CN111100663B

CN111100663B - Method for microwave pyrolysis of waste polyethylene

Info

Publication number: CN111100663B
Application number: CN201811264439.XA
Authority: CN
Inventors: 蒋海斌; 乔金樑; 张晓红; 刘文璐; 黄文氢; 戚桂村; 陈松; 宋志海; 赵亚婷; 蔡传伦; 孙姝琦; 高建明; 赖金梅; 李秉海; 王湘; 张江茹; 韩朋; 茹越; 张红彬; 郭照琰
Original assignee: Sinopec Beijing Research Institute of Chemical Industry; China Petroleum and Chemical Corp
Current assignee: Sinopec Beijing Research Institute of Chemical Industry; China Petroleum and Chemical Corp
Priority date: 2018-10-29
Filing date: 2018-10-29
Publication date: 2021-07-02
Anticipated expiration: 2038-10-29
Also published as: CN111100663A

Abstract

The invention discloses a method for microwave pyrolysis of waste polyethylene. The method comprises the following steps: the waste polyethylene is contacted with the porous composite material, a microwave field is applied to the waste polyethylene and the porous composite material under inert atmosphere or vacuum, and the porous composite material generates electric arc under microwave, so that the high temperature is quickly reached, and the waste polyethylene is cracked; the method of the invention utilizes the porous composite material which generates electric arc in the microwave to generate electric arc in the microwave, thereby quickly generating high temperature, leading the waste polyethylene to be cracked into chemical raw materials, having high process efficiency and high added value of the composition of products.

Description

Method for microwave pyrolysis of waste polyethylene

Technical Field

The invention relates to the technical field of waste plastic resource utilization, in particular to a method for microwave pyrolysis of waste polyethylene.

Background

Since the 50's of the 20 th century, mankind has produced 83 million tons of plastic, of which 63 million tons have become waste. Of the 63 hundred million tons of waste plastics, 9% is recovered, 12% is incinerated, and the remaining 79% (nearly 55 hundred million tons) is buried in a landfill or accumulated in the natural environment. The production speed of plastics is continuously increased by mankind, the current plastic yield reaches 4 hundred million tons every year, and 120 hundred million tons of waste plastics are expected to exist in the world by 2050. Over 800 million tons of plastics enter the ocean every year, and by 2050, there will be more plastic waste in the ocean than fish, if not limited. In recent years, international publications have successively published the pollution of plastic particles to living organisms and drinking water in the ocean and river, and have attracted attention to plastic pollution throughout the society. In 2018, the united nations environmental arrangement focuses on the problem of disposable plastic pollution for the first time, and the theme of the world environmental day is 'plastic warfare fast solution' and calls for 'warfare' of plastic pollution all over the world. Much diligent effort has been made by researchers in addressing the problem of plastic contamination. Since 1970, a great deal of research has been devoted to the preparation of plastics degradable in natural environments, but degradable plastics have important applications only in the aspects of biomedicine, agricultural mulching films, garbage bags and the like, and the existence of the degradable plastics can seriously affect the performance of recycled plastic products in occasions where recycling is needed; meanwhile, the degradable plastics still need a long time to degrade in a non-ideal natural environment, and the problem of white pollution cannot be effectively solved. At present, mechanical recovery is the only widely adopted technical scheme for treating waste plastics, the main steps are organic residue removal, washing, crushing and melt reprocessing in sequence, and new materials are usually blended to maintain the performance in the melt reprocessing process. Different plastics respond to the processing process differently, so that the mechanical recycling technical scheme is applicable to few types of plastics, and only polyethylene terephthalate (PET) and Polyethylene (PE) which are actually recycled by the technology currently account for 9 percent and 37 percent of the annual plastic yield respectively. Temperature sensitive plastics, composites, and plastics that do not melt flow at elevated temperatures (e.g., thermosets) cannot be processed by this method. Chemical recycling methods, in which waste plastics are made into small-molecule hydrocarbons (gas, liquid oil, or solid wax) by chemical conversion or thermal conversion, are considered as technical solutions that can go beyond mechanical recycling, and the resulting products can be used as fuels or chemical raw materials. At present, the technical scheme is not widely applied, mainly because the cost is too high. On one hand, the chemical recovery process mostly needs expensive catalysts, and the selectivity of the catalysts requires that raw materials need to be pure polymers, so that the waste plastics need to be classified in a time-consuming and labor-consuming manner; on the other hand, the chemical recovery process requires large energy consumption.

Polyethylene is one of the most used plastics, a microwave thermal cracking technology of a catalyst is not adopted, the energy efficiency is high, different types of waste polyethylene polluted to a certain extent can be simultaneously treated to be cracked into chemical raw materials, and the key for solving the problem of plastic pollution is expected. The microwave is an electromagnetic wave having a wavelength between infrared rays and Ultra High Frequency (UHF) radio waves, has a very strong penetration capability, has a wavelength between lm and lmm, and corresponds to a frequency of 300GHz to 300 MHz. The magnetron of the microwave generator receives power supply power to generate microwaves, the microwaves are transmitted to the microwave heater through the waveguide, and materials to be heated are heated under the action of the microwave field. The heating mode of microwave is different from the common heat transfer, the high-frequency electric field changes the external electric field and direction periodically at the speed of hundreds of millions of levels per second, so that the polar molecules in the material vibrate with the electric field at high frequency, and the material is heated rapidly under the action of friction and extrusion among molecules, thereby the internal and surface temperatures of the material are raised rapidly. Many patents have disclosed thermal cracking technology using the characteristic of microwave, such as patent CN102585860A, patent CN103252226A, patent CN106520176A, etc., but all use common microwave-sensitive materials such as silicon carbide to generate heat in microwave field and transfer the heat to the thermal cracking material, so as to achieve the purpose of thermal cracking.

Therefore, how to develop an efficient method for microwave pyrolysis of waste polyethylene is still a difficult problem, and the development of the method has huge application prospects.

Disclosure of Invention

In order to solve the problems in the prior art, the invention provides a method for microwave pyrolysis of waste polyethylene. The invention utilizes the porous composite material which generates electric arc in the microwave to generate electric arc in the microwave, thereby quickly generating high temperature and cracking the waste ethylene into chemical raw materials. The method has high efficiency and high added value of the product composition.

The invention aims to provide a method for microwave pyrolysis of waste polyethylene.

