CN115959649A - Preparation method of irradiated starch-based hard carbon material - Google Patents
Preparation method of irradiated starch-based hard carbon material Download PDFInfo
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- CN115959649A CN115959649A CN202211698141.6A CN202211698141A CN115959649A CN 115959649 A CN115959649 A CN 115959649A CN 202211698141 A CN202211698141 A CN 202211698141A CN 115959649 A CN115959649 A CN 115959649A
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Abstract
A method for preparing an irradiated starch-based hard carbon material, comprising: 1. swelling and breaking of starch granules. Putting 100 parts of starch into a high-speed stirring mixer, adding 5-20 parts of plasticizer, and stirring at a high speed to realize swelling and micro-swelling of starch granules; 2. radiation crosslinking of starch. Slowly adding 2 to 20 parts of cross-linking agent and 0.5 to 5 parts of coupling agent in sequence while mixing and stirring starch and plasticizer, and uniformly mixing after stirring for 3 to 5 min; placing the mixed powder in a tray, paving, and then conveying to an electron accelerator for irradiation to obtain irradiation cross-linked starch; the irradiation dose is 10 to 100kGy; 3. and (6) carbonizing. And (2) carrying out constant-temperature carbonization treatment on the irradiated crosslinked starch in an inert atmosphere, annealing, washing with acid liquor, absolute ethyl alcohol and water in sequence, and drying to obtain the starch-based hard carbon material. The process for modifying the starch by electron beam irradiation is simple, high in treatment efficiency, environment-friendly, low-carbon and suitable for batch production of hard carbon materials.
Description
Technical Field
The invention relates to the technical field of preparation of starch-based capacitive activated carbon, in particular to a preparation method of an irradiation starch-based hard carbon material.
Background
The biomass material comprises cellulose, lignin, starch and the like, can be used for preparing hard carbon materials, and is widely applied to the fields of alkali metal batteries, supercapacitors, oil-water separation, catalysis and the like. Due to the complexity of the structure and components of the biomass raw material, the research on the carbon forming mechanism and the process control are particularly important, and the realization of the efficient batch production of the hard carbon material also becomes the focus of attention of researchers in the current industry.
The starch has wide sources, and has the advantages of low cost, greenness, renewability, high carbon content and the like. However, the thermal stability of starch molecular chains is poor, a large amount of volatile matters are easily generated in the thermal cracking process, and the spherical structure of the starch is damaged by the quick release of the volatile matters, so that the compaction density of the capacitance carbon material is low, and the energy density of a capacitor is influenced.
CN103647082B discloses a preparation method of a hard carbon microsphere negative electrode material of a lithium ion secondary battery. Starch is used as a raw material, and the hard carbon microspheres are prepared through stabilizing and carbonizing processes under a reduced pressure condition. The method effectively inhibits the caking problem of starch particles in the carbonization process, and keeps the good sphericity and dispersity of the starch-based hard carbon, but the method needs to heat and stabilize the starch at a lower temperature for a long time, so that the preparation time of the hard carbon microspheres is too long.
CN115207350A discloses a hard carbon negative electrode material of a sodium ion battery with an ultra-low specific surface area and a preparation method thereof, the method can solve the problems of poor starch thermal stability, structural fusion foaming and the like, and improve the surface pores and defect concentration of hard carbon. However, the esterification reaction time in the method is long (1-10 h), and after the reaction, alkali liquor, organic reagent and water are required to be adopted for washing, filtering, freeze-drying and reduction reaction in sequence, so that the process is complex. And the dry starch granules are compact, the anhydride can only react with the starch on the surfaces of the granules, the molecular chains in the granules are difficult to fully crosslink, and the reaction efficiency of the anhydride is low.
In summary, the prior art has the following disadvantages:
(1) The traditional starch-based hard carbon material has long preparation time and complex process flow;
(2) The cross-linking reaction can avoid the hollow structure of the product and improve the tap density of the hard carbon material, but the reaction efficiency of the conventional cross-linking reaction is low, and starch particles are difficult to permeate, so that the cross-linking is insufficient.
Therefore, how to solve the above-mentioned deficiencies of the prior art is a problem to be solved by the present invention.
Disclosure of Invention
The invention aims to provide a preparation method of an irradiated starch-based hard carbon material.
