Method for converting waste plastics into light olefins in high yield and conversion device

Abstract

The present invention relates to a method for producing light olefins, and more particularly, to a method for producing light olefins, which can increase the production yield of light olefins and minimize the generation of carbon dioxide. The preparation method of the light olefin comprises the following steps: S1) performing pyrolysis on waste plastics to prepare pyrolysis oil and pyrolysis gas; s2) separating the pyrolysis oil and the pyrolysis gas; s3) refining the separated pyrolysis gas so as to prepare first gas without impurities; s4) performing steam reforming reaction on the first gas to prepare second gas; s5) preparing a first synthesis gas from the second gas; s6) converting carbon monoxide in the first synthesis gas into hydrogen and carbon dioxide through a water gas shift reaction to prepare a second synthesis gas; s7) converting the second synthesis gas into methanol through a hydrogenation reaction to prepare a first mixed solution containing methanol; and S8) preparing a second mixed solution containing light olefins from the methanol contained in the first mixed solution through an olefin conversion reaction, and recovering the light olefins from the second mixed solution.

Description

Technical Field

[0001] This invention relates to a method and apparatus for preparing light olefins using waste plastics as raw materials. More specifically, it relates to a method and apparatus for preparing light olefins that can improve the yield of light olefins prepared from waste plastics and can minimize the generation of carbon dioxide. Background Technology

[0002] Waste plastics are made from petroleum and have a low recycling rate, with most being disposed of as waste. These wastes take a long time to decompose naturally, thus polluting the soil and causing serious environmental pollution. Methods for recycling waste plastics include pyrolysis to convert them into usable fractions.

[0003] Waste plastics are mixtures of hydrocarbon fractions with varying boiling points and molecular weight distributions. Therefore, the process of preparing pyrolysis oil from waste plastics generates not only liquid pyrolysis oil but also gaseous pyrolysis gas, with the amount of gas produced being comparable to that of liquid pyrolysis oil. Liquid pyrolysis oil, after separation and refining, is used as fuel and a raw material for various petrochemical industries. However, the pyrolysis gas is reused as pyrolysis fuel or released into the atmosphere after passing through a heat exchanger. This emitted gas contains a large amount of carbon dioxide, thus posing challenges in meeting greenhouse gas emission standards and addressing environmental pollution issues caused by other impurities in the emitted gas.

[0004] In addition, light olefins refer to ethylene, propylene, and butene obtained through naphtha cracking. They are essential raw materials for the petrochemical industry in the preparation of various chemical products such as synthetic resins, synthetic rubber, and alcohols. To date, most ethylene or propylene is mainly produced by pyrolysis of natural gas or hydrocarbon fractions primarily composed of alkane-based compounds such as naphtha or gas oil under catalyst-free conditions in a high-temperature steam atmosphere above 800°C. However, in recent years, with the sharp rise in crude oil prices, the price of light olefin feedstocks has become very high, and the production of light olefins emits large amounts of carbon dioxide, contributing to global warming. To reduce carbon dioxide emissions, it is necessary to develop a process for producing light olefins using resources other than crude oil.

[0005] To address the aforementioned issues, attempts were made to prepare light olefins from waste plastic pyrolysis oil. However, compared to fuel components, waste plastic pyrolysis oil contains excessive impurities such as chlorine, nitrogen, or metals. This not only significantly reduces reactivity and conversion efficiency but also fails to produce high-quality light olefins, hindering economic and commercial viability. The pyrolysis gas produced during waste plastic pyrolysis contains lower levels of impurities such as chlorine and nitrogen than pyrolysis oil and contains large amounts of hydrocarbons such as methane and olefins, making it a promising feedstock for light olefins. However, the process for preparing light olefins using pyrolysis gas has low productivity and is difficult to commercialize.

[0006] Therefore, there is a need to study methods and apparatus that can convert waste plastics into light olefins in high yield.

[0007] [Existing Technical Documents] [Patent Literature] Korean Patent Publication No. 10-2023-0002685A (January 5, 2023) Summary of the Invention

[0008] (a) Technical problems to be solved According to one aspect of the present invention, a conversion method and apparatus can be provided, which can convert waste plastics into light olefins in high yield by pyrolysis.

[0009] According to one aspect of the present invention, a method and apparatus for preparing light olefins can be provided, which can minimize the generation of carbon dioxide and achieve carbon neutrality.

[0010] (II) Technical Solution The method for preparing light olefins according to the present invention includes the following steps: S1) pyrolyzing waste plastics to prepare pyrolysis oil and pyrolysis gas; S2) separating the pyrolysis oil and the pyrolysis gas; S3) purifying the separated pyrolysis gas to prepare a first gas with impurities removed; S4) subjecting the first gas to a steam reforming reaction to prepare a second gas; S5) preparing a first syngas from the second gas; S6) converting carbon monoxide in the first syngas into hydrogen and carbon dioxide through a water-gas shift reaction to prepare a second syngas; S7) converting the second syngas into methanol through a methanol conversion reaction; and S8) converting the methanol into light olefins through an olefin conversion reaction.

[0011] In one example, step S3) may include the following steps: removing impurities from the separated pyrolysis gas to prepare a first gas; and separating olefins from the first gas.

[0012] In one instance, the olefin can be mixed with and recovered from the light olefin of step S8).

[0013] In one instance, the impurity may include one or more selected from tar, sulfur, nitrogen, and chlorine.

[0014] In one instance, in step S4), the second gas may contain hydrogen, carbon monoxide, and carbon dioxide.

[0015] In one example, step S5) may include the following steps: separating the second gas into a first stream containing carbon dioxide and a second stream containing hydrogen and carbon monoxide; converting the first stream into a third stream containing carbon monoxide by a reverse Boudouar reaction; and mixing the third stream and the second stream to prepare a first syngas.

[0016] In one example, the pyrolysis oil may contain one or more fractions selected from aromatic fractions, naphtha, and heavy fractions.

[0017] In one example, the pyrolysis temperature of step S1) can be between 400°C and 600°C.

[0018] In one example, the steam reforming reaction in step S4) can be carried out under a catalyst, which can be a composite catalyst of hydrogenated metal supported on a support.

[0019] In one instance, the hydrogenated metal may be one or more selected from nickel, vanadium, iron, platinum, palladium, or ruthenium.

[0020] In one instance, the reverse boudouard reaction can be carried out at temperatures of 800°C to 1000°C and pressures of 50 kPa to 200 kPa.