The method of the invention comprises the following steps:

the waste polyethylene is contacted with the porous composite material, a microwave field is applied to the waste polyethylene and the porous composite material under inert atmosphere or vacuum, and the porous composite material generates electric arc under microwave, so that the high temperature is quickly reached, and the waste polyethylene is cracked; the weight ratio of the waste polyethylene to the porous composite material is 1: 99-99: 1, preferably 1: 50-50: 1, and more preferably 1: 30-30: 1.

The inert gas atmosphere is an inert gas atmosphere commonly used in the art, such as nitrogen, helium, neon, argon, krypton, or xenon, preferably nitrogen.

The contact mode of the waste polyvinyl chloride and the porous composite material can adopt various modes as long as the waste polyvinyl chloride is in contact with the porous composite material. Preferably: waste polyvinyl chloride is placed on the porous composite material, placed in a cavity formed by the porous composite material, or covered on the lower part by the porous composite material, and the like.

The microwave power is 200W-100 KW; preferably 300W-50 KW, most preferably 500W-20 KW; the microwave time is 0.5-150 min, preferably 1-120 min, and most preferably 2-100 min; the microwave generates electric arc, and the temperature can quickly reach 700-3000 ℃, preferably 800-2500 ℃, and more preferably 800-2000 ℃, so that the waste polyvinyl chloride is cracked.

The porous composite material comprises: an inorganic porous skeleton and a carbon material supported on the inorganic porous skeleton. The load is as follows: the carbon material is fixed on the surface or in the structure of the inorganic porous framework through a certain binding force.

The carbon material accounts for 0.001-99%, preferably 0.01-90%, more preferably 0.1-80% of the total mass of the porous composite material;

the inorganic porous skeleton is an inorganic material having a porous structure; the average pore diameter of the inorganic porous skeleton is 0.01 to 1000. mu.m, preferably 0.05 to 500. mu.m, more preferably 0.2 to 250. mu.m; the porosity is 1% -99.99%; preferably 10% to 99.9%, more preferably 30% to 99%. The pore diameter of an individual pore is derived from the shortest value in the distance between the intersection points of the straight line through the center of the pore and the pore profile in the SEM picture.

The carbon material is at least one of graphene, carbon nanotubes, carbon nanofibers, graphite, carbon black, carbon fibers, carbon dots, carbon nanowires, a product obtained by carbonizing a carbonizable organic substance or a product obtained by carbonizing a mixture of carbonizable organic substances, and preferably at least one of graphene, carbon nanotubes, a product obtained by carbonizing a carbonizable organic substance and a product obtained by carbonizing a mixture of carbonizable organic substances.

The mixture of the carbonizable organic matter is a mixture of the carbonizable organic matter, inorganic matters of non-metal and non-metal compounds, and other organic matters of non-metal compounds.

The carbonization is that: treating organic matter at certain temperature and atmosphere condition to volatilize most or all of hydrogen, oxygen, nitrogen, sulfur and other components in the organic matter and obtain one kind of carbon containing synthetic material.

The organic matter capable of being carbonized is preferably an organic high molecular compound, and the organic high molecular compound comprises a synthetic high molecular compound and a natural organic high molecular compound; the synthetic polymer compound is preferably rubber or plastic; including thermosets and thermoplastics.

The natural organic polymer compound is preferably at least one of starch, viscose, lignin and cellulose.

The synthetic polymer compound is preferably at least one selected from epoxy resin, phenolic resin, furan resin, polystyrene, styrene-divinylbenzene copolymer, polyacrylonitrile, polyaniline, polypyrrole, polythiophene, styrene butadiene rubber and polyurethane rubber.

The mixture of carbonizable organic substances is preferably at least one of coal, natural asphalt, petroleum asphalt, or coal tar asphalt.

The inorganic material of the inorganic porous framework is one or a combination of more of carbon, silicate, aluminate, borate, phosphate, germanate, titanate, oxide, nitride, carbide, boride, sulfide, silicide and halide; wherein the oxide is preferably at least one of alumina, silica, zirconia, magnesia, ceria and titania; the nitride is preferably at least one of silicon nitride, boron nitride, zirconium nitride, hafnium nitride and tantalum nitride; the carbide is preferably at least one of silicon carbide, zirconium carbide, hafnium carbide and tantalum carbide; the boride is preferably at least one of zirconium boride, hafnium boride and tantalum boride.

The inorganic material of the inorganic porous skeleton is more preferably at least one of carbon, silicate, alumina, magnesia, zirconia, silicon carbide, boron nitride, and potassium titanate.

The inorganic porous framework is preferably at least one of the following specific frameworks: a carbon skeleton obtained after carbonization of the polymer sponge, a porous skeleton formed by inorganic fibers, an inorganic sponge skeleton, a skeleton formed by accumulation of inorganic particles, a ceramic sponge skeleton obtained after roasting of a ceramic precursor sponge and a ceramic fiber skeleton obtained after roasting of ceramic precursor fibers; preferred are a skeleton obtained by carbonizing a melamine sponge, a skeleton obtained by carbonizing a phenol resin sponge, a porous skeleton of aluminum silicate fiber (e.g., aluminum silicate rock wool), a porous skeleton of mullite fiber, a porous skeleton of alumina fiber (e.g., alumina fiber board), a porous skeleton of zirconia fiber, a porous skeleton of magnesia fiber, a porous skeleton of boron nitride fiber, a porous skeleton of boron carbide fiber, a porous skeleton of silicon carbide fiber, a porous skeleton of potassium titanate fiber, and a ceramic fiber skeleton obtained by firing a ceramic precursor fiber.

The porous structure of the inorganic porous framework may be derived from the pore structure of the framework material itself, for example in the form of a sponge-like structure; or from a pore structure formed by the accumulation of fibrous materials, such as the structural forms of cellucotton, fibrofelt, fiberboard and the like; it may also come from a pore structure formed by the accumulation of particulate material, for example in the form of a sand heap; but also from a combination of the above forms. Preferably from a pore structure of a pile of fibrous material. In particular, the porous skeleton made of the inorganic fibers described above is a porous structure made of a skeleton in which fibrous materials are stacked, and does not mean that the fibers themselves have porosity.

The porous composite material can generate high-temperature electric arcs in microwaves, for example, electric arcs which enable the porous composite material to be heated to more than 1000 ℃ in a 900w microwave field can be generated, and the material can resist high temperature, and can resist the high temperature of 3000 ℃ at most. The porous composite material for generating electric arc in microwave is a novel and efficient microwave heating material. .

