A method for preparing olefin raw materials by waste plastic solvent dissolution-catalytic cracking

Abstract

The application discloses a kind of waste plastics solvent dissolution-catalytic cracking preparation olefin raw materials, it is related to solid waste resource utilization and chemical raw material production technical field, the waste plastics solvent dissolution-catalytic cracking preparation olefin raw materials method specifically includes the following steps: step A, solvent dissolution pretreatment, the catalytic cracking reaction also includes device initial solvent dissolution pretreatment of starting, the device initial solvent dissolution pretreatment of starting is that waste plastics is mixed with high-boiling aromatic hydrocarbon solvent in inert atmosphere, 250°C-350°C, 1.0MPa-3.0MPa condition, the plastic solution formed, to obtain the plastic solution prepared in step A, wherein high-boiling aromatic hydrocarbon solvent can use outsourcing raw materials, after device starting, can use device product.The application can efficiently convert mixed waste plastics into high-value olefin raw materials, and by adjusting catalyst and reaction conditions, product distribution can be flexibly controlled, and has very strong industrial application prospect.

Description

Technical Field

[0001] This invention relates to the fields of solid waste resource utilization and chemical raw material production technology, specifically a method for producing olefin raw materials by solvent dissolution and catalytic cracking of waste plastics. Background Technology

[0002] With the widespread use of plastic products, the "white pollution" problem caused by waste plastics is becoming increasingly serious. Traditional treatment methods such as landfill and incineration not only occupy a large amount of land resources but may also cause soil and air pollution. Pyrolysis technology, as a promising recycling method, can convert waste plastics into fuel oil or chemicals, but it still has many shortcomings: traditional pyrolysis requires high purity of raw materials, and mixed waste plastics (such as PE, PP, PS, etc.) are difficult to achieve efficient co-conversion due to different pyrolysis temperatures and mechanisms, resulting in a wide product distribution and poor selectivity, thus making its raw material adaptability poor; moreover, direct pyrolysis usually requires 50°C. Conducting the reaction at temperatures above 0°C or even higher results in enormous energy consumption and a high risk of secondary coking, impacting the long-term operation of the equipment and leading to high reaction temperatures and energy consumption. Furthermore, the direct pyrolysis products are mostly complex mixed hydrocarbon oils, requiring complex separation and refining to obtain high-purity olefins, increasing subsequent processing costs and resulting in low-value products. Additionally, the diverse physical forms of waste plastics, such as bottle flakes and films, easily lead to agglomeration or sedimentation within the reactor, causing uneven solid-liquid contact. Existing stirring or propulsion structures (such as screw propellers) have poor adaptability to high-viscosity systems and low mass transfer rates, resulting in prolonged processing time and reduced yield.

[0003] Therefore, developing a new technology that can efficiently process mixed waste plastics, reduce reaction energy consumption, and produce olefin raw materials with high selectivity has significant practical and economic value. Summary of the Invention

[0004] The purpose of this invention is to provide a method for producing olefin raw materials from waste plastics by solvent dissolution and catalytic cracking, in order to solve the problems of poor raw material adaptability, high energy consumption and low olefin selectivity in existing waste plastics treatment technologies.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for producing olefin raw materials by solvent dissolution and catalytic cracking of waste plastics, wherein the method specifically includes the following steps:

[0006] Step A, solvent dissolution pretreatment, the catalytic cracking reaction also includes solvent dissolution pretreatment at the beginning of the unit start-up, the solvent dissolution pretreatment at the beginning of the unit start-up is carried out by a waste plastic solvent raw material treatment device; Step B, catalytic cracking reaction: The plastic solution prepared in step A is contacted with a modified zeolite molecular sieve catalyst at 400°C - 550°C and 0.1 MPa - 0.5 MPa to carry out catalytic cracking reaction. Step C, product separation and collection, utilizes the separation reaction products to obtain olefin fractions, and recycles unreacted solvents and catalysts. The gaseous products after the reaction enter the separation system, and after cooling, compression and distillation separation, low-carbon olefin fractions rich in ethylene and propylene, C4+ fractions and a small amount of aromatics are obtained. At the same time, after the unreacted solvents and catalysts are separated from the heavy components generated by cracking, the solvents can be recycled back to the dissolution vessel, and the catalysts can be regenerated and reused.