[0021] In one example, the second synthesis gas may contain hydrogen and carbon monoxide, and the molar ratio of hydrogen to carbon monoxide may be from 1.9 to 2.1:1.

[0022] In one instance, step S7) can be performed at a temperature of 400°C to 600°C and a pressure of 1 bar to 10 bar.

[0023] In one example, the methanol content in the methanol conversion product of step S7) may be more than 10% by weight relative to the total weight of the product.

[0024] In one instance, step S8) can be performed on a zeolite-based catalyst or an AlPO4-based molecular sieve catalyst.

[0025] In one example, the zeolite-based catalyst or the AlPO4-based molecular sieve catalyst may be ZSM-5, SAPO-34, or a combination thereof.

[0026] The present invention includes a light olefin preparation apparatus.

[0027] The light olefin preparation apparatus according to the present invention comprises: a first reactor for pyrolyzing organic waste to generate pyrolysis oil and pyrolysis gas; a refining unit for receiving the pyrolysis gas and generating refined pyrolysis gas; a second reactor for receiving the refined pyrolysis gas and generating a second gas through a steam reforming reaction; a first syngas generation unit for preparing a first syngas from the second gas; a second syngas generation unit for converting carbon monoxide in the first syngas into hydrogen and carbon dioxide through a water-gas shift reaction to prepare a second syngas; a third reactor for generating methanol from the second syngas through a methanol conversion reaction; and a fourth reactor for generating light olefins from the methanol through an olefin conversion reaction.

[0028] In one example, the refining unit may include: an impurity removal unit for removing impurities; and an olefin separation unit for separating and recovering olefins.

[0029] In one example, the first syngas generation unit may include: an amine scrubber that receives the second gas and separates carbon dioxide; and a reverse Boudouar reactor that receives the carbon dioxide separated from the amine scrubber and performs a reverse Boudouar reaction.

[0030] In one instance, the first to the fourth reactors may comprise a fluidized bed reactor or a fixed bed reactor.

[0031] In one instance, the reverse Boudouar reactor may include a fluidized bed reactor or a fixed bed reactor.

[0032] (III) Beneficial Effects According to one embodiment of the present invention, light olefins can be produced efficiently by pyrolyzing waste plastics.

[0033] According to one embodiment of the present invention, carbon dioxide generation can be minimized during the preparation of light olefins. Attached Figure Description

[0034] Figure 1 A schematic diagram illustrating a method for preparing a light olefin according to the present invention.

[0035] Figure 2 This is a schematic diagram illustrating a method for preparing light olefins according to one embodiment of the present invention.

[0036] Figure 3 A schematic diagram illustrating a light olefin preparation apparatus according to the present invention.

[0037] Figure 4 A schematic diagram illustrating a light olefin preparation apparatus according to one embodiment of the present invention.

[0038] Figure 5 This is a schematic diagram illustrating an olefin separation unit according to one embodiment of the present invention. Detailed Implementation

[0039] In this specification, unless otherwise specified, the singular form of the terms used may be interpreted to include the plural form.

[0040] The numerical ranges used in this specification include lower and upper limits, all values ​​within that range, all values ​​defined therein, and all possible combinations of upper and lower limits of numerical ranges defined in different forms. Unless otherwise specifically defined, values ​​outside the defined numerical range that may arise due to experimental error or rounding are also included within the defined numerical ranges.

[0041] The term “comprising / including” as used in this specification is an open-ended description that is equivalent to expressions such as “possessing,” “containing,” “having,” “characterized in,” etc., and does not exclude elements, materials, or processes not further listed.

[0042] In this specification, unless otherwise defined, the units of % used without special mention refer to weight.

[0043] Waste plastics are mixtures of hydrocarbon fractions with various boiling points and molecular weight distributions. Therefore, in the process of preparing pyrolysis oil from waste plastics, not only is liquid pyrolysis oil generated, but also gaseous pyrolysis gas is produced simultaneously, and the amount of pyrolysis gas produced is comparable to that of liquid pyrolysis oil. Although this pyrolysis gas contains hydrocarbons that can be used as raw materials for light olefins, most of it is emitted as waste gas. Therefore, the inventors of this invention have designed a conversion method and apparatus for efficiently preparing light olefins through the pyrolysis of waste plastics.

[0044] This invention provides a method for preparing light olefins, the method comprising the following steps: S1) pyrolyzing waste plastics to prepare pyrolysis oil and pyrolysis gas; S2) separating the pyrolysis oil and the pyrolysis gas; S3) purifying the separated pyrolysis gas to prepare a first gas; S4) subjecting the first gas to a steam reforming reaction to prepare a second gas; S5) preparing a first syngas from the second gas; S6) converting carbon monoxide in the first syngas into hydrogen and carbon dioxide through a water-gas shift reaction to prepare a second syngas; S7) converting the second syngas into methanol through a methanol conversion reaction; and S8) converting the methanol into light olefins through an olefin conversion reaction.

[0045] In the method for preparing light olefins according to the present invention, compared with the existing light olefin preparation process, the generation of carbon dioxide can be minimized, thereby preventing environmental pollution. Liquid pyrolysis oil can be recovered during the pyrolysis of waste plastics, and high-value-added light olefins can be recovered through the pyrolysis of waste plastics. Therefore, waste resources can be converted efficiently.

[0046] Step S1) is the step of pyrolyzing waste plastics to prepare pyrolysis oil and pyrolysis gas. Specifically, refer to... Figure 1 Waste plastic 300 is introduced into the pyrolysis reactor and pyrolyzed to generate pyrolysis gas and pyrolysis oil (100).

[0047] Specifically, the waste plastic 300 can be household plastic waste (household waste plastic) or industrial plastic waste (industrial waste plastic). The household waste plastic can be polyolefin-based waste plastic, specifically, it can be a mixture of plastics other than polyethylene (PE) and polypropylene (PP), such as polyvinyl chloride (PVC), polystyrene (PS), polyethylene terephthalate (PET), and polybutylene terephthalate (PBT).

[0048] The pyrolysis reaction can be carried out in a batch reactor. Specifically, the pyrolysis reaction can be carried out in any reactor with controllable stirring and heating, for example, in a rotary kiln type batch reactor, but the invention is not limited thereto.

[0049] The pyrolysis temperature can be specifically between 300°C and 900°C, and more specifically between 400°C and 600°C.

