Method for pretreating lignocellulose biomass by using ionic liquid-assisted organic solvent two-phase system to realize directional fractionation of components and improve enzymolysis performance

Abstract

The invention discloses a method for pretreating lignocellulose biomass by using an ionic liquid-assisted organic solvent two-phase system to realize directional fractionation of components and improve enzymolysis performance. The method comprises the following steps: pretreatment of a lignocellulose biomass raw material, biphase pretreatment of an ionic liquid [BHEM] meso-assisted organic solvent, enzymatic hydrolysis for sugar production, and extraction of hemicellulose and lignin. The method disclosed by the invention has the advantages that efficient separation of components and excellent enzymolysis efficiency of a substrate are realized through an ionic liquid assisted organic solvent aqueous solution, and hemicellulose and lignin derivatives which are pretreated and disassembled are respectively dissolved into a water phase and an organic phase through a two-phase system, so that the complex operation of separating due to mixing of the components of the pretreatment liquid is reduced; directional dissolution of lignocellulose biomass components is achieved, practicability is high, and full-component value-added conversion of staple cellulose and lignin is facilitated.

Description

Technical Field

[0001] The invention relates to the field of biomass refining, and in particular to a method for pretreating lignocellulosic biomass by using an ionic liquid-assisted organic solvent biphasic system to achieve component directional fractionation and improve enzymatic hydrolysis performance. Background Art

[0002] As a representative bioenergy raw material, lignocellulosic biomass has become a promising solution to replace fossil fuels and become the new core of industrial energy due to its wide distribution and large reserves. However, the inherent complexity of lignocellulosic biomass poses major challenges: the strong chemical bonds and complex physical entanglements of cellulose, hemicellulose, and lignin make them difficult to use directly. Unleashing the full potential of lignocellulosic biomass requires advanced pretreatment methods to destroy its stubborn structure and fractionate its components for subsequent conversion and utilization.

[0003] Ionic liquids have excellent solubility and stability and have become widely studied pretreatment solvents. However, single ionic liquid pretreatment often has problems such as high cost and high viscosity. Co-solvents are considered to be a solution to this problem. However, ionic liquid co-solvent systems have so far focused on traditional single-phase solvents, including polar aprotic solvents (such as dimethyl sulfoxide, acetone), polyols (such as glycerol, ethylene glycol) and monohydric alcohols (such as methanol, ethanol). In recent years, organic solvents that can form two phases that are immiscible with water, such as phenoxyethanol, methyl isobutyl ketone and 2-methyltetrahydrofuran, have shown good pretreatment capabilities, but the use of these solvents alone requires high reaction temperatures and long reaction times. In response to the above problems, a two-phase solvent system was constructed using ionic liquids with good hemicellulose removal and delignification effects and these solvents, which can not only effectively exert the efficient and excellent pretreatment capabilities of ionic liquids, but also maximize the stability of lignocellulosic biomass and ensure the efficient separation and utilization of hemicellulose and lignin. This system combines the good pretreatment effect of ionic liquids with the fractionation characteristics of organic solvent-water two-phase separation. After pretreatment, lignin and hemicellulose were selectively extracted into the organic phase and aqueous phase, respectively, while cellulose was retained in the solid phase. In addition, the composite system pretreatment can achieve excellent pretreatment effects under mild pretreatment conditions. Summary of the invention

[0004] The purpose of the present invention is to provide a method for pretreating lignocellulosic biomass using an ionic liquid-assisted organic solvent dual-phase system to achieve directional fractionation of components and improve enzymatic hydrolysis performance. In view of the current situation that the components of the pretreatment liquid are mixed and separated complicatedly after the pretreatment of lignocellulosic biomass, an organic solvent aqueous solution dual-phase system is used in the selection of pretreatment solvents, so that the hemicellulose and lignin derivatives disassembled after the reaction are directional dissolved in the aqueous phase and the organic phase respectively, which is beneficial to the subsequent value-added conversion of the components and realizes the full component utilization of lignocellulosic biomass. In addition, the synergistic effect of the ionic liquid-organic solvent aqueous solution dual-phase system promotes component separation and improves the hydrolysis sugar production efficiency.

