Method and treatment system for preparing hydrogen and carbon nanotubes by converting plastic through plasma-thermocatalysis coupling

Abstract

The invention relates to a method and a treatment system for preparing hydrogen and a carbon nano tube by converting plastic through plasma-thermocatalysis coupling. The method comprises the following steps that S1, plasma is applied to conduct pyrolysis treatment on waste plastic powder, and pyrolysis gas is obtained; and S2, under the action of a metal catalyst, carrying out thermocatalytic treatment on the pyrolysis gas obtained in the step S1 to obtain hydrogen and the carbon nanotubes. The treatment system comprises a plasma pyrolysis reactor, a thermocatalytic reactor, a gas condenser and a gas collecting device. Compared with the prior art, the method has the advantages that the selectivity of plasma catalysis can be improved, the reaction time of traditional thermocatalysis is shortened, the efficiency and the yield are improved, and resource conversion from the waste plastics to high-selectivity hydrogen and high-added-value carbon nanotube materials is realized.

Description

Technical Field

[0001] The invention relates to the technical field of solid waste resource recovery, and in particular to a method and a processing system for preparing hydrogen and carbon nanotubes by plasma-thermal catalytic coupling conversion of plastics. Background Art

[0002] Plastic products have the advantages of stable chemical properties, light weight, high specific strength and low price, and have been widely used in various fields of industrial and agricultural production and daily life. However, due to the difficulty of plastic degradation, the "white pollution" problem caused by a large amount of discarded plastics has become increasingly serious. According to statistics from the United Nations Environment Program, global plastic consumption is growing at an annual rate of 8%. Nearly 10 million tons of plastic waste enters the ocean every year, polluting the living environment of marine animals and causing a large number of marine organisms to die from accidentally ingesting plastic fragments. Plastic waste can also affect the growth of crops, pollute groundwater, and may enter the human body through eating and breathing, affecting human health. Plastic pollution has become a global environmental problem, posing a serious threat to the ecological environment and human health. The clean and high-value-added energy and resource utilization of waste plastics is one of the key and difficult points of current research.

[0003] In order to solve the waste plastic pollution problem and maximize its value, some researchers have proposed plasma conversion or thermal catalytic conversion of waste plastics, but there are problems such as difficult to control product selectivity and low efficiency and yield of high value-added products, which greatly restricts the further development of waste plastic recycling industry. At present, there is still a lack of effective methods for high-selectivity and high-value-added recycling of waste plastics. Summary of the invention

[0004] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and to provide a method and a processing system for converting plastics into hydrogen and carbon nanotubes by plasma-thermal catalytic coupling, aiming to solve the problems of difficult control of the selectivity of the existing waste plastic conversion products, low product added value, low yield and high cost.

[0005] During the course of conception, the applicant believed that the present invention adopts a plasma-thermal catalytic coupling conversion process, in which waste plastics are pyrolyzed by plasma and the resulting gas is then subjected to thermal catalysis, which can improve the selectivity of plasma catalysis, shorten the reaction time of traditional thermal catalysis, and improve efficiency and yield, thereby realizing the resource conversion of waste plastics into highly selective hydrogen and high value-added carbon nanotube materials.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] In one aspect, the present invention provides a method for preparing hydrogen and carbon nanotubes by plasma-thermal catalytic coupled conversion of plastics, comprising the following steps:

[0008] S1. crushing waste plastics into powder, and applying plasma to pyrolyze the waste plastic powder to obtain pyrolysis gas;

[0009] S2. Under the action of a metal catalyst, the pyrolysis gas obtained in S1 is subjected to thermal catalytic treatment to obtain hydrogen and carbon nanotubes.

[0010] Furthermore, in S1, the step of subjecting the waste plastic powder to pyrolysis by plasma comprises: subjecting the waste plastic powder to pyrolysis for 0.5 to 100 minutes in a nitrogen environment at a temperature of 400 to 900° C. to obtain pyrolysis gas.

[0011] Preferably, the waste plastic powder is pyrolyzed for 5 to 15 minutes.

