CN109250709B - Production system for preparing graphene by using low-layer graphene oxide - Google Patents
Production system for preparing graphene by using low-layer graphene oxide Download PDFInfo
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- CN109250709B CN109250709B CN201811494486.3A CN201811494486A CN109250709B CN 109250709 B CN109250709 B CN 109250709B CN 201811494486 A CN201811494486 A CN 201811494486A CN 109250709 B CN109250709 B CN 109250709B
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Abstract
The invention provides a production system for preparing graphene by using low-layer graphene oxide. The production system comprises a graphene oxide purification device, a low-layer graphene oxide preparation device and a reduction device, wherein the graphene oxide purification device comprises a first feeding hole, a tank body, a first partition plate, a second partition plate, an ultrasonic generation unit and a first discharging hole; the low-layer graphene oxide preparation device is used for freeze drying the purified graphene obtained by the graphene oxide purification device and comprises a hydrogel forming unit, a low-temperature drying unit and a conveying mechanism; the reduction device comprises a bin, a traveling mechanism, a reaction unit and an atmosphere control unit, wherein the bin is used for reducing the graphene oxide with the second layer number obtained by the low-layer graphene oxide preparation device. The system disclosed by the invention is simple in structure and high in production efficiency, and graphene oxide passes through the reaction unit by virtue of self gravity, so that continuous production of graphene can be realized.
Description
Technical Field
The invention relates to the technical field of graphene preparation, in particular to a production system for preparing graphene by using low-layer graphene oxide.
Background
At present, the mainstream graphene preparation method comprises a mechanical stripping method, a redox method, an epitaxial growth method, a chemical vapor deposition method and the like, wherein the redox method is the most commonly used method for industrial production due to the advantages of low cost, simple production equipment, maximum single-time yield, concentrated product layer number, uniform transverse dimension and the like. On one hand, in the process of oxidation intercalation, the crystal structure of the graphene prepared by the redox method is easily damaged, so that the internal defects of the graphene are increased, and the performance of the graphene is greatly influenced; on the other hand, a large amount of metal and nonmetal impurities still exist in the graphene produced by the oxidation-reduction method, which further influences the large-scale development and application of the graphene.
Disclosure of Invention
In view of the deficiencies in the prior art, it is an object of the present invention to address one or more of the problems in the prior art as set forth above. For example, it is an object of the present invention to provide a graphene production system capable of producing a low impurity content by virtue of self-gravity through a reaction zone.
In order to achieve the above object, the present invention provides a production system for preparing graphene using a low-layer graphene oxide, which may include a graphene oxide purification apparatus, a low-layer graphene oxide preparation apparatus, and a reduction apparatus, wherein,
the graphene oxide purification device comprises a first feed inlet, a tank body, a first partition plate, a second partition plate, an ultrasonic generation unit and a first discharge outlet, wherein the first partition plate and the second partition plate are arranged in the tank body along the cross section of the tank body so as to divide the tank body into a reaction area, a filtering area and a collecting area which are sequentially distributed from top to bottom; the first feed port is arranged at the upper part of the tank body and communicated with the reaction zone, so that a purification object, a complexing agent and an acidic solution enter the reaction zone through the feed port, and the purification object comprises graphene oxide with a first layer number and impurity ions combined on functional groups; the first discharge hole is formed in the side wall of the tank body and located above the second partition plate so as to discharge purified graphene oxide deposited on the filtering component, and the purified graphene oxide is graphene oxide with a first layer number; the ultrasonic generating unit is arranged in the reaction zone to provide an ultrasonic environment for the reaction zone so as to fully perform the complex reaction;