[0050] The pyrolysis reaction can be carried out in a non-oxidizing atmosphere. This non-oxidizing atmosphere is one in which the waste plastic will not oxidize (burn), allowing for efficient pyrolysis. The non-oxidizing atmosphere can be, for example, an atmosphere with an oxygen concentration adjusted to below 1% by volume, or an atmosphere containing inert gases such as nitrogen, water vapor, carbon dioxide, and argon. The pyrolysis process can be carried out stably in a low-oxygen atmosphere with an oxygen concentration adjusted to below 1% by volume. The pyrolysis reaction can be carried out in a non-oxidizing atmosphere for 50 to 550 minutes, specifically 150 to 350 minutes. Meeting this holding time allows for activation of the non-oxidizing atmosphere and complete pyrolysis, minimizing energy consumption and operating time, and is therefore preferred.

[0051] Step S2) is to perform gas-liquid separation of pyrolysis oil and pyrolysis gas (100) to recover pyrolysis oil 310 and capture only pyrolysis gas 110.

[0052] Reference Figure 1 It can perform gas-liquid separation on the pyrolysis oil and pyrolysis gas (100) generated from the pyrolysis of waste plastics to recover the liquid pyrolysis oil 310, and only capture the gaseous pyrolysis gas 110, which is then added to the subsequent process.

[0053] The pyrolysis gas 110 may contain hydrogen, carbon monoxide, carbon dioxide, methane, olefins, and C2 to C4 hydrocarbons.

[0054] The pyrolysis oil 310 may contain one or more fractions selected from aromatic fractions, naphtha and heavy fractions.

[0055] According to a specific implementation plan, the pyrolysis oil 310 recovered in step S2) can be recovered in a specific fraction after refining and separation processes.

[0056] Step S3) is a step of purifying the pyrolysis gas 110 separated in step S2) to generate the first gas 120.

[0057] The pyrolysis gas 110 generated from the pyrolysis of waste plastics may contain one or more impurities selected from tar, sulfur, nitrogen, and chlorine. Specifically, the pyrolysis gas 110 may contain water-soluble impurities such as H2S, HCl, HOCl, and NH3, and non-water-soluble impurities such as tar. These impurities contained in the pyrolysis gas 110 can induce catalyst deactivation, which may reduce the efficiency of subsequent processes. Therefore, when refining by removing impurities from the pyrolysis gas 110, the efficiency of the entire process can be improved.

[0058] The purification method for pyrolysis gas 110 can be selected from one or a combination of two or more of the following: using a high-pressure dust filter, water washing, alkaline solution washing, and passing through a ceramic filter. However, it is not limited to the above methods, as long as the method can remove impurities contained in the pyrolysis gas 110. When using water washing or alkaline solution washing, water-soluble impurities such as H2S, HCl, HOCl, and NH3 contained in the pyrolysis gas 110 can be removed. When the pyrolysis gas is passed through a ceramic filter or dust filter, non-water-soluble impurities such as tar and dust can be removed. Through the above purification process, the pyrolysis gas 110 can be purified to be converted into the first gas 120.

[0059] The first gas 120 may contain hydrogen, carbon monoxide, carbon dioxide, methane, olefins, and C2 to C4 hydrocarbons.

[0060] In one specific embodiment of the present invention, reference is made to... Figure 2 Step S3) may include the following steps: removing impurities from the separated pyrolysis gas 110 to prepare a first gas 120; and separating olefins from the first gas 120.

[0061] The steps for removing impurities from the pyrolysis gas 110 are the same as the impurity removal method described above. For the first gas 120, the olefins contained in the first gas 120 can be separated by an olefin separation process to form an olefin feed stream. The components in the first gas 120 other than olefins can be added to step S4) as a subsequent process.

[0062] Since step S3) includes an impurity removal process and an olefin separation process, the olefin stream separated from the pyrolysis gas 110 can be mixed with and recovered from the olefin-containing product 170 ultimately generated by the pyrolysis gas 110, thus further improving the total olefin recovery rate. Furthermore, the subsequent steam reforming process does not require further conversion of olefins into hydrogen and carbon monoxide, thus enabling more efficient process operation.

[0063] The olefin separation step can be carried out by passing a first gas 120 through an adsorption column and a distillation column filled with adsorbent, and can include the following steps: supplying the first gas 120 to the adsorption column to adsorb olefins; and supplying the adsorbed olefins to the distillation column to recover olefins.

[0064] As a non-limiting example, a first gas 120 containing olefins can be fed into an adsorption column filled with adsorbent and contacted with the adsorbent. At this point, the olefins contained in the first gas 120 can be adsorbed by the adsorbent, forming an olefin-adsorbate, thereby separating the olefins contained in the first gas 120 from the first gas 120. The olefin-adsorbate is then fed into a distillation column. In the distillation column, the olefin-adsorbate can be separated into an olefin stream and the adsorbent by distillation. The separated olefin stream can be mixed with and recovered from the olefin-containing product 170 ultimately converted from the pyrolysis gas, and the adsorbent can be reintroduced into the olefin separation step and reused.

[0065] The adsorbent filled in the adsorption tower may include one or more selected from π-complex adsorbents that selectively form adsorbates with olefins, X-type zeolite adsorbents, Y-type zeolite adsorbents, and A-type zeolite adsorbents.

[0066] The olefin adsorption step can be carried out under pressure conditions of 1 standard atmosphere (atm) to 35 standard atmospheres and temperature conditions of 20°C to 150°C.

[0067] The olefin recovery process can be carried out at pressures ranging from 1 to 35 atmospheres and temperatures ranging from 20°C to 150°C.

[0068] Since step S3) further includes a refining process and an olefin separation process, the gas supplied to step S4) may contain hydrogen, carbon monoxide, carbon dioxide, methane, and C2 to C4 hydrocarbons.

[0069] Step S4) is the step of converting the product of step S3) into a second gas 130 through a steam reforming reaction. In step S4), the hydrocarbons contained in the product of step S3) can be reacted with water vapor through a steam reforming reaction to convert them into carbon monoxide and hydrogen, thereby preparing the second gas 130. The steam reforming reaction can carry out any one or more of the following reforming reactions.

[0070] [Reaction Formula 1] CH4+H2O CO + 3H2 [Reaction 2] C x H y +nH2O xCO+(x+y / 2)H2 The second gas 130 may contain hydrogen and carbon monoxide, and may also contain carbon dioxide and unreacted methane from the steam reforming reaction.

[0071] The steam reforming reaction in step S4) can be carried out at a temperature of 600°C to 1400°C and a pressure of 30 kPa to 2000 kPa.

