Method for simultaneously recycling polyolefin and carbon dioxide by using microwaves and application thereof

Abstract

The invention relates to the technical field of polyolefin treatment, and discloses a method for simultaneously recycling polyolefin and carbon dioxide by using microwaves, which comprises the following steps: contacting polyolefin with a carbon fiber aggregate, and applying microwaves to the polyolefin and carbon fiber aggregate in the atmosphere of gas containing carbon dioxide, polyolefin reacts with carbon dioxide to be converted into a gas product with carbon monoxide as a main component; the carbon fiber aggregate comprises a plurality of carbon fiber basic units which are arranged in a non-directional mode, each carbon fiber basic unit is a carbon fiber bundle formed by a single carbon fiber and / or a plurality of carbon fibers, the two ends of each carbon fiber in the length direction serve as the tail ends of the carbon fibers, and the number of the carbon fiber tail ends is equal to the number of the carbon fiber basic units. The number of carbon fiber ends contained in each gram of the carbon fiber aggregate is 1 * 106 / g or more. Polyolefin is efficiently cracked by using the carbon fiber aggregate, and polyolefin and carbon dioxide are efficiently converted into synthesis gas with carbon monoxide as a main component at the same time.

Description

Technical Field

[0001] The invention relates to the technical field of polyolefin processing, and in particular to a method for simultaneously recycling polyolefin and carbon dioxide by using microwaves and an application thereof. Background Art

[0002] Polyolefin materials refer to thermoplastic polymer materials polymerized from ethylene, propylene, butene or α-olefins, including polyethylene (PE), polypropylene (PP), ethylene-vinyl acetate copolymer (EVA), etc., which are commonly used in people's lives. At present, the global total production of polyolefins exceeds 220 million tons / year, which is widely used in medical and health, agriculture, transportation, electronic appliances, construction and home furnishing, energy conservation and environmental protection, new energy and other fields. It is the world's largest and most widely used polymer material. my country is the world's largest producer and consumer of polyolefins. In 2020, the total production capacity has reached 53 million tons / year, and the total consumption has exceeded 66 million tons / year. However, since the main chain chemical bond of polyolefins is a carbon-carbon bond and has good chemical stability, polyolefins are not easy to degrade in the natural environment, and are difficult to decompose and treat even under strong acid and strong alkali conditions. This also makes waste polyolefins an important source of environmental pollution, usually white pollution. Although polyolefins can be recycled by thermoplastic processing, the addition and use of additives in the recycling process will cause polyolefins to be unable to be permanently recycled through physical recycling. Ultimately, chemical recycling methods are still needed to process polyolefins into chemical raw materials or fuels. High-temperature cracking is the most effective method for processing waste polyolefin materials, but tar and carbon deposits are easily formed during the high-temperature cracking process. This will reduce the heat transfer efficiency of the cracking furnace. If the tar in the cracking product is not treated, it will gradually cool down when it is carried through the pipeline, forming a viscous liquid that adheres to the pipeline, causing corrosion, scaling, blockage and other problems that threaten the safety of pipelines and equipment.

[0003] Plasma is the fourth state of matter besides solid, liquid and gas. Its characteristic is that the plasma state is highly dependent on the electromagnetic field. The material composition of plasma is unbound ions and free electrons, and the overall state of plasma is electrically neutral. Microwaves refer to electromagnetic waves with wavelengths between infrared and ultra-high frequency (UHF) radio waves, with very strong penetrating power. Its wavelength is between 1m and 1mm, and the corresponding frequency is 300GHz-300MHz. Microwave plasma technology is a technology that generates plasma by microwave irradiation, which can achieve an energy conversion efficiency of more than 60% under non-equilibrium conditions of plasma. Microwave plasma has a significant thermal effect. The Chinese invention patent CN111100661A we applied for, the porous composite material prepared can generate a high temperature of more than 1000℃ by microwave irradiation in a nitrogen atmosphere, thereby quickly cracking polyolefins. However, the porous composite materials prepared by these two patents are rigid structural materials, which are brittle and easy to damage, which is not conducive to long-term use, and cannot solve the problem that polyolefin cracking will produce a large amount of tar and coke.

[0004] Extreme climate and energy crisis are two major challenges that mankind needs to face in this century. As we all know, carbon dioxide is the main greenhouse gas, and the occurrence of global extreme climate is mainly affected by the increase in global carbon dioxide emissions. Therefore, the treatment of carbon dioxide has become an issue that the whole society needs to pay attention to and solve. The utilization of carbon dioxide can be divided into four categories: chemical synthesis, fuel production, biological application and direct application. At present, the total annual carbon dioxide emissions in the world are about 35 billion tons / year. However, the total carbon dioxide consumption in the chemical industry, which uses the largest amount of carbon dioxide, is only about 220 million tons / year, which is a drop in the bucket compared to the total global carbon dioxide emissions. Among the current methods of converting carbon dioxide into energy fuels, the technology of converting carbon dioxide and water into synthesis gas is the most concerned. The reason is that synthesis gas is a traditional fuel energy, water resources are easy to obtain, and synthesis gas is also an important chemical energy storage medium.

[0005] Research has found that carbon dioxide can react with coke and tar under microwave high temperature to convert into carbon monoxide. Therefore, if a microwave heating material that is not easily damaged and can generate plasma in a microwave field containing a carbon dioxide atmosphere is designed and synthesized, the coke and tar produced by polyolefin cracking can be reduced, the utilization rate of polyolefin microwave cracking can be increased, and carbon dioxide can be recycled and utilized at the same time, achieving efficient recycling of carbon dioxide and polyolefin at the same time, which has a wide range of application markets. Summary of the invention

[0006] To solve the problems in the prior art, the present invention provides a method for simultaneously recycling polyolefin and carbon dioxide using microwaves and its application. The present invention utilizes a carbon fiber aggregate that can generate high temperature and plasma in a microwave field containing carbon dioxide gas to efficiently crack polyolefin, and utilizes the characteristics of polyolefin generating coke and tar and carbon dioxide being converted into carbon monoxide under microwave plasma and high temperature to simultaneously and efficiently convert polyolefin and carbon dioxide into synthesis gas with carbon monoxide as the main component.

