Method for preparing aromatic hydrocarbons by means of coupling conversion of co and polyolefin

Abstract

Provided is a method for preparing aromatic hydrocarbons by means of coupling conversion of carbon monoxide and a polyolefin, belonging to the technical field of polyolefin plastic conversion and recycling. The method uses carbon monoxide and polyolefin type plastic as reaction raw materials, uses as a catalyst a bifunctional catalyst consisting of metal, a metal oxide and a molecular sieve, and comprises performing a conversion reaction under the action of the catalyst. Because carbon monoxide may come from carbon resources such as coal, biomass and natural gas, the reaction process not only achieves optimized utilization of carbon resources, but also converts polyolefin waste plastic into valuable resources, achieving high-value utilization and producing aromatic hydrocarbon products having high added value. The reaction has a very high product yield and product selectivity, the yield of the aromatic hydrocarbons can reach 50%-80%, the proportion of benzene, toluene and xylene in the aromatic hydrocarbons is greater than 60%, and the catalyst can be repeatedly used after simple regeneration treatment. The present application is a new technology for comprehensive utilization of polyolefin type waste plastic and carbon monoxide utilization, and has a good application prospect.

Description

A method for preparing aromatic hydrocarbons by coupling conversion of CO and polyolefins Technical Field

[0001] The present invention relates to a method for preparing high-value aromatic hydrocarbon chemicals by coupling conversion of CO and polyolefins, and particularly relates to a catalyst and a method for preparing aromatic hydrocarbons by coupling conversion of CO and polyolefins. Background Art

[0002] Plastics are important organic synthetic polymer materials, widely used in a variety of fields, including packaging, agriculture, construction, and automotive. As of 2019, global plastic production reached 460 million tons per year, making it one of the largest synthetic materials by volume. Polyolefin plastics, represented by polyethylene and polypropylene, account for approximately 55% of total plastic production. However, due to their chemical inertness, a large amount of polyolefins are disposable and difficult to recycle. The resulting serious environmental pollution has attracted widespread attention from researchers.

[0003] For polyolefins, the C(sp 3 )-C(sp 3 ) bonds are very stable and difficult to break. Therefore, recycling polyolefins requires the introduction of additional energy to break the C-C bonds. However, traditional polyolefin recovery technologies, such as pyrolysis and hydrogenolysis, break C-C bonds randomly and irregularly, resulting in pyrolysis oils primarily composed of long-chain alkanes or alkenes. These products have a wide distillation range and relatively low added value, making it impossible to selectively produce high-value-added products. This has led to a lack of economically viable drivers for plastic pyrolysis.

[0004] Carbon monoxide (CO) is an unsaturated, metastable molecule, chemically stable with respect to decomposition. At room temperature, CO does not react with acids or bases, but it can form explosive mixtures when mixed with air. Exposure to open flames or high temperatures can cause combustion and explosion, making it a flammable and explosive gas. Because the carbon element in a CO molecule has a valence of +2, it can be oxidized to +4, making it reducing, and can also be reduced to a lower valence, making it oxidizing. As a major component of synthesis gas and various types of coal gas, CO is a crucial raw material for the synthesis of a wide range of basic organic chemical products and intermediates. Starting from CO, nearly all basic chemicals can be produced, including ammonia, phosgene, alcohols, acids, anhydrides, esters, aldehydes, ethers, amines, alkanes, and alkenes. Furthermore, the property of CO to react with transition metals to form metal carbonyls or metal carbonyl derivatives can be used to prepare various homogeneous catalysts required for organic chemical production. Furthermore, CO can be used as a terminator in polyethylene polymerization reactions. Although some studies have shown that high-value-added chemicals or liquid fuels (such as light olefins, aromatics, or higher alcohols) can be produced using CO and H2 under high temperature and pressure, the current acquisition of H2 resources is heavily dependent on the consumption of fossil energy (coal, oil, and natural gas). In the absence of significant "green hydrogen" acquisition technology, the large-scale use of H2 resources means more CO2 emissions, which is not conducive to the realization of the "dual carbon" goals. Therefore, in the absence of hydrogen, the resource utilization of CO is more attractive and more challenging.