the graphene oxide preparation device with the low layer number comprises a hydrogel forming unit, a low-temperature drying unit and a conveying mechanism, wherein the hydrogel forming unit is provided with a dispersing groove, the dispersing groove can receive water and purified graphene oxide discharged from the first discharge hole and disperse the purified graphene oxide in the water to form graphene oxide hydrogel; the low-temperature drying unit is provided with a temperature control unit, a pressure control unit and a cold drying cavity, wherein the cold drying cavity is formed by a shell and is provided with a second feeding hole, a second discharging hole and a cavity body, the temperature control unit is used for controlling the temperature in the cavity body to be not higher than-50 ℃ and controlling the temperature change in the whole cavity body to be not more than +/-4 ℃, and the pressure control unit is used for controlling the pressure in the cavity body to be lower than 1 atmosphere and controlling the pressure change in the whole cavity body to be not more than +/-100 Pa; the conveying mechanism is provided with a conveying member penetrating through the cold dry cavity and a speed regulating mechanism capable of regulating the advancing speed of the conveying member, the conveying member is used for receiving the graphene oxide hydrogel formed by the hydrogel forming unit and enabling the graphene oxide hydrogel to pass through the whole cold dry cavity so as to obtain graphene oxide with a second layer number from the second discharging hole, and the second layer number is smaller than the first layer number;
the reduction device can comprise a reaction unit and an atmosphere control unit, wherein the reaction unit comprises an ith reaction zone and an nth reaction zone which are sequentially connected in the vertical direction, the reaction unit is arranged to be capable of receiving the graphene oxide with the second layer number and enabling the graphene oxide with the second layer number to sequentially undergo the reaction of the ith reaction zone and the nth reaction zone of the reaction unit under the action of self gravity, n is a natural number and is not less than 2, and i takes all natural numbers less than n; the atmosphere control unit comprises a temperature control mechanism and a vacuum control mechanism which are matched with each other, wherein the temperature control mechanism is set to control the temperature of the nth reaction zone to be TnAnd controlling the temperature of the i-th reaction zone to be TiWherein，Ti＝w1·i/n·Tn，w1T is selected from 0.80 to 1.20nOver 1250 ℃; the vacuum control mechanism is arranged to control the pressure of the nth reaction zone to be PnAnd controlling the pressure of the ith reaction zone to be PiWherein P isi＝(P0-Pn)·(1-i/n)，P0Denotes 1 standard atmospheric pressure, PnIs 30Pa to 500 Pa.
Compared with the prior art, the invention has the beneficial effects that:
(1) the system can effectively separate the graphene oxide from impurity ions, can improve the thoroughness of graphene oxide purification, and has the advantages of high purification efficiency, low cost, simple structure, convenience in use and transportation and small occupied area;
(2) the freeze drying process for treating the graphene oxide by using the system provided by the invention does not damage the structure of the graphite oxide sheet layer, so that functional groups are well preserved, and the graphite oxide after freeze drying is not easy to agglomerate; the layer-to-layer spacing of the graphene oxide sheets after freeze drying is larger than that of the graphene oxide product dried by other drying methods, and the graphene oxide product has more excellent dispersing performance, fewer layers and larger specific surface area;
(3) by utilizing the system, the low-layer graphene oxide is subjected to reaction in the reaction zone by virtue of self gravity through setting different temperature and pressure areas, so that the graphene oxide can be pretreated, and the production efficiency of the graphene can be improved;
(4) the system provided by the invention makes full use of the characteristic of high melting point of graphene, removes metal and nonmetal impurities in the graphene at high temperature, removes a large amount of oxygen-containing functional groups carried by graphene oxide, and can repair SP (SP) caused by the graphene oxide in the preparation process3Hybridization defects, namely graphene with low impurity content, few structural defects and excellent comprehensive performance can be produced;
(5) the system disclosed by the invention is simple in structure and high in production efficiency, and can realize continuous production of graphene.
Drawings
The above and other objects and features of the present invention will become more apparent from the following description taken in conjunction with the accompanying drawings, in which:
fig. 1 shows a schematic diagram of a graphene oxide purification apparatus in a low impurity content graphene continuous production system according to an exemplary embodiment of the present invention;
fig. 2 shows a schematic diagram of a reduction apparatus in a low impurity content graphene continuous production system according to an exemplary embodiment of the present invention.
Illustration of the drawings:
10-a first feed port, 11-a first sub-feed port, 12-a second sub-feed port; 20-a reaction zone, 21-an ultrasonic generator, 22-a first partition plate; 30-a filtering area, 31-a second clapboard, 32-a first discharge hole, 33-an ICP ion concentration detector, 34-a buffer layer, 40-a collecting area, 41-a liquid discharge hole and 42-a vacuum pump.
