soluble product was measured by gel permeation chromatography (GPC), and the yield of each aromatic monomer was measured by gas chromatography / mass spectrometry (GC / MS). The results are shown in Tables 2 to 4 and Figures 3 to 5. Table 1 lists the materials and test conditions used in No. 1 and Nos. 2 to 13, which will be described later.

[0048] (No.2) As a metal element catalyst, 25 mg of palladium catalyst supported on solid carbon, Pd / C (Pd content of the entire catalyst: 5% by mass) (Nacalai Tesque, product number 25910) was prepared. All other points were the same as No. 1.

[0049] Beech wood flour was decomposed under the same conditions as in No. 1, except that beech wood flour, 1,3-diphenoxybenzene, and Pd / C were added to the reactor. The composition and yield of each gas in the gas product, as well as the molecular weight and yield of each aromatic monomer in the ethyl acetate solution, were measured using the same methods as in No. 1. The results are shown in Tables 2 to 4 and Figures 3 to 5.

[0050] (No.3~5) Beech wood flour was decomposed using the same material as in No. 2, except that the conditions were changed to those listed in Table 1. The composition and yield of each gas in the gas product, as well as the molecular weight and yield of each aromatic monomer in the ethyl acetate solution, were measured using the same methods as in No. 1. The results are shown in Tables 2 to 4 and Figures 3 to 5.

[0051] (No.6) 100 mg of cedar wood flour (manufactured by Naka Wood Co., Ltd.) was prepared as lignocellulosic biomass. The decomposition of cedar wood flour was otherwise carried out under the same conditions as in No. 1. The composition and yield of each gas in the gas product, as well as the molecular weight and yield of each aromatic monomer in the ethyl acetate solution, were measured using the same methods as in No. 1. The results are shown in Tables 2 to 4 and Figures 3 to 5.

[0052] (No.7) Decomposition of cedar wood flour was carried out under the same conditions as in No. 2, except that cedar wood flour was used as the lignocellulosic biomass. The composition and yield of each gas in the gas product, as well as the molecular weight and yield of each aromatic monomer in the ethyl acetate solution, were measured using the same methods as in No. 1. The results are shown in Tables 2 to 4 and Figures 3 to 5.

[0053] (No.8~10) Decomposition of cedar wood flour was carried out using the same material as in No. 7, except that the conditions were changed to those listed in Table 1. In addition, the composition and yield of each gas in the gas product, as well as the molecular weight and yield of each aromatic monomer in the ethyl acetate solution, were measured using the same methods as in No. 1. The results are shown in Tables 2 to 4 and Figures 3 to 5.

[0054] (No.11) 25 mg of beech ground lignin (Buna MWL) was prepared as the raw material. Other than that, the decomposition of Buna MWL was carried out under the same conditions as in No. 2. The composition and yield of each gas in the gas product, as well as the molecular weight and yield of each aromatic monomer in the ethyl acetate solution, were measured using the same methods as in No. 1. The results are shown in Table 2 and Figure 3.

[0055] (No.12) 33 mg of ground cedar lignin (cedar MWL) was prepared as the raw material. Otherwise, decomposition of cedar MWL was carried out under the same conditions as in No. 2. The composition and yield of each gas in the gas product, as well as the molecular weight and yield of each aromatic monomer in the ethyl acetate solution, were measured using the same methods as in No. 1. The results are shown in Table 2 and Figure 3. As mentioned above, product gas was obtained by the decomposition of cellulose and hemicellulose, so no product gas was obtained from beech MWL or cedar MWL.

[0056] (No.13) 100 mg of cellulose (Avicel®) was prepared. Otherwise, the cellulose decomposition was carried out under the same conditions as in No. 2. The composition and yield of each gas in the gas product, as well as the molecular weight and yield of each aromatic monomer in the ethyl acetate solution, were measured using the same methods as in No. 1. The results are shown in Tables 3 and 4 and Figures 4 and 5. As mentioned above, aromatic monomers are obtained by decomposition of lignin, so aromatic monomers were not obtained from cellulose.

