A method for pretreating a biomass feedstock

Abstract

The application discloses a biomass raw material pretreatment method, which realizes efficient decomposition of cellulose, hemicellulose and lignin by mixing and reacting the biomass raw material and a pretreatment liquid, and does not need to pre-smash the biomass raw material, and the pretreatment liquid can be recycled, so that the industrial cost is greatly reduced.

Description

Technical Field

[0001] This invention relates to the field of biomass application technology, specifically to a method for pretreatment of biomass raw materials. Background Technology

[0002] Lignocellulosic biomass is the most abundant renewable resource, boasting wide availability and rich reserves, thus its efficient utilization has attracted widespread attention. However, hemicellulose, cellulose, lignin, and a small amount of impurities in lignocellulosic materials combine to form a dense protective layer, making it difficult to catalytically convert and utilize lignocellulosic materials.

[0003] Common pretreatment methods include acid-base pretreatment, ionic liquid phase pretreatment, and steam explosion pretreatment. However, these methods have some drawbacks, such as high-temperature and high-pressure reaction conditions, severe equipment corrosion, and low pretreatment efficiency.

[0004] Furthermore, existing pretreatment methods often focus solely on cellulose recovery and lignin removal to retain more cellulose and achieve a higher cellulose hydrolysis rate, thereby obtaining more cellulose for enzymatic saccharification. However, they neglect the recovery of lignin and hemicellulose, which does not align with the goal of economic efficiency.

[0005] Therefore, existing biomass raw material pretreatment methods need to be improved. Summary of the Invention

[0006] This invention aims to solve one of the technical problems existing in the prior art. To this end, this invention proposes a method for pretreatment of biomass raw materials.

[0007] According to an embodiment of the present invention, the method includes:

[0008] (1) After mixing and reacting the biomass raw material and the pretreatment liquid, the first solid-liquid separation is carried out to obtain the first solid phase and the first liquid phase;

[0009] (2) After concentrating the first liquid phase, an extractant is added to obtain a suspension. The suspension is then subjected to a second solid-liquid separation to obtain a second solid phase and a second liquid phase.

[0010] In some embodiments, the biomass refers to biomass containing lignin, cellulose, and hemicellulose, and the biomass includes at least one of straw, rice husks, cork, hardwood, and branches, preferably straw. The straw includes, for example, at least one of corn stalks, wheat stalks, rice straw, rapeseed stalks, barley straw, oat straw, and sorghum straw.

[0011] In some embodiments, the pretreatment solution comprises an acid, an alcohol solvent, and water, wherein the mass ratio of the biomass feedstock, acid, alcohol solvent, and water is 1:(0.01–1.8):(2–20):(0.02–0.8), preferably 1:(0.05–1.2):(3–10):(0.1–0.8). It should be noted that the water in the pretreatment solution includes moisture derived from the biomass feedstock.

[0012] In some embodiments, the acid includes at least one of hydrochloric acid, sulfuric acid, sulfurous acid, sulfur dioxide, sulfur trioxide, nitric acid, phosphoric acid, formic acid, acetic acid, and lactic acid. The method of adding the acid is not particularly limited, and may include direct pouring, spraying, steam injection, or injection of acidic gas.

[0013] In some embodiments, the alcohol solvent includes one or more monohydric alcohols and dihydric alcohols, such as methanol, ethanol, isopropanol, ethylene glycol, propylene glycol, and butanediol.

[0014] In some embodiments, the first liquid phase can be used as a pretreatment liquid, mixed and reacted with the next batch of biomass raw materials, and can be recycled 2 to 6 times.

[0015] In some embodiments, in step (1), the reaction temperature is 60–180°C, preferably 80–150°C, and more preferably 110–130°C. For example, 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, etc.

[0016] In some embodiments, the time in step (1) is 0.1 to 20 hours, preferably 2 to 4 hours, for example 0.1 hours, 0.5 hours, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours, 20 hours, etc.