[0007] As a further aspect of the present invention: the solvent dissolution pretreatment at the initial stage of device startup as described in step A involves mixing waste plastic with a high-boiling-point aromatic solvent under an inert atmosphere, at 250°C - 350°C, and at 1.0 MPa - 3.0 MPa to form a plastic solution, thereby obtaining the plastic solution prepared in step A. The high-boiling-point aromatic solvent can be sourced from purchased raw materials, and after the device is started up, the product of the device can be used. The catalytic cracking reaction involves mixing waste plastics with a high-boiling-point aromatic solvent under an inert atmosphere, at 250°C - 350°C, and at 1.0 MPa - 3.0 MPa to form a homogeneous plastic solution. The high-boiling-point aromatic solvent mentioned in step A is one or more of tetrahydronaphthalene, decahydronaphthalene, or dimethylnaphthalene.

[0008] As a further aspect of the present invention: the mass ratio of waste plastic to high-boiling-point aromatic solvent as described in step A is 1:5 to 1:20.

[0009] As a further aspect of the present invention: the modified zeolite molecular sieve catalyst described in step B is an HZSM-5, HY, or USY molecular sieve modified with phosphorus, rare earth elements, or transition metals. The olefin selectivity is high and a specific modified zeolite molecular sieve catalyst is used. Combined with the solvent environment, the cracking pathway can be precisely controlled, effectively suppressing side reactions such as hydrogen transfer and aromatization, and significantly improving the selectivity and yield of target olefins such as ethylene and propylene.

[0010] As a further aspect of the present invention: the catalytic cracking reaction described in step B is carried out in a fixed-bed or fluidized-bed reactor with a weight hourly space velocity (WHSV) of 0.5 h⁻¹. - ¹ - 3.0 h - ¹.

[0011] As a further embodiment of the present invention: the waste plastic solvent raw material processing device includes a tank body, a connecting ring is movably connected to the top of the tank body, a driving component is provided at the top of one side of the tank body, a linkage component is provided at the top of the driving component, an end cap is provided on the top of the tank body, a limiting ring is provided at the bottom of the inner wall of the tank body, and both sides of the limiting ring are fixedly connected to the inner wall of the tank body through fixing blocks. The connecting ring has limit covers at both the top and bottom, and the cross-section of each limit cover is L-shaped. A support ring is located at the middle position of the connecting ring. The bottom of the support ring has multiple sets of teeth evenly arranged. The outside of the support ring has an annular groove. The bottom of the connecting ring has multiple sets of longitudinal scrapers evenly arranged. The outside of each longitudinal scraper has multiple sets of annular scrapers. The bottom of each set of longitudinal scrapers has multiple sets of arc-shaped scrapers evenly arranged. The drive assembly includes a motor, the output end of which is provided with a rotating shaft, and four actuating levers are provided at the four corners of the rotating shaft. Both ends of the actuating levers are arc-shaped, and the other end of the rotating shaft is provided with a gear that meshes with a locking tooth. The linkage component includes a rotating rod, a longitudinal slider on one side of the rotating rod, a linkage disk on the other side of the rotating rod, a toggle block on one side of the linkage disk, and an arc-shaped transverse slider on one side of the rotating rod.

[0012] As a further embodiment of the present invention: one side of the rotating rod is slidably connected to the support ring through an arc-shaped transverse slider and an annular groove, and a ball is provided at the connection end of the arc-shaped transverse slider and the annular groove.

[0013] As a further embodiment of the present invention: a movable gap is provided between the limiting ring and the tank body, the longitudinal scraper is located in the movable gap between the limiting ring and the adjacent end face of the tank body, and the longitudinal scraper is movably connected to the tank body through the movable gap.

[0014] As a further embodiment of the present invention: a support cover is provided at the connection end between the tank body and the end cap. The top end of the inner wall of the support cover is fixedly connected to the bottom end of the end cap. The bottom end of the inner wall of the support cover is fixedly connected to the top end of the tank body. A heat dissipation hole extending into the interior is provided on one side of the support cover. The motor is installed at the bottom end of one side of the support cover.

[0015] As a further embodiment of the present invention: a longitudinal groove matching the longitudinal slider is provided on one side of the inner wall of the support cover, and the rotating rod is longitudinally slidably connected to the support cover through the cooperation of the longitudinal slider and the longitudinal groove.

