Carbon nanotube production device, carbon nanotubes prepared by pyrolyzing plastic and preparation method thereof

Abstract

The application relates to the field of carbon nanotube preparation, and particularly discloses a carbon nanotube production device, carbon nanotubes prepared by pyrolysis of plastics and a preparation method thereof. The carbon nanotube production device comprises a multi-temperature-zone reaction furnace provided with multiple communication reaction chambers, and the multiple reaction chambers are located on the same horizontal plane. A method for preparing carbon nanotubes by pyrolysis of plastics comprises the following preparation steps: waste plastic pretreatment, catalyst addition, CVD preparation, and the low-temperature reaction chamber and the high-temperature reaction chamber are arranged on the same horizontal plane. The technical scheme adjusts the structure of the device for preparing carbon nanotubes, improves the carbon nanotube production efficiency, and further improves the conversion rate of the carbon nanotube material prepared by pyrolysis of waste plastics and gas phase deposition.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of carbon nanotube preparation, and in particular to a carbon nanotube production device, a carbon nanotube prepared by pyrolyzing plastic and a preparation method thereof. BACKGROUND

[0002] As a kind of nanomaterial, carbon nanotube has excellent electrical conductivity, thermal conductivity and mechanical properties, and is applied in many fields such as chemical industry, aerospace and medical treatment. In recent years, due to the obvious performance advantages of carbon nanotube used in lithium battery conductive agent, the market demand for carbon nanotube increases year by year. Industrialized production of carbon nanotube mainly adopts chemical vapor deposition method, which realizes preparation of carbon nanotube material by cracking carbon-containing gas such as propylene and ethylene at high temperature and depositing carbon on the surface of nanometer catalyst. Many plastics are actually polymers of such olefins. The preparation of carbon nanotube from waste plastics not only reduces the production cost of carbon nanotube, but also opens up a new technical route for waste plastic recycling.

[0003] However, due to the complexity of waste plastics, high requirements are put forward for the selection of raw materials and catalysts in the early stage and the control of the reaction process. The Chinese invention patent with publication number CN112408364A discloses a method for preparing carbon nanotube by catalytic pyrolysis of waste thermosetting plastic. The method uses a core-shell catalyst, uses waste thermosetting plastic as raw material, and produces pyrolysis gas in a two-stage fixed bed reactor to form carbon nanotube on the surface of the catalyst. The whole process is to prepare carbon nanotube by controlling the temperature of the reactor, which not only realizes the recycling of waste plastics, but also produces high value-added carbon nanotube. However, the scheme of cracking waste plastics in a two-stage reactor to prepare carbon nanotube material by gas phase deposition is complex, the carbon conversion efficiency is low, and the thermosetting plastic contains oxygen elements, which will greatly affect the yield of carbon nanotube in the preparation of carbon nanotube. SUMMARY

[0004] In order to improve the defect that the conversion rate of carbon nanotube material prepared by cracking waste plastics to prepare carbon nanotube by gas phase deposition is not good, the present application provides a carbon nanotube production device, a carbon nanotube prepared by pyrolyzing plastic and a preparation method thereof.

[0005] In a first aspect, the present application provides a carbon nanotube production device, which adopts the following technical scheme:

[0006] A carbon nanotube production device, comprising a multi-temperature zone reaction furnace, wherein the multi-temperature zone reaction furnace is provided with a plurality of connected reaction chambers, and the plurality of reaction chambers are located on the same horizontal plane.

[0007] By adopting the technical scheme, the device structure for producing carbon nanotubes is further adjusted, a plurality of connected reaction chambers are arranged on the same horizontal plane, and the defects of low continuous production efficiency caused by the traditional two-stage method of hanging waste plastic pyrolysis production CVD are effectively improved. At the same time, the plurality of connected reaction chambers are arranged on the same horizontal plane, that is, the condensing equipment does not need to be arranged between the two regions to continuously produce carbon nanotubes, the production efficiency of the carbon nanotubes is improved, and the conversion rate of the carbon nanotube material prepared by pyrolyzing waste plastics to gas phase deposition is further improved.

[0008] Preferably, the carbon nanotube production device further comprises:

[0009] A feeding bin is arranged at one end of the multi-temperature zone reaction furnace, and a feeding chamber connected with the reaction chamber is arranged in the feeding bin.

[0010] A discharging bin is arranged at the other end of the multi-temperature zone reaction furnace and is provided with a discharging chamber connected with the reaction chamber.

[0011] By adopting the technical scheme, the feeding bin and the discharging bin are arranged, and in the actual production process, the materials in the carbon nanotube production device can be effectively stored, added and discharged, and the production efficiency is improved.

[0012] Preferably, the reaction chamber in the multi-temperature zone reaction furnace in the carbon nanotube production device is two, the two reaction chambers are a low-temperature reaction chamber and a high-temperature reaction chamber respectively, and the carbon nanotube production device further comprises:

[0013] A feeding device is arranged at one end in the feeding chamber and at the other end in the low-temperature reaction chamber, and the circulating feeding device is used to carry a container device to make the reaction device reciprocatingly move in the feeding chamber and the low-temperature reaction chamber.

[0014] By adopting the technical scheme, the feeding device is further arranged in the feeding chamber, the feeding device improves the problem that the materials in the carbon nanotube production device cannot be cyclically added in the production process and reduces the production efficiency, and the application further reduces the risk of oxygen element entering the device by the circulating feeding mode, thereby improving the conversion rate of the carbon nanotube production.

[0015] Preferably, the carbon nanotube production device further comprises:

[0016] A discharging device is arranged at one end in the discharging chamber and at the other end in the high-temperature reaction chamber, and the discharging device is used to carry a reaction container to make the reaction container reciprocatingly move in the discharging chamber and the high-temperature reaction chamber.

