CN115976116A - Green and efficient biomass pretreatment method - Google Patents

Abstract

The invention discloses a green and efficient biomass pretreatment method, which comprises the steps of soaking biomass fragments in water to obtain wet biomass fragments, carrying out steam explosion treatment on the wet biomass fragments to obtain biomass residues, adding the biomass residues into a eutectic solvent, reacting, and collecting solid residues; the eutectic solvent is a mixed solvent consisting of choline chloride and formic acid. According to the invention, steam explosion and the eutectic solvent are coupled, and the lignocellulose-containing biomass is pretreated under mild conditions, so that lignin and hemicellulose can be efficiently removed, a cellulose product with high purity and less loss is produced, wherein the structure and the composition of the cellulose are not greatly changed, and the method can be applied to the field of production of various large celluloses.

Description

A Green and Efficient Biomass Pretreatment Method

technical field

The invention belongs to the technical field of biomass pretreatment, and in particular relates to a green and efficient biomass pretreatment method.

Background technique

With the excessive consumption of fossil resources and the inevitable trend of sustainable development, the concept of actively developing and applying environmentally friendly renewable resources has become a consensus, and industrial chemicals developed based on biomass have attracted the active attention of researchers. Lignocellulose has the advantages of wide sources and abundant reserves. As the most potential renewable biomass resource, it can be effectively transformed into various fossil resource substitutes for use in various fields. For example, by making the separated and purified lignin into nano-lignin and various functional materials, cellulose can be produced into bioethanol through enzymatic fermentation or catalytic conversion into ethylene glycol, and hemicellulose products can be the best for furfural production. raw material.

However, lignocellulosic biomass is composed of hemicellulose, cellulose, lignin and a small amount of ash, and is the main component of plant cell walls. Interaction forces combine to form a complex three-dimensional structure (anti-depolymerization barrier), making lignocellulose difficult to transform and utilize. If biomass is directly used as raw material, not only the process cost is high, the product is likely to be complex and changeable, but also most of the cellulose will be lost, so today's industrial production often requires pretreatment of lignocellulosic biomass for subsequent conversion use. Conventional pretreatment uses acid treatment, alkali treatment, ionic liquid treatment, physical treatment, hydrothermal method, deep eutectic solvent treatment and so on. Among them, the acid-base treatment corrodes the equipment, causing additional environmental pollution and the treatment solvent is not easy to recover. The cost of the ionic liquid treatment method is high, the efficiency of the physical method is low, and the hydrothermal method requires high temperature and high pressure and has high requirements on equipment. The deep eutectic solvent has a long treatment time but is easy to solvent recovery, but usually the solvent system is complex, the reaction conditions are harsh, and the damage to the equipment is large, such as a biomass pretreatment agent in the patent (CN115261219A), which is an organic acid-based low-eutectic Melt solvent, it comprises organic acid, choline chloride and Lewis acid, and the Lewis acid used comprises one or more in aluminum chloride, ferric chloride and manganese chloride, wherein the excess chloride ion in Lewis acid The equipment is greatly damaged, and there are defects such as the inhibition of cellulase activity by metal ions at the same time. In addition, the residue yield is only about 44%, and the yield is low.

Contents of the invention

Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a green and efficient biomass pretreatment method, by soaking wood waste, steam explosion, and deep eutectic solvent pretreatment. It can remove most of the lignin and obtain high-quality raw materials with high cellulose retention rate for biomass energy production. Some simplifications or omissions may be made in this section, as well as in the abstract and titles of this application, to avoid obscuring the purpose of this section, the abstract and titles, and such simplifications or omissions should not be used to limit the scope of the invention.

In order to solve the problems of the technologies described above, the present invention adopts the following technical solutions:

The invention provides a green and efficient biomass pretreatment method. The biomass debris is soaked in water to obtain wet biomass debris, and the wet biomass debris is subjected to steam explosion treatment to obtain biomass residue. The eutectic solvent is reacted and the solid residue is collected; the eutectic solvent is a mixed solvent composed of choline chloride and formic acid.

The pretreatment method of the present invention adopts steam explosion and deep eutectic solvent to carry out synergistic treatment, first adopts steam explosion, feeds high-pressure steam and releases pressure rapidly, can promote poplar wood hemicellulose to degrade into monosaccharide, cellulose expansion fracture, change Cellulose crystallinity and induction of partial lignin conversion, resulting in the destruction of the dense three-dimensional network structure of the biomass, and then using a deep eutectic solvent to treat the blasting residues, destroying the β-O-4 linkages between the lignins, and the wood Linkages such as benzyl ether bonds between prime and hemicellulose. Because the cohesive energy of cellulose is too strong, the hydrogen bond strength in the deep eutectic solvent (DES) is weaker than the force between cellulose, and cannot be dissociated in the DES system, so DES can selectively separate lignin and cellulose.