[0016] Compared with the prior art, the beneficial effects of the present invention are: 1. By dissolving in a solvent, different types of waste plastics are mixed uniformly at the molecular level, eliminating the differences in physical properties between different plastics, realizing the efficient "one-pot" conversion of mixed plastics, and enhancing the adaptability of raw materials. 2. The introduction of solvent effectively reduces the activation energy of plastic macromolecule pyrolysis, allowing catalytic pyrolysis to be carried out at a lower temperature (400-550°C). Compared with traditional pyrolysis (>600°C), this significantly reduces energy consumption, resulting in milder reaction conditions and lower energy consumption. 3. By employing specific modified zeolite molecular sieve catalysts and combining them with the solvent environment, the cracking pathway can be precisely controlled, effectively suppressing side reactions such as hydrogen transfer and aromatization, and significantly improving the selectivity and yield of target olefins such as ethylene and propylene, thereby enhancing olefin selectivity. 4. By enabling both solvents and catalysts to be recycled and reused, the discharge of "three wastes" is reduced, achieving greening of the process and maximizing resource utilization, which meets the requirements of clean production and energy management, thereby making its process integration higher and resource utilization rate higher.

[0017] 5. By utilizing the up-and-down movement of the connecting ring under the influence of the actuating rod, the connecting ring can also be moved laterally under the influence of the gear. This makes the longitudinal scraper, transverse scraper and arc-shaped scraper at its bottom more effective at scraping the residual material on the inner wall of the tank, avoiding its stubborn adhesion to the inner wall of the tank and causing clumping or sedimentation, thus ensuring the uniformity of solid-liquid contact.

[0018] 6. By giving the longitudinal scraper a certain ability to deform under stress, when the longitudinal scraper moves to the end face adjacent to the limiting ring and the tank body, the bottom of the longitudinal scraper near the arc-shaped position will be straightened by the squeezing effect of the limiting ring when passing the side of the limiting ring. When it moves down, the arc-shaped position at the bottom of the longitudinal scraper will bend under the influence of the arc-shaped position at the bottom of the inner wall of the tank. This state can be used to make the contact between the longitudinal scraper and the arc-shaped position at the bottom of the inner wall of the tank more compact, thereby improving the scraping efficiency and avoiding the impact of high strength wear of the longitudinal scraper caused by long-term scraping operations on the scraping operation, thus improving the operating efficiency. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the process flow of the present invention; Figure 2 This is a perspective view of the present invention; Figure 3 This is a partial perspective view of the present invention; Figure 4 This is a schematic diagram of the structure of the driving component of the present invention; Figure 5 This is a schematic diagram of the limiting ring of the present invention; Figure 6 This is a partial structural schematic diagram of the connecting ring of the present invention; Figure 7 This is a schematic diagram of the structure of the present invention; Figure 8 This is a schematic diagram of the movable structure of the lever and linkage plate of the present invention; Figure 9 This is a perspective view of the linkage component of the present invention; Figure 10 This is a partial perspective view of the support cover of the present invention.

[0020] In the picture: 1. Tank body; 101. End cap; 102. Support cover; 103. Limiting ring; 104. Fixing block; 2. Connecting ring; 201. Limiting cover; 202. Support ring; 203. Clamping tooth; 204. Annular groove; 205. Longitudinal scraper; 206. Annular scraper; 207. Arc-shaped scraper; 3. Drive components; 301. Motor; 302. Shaft; 303. Actuating lever; 304. Gear; 4. Linkage components; 401. Rotating rod; 402. Linkage disc; 403. Arc-shaped horizontal slider; 404. Vertical slider; 405. Toggle block. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. In the description of this invention, it should be noted that unless otherwise explicitly specified and limited, the terms "installed," "connected," "linked," and "set up" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. The following describes embodiments of the invention based on its overall structure.