[0007] The carbon fiber aggregate used in the present invention is based on the following findings of the inventors of the present invention: carbon fiber is a material that has both high strength and flexibility. Ordinary carbon fiber, such as T300 carbon fiber monofilament, has a tensile strength of up to 3500MPa and a tensile modulus of up to 230GPa. From a physical property point of view, although it can solve the problem of high brittleness and easy damage, since carbon fiber can both absorb and reflect microwaves, and weaving carbon fiber can only prepare microwave reflective materials, such practical applications show that carbon fiber is more inclined to reflect microwaves. At present, there is no precedent for pure carbon fiber to generate plasma through microwave irradiation as a microwave heating material. Through research, the inventors of the present invention unexpectedly found that by controlling the number of carbon fiber ends contained in each gram of the carbon fiber aggregate, a carbon fiber aggregate can be obtained. Although the carbon fiber aggregate is pure carbon fiber, it can generate plasma and a high temperature of more than 1000°C under microwave irradiation.

[0008] The object of the present invention is to provide a method for simultaneously recovering polyolefin and carbon dioxide using microwaves, comprising:

[0009] The polyolefin is brought into contact with the carbon fiber aggregate, and microwaves are applied to the polyolefin and the carbon fiber aggregate in an atmosphere of a gas containing carbon dioxide, so that the polyolefin reacts with the carbon dioxide to convert into a gas product having carbon monoxide as a main component;

[0010] The carbon fiber assembly comprises a plurality of randomly arranged carbon fiber basic units, wherein the carbon fiber basic unit is a single carbon fiber and / or a carbon fiber bundle formed by a plurality of carbon fibers;

[0011] The two ends of each carbon fiber in the length direction are the carbon fiber ends, and the number of carbon fiber ends contained in each gram of the carbon fiber aggregate is 1×10 6 Pieces / g or more.

[0012] Through the above technical scheme, the present invention brings polyolefin into contact with a carbon fiber aggregate, applies microwaves to the polyolefin and the carbon fiber aggregate in an atmosphere containing carbon dioxide gas, and the carbon fiber aggregate generates high temperature and plasma in the microwave field under the carbon dioxide atmosphere. Under the combined action of high temperature and plasma, the polyolefin and carbon dioxide are converted into a gas product (i.e., synthesis gas) with carbon monoxide as the main component.

[0013] In the present invention, the gas product with carbon monoxide as the main component means that, based on the volume content, the total volume of the gas product is 100%, the content of carbon monoxide in the gas product is 20% or more, preferably 40% or more, and more preferably 50% or more.

[0014] In a preferred embodiment of the present invention, the carbon fiber aggregate presents a two-dimensional or three-dimensional spatial structure.

[0015] In a preferred embodiment of the present invention, at least part of two or more adjacent carbon fiber basis units are in contact with each other; preferably, the contact includes at least one of abutting, overlapping and interlacing with each other.

[0016] In a preferred embodiment of the present invention, the number of carbon fiber ends contained in each gram of the carbon fiber aggregate is 1×10 6 ~6×10 8 / g, preferably 1×10 6 ~6×10 7 pcs / g, more preferably 1×10 6 ~2×10 7 Pieces / g.

[0017] In a preferred embodiment of the present invention, the carbon fiber bundle is a carbon fiber bundle filament fixed together; at least one fixed node is provided on the carbon fiber bundle filament; more preferably,

[0018] When there is only one fixed node on the carbon fiber bundle, the length of the carbon fiber bundle is 0.1 to 30 mm, preferably 1 to 20 mm, and more preferably 3 to 20 mm;

[0019] When more than two fixing nodes are provided on the carbon fiber bundle, the spacing between adjacent fixing nodes is 1 to 50 mm, preferably 2 to 30 mm, more preferably 5 to 20 mm; and part of the carbon fiber bundle between adjacent fixing nodes is in a disconnected state.

[0020] In a preferred embodiment of the present invention, the fixing includes bundling fixing and / or knotting fixing, and the fixing nodes include bundling nodes and / or knotting points. More preferably, the knotting fixing is that the carbon fiber bundles are fixed by knotting themselves; and / or the bundles of the bundling fixing are carbon fiber bundles.

[0021] The raw materials used for the carbon fiber aggregate described in the present invention can be purchased on the market. According to the present invention, the carbon fiber bundles can adopt various types of carbon fiber bundles in the prior art. In a preferred embodiment of the present invention, the carbon fiber bundles, the carbon fiber bundles for bundling, and the carbon fiber bundles for knotting are independently selected from at least one of the following types of carbon fiber bundles: T300, T700, T800, T1000, T1100, M40, M50, M60; preferably selected from at least one of the following types of carbon fiber bundles: T300, T700, T800; more preferably selected from at least one of the following types of carbon fiber bundles: T300, T700.

[0022] According to the present invention, there are multiple options for the number of carbon fibers contained in each bundle of carbon fiber bundles. In a preferred embodiment of the present invention, the number of carbon fibers contained in each bundle of carbon fiber bundles is 1K-48K, preferably 1K, 3K, 6K, 12K, 24K, 48K, more preferably 12K, 24K, and most preferably 12K.

[0023] According to the present invention, the carbon fiber assembly comprises a plurality of carbon fiber basic units arranged in an irregular manner, and the carbon fiber basic unit is a carbon fiber bundle formed by a single carbon fiber and / or a plurality of carbon fibers. In a preferred embodiment of the present invention, the carbon fiber basic unit is a carbon fiber bundle formed by a plurality of carbon fibers, or the carbon fiber basic unit comprises both a single carbon fiber and a carbon fiber bundle, or the carbon fiber basic unit is a single carbon fiber. More preferably, the carbon fiber basic unit is a carbon fiber bundle formed by a plurality of carbon fibers, or the carbon fiber basic unit comprises both a single carbon fiber and a carbon fiber bundle. In this more preferred embodiment, the carbon fiber assembly is easier to use and recycle.

