CN114455950B - Method for preparing graphite carrier boat from lignin-rich plant - Google Patents

Abstract

The invention relates to a method for preparing a graphite boat from lignin-rich plants, which comprises the following steps: providing a plant body rich in lignin, and carrying out high-temperature pyrolysis treatment on the plant body rich in lignin to obtain carbonized powder; mixing the carbonized powder, the asphalt powder and the adhesive to obtain a mixture; pressing and forming the mixture to obtain a preformed carrier boat; dehydrating the preformed carrier boat and then sintering to obtain a formed carbon carrier boat; adding a mixture of carbonized powder and asphalt powder into the formed carbon carrier boat, performing secondary sintering treatment, and taking out a coked mixture in the carrier boat after secondary sintering to obtain a secondary sintering carrier boat; and tempering the secondary sintering carrier boat to obtain the graphite carrier boat. The invention realizes plant body pyrolysis, plant body coke making and boat carrying soaking and baking in one step; and (5) after the processing and forming, graphitizing is completed. The technological means of sintering, soaking and baking are adopted in the technological process to shorten the production period of the product.

Description

Method for preparing graphite carrier boat from lignin-rich plant

Technical Field

The invention relates to the technical field of new materials, in particular to a method for preparing a graphite carrier boat by using lignin-rich plants.

Background

Carbon in nature is a variety of allotropes-diamond, graphite, graphene, carbon nanotubes, C ₆₀ Hexagonal diamond (blue silk stone). Diamond and graphite have long been known and after experiments were performed with rawa tin to burn diamond and graphite, it was determined that both substances burned to produce CO ₂ It follows that diamond and graphite contain the same "base", referred to as carbon. It is the first time that ravaltin has carbon listed in the periodic table. C (C) ₆₀ Is found in 1985 by the chemist of university of houston, haliotid et al, U.S. and is a spherical stable carbon molecule consisting of 60 carbon atoms, the third allotrope of carbon after diamond and graphite. Bamboo contains ash 0.53%, lignin 36.51%, cellulose 53.06%, pentosan 29.27% (total). Cellulose contains pentosan 20.54%, and the main component in ash is potassium hydroxide. The carbon content is about 30% by elemental proportion.

In the general knowledge in the field of organic chemistry, the bond energy of the C-C bond is about 345.6KJ/mol, the bond energy of the C-H bond is about 415.3KJ/mol, the bond energy of the C=C double bond is about 615KJ/mol, and the triple bond energy is 836.8KJ/mol. The shorter the bond length, the greater the bond energy. The chemical bond formed by the same element has double bond energy larger than single bond energy. Bond lengths may be compared approximately by atomic radius, and so on. Since the atomic radius of carbon is larger than that of oxygen. Bond energy: oxygen double bond > carbon-oxygen single bond. Based on the principle of low energy balance based on physics and the basic bond energy parameters, bamboo can be finally made into pure carbon materials by artificial methods under proper external conditions.

The graphite carrier used in the manufacturing of the lithium battery anode material has the advantages that the graphite carrier is low in consumption and free of metal impurity pollution in the processing of the anode material, and the performance requirements on the graphite carrier are particularly shown in the following aspects: fine structure, high strength, high compactness, stable resistivity, etc. The carrier boat with the pure graphite structure made of the bamboo charcoal is completely suitable for the manufacturing requirement of lithium battery cathode materials in the aspects.

Disclosure of Invention

In order to solve the problems in the prior art, the invention provides a method for preparing a graphite boat by using lignin-rich plants.

The technical scheme of the invention is as follows:

a method for preparing a graphite boat from lignin-rich plants, comprising the steps of:

providing a plant body rich in lignin, and carrying out high-temperature pyrolysis treatment on the plant body rich in lignin to obtain carbonized powder;

mixing the carbonized powder, the asphalt powder and the adhesive to obtain a mixture;

pressing and forming the mixture to obtain a preformed carrier boat;

dehydrating the preformed carrier boat and then sintering to obtain a formed carbon carrier boat;

adding a mixture of carbonized powder and asphalt powder into the formed carbon carrier boat, performing secondary sintering treatment, and taking out a coked mixture in the carrier boat after secondary sintering to obtain a secondary sintering carrier boat;

and tempering the secondary sintering carrier boat to obtain the graphite carrier boat.

Optionally, the lignin-rich plant body is bamboo, pine, corn cob, coconut husk, or tea seed oil husk.