[0022] Please see Figures 1-10 In this embodiment of the invention, Example 1 The raw material is a mixture of waste plastics of polyethylene (PE), polypropylene (PP) and polystyrene (PS) in a mass ratio of 5:3:2. Raw material pretreatment: The mixed plastic is crushed to a particle size of less than 5 mm, washed to remove impurities, and dried at 105°C to constant weight; Solvent dissolution: Take 100 kg of pretreated plastic raw material, add 1000 kg of tetrahydronaphthalene solvent to the dissolving vessel, purge the air with nitrogen, heat to 300°C, stir and maintain the system pressure at 2.0 MPa, keep warm for 1 hour until the plastic is completely dissolved and a transparent and homogeneous solution is formed. Catalytic pyrolysis: The above plastic solution was subjected to 2.0 h... - ¹ The reaction mixture was pumped into a fixed-bed reactor containing phosphorus-modified HZSM-5 molecular sieve catalyst at a weight hourly space velocity (GHSV), and the reaction temperature was controlled at 480°C and the pressure at 0.3 MPa. Product separation: After cooling, the reaction products entered the separation system. Quantitative analysis showed that the total yield of ethylene and propylene (based on the mass of the plastic raw materials) reached 58%, with ethylene yielding 25% and propylene yielding 33%. The C4+ fraction yielded 20%, and the aromatics yielded 10%. Solvent recovery exceeded 98%.

[0023] Example 2 The raw material is a mixture of waste plastics of polyethylene (PE), polypropylene (PP) and polystyrene (PS) in a mass ratio of 5:3:2. Raw material pretreatment: The mixed plastic is crushed to a particle size of less than 5 mm, washed to remove impurities, and dried at 105°C to constant weight; Solvent dissolution: Take 100 kg of pretreated plastic raw material, add 1000 kg of tetrahydronaphthalene solvent to the dissolving vessel, purge the air with nitrogen, heat to 300°C, stir and maintain the system pressure at 2.0 MPa, keep warm for 1 hour until the plastic is completely dissolved and a transparent and homogeneous solution is formed. Catalytic pyrolysis: The above plastic solution was subjected to 2.0 h... - ¹ The mass space velocity was pumped into a fixed-bed reactor containing rare earth lanthanum-modified USY molecular sieve catalyst, and the reaction temperature was controlled at 520°C and the pressure at 0.3 MPa. Product separation: After cooling, the reaction products entered the separation system. Quantitative analysis showed that the total yield of ethylene and propylene (based on the mass of the plastic raw materials) reached 55%, with ethylene yielding 25% and propylene yielding 33%. The C4+ fraction yielded 20%, and the aromatics yielded 15%. Solvent recovery exceeded 98%.

[0024] Please refer to this carefully. Figures 2-10 Waste plastic solvent raw material processing device includes a tank 1, an end cap 101 is provided on the top of the tank 1, a limiting ring 103 is provided at the bottom of the inner wall of the tank 1, both sides of the limiting ring 103 are fixedly connected to the inner wall of the tank 1 by fixing blocks 104, a connecting ring 2 is movably connected to the top of the inside of the tank 1, a driving component 3 is provided at the top of one side of the tank 1, and a linkage component 4 is provided at the top of the driving component 3. Among them, the top and bottom of the connecting ring 2 are provided with limit covers 201, and the cross-section of the limit covers 201 is L-shaped. The middle position of the connecting ring 2 is provided with a support ring 202. The bottom of the support ring 202 is evenly provided with multiple sets of locking teeth 203. The outside of the support ring 202 is provided with an annular groove 204. The bottom of the connecting ring 2 is evenly provided with multiple sets of longitudinal scrapers 205. The outside of the longitudinal scrapers 205 is provided with multiple sets of annular scrapers 206. The bottom of the outer side of each set of longitudinal scrapers 205 is evenly provided with multiple sets of arc-shaped scrapers 207. The drive assembly 3 includes a motor 301, the output end of the motor 301 is provided with a rotating shaft 302, and each of the four corners of the rotating shaft 302 is provided with a lever 303. Both ends of the lever 303 are arc-shaped, and the other end of the rotating shaft 302 is provided with a gear 304 that meshes with the snap tooth 203. The linkage component 4 includes a rotating rod 401, a longitudinal slider 404 on one side of the rotating rod 401, a linkage disk 402 on the other side of the rotating rod 401, a toggle block 405 on one side of the linkage disk 402, and an arc-shaped transverse slider 403 on one side of the rotating rod 401.

