Method for producing aromatic hydrocarbons by co-conversion of co and polyolefin

Abstract

FIELD: chemical recycling.SUBSTANCE: method for producing aromatic hydrocarbons by the joint conversion of carbon monoxide and polyolefin, relating to the technical field of conversion and processing of polyolefin plastic. The method is carried out in the presence of a bifunctional catalyst, wherein one functional component is selected from a metal, a metal oxide and a mixture thereof, and the other functional component is a zeolite. The zeolite has a topological structure of MFI, MEL or MWW and contains medium strength acidic sites in an amount greater than or equal to 0.1 mol / kg, and the metal / metal oxide comprises one or more elements selected from Fe, Co, Ni, Mn, Ce, Cu, Ru, Zn, Ga, Rh, Pd, Ir and Pt. The pressure of carbon monoxide is 0.2–6 MPa, the reaction temperature is 180–400 °C, and the mass ratio of the catalyst to the polyolefin is greater than or equal to 1:500.EFFECT: high yield and selectivity of products.8 cl, 3 tbl, 26 ex

Description

[0001] FIELD OF TECHNOLOGY

[0002] The present invention relates to the technical field of producing high-value aromatic chemical products by co-converting CO and a polyolefin, in particular to a method for producing an aromatic hydrocarbon by co-converting CO and a polyolefin.

[0003] STATE OF THE ART

[0004] Plastics are important organic synthetic polymer materials commonly used in packaging, agriculture, construction, automotive manufacturing, and other fields. By 2019, global plastic production reached 460 million tons per year, making it one of the most widely produced synthetic materials. This includes polyolefin plastics, such as polyethylene and polypropylene, which account for approximately 55% of total plastic production. However, due to the chemical inertness of polyolefin, a significant portion of disposable polyolefin-based products are difficult to recycle, leading to serious environmental pollution and attracting extensive research attention.

[0005] For C(sp) bond polyolefin 3 )-C(sp 3) in their backbones are very stable and resistant to cleavage. Therefore, polyolefin processing requires additional energy to cleave these C-C bonds. However, traditional polyolefin processing methods, such as pyrolysis and hydrogenolysis, result in random and non-selective cleavage of C-C bonds, resulting in pyrolysis oils dominated by long-chain alkanes or olefins with a wide boiling range and relatively low added value. These methods do not produce high-added-value products with high selectivity, making plastic pyrolysis economically unviable due to the lack of an acceptable driving force.

[0006] Carbon monoxide (CO) molecules are unsaturated and metastable and are chemically stable with respect to decomposition. At room temperature, CO does not react with acids or bases, but can form explosive mixtures when mixed with air. It is highly flammable and explosive when exposed to an open flame or high temperatures. The carbon atom in CO molecules has an oxidation state of +2, which allows it to be oxidized to the oxidation state of +4 (exhibiting reducing properties) or reduced to lower oxidation states (exhibiting oxidizing properties). As the main component of syngas and various types of coal gas, CO is an essential raw material for the synthesis of a wide range of basic organic chemical products and intermediates.Starting from CO, almost all basic chemical products can be obtained, including ammonia, phosgene, alcohols, acids, anhydrides, esters, aldehydes, ethers, amines, alkanes, and alkenes. Furthermore, CO can react with transition metals to form metal carbonyls or their derivatives, which can be used as homogeneous catalysts in the production of organic chemicals. Furthermore, CO can also be used as a capping agent in polyethylene polymerization reactions. Although some studies have shown that high-value chemicals or liquid fuels (e.g., lower olefins, aromatic compounds, or higher alcohols) can be produced from CO and H2 under high temperature and pressure, H2 production currently relies heavily on fossil fuels (coal, oil, and natural gas).Without significant green hydrogen production technologies, the active use of H2 resources implies increased CO2 emissions, which negatively impacts the achievement of carbon peaking and carbon neutrality goals. Therefore, the use of CO2 without H2 is a more attractive and challenging task.