[0017] By adopting the technical scheme, the application further sets the circulating discharging device in the discharging chamber, which improves the discharging efficiency of the carbon nanotubes on one hand, and reduces the risk of the carbon nanotube production device entering oxygen elements in the production process on the other hand, thereby improving the conversion rate of the carbon nanotube production.

[0018] In a second aspect, the application provides a method for preparing carbon nanotubes by pyrolyzing plastics, which adopts the following technical scheme:

[0019] A method for preparing carbon nanotubes by pyrolyzing plastics, comprising the following preparation steps:

[0020] Preprocessing of waste plastics: taking waste plastics and washing and drying, crushing and collecting waste plastic particles and placing them in a low-temperature reaction chamber in a carbon nanotube production device;

[0021] Adding catalyst: adding catalyst to a high-temperature reaction chamber in the carbon nanotube production device and introducing protective gas;

[0022] CVD preparation: heating treatment of the low-temperature reaction chamber and the high-temperature reaction chamber, pyrolysis of the low-temperature reaction chamber and gas phase deposition of the high-temperature reaction chamber, and standing cooling, so that carbon nanotubes can be prepared; the low-temperature reaction chamber and the high-temperature reaction chamber are arranged on the same horizontal plane.

[0023] By adopting the technical scheme, the application selects waste plastics as the main raw material, and through heating treatment, the C-C bonds on the molecular chain of the waste plastics are randomly broken to generate a plurality of small molecule radicals. During the subsequent heat preservation process, hydrogen transfer and beta-breaking reactions occur, the generated radicals take hydrogen atoms from the molecular chain to convert into alkanes or alkenes, and the molecular chain lacking hydrogen atoms evolves into radicals, which eventually undergo recombination or disproportionation reactions to convert into small molecule gaseous carbon sources such as methane, ethylene, propylene and benzene. This part of the carbon source is first effectively adsorbed on the surface of the catalyst, and then further diffuses into the metal particles to form carbides until the surface of the catalyst is completely covered by carbon fragments, thereby completing the preparation process of the carbon nanotubes.

[0024] Meanwhile, the technical scheme of the application further cooperates with the device for preparing carbon nanotubes, on one hand, by arranging a plurality of communicating reaction chambers in the same horizontal plane, the defect that the continuous production efficiency of the traditional two-stage method of hanging waste plastics for cracking to produce CVD is low is effectively improved. On the other hand, the setting of the circulating feeding and discharging and the circulating discharging device can effectively reduce the risk of the device for preparing carbon nanotubes entering oxygen elements in the actual production process, thereby further improving the conversion rate of the carbon nanotube material prepared by cracking waste plastics for gas phase deposition.

[0025] Preferably, the size of the waste plastic particles is 50-100 mesh.

[0026] By adopting the above technical solution, the size of the waste plastic particles is further optimized, so that the cracking efficiency is improved, and the conversion rate of the carbon nanotube material is also improved.

[0027] Preferably, the temperature rising speed of the low-temperature reaction chamber is 5-30℃ / min, and the pyrolysis temperature is 250-650℃; the temperature rising speed of the high-temperature reaction chamber is 5-30℃ / min, and the pyrolysis temperature is 550-950℃.

[0028] By adopting the above technical solution, the holding temperature and the temperature rising rate of the low-temperature reaction chamber and the high-temperature reaction chamber are further optimized. On the one hand, the low-temperature reaction chamber maintains a good temperature rising rate and a suitable cracking temperature, which can effectively control the rate of forming carbon source gas by cracking waste plastics, so that the deposition efficiency and the conversion rate are maintained in the CVD process. On the other hand, the high-temperature reaction chamber maintains a stable temperature rising speed and a suitable pyrolysis temperature, which can improve the defect that the quality of the generated carbon nanotubes is reduced due to the aggregation and reconstruction of the catalyst particles caused by the sharp change of the temperature.

[0029] Preferably, the catalyst comprises Co 1-x M x / Al2O3 catalyst, and the M element in the Co 1-x M x / Al2O3 catalyst comprises any one of Fe, Ni and Mo.

[0030] By adopting the above technical solution, the composition of the catalyst material is further optimized. By selecting Fe, Ni and Mo elements as the catalyst active material, the conversion rate of preparing carbon nanotubes by catalytic cracking of waste plastics is further improved. Among them, the Mo element adopted in the present application has high catalytic activity and high carbon solubility, which can effectively inhibit the aggregation of catalyst particles and realize the control of the morphology and size of the catalyst particles. The Ni-based and Fe-based catalysts are more conducive to the breaking of C-C and C-H bonds, thereby also being more conducive to the polymer cracking and reforming reaction. Thus, the prepared carbon nanotubes have moderate length and smooth surface.

[0031] Meanwhile, the present application further optimizes the catalyst, which adopts Co combined with alumina as the carrier. Since the interaction between cobalt and the alumina carrier is strong, the combination of the M element doped as a catalyst is used, which reduces the diameter of the prepared CNTs and improves the conversion rate of the prepared CNTs.

[0032] Preferably, the Co 1-x M x / Al2O3 catalyst comprises Co 1-x Mx The mass ratio of the Co

[0033] By adopting the technical scheme, the Co 1-x M x / Al2O3 catalyst is prepared by adopting the following scheme:

[0034] Preferably, the Co 1-x M x / Al2O3 catalyst is prepared by adopting the following scheme:

[0035] The cobalt salt and the aluminum salt are dissolved in a solvent, and a mixed solution is collected by stirring and mixing;

[0036] The ammonium salt aqueous solution is stirred and mixed with the mixed solution, the pH is adjusted to 9-10, the precipitate is filtered, dried and calcined, and the Co 1-x M x / Al2O3 catalyst is prepared.

[0037] By adopting the technical scheme, the catalyst material is prepared by the coprecipitation method, and the catalyst material prepared by the coprecipitation method has a uniform and controllable particle size and a more excellent size structure, so that the prepared CNTs have good structural performance and conversion rate in the subsequent preparation process of the CNTs.