Detailed Description
Hereinafter, a production system for preparing graphene using a low-layer number of graphene oxide according to the present invention will be described in detail with reference to the accompanying drawings and exemplary embodiments.
Fig. 1 shows a schematic diagram of a graphene oxide purification apparatus in a low impurity content graphene continuous production system according to an exemplary embodiment of the present invention; fig. 2 shows a schematic diagram of a reduction apparatus in a low impurity content graphene continuous production system according to an exemplary embodiment of the present invention.
In an exemplary embodiment of the production system for preparing graphene using a low-layer graphene oxide according to the present invention, the production system may include a graphene oxide purification apparatus, a low-layer graphene oxide preparation apparatus, and a reduction apparatus.
In an exemplary embodiment of the present invention, as shown in fig. 1, the graphene oxide purification apparatus may be an integrated apparatus. The purification device comprises a tank body, wherein a first feeding hole 10 is formed in the top of the tank body, and the first feeding hole 10 comprises a first sub-feeding hole 11 and a second sub-feeding hole 12; the tank body is divided into a reaction zone 20, a filtering zone 30 and a collecting zone 40 by a first partition plate 22 and a second partition plate 31 which are arranged transversely from top to bottom in sequence. An ultrasonic generator 21 is provided in the reaction zone 20. The first partition 22 is provided with an openable member, and a metal coarse filter screen (not shown) is provided at an opening of the openable member. The second separator 31 may include a filter member (not shown). The bottom of the filtering zone 30 is provided with a first discharge port 32, and the first discharge port 32 is provided with an ICP ion concentration detector 33. Also included in the filtration zone 30 is a buffer layer 34 disposed over the second separator plate. The collection area 40 is provided at the bottom thereof with a liquid discharge port 41 and a vacuum pump 42. The openable and closable member of the first partition 22 connects the reaction zone 20 to the filtration zone 30, and the filter member of the second partition 31 connects the filtration zone 30 to the collection zone 40.
The graphene oxide containing impurities and having a first layer number can enter from a first sub-feed opening 11, and the complexing agent and the dilute hydrochloric acid can enter from a second sub-feed opening 12; complexing agent and impurity heavy metal ions contained in the graphene oxide under acidic condition, and then allowing the complex, the graphene oxide with smaller size and the impurity ions to enter the filtering area 20 through the openable component on the first partition plate 22; buffer protection layer 34 can slow down the impact of ultrasonic wave to the membrane structure in the second baffle 31 filtering component, because the effect of vacuum filtration system (the annular shape of falling U cavity in vacuum pump 42 and collection region), the complex is filtered to collection region 30 with impurity ion under the negative pressure effect, the less oxidized graphene of size can purify, can flow out from first discharge gate 32, the oxidized graphene residual ion concentration that has the first number of layers after accessible ICP ion concentration detector 33 detects the purification, and the waste liquid that contains complex and impurity acid radical ion can flow out from liquid discharge gate 41.
The purified graphene oxide with the first layer number is obtained at the first discharge hole of the purification device, and is detected by the ICP ion concentration detector 33, and the detection result shows that the weight percentage of impurity ions on the purified graphene oxide with the first layer number is below 0.005%, and the impurity ion removal rate is above 99%.
In an exemplary embodiment of the present invention, the low-layer graphene oxide preparation apparatus is capable of receiving the graphene oxide purified by the graphene oxide purification apparatus and performing a freeze-drying process on the graphene oxide. The preparation device of the graphene oxide with the low layer number can be composed of a hydrogel forming unit, a low-temperature drying unit and a conveying mechanism.
The hydrogel-forming unit has dispersion grooves. The dispersion tank can receive the purified graphene oxide with the first layer number and water discharged from the first discharge hole in the graphene oxide purification device, and disperse the purified graphene oxide with the first layer number in water to form graphene oxide hydrogel. For example, the dispersion tank may have a tank body, a second feed port disposed above the tank body, and a second discharge port disposed at a side or bottom of the tank body. The second charging opening is used for adding the purified graphene oxide with the first layer number and water as raw materials. Here, the first layer number may be ten to several tens of layers, for example, 20 to 30 layers. And the second discharge hole is used for discharging the graphene oxide hydrogel. In addition, the hydrogel-forming unit may further have an ultrasound generating mechanism. The ultrasonic generating mechanism can transmit ultrasonic waves to the dispersion tank to form ultrasonic oscillation on the graphene oxide in the water of the dispersion tank, so that the dispersion effect is enhanced.