[0024] In a more preferred embodiment of the present invention, when the carbon fiber basic unit contains both a single carbon fiber and a carbon fiber bundle, the total mass of the carbon fiber aggregate is 100wt%, and the content of the carbon fiber bundle in the carbon fiber aggregate is 0.1-99.9wt%, preferably 1-99wt%; and / or, the length of each fiber of the single carbon fiber is 0.1-30mm, preferably 1-20mm, more preferably 3-20mm; and / or, the diameter of the single carbon fiber is 5-10μm, and / or, the density is 1.5-2.0g / cm 3 .

[0025] The method for preparing a carbon fiber aggregate of the present invention comprises:

[0026] The single carbon fibers and / or carbon fiber bundles are assembled in a non-directional arrangement to obtain the carbon fiber aggregate; wherein the method for preparing the carbon fiber bundles includes fixing the carbon fiber bundles together and providing at least one fixed node on the carbon fiber bundles, and when more than two fixed nodes are provided on the carbon fiber bundles, the carbon fiber bundles between adjacent fixed nodes are partially disconnected or completely disconnected.

[0027] The described collection refers to the aggregation of scattered carbon fiber basic units, which are physically mixed rather than chemically connected to each other; for example, the collection of carbon fiber basic units is achieved by adopting a stacking aggregation method or a winding aggregation method, and then preferably at least two or more partially adjacent carbon fiber basic units are in contact with each other, and more preferably, at least two or more partially adjacent carbon fiber basic units are in contact with each other in at least one manner including adjacency, overlap, and interlacing.

[0028] In a preferred embodiment of the present invention, the fixing includes bundling and / or knotting.

[0029] In a preferred embodiment of the present invention, the disconnection includes cutting and / or shearing.

[0030] In a more preferred embodiment of the present invention, when there is only one fixed node on the carbon fiber bundle, the length of the carbon fiber bundle is 0.1-30 mm, preferably 1-20 mm, and more preferably 3-20 mm.

[0031] In a more preferred embodiment of the present invention, when there are more than two fixed nodes on the carbon fiber bundle, the spacing between adjacent fixed nodes is 1-50 mm, preferably 2-30 mm, and more preferably 5-20 mm.

[0032] The fixing includes bundling fixing and / or knotting fixing, and the fixing nodes include bundling nodes and / or knotting points. Preferably, the knotting fixing is performed by knotting the carbon fiber bundle itself; and / or, the bundling fixing adopts the carbon fiber bundle for bundling; more preferably, the knotting method is at least one of a single knot, a flat knot, a Bollinger knot, an Alpine bow knot, an Alpine bow knot, a double Alpine bow knot, a Blake knot, a clove knot, an 8-shaped single knot, and an 8-shaped connecting knot; for the knotting method, preferably at least one of a single knot, a flat knot, an Alpine bow knot, an Alpine bow knot, a double Alpine bow knot, an 8-shaped single knot, and an 8-shaped connecting knot; more preferably, at least one of a single knot, a flat knot, an Alpine bow knot, and an 8-shaped single knot.

[0033] The equipment used in the preparation method of the present invention is all commonly used equipment.

[0034] The above-mentioned method for preparing the carbon fiber aggregate directly uses high-strength carbon fiber as raw material. Through simple processing, a flexible, high-temperature resistant material that can generate a high temperature of more than 1000°C in a microwave field can be prepared. The process flow is simple and easy to implement, and large-scale preparation is easy.

[0035] In the present invention, the weight ratio of the polyolefin to the carbon fiber aggregate is preferably (1:100) to (100:1), preferably (1:50) to (50:1), and more preferably (1:30) to (30:1).

[0036] In the present invention, preferably, the gas containing carbon dioxide comprises pure carbon dioxide gas or a mixed gas containing carbon dioxide; more preferably,

[0037] The carbon dioxide-containing mixed gas is a mixed gas of carbon dioxide and an inert gas and / or water vapor; more preferably, the inert gas is at least one of nitrogen, argon and helium.

[0038] More preferably, the volume fraction of carbon dioxide in the carbon dioxide mixed gas is 5% to 99.9%, preferably 10% to 99.9%, and most preferably 20% to 99.9%.

[0039] According to the present invention, the power of the microwave can be selected within a wide range. In a preferred embodiment of the present invention, the power of the microwave is 1W to 100KW, preferably 200W to 50KW, and most preferably 500W to 20KW.

[0040] According to the present invention, the microwave time can be selected within a wide range. In a preferred embodiment of the present invention, the microwave time is 0.1 to 200 min, preferably 0.5 to 150 min, and most preferably 1 to 100 min.

[0041] In the present invention, the temperature of the carbon fiber aggregate exceeds 1000° C., so that the polyolefin is cracked.

[0042] The contacting method of the polyolefin and the carbon fiber assembly can be various, as long as the polyolefin and the carbon fiber assembly are in contact. Preferably, the contacting method of the polyolefin and the carbon fiber assembly includes: the polyolefin is placed on the carbon fiber assembly, placed in the cavity formed by the carbon fiber assembly, covered by the carbon fiber assembly, and mixed with the carbon fiber assembly. One or more combinations of the above methods.

[0043] According to the present invention, the polyolefin can be selected from a wide range. In a preferred embodiment of the present invention, the polyolefin is a polyolefin prepared by homopolymerization or copolymerization of at least one of ethylene, propylene, butene, α-olefin, cycloolefin, 4-methyl-1-pentene, and acrylic acid monomers, as well as a mixture of the polyolefins.

[0044] The polyolefin described in the present invention can be various types of polyethylene (PE), polypropylene (PP), poly 1-butene (PB-1), ethylene-vinyl acetate copolymer (EVA), polyolefin elastomer (POE), cycloolefin homopolymer / copolymer (COP / COC), poly 4-methyl-1-pentene (PMP), ethylene-vinyl alcohol copolymer (EVOH), ethylene-acrylic acid copolymer (EAA), etc., which are prepared by homopolymerization and copolymerization of ethylene, propylene, butene, α-olefin, cycloolefin, 4-methyl-1-pentene, acrylic acid monomers, etc., as well as mixtures of the above polyolefins.

[0045] Preferably, the polyolefin is at least one of polyethylene, polypropylene, poly-1-butene, ethylene-vinyl acetate copolymer, polyolefin elastomer, cycloolefin homopolymer / copolymer, poly-4-methyl-1-pentene, ethylene-vinyl alcohol copolymer, and ethylene-acrylic acid copolymer.