In the present invention, only the mixed solvent composed of choline chloride and formic acid is used as the deep eutectic solvent, which can achieve excellent pretreatment effect and obtain a yield much higher than that of the prior art.

The invention couples the steam explosion with the deep eutectic solvent, pretreats the biomass containing lignocellulose under mild conditions, can efficiently remove lignin and hemicellulose, and produce cellulose products with high purity and less loss , in which the structure and composition of cellulose have not changed significantly, and can be applied to various cellulose production fields.

Further, the particle size of the biomass chips is 4-10 mesh.

Further, the time for soaking the biomass chips in water is 12-24 hours.

Further, the pressure of the steam explosion treatment is 1.6-1.8 MPa, and the pressure maintenance time is 180-240s.

In the present invention, the pressure of the steam explosion treatment is controlled within the above range, and finally the synergistic treatment effect with DES is optimal, and if the pressure of the steam explosion is too high, the excessive hydrolysis of hemicellulose will be caused, resulting in 5- Harmful substances such as hydroxymethylfurfural, and severe blasting conditions will destroy the crystallization area of cellulose, which is not conducive to the production of some cellulose-based functional materials. During actual operation, wet biomass chips are placed in a steam explosion machine for processing.

Further, the wet biomass debris is subjected to steam explosion treatment to obtain a biomass residue after drying in a natural environment.

Further, in the deep eutectic solvent, the molar ratio of choline chloride to formic acid is 1:1.8-2.5.

In the present invention, the deep eutectic solvent chooses choline chloride as the hydrogen bond acceptor, and formic acid as the hydrogen bond donor. The optimal effect can be achieved by the mutual matching of choline.

Furthermore, the method for obtaining the deep eutectic solvent is: reacting choline chloride and formic acid at 75-85° C. for 1.5-2 hours until a transparent uniform solution is formed.

Further, the solid-to-liquid mass volume ratio of the biomass residue to the deep eutectic solvent is 1g:10-20mL.

Further, the reaction temperature is 100-120°C, and the reaction time is 2-4h.

By adopting the deep eutectic solvent of the present invention, an excellent pretreatment effect can be obtained at a lower temperature.

Further, after the reaction is completed, vacuum filtration is used to separate the solid and liquid of the reaction mixture, the obtained solid phase is washed with ethanol aqueous solution until neutral, and the solid residue is collected; that is, the separated and purified cellulose product.

Furthermore, the aqueous ethanol solution is a mixed solution prepared from ethanol and ultrapure water at a volume ratio of 1:1-1.5.

Beneficial effect

The present invention optimizes the existing biomass pretreatment technology, avoids excessive pulverization of biomass waste in the whole process, reduces the requirements for biomass raw materials, has mild reaction conditions, short production cycle, high efficiency, and significantly high yield Compared with the existing treatment technology, in addition, the water immersion treatment of biomass raw materials before blasting has already satisfied the removal effect of hemicellulose after blasting, and there is no need to use dilute acid or dilute alkali to reduce environmental pollution and equipment corrosion. The use of metal ions avoids the disadvantages of cellulase activity inhibition.

Since the biomass material with a larger particle size is used as the raw material, the processing difficulty is reduced, and the raw material can make full use of wood processing scraps and waste materials.

The green and high-efficiency biomass pretreatment method provided by the present invention can effectively improve the utilization efficiency of each component of lignocellulose by separating lignocellulose, and produce cleaner and more environmentally friendly green chemicals.

The invention optimizes the wood processing technology, reduces the particle size requirements of biomass raw materials, can make full use of waste wood, and has mild reaction conditions in the whole preparation process, and the deep eutectic solvent can be recycled. The process is simple and easy to scale, and the requirements for equipment and materials Low.

Description of drawings

Figure 1: Comparison of the contents of lignocellulose components before and after pretreatment,

Figure 2: Comparison chart of cellulose retention rate, hemicellulose removal rate and lignin removal rate before and after pretreatment,

Figure 3: Effect of pressure maintenance time on the content of lignocellulose components in steam explosion,

Figure 4: The effect of explosion pressure on the content of lignocellulose components in steam explosion,

Figure 5: Effect of treatment temperature on the content of lignocellulose components in deep eutectic solvent,

Figure 6: Effect of treatment time in deep eutectic solvent on the content of each component of lignocellulose.