[0072] Step S4) can be operated without a catalyst, but can be operated with a catalyst to improve the reaction conversion rate at low temperatures of 600°C to 700°C. The catalyst in step S4) can be a composite catalyst with a hydrogenated metal supported on a support. The hydrogenated metal can contain one or more of nickel, vanadium, iron, platinum, palladium, or ruthenium. Commonly known metals such as nickel, vanadium, and iron can be used; when the impurity content in raw materials such as organic waste is low during the heat treatment process, noble metals can be used. The noble metal can be platinum, palladium, or ruthenium. The support can be a solid acid substance such as an oxide or zeolite. Specifically, the support can be ZSM-5, ZSM-11, USY zeolite, Ferrite, Mordenite, MCM-22, SUZ-4, or L-type zeolite, silica, alumina, silica-alumina, carbon, zirconium oxide, titanium dioxide, etc.

[0073] Reference Figure 1 Step S5) is the step of preparing the first synthesis gas 140 from the second gas 130 generated in step S4).

[0074] The first synthesis gas 140 may contain hydrogen and carbon monoxide as its main components.

[0075] In one specific implementation plan, refer to Figure 2 Step S5) may include the following steps: separating the second gas 130 into a first stream 210 containing carbon dioxide and a second stream 220 containing hydrogen and carbon monoxide; converting the first stream 210 into a third stream 230 containing carbon monoxide by a reverse Boudouar reaction; and mixing the third stream 230 and the second stream 220 to prepare a first syngas 140.

[0076] Reference Figure 2The second gas 130 can be introduced into the carbon dioxide separation process and separated into a first stream 210 containing carbon dioxide and a second stream 220 containing hydrogen and carbon monoxide. The first stream 210 is supplied to a subsequent step of the reverse Boudouar reaction, and the second stream 220 is supplied to the first syngas preparation unit. The first stream 210 can be converted into carbon monoxide through the reverse Boudouar reaction to form a third stream 230, which is then introduced into the first syngas preparation unit. In the first syngas preparation unit, the second stream 220 and the third stream 230 can be mixed to prepare the first syngas 140. Since step S5) includes the steps according to one specific embodiment described above, the content of carbon monoxide, a reactant in the water-gas shift reaction as a subsequent process, can be increased, and the content of carbon dioxide, a reaction product, can be reduced, thereby improving the reactivity of the water-gas shift reaction and thus improving the efficiency of the entire light olefins preparation process.

[0077] There are no restrictions on the steps for separating carbon dioxide from the second gas 130, as long as the method can separate carbon dioxide from the second gas 130, but it can be done by using various carbon dioxide separation units. As a specific implementation, it can be done by using an amine scrubber. Typically, an amine scrubber uses amine substances to bind and remove carbon dioxide, and can separate components such as carbon dioxide and hydrogen sulfide from the gas vapor, and can recover gases containing hydrogen, carbon monoxide, or inert gases.

[0078] Specifically, as a first amine scrubbing step, a second gas can be added to an amine solution at a temperature of 40°C to 100°C to capture carbon dioxide. As a second amine scrubbing step, the amine solution can be heated to 100°C to 200°C to separate into an amine solution and carbon dioxide. When using the amine scrubbing unit described above, carbon dioxide can be separated at a lower temperature compared to the CCS unit described below, thus offering advantages in terms of process stability.

[0079] As another specific implementation, carbon dioxide separation can be performed using a carbon capture and storage unit (CCS unit). The CCS unit can adsorb and separate carbon dioxide using one or more adsorbents selected from calcium oxide, calcium hydroxide, dolomite, limestone, or natural alkali. Specifically, the adsorbent can be calcium oxide. In the CCS unit, the adsorption of carbon dioxide can be carried out at a temperature above 500°C and below 800°C and a pressure of 300 kPa to 500 kPa. Under these conditions, excellent carbon dioxide adsorption efficiency can be achieved. Specifically, the temperature can be 500°C to 700°C, and the pressure can be 500 kPa to 150 kPa; more specifically, the temperature can be 550°C to 650°C, and the pressure can be 50 kPa to 100 kPa. In the CCS unit, the carbon dioxide adsorbed on the adsorbent is desorbed again, and this desorption can be carried out at a temperature of 500°C to 1000°C and a pressure of 300 kPa to 500 kPa. Under the above conditions, excellent carbon dioxide desorption efficiency can be achieved. Specifically, the temperature can be from 700°C to 950°C, and the pressure can be from 50 kPa to 150 kPa. More specifically, the temperature can be from 850°C to 950°C, and the pressure can be from 50 kPa to 100 kPa.

[0080] The step of converting the first feed stream 210 into a third feed stream 230 containing carbon monoxide via the reverse Boudouar reaction is a step of converting the carbon dioxide contained in the first feed stream 210 into carbon monoxide via the reverse Boudouar reaction. Further conversion of carbon dioxide into carbon monoxide via the reverse Boudouar reaction reduces carbon dioxide emissions, thus preventing environmental pollution. Furthermore, it allows for an increase in the reactant content of subsequent processes, thereby improving the overall yield of light olefins. The reverse Boudouar reaction can be represented by the following reaction formula 3.

[0081] [Reaction 3] C + CO2 2CO In one specific implementation, activated carbon or similar carbon can be supplied to facilitate the reverse Boudouar reaction. Alternatively, the catalyst deactivated by coke or similar materials in step S1) can be used as a carbon source to carry out the reverse Boudouar reaction. Specifically, the carbon source can be char from the organic waste, more specifically, char from the pyrolysis of waste plastics or char from biomass. Alternatively, to avoid the possibility of introducing impurity gases from an external carbon source, high-purity graphite can be included.

[0082] When unreacted carbon dioxide remains after the reverse Boudouar reaction, the carbon dioxide can be separated from the product again, and the separated carbon dioxide can be used to repeat the reverse Boudouar reaction more than once. Therefore, carbon dioxide can be converted into carbon monoxide with very high efficiency.

[0083] The reverse Boudouar reaction can be carried out at a temperature of 700°C to 1000°C and a pressure of 50 kPa to 200 kPa. Under these conditions, excellent efficiency in converting carbon dioxide to carbon monoxide and catalyst regeneration efficiency can be achieved. Specifically, the temperature can be 800°C to 1000°C and the pressure can be 50 kPa to 150 kPa; more specifically, the temperature can be 950°C to 1000°C and the pressure can be 100 kPa to 150 kPa.

[0084] The preparation step of the first syngas 140 may refer to the step of mixing the second stream 220 separated from the second gas 130 with the third stream 230 converted from the first stream 210 by the reverse Boudouar reaction. The first syngas 140 can be prepared by mixing the two streams.