[0005] Aromatic hydrocarbons, especially benzene, toluene, and xylene (BTX), are basic organic chemical raw materials with great demand. They are generally obtained by catalytic reforming and distillation of naphtha. Using waste polyolefins as raw materials, obtaining aromatic hydrocarbons under mild conditions by catalytic pyrolysis is an economically feasible technical route. Zhang et al. from the University of California, Santa Barbara used Pt / γ-Al2O3 catalyst to convert polyolefins into long-chain alkyl aromatic hydrocarbons at 280°C, with an aromatic yield of more than 70%. Although this method can achieve conversion at a relatively mild temperature of 280°C, there is almost no higher value-added benzene, toluene, and xylene in the product (Fan Zhang et al. Science 370 (2020) 437-441). There has been no report on the coupling conversion reaction of CO and polyolefins to produce high-value aromatic hydrocarbons at lower temperatures, such as below 300°C.

[0006] Summary of the Invention

[0007] To address the above problems, the present invention provides a catalyst and a method for producing aromatic hydrocarbons by coupling CO with polyolefins. To achieve the above objectives, the technical solution of the present invention is as follows:

[0008] The present invention provides a catalyst for the coupled conversion of carbon monoxide and polyolefins to prepare aromatic hydrocarbons. The catalyst is a bifunctional catalyst composed of a metal and a molecular sieve. Carbon monoxide and polyolefins are used as reaction raw materials. Under the action of the catalyst, a conversion reaction is carried out in a kettle reactor. The catalyst is a bifunctional catalyst, one of the functional components is composed of a metal, a metal oxide, or both, and the other functional component is composed of a molecular sieve. The metal and metal oxide components activate CO2, and the molecular sieve activates the polyolefin. The molecular sieve has an MFI, MEL, or MWW topological structure.

[0009] Based on the above technical solution, preferably, the metal or metal oxide contains one or more of the elements Fe, Co, Ni, Mn, Ce, Cu, Ru, Zn, Ga, Rh, Pd, Ir, and Pt; the mass fraction of the metal or metal oxide in the bifunctional catalyst is 0.1wt%-60wt%, preferably 0.5wt%-50wt%.

[0010] Based on the above technical solution, preferably, the metal or metal oxide can be directly supported on the molecular sieve, or can be dispersed on the metal oxide carrier and then physically mixed with the molecular sieve to form a bifunctional catalyst; the metal oxide carrier is Al2O3, TiO2, CeO2, ZnO, MoO x 、MnO x One or more of the following.

[0011] Based on the above technical solutions, preferably, the framework elements of the molecular sieves having MFI, MEL and MWW topological structures include at least one of Si-O, Si-O-Al, Si-O-Al-P, Si-O-Al-B and Si-O-Al-Ge; the molecular sieves having MFI, MEL and MWW topological structures are preferably at least one of MCM-22, ZSM-11 or ZSM-5.

[0012] Based on the above technical solutions, preferably, the molecular sieves having MFI, MEL and MWW topological structures contain medium-strong acid, and the amount of medium-strong acid sites is ≥0.1 mol / kg, more preferably ≥0.2 mol / kg, and more preferably ≥0.25 mol / kg.

[0013] The acid strength is defined by the NH3-TPD peak, including three types of acidity: weak acid, medium acid, and strong acid. The NH3-TPD is based on the desorption peak position of NH3. The position of the desorption peak refers to the thermal conductivity signal of desorbed NH3 recorded by TCD under standard test conditions, under the test conditions of sample mass w and carrier gas flow rate f (w / f) = 100g·h / L and a heating rate of 10°C / min, and a desorption curve is drawn. The inorganic solid is divided into three acid strengths according to the peak position of the curve. Weak acid refers to an acidic site with an NH3 desorption temperature of less than 245°C; medium acid refers to an acidic site with an NH3 desorption temperature of 275-500°C; and strong acid refers to an acidic site with an NH3 desorption temperature of greater than 500°C. The molecular sieve can be laboratory synthesized or commercially purchased and meet the requirements of the present invention.

[0014] Based on the above technical solutions, preferably, the metal or metal oxide is compounded with the molecular sieve by physical mixing or loading; preferably, the metal or metal oxide is compounded with the molecular sieve by impregnation, deposition precipitation, vapor deposition, or physical mixing.

[0015] Based on the above technical solution, preferably, the bifunctional catalyst needs to be pre-reduced, the reducing atmosphere is H2 or CO, the reduction temperature is 300°C-500°C, and the reduction time is 0.5h-10h.

