Biomass modification method

Abstract

The invention belongs to the technical field of biomass pretreatment, and discloses a biomass modification method. The modification method comprises the following steps: mixing a water-based oxidant solution with a biomass material to obtain a premix; and carrying out flash explosion treatment on the premix by using a continuous flash explosion device to obtain the oxidized modified biomass material. According to the biomass modification method provided by the invention, chemical modification can be simultaneously carried out in a continuous flash explosion process, and the specific surface area of the biomass is greatly increased by utilizing flash explosion while the biomass is chemically modified. Moreover, the modification method provided by the invention can be used for multiple times of flash explosion and multiple times of modification, and control of different reaction stages and control of different modification directions are realized by changing the variety and content of the oxidizing agent.

Description

Technical Field

[0001] The invention relates to the technical field of biomass pretreatment, and in particular to a biomass modification method. Background Art

[0002] Plant fiber is the most abundant renewable biological resource on earth. After biomass conversion and other processing, it can provide fuel, chemical products, etc. for human daily life. However, due to the complexity of the structure and chemical composition of different plant fibers, as well as the recalcitrant nature of biomass itself to the external environment, the utilization of plant fibers has become very difficult. Factors such as the crystallinity and degree of polymerization of cellulose, the accessibility of plant fibers, the barrier of lignin to cellulose, and the coating of cellulose by hemicellulose will all affect the strength of the recalcitrant nature of plant fibers to the external environment. In order to achieve high-value utilization of biomass, it is necessary to pretreat the biomass. The main purpose of pretreatment is to change the composition, macroscopic and microscopic structure of plant fibers, while also improving the biodegradability of natural plant fiber polymers.

[0003] Among the existing methods, biomass pretreatment is roughly divided into several methods: physical crushing and rolling method, acid-base treatment method, ionic liquid treatment method, organic solvent treatment method, oxidation treatment method, biological enzymatic hydrolysis method, flash explosion pretreatment method (flash explosion method) and the like.

[0004] Taking the oxidation treatment method as an example, biomass oxidation modification is a modification method that uses an oxidant to oxidize the biomass molecular structure into a structure containing carbonyl, carboxyl, etc., which can make the biomass material have more and stronger reactive groups. For example, XM Fan et al. (XM Fan, HY Yu, et al. Facile and Green Synthesis of Carboxylated Cellulose Nanocrystals as Efficient Adsorbents in Wastewater Treatments [J]. ACSSustainable Chemistry & Engineering, 2019, 7 (21)) proposed a simple and environmentally friendly Fe 2+ / H2O2 oxidation of microcrystalline cellulose (MCCs) to prepare cellulose nanocrystals (CNCs) with a high carboxylation content. For another example, R.Batmaz et al. (R.Batmaz, Nishil Mohammed, et al. Cellulose nanocrystals as promising adsorbents for the removal of cationic dyes [J]. Cellulose, 2014, 21) prepared cellulose nanocrystals (CNCs) by hydrolyzing cellulose fibers with sulfuric acid and used them as adsorbents to remove methylene blue (MB) from aqueous solutions. However, the above-mentioned prior art is only a chemical surface modification, which can only modify biomass materials that have been physically treated in advance, and a single chemical modification has limited improvement on the specific surface area of ​​the biomass.