[0017] In some embodiments, in step (1), the first solid phase is washed and then dried to obtain a cellulose-rich material. Specifically, the washing solution used for washing is an alcohol and / or water, and the alcohol includes one or more of methanol, ethanol, isopropanol, ethylene glycol, propylene glycol, and butanediol. When the pH of the washing solution is higher than 3, the washing is terminated, and a cellulose-rich material is obtained. The cellulose-rich material obtained by the above treatment method has extremely low inhibitor content, with furfural inhibitors not exceeding 0.1%, preferably not exceeding 0.05%, such as 0.01%, 0.02%, 0.03%, 0.04%, 0.05%, 0.06%, 0.07%, 0.08%, 0.09%, 0.1%, etc., and organic acid inhibitors not exceeding 1.0 wt%, preferably not exceeding 0.5%, such as 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, etc. Therefore, there is no need for further detoxification treatment of the cellulose-rich material, and it can be directly used in bio-fermentation processes such as ethanol, lactic acid, sugar acid, amino acids, and oils after saccharification.

[0018] In some embodiments, in step (2), the step of adding an extractant after concentrating the first liquid phase specifically includes: evaporating and concentrating the second liquid phase, condensing the vapor to recover the alcohol solvent, then adding an extractant to the concentrate, continuing to evaporate and concentrate until the alcohol content in the concentrate drops below 10%, and obtaining a lignin-containing suspension.

[0019] In some embodiments, in step (2), the extractant includes at least one of water, ethyl acetate, and ethyl formate.

[0020] In some embodiments, in step (2), the second solid phase is washed and dried to obtain a lignin-rich material. Specifically, the washing liquid used for washing can be an alcohol and / or water, wherein the alcohol includes one or more of methanol, ethanol, isopropanol, ethylene glycol, propylene glycol, and butanediol. Washing is terminated when the content of pentose sugars in the washing liquid is not higher than 0.05%, and a lignin-rich material is obtained. The lignin-rich material can be used to produce functional additives such as weather-resistant, flame-retardant, and toughening agents, cement water-reducing agents, and organic fertilizers.

[0021] In some embodiments, in step (2), the second liquid phase is a solution rich in pentose sugars, which include at least one of xylose and arabinose.

[0022] In some embodiments, the cellulose recovery rate is 80-99%, such as 80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, etc.

[0023] In some embodiments, the purity of the cellulose is 50-85%, for example 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, etc.

[0024] In some embodiments, the hemicellulose has a solubility of 50-98%, such as 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 98%, etc.

[0025] In some embodiments, the lignin has a solubility of 45-95%, such as 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, etc.

[0026] In some embodiments, the purity of the lignin is 80-97%, for example 80%, 85%, 90%, 95%, 97%, etc.

[0027] The formula for calculating the cellulose recovery rate is as follows:

[0028] Cellulose recovery rate (%) = Mass of cellulose in cellulose-rich materials / Mass of cellulose in biomass feedstock × 100%.

[0029] The formula for calculating the purity of cellulose is:

[0030] Cellulose purity (%) = Mass of cellulose in cellulose-rich material / Mass of cellulose-rich material × 100%.

[0031] The formula for calculating the hemicellulose solubility is as follows:

[0032] The hemicellulose solubility (%) = (mass of hemicellulose in biomass feedstock - mass of hemicellulose in cellulose-rich materials) / mass of hemicellulose in biomass feedstock × 100%.

[0033] The formula for calculating the lignin solubility rate is as follows:

[0034] Lignin solubility (%) = (mass of lignin in biomass feedstock - mass of lignin in cellulose-rich materials) / mass of lignin in biomass feedstock × 100%.

[0035] The formula for calculating the purity of lignin is as follows:

[0036] Lignin purity (%) = Mass of lignin in lignin-rich material / Mass of lignin-rich material × 100%.

[0037] It should be noted that the specific methods of the first solid-liquid separation and / or the second solid-liquid separation are not particularly limited, such as filtration, centrifugation, etc.

[0038] The beneficial effects of this invention are:

[0039] (1) The method of the present invention reacts under relatively mild conditions, which can preserve the functional structure of lignin and cellulose more completely, which is beneficial to the further processing and utilization of lignin and cellulose. At the same time, it converts hemicellulose into pentose sugar with high utilization value, realizing the full-component separation and recovery of biomass raw materials.

[0040] (2) The pretreatment liquid used in this invention has a low water addition amount, which reduces water consumption and thus reduces water consumption and wastewater treatment costs. Moreover, by recycling the pretreatment liquid, the utilization rate of the pretreatment liquid is improved, thereby reducing costs.