The purified graphene oxide having the first layer number can be dispersed in water by the dispersion tank, and a graphene oxide hydrogel can be formed. The graphene oxide as a raw material contains an oxygen-containing functional group. For example, the graphene oxide having the first layer number may be prepared by intercalating graphite with protonic acid. In the dispersing process, the dispersing effect is preferably further enhanced by ultrasonic dispersion, so that water molecules fully enter a lamellar structure or folds of the graphene oxide, or are combined with functional groups on the surface of the graphene oxide to form hydrated ions, thereby forming the graphene oxide hydrogel. The graphene oxide hydrogel has a structure in which water molecules are bonded in its own sheet or wrinkle of graphene oxide. The solid content of the graphene oxide hydrogel can be 0.1-50 wt%.
The low-temperature drying unit is provided with a temperature control unit, a pressure control unit and a cold drying cavity. Wherein, the cold dry chamber is enclosed by the casing and has feed inlet, discharge gate and the cavity of determining length. The cavity of the cold dry cavity can be in a U shape or a ring shape with a gap so as to save space. However, the present exemplary embodiment is not limited thereto, and the cavity of the cold dry chamber may also be S-shaped or linear. The feeding hole and the discharging hole are respectively arranged at the front end and the rear end of the cavity along the advancing direction of the materials, and are respectively provided with a valve capable of opening and closing so as to separate the cavity from the outside. The temperature control unit can be a refrigerator which is connected with the cold dry cavity and has a constant temperature control function, and the refrigerator can control the temperature in the cavity of the cold dry cavity to be not higher than-50 ℃ and control the temperature change in the cavity of the whole cold dry cavity to be not more than +/-4 ℃. And the pressure control unit can be a vacuum pump which is connected with the cold dry cavity and has a constant pressure control function, and the vacuum pump can control the pressure in the cavity of the cold dry cavity to be lower than 1 atmosphere and control the pressure variation in the whole cavity to be not more than +/-100 Pa.
Further, the temperature control unit can control the temperature in the cavity within a range of-55 to-65 ℃ and control the temperature change in the whole cavity to be not more than +/-2 ℃, and the pressure control unit can control the pressure in the cavity to be 10 to 100Pa and control the pressure change in the whole cavity to be not more than +/-10 Pa, so that the atmospheric environment with relatively stable low temperature and relatively stable vacuum degree can be obtained.
The water molecules can be changed into ice molecules through the coordination of the temperature control unit and the pressure control unit, and the lamellar structure of the graphite is further widened through volume expansion; and the ice can be desublimated and volatilized at low temperature and low pressure, the temperature is low, the entropy value is low, the strutted structure of the graphene oxide can be maintained, and the prepared graphene oxide material has good dispersibility and large specific surface area. Moreover, the relatively constant low temperature (for example, not higher than-50 ℃ and the temperature variation in the cavity of the whole cold dry cavity is controlled not to exceed +/-4 ℃) and the relatively constant vacuum degree (for example, lower than 1 atmosphere and the pressure variation in the whole cavity is controlled not to exceed +/-100 Pa) are beneficial to relatively stabilizing the condensation speed and degree of water molecules, so that the 'opening' effect on the graphene oxide layer is stable; but also the ice molecule desublimation speed and degree are relatively stable, thus being beneficial to avoiding local defects caused by the local stress of the graphene oxide layer to a certain degree. Furthermore, the temperature control unit and the pressure control unit are used for controlling the atmosphere of the cold drying cavity to be within the range of-55 to-65 ℃, the temperature change in the whole cavity is controlled not to exceed +/-2 ℃, the pressure is controlled to be 10 to 100Pa, the pressure change in the whole cavity is controlled not to exceed +/-10 Pa, the condensation speed and the degree of water molecules are further stabilized, and the opening effect of the graphene oxide layer is stabilized; but also the ice molecule desublimation speed and degree are further stabilized, thereby further avoiding local defects caused by the local stress of the graphene oxide layer.