The microwave pyrolysis method for waste polyethylene can comprise the preparation of the porous composite material. Specifically, the preparation method of the porous composite material preferably includes the steps of:

a. preparing a carbon material for loading or a carbon material precursor solution or dispersion liquid;

b. b, immersing an inorganic porous framework or an inorganic porous framework precursor into the solution or the dispersion liquid obtained in the step a to fill the pores of the inorganic porous framework or the inorganic porous framework precursor with the solution or the dispersion liquid; the carbon material and/or the carbon material precursor accounts for 0.001-99.999 percent of the total mass of the inorganic porous framework material or the inorganic porous framework material precursor and the carbon material and/or the carbon material precursor, preferably 0.01-99.99 percent, and more preferably 0.1-99.9 percent;

c. taking out the porous material obtained in the step b, heating, drying, separating out or curing a carbon material or a carbon material precursor, and loading the carbon material or the carbon material precursor on an inorganic porous framework or an inorganic porous framework precursor; the heating and drying temperature is 50-250 ℃, preferably 60-200 ℃, and more preferably 80-180 ℃;

if the raw materials adopt carbon materials and inorganic porous frameworks, the porous composite material for generating the electric arc in the microwave is obtained after the step c; if the raw material adopts at least one of a carbon material precursor or an inorganic porous skeleton precursor, the following step d is required to be continued:

d. c, heating the porous material obtained in the step c in an inert gas atmosphere, converting an inorganic porous skeleton precursor into an inorganic porous skeleton, and/or reducing or carbonizing a carbon material precursor to obtain a porous composite material for generating electric arcs in the microwaves; the heating temperature is 400-1800 ℃, preferably 600-1500 ℃, and more preferably 800-1200 ℃.

Among them, preferred are:

the precursor of the inorganic porous framework is a porous material which can be converted into the inorganic porous framework; at least one selected from a ceramic precursor, a porous material of a carbonizable organic substance, or a porous material of a mixture of carbonizable organic substances.

The carbon material precursor is at least one of graphene oxide, modified carbon nanotubes, modified carbon nanofibers, modified graphite, modified carbon black, modified carbon fibers and a carbonizable organic substance or a carbonizable organic substance mixture. The modified carbon nanotube, modified carbon nanofiber, modified graphite, modified carbon black and modified carbon fiber refer to carbon materials that are pretreated, for example, pretreated by using a dispersant or a surfactant or pretreated by grafting a hydrophilic group, in order to improve the dispersibility of the carbon materials in water or an organic solvent to obtain a stable dispersion liquid; these pretreatment means are those of the prior art which improve dispersibility. Carbon materials subjected to the above pretreatment, such as graphene aqueous dispersion, graphene ethanol dispersion, graphene aqueous slurry, graphene oil-based slurry, graphene oxide aqueous dispersion, graphene oxide ethanol dispersion, graphene oxide N-methylpyrrolidone dispersion, carbon nanotube aqueous dispersion, carboxylated carbon nanotube aqueous dispersion, carbon nanotube ethanol dispersion, carbon nanotube dimethylformamide dispersion, carbon nanotube N-methylpyrrolidone slurry, and the like, can also be commercially available.

The solvent of the carbon material or the precursor solution or dispersion thereof in the step a can be selected from one or a combination of benzene, toluene, xylene, trichlorobenzene, chloroform, cyclohexane, ethyl hexanoate, butyl acetate, carbon disulfide, ketone, acetone, cyclohexanone, tetrahydrofuran, dimethylformamide, water or alcohols;

wherein the alcohol is preferably at least one selected from propanol, n-butanol, isobutanol, ethylene glycol, propylene glycol, 1, 4-butanediol, isopropanol, and ethanol.

The precursor of the carbon material for loading in the preparation method of the invention is preferably a precursor which can be dissolved or dispersed in a solvent which is friendly to human body and environment before loading, so that the preparation process is 'green'. The solvent friendly to human body and environment is at least one selected from ethanol, water and mixture of the two. I.e. the solvent in step a is more preferably a solvent comprising water and/or ethanol; further preferably water and/or ethanol.

The solution or dispersion liquid in step a can be used to fully dissolve or fully disperse the carbon material and/or carbon material precursor in the solvent, and the concentration of the solution or dispersion liquid is usually 0.001-1 g/mL, preferably 0.002-0.8 g/mL, and more preferably 0.003-0.5 g/mL.

More specifically:

when the carbon material supported on the inorganic porous skeleton in the preparation method of the present invention is graphene, the graphene oxide aqueous solution is preferably used in step a.

When the carbon material loaded on the inorganic porous framework in the preparation method of the present invention is a carbon nanotube, the carbon nanotube dispersion liquid is preferably used in step a.

When the carbon material precursor for loading in the preparation method is selected from thermosetting plastics, a proper curing system is prepared according to a curing formula commonly used in the prior art of the selected thermosetting plastics in the step a; optionally, one or more additives selected from the group consisting of: cure accelerators, dyes, pigments, colorants, antioxidants, stabilizers, plasticizers, lubricants, flow modifiers or adjuvants, flame retardants, drip retardants, antiblock agents, adhesion promoters, conductive agents, polyvalent metal ions, impact modifiers, mold release aids, nucleating agents, and the like; the dosage of the used additives is conventional dosage or is adjusted according to the requirements of actual conditions. And c, when the carbon material precursor for loading is selected from thermosetting plastics, the thermosetting resin serving as the carbon material precursor is cured after being heated in the subsequent step c, and is loaded on the inorganic porous framework.

When the carbon material precursor for loading in the preparation method is thermosetting plastic, a good solvent corresponding to the prior art is selected in the step a to dissolve the thermosetting plastic and the curing system thereof, so as to obtain the carbon material precursor solution for loading.

When the carbon material precursor for loading in the preparation method of the invention is thermoplastic plastic, common additives in the prior art in the plastic processing process, such as antioxidant, antioxidant aid, heat stabilizer, light stabilizer, ozone stabilizer, processing aid, plasticizer, softener, anti-blocking agent, foaming agent, dye, pigment, wax, extender, organic acid, flame retardant, coupling agent and the like, can be added into the solution of the carbon material precursor for loading. The dosage of the used auxiliary agent is conventional dosage or is adjusted according to the requirements of actual conditions.