[0038] Preferably, the ammonium salt aqueous solution includes any one of an ammonium carbonate aqueous solution, an ammonium molybdate tetrahydrate / ammonium carbonate aqueous solution, an iron nitrate / ammonium carbonate aqueous solution or a nickel nitrate / ammonium carbonate aqueous solution.

[0039] Preferably, the mass ratio of the catalyst to the waste plastic particles is (0.005-1):1.

[0040] By adopting the technical scheme, the appropriate ratio between the catalyst material and the waste plastic particles is selected, which not only improves the defects of limited catalytic effect and poor catalytic effect of the catalyst material when the addition ratio of the catalyst material is too low, but also improves the problem that the catalyst is prone to agglomeration and thus reduces the catalytic activity when the addition ratio of the catalyst is too high. The appropriate addition ratio of the catalyst selected by the application enables the prepared carbon nanotube material to have good conversion rate.

[0041] Preferably, in the adding catalyst step, the protective gas is introduced at a rate of 0.5-1.5 L / min, and the protective gas is introduced from the low-temperature reaction chamber to the high-temperature reaction chamber.

[0042] Preferably, the CVD preparation step further comprises:

[0043] The rate of introduction of the protective gas during the temperature-increasing heating treatment and the temperature-maintaining pyrolysis process is 0.05-2 L / min.

[0044] After the temperature-maintaining pyrolysis is completed, the rate of introduction of the protective gas is adjusted again to 0.5-1.5 L / min.

[0045] By using the above technical solution, the rate of introduction of the protective gas is adjusted during the adding catalyst process, the temperature-increasing heating process, and the temperature-maintaining pyrolysis process, respectively. The rate of introduction of the protective gas is adjusted according to different situations, which can effectively improve the rate of deposition of the carbon source gas formed by decomposition on the surface of the catalyst during actual use, thereby optimizing the conversion rate of the carbon nanotube particles and improving the size structure of the carbon nanotube particles, and thus effectively improving the performance of the produced carbon nanotube particles.

[0046] In a second aspect, the present application provides a carbon nanotube prepared by the above-mentioned method for preparing carbon nanotubes from pyrolyzed plastics.

[0047] By using the above technical solution, the present application is prepared by selecting appropriate catalyst materials and assisted by the transversely arranged carbon nanotube particle production device, which effectively improves the conversion rate of CNTs, further improves the size structure and uniform and stable performance of CNTs, and makes the prepared CNTs have good electrical conductivity, thermal conductivity, and mechanical properties.

[0048] In summary, the present application has the following beneficial effects:

[0049] First, the present application selects waste plastics as the main raw material, and through heating treatment, the C—C bonds on the molecular chain of the waste plastics are randomly broken to generate a plurality of small molecule radicals. During the subsequent temperature-maintaining process, hydrogen transfer and β-scission reactions occur, the generated radicals take hydrogen atoms from the molecular chain to convert into alkanes or alkenes, and the molecular chain lacking hydrogen atoms evolves into radicals. Finally, the radicals undergo recombination or disproportionation reactions to convert into small molecule gaseous carbon sources such as methane, ethylene, propylene, and benzene. This part of the carbon source is first effectively adsorbed on the surface of the catalyst, and then further diffuses into the metal particles to form carbides until the surface of the catalyst is completely covered by carbon fragments, thereby completing the preparation process of the carbon nanotube.

[0050] Meanwhile, the technical scheme of the present application further adjusts the structure of the device for producing carbon nanotubes, and by arranging the waste plastic cracking region and the CVD region on the same horizontal plane, the defect of low continuous production efficiency caused by the traditional two-stage method of hanging waste plastic cracking to produce CVD is effectively improved. Meanwhile, by arranging the waste plastic cracking region and the CVD region on the same horizontal plane, i.e. without the need to arrange a condensing device between the two regions, carbon nanotubes can be continuously produced, the production efficiency of carbon nanotubes is improved, and the conversion rate of the carbon nanotube material prepared by cracking waste plastic to gas phase deposition is further improved.

[0051] Secondly, the present application further optimizes the proportion relationship of elements in the Co1-xMx / Al2O3 catalyst, and by forming a synergistic cooperation between the Co element, the M (Fe, Ni, Mo) element and the Al2O3 carrier, the particle size of the catalyst can be effectively controlled, the agglomeration and growth of the catalyst in the high-temperature pyrolysis process can be prevented, the catalyst can have high catalytic activity, and the finally produced CNTs can have good performance and conversion rate.

[0052] Thirdly, the present application prepares the catalyst material by the coprecipitation method, and since the catalyst material prepared by the coprecipitation method has a uniform and controllable particle size and has a more excellent size structure, the prepared CNTs can have good structural performance and conversion rate in the subsequent preparation process. BRIEF DESCRIPTION OF DRAWINGS

[0053] Fig. 1 is a structural schematic diagram of a carbon nanotube production device of an embodiment of the present application;

[0054] Fig. 2 is a cross-sectional view of a multi-temperature zone reaction furnace in the carbon nanotube production device of the embodiment of the present application;

[0055] Fig. 3 is a structural schematic diagram of a feeding hopper of the embodiment of the present application;

[0056] Fig. 4 is a structural schematic diagram of a discharging hopper of the embodiment of the present application;

[0057] Fig. 5 is a Raman spectrum diagram of the carbon nanotubes prepared in Example 1 of the present application;

[0058] Fig. 6 is a scanning electron microscope diagram of the carbon nanotubes prepared in Example 4 of the present application;

[0059] Fig. 7 is a transmission electron microscope diagram of the carbon nanotubes prepared in Example 5 of the present application.