[0016] Based on the above technical solution, the present invention also provides a method for preparing aromatic hydrocarbons by coupling conversion of carbon monoxide and polyolefins. Carbon monoxide and polyolefins are used as reaction raw materials, and the conversion reaction is carried out in a tank reactor using the catalyst provided in the above technical solution.

[0017] Based on the above technical solution, preferably, the polyolefin includes one or more of polyethylene, polypropylene, and polybutene, and plastic products made from the above polyolefins as raw materials or used waste plastics.

[0018] Based on the above technical solution, preferably, the carbon monoxide pressure is 0.2-6 MPa, preferably 0.5-3 MPa; the reaction temperature is 180-400°C, preferably 230-300°C; the mass ratio of catalyst to polyolefin is ≥1:500, preferably ≥1:100;

[0019] Based on the above technical solution, preferably, when the reaction is carried out in a tank reactor, the residence time of the reactants is 0.5-20 h, preferably 1-10 h, and more preferably 2-10 h.

[0020] Based on the above technical solution, preferably, when the reaction is carried out in a moving bed reactor, the gas space velocity of the reaction is 20-2000 mL·g -1 ·h -1, preferably 20-1000mL·g -1 ·h -1 , more preferably 80-1000 mL·g -1 ·h -1 .

[0021] The beneficial effects of the present invention are:

[0022] 1. The technical solution of this invention differs from traditional plastic pyrolysis technology by utilizing a composite catalyst to achieve a one-step, highly selective conversion of CO and polyolefins into high-value-added aromatics such as benzene, toluene, and xylene. The addition of CO not only serves as a feedstock for aromatics production but also reacts with H species generated by hydrogen transfer during aromatization, inhibiting the formation of alkanes and improving the selectivity of aromatic components.

[0023] 2. Unlike the high-temperature pyrolysis mechanism of polyolefins, at low temperatures (reaction temperatures below 300°C), polyolefins cannot produce aromatics through the dehydrogenation aromatization process (Equation 1) and can only produce aromatics through hydrogen transfer aromatization (Equation 2). Therefore, the yield of aromatics at low temperatures is limited by the reaction mechanism and cannot exceed 50%.

[0024] The present invention utilizes hydrogen overflow between catalyst components and CO to consume hydrogen overflowed from molecular sieve hydrogen transfer aromatization, thereby preventing the generation of alkanes. This breaks the original reaction equilibrium and achieves highly selective preparation of high-value-added aromatic products under relatively mild reaction conditions (reaction temperature below 300°C), thus having strong economic application prospects.

[0025] 3. The present invention uses polyolefin as raw material. The polyolefin can also be polyolefin or plastic products made from polyolefin as raw material, such as plastic bags, plastic barrels, plastic wrap, various films, waste food packaging, etc. Its raw material sources are wide and the raw material utilization rate is high. It is an effective and scalable polyolefin utilization solution.

[0026] 4. The present invention can be applied not only to the resource utilization of CO waste gas in the production processes of coking and ironmaking in the oil refining and metallurgical industries, but also to the utilization of waste gas containing high concentration of CO in the production processes of synthetic ammonia and methanol in the chemical industry, and even the waste gas of CO and CO2 at the same time. It has a wide source of raw materials and strong applicability, which can significantly promote the utilization of CO and reduce CO2 emissions.

[0027] 5. The catalyst of the present invention can be recycled after regeneration treatment by air roasting-hydrogen reduction, without obvious catalyst loss, which can significantly reduce the cost problem caused by catalyst deactivation.

[0028] 6. The preparation process of the nanocomposite catalyst of the present invention is simple and the conditions are mild. The reaction process can not only achieve high-value utilization of polyolefins and CO simultaneously, but also has high product space-time yield and selectivity. The yield of mixed aromatics can reach 50-80%, and the proportion of benzene, toluene and xylene in the aromatics is greater than 60%. Compared with the traditional polyolefin pyrolysis process under inert gas conditions, the aromatics yield is about twice as high. DETAILED DESCRIPTION

[0029] The present invention will be further described below by way of examples, but the scope of the claims of the present invention is not limited by these examples. Meanwhile, the examples only provide some conditions for achieving this purpose, but do not mean that these conditions must be met to achieve this purpose.