Optionally, the temperature of the pyrolysis treatment is 600-1000 ℃.

Optionally, the carbonized powder has a particle size of 1 μm to 10mm.

Optionally, 40-95 parts of carbonized powder, 5-60 parts of asphalt powder and 10-20 parts of adhesive are mixed according to parts by weight.

Optionally, the step of dehydrating the preformed carrier boat and then sintering to obtain the molded carbon carrier boat specifically comprises the following steps:

and (3) dehydrating the preformed carrier boat at 100-200 ℃, loading the dehydrated preformed carrier boat into a sintering furnace, raising the pressure of the sintering furnace to 1.1-1.3Mpa, maintaining the pressure unchanged, raising the temperature to 600-1200 ℃, preserving the heat for 120-240 minutes, and then cooling and releasing the pressure to obtain the formed carbon carrier boat.

Optionally, the tempering treatment is performed at a temperature of 1000-3100 ℃.

Optionally, the particle size of the asphalt powder is 0.1-2mm.

Optionally, the adhesive is a glutinous rice adhesive.

Further alternatively, the preparation method of the glutinous rice adhesive comprises the following steps:

adding 9-10 kg of water into each kg of glutinous rice, adding water into the glutinous rice, placing into a container with 3000 rpm rotary blades, heating to 100deg.C, stopping heating, and simultaneously starting the rotary blades to operate for 1 min; stopping heating when the temperature is heated to 100 ℃ again, and simultaneously starting the rotary blade to run for 1 minute; and the sticky rice adhesive is obtained after 10-12 times of round trip.

The beneficial effects are that: the raw material formula of the invention takes plant bodies rich in lignin such as bamboo, wood and the like as the most original base material, takes plant body coke as a framework material, takes medium-temperature asphalt powder as a coking agent, adds an adhesive, finishes the preforming of the graphite carrier by using a high-purity hydrocarbon oxygen three-element system at the level of atomic level to nm level, and then realizes the preparation of the graphite carrier through high-temperature graphitization. The invention realizes plant body pyrolysis, plant body coke making and boat carrying soaking and baking in one step; and (5) after the processing and forming, graphitizing is completed. The technological means of sintering, soaking and baking are adopted in the technological process to shorten the production period of the product.

Drawings

FIG. 1 is a schematic flow chart of preparing a graphite boat.

Fig. 2 is a schematic diagram of the sintering process flow in fig. 1.

Detailed Description

The invention provides a method for preparing a graphite boat by using lignin-rich plants, which is used for making the purposes, technical schemes and effects of the invention clearer and more definite, and is further described in detail below. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.

The embodiment of the invention provides a method for preparing a graphite boat by using lignin-rich plants, which comprises the following steps:

s1, providing a plant body rich in lignin, and performing high-temperature pyrolysis treatment on the plant body rich in lignin to obtain carbonized powder;

s2, mixing the carbonized powder, the asphalt powder and the adhesive to obtain a mixture;

s3, performing compression molding on the mixture to obtain a preformed carrier boat;

s4, dehydrating the preformed carrier boat and then sintering to obtain a formed carbon carrier boat;

s5, adding a mixture of carbonized powder and asphalt powder into the molded carbon carrier boat, performing secondary sintering treatment, and taking out a coked mixture in the carrier boat after secondary sintering is finished to obtain a secondary sintering carrier boat;

and S6, tempering the secondary sintering carrier to obtain the graphite carrier.

The material formula and the process flow of the embodiment are completely different from the conventional carbon material and the carbon product, and are novel processes for preparing pure carbon materials by a hot-press sintering method. The raw material formula takes plant bodies rich in lignin such as bamboo, wood and the like as the most original base materials, takes plant body coke as a framework material, takes medium-temperature asphalt powder as a coking agent, adds an adhesive, finishes the preforming of the graphite carrying boat by using a high-purity hydrocarbon oxygen three-element system at the level of atomic level to nm level, and then realizes the preparation of the graphite carrying boat through high-temperature graphitization. The conventional carbon product must be impregnated and sintered separately, and the present embodiment is completed at the same time as the conventional carbon product is impregnated, sintered, and impregnated. Namely, the embodiment realizes the coke making and boat loading soaking and baking of the plants in one step. The technical means of sintering, soaking and baking combination are adopted in the technological process of the embodiment, so that the production period of the product is shortened.