[0060] Explanation of reference signs: 1, multi-temperature zone reaction furnace; 11, heating device; 2, feeding bin; 21, low-temperature reaction chamber; 22, feeding device; 23, operation through hole; 24, glove sleeve; 25, window through hole; 26, first protective gas delivery hole; 3, discharging bin; 31, high-temperature reaction chamber; 32, discharging device; 33, second tail gas output hole; 4, feeding hopper; 41, first storage protective gas inlet hole; 42, first storage protective gas outlet hole; 43, raw material storage protective gas device; 5, discharging hopper; 51, second storage protective gas inlet hole; 52, second storage protective gas outlet hole; 53, catalyst storage protective gas device; 6, access door; 7, first temperature insulation layer; 71, feeding through hole; 72, self-sealing temperature insulation door; 73, second protective gas delivery hole; 8, second temperature insulation layer; 81, first tail gas output hole; 9, protective gas inlet tank. DETAILED DESCRIPTION

[0061] The following will be described in detail with reference to the accompanying drawings. Figs. 1-7 The present application is further described in detail.

[0062] The present application discloses a carbon nanotube production device. Referring to Figs. 1-2 The carbon nanotube production device is provided with a multi-temperature zone reaction furnace 1, which is provided with two reaction chambers connected with each other, and the two reaction chambers are arranged in the same horizontal plane. The inner wall of the top of each reaction chamber is provided with a heating device 11, and the two heating devices 11 are independently arranged and can independently heat and keep warm. The multi-temperature zone reaction furnace 1 is provided with a feeding bin 2 and a discharging bin 3 at two ends respectively, and the feeding bin 2 and the discharging bin 3 are each provided with a feeding chamber and a discharging chamber for feeding or discharging. The reaction chamber near the feeding bin 2 in the multi-temperature zone reaction furnace 1 is a low-temperature reaction chamber 21, and the reaction chamber near the discharging bin 3 in the multi-temperature zone reaction furnace 1 is a high-temperature reaction chamber 31.

[0063] Referring to Figs. 1-2 In the low-temperature reaction chamber 21 and the feeding chamber, a feeding device 22 is arranged, which is an annular conveying structure, and a part of the annular conveying structure is arranged in the low-temperature reaction chamber 21 and the other part is arranged in the feeding chamber. The feeding device 22 is used for conveying the low-temperature reaction container along the feeding chamber to the high-temperature reaction chamber 31. When the low-temperature reaction container is conveyed to the low-temperature reaction chamber 21, the feeding device 22 is stationary, so that the low-temperature reaction container is kept warm at the fixed position. When the material in the low-temperature reaction container is kept warm and cracked, the feeding device 22 is restarted to convey the low-temperature reaction container from the low-temperature reaction chamber 21 to the feeding chamber again, and after being refilled with waste plastic particles, the low-temperature reaction container is circulated in the low-temperature reaction chamber 21 and the feeding chamber.

[0064] Referring to Figs. 1-2The shell surface of the feeding bin 2 and the discharging bin 3 is respectively provided with two pairs of operation through holes 23 through which the arms can pass. After being fixed at one end of the two glove sleeves 24 through each pair of operation through holes 23, an operation chamber for the hands is formed in the glove sleeves 24. The operation chamber is arranged in the feeding chamber and the discharging chamber respectively. Since one end of the two glove sleeves 24 is fixedly connected with the operation through holes 23 respectively, the operation chamber in the feeding bin 2 is not communicated with the feeding chamber, and the operation chamber in the discharging bin 3 is not communicated with the discharging chamber.

[0065] With reference to Figs. 1-2 Similarly, the discharging device 32 is arranged in the high-temperature reaction chamber 31 and the discharging chamber. The discharging device 32 and the feeding device 22 are both annular conveying structures. Part of the discharging device 32 is arranged in the high-temperature reaction chamber 31, and the other part is arranged in the discharging chamber. The discharging device 32 is used for conveying the high-temperature reaction container with catalyst to the high-temperature reaction chamber 31 along the discharging chamber. When the high-temperature reaction container is conveyed to the high-temperature reaction chamber 31, the discharging device 32 stops conveying and places the high-temperature reaction container in the high-temperature reaction chamber 31 for heat preservation and catalytic deposition treatment. When the production of carbon nanotubes is completed, the high-temperature reaction container containing the carbon nanotube product is conveyed to the feeding and discharging chamber from the high-temperature reaction chamber 31. When the high-temperature reaction container is conveyed to the discharging bin 3, the product formed in the high-temperature reaction container is collected through the glove sleeves 24, and the catalyst material is added again. The cycle is repeated, and the high-temperature reaction container can be circulated in the high-temperature reaction chamber 31 and the discharging chamber.

[0066] With reference to Figs. 3-4 The feeding hopper 4 and the discharging hopper 5 are arranged at the top end of the feeding bin 2 and the discharging bin 3 respectively. The feeding hopper 4 is filled with waste plastic particles as raw materials, and the discharging hopper 5 is filled with catalyst materials. The volume of the discharging hopper 5 is smaller than that of the feeding hopper 4. One end of the feeding hopper 4 is a material feeding pipe and extends into the feeding chamber, and one end of the discharging hopper 5 is a catalyst feeding pipe and extends into the discharging chamber. Valves are arranged on the catalyst feeding pipe and the material feeding pipe. By opening and closing the valves, the waste plastic particles and the catalyst materials can be added.

[0067] A first raw material storage protective gas inlet hole 41 and a first raw material storage protective gas outlet hole 42 are arranged on the outer wall surface of the raw material storage bin of the feeding hopper 4. One end of a raw material storage protective gas device 43 is connected to the first raw material storage protective gas inlet hole 41 to perform protective gas treatment on the feeding hopper 4. Air is discharged through the first raw material storage protective gas outlet hole 42, so that no air enters the feeding chamber during the feeding of the waste plastic particles.