[0007] Aromatic compounds, especially benzene, toluene, and xylene (BTX), are in-demand basic organic chemical raw materials, typically produced from naphtha through catalytic reforming and distillation. Using polyolefin waste as raw materials to produce aromatic compounds through mild catalytic pyrolysis is a cost-effective technical route. Scientists such as Zhang et al. from the University of California, Santa Barbara used a Pt / γ-Al2O3 catalyst to convert polyolefin to long-chain alkyl aromatic compounds at 280°C, achieving aromatic yields exceeding 70%. Although this method allows for conversion at a relatively moderate temperature (280 °C), the products contain virtually no high-quality benzene, toluene, or xylene (Fan Zhang et al., Science, 370 (2020), pp. 437–441).The co-conversion reaction of CO and polyolefin to produce high-value aromatic compounds at lower temperatures, such as below 300 °C, has not been reported.

[0008] SUMMARY OF THE INVENTION

[0009] In view of the above problems, the present invention provides a method for producing aromatic hydrocarbons by co-converting CO and a polyolefin, comprising:

[0010] using carbon monoxide and a polyolefin as reaction raw materials and using a bifunctional catalyst, wherein one functional component is selected from a metal, a metal oxide, and a mixture thereof, and the other functional component is a zeolite;

[0011] at the same time

[0012] The zeolite has a topological structure of MFI, MEL or MWW and contains medium-strength acid sites in an amount greater than or equal to 0.1 mol / kg;

[0013] the metal / metal oxide comprises one or more elements selected from Fe, Co, Ni, Mn, Ce, Cu, Ru, Zn, Ga, Rh, Pd, Ir and Pt; and

[0014] wherein the carbon monoxide pressure is 0.2-6 MPa, the reaction temperature is 180-400 °C, and the mass ratio of the catalyst to the polyolefin is greater than or equal to 1:500.

[0015] In one embodiment, the weight fraction of the metal or metal oxide in the bifunctional catalyst is from 0.1 wt.% to 60 wt.%, wherein the metal or metal oxide is either directly loaded onto the zeolite or distributed on a metal oxide support and then physically mixed with the zeolite to form the bifunctional catalyst, wherein the metal oxide support is selected from Al2O3, TiO2, ZrO2, CeO2, ZnO, MoO x , MnO x and their mixtures.

[0016] In another embodiment, the zeolite with the topological structure of MFI, MEL or MWW has a framework comprising at least one of Si-O, Si-O-Al, Si-O-Al-P, Si-O-Al-B and Si-O-Al-Ge, and the zeolite with the topological structure of MFI, MEL or MWW is preferably at least one of MCM-22, ZSM-11 and ZSM-5.

[0017] In another embodiment, the metal or metal oxide and the zeolite are combined in a mechanical mixing or loading mode, wherein the loading mode is loading the metal or metal oxide onto the zeolite by impregnation, precipitation by precipitation, or vapor deposition.

[0018] In another embodiment, the metal / metal oxide component in the catalyst provides CO activation and the zeolite provides polyolefin activation.

[0019] In another embodiment, the bifunctional catalyst is pre-reduced in an H2 or CO atmosphere at 300-500 °C for 0.5-10 h.

[0020] In another embodiment, when the reaction is carried out in a tank-type reactor, the residence time of the reactants is 0.5 to 20 hours; when the reaction is carried out in a moving bed reactor, the gas hourly space velocity is 20 to 2000 ml g -1 ⋅h -1 .

[0021] In another embodiment, the polyolefin comprises at least one of polyethylene, polypropylene and polybutene, as well as plastic products made from them, or consumer plastic waste. The present invention has the following advantages.

[0022] 1. Unlike conventional plastic pyrolysis technologies, the present invention utilizes a composite catalyst to achieve a single-step combined use of CO and polyolefin for highly selective conversion to high-value aromatic compounds such as benzene, toluene, and xylene. The introduced CO not only serves as a raw material for the production of aromatic compounds but also reacts with hydrogen species generated during hydrogen transfer aromatization, suppressing the formation of alkanes and increasing the selectivity for aromatic components.

[0023] 2. Unlike the mechanisms of high-temperature pyrolysis of polyolefins, at low temperatures (reaction temperatures below 300°C), polyolefin cannot form aromatic compounds through aromatization by dehydrogenation (Equation 1), but only through aromatization with hydrogen transfer (Equation 2). Therefore, the yield of aromatic compounds at low temperatures is limited by this reaction mechanism and cannot exceed 50%.