Compared with the existing method, the method of the embodiment has the following technical advantages:

1. in the embodiment, the carbon product is directly manufactured from organic matters (plant bodies rich in lignin), and the carbon production, the coking, the roasting, the impregnation and the graphitization are performed in an overlapping manner, so that the energy sources are greatly saved and the manufacturing period is shortened;

2. the purity of the product is determined by the purity of the original material, lignin-rich plant bodies are adopted as the original material, and impurities are not easy to introduce in the manufacturing process of the pure graphite material, so that the purity of the product is ensured, and the obtained product has stable quality;

3. bamboo and the like are made into basic industrial materials, which is favorable for regeneration and benefits the next generation.

The key technical problems to be solved in the preparation of the graphite carrier boat by adopting plants containing a large amount of lignin such as bamboo, wood and the like in the embodiment are that the structure, strength, compactness, resistivity and the like of the prepared carbon material are required to meet the use requirements when the lithium battery cathode material is prepared. Based on this, the parameters involved in the preparation process are further optimized in this example.

In step S1, in one embodiment, the lignin-rich plant body may be bamboo, pine, corn cob, coconut husk, tea seed oil husk, or the like. In the preparation process of the pure graphite material, the plant body is not easy to introduce impurities.

In one embodiment, the high temperature cracking treatment is at a temperature of 600 to 1000 ℃.

In one embodiment, the carbonized powder has a particle size of 1 μm to 10mm. Further, the particle size of the carbonized powder is 1-3 μm. The carbonized powder with the particle size can ensure that the pores of the semi-finished product in the sintering process section are small enough, so that the porosity of the final product reaches the standard.

In step S2, in one embodiment, 40 to 95 parts by weight of the carbonized powder, 5 to 60 parts by weight of the pitch powder, and 10 to 20 parts by weight of the binder are mixed.

In one embodiment, the pitch powder has a particle size of 0.1 to 2mm. The asphalt powder is prepared from asphalt by an air mill, the asphalt powder can be replaced by epoxy resin powder, the purity is 99.6%, and the epoxy resin powder is prepared from epoxy resin by the air mill.

In one embodiment, the adhesive is a sticky rice adhesive. The glutinous rice adhesive contains C and H ₂ O, no other elements are introduced, water except carbon is volatilized after pyrolysis, and the probability of generating holes at the later atomic level is ensured to be reduced. The high-viscosity glutinous rice liquid is necessary for molding, and the bamboo charcoal cracking carbonized powder and the medium-temperature asphalt powder (air flow mill) are difficult to mold without the high-viscosity glutinous rice liquid, so that the high-viscosity glutinous rice liquid cannot be mixed and pressed.

In one embodiment, the preparation method of the sticky rice adhesive comprises the following steps:

adding water into glutinous rice according to the proportion of adding 9-10 kg of water into each kg of glutinous rice, placing into a container with 3000 rpm rotary blades, stopping heating when the temperature is 100 ℃, and simultaneously starting the rotary blades to run for 1 minute; stopping heating when the heating system is started again to heat to 100 ℃, and simultaneously starting the rotary blade to run for 1 minute; the adhesive reaches the requirement after 10-12 times of round trip: no particles/high viscosity.

In step S4, in one embodiment, the step of dehydrating the preformed carrier and then sintering to obtain a molded carbon carrier specifically includes:

and (3) dehydrating the preformed carrier boat at 100-200 ℃, loading the dehydrated preformed carrier boat into a sintering furnace, raising the pressure of the sintering furnace to 1.1-1.3Mpa, maintaining the pressure unchanged, raising the temperature to 800-1200 ℃, stopping heating, preserving the heat for 120-240 minutes, and then cooling and releasing the pressure to obtain the formed carbon carrier boat.

The specific heat preservation and pressure maintaining are related to different formulas. The holding time and the pressure maintaining time are related to the selection of raw material formulas, and when the components with low normal pressure decomposition temperature of the raw materials are more (for example, the glutinous rice adhesive is more), the holding time is prolonged, and otherwise, the holding time is shortened.

Wherein the rate of the boost may be 0.001 Mpa/sec.

Wherein the rate of temperature rise may be 30 ℃/hour.

Wherein, the pressure and temperature reduction can be carried out for 20 hours.

In step S5, in one embodiment, a mixture of carbonized powder and asphalt powder is added into the molded carbonaceous carrier, and secondary sintering treatment is performed, and after the secondary sintering is completed, the mixture coked in the carrier is taken out, thereby obtaining the secondary sintering carrier. Wherein the temperature of the secondary sintering treatment is 800-1200 ℃, and the time of the secondary sintering treatment is 120-240 minutes.