In order to achieve the purpose, the invention adopts the technical scheme that:
a method for preparing an irradiated starch-based hard carbon material, comprising:
step one, swelling and crushing of starch granules
Putting 100 parts of starch into a high-speed stirring mixer, adding 5-20 parts of plasticizer, and stirring at 800-1200 rpm for 4-8 minutes to realize swelling and micro-swelling of starch granules;
step two, irradiation crosslinking of starch
While mixing and stirring the starch and the plasticizer, slowly adding 2-20 parts of the cross-linking agent and 0.5-5 parts of the coupling agent in sequence, stirring for 3-5 min, and uniformly mixing; placing the mixed powder in a tray, paving the mixed powder, and then conveying the mixed powder to an electron accelerator for irradiation under beams to obtain irradiation crosslinked starch; the irradiation dose is 10-100 kGy;
step three, carbonizing
And (2) carrying out constant-temperature carbonization treatment on the irradiated crosslinked starch in an inert atmosphere, annealing, washing with acid liquor, absolute ethyl alcohol and water in sequence, and drying to obtain the starch-based hard carbon material.
In a further technical scheme, the starch comprises one or more of corn starch, waxy corn starch, tapioca starch, potato starch and wheat starch.
According to a further technical scheme, the plasticizer comprises one or more of ethylene glycol, glycerol, xylitol, sorbitol, erythritol, mannitol, pentaerythritol and polyvinyl alcohol, and the function of the plasticizer is to break hydrogen bond structures among starch molecular chains and realize swelling and breaking of starch particles.
According to a further technical scheme, the cross-linking agent comprises one or more of hexanediol diacrylate, triallyl isocyanurate, trimethylolpropane triacrylate and pentaerythritol triacrylate, and the cross-linking agent mainly plays a role in generating cross-linking points among molecular chains to enable starch to be cross-linked.
According to a further technical scheme, the coupling agent is one of 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane and 3-methacryloxypropyltriisopropoxysilane, unsaturated double bonds in silane participate in grafting reaction under electron beam irradiation, and silicon oxygen bonds are hydrolyzed to form a cross-linked structure, so that the cross-linking degree of a starch molecular chain is further improved.
In the second step, the energy of the electron accelerator is 2-10 MeV, and the thickness of the spread powder is 5-20 mm.
The working principle and the advantages of the invention are as follows:
the invention utilizes a novel green and environment-friendly electron beam irradiation process to realize the activation of starch molecular chains, and realizes the full penetration of a cross-linking agent to starch molecules and the full cross-linking of the starch molecular chains by means of the swelling and the damage of a plasticizer to starch granules. The starch subjected to electron beam irradiation crosslinking and activation has good thermal stability, the problem of fusion foaming can be avoided, the pores and defect concentration on the surface of the hard carbon can be improved, and finally the starch-based hard carbon material with good spherical structure, high carbon yield and high tap density is obtained.
According to the invention, the generation of free radicals in starch molecules is promoted by introducing electron beam irradiation, and in the process of preparing the hard carbon material, the existence of the free radicals can promote the carbonization reaction, so that the carbonization time is effectively shortened, the reaction efficiency is improved, and the material performance is finally improved.
According to the invention, the chemical crosslinking reaction of starch molecules and the micromolecule crosslinking agent is initiated through electron beam irradiation, so that the thermal stability of starch is improved, the problem of melting and foaming in the preparation process of the hard carbon material is avoided, and the pores and defect concentration on the surface of the hard carbon are effectively improved.
The invention can promote the swelling and the cracking of starch granules by introducing the micromolecule plasticizer, is convenient for the micromolecule cross-linking agent to fully permeate, and improves the efficiency of the cross-linking reaction.
The electron beam irradiation modified starch has the advantages of simple process, high treatment efficiency, environmental protection and low carbon, and is suitable for batch production of hard carbon materials.
Detailed Description
The invention is further described below with reference to examples:
the embodiment is as follows: the present disclosure will be described in detail, and it is understood that variations and modifications can be made by the techniques taught in the present disclosure without departing from the spirit and scope of the present disclosure by those skilled in the art after understanding the embodiments of the present disclosure.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. The singular forms "a", "an", "the" and "the", as used herein, also include the plural forms. As used herein, the terms "comprising," "including," "having," and the like are open-ended terms that mean including, but not limited to.
As used herein, the term (terms), unless otherwise indicated, shall generally have the ordinary meaning as commonly understood by one of ordinary skill in the art, in this written description and in the claims. Certain terms used to describe the disclosure are discussed below or elsewhere in this specification to provide additional guidance to those skilled in the art in describing the disclosure.
Example 1:
(1) 1000g of corn starch is placed in a high-speed stirring mixer, 100g of sorbitol is added, and high-speed stirring is carried out for 8 minutes at 800rpm, so that swelling and micro-swelling of starch granules are realized.
(2) While stirring the mixed powder, 50g of triallyl isocyanurate and 30g of 3-methacryloxypropyl triisopropoxysilane were gradually added in this order, and the mixture was stirred for 5 minutes and then mixed uniformly. The mixed powder is placed in a rectangular tray and paved to be about 5mm thick, and then the mixed powder is conveyed to a 2MeV electron accelerator to be irradiated to obtain the irradiation cross-linked starch. The irradiation dose was 20kGy.