[0012] Furthermore, the flow rate of the nitrogen is 2 to 20 m 3 / h.

[0013] Preferably, the flow rate of the nitrogen is 5m 3 / h.

[0014] Furthermore, the pyrolysis gas includes methane, ethylene, acetylene and hydrogen.

[0015] Furthermore, in S1, the waste plastic powder is at least one of polyethylene, polypropylene, polyvinyl chloride, polystyrene, polybutylene terephthalate, polycarbonate, and polystyrene.

[0016] Furthermore, in S2, the step of thermal catalytic treatment includes: performing thermal catalytic treatment on the pyrolysis gas for 0.5 to 5 hours at a temperature of 500 to 1000° C. in the presence of the metal catalyst to obtain hydrogen and carbon nanotubes.

[0017] Preferably, the pyrolysis gas is subjected to thermal catalytic treatment for 2 to 3 hours.

[0018] Furthermore, in S2, the metal catalyst is at least one of iron-, nickel-, and cobalt-based metal catalytic materials.

[0019] Furthermore, the mass ratio of the waste plastic powder to the metal catalyst is 1:(0.5-2).

[0020] On the other hand, the present invention also provides a processing system for preparing hydrogen and carbon nanotubes by plasma-thermal catalytic coupling conversion of plastics, comprising:

[0021] Plasma pyrolysis reactor, used for plasma pyrolysis of waste plastic powder to generate pyrolysis gas;

[0022] A thermal catalytic reactor, which is provided with a metal catalyst inside and is connected to the plasma pyrolysis reactor, and is used to catalyze the pyrolysis gas. The pyrolysis gas is catalytically cracked on the surface of the active metal of the catalyst to produce hydrogen, and the carbon produced by the cracking is deposited on the surface of the catalyst and forms carbon nanotubes through migration and recombination. The carbon nanotubes are deposited in the thermal catalytic reactor;

[0023] a gas condenser, connected to the thermal catalytic reactor, for cooling the hydrogen;

[0024] A gas collecting device is connected to the gas condenser and is used for collecting hydrogen.

[0025] Furthermore, the power of the plasma pyrolysis reactor is 30-60KW.

[0026] Preferably, the power of the plasma pyrolysis reactor is 40-60 kW.

[0027] Furthermore, a heating device is provided in the thermal catalytic reactor, and the heating device is used to heat the thermal catalytic reactor to 500-1000°C.

[0028] Furthermore, the plasma pyrolysis reactor is also connected to a plasma generation control device and nitrogen, thereby ensuring the effective operation and safety of the plasma pyrolysis reactor.

[0029] Furthermore, the working principle of the treatment system is as follows: under a nitrogen atmosphere, the high-energy environment of plasma is used to break the chemical bonds of organic matter in the plastic, causing it to be pyrolyzed into a gaseous mixture such as hydrocarbon gas and hydrogen, and then introduced into a thermal catalytic reactor; during the thermal catalytic treatment process, the hydrocarbon gas is catalytically decomposed on the surface of metals such as Fe, Co, and Ni to produce hydrogen, and the carbon source is deposited and reformed on the surface of these metal catalysts to form carbon nanotubes, which are deposited in the thermal catalytic reactor; a gas condenser is arranged between the thermal catalytic reactor and the gas collection device to cool the hydrogen, and finally the gas collection device collects relatively pure hydrogen.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] (1) The plasma-thermal catalytic coupling conversion process adopted by the present invention uses waste plastics as raw materials, and uses the high-energy environment of plasma to break the chemical bonds of organic matter in plastics, and pyrolyzes the waste plastics into gaseous mixtures such as hydrocarbon gas and hydrogen; then, under the action of a metal catalyst, the resulting pyrolysis gas is subjected to thermal catalytic treatment. During the thermal catalytic treatment, the hydrocarbon gas is catalytically decomposed on the metal surface, and the generated carbon elements are arranged on the metal surface according to a specific structure to form carbon nanotubes; in addition, hydrogen has a reducing property, which can prevent the metal catalyst from being oxidized and losing its catalytic activity, maintain the activity of the metal catalyst, and is conducive to the deposition of hydrocarbon gas to form nano-carbon materials. Moreover, through thermal catalytic treatment, hydrogen can be purified and enriched, thereby improving the utilization rate of hydrogen. This method can improve the selectivity of plasma catalysis, shorten the reaction time of traditional thermal catalysis, and improve efficiency and yield, thereby realizing the resource conversion of plastics into highly selective hydrogen and high value-added carbon nanotube materials.