[0005] To achieve this object, the present invention adopts the following technical solution: a method for pretreating lignocellulosic biomass using an ionic liquid-assisted organic solvent biphasic system to achieve component-oriented fractionation and improve enzymatic hydrolysis performance.

[0006] The features include:

[0007] 1. Pretreatment of lignocellulosic biomass raw materials: Pretreatment of lignocellulosic biomass raw materials: The lignocellulosic raw materials are treated with a neutral detergent to remove non-structural components, crushed through a 40-mesh sieve and placed in a 60° C. oven to dry to constant weight for later use.

[0008] 2. Ionic liquid [BHEM] mesy assisted organic solvent two-phase system pretreatment: The raw material is mixed with the ionic liquid pentanol system for pretreatment; after the pretreatment, the solid and liquid are separated. The solid is repeatedly washed and dried with hot water and ethanol and then used for enzymatic hydrolysis, and the filtrate is directly refrigerated and stored for subsequent hemicellulose and lignin extraction.

[0009] 3. Enzymatic hydrolysis to produce sugar: The solid matrix dried in step 2) is mixed with a buffer solution at 2-30% (w / v), and hydrolyzed by cellulase to obtain a sugar solution. The buffer solution is composed of a 0.1 mol citric acid buffer solution at pH 4.8.

[0010] 4. Extraction of hemicellulose and lignin: The aqueous phase and organic phase in the filtrate obtained by pretreatment are separated by a separatory funnel. For the aqueous phase, i.e., the aqueous solution of hemicellulose derivatives, the target concentration of sugar solution can be obtained by rotary evaporation concentration; for the organic phase, i.e., the lignin dissolved therein, the lignin precipitate can be obtained by acid precipitation method.

[0011] Invention Advantages

[0012] 1. The present invention adopts an ionic liquid-assisted organic solvent two-phase system to pretreat lignocellulosic biomass.

[0013] 2. The present invention is applicable to a wide range of raw materials, including agricultural and forestry waste biomass from various sources.

[0014] 3. The ionic liquid and organic solvent used in the present invention are both composed of low-cost and green sources.

[0015] 4. The present invention combines ionic liquids with a two-phase solvent system, reduces pretreatment reaction conditions such as temperature and time, promotes component separation, and achieves separation of lignocellulosic biomass components under mild conditions.

[0016] 5. The present invention realizes the directional dissolution of lignocellulosic biomass components and avoids the complicated operation of subsequent separation. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a comparison of the surface morphology before and after pretreatment in the specific embodiment 2 of the present invention. DETAILED DESCRIPTION

[0018] The present invention is further described below by way of examples, but the protection scope of the present invention is not limited to the contents described.

[0019] Example 1

[0020] 1) After removing the non-structural components, the corn stalks are crushed and passed through a 40-mesh sieve, placed in an oven and dried for use at any time.

[0021] 2) Take 1g of raw material, add 20g of reaction solvent, the solvent is a mixed system consisting of 2g of ionic liquid and 18g of amyl alcohol aqueous solution (60%wt). After mixing evenly, heat to 120℃ for 45min; after the reaction is completed, separate the solid and liquid, wash the solid with ethanol and water for many times, and measure the components after drying. Among them, the cellulose retention rate is 96.1%, the hemicellulose removal rate is 69.2%, and the lignin removal rate is 58.7%.

[0022] 3) Take 0.2 g of the solid matrix dried in step 2) above, add it to 10 ml of citric acid buffer at about pH 4.8, add 7.2 mg / g cellulase, place it in a 50°C shaker for enzymatic hydrolysis at 180 rpm, and measure the sugar content at regular intervals. The enzymatic hydrolysis cycle is 72 h.

[0023] 4) The pretreated liquid after the reaction in the above step 2) is separated into an upper organic phase and a lower aqueous phase by a separatory funnel. The sugar content in the aqueous phase is determined by high performance liquid chromatography; the dissolved lignin in the organic phase is precipitated by acid precipitation with a pH 2 HCL solution to obtain lignin.