In this embodiment, the purposes of adding the carbonized powder and the asphalt powder are mainly two: firstly, asphalt powder is used as a liquid leaching material to be partially spread into a boat-carrying entity at 200-300 ℃ to achieve the purpose of leaching, namely, a part of asphalt is permeated into the boat-carrying entity; secondly, after the mixture is continuously heated, the mixture is mixed and coked to generate bamboo coke, and the coke is a main raw material for producing the carrier boat.

In this embodiment, the boat density can be increased by two times of sintering.

In step S6, in one embodiment, the tempering treatment is performed at a temperature of 1000-3100 ℃. The conductivity and porosity of the carbon material are determined by the tempering process. The process of converting carbon into graphite is a volume shrinkage process, and when the parameters of the hot-press sintering process are controlled, the pores of the carbon block are uniform and less than 10.0 percent. In the next material self-conversion process, the pores of the carbon block gradually decrease to below 1% along with the volume shrinkage of the carbon block converted to graphite. At this time, the temperature is higher than 1800 ℃, all the conversion is completed at 3100 ℃, and at this time, the material is completely graphite without adjustable resistance, so that the tempering parameters are specifically determined according to the conductivity and porosity requirements used.

The preparation process and principle of the graphite carrier boat are described below with bamboo and wood plant as raw materials.

Fig. 1 is a schematic flow chart of preparing a graphite carrier, specifically, bamboo and wood carbonized powder and medium-temperature asphalt powder prepared by high-temperature pyrolysis of bamboo and wood are mixed, glue (i.e. adhesive) is added, then mixed and pressed, and then pretreatment is carried out at 160 ℃, and then sintering treatment is carried out twice, and high-temperature graphitization is carried out, so that the preparation of the graphite carrier can be realized. Fig. 2 is a key process of preparing coke by bamboo charcoal, carrying boat, soaking, baking and sintering, namely: and carrying out boat soaking, baking and sintering, and simultaneously completing a process curve of preparing the coke by the bamboo charcoal. Mixing the bamboo charcoal carbonized powder, asphalt powder and glutinous rice liquid adhesive, putting into preformed graphite carrier boat blank (full), and performing preset sintering process flow according to the process curve of figure 2, wherein the preformed carrier boat is soaked and baked, and the bamboo charcoal in the boat is prepared into coke at the same time. The abscissa of fig. 2 is the time axis and the ordinate is a qualitative representation of pressure, power. The pressure line means the pressure increasing, pressure maintaining and pressure releasing process which changes along with time, and the pressure line P represents the pressure maintaining period; the power line is the whole process of temperature rise, heat preservation and temperature reduction which change along with time, wherein the power lines A, B respectively represent constant power for a period of time. The section A is a low-power section relative to the section B, and the temperature of the heated blank body is gradually increased and reaches the decomposition temperature of the adhesive; the B section is a high-power section relative to the A section, and the temperature of the heated blank body is increased again at the moment and reaches the high-temperature anaerobic carbonization of high-temperature pyrolyzed substances such as bamboo charcoal and asphalt powder. The purpose is that the two-stage counterparts are decomposed and carbonized respectively and fully. The bamboo charcoal high-temperature cracking carbonized powder and the medium-temperature asphalt powder are adopted as a raw material system, and have the advantages that: other impurities are not easy to be introduced in the manufacturing process of the pure graphite material. The addition of adhesive (binder) refers to adding special high viscosity glutinous rice liquid binder, and the components are C+H ₂ O, without other elements introduced, volatilizes water except carbon after pyrolysis (section A), and ensures that the probability of generating holes at the later atomic level is reduced. The addition of the high-viscosity glutinous rice liquid is necessary for molding, and the bamboo charcoal cracking coking powder and the medium-temperature asphalt powder (air flow mill) are difficult to mold without the high-viscosity glutinous rice liquid, so that the mixture cannot be pressed.

The corresponding coordinate values and units of the abscissa in the figure are respectively: the abscissa is the time axis, taking hours as a unit, the whole process is approximately 25 hours; the ordinate corresponds to heating power and pressure; the power A section is 100kw and the power B section is 180kw, and the pressure P is 1-2 Mpa (the material systems are different, but the principle of the corresponding material decomposition step by step under a certain temperature and pressure is the same).