[0024] (1)

[0025] (2)

[0026] The present invention utilizes hydrogen flow between catalyst components and utilizes CO to consume hydrogen flowing from hydrogen-transfer aromatization on a zeolite, preventing its conversion to alkanes. This disrupts the initial reaction equilibrium and enables highly selective production of value-added aromatic products under relatively mild reaction conditions (reaction temperatures below 300°C), demonstrating high economic potential for application.

[0027] 3. In the present invention, polyolefin is used as a raw material, which may also include plastic products made of polyolefin and polyolefin-based materials, such as plastic bags, plastic barrels, polyethylene film, various films, food packaging waste, etc. The raw materials for the method of the present invention are publicly available and exhibit a high recycling rate, making it an effective and scalable solution for recycling polyolefins. 4. The present invention is applicable not only to the utilization of CO emissions generated in processes such as petroleum refining, coking, and ironmaking in the metallurgical industry, but also to the utilization of high-concentration CO emissions generated in processes such as ammonia synthesis and methanol production in the chemical industry. It can even be applied to the utilization of emissions containing both CO and CO2. Due to the abundant raw material sources and good applicability, the present invention significantly promotes the utilization of CO while simultaneously reducing CO2 emissions.

[0029] 5. After regeneration by roasting in an air atmosphere followed by reduction in a hydrogen atmosphere, the catalyst according to the present invention can be recycled without significant loss of catalyst, which significantly reduces the costs associated with the loss of catalyst activity.

[0030] 6. The process for producing the nanocomposite catalyst in the present invention is simple and carried out under mild conditions. Furthermore, the reaction not only ensures high-value utilization of both polyolefin and CO but also demonstrates high yield per unit time per unit volume and selectivity. The yield of mixed aromatic compounds can reach 50–80%, with benzene, toluene, and xylene accounting for more than 60% of the aromatic products. Compared with traditional polyolefin pyrolysis under inert gas conditions, the yield of aromatic compounds is more than twice as high.

[0031] DETAILED DESCRIPTION OF PREFERRED IMPLEMENTATION OPTIONS

[0032] The following examples are provided to further illustrate the present invention, but the scope of the claims is not limited to these examples. At the same time, these examples only present some conditions for achieving the objectives, which does not mean that the conditions must be met to achieve the objectives.

[0033] 1. Obtaining zeolites

[0034] Ⅰ. Obtaining zeolites

[0035] The medium-strength acid sites described in the present invention can be characterized by a variety of methods, including, but not limited to, solid-state NMR (¹H NMR), NH3-TPD (temperature-programmed desorption), infrared spectroscopy (IR), and chemical titration.

[0036] The zeolite with the MFI, MEL, or MWW topological structure described in the present invention can be prepared by various methods and under various conditions. This patent provides an example of their preparation via hydrothermal synthesis.

[0037] 1) The process of obtaining zeolite with MFI topological structure may include the following method.

[0038] Raw materials including 30% (by weight) of silica sol, aluminum sulfate, sodium hydroxide, tetrapropylammonium hydroxide (R) and deionized water were weighed at an oxide weight ratio of SiO2:Al2O3:Na2O:R:H2O=5:0.02:2:1.5:200, and stirred and kept at 30 °C for 2 hours to obtain a product, then the product was transferred to a hydrothermal reactor for crystallization at 180 °C for 48 hours. The crystallized product was cooled to room temperature in a water bath and then centrifuged and washed repeatedly until the supernatant pH reached 7. The precipitate was dried at 110 °C for 17 hours and then calcined in air at 600 °C for 3 hours to obtain a ZSM-5 molecular sieve with a topological structure, designated as zeolite 1.

[0039] 2) The process of obtaining zeolite with MFI topological structure may include the following method.