Detailed ways

The specific embodiment of the present invention will be described in detail below through specific examples. The given examples are only used to explain the present invention, not to limit the scope of the present invention. All raw materials used in the examples are commercially available or prepared by conventional methods.

The content of cellulose, hemicellulose and lignin in the poplar raw material and pretreated poplar residue was determined by the analytical method of the National Renewable Energy Laboratory (NREL), and the cellulose retention rate and hemicellulose removal rate and The lignin removal rate, the specific calculation formula is as follows:

In the formula: M is the product yield after pretreatment, m ₀ and m ₁ are the solid mass (g) before and after pretreatment respectively; C ₁ , H ₁ and L ₁ are the contents of cellulose, hemicellulose and lignin in the raw material ( %); C ₂ , H ₂ and L ₂ are the contents of cellulose, hemicellulose and lignin in poplar residue after pretreatment (%).

Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

Example 1:

Green and efficient biomass pretreatment method:

1) Steam explosion treatment: After immersing 4-6 mesh biomass debris in water for 24 hours, place them in a steam explosion machine for treatment, with a blasting pressure of 1.6MPa and a pressure maintenance time of 180s. Collect the blasting residue and dry it in the natural environment;

2) Preparation of deep eutectic solvent: react choline chloride and formic acid at 80° C. for 2 hours until a transparent homogeneous solution is formed.

3) Deep eutectic solvent pretreatment: add a deep eutectic solvent to the dried biomass residue at a solid-to-liquid ratio of 1:20 (g/ml), and bathe in oil at 120°C for 2 hours;

4) Washing: Use vacuum filtration to separate the solid-liquid mixture after the pretreatment reaction, wash the solid residue with ethanol aqueous solution (v:v=1:1) until it is neutral, and collect the solid residue, which is the separation and purification of cellulose products.

Among the solid residues obtained after pretreatment, the residue yield was 62.74%, the cellulose content was 75.97%, the hemicellulose and lignin removal rates were 75.77%, 86.94%, and the cellulose retention rate was 96.67%.

Example 2:

Green and efficient biomass pretreatment method:

1) Steam explosion treatment: After immersing 4-6 mesh biomass debris in water for 24 hours, place them in a steam explosion machine for treatment, with a blasting pressure of 1.6MPa and a pressure maintenance time of 180s. Collect the blasting residue and dry it in the natural environment;

2) Preparation of deep eutectic solvent: react choline chloride and formic acid at 80° C. for 2 hours until a transparent homogeneous solution is formed.

3) Deep eutectic solvent pretreatment: add a deep eutectic solvent to the dried biomass residue at a solid-to-liquid ratio of 1:20 (g/ml), and bathe in oil at 120°C for 4 hours;

4) Washing: Use vacuum filtration to separate the solid-liquid mixture after the pretreatment reaction, wash the solid residue with ethanol aqueous solution (v:v=1:1) until it is neutral, and collect the solid residue, which is the separation and purification of cellulose products.

In the solid residue obtained after pretreatment, the residue yield was 55.00%, the cellulose content was 81.35%, the hemicellulose and lignin removal rates were 83.50%, 85.47%, and the cellulose retention rate was 90.75%.

Comparative example 1:

Green and efficient biomass pretreatment method:

1) Simple soaking treatment: soak 4-6 mesh biomass debris in water for 24 hours, then dry in natural environment;

2) Preparation of deep eutectic solvent: react choline chloride and formic acid at 80° C. for 2 hours until a transparent homogeneous solution is formed.

3) Deep eutectic solvent pretreatment: add a deep eutectic solvent to the dried biomass residue at a solid-to-liquid ratio of 1:20 (g/ml), and bathe in oil at 120°C for 4 hours;

4) Washing: Use vacuum filtration to separate the solid-liquid mixture after the pretreatment reaction, wash the solid residue with ethanol aqueous solution (v:v=1:1) until it is neutral, and collect the solid residue, which is the separation and purification of cellulose products.

In the solid residue obtained after pretreatment, the residue yield was 40.98%, the cellulose content was 86.48%, the hemicellulose and lignin removal rates were 95.69%, 95.09%, and the cellulose retention rate was 71.88%; it can be seen that Although most of the hemicellulose and lignin can be removed without blasting treatment, due to the chemical bonding of the various components of lignocellulose, most of the cellulose is also hydrolyzed, resulting in a large loss.