[0025] In this embodiment, during use, the material is introduced into the tank 1 (the valve is installed on the discharge pipe at the bottom of the tank 1) through the feed end at the top of the end cap 101. Then, the output end of the motor 301 rotates under the action of electricity, carrying the rotating shaft 302, which directly carries the actuating rod 303 and the gear 304 to rotate. Since the actuating rod 303 is in contact with the actuating block 405, and one end of the actuating rod 303 has an arc-shaped structure, it can directly generate a actuating force on the actuating block 405 located on its side, causing the actuating block 405, which is subjected to force and pressure, to carry the linkage plate 402 to move up and down in the rotating rod 401, the longitudinal slider 404, and the longitudinal slide groove. At the same time, because the linkage plate 402 moves up and down through the arc-shaped transverse slider 403 and the annular slide groove 204... The gear 304 and the connecting ring 2 slide laterally together. Since the gear 304 and the snap tooth 203 are meshed, the connecting ring 2 can be rotated laterally along the notch between the tank body 1 and the end cover 101. The motor 301 continues to rotate, and the actuating block 405 will move down along the arc surface of the other end of the actuating rod 303, which makes it easy for the connecting ring 2 to move down and return to the appropriate position. Thus, the connecting ring 2 can not only move up and down under the influence of the actuating rod 303, but also move laterally under the influence of the gear 304. The longitudinal scraper 205, the annular scraper 206 and the arc-shaped scraper 207 can not only scrape longitudinally, but also scrape laterally, so as to effectively scrape off the material adhering to the inner wall of the tank body 1 and prevent agglomeration. The longitudinal scraper 205 has a certain ability to deform under stress. When the longitudinal scraper 205 moves to the end face of the limiting ring 103 adjacent to the tank body 1, the bottom of the longitudinal scraper 205 near the arc-shaped position will be squeezed by the limiting ring 103 when passing the side of the limiting ring 103, causing the arc-shaped position to be straightened by the force. When it moves down, the arc-shaped position at the bottom of the longitudinal scraper 205 will be bent by the arc-shaped position at the bottom of the inner wall of the tank body 1. This state can be used to make the contact between the longitudinal scraper 205 and the arc-shaped position at the bottom of the inner wall of the tank body 1 more compact, thereby improving the scraping efficiency and avoiding the impact of high strength wear of the longitudinal scraper 205 caused by long-term scraping operation on the scraping operation, thereby improving the operation efficiency. The limiting cover 201 ensures that the outer periphery of the connecting ring 2 is located at the connection edge between the end cap 101 and the tank body 1, so that the connecting ring 2 is always connected to the end cap 101 and the tank body 1 no matter how it moves. In addition, the connection edge between the connecting ring 2 and the end cap 101 and the tank body 1 is provided with a sealing ring, which ensures the sealing of the entire state.

[0026] Please refer to this carefully. Figures 2-10 One side of the rotating rod 401 is slidably connected to the support ring 202 through the arc-shaped transverse slider 403 and the annular groove 204. A ball is provided at the connection end of the arc-shaped transverse slider 403 and the annular groove 204.

[0027] In this embodiment, the contact area between the arc-shaped transverse slider 403 and the annular groove 204 is reduced by using a ball bearing, which makes its operation more effortless during movement and thus improves the transverse movement of the connecting ring 2.

[0028] Please refer to this carefully. Figures 2-10 A movable gap is provided between the limiting ring 103 and the tank body 1. The longitudinal scraper 205 is located in the movable gap between the limiting ring 103 and the adjacent end face of the tank body 1, and the longitudinal scraper 205 is movably connected to the tank body 1 through the movable gap.

[0029] In this embodiment, the set movable gap provides sufficient space for the vertical movement of the longitudinal scraper 205, thereby improving its operation. The inner diameters of the top of the limiting ring 103 and the connecting ring 2 decrease sequentially from top to bottom, and the inner diameters of the bottom of the limiting ring 103 and the connecting ring 2 decrease sequentially from bottom to top. This makes the material sliding down this position smoother, and the material adhering to the moving connecting ring 2 can be flung out by the inertia of the movement. The area of ​​material adhering to the limiting ring 103 is small and can be ignored.