[0057] In Table 2, aromatic monomers are derived from the benzene rings of lignin contained in lignocellulosic biomass. In Tables 3 and 4, the product gases are derived from the carbon of cellulose and hemicellulose contained in lignocellulosic biomass. In Table 2, "DHSA" represents dihydrosinapyl alcohol, "IS" represents 4-propenylsyringol, "VS" represents syringaldehyde, "DHCA" represents dihydroconiferyl alcohol, "EG" represents eugenol, "IG" represents trans-isoeugenol, "Cis-IG" represents cis-isoeugenol, and "VG" represents vanillin.

[0058] [Table 1]

[0059] [Table 2]

[0060] [Table 3]

[0061] [Table 4]

[0062] In No. 1, the yields of aromatic monomers, which are decomposition products, and the product gas (CO) were lower than in Nos. 2 to 5. In addition, compared to Nos. 2 to 5, almost no H2 was produced.

[0063] In Nos. 2 and 3, the yields of aromatic monomers, which are cracking products, and the product gas (CO) were higher in No. 3 than in No. 2. The production rate of H2 was also higher in No. 3 than in No. 2.

[0064] In Nos. 4 and 5, the yield of aromatic monomers, which are cracking products, was higher in No. 4 than in No. 5, and the yield of product gas (CO) and the rate of H2 production were higher in No. 5 than in No. 4.

[0065] In No. 6, the yields of aromatic monomers, which are decomposition products, and the product gas (CO) were lower than in Nos. 7 to 10. In addition, compared to Nos. 7 to 10, almost no H2 was produced.

[0066] In No. 7 and No. 8, the yield of aromatic monomers, which are decomposition products, was higher in No. 8 than in No. 7. There was also little difference in the yield of product gas (CO) and the rate of H2 production.

[0067] There was almost no difference in the yield of aromatic monomers, which were decomposition products, between Nos. 9 and 10. In addition, the yield of product gas (CO) and the rate of H2 production were higher in No. 10 than in No. 9.

[0068] The yields of aromatic monomers and CO produced as decomposition products in Nos. 1 and 6, which did not use a metal catalyst, were lower than those in Nos. 2 to 5 and 7 to 10. This is thought to be because the decomposition of lignin, cellulose, and hemicellulose did not progress.

[0069] No product gas was obtained from Nos. 11 and 12. Because product gas is obtained by the decomposition of cellulose and hemicellulose, it is thought that it was not obtained from the beech MWL and cedar MWL. Furthermore, no aromatic monomers were obtained from No. 13. Because aromatic monomers are obtained by the decomposition of lignin, it is thought that they were not obtained from cellulose.

[0070] The above examples confirmed that the method for producing cracked products of the present disclosure makes it possible to obtain aromatic monomers and product gas (CO) in high yields.

[0071] The embodiments and examples disclosed herein are illustrative in all respects and should not be considered limiting. The scope of the present invention is defined by the claims rather than the above-described embodiments and examples, and it is intended to include any modifications within the scope of the claims that are equivalent to the claims. [Explanation of symbols]

[0072] 1 gas bag, 2 reactor, 3 heating mechanism, 4 magnetic stirrer, 5 lid, 10 apparatus.

Claims

1. 1. A method for producing degradation products from lignocellulosic biomass, comprising: heating the lignocellulosic biomass at 250°C or higher and 500°C or lower in the presence of a metal element catalyst; The process is carried out in the absence of hydrogen, at atmospheric pressure or at reduced pressure, The method for producing a cracked product, wherein the cracked product contains at least one selected from the group consisting of an aromatic monomer and a product gas.

2. The method for producing a cracked product according to claim 1 , wherein the cracked product comprises the aromatic monomer and the product gas.

3. The method for producing a decomposition product according to claim 1 or 2, wherein the decomposition product comprises the aromatic monomer and carbon monoxide.

4. The method for producing a decomposition product according to claim 1 or 2, wherein the decomposition product comprises the aromatic monomer, carbon monoxide, and hydrogen.

5. The method for producing a decomposition product according to claim 1 or 2, wherein the lignocellulosic biomass is woody biomass.

6. The method for producing a decomposition product according to claim 1 or 2, wherein the metal element catalyst is a palladium catalyst supported on solid carbon.

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