[0085] Step S6) is the step of converting carbon monoxide in the first syngas 140 generated in step S5) into hydrogen through a water-gas shift reaction to prepare the second syngas 150. The water-gas shift reaction can be represented by the following reaction formula 4.

[0086] [Reaction 4] CO + H₂O H2+CO2 The water-gas shift reaction can be carried out in the presence of a catalyst containing one or more metals selected from Fe, Cr, Cu, and Zn. The water-gas shift reaction can be carried out at temperatures ranging from 100°C to 400°C (specifically from 100°C to 300°C) and pressures ranging from 20 bar to 80 bar (specifically from 25 bar to 70 bar).

[0087] In the second syngas generated by the water-gas shift reaction, the molar ratio of hydrogen to carbon monoxide can be from 1.5 to 3:1, specifically from 1.9 to 2.1:1. Since the molar ratio of hydrogen to carbon monoxide in the second syngas meets the above range, the methanol synthesis process, which is a subsequent process, can be carried out efficiently.

[0088] Step S7) is the step of preparing methanol by using hydrogen and carbon monoxide contained in the second synthesis gas 150 as reactants through a methanol conversion reaction. The hydrogenation reaction of carbon monoxide can be represented by the following reaction formula 5.

[0089] [Reaction 5] CO + 2H2 CH3OH In one specific embodiment, step S7) can be carried out under a Cu-based catalyst. Specifically, in order to facilitate methanol conversion at low temperatures, the Cu-based catalyst can be a Cu-based methanol synthesis catalyst, and the support for the Cu-based catalyst can be one or more selected from SiO2, ZrO2, Ga2O3, Al2O3, MgO, and TiO2. Specifically, the Cu-based methanol synthesis catalyst can be Cu / Zr / Al2O3.

[0090] Step S7) can be performed at a temperature of 400°C to 600°C (specifically 430°C to 530°C) and a pressure of 0.1 MPa to 10 MPa (specifically 0.1 MPa to 5 MPa).

[0091] Reference Figure 2 The second synthesis gas 150 can be converted into methanol-containing product 160 containing methanol and water through a methanol conversion reaction. The methanol content can be more than 10% by weight, more than 20% by weight, more than 30% by weight, more than 50% by weight, less than 90% by weight, less than 80% by weight, or less than 70% by weight, specifically from 10% by weight to 90% by weight, and more specifically from 30% by weight to 70% by weight.

[0092] The methanol contained in methanol-containing product 160 can be converted into olefin-containing product 170 through an olefin conversion reaction. The methanol contained in methanol-containing product 160 in step S7) can be contacted with the olefin conversion catalyst in step S8) and converted into olefins.

[0093] In one specific embodiment, step S8) can be carried out under a zeolite-based catalyst or an AlPO4-based molecular sieve catalyst. Specifically, the zeolite-based catalyst may include ZSM-5, and the AlPO4-based catalyst may be a silica alumina phosphate (SAPO) molecular sieve catalyst, specifically one or more selected from SAPO-5, SAPO-8, SAPO-11, SAPO-16, SAPO-17, SAPO-18, SAPO-20, SAPO-31, SAPO-34, SAPO-35, SAPO-44, and SAPO-46.

[0094] Step S8) can be performed at a temperature of 200°C to 600°C (specifically 300°C to 500°C) and a pressure of 1 bar to 10 bar (specifically 1 bar to 5 bar).

[0095] In one specific embodiment, step S8) may further include a step of removing moisture from the olefin-containing product 170. The olefin-containing product 170 may contain water and light olefins, and therefore only the olefins can be recovered by further including a moisture removal step. Known methods can be used for moisture removal, and there are no limitations on the methods employed.

[0096] In one specific implementation, the olefin-containing product 170 recovered in step S8) can be mixed with the olefin stream separated in step S3) and recovered as olefin product 240, and moisture can be removed from olefin product 240 to recover only olefins.

[0097] This invention provides a light olefin preparation apparatus 1000, comprising: a first reactor 10 for pyrolyzing organic waste to generate pyrolysis oil and pyrolysis gas; a refining unit 20 for receiving the pyrolysis gas and generating refined pyrolysis gas; a second reactor 30 for receiving the refined pyrolysis gas and generating a second gas through a steam reforming reaction; a first syngas generation unit 40 for receiving the second gas from the second reactor 30 and generating a first syngas 140; a second syngas generation unit 50 for receiving the first syngas 140 and converting carbon monoxide into hydrogen and carbon dioxide through a water-gas shift reaction to generate a second syngas 150; a third reactor 60 for receiving the second syngas 150 and generating methanol through a methanol conversion reaction; and a fourth reactor 70 for generating light olefins from the methanol through an olefin conversion reaction.

[0098] When using the light olefin preparation apparatus according to the present invention, light olefins can be prepared in high yield by pyrolysis of waste plastics during the pyrolysis process. Furthermore, carbon dioxide emitted as waste gas can be captured and used as a raw material for the preparation of light olefins, thereby preventing environmental pollution. In addition, when the pyrolysis oil generated during pyrolysis is connected to a post-treatment process for the pyrolysis oil, high-quality pyrolysis oil can be recovered simultaneously. That is, by pyrolyzing waste plastics, not only can pyrolysis oil be obtained, but also high-value-added hydrocarbons can be obtained by converting the pyrolysis gas generated during pyrolysis, thus demonstrating excellent waste resource recycling efficiency.

[0099] In one specific embodiment, the first to fourth reactors used in the light olefin preparation apparatus according to the present invention can be batch reactors, fluidized bed reactors, or fixed bed reactors. The use of either fluidized bed or fixed bed reactors is unrestricted, but when using a fluidized bed reactor, advantages in process efficiency may be available.

[0100] Reference Figure 3Waste plastic 300 is introduced into the first reactor 10 and subjected to a pyrolysis reaction to convert the waste plastic 300 into pyrolysis oil 310 and pyrolysis gas 100, which are liquid and gaseous hydrocarbons with various boiling points. The pyrolysis oil 310 is transported to the post-processing process for post-processing through a pipeline connected to the first reactor, and the pyrolysis gas 100 is supplied to the refining unit 20.

[0101] The refining unit 20 may include a sprayer for spraying liquid to bring the pyrolysis gas 100 into contact with water or a weakly alkaline solution containing sodium carbonate, thereby removing water-soluble impurities such as H2S, HCl, HOCl and NH3. Alternatively, a high-pressure dust filter may be used to remove dust, and the unit may include a ceramic filter to remove non-water-soluble impurities such as tar.