[0040] The raw materials, including 30% (by weight) of silica sol, aluminum isopropylate, sodium hydroxide, tetrabutylammonium hydroxide (R), and deionized water, were weighed at a weight ratio of SiO2:Al2O3:Na2O:R:H2O=10:0.3:1:2:200 and stirred overnight at room temperature to obtain a product, and then the product was placed in an oven at 65 °C for drying. The dried product was crushed and placed in a hydrothermal reactor. A certain amount of deionized water was poured into the reactor for crystallization at 170 °C for 3 days. The crystallized product was vacuum filtered, washed, dried, and ammonium exchanged, then calcined in a muffle furnace at 600 °C for 6 hours to obtain a ZSM-11 molecular sieve with an MFI topological structure, designated as zeolite 2.

[0041] A zeolite with a topological structure of MEL, MFI or MWW has a framework containing at least one of Si-O, Si-Al-O, Si-Al-PO, Si-Al-BO, Si-Al-Ge-O.

[0042] Table 1. Parameters for obtaining and characteristics of zeolites with MFI, MEL or MWW topological structure

[0043] Sample number Zeolite type Source Topological structure Amount of medium strength acid (mol / kg) Pore ​​volume, Vp (cm3 / g) Zeolite 1 ZSM-5 Hydrothermal synthesis MFI 0,87 0,35 Zeolite 2 ZSM-11 Hydrothermal synthesis MEL 0,65 0,38 Zeolite 3 ZSM-5 Purchased from Nankai University MFI 0,68 0,31 Zeolite 4 MCM-22 Purchased from Nankai University MWW 0,43 0,36 Zeolite 5 SAPO-34 Purchased from Nankai University CHA 0,36 0,32 Zeolite 6 USY Purchased from Nankai University FAU 0,96 0,41 Zeolite 7 MOR Purchased from Nankai University MOR 0,73 0,35 Zeolite 8 SAPO-11 Purchased from Nankai University AEL 0,25 0,32 Zeolite 9 ZSM-5 Purchased from Nankai University MFI 0,07 0,29

[0044] Ⅱ. Preparation of bifunctional catalysts

[0045] A metal / metal oxide component is combined with a zeolite by methods such as impregnation, precipitation, vapor deposition, or physical mixing to form bifunctional catalysts. In this case, a bifunctional catalyst obtained by impregnation is considered as an example.

[0046] The impregnation method can be carried out using either incipient wetness impregnation or excess solution impregnation as described below.

[0047] The metal source is dissolved in deionized water to form a stock solution. The zeolite is impregnated in the stock solution and thoroughly mixed to ensure uniform distribution of the stock solution and its solutes on the zeolite. Drying and calcination then follow to produce the desired metal oxide-modified zeolite.

[0048] Pore volume V p The zeolite must be measured in advance, before impregnation. If incipient wetness impregnation is used, the volume of the initial solution used, V0, must be equal to V p If the excess solution impregnation method is used, the volume of the initial solution used V0 should be less than V p .

[0049] The parameters for obtaining catalysts are shown in Table 2.

[0050] Table 2. Catalysts obtained by impregnation method and characteristics of their parameters

[0051] Catalyst No. Metal Zeolite component Mass fraction of metal component (wt.%) Methods of impregnation, drying and firing Impregnation method Drying temperature (°C), time (h) Firing temperature (°C), time (h) Recovery temperature (°C), time (h) Catalyst A Pt Zeolite 1 1 Impregnation by moisture capacity 120, 12 550, 6 330, 2 Catalyst B Pt + Zn Zeolite 2 0,5 + 3 Impregnation with excess solution 80, 12 600, 4 400, 2 Catalyst C Pd Zeolite 3 2 Impregnation with excess solution 70, 24 550, 6 300, 1 Catalyst D Fe Zeolite 4 6 Impregnation with excess solution 100, 8 550, 6 350, 2 Catalyst E Mn Zeolite 3 8 Impregnation by moisture capacity 60, 24 600, 6 450, 1 Catalyst F Ga Zeolite 1 5 Impregnation with excess solution 120, 10 550, 6 400, 1 Catalyst G Ni Zeolite 4 6 Impregnation with excess solution 90, 8 550, 4 300, 4 Catalyst H Ir + Mn Zeolite 2 0,5 + 5 Impregnation by moisture capacity 80, 24 600, 6 400, 2 Catalyst I Ru + Co Zeolite 1 0,5 + 10 Impregnation with excess solution 120, 12 550, 6 350, 1 Catalyst J Catalyst J was prepared by reaction-reduction treatment of catalyst A (i.e., the catalyst after the reaction in Example 1 was calcined at 550 °C in an air atmosphere for 2 h, and then it was reduced at 300 °C in a hydrogen atmosphere for 2 h) Catalyst K Catalyst K was prepared by reaction-reduction treatment of catalyst J (i.e., the catalyst after the reaction in Example 11 was calcined at 550 °C in air for 2 h, and then it was reduced at 300 °C in hydrogen atmosphere for 2 h)