[0030] Please refer to this carefully. Figures 2-10 A support cover 102 is provided at the connection end between the tank body 1 and the end cap 101. The top of the inner wall of the support cover 102 is fixedly connected to the bottom of the outer side of the end cap 101, and the bottom of the inner wall of the support cover 102 is fixedly connected to the top of the outer side of the tank body 1. A heat dissipation hole extending into the inside is provided on one side of the support cover 102. The motor 301 (the motor 301 is a forward and reverse motor. When the connecting ring 2 moves to a position where it can no longer rotate, the output end of the motor 301 reverses under the action of electricity, and causes the connecting ring 2 to reverse and repeat the above operation) is installed at the bottom of one side of the support cover 102.

[0031] In this embodiment, the support cover 102 is used to protect the gap between the tank body 1 and the end cap 101, as well as the drive component 3 and linkage component 4 located on the side of the connecting ring 2. At the same time, the support cover 102 can effectively support the end cap 101, preventing it from being pressed down by force, ensuring the smooth movement of the connecting ring 2, and preventing the normal operation of the connecting ring 2 from being affected by the gravity of the end cap 101.

[0032] Please refer to this carefully. Figures 2-10The inner wall of the support cover 102 is provided with a longitudinal groove that matches the longitudinal slider 404. The rotating rod 401 is longitudinally slidably connected to the support cover 102 through the cooperation of the longitudinal slider 404 and the longitudinal groove.

[0033] In this embodiment, the longitudinal slider 404 and the longitudinal groove cooperate to make the rotating rod 401 slide longitudinally connected to the support cover 102, and move up and down only at this position, and the rotating rod 401 directly acts on the connecting ring 2.

[0034] Working principle: 1. Raw material pretreatment stage, including raw material storage tank → crusher → washing machine → dryer → filter → heat exchanger → electric desalting tank: Raw material storage tanks are used to store mixed waste plastic raw materials and serve as the starting point of the entire process. They control the storage temperature to prevent plastic aging and degradation. The crusher is used to crush mixed waste plastics into uniform particles of 5-10mm. It adopts a shear crusher to process plastics of different hardness and controls the temperature rise during the crushing process to prevent the plastic from melting. The cleaning machine adopts a multi-stage cleaning process: pre-wash → main wash → rinsing, using 60-80℃ hot water and environmentally friendly cleaning agents to remove oil, labels, adhesives and other impurities from the plastic surface, and to separate plastics and impurities of different densities. The dryer uses hot air drying or vacuum drying processes to control the drying temperature at 80-120℃, avoid thermal degradation of plastics, and ensure that the moisture content of the dried plastics is <0.5%. It also uses fluidized bed drying to improve drying efficiency. The filter is used to remove fine impurities and dust that remain after drying. It adopts multi-stage filtration to ensure the cleanliness of raw materials and allows for regular cleaning of the filter screen to maintain filtration efficiency. The heat exchanger is used to preheat clean plastic granules and recover waste heat from subsequent processes, saving energy, while controlling the preheating temperature to prepare for the melting process. Electrostatic desalting tanks are used to remove residual salts and metal impurities from plastics. They employ electrochemical methods to efficiently separate impurities, thereby protecting downstream equipment and extending catalyst lifespan.

[0035] II. The dissolution process, including the electro-desalting tank → dissolution vessel, involves sending pretreated clean plastic granules into the dissolution vessel, adding appropriate solvents, and dissolving them under heating and stirring conditions. The dissolution temperature, stirring speed, and dissolution time are controlled to form a uniform plastic solution, which is then prepared for the pyrolysis reaction.

[0036] III. Catalytic cracking process, including dissolving vessel → high pressure pump → catalytic cracking reactor. The high pressure pump is used to pressurize the plastic solution to the pressure required for the reaction and send it into the catalytic cracking reactor. Cracking occurs under the action of a catalyst. Then, the reaction temperature is controlled at 350-500℃ and the pressure at 1-3MPa, and the plastic macromolecules are cracked into small molecule hydrocarbon compounds.

[0037] IV. Separation process, including catalytic cracking reactor → cyclone separator → fractionation tower The cyclone separator utilizes centrifugal force to separate the gas and solid phases, enabling the recovery of solid catalyst particles for recycling, with a separation efficiency of >99%, thus reducing catalyst loss. The fractionation tower separates the cracking products based on the differences in boiling points of each component, thereby obtaining gasoline fraction, diesel fraction, heavy oil fraction, etc., and controls the temperature at the top and bottom of the tower to optimize product distribution.