[0068] Similarly, on the outer wall surface of the catalyst storage bin of the discharge hopper 5, a second storage protective gas inlet hole 51 and a second storage protective gas outlet hole 52 are also arranged respectively, the catalyst storage protective gas device 53 is connected to the second storage protective gas inlet hole 51, the discharge hopper 5 is treated with protective gas, and the air is discharged through the second storage protective gas outlet hole 52, so that no air enters the discharge chamber during the feeding of the catalyst material.

[0069] With reference to Figs. 1-2 On the top of the shell of the discharge bin 3 and the feeding bin 2, a window through hole 25 is arranged, and a transparent glass plate is sealed in the window through hole 25, which provides convenience when the discharge chamber and the feeding chamber are operated through the glove sleeve 24.

[0070] At the same time, on one side of the operation through hole 23 of the discharge bin 3 and the feeding bin 2 shell, a switchable access door 6 is arranged respectively, when the inside of the discharge bin 3 and the feeding bin 2 needs to be maintained, the access door 6 is opened, and in the actual production and use process, the access door 6 is closed to form a seal in the discharge chamber and the feeding chamber.

[0071] With reference to Figs. 1-2 A first temperature insulation layer 7 is arranged between the low-temperature reaction chamber 21 and the feeding chamber, and a second temperature insulation layer 8 is arranged between the high-temperature reaction chamber 31 and the discharge chamber, through the arrangement of the first temperature insulation layer 7 and the second temperature insulation layer 8, not only the internal temperature of the multi-temperature zone reaction furnace 1 is stable during the working process, but also the heat loss caused by the open multi-temperature zone reaction furnace 1 structure is effectively prevented, and the energy loss is reduced.

[0072] With reference to Figs. 1-2 Two feeding through holes 71 are arranged on the first temperature insulation layer 7, so that the feeding device circulates reciprocatingly in the feeding chamber and the low-temperature reaction chamber 21 through the feeding through holes 71; two discharge through holes are arranged on the second temperature insulation layer 8, for making the discharge device 32 circulate reciprocatingly in the discharge chamber and the high-temperature reaction chamber 31 through the two discharge through holes. On each feeding through hole 71, a self-sealing temperature insulation door 72 is arranged, the upper end of the self-sealing door is rotationally connected to the upper end of the feeding through hole 71, and the lower end of the self-sealing door is provided with a flexible sealing piece and abuts against the upper surface of the feeding device.

[0073] Similarly, on each discharge through hole, a self-sealing temperature insulation door 72 is arranged, the upper end of the self-sealing door is rotationally connected to the upper end of the discharge through hole, and the lower end of the self-sealing door is provided with a flexible sealing piece and abuts against the upper surface of the discharge device 32.

[0074] With reference to Figs. 1-2The shell of the feeding bin 2 is further provided with a first protective gas delivery hole 26, and the first temperature insulation layer 7 is provided with a second protective gas delivery hole 73. The one end of the protective gas inlet pipe is installed in the tank 9, and the protective gas inlet pipe passes through the first protective gas delivery hole 26 and the second protective gas delivery hole 73 in sequence and extends into the low-temperature reaction chamber 21. The protective gas inlet direction of the protective gas inlet pipe is coaxially arranged with the multi-temperature zone reaction furnace 1. The second temperature insulation layer 8 is provided with a first tail gas output hole 81 for discharging the tail gas generated during the CNTs preparation by CVD. The generated tail gas enters the discharging chamber from the high-temperature reaction chamber 31 through the first tail gas output hole 81 and is discharged from the second tail gas output hole 33 at the top of the shell of the discharging bin 3.

[0075] Preparation Example

[0076] Catalyst Preparation

[0077] Preparation Example 1

[0078] Catalyst 1: 1.27 kg of cobalt nitrate hexahydrate and 7.36 kg of aluminum nitrate nonahydrate were dissolved in 20 L of deionized water, and stirred until completely dissolved to obtain a nitrate solution;

[0079] Then 85 g of ammonium molybdate tetrahydrate was dissolved in 10 L of 2 mol / L ammonium carbonate aqueous solution, and the mixture was stirred and added dropwise into the nitrate solution at a dropwise adding speed of 50 mL / min. During the dropwise adding process, the mixture was stirred at a stirring speed of 1200 r / min to obtain a mixed solution;

[0080] After the dropwise adding was completed, the pH value of the mixed solution was adjusted to 9 by using 0.5 mol / L ammonia water. After complete precipitation, the precipitate was filtered out, dried in a 100°C oven, and collected. The dried material was calcined in a muffle furnace at 550°C for 2 h to obtain a powder. The powder was ground into fine powder by using a mortar and sieved through a 100 mesh sieve to obtain the catalyst 1.

[0081] Preparation Example 2

[0082] Catalyst 2: 750 g of cobalt nitrate hexahydrate, 1.09 kg of iron nitrate hexahydrate and 7.36 kg of aluminum nitrate nonahydrate were dissolved in 20 L of deionized water, and stirred until completely dissolved to obtain a nitrate solution;

[0083] Then 10 L of 3 mol / L ammonium carbonate aqueous solution was added dropwise into the nitrate solution at a dropwise adding speed of 50 mL / min. During the dropwise adding process, the mixture was stirred at a stirring speed of 1200 r / min to obtain a mixed solution;

[0084] After the dropping is completed, the pH value of the mixed solution is adjusted to 9.5 with 0.5 mol / L ammonia water, and after complete precipitation, the precipitate is filtered out, dried in a 100°C oven, the dried material is collected and placed in a muffle furnace, calcined at 450°C for 3h, the obtained powder is ground into fine powder with a mortar, and sieved through a 100 mesh sieve to prepare the catalyst 2.