[0052] Ⅲ. Examples of catalytic reactions

[0053] The catalyst according to the present invention can be used in tank-type reactors.

[0054] The reaction apparatuses were equipped with a gas mass flow meter to control the gas flow rate, and a gas chromatograph was used to quantitatively analyze the products.

[0055] Tank type reactor is taken as an example:

[0056] 2 g of the obtained catalyst and 40 g of polyolefin were mixed and placed in a tank-type reactor. The air in the reactor was purged by purging with CO (0.2–6 MPa and containing 5% Ar as an internal standard for gas chromatographic analysis). The reactor temperature was then increased to 180–300 °C for the reaction. Quantitative analysis of the products was performed using gas chromatography.

[0057] Gaseous products were analyzed using Ar as an internal standard, and product yields were calculated. Liquid products were collected and analyzed using n-undecane as an internal standard, and product yields were calculated.

[0058] The reaction characteristics can be adjusted by changing the reaction temperature, reaction pressure and the mass ratio of CO and polyolefin when feeding.

[0059] The reaction characteristics are as follows: the overall selectivity for aromatic compounds can reach 60–80%, with benzene, toluene, and xylene (BTX) accounting for more than 60% of the aromatic compounds. The introduced CO not only serves as a feedstock for the production of aromatic compounds but also reacts with the hydrogen species generated during hydrogen transfer aromatization, suppressing the formation of alkanes and increasing the selectivity for aromatic components.

[0060] Specific applications of catalysts and their effect data are shown in Table 3.

[0061] Table 3. Specific applications of catalysts and their effect data

[0062] Example Catalyst Temperature (°C) Type of polyolefin The mass ratio of polyolefin to catalyst Partial pressure of CO2 (MPa) Reaction duration (h) CO2 conversion factor (g⋅g-1(polyolefin)⋅h-1) Yield of aromatic compounds (%) The proportion of BTX in aromatic compounds (%) 1 Catalyst A 280 Polyethylene 20 1 4 0,38 68 66 2 Catalyst B 230 Polypropylene 6 3 15 0,11 52 72 3 Catalyst C 300 Waste polyethylene food film 100 2 2 0,50 71 74 4 Catalyst D 270 Polybutene 30 0,5 5 0,34 63 76 5 Catalyst E 250 Polypropylene plastic bottle 15 5 5 0,25 62 67 6 Catalyst F 300 Polyethylene 40 6 3 0,56 75 65 7 Catalyst G 260 Polyethylene plastic bags 20 4 5 0,27 69 66 8 Catalyst H 200 Polybutene 5 0,5 20 0,07 52 78 9 Catalyst I 220 Polypropylene 4 0,8 15 0,11 55 73 10 Catalyst J 280 Waste plastic packaging 20 1 4 0,36 61 71 11 Catalyst K 280 Polyethylene 20 1 4 0,38 68 70 12 Catalyst B 300 Polyethylene 6 3 15 0,58 79 78 13 Catalyst B 280 Polyethylene 6 3 15 0,47 75 76 14 Catalyst B 280 Polyethylene 3 3 15 0,54 76 72 15 Catalyst B 280 Polyethylene 6 1 15 0,49 73 82 16 Catalyst B 280 Polyethylene 6 3 5 0,38 64 73 Comparative example 1 Catalyst L 280 Polyethylene 20 1 4 0,04 4 96 Comparative example 2 Catalyst M 280 Polyethylene 20 1 4 0,26 38 30 Comparative example 3 Catalyst N 280 Polyethylene 20 1 4 0,08 21 54 Comparative example 4 Catalyst O 280 Polyethylene 20 1 4 0,03 11 82 Comparative example 5 Catalyst P 280 Polyethylene 20 1 4 0,05 44 75 Comparative example 6 Catalyst Q 280 Polyethylene 20 1 4 -- 8 3 Comparative example 7 Catalyst R 280 Polyethylene 20 1 4 0,04 35 61 Comparative example 8 Catalyst A 280 Polyethylene ∞ 30 -- 0 0 Comparative example 9 Catalyst A 280 -- 0 -- -- 32 59 Comparative example 10 Catalyst A 280 Polyethylene 20 0,1 4 0,10 49 61