[0041] (3) It can achieve efficient pretreatment without the need for pretreatment steps such as crushing biomass raw materials, which further reduces costs.

[0042] In summary, the pretreatment method of the present invention has great potential for industrial application.

[0043] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Detailed Implementation

[0044] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention, and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0045] Unless otherwise specified, all methods described in the following examples and comparative examples are conventional; and all reagents and materials described are commercially available unless otherwise specified.

[0046] The calculation methods for each indicator in Table 1 are as follows:

[0047] Cellulose recovery rate (%) = Mass of cellulose in cellulose-rich materials / Mass of cellulose in corn stalks × 100%;

[0048] Cellulose purity (%) = Mass of cellulose in cellulose-rich material / Mass of cellulose-rich material × 100%;

[0049] Hemicellulose solubility (%) = (mass of hemicellulose in corn stalks - mass of hemicellulose in cellulose-rich materials) / mass of hemicellulose in corn stalks × 100%;

[0050] Lignin solubility (%) = (mass of lignin in corn stalks - mass of lignin in cellulose-rich materials) / mass of lignin in corn stalks × 100%;

[0051] Lignin purity (%) = Mass of lignin in lignin-rich materials / Mass of lignin-rich materials × 100%;

[0052] The contents of furfural inhibitors and organic acid inhibitors in cellulose-rich materials were determined by liquid chromatography.

[0053] Example 1

[0054] (1) Corn stalks, sulfuric acid (pure), methanol and water (including water in corn stalks) are mixed and reacted in a mass ratio of 1:0.2:4:0.3. The reaction is carried out at 120℃ for 2 hours. After the reaction, the mixture is filtered to obtain the first solid phase and the first liquid phase. The first solid phase is washed with pure methanol until the pH of the washing liquid is below 3. After drying, a material rich in cellulose is obtained.

[0055] (2) The first liquid phase is evaporated and concentrated, and the condensed methanol is recovered. Water is added to the concentrate and mixed. Evaporation and concentration are continued until the methanol content in the concentrate drops below 10%, resulting in a suspension. The suspension is filtered to obtain the second solid phase and the second liquid phase. The second solid phase is washed with pure methanol until the pentose content in the washing liquid is no higher than a certain value.

[0056] 0.05 wt%, after drying, a material rich in lignin is obtained, and the second liquid phase is a solution rich in pentose sugars.

[0057] Example 2

[0058] The mass ratio of corn stalks, sulfuric acid (pure), methanol and water (including moisture from the corn stalks) was 1:0.2:10:0.3, and other parameters were the same as in Example 1.

[0059] Example 3

[0060] The mass ratio of corn stalks, sulfuric acid (pure), methanol and water (including moisture from the corn stalks) was 1:0.2:3:0.3, and other parameters were the same as in Example 1.

[0061] Example 4

[0062] The mass ratio of corn stalks, sulfuric acid (pure), methanol and water (including moisture from the corn stalks) was 1:0.05:4:0.3, and other parameters were the same as in Example 1.

[0063] Example 5

[0064] The mass ratio of corn stalks, sulfuric acid (pure), methanol and water (including moisture from the corn stalks) was 1:0.3:4:0.3, and other parameters were the same as in Example 1.

[0065] Example 6

[0066] The mass ratio of corn stalks, sulfur dioxide, methanol and water (including moisture in the corn stalks) was 1:1.1:4:0.3, and other parameters were the same as in Example 1.

[0067] Example 7

[0068] The mass ratio of corn stalks, sulfuric acid (pure), methanol and water (including moisture from the corn stalks) was 1:0.2:4:0.1, and other parameters were the same as in Example 1.

[0069] Example 8

[0070] The mass ratio of corn stalks, sulfuric acid (pure), methanol and water (including moisture from the corn stalks) was 1:0.2:4:0.8, and other parameters were the same as in Example 1.

[0071] Example 9

[0072] In step (1), the reaction temperature is 80℃ and the time is 9h.

[0073] Example 10

[0074] In step (1), the reaction temperature is 140℃ and the time is 1h.

[0075] Comparative Example 1

[0076] The mass ratio of corn stalks, sulfuric acid (pure), methanol and water (including moisture from the corn stalks) was 1:0.2:4:0, and other parameters were the same as in Example 1.