[0085] Preparation Example 3

[0086] Catalyst 3: 1.2 kg of cobalt nitrate hexahydrate, 300 g of iron nitrate nonahydrate and 7.36 kg of aluminum nitrate nonahydrate were dissolved in 20 L of deionized water, and stirred until completely dissolved to obtain a nitrate salt solution;

[0087] Then 10 L of 1 mol / L aqueous ammonium carbonate solution was added dropwise into the nitrate salt solution, and the dropping rate was controlled at 50 mL / min. During the dropping process, the mixture was stirred at a stirring speed of 1200 r / min to obtain a mixed solution;

[0088] After the dropping was completed, the pH value of the mixed solution was adjusted to 10 with 0.5 mol / L ammonia water, and after complete precipitation, the precipitate was filtered out, dried in a 100°C oven, the dried material was collected and placed in a muffle furnace, calcined at 450°C for 3h, the obtained powder was ground into fine powder with a mortar, and sieved through a 100 mesh sieve to prepare the catalyst 3. Example

[0089] Example 1

[0090] A method for preparing carbon nanotubes by pyrolyzing plastics, comprising the following synthesis steps:

[0091] Waste plastic pretreatment: 100 g of recycled polypropylene masterbatch was washed and dried, then crushed into polypropylene masterbatch particles of 50-100 mesh. The polypropylene masterbatch particles were placed in a quartz boat and placed in a low-temperature chamber in a carbon nanotube production device;

[0092] Addition of catalyst: 1 g of catalyst 1 was placed in a quartz boat, and the quartz boat was placed in a high-temperature chamber in a carbon nanotube production device. The gas circuit was connected, nitrogen was introduced, and the flow rate was 0.5 L / min;

[0093] CVD preparation: After 10 min of nitrogen flow, the temperature was raised, the nitrogen flow rate was changed to 0.75 L / min, the low-temperature reaction chamber and the high-temperature reaction chamber in the carbon nanotube production device were raised to 250°C and 550°C respectively at a rate of 5°C / min, and then held for 1.5 h. After stopping heating, the carbon nanotubes were prepared by cooling to room temperature.

[0094] Example 2

[0095] A method for preparing carbon nanotubes by pyrolyzing plastics, comprising the following synthesis steps:

[0096] Waste plastic pretreatment: 100 g of recycled polypropylene masterbatch was washed and dried, then crushed into polypropylene masterbatch particles of 50-100 mesh. The polypropylene masterbatch particles were placed in a quartz boat and placed in the low-temperature chamber of the carbon nanotube production device;

[0097] Addition of catalyst: 1 g of catalyst 1 was placed in a quartz boat, which was then placed in the high-temperature chamber of the carbon nanotube production device. The gas circuit was connected, nitrogen was introduced, and the flow rate was 1 L / min;

[0098] CVD preparation: After 10 minutes of nitrogen flow, the temperature was raised, the nitrogen flow rate was changed to 0.75 L / min, and the low-temperature reaction chamber and the high-temperature reaction chamber of the carbon nanotube production device were raised to 450°C and 700°C at a rate of 5°C / min, respectively. After 1.5 h of heat preservation, nitrogen was continuously introduced at a rate of 1 L / min, and after the heating was stopped, the system was allowed to cool to room temperature. Carbon nanotubes 2 were prepared.

[0099] Example 3

[0100] A method for preparing carbon nanotubes by pyrolyzing plastics, comprising the following synthesis steps:

[0101] Waste plastic pretreatment: 100 g of recycled polypropylene masterbatch was washed and dried, then crushed into polypropylene masterbatch particles of 50-100 mesh. The polypropylene masterbatch particles were placed in a quartz boat and placed in the low-temperature chamber of the carbon nanotube production device;

[0102] Addition of catalyst: 1 g of catalyst 1 was placed in a quartz boat, which was then placed in the high-temperature chamber of the carbon nanotube production device. The gas circuit was connected, nitrogen was introduced, and the flow rate was 1.5 L / min;

[0103] CVD preparation: After 10 minutes of nitrogen flow, the temperature was raised, the nitrogen flow rate was changed to 0.75 L / min, and the low-temperature reaction chamber and the high-temperature reaction chamber of the carbon nanotube production device were raised to 650°C and 950°C at a rate of 5°C / min, respectively. After 1.5 h of heat preservation, nitrogen was continuously introduced at a rate of 1.5 L / min, and after the heating was stopped, the system was allowed to cool to room temperature. Carbon nanotubes 3 were prepared.

[0104] Example 4

[0105] A method for preparing carbon nanotubes by pyrolyzing plastics, comprising the following synthesis steps:

[0106] Waste plastic pretreatment: 100 g of recycled self-sealing bags (LDPE) were washed and dried, then crushed into LDPE self-sealing bag fragments. The LDPE self-sealing bag fragments were placed in a quartz boat and placed in the low-temperature chamber of the carbon nanotube production device;

[0107] Addition of catalyst: 1.5 g of catalyst 2 was placed in a quartz boat, which was then placed in the high-temperature chamber of the carbon nanotube production device. The gas circuit was connected, nitrogen was introduced at a flow rate of 1 L / min;

[0108] CVD preparation: After 10 min of nitrogen flow, the temperature was raised, the nitrogen flow rate was changed to 0.5 L / min, and the low-temperature reaction chamber and the high-temperature reaction chamber of the carbon nanotube production device were raised to 500°C and 650°C, respectively, at a rate of 30°C / min. After 2 h of heat preservation, nitrogen was continuously introduced at a rate of 1 L / min, and after the heating was stopped, the system was allowed to cool to room temperature. Carbon nanotubes 4 were thus prepared.