[0046] In a preferred embodiment of the present invention, the method comprises the following steps:

[0047] a. Removing small molecules from polyolefins;

[0048] b. placing the treated polyolefin and carbon fiber assembly in a sealable reaction container, wherein the reaction container is made of a microwave transparent material;

[0049] c. introducing a gas containing carbon dioxide into the reaction vessel to replace the air;

[0050] d. Start the microwave, place the reaction container under the microwave field to react, and collect the gas products generated by the reaction.

[0051] The method for simultaneously recycling polyolefin and carbon dioxide by using microwaves comprises the following steps:

[0052] a. The polyolefin is subjected to a small molecule removal treatment at 50°C-200°C for 1min-240min. The small molecule removal equipment may be a commercially available drying equipment, such as a blast dryer, a microwave oven, a thermal radiation instrument, etc., or the small molecule removal treatment may be carried out by sun exposure, air drying, etc., so that the polyolefin does not produce a thermal weight loss greater than 1% of its mass within 10 minutes at 200°C;

[0053] b. placing the polyolefin and the carbon fiber assembly together in any manner so that the polyolefin contacts the carbon fiber assembly;

[0054] c. introducing pure carbon dioxide or a mixture of carbon dioxide and one or more of the following: nitrogen, argon, helium, water vapor into the reaction system to replace the air;

[0055] d. Start the microwave and collect the gas products generated by the reaction.

[0056] The microwave field in the method of the present invention can adopt various microwave equipment in the prior art, such as household microwave ovens, industrial microwave equipment (such as microwave thermal cracking reactors), etc.

[0057] According to the present invention, the microwave transparent material means that microwaves can penetrate the wall of the reaction container made of the material and radiate to the sample.

[0058] The device for placing or carrying the polyolefin and carbon fiber aggregate in the method of the present invention can be selected from various containers or pipes in the prior art that can be penetrated by microwaves and withstand high temperatures above 1200°C, such as quartz crucibles, quartz reactors, quartz tubes, alumina crucibles, alumina reactors, alumina tubes, etc.

[0059] In the method of the present invention, polyolefin is cracked and then gasified, and the gas obtained after cracking is collected for subsequent treatment, such as being used as fuel or as a raw material for chemical industry for subsequent reaction and production after gas separation.

[0060] The gas product collection is a common method in the prior art, preferably carried out under an inert atmosphere. For example, if a microwave oven is used as a microwave field, the gas collection method is as follows: in a nitrogen-protected glove box, a quartz crucible carrying waste plastics and porous composite materials is placed in a vacuum bag and sealed, and after the reaction under microwave, the crucible is unscrewed through the vacuum bag, and a syringe is used to pierce the vacuum bag for sampling; an industrial microwave oven with an air inlet and an air outlet (such as a microwave thermal cracking reactor, etc.) is used, and the gas collection method is as follows: nitrogen is purged during the reaction process, and a gas collection bag is used at the air outlet for sampling and collection.

[0061] The second aspect of the present invention is to provide an application of the method for simultaneously recovering polyolefin and carbon dioxide using microwaves according to the first aspect in the recovery of polyolefin.

[0062] The carbon fiber aggregate described in the method for simultaneously recovering polyolefin and carbon dioxide using microwaves of the present invention is a material composed of a large number of carbon fiber ends gathered in a disordered manner, wherein plasma can be generated between the carbon fiber ends under microwave irradiation. The present invention obtains a carbon fiber aggregate by controlling the number of carbon fiber ends contained in each gram of the carbon fiber aggregate. Although the carbon fiber aggregate is pure carbon fiber, it can generate plasma and a high temperature of more than 1000°C under microwave irradiation. The problem of large brittleness and easy damage of porous composite materials in the prior art is overcome. In addition, the carbon fiber aggregate of the present invention has simple raw materials, is easy to prepare, and has extremely high promotion and application value.

[0063] The present invention adopts a carbon fiber aggregate that is not easily damaged and can generate plasma in a microwave field containing a carbon dioxide atmosphere, that is, it can reduce the coke and tar produced by polyolefin cracking, improve the utilization rate of polyolefin microwave cracking, and recycle carbon dioxide at the same time, thereby achieving efficient recycling of carbon dioxide and polyolefin at the same time, and has a wide application market. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Figure 1 This is a morphological photograph of the carbon fiber aggregate in Example 1 of the present invention, wherein the carbon fiber basic unit is a carbon fiber bundle prepared from carbon fiber bundle filaments. DETAILED DESCRIPTION

[0065] The present invention is described in detail below in conjunction with specific embodiments. It is necessary to point out that the following embodiments are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made to the present invention by those skilled in the art based on the contents of the present invention still fall within the scope of protection of the present invention.

[0066] The experimental data in the examples were measured using the following instruments and measurement methods:

[0067] In the embodiment, the collected synthesis gas components are subjected to chromatographic analysis in the following manner:

[0068] The gas products collected after cracking were analyzed according to the ASTM D1945-14 method using a refinery gas analyzer (HPAgilent 7890A, equipped with 3 channels, including 1 FID and 2 TCDs (thermal conductivity detectors)). Hydrocarbons were analyzed on the FID channel. A TCD using a nitrogen carrier gas was used to determine the hydrogen content because there was a small difference in the conductivity of hydrogen and helium carrier gases. Another TCD using helium as a carrier gas was used to detect CO, CO2, N2, and O2. In order to perform quantitative analysis, the response factor was determined by using an RGA (refinery gas analysis) calibration gas standard.

[0069] In the embodiment, the carbon-based solid matter residual rate after polyolefin cracking is X c The content is analyzed by weighing method:

[0070] The mass of the polyolefin after drying is weighed as M1, and the mass of the solid matter remaining after the polyolefin is cracked is weighed as M2.

[0071] Residual rate of carbon-based solid matter after polyolefin cracking X c =M2 / M1×100%

[0072] The raw materials of the embodiments of the invention are all commercially available.