[0030] 1. Preparation of molecular sieves

[0031] The medium-strong acid described in the present invention can be tested by solid-state nuclear magnetic resonance (NMR) H spectroscopy, NH3-TPD, infrared spectroscopy, chemical titration, etc. However, the acidity test method is not limited to the above test methods.

[0032] The molecular sieves with MFI, MEL and MWW topological structures described in the present invention can be prepared by various methods and conditions. This patent takes the preparation by hydrothermal synthesis as an example.

[0033] 1) The molecular sieve with MFI topology can be prepared by referring to the following method:

[0034] The raw materials, including 30% silica sol (mass concentration), aluminum sulfate, sodium hydroxide, tetrapropylammonium hydroxide (R), and deionized water, were weighed in a mass ratio of SiO2:Al2O3:Na2O:R:H2O = 5:0.02:2:1.5:200. The mixture was stirred and aged at 30°C for 2 hours. After that, it was transferred to a hydrothermal reactor and crystallized at 180°C for 48 hours. The mixture was quickly cooled to room temperature in a water bath and repeatedly centrifuged and washed until the pH of the supernatant was 7 at the end of the washing. The precipitate was dried at 110°C for 17 hours and then calcined in air at 600°C for 3 hours to obtain a topological ZSM-5 molecular sieve, labeled as fraction 1.

[0035] 2) The molecular sieve having a MEL topology can be prepared by referring to the following method:

[0036] The raw materials, silica sol, aluminum isopropoxide, sodium hydroxide, TBAOH(R), and deionized water, were weighed in a mass ratio of SiO2:Al2O3:Na2O:R:H2O = 10:0.3:1:2:200. After stirring overnight at room temperature, the gel was placed in a 65°C oven, dried, crushed, and then placed in a crystallization kettle. A certain amount of deionized water was added and crystallized at 170°C for 3 days. The resulting product was filtered, washed, dried, and ammonium exchanged before being calcined in a muffle furnace at 600°C for 6 hours to produce a ZSM-11 molecular sieve with a MEL topology, labeled as fraction 2.

[0037] The framework element composition of the molecular sieve with MFI, MEL and MWW topological structures can also be at least one of Si-O, Si-Al-O, Si-Al-PO, Si-Al-BO and Si-Al-Ge-O.

[0038] Table 1 Preparation and performance parameters of molecular sieves with MFI, MEL and MWW topologies

[0039] 2. Preparation of bifunctional catalysts

[0040] The metal is combined with the molecular sieve to form a bifunctional catalyst by impregnation, deposition, vapor deposition, or physical mixing. Here, the bifunctional catalyst prepared by impregnation is taken as an example.

[0041] The impregnation process can be implemented by either equal volume impregnation or excess impregnation, as follows:

[0042] The metal source is dissolved in deionized water to prepare a precursor solution, which is then placed in the precursor solution and stirred thoroughly to uniformly disperse the precursor solution and the solute therein on the molecular sieve, followed by drying and calcination to obtain the desired metal oxide-modified molecular sieve.

[0043] If the equal volume impregnation method is used, the pore volume V of the molecular sieve needs to be determined in advance. p The volume of the precursor solution used is V0 = V p If the excess impregnation method is used, the V0 of the precursor solution used <V p .

[0044] The specific catalyst preparation and its parameter characteristics are shown in Table 2-3.

[0045] Table 2 Catalysts prepared by impregnation method and their parameter characteristics

[0046] 3. Catalytic Reaction Examples

[0047] The catalyst can be used in a tank reactor.

[0048] The reaction apparatus was equipped with a gas mass flowmeter to control the gas flow, and gas chromatography was used for quantitative analysis of the products.

[0049] The following describes a method using a tank reactor as an example: 2 g of the catalyst of the present invention and 40 g of a polyolefin are mixed in a tank reactor. The air in the reactor is replaced with CO, and CO gas (containing 5% Ar as an internal standard for chromatographic analysis) is introduced at a pressure of 0.2-6 MPa. The temperature is raised to 180°C-300°C, and the reaction is carried out. The product is quantitatively analyzed by chromatography.

[0050] The gaseous products were analyzed using Ar as an internal standard and the yields were calculated. The liquid products were collected and analyzed using n-undecane as an internal standard and the yields were calculated.

[0051] The reaction performance can be changed by changing the reaction temperature, reaction pressure, and the feed mass ratio of CO to polyolefin.