[0038] V. Solvent circulation system, including fractionation tower → storage tank → circulation pump → cooler → dissolving vessel. The fractionated solvent components are stored in the storage tank, and then the circulation pump pressurizes and delivers the solvent to the cooler. The cooler reduces the solvent temperature to the requirements of the dissolving process, and the solvent is recycled back to the dissolving vessel for reuse, so that the recovery rate is >95%.

[0039] VI. Catalyst regeneration system, including cyclone separator → catalyst regenerator ← air compressor. The deactivated catalyst recovered from the cyclone separator is sent to the regenerator, and then the air compressor provides the air required for regeneration. The catalyst is burned at 500-600℃ to remove the carbon deposits on the catalyst surface, and the regenerated catalyst is restored to its activity and returned to the catalytic cracking regenerator.

[0040] The entire process achieves efficient chemical recycling of mixed waste plastics, transforming waste plastics into valuable fuel products, while also realizing the recycling of solvents and catalysts, resulting in good economic and environmental benefits.

[0041] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for producing olefin raw materials by solvent dissolution and catalytic cracking of waste plastics, characterized in that, The method for producing olefin raw materials by solvent dissolution and catalytic cracking of waste plastics specifically includes the following steps: Step A, solvent dissolution pretreatment, the catalytic cracking reaction also includes solvent dissolution pretreatment at the beginning of the unit start-up, the solvent dissolution pretreatment at the beginning of the unit start-up is carried out by a waste plastic solvent raw material treatment device; Step B, catalytic cracking reaction: The plastic solution prepared in step A is contacted with a modified zeolite molecular sieve catalyst at 400°C-550°C and 0.1MPa-0.5MPa to carry out catalytic cracking reaction. Step C, product separation and collection, utilizes the separation reaction products to obtain olefin fractions, and recycles unreacted solvents and catalysts. The gaseous products after the reaction enter the separation system, and after cooling, compression and distillation separation, low-carbon olefin fractions rich in ethylene and propylene, C4+ fractions and a small amount of aromatics are obtained. At the same time, after the unreacted solvents and catalysts are separated from the heavy components generated by cracking, the solvents can be recycled back to the dissolution vessel, and the catalysts can be regenerated and reused.

2. The method for producing olefin raw materials by solvent dissolution and catalytic cracking of waste plastics according to claim 1, characterized in that, According to step A, the initial solvent dissolution pretreatment during the initial operation of the device involves mixing waste plastic with a high-boiling-point aromatic solvent under an inert atmosphere, at 250°C-350°C and 1.0MPa-3.0MPa to form a plastic solution, thereby obtaining the plastic solution prepared in step A. The high-boiling-point aromatic solvent can be sourced from purchased raw materials, and after the device is started up, the product of the device can be used. The catalytic cracking reaction involves mixing waste plastics with a high-boiling-point aromatic solvent under an inert atmosphere, at 250°C-350°C, and at 1.0MPa-3.0MPa to form a homogeneous plastic solution. The high-boiling-point aromatic solvent mentioned in step A is one or more of tetrahydronaphthalene, decahydronaphthalene, or dimethylnaphthalene.

3. The method for producing olefin raw materials by solvent dissolution and catalytic cracking of waste plastics according to claim 1, characterized in that, According to step A, the mass ratio of waste plastic to high-boiling-point aromatic solvent is 1:5 to 1:

20.

4. The method for producing olefin raw materials by solvent dissolution and catalytic cracking of waste plastics according to claim 1, characterized in that, The modified zeolite molecular sieve catalyst described in step B is an HZSM-5, HY, or USY molecular sieve modified with phosphorus, rare earth elements, or transition metals. It has high olefin selectivity and uses a specific modified zeolite molecular sieve catalyst. Combined with the solvent environment, it can precisely control the cracking pathway.

5. The method for producing olefin raw materials by solvent dissolution and catalytic cracking of waste plastics according to claim 1, characterized in that, The catalytic cracking reaction described in step B is carried out in a fixed-bed or fluidized-bed reactor at a weight hourly space velocity (WHSV) of 0.5 h⁻¹. - ¹ - 3.0 h - ¹.