[0032] (2) The plasma-thermal catalytic coupled conversion plastic processing system provided by the present invention for preparing hydrogen and carbon nanotubes can basically recover carbon, hydrogen and other elemental components in the waste plastics through pyrolysis and thermal catalytic treatment of waste plastics. The recovery efficiency is high, and the problems of low selectivity and long reaction time of traditional methods are effectively avoided. It is expected to pave the way for large-scale recycling and industrial application of plastics. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 A schematic diagram of the structure of a processing system for preparing hydrogen and carbon nanotubes by plasma-thermal catalytic coupling conversion of plastics provided in Example 1 of the present invention;

[0034] Figure 2 This is a scanning electron microscope (SEM) image of the carbon nanotubes prepared in Example 1 of the present invention.

[0035] Figure numerals: 1-plasma pyrolysis reactor, 2-waste plastic powder, 3-thermal catalytic reactor, 4-metal catalyst. DETAILED DESCRIPTION

[0036] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. Any features such as preparation means, materials, structures or composition ratios not clearly described in this technical solution are regarded as common technical features disclosed in the prior art.

[0037] The disposable plastic lunch boxes, plastic beverage bottles, plastic bags, plastic cling film, plastic gloves, etc. in the following embodiments are all purchased from the market, and the above-mentioned plastic products are at least one of polyethylene, polypropylene, polyvinyl chloride, polystyrene, polybutylene terephthalate, polycarbonate, and polystyrene; the metal catalysts in the following embodiments include all Fe, Co, and Ni-based catalysts that can realize the thermal catalytic reaction in this application, as well as molecular sieve-loaded Fe, Co, and Ni-based catalysts, such as alumina-based non-precious metal single-atom catalysts, product numbers FMA5386775 and FMA5386774; the model of the gas condenser in the following embodiments is JCT-1 gas condensation dryer.

[0038] Example 1

[0039] The present invention provides a processing system for preparing hydrogen and carbon nanotubes by plasma-thermal catalytic coupling conversion of plastics, comprising:

[0040] A plasma pyrolysis reactor 1 is used for plasma pyrolysis of waste plastic powder 2 to generate pyrolysis gas;

[0041] The thermal catalytic reactor 3 is provided with a metal catalyst 4 inside and is connected to the plasma pyrolysis reactor 1, and is used to catalyze the pyrolysis gas. The pyrolysis gas is catalytically cracked on the surface of the active metal of the catalyst to produce hydrogen, and the carbon produced by the cracking is deposited on the surface of the catalyst, and forms carbon nanotubes through migration and recombination. The carbon nanotubes are deposited in the thermal catalytic reactor 3;

[0042] A gas condenser, connected to the thermal catalytic reactor 3, for cooling the hydrogen;

[0043] A gas collecting device is connected to the gas condenser and is used for collecting hydrogen.

[0044] In this embodiment, the power of the plasma pyrolysis reactor 1 is 30-60KW.

[0045] In this embodiment, the heating temperature of the plasma pyrolysis reactor 1 is 400-900°C, which provides a suitable pyrolysis temperature for the pyrolysis of waste plastics, and fully pyrolyzes the waste plastics into products such as hydrocarbon gases and hydrogen. The thermal catalytic reactor 3 is provided with a heating device, which is used to heat the thermal catalytic reactor 3 to 500-1000°C, catalyze the pyrolysis gas, and promote the growth of carbon nanotubes and high-purity hydrogen.