[0063] The metal component and the production method of catalyst L used in Comparative Example 1 were the same as those of catalyst A, but the zeolite component was replaced with commercially available zeolite 5 from Nankai University Catalyst Factory, which has a three-dimensional eight-membered ring porous structure.

[0064] The metal component and the production method of catalyst M used in Comparative Example 2 were the same as those of catalyst A, but the zeolite component was replaced with commercially available zeolite 6 from Nankai University Catalyst Factory, which has a three-dimensional twelve-membered ring porous structure.

[0065] The metal component and the production method of catalyst N used in Comparative Example 3 were the same as those of catalyst A, but the zeolite component was replaced with commercially available zeolite 7 from Nankai University Catalyst Factory, which has a one-dimensional porous structure with coexisting eight- and twelve-membered rings.

[0066] The metal component and the production method of catalyst O used in Comparative Example 4 were the same as those of catalyst A, but the zeolite component was replaced with commercially available zeolite 8 from Nankai University Catalyst Factory, which has a one-dimensional ten-membered ring porous structure.

[0067] The reaction results for Comparative Examples 1–4 indicate that zeolites with different topological structures have a strong impact on product selectivity. Zeolite SAPO-34, with a three-dimensional eight-membered ring structure, is unsuitable for converting polyolefins and producing aromatic compounds. Instead, it is suitable for producing short-chain hydrocarbons with an aromatic yield of only 4%. Zeolite USY, with a three-dimensional twelve-membered ring structure with large pore openings, leads to the formation of heavier aromatic compounds (e.g., naphthalene) and rapid coking deactivation, with heavy aromatic compounds accounting for 70% of the total aromatic products.MOR zeolite, which has a one-dimensional porous structure with coexisting eight- and twelve-membered rings, and SAPO-11 zeolite, which has a one-dimensional ten-membered ring porous structure, are not suitable for aromatization, primarily favoring the formation of low-aromatic cracked gasoline products, comprising 21% aromatics.

[0068] The metal component and the production method of catalyst P used in Comparative Example 5 were the same as those of catalyst A, but the zeolite component was replaced with zeolite 9, which has a medium-strength acid density of only 0.07 mmol / g. The reaction performance of Comparative Example 5 was extremely poor, probably due to insufficient acid density for effective aromatization, highlighting the importance of ensuring the required medium-strength acid density.

[0069] Catalyst Q used in Comparative Example 6 was prepared by direct impregnation of Pt on γ-Al2O3. The results show virtually no CO conversion, low polyolefin conversion, and low yields of aromatics and BTX.

[0070] The zeolite component of catalyst R used in Comparative Example 7 was the same as that of catalyst A (zeolite 1), but lacked the metal component Pt. Since zeolite cannot activate CO, only olefins were aromatized with a low aromatic yield of 38%. In Comparative Example 7, long-chain alkanes were primarily obtained with a low CO conversion rate of only 0.02 g⋅g -1 (полиолефин) ⋅h -1 , which does not provide high selectivity for aromatic compounds or efficient CO utilization.

[0071] Comparative Examples 6 and 7 show that when there is only one functional component, either a metal or a zeolite, the reaction performance is low and significantly worse compared to the excellent reaction performance described in the present invention.

[0072] Both Comparative Example 8 and Example 1 used Catalyst A, but no polyolefin was added in Comparative Example 8. The results show that CO cannot be effectively converted without the polyolefin.