[0052] Performance is as follows: Total aromatics selectivity can reach 60-80%, with benzene, toluene, and xylene (BTX) accounting for more than 60% of the aromatics. The addition of CO not only serves as a feedstock for aromatics production but also reacts with hydrogen species generated by hydrogen transfer during aromatization, inhibiting the formation of alkanes and improving the selectivity of aromatic components.

[0053] Table 3 lists the specific applications of the catalyst and its effect data.

[0054] Table 3 Specific application of catalyst and its reaction effect data

[0055] The metal components and preparation method used in catalyst L used in comparative example 1 are consistent with those of catalyst A, and the molecular sieve component used is replaced by commercially available 5 molecular sieve from the catalyst factory of Nankai University, which has a three-dimensional octahedral pore channel.

[0056] The metal components and preparation method used in the catalyst M used in Comparative Example 2 are consistent with those of catalyst A, and the molecular sieve component used is replaced by the commercially available 6 molecular sieve from the Nankai University Catalyst Factory, which has a three-dimensional twelve-membered ring channel.

[0057] The metal components and preparation method used in catalyst N used in comparative example 3 are consistent with those of catalyst A, and the molecular sieve component used is replaced by the commercially available 7 molecular sieve from Nankai University Catalyst Factory, which has one-dimensional pores with coexisting octahedral rings and 12-membered rings.

[0058] The metal components and preparation method used in catalyst O used in comparative example 4 are consistent with those of catalyst A, and the molecular sieve component used is replaced by commercially available 8 molecular sieve from the catalyst factory of Nankai University, which has a one-dimensional ten-membered ring channel.

[0059] The reaction results of comparative examples 1-4 show that the molecular sieves of different topological structures are obviously modulated to product selectivity. The SAPO-34 of three-dimensional eight-membered ring pore structure is unfavorable for the conversion of polyolefins and the generation of aromatic products, is suitable for generating the product of short carbon chain hydrocarbons, but aromatics yield only has 4%. There is larger orifice in the USY molecular sieve with three-dimensional twelve-membered ring pore, causes very easily to produce heavier aromatics (such as naphthalene) and carbon deposition deactivation, therefore the yield of heavy aromatics and carbon deposition is higher, and heavy aromatics accounts for 68% of all aromatic products. There is the commercially available MOR molecular sieve of one-dimensional eight-membered ring and twelve-membered ring coexistence and the SAPO-11 molecular sieve with one-dimensional ten-membered ring pore, is unfavorable for aromatization process, product is mainly the gasoline product of cracking, and aromatics content is lower, and aromatics yield only has 21%.

[0060] Catalyst P, used in Comparative Example 5, uses the same metal components and preparation method as Catalyst A. The molecular sieve component is replaced with a 9-point molecular sieve, and the strong acid density is only 0.07 mmol / g. The reaction performance in Comparative Example 5 is extremely poor, likely due to the low acid density, which results in poor aromatization. Therefore, a certain medium-strong acid density is crucial.

[0061] The catalyst Q used in Comparative Example 6 is Pt directly impregnated on γ-Al2O3. As a result, CO is almost not converted, the polyolefin conversion rate is very low, and the yields of aromatics and BTX are also very low.

[0062] The molecular sieve component used in Catalyst R used in Comparative Example 7 is the same as that of Catalyst A (Part 1), except that it does not contain a metal Pt component. Since the molecular sieve has almost no catalytic activity for activating CO, only olefins react during the catalytic reaction. That is, olefins can be directly aromatized by the molecular sieve. However, the yield of aromatics is not high (38%), and long-chain alkanes are mainly produced. The CO conversion rate is only 0.02 g·g (聚烯烃) ·h -1 , which is very low and cannot achieve high selectivity in the preparation of aromatics and utilization of CO.

[0063] Comparative Examples 6 and 7 show that when only one functional component, metal oxide or molecular sieve, is present, the reaction effect is poor and the excellent reaction performance described in the present invention is completely lacking.

[0064] The catalyst used in Comparative Example 8 and the catalyst used in Example 1 are both Catalyst A, but no olefin is added in Comparative Example 8. Experiments show that without the addition of polyolefin, CO cannot be effectively converted.