[0077] Comparative Example 2

[0078] The mass ratio of corn stalks, sulfuric acid (pure), methanol and water (including moisture from the corn stalks) was 1:0:4:0.3, and other parameters were the same as in Example 1.

[0079] Comparative Example 3

[0080] The mass ratio of corn stalks, sulfuric acid (pure), methanol and water (including moisture from the corn stalks) is 1:0:4:0, and other parameters are the same as in Example 1.

[0081] Comparative Example 4

[0082] The mass ratio of corn stalks, sulfuric acid (pure), methanol and water (including moisture from the corn stalks) was 1:0.2:2:2.3, and other parameters were the same as in Example 1.

[0083] The effects of the preprocessing methods in each embodiment and comparative example are shown in Table 1:

[0084] Table 1

[0085]

[0086]

[0087] Comparative Examples 1-3 and Comparative Example 2 show that the lignin solubility gradually increases with the increase of alcohol content in the pretreatment solution. Comparative Examples 1 and 4-5 show that the hemicellulose solubility gradually increases with the increase of acid content in the pretreatment solution and reaches equilibrium. Comparative Examples 1, 7-8, and Comparative Example 1 show that the presence of water is beneficial to promoting the removal of hemicellulose, but excessive water is not conducive to the removal of lignin and may increase the steam consumption of the entire process. Comparative Examples 1 and 9-10 show that increasing the temperature is beneficial to promoting the removal of hemicellulose and lignin, but excessively high temperatures will reduce the cellulose recovery rate and increase the generation of inhibitors.

[0088] Although preferred embodiments of the invention have been disclosed for the purpose of illustrating the invention, those skilled in the art should understand that various modifications, additions, and substitutions can be made to the invention without departing from the concept and scope of the invention as defined in the claims.

Claims

1. A method for pretreatment of biomass raw materials, characterized in that, The method includes: (1) After mixing and reacting the biomass raw material and the pretreatment liquid, the first solid-liquid separation is carried out to obtain the first solid phase and the first liquid phase; (2) After concentrating the first liquid phase, an extractant is added to obtain a suspension. The suspension is then subjected to a second solid-liquid separation to obtain a second solid phase and a second liquid phase.

2. The method according to claim 1, characterized in that, In step (1), the pretreatment liquid includes acid, alcohol solvent and water, and the mass ratio of the biomass raw material, acid, alcohol solvent and water is 1:(0.01~1.8):(2~20):(0.02~0.8), preferably 1:(0.05~1.2):(3~10):(0.1~0.8).

3. The method according to claim 1, characterized in that, The biomass raw materials include at least one of straw, rice husks, cork, hardwood, and branches.

4. The method according to claim 1, characterized in that, In step (1), the reaction temperature is 60-180°C, preferably 80-150°C, more preferably 110-130°C, and the time is 0.1-20h, preferably 2-4h.

5. The method according to claim 2, characterized in that, The alcohol solvent includes at least one of methanol, ethanol, isopropanol, ethylene glycol, propylene glycol, and butanediol; and / or, The acid includes at least one of hydrochloric acid, sulfuric acid, sulfurous acid, sulfur dioxide, sulfur trioxide, nitric acid, phosphoric acid, formic acid, acetic acid, and lactic acid.

6. The method according to claim 1, characterized in that, In step (1), the first liquid phase is used as a pretreatment liquid and recycled 2 to 6 times.

7. The method according to claim 1, characterized in that, In step (2), the second solid phase is washed and dried to obtain a cellulose-rich material; and / or, The content of furfural inhibitors in the cellulose-rich material is not higher than 0.1%, preferably not higher than 0.05%, and the content of organic acid inhibitors is not higher than 1.0%, preferably not higher than 0.5%.

8. The method according to claim 1, characterized in that, In step (2), the extractant includes at least one of water, ethyl acetate and ethyl formate.

9. The method according to claim 1, characterized in that, In step (2), the second solid phase is washed and dried to obtain a lignin-rich material; and / or, The second liquid phase is a solution rich in pentose sugars, including one or more of xylose and arabinose.

10. The method according to claim 1, characterized in that, Cellulose recovery rate is 80-99%, purity is 50-85%; and / or, The solubility of hemicellulose is 50-98%; and / or, The solubility of lignin is 45-95%, and its purity is 80-97%.

Images