[0102] In one specific embodiment, the refining unit 20 may include: an impurity removal unit 20 for removing impurities; and an olefin separation unit 21 for separating and recovering olefins.

[0103] Reference Figure 4 The pyrolysis gas 100 generated in the first reactor is introduced into the refining unit 20, where impurities are discharged to the outside. The first gas 120, from which impurities have been removed, is then introduced into the olefin separation unit 21. The olefins contained in the first gas 120 are separated by the olefin separation unit 21 to form an olefin feed stream. The olefin-free first gas is then conveyed to the second reactor 30. At this point, the olefin feed stream separated from the first gas can be mixed with and recovered from the olefin-containing product 170 ultimately converted from the pyrolysis gas.

[0104] Reference Figure 3 and Figure 4 The second reactor 30 receives the first gas 120 from the refining unit 20 and converts the first gas 120 into a second gas 130 through a steam reforming reaction. Specifically, the first gas 120 received from the refining unit 20 can be converted into hydrogen, carbon monoxide, and carbon dioxide through a steam reforming reaction in the second reactor 30 to generate the second gas 130, whose main components are hydrogen and carbon monoxide.

[0105] Reference Figure 3 The first syngas generation unit 40 receives the second gas 130 from the second reactor 30 and produces the first syngas 140.

[0106] In one specific implementation plan, refer to Figure 4 The first syngas generation unit 40 may further include: an amine scrubber 41, which receives the second gas 130 and separates carbon dioxide; and a reverse Boudouar reactor 42, which receives the carbon dioxide separated from the amine scrubber 41 and performs a reverse Boudouar reaction.

[0107] Since the first syngas generation unit 40 further includes an amine scrubber 41 and a reverse Boudouar reactor 42, the carbon dioxide contained in the first syngas can be converted into carbon monoxide, thereby preventing environmental pollution by reducing carbon dioxide emissions and improving the reactivity of the subsequent methanol conversion process.

[0108] Reference Figure 4 The second gas 130 generated in the second reactor 30 can be introduced into the amine scrubber 41 and separated into a first stream 210 containing carbon dioxide and a second stream 220 without carbon dioxide. The first stream 210 is introduced into the reverse Boudouar reactor 42, where the carbon dioxide contained in the first stream 210 is converted into carbon monoxide to generate a third stream 230 containing carbon monoxide. The third stream 230 is mixed with the second stream 220 separated from the amine scrubber 41 and supplied with first syngas 140 through the first syngas generation unit 40.

[0109] The second syngas generation unit 50 receives the first syngas 140 from the first syngas generation unit 40 and reacts the carbon monoxide contained in the first syngas 140 with water vapor to convert it into hydrogen, thereby generating the second syngas 150.

[0110] The second synthesis gas 150 may contain hydrogen and carbon monoxide as the main components.

[0111] The third reactor 60 can receive a second syngas 150 containing carbon monoxide and hydrogen from the second syngas generation unit 50. The hydrogen and carbon monoxide react to convert the hydrogen into methanol via a methanol conversion reaction to generate a product containing the methanol.

[0112] The fourth reactor 70 can receive the methanol-containing product from the third reactor 60, converting the methanol in the first mixture into light olefins to prepare a product containing olefins and water.

[0113] In one specific embodiment, the second mixture generated in the fourth reactor 70 can be supplied to a separation tower to separate into water and olefin-containing product 170, thereby allowing only the olefin-containing product 170 to be recovered. The separated olefins can be mixed with and recovered from the olefin stream separated from the olefin separation unit 21.

[0114] The present invention will be described in more detail below through examples.

[0115] (Example 1) The waste plastic mixture was dried in an oven at 60°C to remove moisture from the raw materials. The composition of the dried waste plastic mixture is shown in Table 1 below.

[0116] [Table 1] 5000g of dried waste plastic mixture was introduced into the first rotary kiln reactor and pyrolyzed at 600℃ for 1 hour. Pyrolysis gas and pyrolysis oil were then separated. The yields of pyrolysis oil and pyrolysis gas in the pyrolysis recovery are shown in Table 2, and the composition of the pyrolysis gas is shown in Table 3.

[0117] [Table 2] [Table 3] The pyrolysis gas was added to a wet scrubber containing an aqueous sodium hydroxide (NaOH) solution for purification, thereby preparing a first gas with impurities removed. The composition of impurities in the first gas was analyzed before and after adding the first gas to the wet scrubber, and the results are shown in Table 4 below. As shown in Table 4, the purification process effectively removed the impurities contained in the first gas.

[0118] [Table 4] like Figure 5 As shown, a first gas, after impurities have been removed, is passed through an olefin separation unit comprising a demethanizer, a deethanizer, and a depropanizer to separate olefins contained in the first gas. More specifically, the first gas is passed through the demethanizer to separate C1 compounds. The first gas from which C1 compounds have been separated is passed through the deethanizer to separate C2 compounds. The first gas from which C2 compounds have been separated is passed through the depropanizer to selectively separate C3 compounds only, thereby obtaining a purified first gas. The separated C2 compounds are separated into ethane (C2H6) and ethylene (C2H4) in a C2 separator, and the separated C3 compounds are separated into propane (C3H8) and propylene (C3H6) in a C3 separator. Ethylene and propylene are mixed with the final light olefin feed stream, and C1 compounds other than light olefins, ethane, propane, butane, butene, benzene-toluene-xylene (BTX), etc., are mixed to prepare a purified first gas. The composition of the first gas purified by the olefin separation unit is shown in Table 5 below.

[0119] [Table 5] 100 moles of purified first gas were added to a second reactor, which served as a fluidized bed reactor, and steam reforming was carried out. The catalyst was used after reduction at 900°C under an H2 gas atmosphere flowing at a flow rate of 3.03 Nl / min. The steam reforming reaction was carried out for 120 hours at a total flow rate of 3.33 Nl / min and a space velocity of 2.0 L / g. 催化剂(cat) A steam reforming reaction was carried out under conditions of ·h and a water vapor / methane (S / C) ratio of 3. Afterwards, the water vapor was removed to obtain a second gas. The compositions of the purified first and second gases are shown in Table 6 below.