In the step b of the preparation method of the present invention, the pores of the inorganic porous skeleton may be filled with the carbon material for loading or the carbon material precursor solution or dispersion by pressing several times or without pressing at all.

After the porous material obtained in step b is taken out in step c of the preparation method of the present invention, the excess solution or dispersion of the carbon material or carbon material precursor for loading in the porous material obtained in step b may be removed with or without measures, including but not limited to one or both of squeezing and centrifuging.

The heating in steps c and d of the preparation method of the present invention may preferably be microwave heating, which is not only efficient but also uniformly heated, specifically:

the power of the microwave in the step c is 1W-100 KW, preferably 500W-10 KW, and the microwave time is 2-200 min, preferably 20-200 min.

The microwave power of the step d is changed into 100W-100 KW, preferably 700W-20 KW; the microwave time is 0.5-200 min, preferably 1-100 min.

The heating in step d of the preparation method of the present invention is desirably carried out under an inert gas atmosphere selected from those commonly used in the art, preferably nitrogen.

The equipment adopted in the preparation method of the invention is common equipment.

As mentioned above, the preparation method of the porous composite material combines the inorganic porous framework and the carbon material, the prepared porous composite material has excellent mechanical property, can generate electric arc in a microwave field to quickly generate high temperature, for example, the electric arc which can heat the porous composite material to more than 1000 ℃ can be generated in a 900w microwave field, the material is high temperature resistant, the process flow is simple and easy, and the large-scale preparation is easy to realize.

The waste polyethylene in the invention refers to polyethylene used and finally eliminated or replaced in civil and industrial use and the mixture thereof, and the polyethylene comprises at least one of but not limited to low density polyethylene, linear low density polyethylene, medium density polyethylene, high density polyethylene and ultrahigh molecular weight polyethylene, and preferably at least one of low density polyethylene, linear low density polyethylene and high density polyethylene.

The microwave field in the method of the present invention can be applied to various microwave devices in the prior art, such as household microwave ovens, industrial microwave devices (such as microwave thermal cracking reactors), etc.

The device for placing or bearing the waste polyethylene and the porous composite material in the method can select various containers or pipelines which can be penetrated by microwaves and can resist the high temperature of more than 1200 ℃ in the prior art, such as quartz crucibles, quartz reactors, quartz tubes, alumina crucibles, alumina reactors, alumina tubes and the like.

According to the method, waste polyethylene is cracked and gasified, and the gas obtained after cracking is collected and can be subjected to subsequent treatment, such as gas is separated and then used as fuel or used as a chemical industrial raw material to perform subsequent reaction and production; and treating the cracked residue as waste.

The gas collection is a method common in the art, preferably under an inert atmosphere. For example, if a household microwave oven is used as the microwave field, the gas collection mode is as follows: putting a quartz crucible bearing waste plastics and porous composite materials into a vacuum bag in a glove box protected by nitrogen, sealing, twisting the crucible through the vacuum bag after reaction under microwave, and pricking the vacuum bag into a needle cylinder for sampling; the gas collection method adopts an industrial microwave oven (such as a microwave thermal cracking reactor and the like) with a gas inlet and a gas outlet, and comprises the following steps: the reaction process is purged by nitrogen, and the gas outlet is sampled and collected by a gas collection bag.

The method of the invention utilizes the porous composite material which generates electric arc in the microwave to generate electric arc in the microwave, thereby quickly generating high temperature, leading the waste polyethylene to be cracked into chemical raw materials, having high process efficiency and high added value of the composition of products.

Detailed Description

The present invention will be further described with reference to the following examples; however, the present invention is not limited to these examples.

The experimental data in the examples were determined using the following instruments and methods:

1. determination of the mass percentage content of the carbon material loaded in the porous composite material obtained in the examples:

1) under the condition that the inorganic porous framework material is adopted in the raw materials, firstly, the weight of the inorganic porous framework material is measured, the weight of the obtained porous composite material is measured after the experiment is finished, and the weight difference between the weight of the inorganic porous framework material and the weight of the obtained porous composite material is the weight of the loaded carbon material, so that the mass percentage content of the loaded carbon material in the porous composite material is measured;

2) under the condition that the inorganic porous framework precursor is adopted in the raw materials, taking two parts of inorganic porous framework precursors with the same weight, wherein one part is taken as an embodiment, and the other part is taken as a blank sample to only carry out the step c and the step d of the preparation method; after the experiment is finished, weighing the weight of the porous composite material obtained in the embodiment, weighing the final weight of the blank sample, and determining the weight difference between the two weights as the weight of the loaded carbon material, thereby determining the mass percentage content of the loaded carbon material in the porous composite material.

2. The gas thus decomposed was analyzed by gas chromatography using Agilent6890N (Agilent Co., U.S.A.).

The raw materials of the examples of the present invention are all commercially available.

Preparation of porous composite materials：

Example 1

(1) Measuring 500ml of graphene oxide aqueous dispersion (JCGO-95-1-2.6-W, 10mg/ml, Nanjing Jicang nanometer technology Co., Ltd.) in a beaker;

(2) soaking 2g of a porous skeleton (phenolic foam, average pore diameter of 300 mu m, porosity of 99%, Uyghur oasis flower foam Co., Ltd.) made of phenolic resin into graphene oxide aqueous dispersion, and making the solution fully enter the pore channels of the porous skeleton;

(3) taking out the soaked porous material, placing the porous material in a stainless steel tray, placing the stainless steel tray in a 180 ℃ oven for heating for 1 hour, drying and pre-reducing;

(4) and (3) placing the dried porous material into a household microwave oven (700w) for high-fire microwave treatment for 2min, reducing the pre-reduced graphene oxide into graphene, carbonizing a phenolic resin framework into a carbon framework (the average pore diameter is 200 mu m, the porosity is 99%), and obtaining the graphene-loaded carbon porous framework porous composite material generating electric arcs in the microwave, wherein the graphene accounts for 10% of the total mass of the porous composite material.