[0109] Example 5

[0110] A method for preparing carbon nanotubes by pyrolyzing plastic, comprising the following synthesis steps:

[0111] Waste plastic pretreatment: 100 g of equal mass of waste milk bottles and bottle caps (PE+PP+PET) were washed and dried, then crushed into 50-100 mesh waste plastic particles. The waste plastic particles were placed in a quartz boat and placed in the low-temperature chamber of the carbon nanotube production device;

[0112] Addition of catalyst: 0.5 g of catalyst 3 was placed in a quartz boat, which was then placed in the high-temperature chamber of the carbon nanotube production device. The gas circuit was connected, nitrogen was introduced at a flow rate of 1 L / min;

[0113] CVD preparation: After 10 min of nitrogen flow, the temperature was raised, the nitrogen flow rate was changed to 1.5 L / min, and the low-temperature reaction chamber and the high-temperature reaction chamber of the carbon nanotube production device were raised to 500°C and 750°C, respectively, at a rate of 30°C / min. After 1 h of heat preservation, nitrogen was continuously introduced at a rate of 1 L / min, and after the heating was stopped, the system was allowed to cool to room temperature. Carbon nanotubes 5 were thus prepared.

[0114] Example 6

[0115] A method for preparing carbon nanotubes by pyrolyzing plastic, which differs from Example 5 in that in the CVD preparation step, the nitrogen flow rate after heating is adjusted to 0.05 L / min.

[0116] Example 7

[0117] A method for preparing carbon nanotubes by pyrolyzing plastic, which differs from Example 6 in that in the CVD preparation step, the nitrogen flow rate after heating is adjusted to 2 L / min.

[0118] Example 8

[0119] A method for preparing carbon nanotubes by pyrolyzing plastics, which is different from example 5 in that the amount of catalyst added is 0.05 g.

[0120] Example 9

[0121] A method for preparing carbon nanotubes by pyrolyzing plastics, which is different from example 5 in that the amount of catalyst added is 10 g.

[0122] Example 10

[0123] A method for preparing carbon nanotubes by pyrolyzing plastics, which is different from example 1 in that the catalyst 4 used in example 10 is prepared according to the following scheme:

[0124] Take 750 g of cobalt nitrate hexahydrate and 1.09 kg of iron nitrate nonahydrate, dissolve them in 20 L of deionized water, stir until completely dissolved, and collect the nitrate solution; add 3 kg of nano-alumina (D50=50 nm) to the nitrate solution, heat in an oil bath while stirring, until the water is evaporated to form a sol, place the evaporation container containing the above sol in a 120°C oven and heat for 6 h, take out the dried powder and place it in a muffle furnace to calcine at 450°C for 3 h, grind the obtained powder into fine powder with a mortar, sieve through a 100 mesh sieve, and prepare catalyst 4.

[0125] Comparative Example

[0126] Comparative Example 1

[0127] A method for preparing carbon nanotubes by pyrolyzing plastics, which comprises the following steps:

[0128] Take 1 g of catalyst 1 and 100 g of recycled polypropylene (PP) masterbatch, mix uniformly with a cell disruptor, and then place it in a quartz boat in a tube furnace high-temperature reaction chamber, and the rest of the preparation conditions are the same as in example 1.

[0129] Performance detection test

[0130] The carbon nanotubes prepared in examples 1-10 and comparative example 1 were tested, and the specific test was to test the yield and carbon conversion rate.

[0131] Yield and carbon conversion rate, the calculation formula is as follows:

[0132] Yield = weight of collected material / weight of catalyst

[0133] Carbon conversion rate = (weight of collected material - weight of metal elements in catalyst) / (weight of plastic x proportion of carbon elements in plastic) x 100%.

[0134] Meanwhile, Raman spectrum analysis was performed on the carbon nanotube 1 prepared in Example 1, and the Raman spectrum chart is shown in Fig. 5 ;

[0135] Scanning electron microscope detection was performed on the carbon nanotube 4 prepared in Example 4, and the detection chart is shown in Fig. 6 ;

[0136] Transmission electron microscope detection was performed on the carbon nanotube 5 prepared in Example 5, and the detection chart is shown in Fig. 7 . The remaining detection results are shown in Table 1 below:

[0137] Table 1 Performance detection table

[0138]

[0139] In combination with Examples 1-10, Comparative Example 1, Figs. 5-7 and Table 1 Performance Detection Table, it can be found that:

[0140] (1) First, the performance of Examples 1-3 is compared with Comparative Example 1. As can be seen from the data in Table 1, the data of Examples 1-3 is obviously better than that of Comparative Example 1. Since the technical scheme of Comparative Example 1 does not use the technical scheme of segmented deposition, the carbon conversion rate and the rate are significantly reduced, which shows that by adjusting the structure of the device for producing carbon nanotubes, by setting the waste plastic cracking region and the CVD region in the same horizontal plane after dividing the temperature zones, the production efficiency of carbon nanotubes is improved, and the conversion rate of the carbon nanotube material prepared by cracking waste plastics for gas phase deposition is further improved.

[0141] (2) In combination with Examples 1-3, Example 4 and Example 5, Table 1 and Figs. 5-7 , it can be seen that the data of Examples 1-3 is more excellent, which shows that the catalytic effect of the catalyst containing Mo element used in the technical scheme of the present application is better, and it shows that the Mo-based catalyst material used in the present application can effectively inhibit the agglomeration of catalyst particles, realize the control of the morphology and size of catalyst particles, and thus effectively improve the conversion rate and rate of the carbon nanotube material prepared by cracking waste plastics for deposition catalysis.

[0142] (3) In combination with Examples 5-7 and Table 1, it is shown that by adjusting the flow rate of the protective gas, the flow rate of the protective gas is adjusted according to different situations, which can effectively improve the deposition rate of the carbon source gas formed by decomposition on the surface of the catalyst in the actual use process, thereby optimizing the conversion rate of the carbon nanotube particles, improving the size structure of the carbon nanotube particles, and thus effectively improving the performance of the produced carbon nanotube particles.

[0143] (4) combining examples 8-9 with example 5, it is illustrated that the present application selects a suitable ratio between the catalyst material and the waste plastic particles, so that the prepared carbon nanotube material has a good conversion rate.