The purity of the graphite boat manufactured by the combined coking and sintering processes is completely determined by the raw materials themselves. When the secondary sintering carrier is heated to a certain temperature for tempering treatment, impurities in high-temperature pyrolysis products such as bamboo, wood and the like and asphalt can be decomposed and volatilized (mainly KOH) along with the temperature rise. The pore of the carbon material is determined by the conversion degree of the secondary sintering carrier to graphite, the conversion process of the secondary sintering carrier to graphite is a volume shrinkage process, the combined coking and sintering processes are well controlled, the pore of the graphite carrier is uniform and less than 10.0%, the residual H, O element in the graphite carrier is discharged along with further coking decomposition of the conversion of the secondary sintering carrier to graphite in the graphitization process, the volume is shrunk again, and the pore is gradually reduced to below 1.0%. The performance indexes of the carbon material manufactured by raw materials containing a large amount of lignin such as bamboo, wood and the like are as follows: a density greater than 1.80; the open porosity is less than 1%; the flexural strength is more than 90Mpa; the conductivity is improved along with the improvement of graphitization degree, and the resistivity of the product can be accurately controlled according to the use requirement.

It is to be understood that the invention is not limited in its application to the examples described above, but is capable of modification and variation in light of the above teachings by those skilled in the art, and that all such modifications and variations are intended to be included within the scope of the appended claims.

Claims (8)

1. A method for preparing a graphite boat from lignin-rich plants, comprising the steps of:

providing a plant body rich in lignin, and carrying out high-temperature pyrolysis treatment on the plant body rich in lignin to obtain carbonized powder, wherein the grain size of the carbonized powder is 1 mu m-10mm;

mixing the carbonized powder, the asphalt powder and the adhesive to obtain a mixture;

pressing and forming the mixture to obtain a preformed carrier boat;

dehydrating the preformed carrier boat and then sintering to obtain a formed carbon carrier boat;

adding a mixture of carbonized powder and asphalt powder into the formed carbon carrier boat, and performing secondary sintering treatment, wherein the temperature of the secondary sintering treatment is 800-1200 ℃, the secondary sintering treatment time is 120-240 minutes, and the coked mixture in the carrier boat is taken out after secondary sintering is finished to obtain a secondary sintering carrier boat;

and tempering the secondary sintering carrier boat, wherein the tempering temperature is 1000-3100 ℃, and the graphite carrier boat is obtained.

2. The method of preparing a graphite boat from lignin-rich plant material of claim 1 wherein the lignin-rich plant material is bamboo, pine, corn cob, coconut husk or tea seed oil husk.

3. The method of preparing a graphite boat from lignin-rich plants according to claim 1 wherein the pyrolysis treatment is at a temperature of 600-1000 ℃.

4. The method of preparing a graphite boat from lignin-rich plants according to claim 1, wherein 40-95 parts by weight of the carbonized powder, 5-60 parts by weight of pitch powder and 10-20 parts by weight of a binder are mixed.

5. The method of preparing a graphite boat from lignin-rich plants according to claim 1, wherein the step of dehydrating the preformed boat and then sintering to obtain a shaped carbonaceous boat comprises:

and (3) dehydrating the preformed carrier boat at 100-200 ℃, loading the dehydrated preformed carrier boat into a sintering furnace, raising the pressure of the sintering furnace to 1.1-1.3Mpa, maintaining the pressure unchanged, raising the temperature to 600-1200 ℃, preserving the heat for 120-240 minutes, and then cooling and releasing the pressure to obtain the formed carbon carrier boat.

6. The method of preparing a graphite boat from lignin-rich plants according to claim 1, wherein the pitch powder has a particle size of 0.1-2mm.

7. The method of preparing a graphite boat from lignin-rich plants according to claim 1, wherein the binder is a glutinous rice binder.

8. The method of preparing a graphite boat from lignin-rich plants according to claim 7, wherein the method of preparing the glutinous rice binder comprises the steps of:

adding 9-10 kg of water into each kg of glutinous rice, adding water into the glutinous rice, placing into a container with 3000 rpm rotary blades, heating to 100deg.C, stopping heating, and simultaneously starting the rotary blades to operate for 1 min; stopping heating when the temperature is heated to 100 ℃ again, and simultaneously starting the rotary blade to run for 1 minute; and the sticky rice adhesive is obtained after 10-12 times of round trip.