[0046] In this embodiment, the plasma pyrolysis reactor 1 is also connected to a plasma generation control device and nitrogen, which ensures the effective operation and safety of the plasma pyrolysis reactor 1 .

[0047] Example 2

[0048] The present invention provides a method for preparing hydrogen and carbon nanotubes by plasma-thermal catalytic coupled conversion of plastics, comprising the following steps:

[0049] S1. Crush the disposable plastic lunch box into powder, place 0.5g of waste plastic powder 2 in a plasma with a power of 40KW for plasma pyrolysis for 5min, and the working gas of the plasma is nitrogen with a flow rate of 5m 3 / h, and obtain pyrolysis gas;

[0050] S2. The pyrolysis gas obtained in S1 is directly introduced into a thermal catalytic reactor 3 at 800°C. Under the action of 1.0g of Fe-based metal catalyst, the pyrolysis gas is thermally catalytically treated for 2h to achieve resource conversion of plastic into highly selective hydrogen (yield>60%) and high value-added carbon nanotube materials (yield>30%).

[0051] The ethane, ethylene, acetylene, methane, etc. produced by the plasma pyrolysis of disposable plastic lunch boxes are cracked into high-value-added carbon nanotubes and hydrogen-rich gas through chemical vapor deposition in a thermal catalytic process, which can improve the yield and selectivity of the obtained hydrogen and carbon nanotubes.

[0052] Example 3

[0053] The present invention provides a method for preparing hydrogen and carbon nanotubes by plasma-thermal catalytic coupled conversion of plastics, comprising the following steps:

[0054] S1. Crush the plastic beverage bottle into powder, place 4.0g of waste plastic powder 2 in a plasma with a power of 50KW for plasma pyrolysis for 10min, and the plasma working gas is nitrogen with a flow rate of 5m 3 / h, and obtain pyrolysis gas;

[0055] S2. The pyrolysis gas obtained in S1 is directly introduced into a thermal catalytic reactor 3 at 800°C. Under the action of 2.0g of molecular sieve-loaded Fe-based catalyst, the pyrolysis gas is thermally catalytically treated for 3h to achieve resource conversion of plastic into highly selective hydrogen (yield>50%) and high value-added carbon nanotube materials (yield>27%).

[0056] The ethane, ethylene, acetylene, methane and the like produced by the plasma pyrolysis of plastic beverage bottles are cracked into high value-added carbon nanotubes and hydrogen-rich gas through chemical vapor deposition in a thermal catalytic process, thereby improving the yield and selectivity of the obtained hydrogen and carbon nanotubes.

[0057] Example 4

[0058] The present invention provides a method for preparing hydrogen and carbon nanotubes by plasma-thermal catalytic coupled conversion of plastics, comprising the following steps:

[0059] S1. Crushing the plastic bag into powder, placing 1.5g of waste plastic powder 2 in a plasma with a power of 45KW for plasma pyrolysis for 15min, the plasma working gas is nitrogen, and the flow rate of nitrogen is 5m 3 / h, and obtain pyrolysis gas;

[0060] S2. The pyrolysis gas obtained in S1 is directly introduced into a thermal catalytic reactor 3 at 800°C. Under the action of 1.5g of molecular sieve-loaded Co-based catalyst, the pyrolysis gas is thermally catalytically treated for 2h to achieve resource conversion of plastic into highly selective hydrogen (yield>53%) and high value-added carbon nanotube materials (yield>31%).

[0061] Ethane, ethylene, acetylene, methane, etc. produced by plasma pyrolysis of plastic bags are cracked into high-value-added carbon nanotubes and hydrogen-rich gas through chemical vapor deposition in a thermal catalytic process, which can improve the yield and selectivity of the obtained hydrogen and carbon nanotubes.