Comparative example 2:

Green and efficient biomass pretreatment method:

1) Steam explosion treatment: After immersing 4-6 mesh biomass debris in water for 24 hours, place them in a steam explosion machine for treatment, with a blasting pressure of 1.6MPa and a pressure maintenance time of 180s. Collect blasting residue;

2) Washing: Use vacuum filtration to separate solid and liquid from the blasting residue, wash the solid residue with ethanol aqueous solution (v:v=1:1) until neutral, collect the solid residue, which is the separated and purified cellulose product .

Among the solid residues obtained after pretreatment, the residue yield was 90.00%, the cellulose content was 47.19%, the hemicellulose and lignin removal rates were 21.82%, 4.96%, and the cellulose retention rate was 86.03%;

Steam explosion treatment can only effectively destroy the fiber structure, but cannot achieve efficient separation of lignocellulose. During this process, due to the high temperature and high pressure of steam explosion, the hemicellulose is hydrolyzed, which destroys the compact structure of lignocellulose, and further treatment is required to achieve efficient separation of lignocellulose components.

Comparative example 3:

Green and efficient biomass pretreatment method:

1) Steam explosion treatment: After immersing the 4-6 mesh biomass debris in water for 24 hours, put them in a steam explosion machine for treatment, the explosion pressure is 1.8MPa, and the pressure maintenance time is 180s. Collect the blasting residue and dry it in the natural environment;

2) Preparation of deep eutectic solvent: react choline chloride and formic acid at 80° C. for 2 hours until a transparent homogeneous solution is formed.

3) Deep eutectic solvent pretreatment: add a deep eutectic solvent to the dried biomass residue at a solid-to-liquid ratio of 1:20 (g/ml), and bathe in oil at 120°C for 4 hours;

4) Washing: Use vacuum filtration to separate the solid-liquid mixture after the pretreatment reaction, wash the solid residue with ethanol aqueous solution (v:v=1:1) until it is neutral, and collect the solid residue, which is the separation and purification of cellulose products.

Among the solid residues obtained after pretreatment, the residue yield was 49.42%, the cellulose content was 79.63%, the hemicellulose and lignin removal rates were 86.42%, 85.13%, and the cellulose retention rate was 79.81%;

It can be seen that too severe steam explosion conditions not only increase energy consumption and danger, but also lose part of the cellulose and reduce the utilization rate of cellulose.

Comparative example 4:

Green and efficient biomass pretreatment method:

1) Steam explosion treatment: After immersing 4-6 mesh biomass debris in water for 24 hours, place them in a steam explosion machine for treatment. The explosion pressure is 1.6MPa, and the pressure maintenance time is 300s. Collect the blasting residue and dry it in the natural environment;

2) Preparation of deep eutectic solvent: react choline chloride and formic acid at 80° C. for 2 hours until a transparent homogeneous solution is formed.

3) Deep eutectic solvent pretreatment: add a deep eutectic solvent to the dried biomass residue at a solid-to-liquid ratio of 1:20 (g/ml), and bathe in oil at 120°C for 4 hours;

4) Washing: Use vacuum filtration to separate the solid-liquid mixture after the pretreatment reaction, wash the solid residue with ethanol aqueous solution (v:v=1:1) until it is neutral, and collect the solid residue, which is the separation and purification of cellulose products.

Among the solid residues obtained after pretreatment, the residue yield was 54.61%, the cellulose content was 73.41%, the hemicellulose and lignin removal rates were 71.85%, 75.55%, and the cellulose retention rate was 81.31%;

Prolonging the pressure maintaining time can effectively enhance the separation effect of the deep eutectic solvent, but too long pressure maintaining time will cause serious damage to the amorphous region of cellulose, resulting in a decrease in the yield and purity of cellulose.

Comparative example 5:

Green and efficient biomass pretreatment method:

1) Steam explosion treatment: After immersing 4-6 mesh biomass debris in water for 24 hours, place them in a steam explosion machine for treatment, with a blasting pressure of 1.6MPa and a pressure maintenance time of 180s. Collect the blasting residue and dry it in the natural environment;

2) Preparation of deep eutectic solvent: react choline chloride and formic acid at 80° C. for 2 hours until a transparent homogeneous solution is formed.

3) Deep eutectic solvent pretreatment: add a deep eutectic solvent to the dried biomass residue at a solid-to-liquid ratio of 1:20 (g/ml), and bathe in oil at 100°C and 140°C for 4 hours, respectively;

4) Washing: Use vacuum filtration to separate the solid-liquid mixture after the pretreatment reaction, wash the solid residue with ethanol aqueous solution (v:v=1:1) until it is neutral, and collect the solid residue, which is the separation and purification of cellulose products.