[0024] Example 2

[0025] 1) After removing the non-structural components, the corn stalks are crushed and passed through a 40-mesh sieve, placed in an oven and dried for use at any time.

[0026] 2) Take 1g of raw material, add 20g of reaction solvent, the solvent is a mixed system consisting of 2g of ionic liquid and 18g of amyl alcohol aqueous solution (60%wt). After mixing evenly, heat to 140℃ for 45min; after the reaction is completed, separate the solid and liquid, wash the solid with ethanol and water for many times, and measure the components after drying. Among them, the cellulose retention rate is 92.3%, the hemicellulose removal rate is 86.3%, and the lignin removal rate is 80.6%.

[0027] 5) Take 0.2 g of the solid matrix dried in step 2) above, add it to 10 ml of citric acid buffer at about pH 4.8, add 7.2 mg / g cellulase, place it in a 50°C shaker for enzymatic hydrolysis at 180 rpm, and measure the sugar content at regular intervals. The enzymatic hydrolysis cycle is 72 h.

[0028] 6) The pretreated liquid after the reaction in the above step 2) is separated into an upper organic phase and a lower aqueous phase by a separatory funnel. The sugar content in the aqueous phase is determined by high performance liquid chromatography; the dissolved lignin in the organic phase is precipitated by acid precipitation with a pH 2 HCL solution to obtain lignin.

[0029] Example 3

[0030] 1) After removing the non-structural components, the corn stalks are crushed and passed through a 40-mesh sieve, placed in an oven and dried for use at any time.

[0031] 2) Take 1g of raw material, add 20g of reaction solvent, the solvent is a mixed system consisting of 2g of ionic liquid and 18g of amyl alcohol aqueous solution (60%wt). After mixing evenly, heat to 160℃ for 45min; after the reaction is completed, separate the solid and liquid, wash the solid with ethanol and water for many times, and measure the components after drying. Among them, the cellulose retention rate is 84.5%, the hemicellulose removal rate is 98.6%, and the lignin removal rate is 67.4%.

[0032] 3) Take 0.2 g of the solid matrix dried in step 2) above, add it to 10 ml of citric acid buffer at about pH 4.8, add 7.2 mg / g cellulase, place it in a 50°C shaker for enzymatic hydrolysis at 180 rpm, and measure the sugar content at regular intervals. The enzymatic hydrolysis cycle is 72 h.

[0033] 4) The pretreated liquid after the reaction in the above step 2) is separated into an upper organic phase and a lower aqueous phase by a separatory funnel. The sugar content in the aqueous phase is determined by high performance liquid chromatography; the dissolved lignin in the organic phase is precipitated by acid precipitation with a pH 2 HCL solution to obtain lignin.

[0034] Example 4

[0035] 1) After removing the non-structural components, the corn stalks are crushed and passed through a 40-mesh sieve, placed in an oven and dried for use at any time.

[0036] 2) Take 1g of raw material, add 20g of reaction solvent, the solvent is a mixed system consisting of 2g of ionic liquid and 18g of amyl alcohol aqueous solution (60%wt). After mixing evenly, heat to 140℃ for 30min; after the reaction is completed, separate the solid and liquid, wash the solid with ethanol and water several times, and measure the components after drying. Among them, the cellulose retention rate is 93.2%, the hemicellulose removal rate is 84.3%, and the lignin removal rate is 73.1%.

[0037] 3) Take 0.2 g of the solid matrix dried in step 2) above, add it to 10 ml of citric acid buffer at about pH 4.8, add 7.2 mg / g cellulase, place it in a 50°C shaker for enzymatic hydrolysis at 180 rpm, and measure the sugar content at regular intervals. The enzymatic hydrolysis cycle is 72 h.

[0038] 4) The pretreated liquid after the reaction in the above step 2) is separated into an upper organic phase and a lower aqueous phase by a separatory funnel. The sugar content in the aqueous phase is determined by high performance liquid chromatography; the dissolved lignin in the organic phase is precipitated by acid precipitation with a pH 2 HCL solution to obtain lignin.

[0039] Example 5

[0040] 1) After removing the non-structural components, the corn stalks are crushed and passed through a 40-mesh sieve, placed in an oven and dried for use at any time.