[0005] Taking the flash explosion pretreatment method as an example, the flash explosion pretreatment is a hydrothermal pretreatment method that can be used for plant fiber hydrolysis and belongs to the category of physical and chemical methods. The basic process of this method is: first, the plant fiber that has been physically pretreated (grinded, crushed or otherwise preprocessed) is treated in a high-temperature, high-pressure steam environment, maintained for a period of time ranging from a few seconds to tens of minutes, and then quickly depressurized to achieve the effect of flash explosion. Generally speaking, flash explosion pretreatment is usually divided into intermittent flash explosion pretreatment and continuous flash explosion pretreatment. Among them, continuous flash explosion pretreatment is: the material prepared with a suitable moisture content is added to the equipment through a feeding device, and the heat generated by the high shear and high friction of the conical screw on the material is used to generate water vapor from the moisture in the material, and the flash explosion process is completed when the material is squeezed out of the die. For example, the utility model patent application with application number 202420080367.8 discloses a steam explosion device for fiber material processing, which can allow materials at different heights to be steamed at the same time to ensure that the steam passes through the material evenly, and can also ensure that the material temperature reaches a suitable gas explosion temperature, but the above scheme is only a single explosion treatment method. For another example, the invention patent application with application number 201810762170.1 discloses a method and equipment for continuous flash explosion and in-situ blending of biomass based on volume pulsation, which solves the problem of fiber breakage under strong shearing of the screw, improves the dispersion performance of biomass, simplifies the equipment structure, and reduces process operations. However, the above scheme is also a steam flash explosion treatment, and is only a single explosion treatment scheme. For another example, the utility model patent application with application number 201020228360.4 discloses a continuous steam explosion machine for pure physical molecular structure modification and activation of straw cellulose. It can achieve molecular-level structural modification and activation of plant cellulose by pure physical steam explosion without using chemical solution immersion treatment, and obtain the base materials of cellulose plastic, lignin pulp, and pectin sugar feed through segmented screening of air ducts. However, the above scheme is a pure physical method, and is only a single explosion treatment scheme. Therefore, the existing flash explosion pretreatment method has the problem that the single chemical modification regulation of flash explosion is limited and the continuous flash explosion process cannot control the chemical structure of the pretreated biomass. Summary of the invention

[0006] The object of the present invention is to provide a biomass modification method, which can pretreat biomass in combination with chemical modification of an oxidant during flash explosion treatment, reduce the process steps of biomass pretreatment, improve biomass pretreatment efficiency, and effectively regulate the morphology and chemical structure of biomass.

[0007] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0008] The present invention provides a biomass modification method, comprising the following steps:

[0009] (1) Premixing: mixing a water-based oxidant solution with a biomass material to obtain a premix;

[0010] (2) Flash explosion: The premix of step (1) is subjected to flash explosion treatment using a continuous flash explosion device to obtain an oxidatively modified biomass material.

[0011] Preferably, in the biomass modification method, in step (1), the water-based oxidant in the water-based oxidant solution includes one or more of hydrogen peroxide, potassium permanganate, sodium hypochlorite, calcium hypochlorite and Serat's reagent, and the concentration of the water-based oxidant solution is 1 to 50 wt%.

[0012] Preferably, in the biomass modification method, in step (1), the biomass material includes plant biomass and / or animal biomass; the plant biomass includes one or more of food in the agricultural and forestry production process, fruit in the agricultural and forestry production process, other wood cellulose in the agricultural and forestry production process, main products of agricultural product processing industry, by-products of agricultural product processing industry, waste materials of agricultural and forestry processing industry and agricultural and forestry waste; the animal biomass includes one or more of animal hair, animal feathers and animal shells.

[0013] Preferably, in the biomass modification method, in step (1), the mass of the water-based oxidant in the water-based oxidant solution is 1 to 80% of the mass of the biomass material.

[0014] Preferably, in the biomass modification method, in step (1), the moisture content of the premix is ​​20 to 80 wt %.

[0015] Preferably, in the biomass modification method, the number of flash explosion treatments in step (2) is 1 to 6 times; the conditions of each flash explosion treatment are independently: the temperature is 80 to 240° C., and the screw speed is 20 to 1000 rpm.

[0016] Preferably, in the biomass modification method, a water-based oxidant solution or biomass material is added after each flash explosion treatment.

[0017] Preferably, in the biomass modification method, after each flash explosion treatment, the mass of the water-based oxidant in the added water-based oxidant solution is 1 to 80% of the mass of the biomass material in step (1).