[0120] [Table 6] The second gas is fed into an amine scrubber. A first stream of the second gas containing carbon dioxide is captured by the amine scrubber and separated into a second stream with removed carbon dioxide. Specifically, the second gas is fed into a first amine scrubber. Under conditions of 50°C to 60°C, 10 bar to 20 bar, a throughput of 0.5 Nl / hour, and a molar fraction of 1 for the second gas, CO2 is captured by an aqueous solution containing 12% by weight of NH3. The uncaptured gas is recovered as the second stream. The solution used in the first amine scrubber flows into the second amine scrubber, where it is separated into an aqueous NH3 solution and CO2 at 100°C. The CO2 is recovered as the first stream.

[0121] The first feed stream flows into a fluidized bed reverse Boudouar reactor, where a third feed stream is prepared via the reverse Boudouar reaction. The reverse Boudouar reactor uses a Ni / Al₂O₃ catalyst (32.1% coke) previously used in steam reforming, and high-purity graphite is further added as an external carbon source. The reverse Boudouar reaction is conducted under N₂ gas, at 750°C, with a CO₂ flow rate of 2.33 Nl / min and a space velocity of 2.0 L / g. 催化剂 The experiment was conducted under h conditions. The composition of the gas contained in the first, second, and third feed streams was analyzed and is shown in Table 7.

[0122] [Table 7] The second and third feed streams are mixed to prepare the first syngas. This is achieved at 165°C, 35 bar, and a space velocity of 1.4 L / g. 催化剂Under the reaction conditions of ·h and with a Cu / Zn / Al2O3 catalyst, the first syngas was converted into a second syngas with a CO:H2 ratio of 1:2 via a water-gas shift reaction. The second syngas was then added back into an amine scrubber to further remove residual carbon dioxide, and the residual carbon dioxide separated from the second syngas was recovered to the reverse Boudouar reactor. The gas compositions of the first syngas, the second syngas, and the carbon dioxide-removed second syngas are shown in Table 8 below.

[0123] [Table 8] The second syngas, from which residual carbon dioxide has been removed, is added to a fixed-bed reactor packed with a catalyst for methanol conversion. The catalyst is a 30 wt% Zr and 50 wt% Cu supported on Al₂O₃. To activate the reaction, 30 moles of CO₂ are further added to the reactor before proceeding with the reaction at 245°C, 35 bar, and 1.6 L / g. 催化剂 The methanol conversion reaction was carried out under the reaction conditions of h. The methanol conversion reaction was continuously recycled until the methanol recovery rate reached 2750g (recovery rate of 90% by weight), and the methanol-containing product obtained after the reaction was recovered.

[0124] The recovered methanol was converted to light olefins using a ZSM-5 catalyst. The ZSM-5 catalyst was introduced into a fixed-bed reactor at a concentration of 0.5 ml-MeOH / g. 催化剂 Light olefins were prepared at 400°C and h. The resulting light olefins were mixed with ethylene and propylene separated from the olefin separation unit, and the olefin products were recovered. Then, water was removed, and only the olefins were recovered.

[0125] Gas composition analysis was performed using gas chromatography (GC), and the total amount of gas was confirmed using a gas meter. Specifically, GC was used to quantify the gases to calculate their selectivity, and the composition of each gas was analyzed by measuring the total amount of gas as confirmed by the gas meter. Here, dry gas refers to hydrocarbon gases with four or fewer carbon atoms.

[0126] Referring to Table 6, it can be confirmed that through the reforming reaction of the first gas, dry gas and carbon dioxide are consumed and converted into carbon monoxide and hydrogen. In Table 6, the second gas obtained by the steam reforming reaction is separated by an amine scrubber into a second stream containing residual CO2 and a first stream containing residual CO2. For the first stream, carbon dioxide is converted into carbon monoxide through a reverse Boudouar reaction, thereby preparing the third stream. Specifically, it can be confirmed that the first stream contains 43.3 moles of carbon dioxide and no carbon monoxide, but since the carbon dioxide in the first stream is converted into carbon monoxide through the reverse Boudouar reaction, the third stream contains 22.1 moles of carbon dioxide and 40.7 moles of carbon monoxide. Therefore, it can be concluded that carbon dioxide is converted into carbon monoxide through the reverse Boudouar reaction.

[0127] In this invention, syngas is prepared by recovering carbon dioxide contained in the second gas and then subjecting it to a reverse Boudouar reaction. This not only increases the amount of syngas obtained but also reduces the carbon dioxide content while allowing the syngas to contain more carbon monoxide and hydrogen. Therefore, the yield of the final light olefins can be improved.

[0128] In particular, by conducting a steam reforming reaction, catalyst deactivation caused by the coke generated during the reaction can be minimized, thereby achieving a high syngas production yield. Furthermore, even if coke deposits on the catalyst during the steam reforming reaction, leading to catalyst deactivation, the deactivated catalyst can be added to the reverse Boudouar reaction, using the coke on the catalyst surface as a carbon source for the reverse Boudouar reaction. Therefore, the catalyst can be easily regenerated by conducting only the reverse Boudouar reaction, thus offering the advantage of enabling a continuous process.

[0129] Referring to Table 8, it can be confirmed that after the reverse Boudouar reaction process, a second syngas is produced via a water-gas shift process, with the carbon monoxide to hydrogen ratio in the second syngas controlled at approximately 1:2. By controlling the carbon monoxide to hydrogen ratio in the syngas, the olefin conversion reaction, which is the subsequent process, can be carried out efficiently, thereby significantly improving the yield of hydrocarbons obtained. Specifically, the second syngas produced by the water-gas shift process contains 197.9 moles of H2 and 98.9 moles of CO, while the CO2 content is relatively low, at only 37.1 moles, thus having a favorable effect on improving the syngas production yield and preventing environmental pollution.

[0130] With the increase in syngas production yield, the yield of light olefins from methanol after converting the syngas to methanol also increases. Specifically, when preparing light olefins using the method of Example 1, the methanol conversion rate was 99.3%, and the olefin selectivity was 81%, indicating a significant increase in olefin production yield. Meanwhile, the selectivity for hydrocarbons with more than C4 atoms was low, only 11%. Among the recovered total olefins, the selectivity for ethylene and propylene was measured at 5.1% and 41.2%, respectively, confirming a significant increase in selectivity for light olefins. In particular, by separating ethylene and propylene contained in the first gas in the olefin separation unit and mixing them with the light olefin product, not only can the yield of light olefins be improved, but the process can also be operated more efficiently.