(3) And (2) carrying out constant-temperature carbonization treatment on the irradiated crosslinked starch in an inert atmosphere, annealing, washing with acid liquor, absolute ethyl alcohol and water in sequence, and drying to obtain the starch-based hard carbon material.
Example 2:
(1) 1000g of cassava starch is placed in a high-speed stirring mixer, 200g of glycerol is added, and the high-speed stirring is carried out for 5 minutes at 1000rpm, so that the swelling and micro-swelling of the starch granules are realized.
(2) While stirring the mixed powder, 100g of hexanediol diacrylate and 50g of 3-methacryloxypropyl trimethoxysilane were slowly added in this order, and the mixture was stirred for 5min and then mixed uniformly. The mixed powder is placed in a rectangular tray and is paved to be about 10mm thick, and then the mixed powder is conveyed to a 5MeV electron accelerator to be irradiated to obtain the irradiation cross-linked starch. The irradiation dose was 30kGy.
(3) And (2) carrying out constant-temperature carbonization treatment on the irradiated crosslinked starch in an inert atmosphere, annealing, washing with acid liquor, absolute ethyl alcohol and water in sequence, and drying to obtain the starch-based hard carbon material.
Example 3:
(1) Placing 500g of potato starch and 500g of corn starch in a high-speed stirring mixer, adding 150g of ethylene glycol, and stirring at 1000rpm for 4 minutes to realize swelling and micro-swelling of starch granules.
(2) While stirring the mixed powder, slowly adding 30g of trimethylolpropane triacrylate and 5g of 3-methacryloxypropyltriethoxysilane in turn, stirring for 5min, and mixing uniformly. The mixed powder is placed in a rectangular tray to be paved, the thickness is about 10mm, and then the mixed powder is conveyed to a 5MeV electron accelerator to be irradiated, so that the irradiated and crosslinked starch is obtained. The irradiation dose was 30kGy.
(3) And (3) carrying out constant-temperature carbonization treatment on the irradiation crosslinked starch in an inert atmosphere, annealing, sequentially washing with acid liquor, absolute ethyl alcohol and water, and drying to obtain the starch-based hard carbon material.
Example 4:
(1) 1000g of wheat starch is placed in a high-speed stirring mixer, 75g of sorbitol and 75g of pentaerythritol are added, and high-speed stirring is carried out for 4 minutes at 800rpm, so that swelling and micro-swelling of starch granules are realized.
(2) While stirring the mixed powder, 20g of pentaerythritol triacrylate and 10g of 3-methacryloxypropyl triisopropoxysilane were added slowly in this order, and the mixture was stirred for 5min and then mixed uniformly. The mixed powder is placed in a rectangular tray to be paved into a rectangular tray with the thickness of about 20mm, and then the rectangular tray is conveyed to a 10MeV electron accelerator to be irradiated, so that the irradiation cross-linked starch is obtained. The irradiation dose was 80kGy.
(3) And (2) carrying out constant-temperature carbonization treatment on the irradiated crosslinked starch in an inert atmosphere, annealing, washing with acid liquor, absolute ethyl alcohol and water in sequence, and drying to obtain the starch-based hard carbon material.
Comparative example 1:
(1) 1000g of corn starch was placed in a high speed mixer, 100g of sorbitol was added and high speed stirred at 800rpm for 8 minutes to achieve swelling and micro-swelling of the starch granules.
(2) While stirring the mixed powder, 50g of triallyl isocyanurate and 30g of 3-methacryloxypropyl triisopropoxysilane were gradually added in this order, and the mixture was stirred for 5 minutes and then mixed uniformly. And (3) placing the mixed powder under the protection of nitrogen, and reacting for 2h at 140 ℃.
(3) And (2) carrying out constant-temperature carbonization treatment on the crosslinked starch in an inert atmosphere, annealing, sequentially washing with acid liquor, absolute ethyl alcohol and water, and drying to obtain the starch-based hard carbon material.
Comparative example 2:
(1) 1000g of corn starch was placed in a high-speed stirring mixer, and stirred at a high speed of 800rpm, while 50g of triallyl isocyanurate and 30g of 3-methacryloxypropyl triisopropoxysilane were slowly added in this order, and stirred for 5min and mixed uniformly. The mixed powder is placed in a rectangular tray and paved to be about 5mm thick, and then the mixed powder is conveyed to a 2MeV electron accelerator to be irradiated to obtain the irradiation cross-linked starch. The irradiation dose was 20kGy.
(2) And (2) carrying out constant-temperature carbonization treatment on the irradiated crosslinked starch in an inert atmosphere, annealing, washing with acid liquor, absolute ethyl alcohol and water in sequence, and drying to obtain the starch-based hard carbon material.