Example 2

(1) Measuring 500ml of carbon nanotube dispersion (XWDM, 100mg/ml, Nanjing Xiancheng nanomaterial science and technology Co., Ltd.) in a beaker;

(2) soaking 2g of a porous skeleton (phenolic foam, average pore diameter 200 μm, porosity 99%, perennial oasis flower foam limited) made of phenolic resin into the carbon nanotube dispersion liquid, so that the carbon nanotube dispersion liquid fully enters the pore channels of the porous skeleton;

(3) taking out the soaked porous material, placing the porous material in a stainless steel tray, placing the stainless steel tray in an oven at 80 ℃ for heating for 5 hours, and drying;

(4) and putting the dried porous material into a tube furnace, and carbonizing for 1h at 800 ℃ in a nitrogen atmosphere to obtain the carbon nanotube-supported carbon porous skeleton porous composite material (the average pore diameter of the carbon skeleton is 140 microns, the porosity is 99%) which generates electric arcs in the microwave, wherein the carbon nanotube accounts for 30% of the total mass of the porous composite material.

Example 3

(2) soaking 5g of fibrous cotton-shaped porous skeleton (average pore diameter 150 μm, porosity 90%, Shandong Luyang energy-saving material Co., Ltd.) made of silicate into the carbon nanotube dispersion liquid, and extruding for several times to make the dispersion liquid fully enter the pore channels of the porous skeleton;

(3) and taking out the soaked porous material, putting the porous material into a stainless steel tray, heating the stainless steel tray in a drying oven at 150 ℃ for 2 hours, and drying to obtain the porous composite material of the carbon nano tube-supported silicate fiber porous framework, which generates electric arcs in microwaves, wherein the carbon nano tube accounts for 10 percent of the total mass of the porous composite material.

Example 4

(1) Weighing 30g of powdered phenolic resin (2123, bermajafan industries, ltd. in new county) and 3.6g of hexamethylenetetramine curing agent in a beaker, pouring 500ml of ethanol, and stirring for 1 hour by using a magnetic rotor until the mixture is dissolved;

(2) soaking 5g of fibrous cotton-shaped porous skeleton (average pore diameter 150 μm, porosity 90%, Shandong Luyang energy-saving material Co., Ltd.) with silicate into the prepared solution, and extruding for several times to make the solution fully enter the pore channel of the porous skeleton;

(3) taking out the soaked porous material, placing the porous material in a stainless steel tray, placing the stainless steel tray in an oven at 180 ℃ for heating for 2 hours, drying the solution, and curing the phenolic resin;

(4) and putting the dried and cured porous material into a tubular furnace, carbonizing for 1h at 1000 ℃ in a nitrogen atmosphere, and carbonizing phenolic resin to obtain the porous composite material of the silicate fiber porous framework loaded by the phenolic resin carbonized product which generates electric arc in microwave, wherein the carbon material accounts for 5 percent of the total mass of the porous composite material.

Example 5

(1) Weighing 50g of liquid phenolic resin (2152, Jining Bai Yi chemical) in a beaker, pouring 500ml of ethanol, and stirring for 1 hour by using a magnetic rotor until the ethanol is dissolved;

(2) soaking 8g of a fiber plate-shaped porous framework (average pore diameter of 100 μm, porosity of 85%, Shandong Luyang energy-saving material Co., Ltd.) made of alumina into the prepared solution, and making the solution fully enter the pore channels of the porous framework;

(4) and putting the dried and cured porous material into a tubular furnace, carbonizing at 900 ℃ for 1h in a nitrogen atmosphere, and carbonizing phenolic resin to obtain the porous composite material of the alumina fiber porous skeleton loaded with the phenolic resin carbonization product generating electric arc in microwave, wherein the carbon material accounts for 6 percent of the total mass of the porous composite material.

Example 6

(1) Weighing 30g of water-soluble starch (pharmaceutical grade, Shanghai Aladdin Biotechnology Co., Ltd.) in a beaker, pouring 500ml of deionized water, and stirring with a magnetic rotor for 1 hour until dissolving;

(2) soaking 8g of fibrous felt-shaped porous framework (average pore diameter is 100 μm, porosity is 85%, Shandong Luyang energy-saving material Co., Ltd.) made of alumina into the prepared solution, and making the solution fully enter the pore channels of the porous framework;

(3) taking out the soaked porous material, placing into a microwave thermal cracking reactor (XOLJ-2000N, Nanjing Europe instruments manufacturing Co., Ltd.), performing microwave treatment with power of 10KW for 2min, and drying the porous material;

(4) and putting the dried porous material into a tubular furnace, carbonizing at 1200 ℃ for 1h in a nitrogen atmosphere, and carbonizing the water-soluble starch to obtain the porous composite material of the starch carbonization product loaded alumina fiber porous skeleton, which generates electric arc in microwave, wherein the carbon material accounts for 0.1 percent of the total mass of the porous composite material.

Example 7

(1) Weighing 50g of water-soluble starch (pharmaceutical grade, Shanghai Aladdin Biotechnology Co., Ltd.) in a beaker, pouring 500ml of deionized water, and stirring with a magnetic rotor for 1 hour until dissolving;

(2) soaking 8g of a fibrous cotton-shaped porous framework (average pore diameter of 100 μm, porosity of 85%, Shandong Luyang energy-saving material Co., Ltd.) made of alumina into the prepared solution, and extruding for several times to make the solution fully enter the pore channels of the porous framework;

(3) taking out the soaked porous material, placing into a microwave thermal cracking reactor (XOLJ-2000N, Nanjing Europe instruments manufacturing Co., Ltd.), performing microwave treatment with power of 500W for 2h, and drying the porous material;

(4) and putting the dried porous material into a tubular furnace, carbonizing for 1h at 1000 ℃ in a nitrogen atmosphere, and carbonizing starch to obtain the porous composite material of the starch carbonization product loading alumina fiber porous framework generating electric arc in microwave, wherein the carbon material accounts for 0.2 percent of the total mass of the porous composite material.

Example 8

(1) Weighing 2kg of liquid phenolic resin (2152, Jining Bai Yi chemical) in a beaker, pouring 4L of ethanol, and stirring with a magnetic rotor for 1 hour until dissolving;

(2) taking 2g of a prepared solution of a porous skeleton (phenolic foam, average pore diameter of 500 mu m, porosity of 99 percent, and evergreen flower foam Co., Ltd.) made of phenolic resin, and enabling the solution to fully enter pore channels of the porous skeleton;

(3) taking out the soaked porous material, putting the porous material in a stainless steel tray, putting the stainless steel tray in a drying oven at 150 ℃ for heating for 2 hours, and drying;

(4) the dried porous material is put into a microwave thermal cracking reactor (XOLJ-2000N, Nanjing Europe instruments manufacturing Co., Ltd.), microwave treatment is carried out for 100min under the nitrogen atmosphere with the power of 20KW, and the porous composite material (the average pore diameter of the carbon framework is 350 mu m, the porosity is 99%) of the carbon porous framework loaded with the phenolic resin carbonization product which generates electric arcs in the microwave is obtained, and the percentage of the carbon material loaded on the inorganic carbon framework in the total mass of the porous composite material is 80%.