[0041] 2) Take 1g of raw material, add 20g of reaction solvent, the solvent is a mixed system consisting of 2g of ionic liquid and 18g of amyl alcohol aqueous solution (60%wt). After mixing evenly, heat to 140℃ for 90min; after the reaction is completed, separate the solid and liquid, wash the solid with ethanol and water for many times, and measure the components after drying. Among them, the cellulose retention rate is 90.5%, the hemicellulose removal rate is 91.1%, and the lignin removal rate is 83.8%.

[0042] 3) Take 0.2 g of the solid matrix dried in step 2) above, add it to 10 ml of citric acid buffer at about pH 4.8, add 7.2 mg / g cellulase, place it in a 50°C shaker for enzymatic hydrolysis at 180 rpm, and measure the sugar content at regular intervals. The enzymatic hydrolysis cycle is 72 h.

[0043] 4) The pretreated liquid after the reaction in the above step 2) is separated into an upper organic phase and a lower aqueous phase by a separatory funnel. The sugar content in the aqueous phase is determined by high performance liquid chromatography; the dissolved lignin in the organic phase is precipitated by acid precipitation with a pH 2 HCL solution to obtain lignin.

[0044] Example 6

[0045] 1) After removing the non-structural components, the corn stalks are crushed and passed through a 40-mesh sieve, placed in an oven and dried for use at any time.

[0046] 2) Take 1g of raw material, add 20g of reaction solvent, the solvent is a mixed system consisting of 1g of ionic liquid and 19g of amyl alcohol aqueous solution (60%wt). After mixing evenly, heat to 140°C for 60min; after the reaction is completed, separate the solid and liquid, wash the solid with ethanol and water for multiple times, and measure the components after drying. Among them, the cellulose retention rate is 100.0%, the hemicellulose removal rate is 77.9%, and the lignin removal rate is 79.1%.

[0047] 3) Take 0.2 g of the solid matrix dried in step 2) above, add it to 10 ml of citric acid buffer at about pH 4.8, add 7.2 mg / g cellulase, place it in a 50°C shaker for enzymatic hydrolysis at 180 rpm, and measure the sugar content at regular intervals. The enzymatic hydrolysis cycle is 72 h.

[0048] 4) The pretreated liquid after the reaction in the above step 2) is separated into an upper organic phase and a lower aqueous phase by a separatory funnel. The sugar content in the aqueous phase is determined by high performance liquid chromatography; the dissolved lignin in the organic phase is precipitated by acid precipitation with a pH 2 HCL solution to obtain lignin.

[0049] Example 7

[0050] 1) After removing the non-structural components, the corn stalks are crushed and passed through a 40-mesh sieve, placed in an oven and dried for use at any time.

[0051] 2) Take 1g of raw material, add 20g of reaction solvent, the solvent is a mixed system consisting of 4g of ionic liquid and 15g of amyl alcohol aqueous solution (60%wt). After mixing evenly, heat to 140℃ for 60min; after the reaction is completed, separate the solid and liquid, wash the solid with ethanol and water for many times, and measure the components after drying. Among them, the cellulose retention rate is 88.5%, the hemicellulose removal rate is 93.7%, and the lignin removal rate is 79.9%.

[0052] 5) Take 0.2 g of the solid matrix dried in step 2) above, add it to 10 ml of citric acid buffer at about pH 4.8, add 7.2 mg / g cellulase, place it in a 50°C shaker for enzymatic hydrolysis at 180 rpm, and measure the sugar content at regular intervals. The enzymatic hydrolysis cycle is 72 h.

[0053] 6) The pretreated liquid after the reaction in the above step 2) is separated into an upper organic phase and a lower aqueous phase by a separatory funnel. The sugar content in the aqueous phase is determined by high performance liquid chromatography; the dissolved lignin in the organic phase is precipitated by acid precipitation with a pH 2 HCL solution to obtain lignin.

[0054] Example 8

[0055] 1) After removing the non-structural components, the corn stalks are crushed and passed through a 40-mesh sieve, placed in an oven and dried for use at any time.