[0018] Preferably, in the biomass modification method, after each flash explosion treatment, the moisture content of the added biomass material is 20 to 80 wt %.

[0019] Preferably, in the biomass modification method, the oxidatively modified biomass material is post-processed, and the post-processing includes: molding the oxidatively modified biomass material, or molding the oxidatively modified biomass material after chemical modification, or mixing the oxidatively modified biomass material with a polymer to prepare a biomass composite material.

[0020] It can be seen from the above technical solution that compared with the prior art, the present invention has the following beneficial effects:

[0021] (1) The biomass modification method proposed in the present invention can achieve chemical modification during the continuous flash explosion process, and use flash explosion to greatly increase the specific surface area of ​​the biomass while chemically modifying the biomass. Compared with a single flash explosion treatment, the present invention combines a water-based oxidant oxidation treatment during the flash explosion process, increases the treatment effect of chemical oxidation during the flash explosion, reduces the process steps of the modification, and improves the modification efficiency; compared with a pure physical flash explosion treatment scheme, the modification method of the present invention improves the modification effect of the molecular structure, with higher efficiency and better effect. In addition, the modification method of the present invention can be flash exploded and modified multiple times, and the control of different reaction stages and different modification directions can be achieved by changing the type and content of the oxidant. For example, sodium hypochlorite oxidation of cellulose, starch, etc. in an acidic environment is easy to generate carbonyl groups, and sodium hypochlorite oxidation of cellulose, starch, etc. in an alkaline environment is easy to generate carboxyl groups.

[0022] (2) The present invention adopts a continuous flash explosion device for flash explosion pretreatment, which has the advantages of large output, high efficiency and low energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required to be used in the description of the embodiments or the prior art are briefly introduced below.

[0024] Figure 1 The infrared spectra of the wheat straw raw material of Example 1 and the oxidized modified wheat straw material obtained in Example 1;

[0025] Figure 2 This is a microscopic morphology of the unmodified wheat straw material of Example 2;

[0026] Figure 3 This is a microscopic morphology of the oxidatively modified wheat straw material obtained in Example 2;

[0027] Figure 4 This is the microscopic morphology of the oxidatively modified corn stalk-reed stalk blend material obtained in Example 3. DETAILED DESCRIPTION

[0028] The present invention provides a biomass modification method, comprising the following steps:

[0029] (1) Premixing: mixing a water-based oxidant solution with a biomass material to obtain a premix;

[0030] (2) Flash explosion: The premix of step (1) is subjected to flash explosion treatment using a continuous flash explosion device to obtain an oxidatively modified biomass material.

[0031] In the present invention, in step (1), the water-based oxidant in the water-based oxidant solution preferably includes one or more of hydrogen peroxide, potassium permanganate, sodium hypochlorite, calcium hypochlorite and Serrette's reagent, further preferably includes one or more of hydrogen peroxide, sodium hypochlorite and calcium hypochlorite, and more preferably includes hydrogen peroxide, sodium hypochlorite or calcium hypochlorite.

[0032] In the present invention, in step (1), the water-based oxidant solution is preferably a water-based oxidant aqueous solution.

[0033] In the present invention, in step (1), the concentration of the water-based oxidant solution is preferably 1 to 50 wt %, more preferably 12 to 30 wt %, and even more preferably 20 wt %.

[0034] In the present invention, in step (1), the biomass material preferably includes plant biomass and / or animal biomass, and more preferably includes plant biomass.

[0035] In the present invention, the plant biomass preferably includes one or more of food in the process of agricultural and forestry production, fruits in the process of agricultural and forestry production, other wood cellulose in the process of agricultural and forestry production, main products of agricultural product processing industry, by-products of agricultural product processing industry, waste materials of agricultural and forestry processing industry and agricultural and forestry waste. Specifically in the embodiments of the present invention, the source of the plant biomass includes but is not limited to wheat, rice, camphor leaves, willow branches, bamboo, ginger, wall moss, liverwort, kidney fern, bracken, kelp, green algae, lichen litmus, usnea, mistletoe, broomrape, creeper, grape, such as straw, polysaccharide, starch products, etc.