The conveying structure is provided with a conveying member penetrating through the cold dry cavity and a speed regulating mechanism capable of regulating the traveling speed of the conveying member. The conveyor is capable of receiving the graphene oxide hydrogel formed by the hydrogel-forming unit and advancing the graphene oxide hydrogel through the entire cold dry cavity to finally obtain a second number of layers of graphene oxide from the discharge outlet of the cold dry cavity. The conveyor may be a conveyor belt. The speed regulating mechanism can control the conveyor belt to pass through the cold drying cavity at a preset speed at a uniform speed. The second number of layers is less than the first number of layers. The second number of layers may have a significant reduction compared to the first number of layers. Here, the second number of layers may be 1/3-1/6 of the first number of layers. For example, the second number of layers may be 5 to 7.
In another exemplary embodiment of the present invention, the apparatus for preparing graphene oxide with a low number of layers may further include a buffer region on the basis of the structure of the above exemplary embodiment. Specifically, the buffer region may be connected to the second discharge port, so as to appropriately raise the temperature of the graphene oxide entering the buffer region from the second discharge port, thereby enabling the graphene oxide as a product to be suitable for a room temperature environment or a subsequent treatment process. For example, the length of the buffer area may be 1.5 to 4 meters, but the present exemplary embodiment is not limited thereto.
In another exemplary embodiment of the present invention, the preparation apparatus of graphene oxide with a low number of layers may further include a pretreatment region on the basis of the structure of the above exemplary embodiment. In particular, the pretreatment zone may be connected to said second inlet and itself crossed by said conveyor. The pretreatment area is provided with a cooling component, so that the graphene oxide hydrogel entering the pretreatment area through the conveying member can be subjected to appropriate cooling treatment, and the temperature of the graphene oxide hydrogel is reduced. For example, the temperature within the pretreatment zone can be stably maintained between 1/6 and 3/5 of the temperature within the cavity. Through the setting in preliminary treatment district, can carry out first cooling to oxidation graphite alkene, be convenient for control cooling process, and do benefit to the operation. For example, the length of the pre-treatment region may be 1.5 to 4 meters, but the present exemplary embodiment is not limited thereto.
In an exemplary embodiment of the invention, the apparatus for preparing graphene oxide with a low number of layers may obtain the completely dried graphene oxide with a second number of layers by coordinately controlling the length of the cavity of the cold dry chamber, the temperature and pressure in the cold dry chamber, and the speed of the conveying member. Specifically, when the preparation device of the present invention is designed, the temperature and pressure in the freeze-drying chamber can be determined according to the above-mentioned relevant requirements, and then the length of the chamber and the operation speed of the conveying member can be determined according to the requirements of the field, etc., so as to ensure that the graphene oxide hydrogel conveyed and operated by the conveying member through the freeze-drying chamber can fully complete the processes of low-temperature freezing and desublimation drying. For example, the cavity length of the cold dry cavity may be 10-20 meters, but the present exemplary embodiment is not limited thereto.
In an exemplary embodiment of the present invention, as shown in fig. 2, the reduction apparatus may include a reaction unit and an atmosphere control unit.
The reaction unit comprises n reaction zones which extend in the vertical direction. And taking the graphene oxide with the second layer number, which is prepared by the low-layer graphene oxide preparation device, as a raw material, sequentially passing the graphene oxide with the second layer number through the ith reaction zone of the reaction unit from the 1 st reaction zone of the reaction unit under the action of gravity of the graphene oxide with the second layer number in sequence until the nth reaction zone finishes the reaction, and collecting the graphene. Wherein n is a natural number and is more than or equal to 2, and i is all natural numbers less than n.