Among the solid residues obtained after pretreatment at 100°C, the residue yield was 57.96%, the cellulose content was 70.85%, the hemicellulose and lignin removal rates were 67.95%, 70.78%, and the cellulose retention rate was 83.29%. The cellulose content in the cellulose raw material obtained after pretreatment at 140°C is 85.33%, the product yield is 41.74%, the hemicellulose and lignin removal rates are 90.75% and 92.98%, respectively, and the cellulose retention rate is 72.23% %;

It can be seen that appropriate temperature conditions can effectively exert the removal effect of deep eutectic solvent, but too low temperature cannot effectively remove lignin and hemicellulose, so that the content of cellulose products after pretreatment is low; Temperature will seriously affect the product yield after pretreatment, making the yield of cellulose products greatly reduced.

Comparative example 6:

Green and efficient biomass pretreatment method:

1) Steam explosion treatment: After immersing the 4-6 mesh biomass debris in water for 24 hours, place them in a steam explosion machine for treatment, the explosion pressure is 1.6MPa, and the pressure maintenance time is 180s. Collect the blasting residue and dry it in the natural environment;

2) Preparation of deep eutectic solvent: react choline chloride and acetic acid at 80° C. for 2 hours until a transparent homogeneous solution is formed.

3) Deep eutectic solvent pretreatment: add a deep eutectic solvent to the dried biomass residue at a solid-to-liquid ratio of 1:20 (g/ml), and bathe in oil at 100°C and 140°C for 4 hours, respectively;

4) Washing: Use vacuum filtration to separate the solid-liquid mixture after the pretreatment reaction, wash the solid residue with ethanol aqueous solution (v:v=1:1) until it is neutral, and collect the solid residue, which is the separation and purification of cellulose products.

In the solid residue obtained after pretreatment, the residue yield was 60.21%, the cellulose content was 62.84%, the hemicellulose and lignin removal rates were 55.05%, 59.49%, and the cellulose retention rate was 76.74%;

When choline chloride and acetic acid were used as deep eutectic solvents, the removal effect on hemicellulose and lignin was not good.

The above-mentioned embodiments merely illustrate several embodiments of the present invention and are not limiting. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these all belong to the protection scope of the present invention.

The technical features involved in the above-mentioned embodiments can be combined arbitrarily. This specification only selects a few specific combinations for description, and does not describe all possible combinations of the technical features in the above-mentioned embodiments. It is intended to be more concise Explain the principle and practical application of the invention. However, as long as there is no contradiction in the combination of these technical features, it should be considered as within the scope of the description.

Claims (10)

1. A green and efficient biomass pretreatment method is characterized by comprising the following steps: soaking the biomass fragments in water to obtain wet biomass fragments, performing steam explosion treatment on the wet biomass fragments to obtain biomass residues, adding the biomass residues into a eutectic solvent, reacting, and collecting solid residues; the eutectic solvent is a mixed solvent consisting of choline chloride and formic acid.

2. The green and efficient biomass pretreatment method according to claim 1, wherein: the particle size of the biomass crumbs is 4-10 meshes.

3. The green and efficient biomass pretreatment method according to claim 1, characterized by comprising the following steps: the time for soaking the biomass scraps in water is 12-24h.

4. The green and efficient biomass pretreatment method according to claim 1, characterized by comprising the following steps: the pressure of the steam explosion treatment is 1.6-1.8MPa, and the pressure maintaining time is 180-240s.

5. The green and efficient biomass pretreatment method according to claim 1 or 4, characterized in that: and (3) carrying out steam explosion treatment on the wet biomass chips to obtain a product, and airing the product in the natural environment to obtain biomass residues.

6. The green and efficient biomass pretreatment method according to claim 1, characterized by comprising the following steps: in the eutectic solvent, the molar ratio of choline chloride to formic acid is 1.8-2.5.

7. The green and efficient biomass pretreatment method according to claim 1 or 6, wherein: the method for obtaining the eutectic solvent comprises the following steps: choline chloride is reacted with formic acid at 75-85 ℃ for 1.5-2h until a clear homogeneous solution is formed.

8. The green and efficient biomass pretreatment method according to claim 1 or 6, characterized in that: the solid-liquid mass volume ratio of the biomass residue to the eutectic solvent is 1g.

9. The green and efficient biomass pretreatment method according to claim 1 or 6, characterized in that: the reaction temperature is 100-120 ℃, and the reaction time is 2-4h.

10. The green and efficient biomass pretreatment method according to claim 1 or 6, wherein: after the reaction is finished, performing vacuum filtration to separate the solid from the liquid of the mixture obtained by the reaction, washing the obtained solid phase to be neutral by adopting ethanol water solution, and collecting solid residues; namely the separated and purified cellulose product.

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