[0065] The catalyst used in Comparative Example 9 is the same as the catalyst used in Example 1, which is Catalyst A. However, in Comparative Example 9, no CO is added and N2 is used as the pressurized atmosphere. Experiments show that without the introduction of CO, polyolefins can be converted into aromatic hydrocarbons by a bifunctional catalyst composed of metal and molecular sieve. The reaction results are similar to those in Comparative Example 7, and the yield of aromatic hydrocarbons is low, only 36%, and does not have the excellent reaction performance described in the present invention.

[0066] From the reaction results of Comparative Examples 8-9, it can be seen that the CO conversion and polyolefin conversion reactions are mutually coupled and mutually beneficial. In the absence of polyolefin, CO cannot be effectively converted; in the absence of CO, polyolefin cannot be highly selectively converted to aromatics, and the amount of alkane by-products increases.

[0067] The catalysts used in Comparative Example 10 are consistent with Catalyst A used in Example 1, but the filling partial pressure of CO in Comparative Example 10 is lower. At this time, the amount of CO is insufficient, and its effect on promoting the selective formation of aromatics is small. Therefore, it is very important to ensure a sufficient amount of CO to promote the catalytic reaction.

[0068] It can be seen from the above table that the topological structure of the molecular sieve, the acid properties, the feed ratio of CO to polyolefin waste plastics, and the matching between the metal or metal oxide and the molecular sieve all play a crucial role, directly affecting the selectivity of mixed aromatics, the conversion rate of CO, and the content of benzene, toluene, and xylene in aromatics.

Claims

1. A method for preparing aromatic hydrocarbons by coupling conversion of carbon monoxide and polyolefins, characterized in that: Carbon monoxide and polyolefin plastics are used as reaction raw materials, and the catalyst used is a bifunctional catalyst, one of the functional components is composed of metal, metal oxide or both, and the other functional component is composed of molecular sieve; The molecular sieve is a molecular sieve having MFI, MEL and MWW topological structures; The metal elements in the metal or metal oxide include one or two or more of Fe, Co, Ni, Mn, Ce, Cu, Ru, Zn, Ga, Rh, Pd, Ir, and Pt.

2. The method according to claim 1, characterized in that: The carbon monoxide pressure is 0.2-6MPa, the reaction temperature is 180-400°C, and the mass ratio of the catalyst to the polyolefin is ≥1:

500.

3. The method according to claim 1, characterized in that: The mass fraction of the metal or metal oxide in the bifunctional catalyst is 0.1wt%-60wt%; the metal or metal oxide can be directly supported on the molecular sieve, or can be dispersed on the metal oxide carrier and then physically mixed with the molecular sieve to form a bifunctional catalyst; the metal oxide carrier is Al2O3, TiO2, ZrO2, CeO2, ZnO, MoO x 、MnO x One or two or more of the following.

4. The method according to claim 1, characterized in that: The framework elements of the molecular sieves having MFI, MEL and MWW topological structures include at least one of Si-O, Si-O-Al, Si-O-Al-P, Si-O-Al-B and Si-O-Al-Ge; the molecular sieves having MFI, MEL and MWW topological structures are preferably at least one of MCM-22, ZSM-11 or ZSM-5.

5. The method according to claim 1, characterized in that: The molecular sieves with MFI, MEL and MWW topological structures contain medium-strong acid, and the amount of medium-strong acid sites is ≥0.1 mol / kg.

6. The method according to claim 1, characterized in that: The composite method of the metal or metal oxide and the molecular sieve is physical mixing or loading; the loading is to load the metal or metal oxide on the molecular sieve by impregnation, deposition precipitation, or vapor deposition.

7. The method according to claim 1, characterized in that: The metal and metal oxide components in the catalyst play a role in activating CO; the molecular sieve plays a role in activating polyolefin.

8. The method according to claim 1, characterized in that: The bifunctional catalyst needs to be pre-reduced, the reducing atmosphere is H2 or CO, the reducing temperature is 300°C-500°C, and the reducing time is 0.5h-10h.

9. The method according to claim 2, characterized in that: When the reaction is carried out in a tank reactor, the residence time of the reactants is 0.5-20h; when the reaction is carried out in a moving bed reactor, the gas space velocity of the reaction is 20-2000mL·g -1 ·h -1 .

10. The method according to claim 1, characterized in that: The polyolefin includes one or more of polyethylene, polypropylene and polybutene, and plastic products made from the above polyolefins as raw materials or waste plastics after use.

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