[0073] The number of carbon fiber ends contained in each gram of the carbon fiber aggregate is obtained by theoretical calculation, and the specific calculation method is:

[0074] (1) When the carbon fiber basic unit of the carbon fiber aggregate is a single carbon fiber, the number of carbon fiber ends contained in each gram of the carbon fiber aggregate corresponds to the following formula:

[0075]

[0076] N is the number of carbon fiber ends contained in each gram of the carbon fiber aggregate (unit: pieces / g), and ρ is the carbon fiber density (unit: g / cm 3 ), d is the carbon fiber diameter (unit: μm), and L is the carbon fiber filament length (unit: mm).

[0077] (2) When the carbon fiber basic unit of the carbon fiber aggregate is a carbon fiber bundle prepared from carbon fiber bundles having one or more knotting points, the number of carbon fiber ends contained in each gram of the carbon fiber aggregate is calculated as follows:

[0078] N=[(n-1)×2×t+2]×k / m

[0079] N is the number of carbon fiber ends contained in each gram of the carbon fiber aggregate (unit: pieces / g), n is the number of knotting points on the carbon fiber bundle; t is the proportion of long carbon fiber bundles cut between the knotting points, k is the number of carbon fiber roots in the carbon fiber bundle, and m is the total mass of the carbon fiber bundle (unit: g).

[0080] Take the calculation method described in Example 1 as an example. A 5000mm long T300 carbon fiber 12K bundle is tied with itself at a knotting interval of 10mm (single knot), and 499 knots can be tied. Cutting the carbon fiber at the middle position of the two ends of the knotting point by two-thirds can produce [(499-1)×2×2 / 3+2)]×12000=7992000 carbon fiber ends. The knotting point formed by the single knot is a ring without an end. The mass of the 5000mm long T300 carbon fiber 12K bundle is 3.96g. Therefore, the number of carbon fiber ends contained in each gram of the carbon fiber aggregate described in Example 1 is 7992000÷3.96g≈2×10 6 Pieces / g.

[0081] (3) For a carbon fiber aggregate prepared from carbon fiber bundles having one or more fixed nodes and / or bundled nodes, the number of carbon fiber ends contained in each gram of the carbon fiber aggregate is calculated as follows:

[0082] N=[(n-1)×2×t×k+2k+c1×n1×k1)] / m

[0083] N is the number of carbon fiber ends contained in each gram of the carbon fiber aggregate (unit: pieces / g), n is the total number of fixed nodes formed by knotting and bundling on the carbon fiber bundle; t is the proportion of the long carbon fiber bundle cut at the fixed node, and k is the number of carbon fibers in the long carbon fiber bundle;

[0084] c1 is the number of ends of each bundle of each fixed node when the fixed node is a bundling node; n1 is the number of bundling nodes; k1 is the number of carbon fiber strands contained in the bundle of the bundling node.

[0085] m is the total mass of the carbon fiber bundle (unit: g).

[0086] (4) When the carbon fiber basic unit of the carbon fiber aggregate includes both a single carbon fiber and a carbon fiber bundle, the number of carbon fiber ends contained in each gram of the carbon fiber aggregate is calculated as follows:

[0087]

[0088] N is the number of carbon fiber ends contained in each gram of the carbon fiber aggregate (unit: pieces / g), n is the total number of fixed nodes formed by knotting and bundling on the carbon fiber bundles in the part of the carbon fiber aggregate constructed with carbon fiber bundles as the basic unit; t is the proportion of the long carbon fiber bundles cut at the fixed node in the part of the carbon fiber aggregate constructed with carbon fiber bundles as the basic unit, k is the number of carbon fibers in the long carbon fiber bundles in the part of the carbon fiber aggregate constructed with carbon fiber bundles as the basic unit; c1 is the number of ends of each bundle of each fixed node in the part of the carbon fiber aggregate constructed with carbon fiber bundles as the basic unit when the fixed node is a bundling node; n1 is the number of bundling nodes in the part of the carbon fiber aggregate constructed with carbon fiber bundles as the basic unit; k1 is the number of carbon fibers containing carbon fiber bundles in the bundle of the bundling node in the part of the carbon fiber aggregate constructed with carbon fiber bundles as the basic unit; ρ is the carbon fiber density in the part of the carbon fiber aggregate constructed with a single carbon fiber as the basic unit (unit: g / cm 3 ), d is the diameter of the carbon fiber in the part constructed with a single carbon fiber as the basic unit in the carbon fiber aggregate (unit: μm), L is the length of the carbon fiber filament in the part constructed with a single carbon fiber as the basic unit in the carbon fiber aggregate (unit: mm); m1 is the total mass of the part constructed with carbon fiber bundles as the basic unit in the carbon fiber aggregate (unit: g), and m2 is the total mass of the part constructed with a single carbon fiber as the basic unit in the carbon fiber aggregate (unit: g).

[0089] Take the calculation method described in Example 5 as an example. A 2500mm long T300 carbon fiber 12K bundle is knotted by itself with a knotting spacing of 10mm (single knot), and 249 knots can be tied. Cutting two-thirds of the carbon fiber bundle at a distance of 5mm between the knotting points can produce [(249-1)×2×2 / 3+2)]×12000=3992000 carbon fiber ends. The knotting point formed by the single knot is a ring without an end. The mass of the 2500mm long T300 carbon fiber 12K bundle is 1.98g; the length is 5mm, the diameter is 7μm, and the density is 1.8g / cm 3 , the mass of a single T700 carbon fiber is 3 g, so the number of carbon fiber ends contained in each gram of the carbon fiber aggregate described in Example 5 is.

[0090]

[0091] Temperature detection method: After the microwave irradiation is completed, a metal thermocouple is immediately inserted into the reaction container and brought into contact with the carbon fiber aggregate to measure the temperature.

[0092] Preparation of carbon fiber aggregate:

[0093] Example 1

[0094] Take a 5000mm long T300 carbon fiber 12K bundle (3.96g, Weihai Guangwei Composite Materials Group Co., Ltd.), use a single knotting method, according to the knotting spacing of 10mm, to tie 499 knots. Cut two-thirds of the carbon fiber bundle at 5mm between the knotting points to make a carbon fiber aggregate. The material is rolled up and placed in a quartz jar. The number of carbon fiber ends contained in each gram of carbon fiber aggregate is about 2×10 6 At this time, the material can generate plasma and an equilibrium temperature of 1200°C under pure carbon dioxide atmosphere by 900W microwave irradiation.