[0062] Example 5

[0063] The present invention provides a method for preparing hydrogen and carbon nanotubes by plasma-thermal catalytic coupled conversion of plastics, comprising the following steps:

[0064] S1. Crush the plastic wrap into powder, place 1.0 g of waste plastic powder 2 in a plasma with a power of 55 kW for plasma pyrolysis for 8 min, and use nitrogen as the working gas of the plasma with a flow rate of 5 m 3 / h, and obtain pyrolysis gas;

[0065] S2. The pyrolysis gas obtained in S1 is directly introduced into a thermal catalytic reactor 3 at 800°C. Under the action of 2.0g of molecular sieve-loaded Ni-based catalyst, the pyrolysis gas is thermally catalytically treated for 2.5h to achieve resource conversion of plastic into highly selective hydrogen (yield>60%) and high value-added carbon nanotube materials (yield>30%).

[0066] Ethane, ethylene, acetylene, methane and the like produced by plasma pyrolysis of plastic wrap are cracked into high value-added carbon nanotubes and hydrogen-rich gas through chemical vapor deposition in a thermal catalytic process, thereby improving the yield and selectivity of the obtained hydrogen and carbon nanotubes.

[0067] Example 6

[0068] The present invention provides a method for preparing hydrogen and carbon nanotubes by plasma-thermal catalytic coupled conversion of plastics, comprising the following steps:

[0069] S1. Crush the plastic gloves into powder. Place 2.0 g of waste plastic powder 2 in a plasma with a power of 60 kW for plasma pyrolysis for 5 min. The working gas of the plasma is nitrogen with a flow rate of 5 m 3 / h, and obtain pyrolysis gas;

[0070] S2. The pyrolysis gas obtained in S1 is directly introduced into a thermal catalytic reactor 3 at 800°C. Under the action of 1.0g of molecular sieve-loaded Fe-based catalyst, the pyrolysis gas is thermally catalytically treated for 3h to achieve resource conversion of plastic into highly selective hydrogen (yield>55%) and high value-added carbon nanotube materials (yield>31%).

[0071] The ethane, ethylene, acetylene, methane and the like produced by the plasma pyrolysis of plastic gloves are cracked into high value-added carbon nanotubes and hydrogen-rich gas through chemical vapor deposition in a thermal catalytic process, thereby improving the yield and selectivity of the obtained hydrogen and carbon nanotubes.

[0072] Example 7

[0073] The present invention provides a method for preparing hydrogen and carbon nanotubes by plasma-thermal catalytic coupled conversion of plastics, comprising the following steps:

[0074] S1. Crush a mixture of disposable plastic lunch boxes, plastic beverage bottles, plastic bags, plastic cling film, and plastic gloves into powder. Place 2.0 g of waste plastic powder 2 in a plasma with a power of 60 kW for plasma pyrolysis for 10 min. The working gas of the plasma is nitrogen, and the flow rate of nitrogen is 5 m 3 / h, and obtain pyrolysis gas;

[0075] S2. The pyrolysis gas obtained in S1 is directly introduced into a thermal catalytic reactor 3 at 800°C. Under the action of 2.0g of molecular sieve-loaded Fe-based catalyst, the pyrolysis gas is thermally catalytically treated for 3h to achieve resource conversion of plastic into highly selective hydrogen (yield>52%) and high value-added carbon nanotube materials (yield>35%).

[0076] Ethane, ethylene, acetylene, methane, etc. produced by plasma pyrolysis of a mixture of disposable plastic lunch boxes, plastic beverage bottles, plastic bags, plastic cling film, and plastic gloves are cracked into high-value-added carbon nanotubes and hydrogen-rich gas through chemical vapor deposition in a thermal catalytic process, thereby improving the yield and selectivity of the resulting hydrogen and carbon nanotubes.

[0077] Example 8

[0078] The present invention provides a method for preparing hydrogen and carbon nanotubes by plasma-thermal catalytic coupled conversion of plastics, comprising the following steps:

[0079] S1. Crushing plastic waste from a landfill into powder, placing 0.5 g of waste plastic powder 2 in a plasma with a power of 55 kW for plasma pyrolysis for 15 min. The plasma working gas is nitrogen with a flow rate of 5 m 3 / h, and obtain pyrolysis gas;

[0080] S2. The pyrolysis gas obtained in S1 is directly introduced into a thermal catalytic reactor 3 at 800°C. Under the action of 1.0g of molecular sieve-loaded Co-based catalyst, the pyrolysis gas is thermally catalytically treated for 2.5h to achieve resource conversion of plastic into highly selective hydrogen (yield>58%) and high value-added carbon nanotube materials (yield>35%).