The atmosphere control unit comprises a temperature control mechanism and a vacuum control mechanism which are matched with each other. The temperature control mechanism is used for controlling the temperature of the ith reaction zone to be TiControlling the temperature of the n-th reaction zone to be Tn. The T isi＝w1·i/n·Tn，w1Can be selected from 0.80 to 1.20. For example, w1May take on a value of 0.9. The vacuum control mechanism can control the pressure of the ith reaction zone to be PiControlling the pressure of the n-th reaction zone to be Pn. The P isi＝(P0-Pn)·(1-i/n)，P0Indicating 1 standard atmosphere.
The T isnMay be 1250 ℃ or higher, further, the TnMay be 1700 ℃ to 2800 ℃. The P isnThe pressure may be 30Pa to 500 Pa. Further, said PnThe pressure may be 60Pa to 100 Pa. Further, said PnThe pressure may be 85Pa to 95 Pa. Said w1Can be selected from 0.85 to 1.14, for example, w1May be taken to be 0.95. Set temperature TnThe benefit of being above 1250 c is that if the temperature is below 1250 c, it is not conducive to volatilization of the impurities, and the melting and boiling points of some of the impurities may not be reached. For example, the set temperature may be 1250 ℃ to 2500 ℃. If the temperature set by the invention is higher than 2800 ℃, the loss of the furnace can be serious, the energy consumption is high and the cost is high. Further, the temperature TnMay be 2200 deg.c. Since 2200 ℃ is the graphitization temperature of the carbon material, the method is also beneficial to repairing the self defects of the graphene oxide. Setting the pressure PnThe advantage of 30 Pa-500 Pa is that under the pressure and vacuum degree, the melting point and the boiling point of impurities contained in the graphene oxide are lower, and the impurities are easier to volatilize and remove.
In an exemplary embodiment of the present invention, the reduction apparatus may further include a speed regulating unit. Since the graphene oxide having the second layer number passes through the reaction zone by its own weight. After the height of the reaction zone is set to a fixed value, the reaction time of the graphene oxide with the second layer number in each zone cannot be effectively controlled, which is not favorable for the reaction of the graphene oxide with the second layer number in the reaction zone. Therefore, in order to effectively control the reaction time of the graphene oxide having the second layer number in each reaction zone, it is necessary to control the falling rate of the graphene oxide having the second layer number. The speed regulating unit can be used for blowing inert gas flow into the reaction zone. When the descending speed of the graphene oxide with the second layer number is too high and the reaction needs to be carried out in a certain reaction zone for a long time, the direction of the blowing gas of the speed regulating unit can be set to be opposite to the descending direction of the graphene oxide with the second layer number, so that the rapid descending of the graphene oxide with the second layer number is prevented. If the graphene oxide with the second layer number falls in an accelerated manner and the reaction time of the graphene oxide with the second layer number in a certain reaction zone is shortened, the direction of the gas blowing of the speed regulating unit is set to be the same as the direction of the falling of the graphene oxide with the second layer number, and the falling of the graphene oxide with the second layer number is accelerated.
The oxygen functional group contained in the purification target may include one or more functional groups of a carboxyl group, a hydroxyl group, a carbonyl group, an ether bond, and an epoxy group. Under the conditions of high temperature and pressure, the functional groups can be decomposed into carbon dioxide and water, and oxygen-containing functional groups in the graphene oxide can be effectively removed. Theoretically, the functional group can be removed at a temperature of 1000 ℃ and under the vacuum environment of the present invention, but the temperature set by the present invention should be higher than 1250 ℃ because the temperature for removing impurities is high. Of course, the oxygen-containing functional group of the present invention is not limited thereto, and can be decomposed into carbon dioxide and water at the temperature and pressure of the present invention.