6. The method for producing olefin raw materials by solvent dissolution and catalytic cracking of waste plastics according to claim 1, characterized in that, The waste plastic solvent raw material processing device includes a tank, a connecting ring is movably connected to the top of the tank, a drive component is provided at the top of one side of the tank, and a linkage component is provided at the top of the drive component. An end cap is provided on the top of the tank, and a limit ring is provided at the bottom of the inner wall of the tank. Both sides of the limit ring are fixedly connected to the inner wall of the tank by fixing blocks. The connecting ring has limit covers at both the top and bottom, and the cross-section of each limit cover is L-shaped. A support ring is located at the middle position of the connecting ring. The bottom of the support ring has multiple sets of teeth evenly arranged. The outside of the support ring has an annular groove. The bottom of the connecting ring has multiple sets of longitudinal scrapers evenly arranged. The outside of each longitudinal scraper has multiple sets of annular scrapers. The bottom of each set of longitudinal scrapers has multiple sets of arc-shaped scrapers evenly arranged. The drive assembly includes a motor, the output end of which is provided with a rotating shaft, and four actuating levers are provided at the four corners of the rotating shaft. Both ends of the actuating levers are arc-shaped, and the other end of the rotating shaft is provided with a gear that meshes with a locking tooth. The linkage component includes a rotating rod, a longitudinal slider on one side of the rotating rod, a linkage disk on the other side of the rotating rod, a toggle block on one side of the linkage disk, and an arc-shaped transverse slider on one side of the rotating rod. Pretreatment using a waste plastic solvent raw material processing device includes the following steps: Step 1: The motor output directly drives the lever and gear to rotate under the action of electricity. Since the lever is in contact with the lever block and one end of the lever has an arc-shaped structure, it can directly generate a pulling force on the lever block located on its side, causing the linkage plate to move up and down. Step 2: Since the linkage disc and the connecting ring are laterally slidingly connected, and the gear and the locking teeth are meshed, the connecting ring can be rotated laterally under the influence of the driving force. Step 3: As the motor continues to rotate, the actuating block will move down along the arc surface of the other end of the actuating rod, which makes it easier for the connecting ring to move down and return to the appropriate position. This not only allows the connecting ring to move up and down, but also allows the connecting ring to move laterally under the influence of the gears. This causes the longitudinal scraper, the ring scraper, and the arc scraper to scrape laterally while scraping longitudinally, effectively scraping off the material adhering to the inner wall of the tank and preventing clumping. Step four: When the longitudinal scraper moves to the end face adjacent to the limiting ring and the tank body, the bottom of the longitudinal scraper near the arc-shaped position will be straightened by the compression of the limiting ring when passing the side of the limiting ring. After it moves down, the arc-shaped position at the bottom of the longitudinal scraper will bend under the influence of the arc-shaped position at the bottom of the inner wall of the tank, making the contact between the longitudinal scraper and the arc-shaped position at the bottom of the inner wall of the tank more compact. This avoids the problem of high strength wear of the longitudinal scraper due to long-term scraping operations affecting the scraping operation.

7. The method for producing olefin raw materials by solvent dissolution and catalytic cracking of waste plastics according to claim 6, characterized in that, One side of the rotating rod is slidably connected to the support ring via an arc-shaped transverse slider and an annular groove, and a ball is provided at the connection end of the arc-shaped transverse slider and the annular groove.

8. The method for producing olefin raw materials by solvent dissolution and catalytic cracking of waste plastics according to claim 6, characterized in that, A movable gap is provided between the limiting ring and the tank body, and the longitudinal scraper is located in the movable gap between the limiting ring and the adjacent end face of the tank body, and the longitudinal scraper is movably connected to the tank body through the movable gap.

9. The method for producing olefin raw materials by solvent dissolution and catalytic cracking of waste plastics according to claim 6, characterized in that, A support cover is provided at the connection end between the tank body and the end cap. The top of the inner wall of the support cover is fixedly connected to the bottom of the outer end cap, and the bottom of the inner wall of the support cover is fixedly connected to the top of the outer end of the tank body. A heat dissipation hole extending into the inside is provided on one side of the support cover, and the motor is installed at the bottom of one side of the support cover.

10. The method for producing olefin raw materials by solvent dissolution and catalytic cracking of waste plastics according to claim 9, characterized in that, One side of the inner wall of the support cover is provided with a longitudinal sliding groove that matches the longitudinal slider. The rotating rod is longitudinally slidably connected to the support cover through the cooperation of the longitudinal slider and the longitudinal sliding groove.

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