[0036] In the present invention, the animal biomass preferably includes one or more of animal hair, animal feathers and animal shells, further preferably includes animal hair, animal feathers or animal shells, and more preferably includes animal shells.

[0037] In the present invention, in step (1), the mass of the water-based oxidant in the water-based oxidant solution is preferably 1 to 80% of the mass of the biomass material, more preferably 4 to 40%, and even more preferably 10%.

[0038] In the present invention, adding a water-based oxidant solution can adjust the water content of the biomass material, thereby achieving a better mixing and dispersion effect of the water-based oxidant and the biomass material. In addition, the chemical structure of the flash explosion product can be flexibly controlled by changing the type and amount of the water-based oxidant.

[0039] In the present invention, in step (1), the moisture content of the premix is ​​preferably 20 to 80 wt %, more preferably 30 to 60 wt %, and even more preferably 40 to 50 wt %.

[0040] In the present invention, in step (2), the number of flash explosion treatments is preferably 1 to 6 times, more preferably 2 to 5 times, and even more preferably 3 to 5 times.

[0041] In the present invention, the conditions of each flash explosion treatment are independent: the temperature is preferably 80-240°C, more preferably 120-160°C, more preferably 130-140°C; the screw speed is preferably 20-1000rpm, more preferably 150-900rpm, more preferably 600-720rpm.

[0042] In the present invention, after each flash explosion treatment, it is preferred to add a water-based oxidant solution or a biomass material.

[0043] In the present invention, after each flash explosion treatment, the water-based oxidant in the added water-based oxidant solution preferably includes one or more of hydrogen peroxide, potassium permanganate, sodium hypochlorite, calcium hypochlorite and Serrette's reagent, further preferably includes one or more of hydrogen peroxide, sodium hypochlorite and calcium hypochlorite, and more preferably includes hydrogen peroxide.

[0044] In the present invention, after each flash explosion treatment, the water-based oxidant solution added is preferably a water-based oxidant aqueous solution.

[0045] In the present invention, after each flash explosion treatment, the concentration of the added water-based oxidant solution is preferably 1 to 50 wt %, more preferably 12 to 30 wt %, and even more preferably 20 wt %.

[0046] In the present invention, after each flash explosion treatment, the mass of the water-based oxidant in the added water-based oxidant solution is preferably 1 to 80% of the mass of the biomass material in step (1), more preferably 5 to 20%, and even more preferably 10%.

[0047] In the present invention, after each flash explosion treatment, the added biomass material preferably includes plant biomass and / or animal biomass, and further preferably includes plant biomass;

[0048] The plant biomass preferably includes one or more of food in the agricultural and forestry production process, fruit in the agricultural and forestry production process, other wood cellulose in the agricultural and forestry production process, main products of agricultural product processing industry, by-products of agricultural product processing industry, waste materials of agricultural and forestry processing industry and agricultural and forestry waste;

[0049] Specifically in the embodiments of the present invention, the sources of the plant biomass include but are not limited to wheat, rice, camphor leaves, willow branches, bamboo, ginger, wall moss, liverwort, kidney fern, bracken, kelp, green algae, lichen litmus, usnea, mistletoe, broomrape, creeper, grapes, such as straw, polysaccharides, starch products, etc.;

[0050] The animal biomass preferably includes one or more of animal hair, animal feathers and animal shells, further preferably includes animal hair, animal feathers or animal shells, and more preferably includes animal shells.

[0051] In the present invention, after each flash explosion treatment, the water content of the added biomass material is preferably 20 to 80 wt %, more preferably 30 to 60 wt %, and even more preferably 50 wt %.

[0052] In the present invention, after each flash explosion treatment, there is no limitation on the amount of biomass material added, and a method well known to those skilled in the art can be used.