[0073] Both Comparative Example 9 and Example 1 used Catalyst A, but in Comparative Example 9, CO was not added and N2 was used as the pressurizing gas. The results show that the polyolefin can still be converted into aromatic compounds using the bifunctional catalyst without CO, but the yield of aromatic compounds was low (36%), as in Comparative Example 7, and was significantly worse than the excellent reaction performance described in the present invention.

[0074] From the reaction results of Comparative Examples 8 and 9, it can be seen that the conversion of CO and polyolefin is mutually linked and synergistic. Without polyolefin, CO cannot be converted efficiently; and without CO, polyolefin cannot be converted with high selectivity to aromatic compounds, while the amount of alkane byproducts increases.

[0075] Both Comparative Example 10 and Example 1 used catalyst A, but the partial pressure of CO was lower in Comparative Example 10. The insufficient amount of CO weakened its promoting effect on the selectivity of aromatic compounds, highlighting the importance of supplying CO in an amount required for optimal catalytic performance.

[0076] The above results indicate that the topological structure and acidic properties of zeolites, the feeding ratio of CO and polyolefin, and the synergy between metal / metal oxide and zeolites play a key role in determining the selectivity of aromatic compounds, CO conversion ratio, and the contents of benzene, toluene, and xylene in aromatic products.

Claims

1. A method for producing aromatic hydrocarbons by the joint conversion of carbon monoxide and a polyolefin, comprising: using carbon monoxide and a polyolefin as reaction raw materials and using a bifunctional catalyst, wherein one functional component is selected from a metal, a metal oxide and a mixture thereof, and the other functional component is a zeolite; at the same time the zeolite has a topological structure of MFI, MEL or MWW and contains acid sites of medium strength in an amount greater than or equal to 0.1 mol / kg; the metal / metal oxide comprises one or more elements selected from Fe, Co, Ni, Mn, Ce, Cu, Ru, Zn, Ga, Rh, Pd, Ir and Pt; and wherein the carbon monoxide pressure is 0.2–6 MPa, the reaction temperature is 180–400 °C, and the mass ratio of the catalyst to the polyolefin is greater than or equal to 1:

500.

2. The method according to claim 1, characterized in that the mass fraction of metal or metal oxide in the bifunctional catalyst is from 0.1 wt. % to 60 wt. %, wherein the metal or metal oxide is either directly loaded onto the zeolite or distributed on a metal oxide carrier and then physically mixed with the zeolite to form a bifunctional catalyst, wherein the metal oxide carrier is selected from Al2O3, TiO2, ZrO2, CeO2, ZnO, MoO x , MnO x and their mixtures.

3. The method according to claim 1, characterized in that the zeolite with the topological structure MFI, MEL or MWW has a framework containing at least one of Si-O, Si-O-Al, Si-O-Al-P, Si-O-Al-B and Si-O-Al-Ge, and the zeolite with the topological structure MFI, MEL or MWW is preferably at least one of MCM-22, ZSM-11 and ZSM-5.

4. The method according to claim 1, characterized in that the metal or metal oxide and the zeolite are combined in a mechanical mixing or loading mode, wherein the loading mode consists of loading the metal or metal oxide onto the zeolite by impregnation, precipitation by precipitation or precipitation from the vapor phase.

5. The method according to claim 1, characterized in that the component in the form of a metal / metal oxide in the catalyst ensures the activation of CO, and the zeolite ensures the activation of the polyolefin.

6. The method according to claim 1, characterized in that the bifunctional catalyst is preliminarily reduced in an atmosphere of H2 or CO at 300–500 °C for 0.5–10 hours.

7. The method according to paragraph 1, characterized in that when the reaction is carried out in a tank-type reactor, the residence time of the reagents is 0.5–20 hours; when carrying out the reaction in a moving bed reactor, the gas hourly space velocity is 20–2000 ml g -1 ⋅h -1 .

8. The method according to claim 7, characterized in that the polyolefin comprises at least one of polyethylene, polypropylene and polybutene, as well as plastic products made from them, or consumer plastic waste.