[0095] Comparative Example 1

[0096] Take a 5000mm long T300 carbon fiber 12K bundle (3.96g, Weihai Guangwei Composite Materials Group Co., Ltd.), use a single knotting method, according to the knotting spacing of 250mm, to tie 19 knots. Cut two-thirds of the carbon fiber bundle at 125mm between the knotting points to make a carbon fiber aggregate, roll it up and put it in a quartz jar. The number of carbon fiber ends contained in each gram of carbon fiber aggregate is about 7.9×10 4 At this time, the material was irradiated with 900W microwaves in a pure carbon dioxide atmosphere, and the material equilibrium temperature could only reach 300°C.

[0097] Example 2

[0098] Take 4g of a single T300 carbon fiber (short carbon fiber, density 1.76g / cm) with a length of 3mm and a diameter of 7μm. 3 , Weihai Guangwei Composite Materials Group Co., Ltd.), randomly stacked in a quartz jar, and the number of carbon fiber ends contained in each gram of carbon fiber aggregate is about 9.8×10 6 At this time, the material can generate plasma and an equilibrium temperature of 1400°C under pure carbon dioxide atmosphere by 1200W microwave irradiation.

[0099] Comparative Example 2

[0100] Take 4g of a single T300 carbon fiber (short carbon fiber, density 1.76g / cm) with a length of 60mm and a diameter of 7μm. 3 , Weihai Guangwei Composite Materials Group Co., Ltd.), randomly stacked in a quartz jar, and the number of carbon fiber ends per gram of carbon fiber aggregate is about 4.9×10 5 At this time, the material was irradiated with 1200W microwaves in a pure carbon dioxide atmosphere, and the material temperature could only reach an equilibrium temperature of 600°C.

[0101] Example 3

[0102] Take a 5600mm long T700 carbon fiber 12K bundle (4.48g, diameter 7μm, Weihai Guangwei Composite Materials Group Co., Ltd.), use a single knotting method, according to the knotting spacing of 14mm, to tie 399 knots. Cut two-thirds of the carbon fiber bundle at 7mm from the middle of the knotting point to make a carbon fiber aggregate. The material is rolled up and placed in a quartz jar. The number of carbon fiber ends contained in each gram of carbon fiber aggregate is about 1.4×10 6 At this time, the material can generate plasma and an equilibrium temperature of 1100°C by 700W microwave irradiation in a mixed gas atmosphere of carbon dioxide and water vapor with a volume ratio of 90:10.

[0103] Comparative Example 3

[0104] Take a 5000mm long T700 carbon fiber 12K bundle (4.0g, Weihai Guangwei Composite Materials Group Co., Ltd.), use a single knotting method, according to the knotting spacing of 250mm, and tie 19 knots. Cut two-thirds of the carbon fiber bundle at 125mm between the knotting points to make a carbon fiber aggregate, roll it up and put it in a quartz jar. The number of carbon fiber ends contained in each gram of carbon fiber aggregate is about 7.8×10 4 At this time, the material was irradiated with 700W microwave in a mixed gas atmosphere of carbon dioxide and water vapor with a volume ratio of 90:10, and the material equilibrium temperature could only reach 100°C.

[0105] Example 4

[0106] Take 6g of T700 single carbon fiber (short carbon fiber, density 1.8g / cm 3 , Weihai Guangwei Composite Materials Group Co., Ltd.), randomly stacked in a quartz jar, and the number of carbon fiber ends per gram of carbon fiber aggregate is about 5.8×10 6 At this time, the material can generate plasma and an equilibrium temperature of 1050°C by 1200W microwave irradiation in a mixed gas atmosphere of carbon dioxide and water vapor with a volume ratio of 30:70.

[0107] Comparative Example 4

[0108] Take 6g of T700 single carbon fiber (short carbon fiber, density 1.8g / cm 3 , Weihai Guangwei Composite Materials Group Co., Ltd.), randomly stacked in a quartz jar, and the number of carbon fiber ends contained in each gram of carbon fiber aggregate is about 8.3×10 5At this time, the material was irradiated with 1200W microwave in a mixed gas atmosphere with a volume ratio of carbon dioxide and water vapor of 30:70, and the equilibrium temperature of the material could only reach 900℃.

[0109] Example 5

[0110] Take a 2500mm long T300 carbon fiber 12K bundle (1.98g, Weihai Guangwei Composite Materials Group Co., Ltd.), use a single knotting method, according to the knotting spacing of 10mm, to tie 249 knots. Cut two-thirds of the carbon fiber bundle at 5mm between the knotting points; take 3g of a single T700 carbon fiber (short carbon fiber, density 1.8g / cm 3 , Weihai Guangwei Composite Materials Group Co., Ltd.), mixed with knotted carbon fiber bundles to form carbon fiber aggregates, which were randomly stacked in a quartz tank. The number of carbon fiber ends per gram of carbon fiber aggregate per unit mass was about 4.3×10 6 At this time, the material can generate plasma and an equilibrium temperature of 1280°C under pure carbon dioxide atmosphere by 900W microwave irradiation.

[0111] The carbon fiber aggregates prepared in Examples 1-5 have a number of carbon fiber ends greater than 1×10 6 / g, sufficient plasma can be generated under microwave irradiation in pure carbon dioxide and mixed gas (carbon dioxide and water vapor) atmosphere, so that the material equilibrium temperature is greater than 1000°C. The carbon fiber aggregates prepared in Comparative Examples 1-4 have a carbon fiber end number per gram of carbon fiber aggregate less than 1×10 6 / g, and sufficient plasma cannot be generated under microwave irradiation in the atmosphere of pure carbon dioxide and mixed gas (carbon dioxide and water vapor), so that the material equilibrium temperature is less than 900℃.