[0053] In the present invention, the structure of the continuous flash explosion device in step (2) is not limited, and a continuous flash explosion device with a similar principle to the "biomass continuous flash explosion and in-situ blending device based on volume pulsation" can be used. Specifically, in Examples 1 to 4 of the present invention, the continuous flash explosion device in step (2) is preferably a biomass continuous flash explosion and in-situ blending method and device based on volume pulsation, and reference can be made to the Chinese invention patent application with publication number CN108890910A.

[0054] In the present invention, adding an oxidant for reactive flash explosion can make continuous flash explosion and oxidant oxidation treatment proceed simultaneously, saving energy consumption of oxidation alone. Flash explosion provides high temperature and high pressure reaction conditions for oxidation reaction, making the reaction easier to proceed.

[0055] In the present invention, the oxidatively modified biomass material is preferably post-treated.

[0056] In the present invention, the post-treatment preferably includes: shaping the oxidatively modified biomass material, or chemically modifying the oxidatively modified biomass material and then shaping it, or mixing the oxidatively modified biomass material with a polymer to prepare a biomass composite material.

[0057] In the present invention, the chemical modification reaction includes but is not limited to cross-linking, grafting, chain extension, and copolymerization.

[0058] In the present invention, the types of polymers include but are not limited to PLA, PVA, and PBAT.

[0059] In the present invention, the parameters and conditions for the molding, the chemical modification, the molding after the chemical modification, and the preparation of the biomass composite material are not limited, and schemes well known to those skilled in the art may be adopted.

[0060] The technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0061] Example 1

[0062] This embodiment provides a biomass modification method, comprising the following steps:

[0063] (1) Premixing: 20 kg of a 20 wt% aqueous hydrogen peroxide solution and 20 kg of wheat straw were mixed in a blender to obtain a wheat straw premix having a moisture content of 50 wt%;

[0064] (2) Flash explosion: The wheat straw premix of step (1) was subjected to flash explosion treatment three times using a continuous flash explosion device. The conditions for each flash explosion treatment were: temperature 140° C., screw speed 720 rpm, to obtain an oxidized modified wheat straw material.

[0065] Figure 1 The infrared spectra of the wheat straw raw material in Example 1 and the oxidized modified wheat straw material obtained in Example 1 are shown in FIG. Figure 1 It can be seen that 1640cm -1 The characteristic peak of carbon-oxygen double bond at is significantly increased, indicating that the oxidation modification is successful during the flash explosion process.

[0066] Example 2

[0067] This embodiment provides a biomass modification method, comprising the following steps:

[0068] (1) Premixing: 30 kg of a 20 wt% aqueous hydrogen peroxide solution and 70 kg of crushed wheat straw were mixed in a blender to obtain a wheat straw premix having a moisture content of 30 wt%;

[0069] (2) Flash explosion: The wheat straw premix of step (1) is subjected to one flash explosion treatment using a continuous flash explosion device, wherein the conditions for the flash explosion treatment are: temperature 130° C., screw speed 600 rpm; then, a hydrogen peroxide aqueous solution (concentration 50 wt%) with a weight percentage of 10% of the crushed wheat straw is added to the product obtained from the first flash explosion treatment, and then the mixture is subjected to four flash explosion treatments, wherein the conditions for each flash explosion treatment are: temperature 130° C., screw speed 600 rpm, to obtain an oxidatively modified wheat straw material. Figure 2 This is the microscopic morphology of the unmodified wheat straw material. Figure 3 The microscopic morphology of the oxidized modified wheat straw material shows that the surface becomes rougher after modification, forming more dendritic protrusions and significantly increasing the specific surface area.