As described above, the purification target may include at least one impurity selected from manganese, iron, potassium, sodium, sulfur, and silicon. The complexing agent used in the purification process may combine with metal impurities in the impurities to remove the metal impurities, e.g., manganese, iron, potassium, sodium, etc. At the moment, the addition amount of the complexing agent is 1.0-1.2 times of the theoretical amount of the complexing agent capable of reacting with impurities. Of course, the metal impurities that can be removed by complexation are not limited thereto, and for example, heavy metal impurities or other impurities that can bind to the complexing agent may be used. After purification to remove a part of impurities, in the reduction step, metallic and non-metallic impurities, such as manganese, iron, potassium, sodium, sulfur, silicon, etc., can be removed under a high temperature and low pressure environment. At high temperature, the melting point and the boiling point of metal impurities and nonmetal impurities contained in the graphene oxide can be reached, and the graphene oxide can be separated from the graphene oxide in a gaseous state. Under certain low-pressure auxiliary conditions, the melting points and boiling points of metal impurities and non-metal impurities can be further reduced, and the metal impurities and the non-metal impurities contained in the graphene oxide can be easily removed through the set temperature and vacuum degree. Impurities contained in the raw materials are removed through the cooperation of the purification process and the high-temperature vacuum reaction process, oxygen-containing functional groups can be well removed under the high-temperature vacuum degree, and graphene with low impurity content can be obtained. In the existing method for preparing graphene, the content of the prepared graphene is generally more than 2000PPm, the content of iron and manganese elements in the low-impurity-content graphene prepared by the method can reach less than 20PPm, further less than 15PPm, and impurities such as nitrate ions, chloride ions and the like can be well removed.
In conclusion, the system provided by the invention can effectively separate the graphene oxide from impurity ions, and can improve the thoroughness of graphene oxide purification. The freeze drying process of the system for processing graphene oxide does not damage the structure of the graphite oxide sheet layer, functional groups are well preserved, and the graphite oxide after freeze drying is not easy to agglomerate. According to the system, the low-layer graphene oxide is subjected to reaction in the reaction zone by virtue of self gravity through setting different temperature and pressure areas, the graphene oxide can be pretreated, the production efficiency of the graphene can be improved, metal and non-metal impurities in the graphene can be removed, a large number of oxygen-containing functional groups carried by the graphene oxide can be removed, and SP (SP) caused in the preparation process of the graphene oxide can be repaired3Hybridization defects, and can produce graphene with low impurity content, few structural defects and excellent comprehensive performance.
Although the present invention has been described above in connection with exemplary embodiments, it will be apparent to those skilled in the art that various modifications and changes may be made to the exemplary embodiments of the present invention without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (9)
1. A production system for preparing graphene by using low-layer graphene oxide is characterized by comprising a graphene oxide purification device, a low-layer graphene oxide preparation device and a reduction device, wherein,
the graphene oxide purification device comprises a first feeding hole, a tank body, a first clapboard, a second clapboard, an ultrasonic generation unit and a first discharging hole, wherein,
the first clapboard and the second clapboard are arranged in the tank body along the cross section of the tank body so as to divide the tank body into a reaction area, a filtering area and a collecting area which are sequentially distributed from top to bottom, the first clapboard is provided with an openable component which can communicate the reaction area with the filtering area, and the second clapboard is provided with a filtering component which can realize solid-liquid separation;
the first feed port is arranged at the upper part of the tank body and communicated with the reaction zone, so that a purification object, a complexing agent and an acidic solution enter the reaction zone through the feed port, and the purification object comprises graphene oxide with a first layer number and impurity ions combined on functional groups;
the first discharge hole is formed in the side wall of the tank body and located above the second partition plate so as to discharge purified graphene oxide deposited on the filtering component, and the purified graphene oxide is graphene oxide with a first layer number;
the ultrasonic generating unit is arranged in the reaction zone to provide an ultrasonic environment for the reaction zone so as to fully perform the complex reaction;
the graphene oxide preparation device with the low layer number comprises a hydrogel forming unit, a low-temperature drying unit and a conveying mechanism, wherein,
the hydrogel forming unit is provided with a dispersion tank, and the dispersion tank is used for receiving water and the purified graphene oxide discharged from the first discharge hole and dispersing the purified graphene oxide in the water to form graphene oxide hydrogel;