[0056] 2) Take 1g of raw material, add 20g of reaction solvent, the solvent is a mixed system consisting of 6g of ionic liquid and 14g of amyl alcohol aqueous solution (60%wt). After mixing evenly, heat to 140℃ for 60min; after the reaction is completed, separate the solid and liquid, wash the solid with ethanol and water for many times, and measure the components after drying. Among them, the cellulose retention rate is 64.5%, the hemicellulose removal rate is 93.0%, and the lignin removal rate is 79.9%.

[0057] 3) Take 0.2 g of the solid matrix dried in step 2) above, add it to 10 ml of citric acid buffer at about pH 4.8, add 7.2 mg / g cellulase, place it in a 50°C shaker for enzymatic hydrolysis at 180 rpm, and measure the sugar content at regular intervals. The enzymatic hydrolysis cycle is 72 h.

[0058] 4) The pretreated liquid after the reaction in the above step 2) is separated into an upper organic phase and a lower aqueous phase by a separatory funnel. The sugar content in the aqueous phase is determined by high performance liquid chromatography; the dissolved lignin in the organic phase is precipitated by acid precipitation with a pH 2 HCL solution to obtain lignin.

[0059] Example 9

[0060] 1) After removing the non-structural components, the corn stalks are crushed and passed through a 40-mesh sieve, placed in an oven and dried for use at any time.

[0061] 2) Take 1g of raw material, add 20g of reaction solvent, the solvent is a mixed system consisting of 2g of ionic liquid and 18g of amyl alcohol aqueous solution (20%wt). After mixing evenly, heat to 140℃ for 60min; after the reaction is completed, separate the solid and liquid, wash the solid with ethanol and water for many times, and measure the components after drying. Among them, the cellulose retention rate is 96.4%, the hemicellulose removal rate is 86.4%, and the lignin removal rate is 76.1%.

[0062] 3) Take 0.2 g of the solid matrix dried in step 2) above, add it to 10 ml of citric acid buffer at about pH 4.8, add 7.2 mg / g cellulase, place it in a 50°C shaker for enzymatic hydrolysis at 180 rpm, and measure the sugar content at regular intervals. The enzymatic hydrolysis cycle is 72 h.

[0063] 4) The pretreated liquid after the reaction in the above step 2) is separated into an upper organic phase and a lower aqueous phase by a separatory funnel. The sugar content in the aqueous phase is determined by high performance liquid chromatography; the dissolved lignin in the organic phase is precipitated by acid precipitation with a pH 2 HCL solution to obtain lignin.

[0064] Example 10

[0065] 1) After removing the non-structural components, the corn stalks are crushed and passed through a 40-mesh sieve, placed in an oven and dried for use at any time.

[0066] 2) Take 1g of raw material, add 20g of reaction solvent, the solvent is a mixed system consisting of 2g of ionic liquid and 18g of amyl alcohol aqueous solution (40%wt). After mixing evenly, heat to 140℃ for 60min; after the reaction is completed, separate the solid and liquid, wash the solid with ethanol and water for many times, and measure the components after drying. Among them, the cellulose retention rate is 93.4%, the hemicellulose removal rate is 87.7%, and the lignin removal rate is 81.0%.

[0067] 3) Take 0.2 g of the solid matrix dried in step 2) above, add it to 10 ml of citric acid buffer at about pH 4.8, add 7.2 mg / g cellulase, place it in a 50°C shaker for enzymatic hydrolysis at 180 rpm, and measure the sugar content at regular intervals. The enzymatic hydrolysis cycle is 72 h.

[0068] 4) The pretreated liquid after the reaction in the above step 2) is separated into an upper organic phase and a lower aqueous phase by a separatory funnel. The sugar content in the aqueous phase is determined by high performance liquid chromatography; the dissolved lignin in the organic phase is precipitated by acid precipitation with a pH 2 HCL solution to obtain lignin.

[0069] Embodiment 11

[0070] 1) After removing the non-structural components, the corn stalks are crushed and passed through a 40-mesh sieve, placed in an oven and dried for use at any time.