Example 9

(1) Weighing 0.3g liquid phenolic resin (2152, JINING BAO YI CHEMICAL), placing in a beaker, adding 100ml ethanol, and stirring with magnetic rotor for 1 hr to dissolve;

(2) soaking 300g of activated alumina (average pore diameter of 0.05 μm, porosity of 30%, Shandong Kai Euro chemical engineering Co., Ltd.) in the prepared solution to make the solution fully enter the pore canal of the activated alumina;

(4) and putting the dried porous material into a tubular furnace, carbonizing for 1h at 1000 ℃ in a nitrogen atmosphere, and carbonizing phenolic resin to obtain the phenolic resin carbonized product loaded active alumina (porous framework) porous composite material generating electric arc in microwave, wherein the carbon material accounts for 0.05 percent of the total mass of the porous composite material.

Example 10

(2) soaking 8g of a fibrous plate-shaped porous framework (average pore diameter of 100 mu m, porosity of 80%, and Jinnan Pitaya thermal ceramics Limited liability company) made of magnesium oxide into the prepared solution, and making the solution fully enter the pore channels of the porous framework;

(4) and putting the dried and cured porous material into a tubular furnace, carbonizing for 1h at 1000 ℃ in a nitrogen atmosphere, and carbonizing phenolic resin to obtain the porous composite material of the phenolic resin carbonized product loaded with the magnesium oxide fiber porous framework, wherein electric arcs are generated in microwaves, and the carbon material accounts for 3 percent of the total mass of the porous composite material.

Example 11

(1) Weighing 100g of water-soluble starch (pharmaceutical grade, Shanghai Aladdin Biotechnology Co., Ltd.) in a beaker, pouring 500ml of deionized water, and stirring with a magnetic rotor for 1 hour until dissolving;

(2) soaking 8g of a fibrous plate-shaped porous framework (with the average pore diameter of 150 mu m and the porosity of 80 percent, and Vietnam fire ceramics Limited liability company) made of zirconia into the prepared solution, and enabling the solution to fully enter pore channels of the porous framework;

(3) taking out the soaked porous material, placing into a microwave thermal cracking reactor (XOLJ-2000N, Nanjing Europe instruments manufacturing Co., Ltd.), performing microwave treatment with power of 3KW for 20min, and drying the porous material;

(4) and putting the dried porous material into a tubular furnace, carbonizing at 900 ℃ for 2h in a nitrogen atmosphere, and carbonizing starch to obtain the porous composite material of the zirconium oxide fiber porous skeleton loaded with the starch carbonization product which generates electric arc in microwave, wherein the percentage of the carbon material in the total mass of the porous composite material is 0.5%.

Example 12

(2) soaking 8g of a fiber plate-shaped porous framework (average pore diameter is 100 mu m, porosity is 80%, and Vietnam fire ceramics Limited liability company) made of boron nitride into the prepared solution, and making the solution fully enter the pore channels of the porous framework;

(4) and putting the dried and cured porous material into a tubular furnace, carbonizing for 1h at 900 ℃ in a nitrogen atmosphere, and carbonizing phenolic resin to obtain the porous composite material of the phenolic resin carbonized product loaded boron nitride fiber porous skeleton, which generates electric arc in microwave, wherein the carbon material accounts for 5 percent of the total mass of the porous composite material.

Example 13

(1) Weighing 100g of liquid phenolic resin (2152, Jining Bai Yi chemical) in a beaker, adding 500ml of ethanol, and stirring with a magnetic rotor for 1 hour until the solution is dissolved;

(2) soaking 8g of a fiber plate-shaped porous framework (average pore diameter of 100 mu m, porosity of 80%, and Vietnam fire ceramics Limited liability company) made of silicon carbide into the prepared solution, and making the solution fully enter the pore channels of the porous framework;

(4) and putting the dried and cured porous material into a tubular furnace, carbonizing at 800 ℃ for 1h in a nitrogen atmosphere, and carbonizing phenolic resin to obtain the porous composite material of the phenolic resin carbonized product loaded silicon carbide fiber porous skeleton, which generates electric arc in microwave, wherein the carbon material accounts for 10 percent of the total mass of the porous composite material.

Example 14

(2) soaking 8g of a fibrous plate-shaped porous framework (average pore diameter is 100 mu m, porosity is 80%, and Vietnam fire ceramics Limited liability company) made of potassium titanate into the prepared solution, and making the solution fully enter pore channels of the porous framework;

(4) and putting the dried and cured porous material into a tubular furnace, carbonizing at 800 ℃ for 1h in a nitrogen atmosphere, and carbonizing phenolic resin to obtain the porous composite material of the potassium titanate fiber porous skeleton loaded by the phenolic resin carbonized product which generates electric arc in microwave, wherein the carbon material accounts for 10 percent of the total mass of the porous composite material.

Microwave cracking waste polyethylene：

Example 15

0.5g of beverage bottle cap (HDPE) and greenhouse film (LLDPE) are cut or weighed and placed on 1g of the porous composite material which generates electric arc in microwave obtained in example 1 respectively, and after protection of nitrogen, high-fire microwave pyrolysis is adopted in a household microwave oven (700w) for 30 s. With the aid of the porous composite material which generates electric arcs in the microwaves obtained in example 1, all materials are cracked and gasified after being treated by short 30s of microwave in a household microwave oven (700w), almost no residue is left, and a violent electric arc discharge phenomenon exists in the process. The porous composite material generates electric arc in microwave, so that high temperature is generated rapidly and transferred to the material to make the material cracked rapidly.

50g of beverage bottle cap (HDPE) and 10g of greenhouse film (LLDPE) were cut and placed in a chamber made of 30g of the porous composite material generating an arc in the microwave obtained in example 1, respectively, and after protection with nitrogen, treated with 1500W power for 5min in a microwave pyrolysis reactor (XOLJ-2000N, manufactured by Nanjin Europe instruments Co., Ltd.). Almost no residue was found in all the materials.