The cross-linking degree, carbon yield and tap density of the material in the scheme are shown in the following table 1:
TABLE 1
| Examples | Degree of crosslinking (%) | Carbon yield (%) | Tap density (g/cm) 3 ) |
| Example 1 | 82 | 45 | 0.67 |
| Example 2 | 73 | 39 | 0.59 |
| Example 3 | 80 | 42 | 0.63 |
| Example 4 | 78 | 40 | 0.62 |
| Comparative example 1 | 18 | 28 | 0.38 |
| Comparative example 2 | 35 | 32 | 0.45 |
As can be seen from Table 1, in examples 1 to 4, the starch particles are slightly swollen by using the plasticizer, and are crosslinked by using the polyfunctional unsaturated monomer, and the high-efficiency crosslinking reaction is realized by the electron beam irradiation, so that the obtained particles have high crosslinking degree, and the hard carbon material has high carbon yield and high tap density. Comparative example 1 the same formulation as in example 1 was used, but crosslinking was not initiated by electron beam irradiation, but was initiated by heat, and the crosslinking efficiency was significantly reduced, so that the degree of crosslinking was low, and the carbon yield and tap density were not satisfactory. Comparative example 2 a formulation similar to that of example 1 was used, but sorbitol was not previously used to swell the starch granules, which affects the effect of the small-molecule crosslinking agent penetrating into the starch granules to perform the crosslinking reaction, and thus the degree of crosslinking of the granules was low, and the hard carbon material had a low carbon yield and a small tap density.
The above embodiments are only for illustrating the technical idea and features of the present invention, and the purpose of the present invention is to enable those skilled in the art to understand the content of the present invention and implement the present invention, and not to limit the protection scope of the present invention by this means. All equivalent changes and modifications made according to the spirit of the present invention should be covered in the protection scope of the present invention.
Claims (6)
1. A preparation method of an irradiated starch-based hard carbon material is characterized by comprising the following steps: the method comprises the following steps:
step one, swelling and crushing starch granules
Putting 100 parts of starch into a high-speed stirring mixer, adding 5-20 parts of plasticizer, and stirring at 800-1200rpm for 4~8 minutes at high speed to realize swelling and micro-swelling of starch granules;
step two, irradiation crosslinking of starch
While mixing and stirring starch and a plasticizer, slowly adding 2-20 parts of a cross-linking agent and 0.5-5 parts of a coupling agent in sequence, and stirring for 3-5 min and then uniformly mixing; placing the mixed powder in a tray, paving the mixed powder, and then conveying the mixed powder to an electron accelerator for irradiation under beams to obtain irradiation crosslinked starch; the irradiation dose is 10 to 100kGy;
step three, carbonizing
And (2) carrying out constant-temperature carbonization treatment on the irradiated crosslinked starch in an inert atmosphere, annealing, washing with acid liquor, absolute ethyl alcohol and water in sequence, and drying to obtain the starch-based hard carbon material.
2. The method of claim 1, wherein the method comprises the steps of: the starch comprises one or more of corn starch, waxy corn starch, cassava starch, potato starch and wheat starch.
3. The method of claim 1, wherein the method comprises the steps of: the plasticizer comprises one or more of ethylene glycol, glycerol, xylitol, sorbitol, erythritol, mannitol, pentaerythritol and polyvinyl alcohol, and has the function of destroying hydrogen bond structures among starch molecular chains to realize swelling and destruction of starch granules.
4. The method for preparing an irradiated starch-based hard carbon material according to claim 1, wherein: the cross-linking agent comprises one or more of hexanediol diacrylate, triallyl isocyanurate, trimethylolpropane triacrylate and pentaerythritol triacrylate, and mainly plays a role in generating cross-linking points among molecular chains to cross-link starch.
5. The method of claim 1, wherein the method comprises the steps of: the coupling agent is one of 3-methacryloxypropyl trimethoxy silane, 3-methacryloxypropyl triethoxy silane and 3-methacryloxypropyl triisopropoxy silane, unsaturated double bonds in the silane participate in grafting reaction under the irradiation of electron beams, and silicon-oxygen bonds are hydrolyzed to form a cross-linking structure, so that the cross-linking degree of a starch molecular chain is further improved.
6. The method for preparing an irradiated starch-based hard carbon material according to claim 1, wherein: in the second step, the energy of the electronic accelerator is 2 to 10MeV, and the thickness of the spread powder is 5 to 20mm.
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| CN117384323A (en) * | 2023-12-12 | 2024-01-12 | 成都锂能科技有限公司 | Starch-based precursor material and preparation method and application thereof |
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| CN117384323A (en) * | 2023-12-12 | 2024-01-12 | 成都锂能科技有限公司 | Starch-based precursor material and preparation method and application thereof |
| CN117384323B (en) * | 2023-12-12 | 2024-03-08 | 成都锂能科技有限公司 | Starch-based precursor material and preparation method and application thereof |
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