[0071] 2) Take 1g of raw material, add 20g of reaction solvent, the solvent is a mixed system consisting of 2g of ionic liquid and 18g of amyl alcohol aqueous solution (80%wt). After mixing evenly, heat to 140°C for 60min; after the reaction is completed, separate the solid and liquid, wash the solid with ethanol and water for multiple times, and measure the components after drying. Among them, the cellulose retention rate is 87.3%, the hemicellulose removal rate is 89.3%, and the lignin removal rate is 88.3%.

[0072] 3) Take 0.2 g of the solid matrix dried in step 2) above, add it to 10 ml of citric acid buffer at about pH 4.8, add 7.2 mg / g cellulase, place it in a 50°C shaker for enzymatic hydrolysis at 180 rpm, and measure the sugar content at regular intervals. The enzymatic hydrolysis cycle is 72 h.

[0073] 4) The pretreated liquid after the reaction in the above step 2) is separated into an upper organic phase and a lower aqueous phase by a separatory funnel. The sugar content in the aqueous phase is determined by high performance liquid chromatography; the dissolved lignin in the organic phase is precipitated by acid precipitation with a pH 2 HCL solution to obtain lignin.

[0074] Although the present invention is described in detail through the above embodiments, the present invention is not limited to the above detailed methods, that is, it does not mean that the present invention must rely on the above detailed methods to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for directional fractionation of lignocellulosic biomass components and improving enzymatic hydrolysis performance by using ionic liquid-assisted organic solvent aqueous solution two-phase system pretreatment, characterized in that: The following steps are involved: 1) Pretreatment of lignocellulosic biomass raw materials: The lignocellulosic raw materials were treated with a neutral detergent to remove non-structural components, crushed through a 40-mesh sieve and dried in a 60° C. oven to constant weight for later use. 2) Ionic liquid [BHEM] mesy assisted organic solvent biphasic pretreatment: The raw material is mixed with the ionic liquid organic solvent system for pretreatment; after the pretreatment, the solid and liquid are separated. The solid is repeatedly washed and dried with hot water and ethanol and then used for enzymatic hydrolysis, and the filtrate is directly refrigerated and stored for subsequent hemicellulose and lignin extraction. 3) Enzymatic hydrolysis to produce sugar: The solid matrix dried in the above step 2) is mixed with a buffer solution at a concentration of 2-30% (w / v), and hydrolyzed with cellulase to obtain a sugar solution. 4) Extraction of hemicellulose and lignin: The aqueous phase and organic phase in the filtrate obtained by pretreatment are separated by a separatory funnel. For the aqueous phase, i.e., the aqueous solution of hemicellulose derivatives, a sugar solution of target concentration can be obtained by rotary evaporation concentration; for the organic phase, i.e., the lignin dissolved therein, a lignin precipitate can be obtained by acid precipitation method.

2. The method according to claim 1, characterized in that The lignocellulosic biomass in step 1) includes cellulose-rich raw materials such as corn stalks, sugarcane bagasse, rice straw, wheat straw, cotton stalks, etc.

3. The method according to claim 1, wherein the ionic liquid in step 2) is N-methyldiethanolamine methanesulfonate, and the organic solvent biphasic system refers to organic solvent aqueous solutions of different concentrations, including amyl alcohol, butanol, phenoxyethanol, methyl isobutyl ketone and 2-methyltetrahydrofuran. The mass ratio of the ionic liquid to the organic solvent aqueous solution is 1:99-99:

1.

4. The method according to claim 1, wherein the pretreatment process temperature in step 2) is 100°C-160°C, and the insulation time is 10min-120min.

5. The method according to claim 1, wherein the enzymatic hydrolyzed sugar solution in step 3) has the following characteristics: the amount of enzyme protein added is 1-20 mg / g, and the enzymatic hydrolysis rate is 50-99%.

6. The method according to claim 1, wherein the filtrate described in step 4) has the following characteristics: a high concentration of sugar and a low concentration of inhibitor in the aqueous phase, 70.8%wt of hemicellulose converted into xylose and xylan in the aqueous phase; a dissolved lignin solution in the organic phase, the lignin obtained by acid precipitation is dark brown in color and has a wide molecular weight distribution.

Images