The specific operation of placing the material to be cracked in a cavity formed by porous composite materials which generate electric arcs in microwaves is as follows: firstly, a part of porous composite materials which generate electric arcs in microwaves are placed at the bottom and around a quartz reactor to form a cavity with an upper opening, then materials are placed in the cavity, and finally the rest of porous composite materials cover the upper parts of the materials.

The same experiment as described above was performed on the samples obtained in examples 2 to 14, and similar experimental phenomena and results were obtained. The porous composite materials obtained in examples 2 to 14 were all arc-generated in the microwave, thereby rapidly generating high temperature and transferring the high temperature to the materials to rapidly crack the materials.

Comparative example 1

0.5g of pieces of beverage bottle caps (HDPE) were put on 1g of silicon carbide powder (98.5%, Beijing, Inc., a chemical reagent of the national drug group), protected with nitrogen, and then subjected to microwave treatment for 30 seconds in a domestic microwave oven (700w) using a high fire. No spark is generated in the microwave process, the HDPE bottle cap is not changed after the microwave treatment, and only the bottom of the quartz crucible is slightly warm.

Example 16

The parameters and procedure were as in example 15, except for the following:

a sample of 1g obtained in example 1 was subjected to a chromatographic analysis of a gas obtained by cracking 0.5g of HDPE and 0.5g of LLDPE respectively in a domestic microwave oven (700W) for 30 seconds, and the main components thereof are shown in Table 1.

A30 g sample of the product obtained in example 6 was subjected to a microwave thermal cracking reactor to crack 50g of HDPE and 50g of LLDPE respectively at 1500W power for 15 minutes, and the gas was subjected to a chromatographic analysis, wherein the main components are shown in Table 2.

TABLE 1

TABLE 2

Claims

1. A method for microwave pyrolysis of waste polyethylene is characterized by comprising the following steps:

the waste polyethylene is contacted with the porous composite material, a microwave field is applied to the waste polyethylene and the porous composite material under inert atmosphere or vacuum, and the porous composite material generates electric arc under microwave, so that the high temperature is quickly reached, and the waste polyethylene is cracked; the weight ratio of the waste polyethylene to the porous composite material is 1: 99-99: 1;

the microwave power of the microwave field is 200W-100 KW; the microwave time is 0.5-150 min;

the porous composite material comprises: an inorganic porous skeleton and a carbon material supported on the inorganic porous skeleton; the carbon material accounts for 0.001% -99% of the total mass of the porous composite material;

the inorganic porous skeleton is an inorganic material having a porous structure; the average pore diameter of the inorganic porous framework is 0.01-1000 microns; the porosity is 1% -99.99%; the inorganic material is one or a combination of carbon, silicate, aluminate, borate, phosphate, germanate, titanate, oxide, nitride, carbide, boride, sulfide, silicide and halide;

the carbon material is at least one of graphene, carbon nanotubes, graphite, carbon black, carbon fibers, carbon dots, carbon nanowires, a product obtained by carbonizing a carbonizable organic substance, or a product obtained by carbonizing a mixture of carbonizable organic substances.

2. The microwave pyrolysis method for waste polyethylene according to claim 1, characterized by comprising the following steps:

the weight ratio of the waste polyethylene to the porous composite material is 1: 50-50: 1; and/or the presence of a gas in the gas,

the carbon material accounts for 0.01-90% of the total mass of the porous composite material; and/or the presence of a gas in the gas,

the carbon material is at least one of graphene, a carbon nanotube, a carbon nanofiber, a product obtained by carbonizing a carbonizable organic substance, and a product obtained by carbonizing a mixture of carbonizable organic substances.

3. The microwave pyrolysis method for waste polyethylene according to claim 2, characterized by comprising the following steps:

the weight ratio of the waste polyethylene to the porous composite material is 1: 30-30: 1; and/or the presence of a gas in the gas,

the carbon material accounts for 0.1-80% of the total mass of the porous composite material.

4. The microwave pyrolysis method for waste polyethylene according to claim 1, characterized by comprising the following steps:

the inorganic material is at least one of carbon, silicate, titanate, oxide, carbide, nitride and boride.

5. The microwave pyrolysis method for waste polyethylene according to claim 4, characterized by comprising the following steps:

the oxide is at least one of aluminum oxide, silicon oxide, zirconium oxide, magnesium oxide, cerium oxide and titanium oxide; and/or the presence of a gas in the gas,

the nitride is at least one of silicon nitride, boron nitride, zirconium nitride, hafnium nitride and tantalum nitride; and/or the presence of a gas in the gas,

the carbide is at least one of silicon carbide, zirconium carbide, hafnium carbide and tantalum carbide; and/or the presence of a gas in the gas,

the boride is at least one of zirconium boride, hafnium boride and tantalum boride.

6. The microwave pyrolysis method for waste polyethylene according to claim 1, characterized by comprising the following steps:

the average pore diameter of the inorganic porous framework is 0.05-500 mu m, and the porosity is 10% -99.9%.

7. The microwave pyrolysis method for waste polyethylene according to claim 6, characterized by comprising the following steps:

the average pore diameter of the inorganic porous framework is 0.2-250 mu m; and/or the porosity of the inorganic porous framework is 30-99%.

8. The microwave pyrolysis method for waste polyethylene according to claim 1, characterized by comprising the following steps:

the inorganic porous framework is at least one of the following: the carbon skeleton obtained after carbonization of the polymer sponge, the porous skeleton formed by inorganic fibers, the inorganic sponge skeleton, the skeleton formed by accumulation of inorganic particles, the ceramic sponge skeleton obtained after roasting of a ceramic precursor sponge and the ceramic fiber skeleton obtained after roasting of ceramic precursor fibers.

9. The microwave pyrolysis method for waste polyethylene according to claim 8, wherein:

the inorganic porous framework is at least one of the following: the composite material comprises a framework obtained by carbonizing melamine sponge, a framework obtained by carbonizing phenolic resin sponge, a porous framework of aluminum silicate fiber, a porous framework of mullite fiber, a porous framework of alumina fiber, a porous framework of zirconia fiber, a porous framework of magnesia fiber, a porous framework of boron nitride fiber, a porous framework of boron carbide fiber, a porous framework of silicon carbide fiber, a porous framework of potassium titanate fiber and a ceramic fiber framework obtained by roasting ceramic precursor fiber.

10. The microwave pyrolysis method for waste polyethylene according to claim 1, characterized by comprising the following steps:

11. The microwave pyrolysis method for waste polyethylene according to claim 10, wherein:

the mixture of the carbonizable organic matters is at least one of coal, natural asphalt, petroleum asphalt or coal tar asphalt.