[0131] Therefore, when preparing light olefins according to the method of the present invention, process efficiency can be improved, thus enabling the production of syngas in high yield and increasing the yield of light olefins produced therefrom. Specifically, by employing a steam reforming process and a reverse Boudouar reaction process, irreversible catalyst deactivation can be minimized, thus providing the advantage of a continuous process. Furthermore, the recovery of carbon dioxide from the mixed gas and its conversion to carbon monoxide effectively improves the syngas production yield and reduces greenhouse gas emissions. Moreover, the preparation of syngas with a controlled ratio of hydrogen to carbon monoxide in the mixed gas via a water-gas shift process allows for more efficient subsequent processes, thereby significantly improving the yield of light olefins.

[0132] As described above, the present invention has been illustrated with specific content and limited embodiments, but this is only provided to help to understand the present invention more fully. The present invention is not limited to the above embodiments, and those skilled in the art can make various modifications and variations based on these descriptions.

[0133] Therefore, the concept of this invention should not be limited to the illustrated embodiments, and all contents of the claims of this invention and those equivalent to or having equivalent variations thereof are within the scope of the concept of this invention.

[0134] [Explanation of reference numerals in the attached figures] 10: First reactor; 20: Refining unit 21: Olefin separation unit; 30: Second reactor 40: First synthesis gas generation unit; 41: Amine scrubber 42: Reverse Boudouar reactor; 50: Second syngas generation unit 60: Third reactor; 70: Fourth reactor 100: Pyrolysis products of waste plastics; 110: Pyrolysis gas 120: First gas; 130: Second gas 140: First synthesis gas; 150: Second synthesis gas 160: Products containing methanol; 170: Products containing olefins 210: First material flow; 220: Second material flow 230: Third feed stream; 240: Olefin products 300: Waste plastics; 310: Pyrolysis oil

Claims

1. A method for preparing light olefins, wherein, The preparation method includes the following steps: S1) Pyrolyze waste plastics to prepare pyrolysis oil and pyrolysis gas; S2) Separate the pyrolysis oil and the pyrolysis gas; S3) The separated pyrolysis gas is purified to prepare a first gas with impurities removed; S4) The first gas is subjected to a steam reforming reaction to prepare the second gas; S5) Prepare a first synthesis gas from the second gas; S6) The carbon monoxide in the first syngas is converted into hydrogen and carbon dioxide through a water-gas shift reaction to prepare the second syngas; S7) The second syngas is converted into methanol via a methanol conversion reaction; and S8) The methanol is converted into light olefins via an olefin conversion reaction.

2. The method for preparing light olefins according to claim 1, wherein, Step S3) includes the following steps: Impurities are removed from the separated pyrolysis gas to prepare a first gas; and Olefins are separated from the first gas.

3. The method for preparing light olefins according to claim 2, wherein, The olefin is mixed with the light olefin from step S8) and recovered.

4. The method for preparing light olefins according to claim 2, wherein, The impurities include one or more selected from tar, sulfur, nitrogen and chlorine.

5. The method for preparing light olefins according to claim 1, wherein, In step S4), the second gas contains hydrogen, carbon monoxide, and carbon dioxide.

6. The method for preparing light olefins according to claim 1, wherein, Step S5) includes the following steps: The second gas is separated into a first stream containing carbon dioxide and a second stream containing hydrogen and carbon monoxide; The first feed stream is converted into a third feed stream containing carbon monoxide via a reverse Boudouar reaction; and The third feed stream and the second feed stream are mixed to prepare the first synthesis gas.

7. The method for preparing light olefins according to claim 1, wherein, The pyrolysis oil contains one or more fractions selected from aromatic fractions, naphtha, and heavy fractions.

8. The method for preparing light olefins according to claim 1, wherein, The pyrolysis temperature of step S1) is 400℃ to 600℃.

9. The method for preparing light olefins according to claim 1, wherein, The steam reforming reaction in step S4) is carried out under a catalyst, which is a composite catalyst of hydrogenated metal supported on a support.

10. The method for preparing light olefins according to claim 9, wherein, The hydrogenated metal is selected from one or more of nickel, vanadium, iron, platinum, palladium, or ruthenium.

11. The method for preparing light olefins according to claim 6, wherein, The reverse Boudouar reaction is carried out at temperatures ranging from 800°C to 1000°C and pressures ranging from 50 kPa to 200 kPa.

12. The method for preparing light olefins according to claim 1, wherein, The second synthesis gas contains hydrogen and carbon monoxide, and the molar ratio of hydrogen to carbon monoxide is 1.9 to 2.1:

1.

13. The method for preparing light olefins according to claim 1, wherein, Step S7) is performed at a temperature of 400°C to 600°C and a pressure of 1 bar to 10 bar.

14. The method for preparing light olefins according to claim 1, wherein, In the methanol conversion product of step S7), the methanol content is 10% by weight or more relative to the total weight of the product.

15. The method for preparing light olefins according to claim 1, wherein, Step S8) is carried out in the presence of a zeolite-based catalyst or an AlPO4-based molecular sieve catalyst.

16. The method for preparing light olefins according to claim 15, wherein, The zeolite-based catalyst or the AlPO4-based molecular sieve catalyst is ZSM-5, SAPO-34, or a combination thereof.

17. A light olefin preparation apparatus, wherein, The preparation apparatus includes: The first reactor pyrolyzes organic waste to produce pyrolysis oil and pyrolysis gas; The refining unit receives the pyrolysis gas and generates refined pyrolysis gas; The second reactor receives the refined pyrolysis gas and generates a second gas through a steam reforming reaction. The first syngas generation unit produces first syngas from the second gas; The second syngas generation unit converts carbon monoxide in the first syngas into hydrogen and carbon dioxide through a water-gas shift reaction to produce the second syngas. The third reactor generates methanol from the second syngas via a methanol conversion reaction; and The fourth reactor converts methanol into light olefins via an olefin conversion reaction.

18. The light olefin preparation apparatus according to claim 17, wherein, The refining unit includes: An impurity removal unit is used to remove impurities; and Olefin separation unit, used to separate and recover olefins.

19. The light olefin preparation apparatus according to claim 17, wherein, The first syngas generation unit includes: An amine scrubber receives the second gas and separates carbon dioxide; and The reverse Boudouar reactor receives carbon dioxide separated from the amine scrubber and carries out the reverse Boudouar reaction.

20. The light olefin preparation apparatus according to claim 17, wherein, The first to the fourth reactors include fluidized bed reactors or fixed bed reactors.

21. The light olefin preparation apparatus according to claim 19, wherein, The reverse Boudouar reactor includes a fluidized bed reactor or a fixed bed reactor.

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