[0112] Simultaneous recycling of polyolefins and carbon dioxide using microwaves:

[0113] Example 6

[0114] Take polyethylene pellets, polypropylene flakes taken from discarded lunch boxes, poly-1-butene pellets, and ethylene-vinyl acetate copolymer taken from discarded shoe soles, and use a blast dryer to remove small molecules at 200°C for 5 hours. Take 2g of polyethylene pellets after small molecules are removed, polypropylene flakes taken from discarded lunch boxes, poly-1-butene pellets, and ethylene-vinyl acetate copolymer taken from discarded shoe soles, respectively, and place them on the surface of 4g of the carbon fiber aggregate obtained in Example 1, and then put the polyolefin and carbon fiber aggregate into a quartz jar. In a pure carbon dioxide atmosphere, use an industrial microwave oven to irradiate with microwaves at a microwave power of 700W for 10 minutes. All materials are gasified and cracked after microwave irradiation, leaving only a small amount of black residue, and weigh to measure the residual rate of carbon-based solid matter X c , as shown in Table 1, and the composition of the obtained gas phase product is shown in Table 2.

[0115] Example 7

[0116] Take polyethylene pellets, polypropylene flakes taken from discarded lunch boxes, poly-1-butene pellets, and ethylene-vinyl acetate copolymer taken from discarded shoe soles, and use an industrial microwave oven at 350W power for 30 minutes under air purge to remove small molecules. Take 64g of polyethylene pellets after small molecules are removed, polypropylene flakes taken from discarded lunch boxes, poly-1-butene pellets, and ethylene-vinyl acetate copolymer taken from discarded shoe soles, respectively, and mix them with 32g of carbon fiber aggregates obtained in Example 1, and then put the polyolefin and carbon fiber aggregates into a quartz jar. In a mixed gas atmosphere with a volume ratio of carbon dioxide to water vapor of 80:20, use an industrial microwave oven to irradiate with microwaves at a microwave power of 2000W for 10 minutes. All materials are gasified and cracked after microwave irradiation, leaving only a small amount of black residue. The residual rate of carbon-based solid matter X is measured by weighing. c , as shown in Table 1, and the composition of the obtained gas phase product is shown in Table 2.

[0117] Comparative Example 5

[0118] 4 g of the carbon fiber aggregate obtained in Example 1 used in Example 6 was replaced with 4 g of silicon carbide powder. Other conditions were the same as those in Example 6. The microwave irradiation cracking product contained a large amount of black residue. The residual carbon-based solid matter rate X was measured by weighing. c , as shown in Table 1.

[0119] Comparative Example 6

[0120] The gas environment of microwave irradiation used in Example 6 was replaced by pure nitrogen from pure carbon dioxide, and other conditions were the same as those in Example 6. The microwave irradiation cracking product contained a large amount of black residue, and the residual rate of carbon-based solid matter was measured by weighing. c , as shown in Table 1.

[0121] Comparative Example 7

[0122] 4 g of the carbon fiber aggregate obtained in Example 1 used in Example 6 was replaced by 4 g of the carbon fiber aggregate in Comparative Example 1. Other conditions were the same as those in Example 6. The microwave irradiation cracking product contained a large amount of black residue. The residual carbon-based solid matter rate X was measured by weighing. c , as shown in Table 1.

[0123] Table 1

[0124]

[0125] Table 2. Gas phase composition of cracking products

[0126]

[0127]

[0128] As shown in Table 1, the final carbon-based solid matter residual rate (X) of polyolefins subjected to microwave pyrolysis using carbon fiber aggregates in an atmosphere containing carbon dioxide gas is c ) are less than 3% (Example 6 and Example 7), while the X of polyolefins cracked by microwave using traditional microwave heating materials c are greater than 15% (Comparative Example 5), and if only carbon fiber aggregates are used and microwave cracking of polyolefin is not performed in an atmosphere containing carbon dioxide, the final X c All are greater than 8% (Comparative Example 6). It can be seen that the use of carbon fiber aggregates in an atmosphere containing carbon dioxide gas to perform microwave cracking of polyolefins can achieve more complete polyolefin cracking than other polyolefin cracking methods. In addition, since the temperature of the carbon fiber aggregate obtained in Comparative Example 1 can only reach 300°C under carbon dioxide microwave irradiation, only a small amount of polyolefin decomposes in a short time at this temperature. It can be seen that the number of carbon fiber ends contained in each gram of carbon fiber aggregate must reach 1×10 6 / g or more to achieve the effect of cracking polyolefins.

[0129] As shown in Table 2, the main components of the gas produced by polyolefin cracking in Examples 6 and 7, except for the incompletely reacted carbon dioxide, are carbon monoxide, hydrogen, methane and ethylene, which can be used as chemical raw materials or energy fuels after separation. The same experiment as the above process was carried out on the samples obtained in Examples 2-5, and similar experimental phenomena and results were obtained.

[0130] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation to the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein, on the contrary, the present invention can be extended to all other methods and applications with the same functions.

[0131] All publications, patent applications, patents and other references mentioned in this specification are incorporated herein by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings conventionally understood by those skilled in the art. In the event of a conflict, the definition in this specification shall prevail.

[0132] When this specification uses the prefix "well-known to those skilled in the art", "prior art" or similar terms to introduce materials, substances, methods, steps, devices or components, etc., the objects introduced by the prefix cover those commonly used in the art when this application is filed, but also include those that are not commonly used at present but will become recognized in the art as being suitable for similar purposes.

[0133] The endpoints and any values ​​of the scope disclosed in the present application document are not limited to the precise scope or value, and these scopes or values ​​should be understood to include values ​​close to these scopes or values. For numerical ranges, between the endpoint values ​​of each scope, between the endpoint values ​​of each scope and a separate point value, and between separate point values, one or more new numerical ranges can be combined with each other, and these numerical ranges should be considered as specifically disclosed in this article. Hereinafter, in principle, each technical solution can be combined with each other to obtain a new technical solution, which should also be considered as specifically disclosed in this article.

[0134] In the context of the present specification, any matters or items not mentioned are directly applicable to those known in the art without any changes except those explicitly stated.

[0135] Moreover, any embodiment described in this document may be freely combined with one or more other embodiments described in this document, and the technical solutions or technical ideas formed thereby are deemed to be part of the original disclosure or original record of the present invention, and should not be regarded as new content that has not been disclosed or anticipated in this document, unless a person skilled in the art considers that the combination is obviously unreasonable.