12. The microwave pyrolysis method for waste polyethylene according to claim 1, characterized by comprising the following steps:

the organic matter capable of being carbonized is an organic high molecular compound, and the organic high molecular compound comprises a synthetic high molecular compound and a natural organic high molecular compound.

13. The microwave pyrolysis method for waste polyethylene according to claim 12, wherein:

the synthetic high molecular compound is rubber or plastic; the plastics include thermosets and thermoplastics; and/or the presence of a gas in the gas,

the natural organic high molecular compound is at least one of starch, viscose, lignin and cellulose.

14. The microwave pyrolysis method for waste polyethylene according to claim 13, wherein:

the synthetic high molecular compound is at least one selected from epoxy resin, phenolic resin, furan resin, polystyrene, styrene-divinylbenzene copolymer, polyacrylonitrile, polyaniline, polypyrrole, polythiophene, styrene butadiene rubber and polyurethane rubber.

15. The microwave pyrolysis method for waste polyethylene according to claim 1, wherein the porous composite material is prepared according to a method comprising the following steps:

a. preparing a carbon material for loading and/or a carbon material precursor solution or dispersion liquid;

b. b, immersing an inorganic porous framework or an inorganic porous framework precursor into the solution or the dispersion liquid obtained in the step a to fill the pores of the inorganic porous framework or the inorganic porous framework precursor with the solution or the dispersion liquid; the carbon material and/or the carbon material precursor accounts for 0.001-99.999% of the total mass of the inorganic porous framework material or the inorganic porous framework material precursor and the carbon material and/or the carbon material precursor;

c. taking out the porous material obtained in the step b, heating, drying, separating out or curing a carbon material or a carbon material precursor, and loading the carbon material or the carbon material precursor on an inorganic porous framework or an inorganic porous framework precursor; heating and drying at 50-250 ℃;

d. c, heating the porous material obtained in the step c in an inert gas atmosphere, converting an inorganic porous skeleton precursor into an inorganic porous skeleton, and/or reducing or carbonizing a carbon material precursor to obtain a porous composite material for generating electric arcs in the microwaves; the heating temperature is 400-1800 ℃.

16. The microwave pyrolysis method for waste polyethylene according to claim 15, wherein:

the carbon material and/or carbon material precursor accounts for 0.01-99.99% of the total mass of the inorganic porous framework material or the inorganic porous framework material precursor and the carbon material and/or carbon material precursor in the step b; and/or the presence of a gas in the gas,

the heating and drying temperature of the step c is 60-200 ℃; and/or the presence of a gas in the gas,

and d, heating at 600-1500 ℃.

17. The microwave pyrolysis method for waste polyethylene according to claim 16, wherein:

the carbon material and/or carbon material precursor accounts for 0.1-99.9% of the total mass of the inorganic porous framework material or the inorganic porous framework material precursor and the carbon material and/or carbon material precursor in the step b; and/or the presence of a gas in the gas,

the heating and drying temperature of the step c is 80-180 ℃; and/or the presence of a gas in the gas,

and d, heating at the temperature of 800-1200 ℃.

18. The microwave pyrolysis method for waste polyethylene according to claim 15, wherein:

19. The microwave pyrolysis method for waste polyethylene according to claim 15, wherein:

the carbon material precursor is at least one of graphene oxide, modified carbon nanotubes, modified graphite, modified carbon black, modified carbon fibers and a carbonizable organic substance or a carbonizable organic substance mixture.

20. The microwave pyrolysis method for waste polyethylene according to claim 19, wherein:

the modified carbon fiber is selected from modified carbon nanofiber.

21. The microwave pyrolysis method for waste polyethylene according to claim 15, wherein:

and (b) the solvent of the carbon material or the precursor solution or dispersion liquid thereof in the step a is selected from one or a combination of benzene, toluene, xylene, trichlorobenzene, chloroform, cyclohexane, ethyl hexanoate, butyl acetate, carbon disulfide, ketone, acetone, cyclohexanone, tetrahydrofuran, dimethylformamide, water or alcohols.

22. The microwave pyrolysis method for waste polyethylene according to claim 21, wherein:

the alcohol is selected from at least one of propanol, n-butanol, isobutanol, ethylene glycol, propylene glycol, 1, 4-butanediol, isopropanol and ethanol.

23. The microwave pyrolysis method for waste polyethylene according to claim 21, wherein:

the solvent of the carbon material or precursor solution or dispersion thereof of step a is selected from solvents comprising water and/or ethanol.

24. The microwave pyrolysis method for waste polyethylene according to claim 23, wherein:

and (b) the solvent of the carbon material or the precursor solution or dispersion liquid of the carbon material in the step a is selected from water and/or ethanol.

25. The microwave pyrolysis method for waste polyethylene according to claim 15, wherein:

the concentration of the solution or dispersion liquid in the step a is 0.001-1 g/mL.

26. The microwave pyrolysis method for waste polyethylene according to claim 25, wherein:

the concentration of the solution or dispersion liquid in the step a is 0.002-0.8 g/mL.

27. The microwave pyrolysis method for waste polyethylene according to claim 26, wherein:

the concentration of the solution or the dispersion liquid in the step a is 0.003 g-0.5 g/mL.

28. The microwave pyrolysis method for waste polyethylene according to claim 15, wherein:

the heating in the step c and the step d is microwave heating;

the microwave power of the step c is 1W-100 KW, and the microwave time is 2-200 min;

the microwave power of the step d is 100W-100 KW, and the microwave time is 0.5-200 min.

29. The microwave pyrolysis method for waste polyethylene according to claim 28, wherein:

the microwave power of the step c is 500W-10 KW; and/or the presence of a gas in the gas,

the microwave time of the step c is 20-200 min; and/or the presence of a gas in the gas,

the microwave power of the step d is 700W-20 KW; and/or the presence of a gas in the gas,

and d, the microwave time in the step d is 1-100 min.

30. The microwave pyrolysis method for waste polyethylene according to any one of claims 1 to 29, wherein:

the microwave power of the microwave field is 300W-50 KW, and the microwave time is 1-120 min.

31. The microwave pyrolysis method for waste polyethylene according to claim 30, wherein:

the microwave power of the microwave field is 500W-20 KW; and/or the microwave time of the microwave field is 2-100 min.