the low-temperature drying unit is provided with a temperature control unit, a pressure control unit and a cold drying cavity, wherein the cold drying cavity is formed by a shell and is provided with a second feeding hole, a second discharging hole and a cavity, the temperature control unit is used for controlling the temperature in the cavity to be not higher than-55 ℃ and controlling the temperature change in the whole cavity to be not more than +/-4 ℃, and the pressure control unit is used for controlling the pressure in the cavity to be lower than 1 atmosphere and controlling the pressure change in the whole cavity to be not more than +/-100 Pa;
the conveying mechanism is provided with a conveying member penetrating through the cold dry cavity and a speed regulating mechanism capable of regulating the advancing speed of the conveying member, the conveying member is used for receiving the graphene oxide hydrogel formed by the hydrogel forming unit and enabling the graphene oxide hydrogel to pass through the whole cold dry cavity so as to obtain graphene oxide with a second layer number from the second discharging hole, and the second layer number is smaller than the first layer number;
the reduction device comprises a reaction unit and an atmosphere control unit, wherein,
the reaction unit comprises an ith reaction zone and an nth reaction zone which are sequentially connected in the vertical direction, the reaction unit is arranged to be capable of receiving the graphene oxide with the second layer number and enabling the graphene oxide with the second layer number to sequentially react with the ith reaction zone and the nth reaction zone of the reaction unit under the action of self gravity, n is a natural number and is not less than 2, and i takes all natural numbers less than n;
the atmosphere control unit comprises a temperature control mechanism and a vacuum control mechanism which are matched with each other, wherein the temperature control mechanism is set to control the temperature of the nth reaction zone to be TnAnd controlling the temperature of the i-th reaction zone to be TiWherein, Ti＝w1·i/n·Tn，w1T is selected from 0.80 to 1.20nOver 1250 ℃; the vacuum control mechanism is arranged to control the pressure of the nth reaction zone to be PnAnd controlling the pressure of the ith reaction zone to be PiWherein P isi＝(P0-Pn)·(1-i/n)，P0Denotes 1 standard atmospheric pressure, Pn30Pa to 500 Pa;
the graphene oxide purification device further comprises a buffer protection layer arranged between the first partition plate and the filtering component, and the buffer protection layer can absorb and buffer ultrasonic waves generated by the ultrasonic generation unit so as to protect the filtering component.
2. The system for producing graphene by using low-layer graphene oxide according to claim 1, wherein the graphene oxide purification device further comprises an ion concentration detection unit disposed at the first discharge port to detect the concentration of impurity ions in the purified graphene oxide.
3. The system according to claim 2, wherein the graphene oxide purification apparatus further comprises a material returning unit having a controller and a material conveying member, the controller is connected to the ion concentration detection unit and determines whether to start the material conveying member according to a detection result of the ion concentration detection unit, and the material conveying member is capable of supplying the purified graphene oxide discharged from the first discharge port to the first feed port.
4. The production system for preparing graphene by using the low-layer graphene oxide according to claim 1, wherein the low-layer graphene oxide preparation device further comprises a buffer area connected with the second discharge port, and the buffer area can heat the graphene oxide entering the buffer area from the second discharge port.
5. The production system for preparing graphene by using the low-layer graphene oxide according to claim 1, wherein the low-layer graphene oxide preparation device further comprises a pretreatment region connected with the second feeding hole and penetrated by the conveying member, and the pretreatment region can perform cooling treatment on the graphene oxide hydrogel entering the pretreatment region so as to reduce the temperature of the graphene oxide hydrogel and keep the temperature in the cavity at 1/6-3/5.
6. The system for producing graphene oxide according to claim 1, wherein the graphene oxide preparation device obtains the completely dried graphene oxide with the second layer number by coordinately controlling the length of the cavity of the cold dry chamber, the temperature and pressure in the cold dry chamber, and the speed of the conveying member.
7. The system for producing graphene by using the low-layer graphene oxide according to claim 1, wherein the temperature control unit of the low-layer graphene oxide production device controls the temperature in the cavity to be within a range of-55 ℃ to-65 ℃ and controls the temperature variation in the whole cavity to be not more than +/-2 ℃.
8. The production system for preparing graphene by using the low-layer graphene oxide according to claim 1, wherein a pressure control unit of the low-layer graphene oxide preparation device controls the pressure in the cavity to be 10-100 Pa and controls the pressure variation in the whole cavity to be not more than +/-10 Pa.
9. The system for producing graphene by using the low-layer graphene oxide according to claim 1, wherein the reduction device further comprises a speed regulating unit, and the speed regulating unit is used for blowing air flow into the reaction unit to control the descending speed of the graphene oxide in the reaction unit.
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