Claims

1. A method for simultaneously recovering polyolefin and carbon dioxide using microwaves, comprising: The polyolefin is brought into contact with the carbon fiber aggregate, and microwaves are applied to the polyolefin and the carbon fiber aggregate in an atmosphere of a gas containing carbon dioxide, so that the polyolefin reacts with the carbon dioxide to convert into a gas product having carbon monoxide as a main component; The carbon fiber assembly comprises a plurality of randomly arranged carbon fiber basic units, wherein the carbon fiber basic unit is a single carbon fiber and / or a carbon fiber bundle formed by a plurality of carbon fibers; The two ends of each carbon fiber in the length direction are the carbon fiber ends, and the number of carbon fiber ends contained in each gram of the carbon fiber aggregate is 1×10 6 Pieces / g or more.

2. The method according to claim 1, characterized in that: The carbon fiber aggregate presents a two-dimensional or three-dimensional spatial structure; and / or, At least some of two or more adjacent carbon fiber base units are in contact with each other; and / or, Calculated by the number of carbon fiber ends, the number of carbon fiber ends contained in each gram of the carbon fiber aggregate is 1×10 6 ~6×10 8 / g, preferably 1×10 6 ~6×10 7 pcs / g, more preferably 1×10 6 ~2×10 7 Pieces / g.

3. The method according to claim 1, characterized in that: The carbon fiber bundle is a carbon fiber bundle filament fixed together; at least one fixed node is provided on the carbon fiber bundle filament; preferably, When there is only one fixed node on the carbon fiber bundle, the length of the carbon fiber bundle is 0.1 to 30 mm, preferably 1 to 20 mm, and more preferably 3 to 20 mm; When the carbon fiber bundle is provided with more than two fixed nodes, the spacing between adjacent fixed nodes is 1 to 50 mm, preferably 2 to 30 mm, more preferably 5 to 20 mm; and part of the carbon fiber bundle between adjacent fixed nodes is disconnected; and / or, The fixing includes bundling fixing and / or knotting fixing, and the fixing nodes include bundling nodes and / or knotting points. More preferably, the knotting fixing is that the carbon fiber bundles are fixed by knotting themselves; and / or the bundles of the bundling fixing are carbon fiber bundles.

4. The method according to claim 3, characterized in that: The carbon fiber bundles, the carbon fiber bundles for bundling, and the carbon fiber bundles for knotting are independently selected from at least one of the following types of carbon fiber bundles: T300, T700, T800, T1000, T1100, M40, M50, and M60; preferably selected from at least one of the following types of carbon fiber bundles: T300, T700, and T800; more preferably selected from at least one of the following types of carbon fiber bundles: T300 and T700.

5. The method according to claim 4, characterized in that: The number of carbon fibers contained in each bundle of carbon fiber filaments is 1K-48K, preferably 1K, 3K, 6K, 12K, 24K, 48K, and more preferably 12K, 24K.

6. The method according to claim 1, characterized in that: The carbon fiber basic unit is a carbon fiber bundle formed by multiple carbon fibers, or the carbon fiber basic unit contains both a single carbon fiber and a carbon fiber bundle, or the carbon fiber basic unit is a single carbon fiber; preferably, When the carbon fiber basic unit comprises both a single carbon fiber and a carbon fiber bundle, the content of the carbon fiber bundle in the carbon fiber aggregate is 0.1-99.9wt%, preferably 1-99wt%, based on the total mass of the carbon fiber aggregate being 100wt%; and / or The length of each single carbon fiber is 0.1-30 mm, preferably 1-20 mm, and more preferably 3-20 mm.

7. The method according to claim 1, characterized in that: The weight ratio of the polyolefin to the carbon fiber aggregate is (1:100) to (100:1), preferably (1:50) to (50:1), and more preferably (1:30) to (30:1).

8. The method according to claim 1, characterized in that: The gas containing carbon dioxide comprises pure carbon dioxide gas or a mixed gas containing carbon dioxide; preferably, The carbon dioxide-containing mixed gas is a mixed gas of carbon dioxide and an inert gas and / or water vapor; more preferably, the inert gas is at least one of nitrogen, argon and helium; and / or, The volume fraction of carbon dioxide in the carbon dioxide mixed gas is 5% to 99.9%, preferably 10% to 99.9%, and most preferably 20% to 99.9%.

9. The method according to claim 1, characterized in that: The power of the microwave is 1W to 100KW, preferably 200W to 50KW, most preferably 500W to 20KW; and / or, The microwave time is 0.1 to 200 min, preferably 0.5 to 150 min, most preferably 1 to 100 min; and / or, The temperature of the carbon fiber aggregate exceeds 1000° C., causing polyolefin to decompose.

10. The method according to claim 1, characterized in that: The contacting mode between the polyolefin and the carbon fiber aggregate includes: the polyolefin is placed on the carbon fiber aggregate, placed in the cavity formed by the carbon fiber aggregate, covered by the carbon fiber aggregate, and mixed with the carbon fiber aggregate, or a combination of one or more modes.

11. The method according to claim 1, characterized in that: The polyolefin is a polyolefin prepared by homopolymerization or copolymerization of at least one of ethylene, propylene, butene, α-olefin, cycloolefin, 4-methyl-1-pentene, acrylic acid monomers, and a mixture of the polyolefins; preferably, The polyolefin is at least one of polyethylene, polypropylene, poly-1-butene, ethylene-vinyl acetate copolymer, polyolefin elastomer, cycloolefin homopolymer / copolymer, poly-4-methyl-1-pentene, ethylene-vinyl alcohol copolymer, and ethylene-acrylic acid copolymer.

12. The method according to claim 1, characterized in that The specific steps include: a. Removing small molecules from polyolefins; b. placing the treated polyolefin and carbon fiber assembly in a sealable reaction container, wherein the reaction container is made of a microwave transparent material; c. introducing a gas containing carbon dioxide into the reaction vessel to replace the air; d. Start the microwave, place the reaction container under the microwave field to react, and collect the gas products generated by the reaction.

13. Use of the method for simultaneously recovering polyolefin and carbon dioxide using microwaves according to any one of claims 1 to 12 in polyolefin recovery.

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