[0081] Ethane, ethylene, acetylene, methane, etc. produced by plasma pyrolysis of plastic waste in landfills are cracked into high-value-added carbon nanotubes and hydrogen-rich gas through chemical vapor deposition in a thermal catalytic process, which can improve the yield and selectivity of the resulting hydrogen and carbon nanotubes.

[0082] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A method for preparing hydrogen and carbon nanotubes by plasma-thermal catalytic conversion of plastics, characterized in that: The steps include: S1. Using plasma to pyrolyze waste plastic powder to obtain pyrolysis gas; S2. Under the action of a metal catalyst, the pyrolysis gas obtained in S1 is subjected to thermal catalytic treatment to obtain hydrogen and carbon nanotubes.

2. The method for preparing hydrogen and carbon nanotubes by plasma-thermal catalytic coupled conversion of plastics according to claim 1, characterized in that: In S1, the step of pyrolyzing the waste plastic powder by plasma comprises: pyrolyzing the waste plastic powder for 0.5 to 100 minutes in a nitrogen environment at a temperature of 400 to 900° C. to obtain pyrolysis gas.

3. The method for preparing hydrogen and carbon nanotubes by plasma-thermal catalytic coupled conversion of plastics according to claim 2, characterized in that: The flow rate of the nitrogen is 2 to 20 m 3 / h.

4. The method for preparing hydrogen and carbon nanotubes by plasma-thermal catalytic conversion of plastics according to claim 1, characterized in that: In S1, the waste plastic powder is at least one of polyethylene, polypropylene, polyvinyl chloride, polystyrene, polybutylene terephthalate, polycarbonate, and polystyrene.

5. The method for preparing hydrogen and carbon nanotubes by plasma-thermal catalytic coupled conversion of plastics according to claim 1, characterized in that: In S2, the step of thermal catalytic treatment includes: performing thermal catalytic treatment on the pyrolysis gas for 0.5 to 5 hours at a temperature of 500 to 1000° C. in the presence of the metal catalyst to obtain hydrogen and carbon nanotubes.

6. The method for preparing hydrogen and carbon nanotubes by plasma-thermal catalytic coupled conversion of plastics according to claim 1, characterized in that: In S2, the metal catalyst is at least one of iron-, nickel-, and cobalt-based metal catalyst materials.

7. The method for preparing hydrogen and carbon nanotubes by plasma-thermal catalytic coupled conversion of plastics according to claim 1, characterized in that: The mass ratio of the waste plastic powder to the metal catalyst is 1:(0.5-2).

8. A plasma-thermal catalytic coupled conversion plastic processing system for producing hydrogen and carbon nanotubes, characterized in that: include: Plasma pyrolysis reactor, used for plasma pyrolysis of waste plastic powder to generate pyrolysis gas; A thermal catalytic reactor, which has a metal catalyst disposed therein and is in communication with the plasma pyrolysis reactor, and is used to catalyze the pyrolysis gas to eventually generate hydrogen and carbon nanotubes, wherein the carbon nanotubes are deposited in the thermal catalytic reactor; a gas condenser, connected to the thermal catalytic reactor, for cooling the hydrogen; A gas collecting device is connected to the gas condenser and is used for collecting hydrogen.

9. The plasma-thermal catalytic coupled conversion plastic processing system for preparing hydrogen and carbon nanotubes according to claim 8, characterized in that: The power of the plasma pyrolysis reactor is 30-60KW.

10. The plasma-thermal catalytic coupled conversion plastic processing system for preparing hydrogen and carbon nanotubes according to claim 8, characterized in that: A heating device is arranged in the thermal catalytic reactor, and the heating device is used to heat the thermal catalytic reactor to 500-1000°C.

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