[0070] Example 3

[0071] This embodiment provides a biomass modification method, comprising the following steps:

[0072] (1) Premixing: 4 kg of a 12% available chlorine sodium hypochlorite aqueous solution and 6 kg of crushed corn stalks were mixed in a blender to obtain a corn stalk premix having a moisture content of 40 wt %;

[0073] (2) Flash explosion: The corn stalk premix of step (1) was flash-exploded twice using a continuous flash explosion device, each time at a temperature of 120°C and a screw speed of 150 rpm; 6 kg of crushed reed stalks with a moisture content of 50 wt% were added to the product obtained from the two flash explosions, and flash-exploded twice, each time at a temperature of 120°C and a screw speed of 150 rpm, to obtain an oxidized modified corn stalk-reed stalk blend. The microscopic morphology of the oxidized modified corn stalk-reed stalk blend is shown in FIG. Figure 4 As shown, it shows that corn stalks and reed stalks are mixed evenly and their surfaces become rougher after oxidation.

[0074] Example 4

[0075] This embodiment provides a biomass modification method, comprising the following steps:

[0076] (1) Premixing: 4 kg of a 10 wt % calcium hypochlorite aqueous solution, 3 kg of corn starch, and 7 kg of reed stalks were mixed in a stirrer to obtain a premix having a moisture content of 30 wt %;

[0077] (2) Flash explosion: The premix of step (1) was subjected to flash explosion treatment three times using a continuous flash explosion device. The conditions for each flash explosion treatment were: temperature 142° C., screw speed 900 rpm, to obtain an oxidized modified starch-reed stalk composite material.

[0078] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A biomass modification method, characterized in that: The following steps are involved: (1) Premixing: mixing a water-based oxidant solution with a biomass material to obtain a premix; (2) Flash explosion: The premix of step (1) is subjected to flash explosion treatment using a continuous flash explosion device to obtain an oxidatively modified biomass material.

2. The biomass modification method according to claim 1, characterized in that: In step (1), the water-based oxidant in the water-based oxidant solution includes one or more of hydrogen peroxide, potassium permanganate, sodium hypochlorite, calcium hypochlorite and Serat's reagent, and the concentration of the water-based oxidant solution is 1 to 50 wt%.

3. The biomass modification method according to claim 1 or 2, characterized in that: In step (1), the biomass material includes plant biomass and / or animal biomass; the plant biomass includes one or more of food in the agricultural and forestry production process, fruits in the agricultural and forestry production process, other wood cellulose in the agricultural and forestry production process, main products of agricultural product processing industry, by-products of agricultural product processing industry, waste materials of agricultural and forestry processing industry and agricultural and forestry waste; the animal biomass includes one or more of animal hair, animal feathers and animal shells.

4. The biomass modification method according to claim 3, characterized in that: In step (1), the mass of the water-based oxidant in the water-based oxidant solution is 1 to 80% of the mass of the biomass material.

5. The biomass modification method according to claim 1, characterized in that: In step (1), the water content of the premix is ​​20 to 80 wt%.

6. The biomass modification method according to claim 1, characterized in that: The number of flash explosion treatments in step (2) is 1 to 6 times; the conditions for each flash explosion treatment are independent of each other: the temperature is 80 to 240° C., and the screw speed is 20 to 1000 rpm.

7. The biomass modification method according to claim 1, characterized in that: After each flash explosion treatment, either a water-based oxidant solution or biomass material is added.

8. The biomass modification method according to claim 7, characterized in that: After each flash explosion treatment, the mass of the water-based oxidant in the added water-based oxidant solution is 1 to 80% of the mass of the biomass material in step (1).

9. The biomass modification method according to claim 7 or 8, characterized in that: After each flash explosion treatment, the moisture content of the added biomass material is 20-80 wt%.

10. The biomass modification method according to claim 1, characterized in that: The oxidatively modified biomass material is post-processed, and the post-processing includes: molding the oxidatively modified biomass material, or chemically modifying the oxidatively modified biomass material and then molding it, or mixing the oxidatively modified biomass material with a polymer to prepare a biomass composite material.

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