[0144] (5) comparing example 10 with example 1, the performance of example 1 is obviously improved compared with example 10, which illustrates that the present application prepares the catalyst material by the coprecipitation method, and since the catalyst material prepared by the coprecipitation method has a uniform and controllable particle size and a more excellent size structure, the prepared CNTs have a good rate and conversion rate in the subsequent preparation process of CNTs.

[0145] The specific embodiments are only an explanation of the present application, and are not a limitation of the present application, and those skilled in the art can make modifications to the embodiments without creative contribution according to the needs after reading the present specification, but as long as the modifications are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A carbon nanotube production apparatus characterized by comprising: The multi-temperature zone reaction furnace (1) is provided with a plurality of communicating reaction chambers, and the plurality of reaction chambers are located on the same horizontal plane. The carbon nanotube production device further comprises: a feeding bin (2) arranged at one end of the multi-temperature zone reaction furnace (1), wherein the feeding bin (2) is provided with a feeding chamber communicating with the reaction chamber; and a discharging bin (3) arranged at the other end of the multi-temperature zone reaction furnace (1) and provided with a discharging chamber communicating with the reaction chamber. The carbon nanotube production device has two reaction chambers in the multi-temperature zone reaction furnace (1), which are a low-temperature reaction chamber (21) and a high-temperature reaction chamber (31). The carbon nanotube production device further comprises: a feeding device (22) arranged at one end in the feeding chamber and at the other end in the low-temperature reaction chamber (21), wherein the feeding device (22) is used for carrying a reaction container to make the reaction container reciprocatingly move in the feeding chamber and the low-temperature reaction chamber (21). The carbon nanotube production device further comprises a discharging device (32) arranged at one end in the discharging chamber and at the other end in the high-temperature reaction chamber (31), wherein the discharging device (32) is used for carrying a reaction container to make the reaction container reciprocatingly move in the discharging chamber and the high-temperature reaction chamber (31).

2. A method for producing carbon nanotubes by pyrolyzing plastic using the carbon nanotube production apparatus according to claim 1, characterized by: The preparation steps comprise: waste plastic pretreatment, i.e. taking waste plastics, washing and drying, crushing and collecting waste plastic particles, and placing the waste plastic particles in the low-temperature reaction chamber of the carbon nanotube production device; adding a catalyst to the high-temperature reaction chamber of the carbon nanotube production device and introducing a protective gas; CVD preparation, i.e. heating treatment of the low-temperature reaction chamber and the high-temperature reaction chamber, pyrolysis of the low-temperature reaction chamber, vapor deposition of the high-temperature reaction chamber, standing and cooling, to obtain carbon nanotubes. The low-temperature reaction chamber and the high-temperature reaction chamber are arranged on the same horizontal plane.

3. The method of claim 2, wherein the pyrolyzing of the plastic to produce carbon nanotubes is performed at a temperature of about 500 °C to about 700 °C. The size of the waste plastic particles is 50-100 mesh.

4. The method of claim 3, wherein the pyrolyzing of the plastic to produce carbon nanotubes is performed at a temperature of about 500 °C to about 700 °C. The heating rate of the low-temperature reaction chamber is 5-30 ℃ / min, and the pyrolysis temperature is 250-650 ℃; and the heating rate of the high-temperature reaction chamber is 5-30 ℃ / min, and the pyrolysis temperature is 550-950 ℃.

5. The method of claim 4, wherein the pyrolyzing of the plastic to produce carbon nanotubes is performed at a temperature of about 500 °C to about 700 °C. The catalyst includes Co 1-x M x The Co 1-x M x The M element in the Co / Al2O3 catalyst includes any one of Fe, Ni, Mo.

6. The method of claim 5, wherein the pyrolyzing of the plastic to produce carbon nanotubes is performed at a temperature of about 500 °C to about 700 °C. The Co 1-x M x Co in the / Al2O3 catalyst 1-x M x The mass ratio of Co to Al2O3 is 1: (1-10), and x = 0-0.

5.

7. The method of claim 6, wherein the pyrolyzing of the plastic to produce carbon nanotubes is performed at a temperature of about 500 °C to about 700 °C. The Co 1-x M x The Co 1- x M x / Al2O3 catalyst is prepared by the following scheme: dissolving a cobalt salt and an aluminum salt in a solvent, stirring and mixing to obtain a mixed solution; stirring and mixing an aqueous ammonium salt solution with the mixed solution, adjusting the pH to 9-10, filtering, drying, and calcining to obtain the Co 1- x M x / Al2O3 catalyst.

8. The method of claim 7, wherein the pyrolyzing of the plastic to produce carbon nanotubes is performed at a temperature of about 500 °C to about 700 °C. The ammonium salt aqueous solution comprises any one of an ammonium carbonate aqueous solution, an ammonium molybdate tetrahydrate / ammonium carbonate aqueous solution, an iron nitrate / ammonium carbonate aqueous solution or a nickel nitrate / ammonium carbonate aqueous solution.

9. The method of claim 2, wherein the pyrolyzing of the plastic to produce carbon nanotubes is performed at a temperature of about 500 °C to about 700 °C. The mass ratio of the catalyst to the waste plastic particles is (0.005-1):

1.

10. The method of claim 2, wherein the pyrolyzing of the plastic to produce carbon nanotubes is performed at a temperature of about 500 °C to about 700 °C. In the step of adding a catalyst, the protective gas is introduced at a rate of 0.5-1.5 L / min, and the protective gas is introduced from the low-temperature reaction chamber to the high-temperature reaction chamber.

11. The method of claim 2, wherein the pyrolyzing of the plastic to produce carbon nanotubes is performed at a temperature of about 500 °C to about 700 °C. The CVD preparation step further comprises: adjusting the inflow rate of the protective gas during the temperature rising heating treatment and the temperature maintaining pyrolysis process to be 0.05-2 L / min; and after the temperature maintaining pyrolysis is completed, adjusting the inflow rate of the protective gas again to be 0.5-1.5 L / min.

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