Method and apparatus for converting waste plastics into light olefins at high yield

Abstract

The present disclosure 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 method for producing light olefins according to the present disclosure comprises the steps of: S1) pyrolyzing waste plastics to produce pyrolysis oil and pyrolysis gas; S2) separating the pyrolysis oil and pyrolysis gas; S3) producing a first gas from which impurities are removed by purifying the separated pyrolysis gas; S4) steam-reforming the first gas to manufacture a second gas; S5) producing a first synthesis gas from the second gas; S6) producing a second synthesis gas by converting carbon monoxide in the synthesis gas into hydrogen and carbon dioxide through a water gas shift reaction; S7) preparing a first mixed solution containing methanol by converting the second synthesis gas into methanol through a hydrogenation reaction; and (S8) preparing a second mixed solution containing light olefins through an olefin conversion reaction of methanol contained in the first mixed solution, and recovering the light olefins from the second mixed solution.

Description

High-yield method and device for converting waste plastics into light olefins

[0001] The present disclosure relates to a method and a device for producing light olefins using waste plastics as a raw material, and more particularly, to a method and a device for producing light olefins capable of increasing the yield of producing light olefins from waste plastics and minimizing the generation of carbon dioxide.

[0002] Waste plastics, manufactured from petroleum, have a low recyclability and are mostly disposed of as waste. Because they take a long time to decompose naturally, they pollute the soil and cause serious environmental pollution. One method for recycling waste plastics is to thermally decompose them into usable oil.

[0003] Since waste plastic is a mixture of hydrocarbon fractions with various boiling points and molecular weight distributions, the process of producing pyrolysis oil from waste plastic generates both liquid pyrolysis oil and gaseous pyrolysis gas, with the latter being as abundant as the liquid pyrolysis oil. Liquid pyrolysis oil is separated and refined to serve as fuel and as a raw material for various petrochemical industries, while pyrolysis gas is either reused as pyrolysis fuel or discharged into the atmosphere after passing through a heat exchanger. However, this exhaust gas contains a large amount of carbon dioxide, raising concerns about meeting greenhouse gas emission standards and environmental pollution due to other impurities contained within the exhaust gas.

[0004] Meanwhile, light olefins, which refer to ethylene, propylene, and butene obtained through the cracking of naphtha, are essential raw materials for the petrochemical industry, essential for the production of various chemical products such as synthetic resins, synthetic rubber, and alcohol. Currently, most ethylene or propylene is produced through thermal cracking in a steam atmosphere at high temperatures above 800°C under non-catalytic conditions, targeting hydrocarbon fractions mainly composed of paraffinic compounds, such as natural gas, naphtha fraction, and gas oil. However, recently, due to the rapid rise in crude oil prices, the raw material prices for light olefins have risen significantly. In addition, the production of light olefins emits a large amount of carbon dioxide, which contributes to global warming. Therefore, the development of a process to produce light olefins from resources other than crude oil has become necessary to reduce this emissions.

[0005] To solve the above-mentioned problem, there have been attempts to produce such light olefins from waste plastic pyrolysis oil. However, waste plastic pyrolysis oil contains an excessive amount of impurities such as chlorine, nitrogen, and metals compared to the fuel components, which significantly reduces the reaction activity, resulting in a very low conversion efficiency. In addition, it is difficult to produce high-quality light olefins, making it difficult to put it into practical use economically and commercially. The pyrolysis gas generated during the pyrolysis of waste plastic has a lower content of impurities such as chlorine and nitrogen than the pyrolysis oil, but contains a lot of hydrocarbons such as methane and olefins, and is thus attracting attention as a raw material for light olefins. However, the process of producing light olefins from pyrolysis gas has low productivity, making it difficult to utilize and commercialize it.

[0006] Accordingly, research is needed on methods and devices that can convert light olefins from waste plastics at high yields.

[0007] [Prior Art Literature]

[0008] [Patent Document]

[0009] Korean Patent Publication No. 10-2023-0002685 A (January 5, 2023)

[0010] According to one aspect of the present disclosure, a conversion method and a conversion device capable of converting light olefins at a high yield by pyrolyzing waste plastics can be provided.

[0011] According to one aspect of the present disclosure, a method and apparatus for producing light olefins capable of minimizing carbon dioxide generation and achieving carbon neutrality can be provided.

[0012] A method for producing light olefins according to the present disclosure comprises the steps of S1) producing pyrolysis oil and pyrolysis gas by pyrolyzing waste plastics; S2) separating the pyrolysis oil and pyrolysis gas; S3) purifying the separated pyrolysis gas to produce a first gas from which impurities are removed; S4) subjecting the first gas to a steam reforming reaction to produce a second gas; S5) producing 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 produce a second synthesis gas; S7) converting the second synthesis gas into methanol through a methanol conversion reaction; and S8) converting the methanol into a light olefin through an olefin conversion reaction.

[0013] In one example, the step S3) may include a step of producing a first gas by removing impurities from the separated pyrolysis gas; and a step of separating olefin from the first gas.

[0014] In one example, the olefin can be recovered by mixing with the light olefin of the step S8).

[0015] In one example, the impurity may include one or more selected from the group consisting of tar, sulfur, nitrogen and chlorine.

[0016] In one example, in the step S4), the second gas may include hydrogen, carbon monoxide and carbon dioxide.

[0017] In one example, the step S5) may include: 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 through a reverse Budar reaction; and mixing the third stream and the second stream to produce a first synthesis gas.

[0018] In one example, the pyrolysis oil may include one or more fractions selected from the group consisting of aromatic fractions, naphtha fractions, and heavy fractions.

[0019] In one example, the thermal decomposition temperature of step S1) may be 400°C to 600°C.

[0020] In one example, the steam reforming reaction in the step S4) is performed under a catalyst, and the catalyst may be a composite catalyst in which a hydrogenation metal is supported on a support.

[0021] In one example, the hydrogenation metal may be at least one selected from the group consisting of nickel, vanadium, iron, platinum, palladium, or ruthenium.

[0022] In one example, the reverse Boudouard reaction may be performed at a temperature of 800°C to 1000°C and a pressure of 50 KPa to 200 KPa.

[0023] In one example, the second synthesis gas may include hydrogen and carbon monoxide, and the molar ratio of hydrogen:carbon monoxide may be 1.9 to 2.1:1.

[0024] In one example, the step S7) may be performed at a temperature of 400°C to 600°C and a pressure of 1 bar to 10 bar.

[0025] In one example, the methanol conversion product of step S7) may contain methanol in an amount of 10 wt% or more based on the total weight of the product.

[0026] In one example, the step S8) may be performed under a zeolite-based catalyst or an AlPO4-based molecular sieve catalyst.

[0027] In one example, the zeolite catalyst or AlPO4 molecular sieve catalyst may be ZSM-5, SAPO-34, or a combination thereof.

[0028] The present disclosure includes a light olefin production device.

[0029] A light olefin production device according to the present disclosure comprises: a first reactor for thermally decomposing organic waste to produce pyrolysis oil and pyrolysis gas; a purification unit for receiving the pyrolysis gas and producing purified pyrolysis gas; a second reactor for receiving the purified pyrolysis gas and producing a second gas through a steam reforming reaction; a first synthesis gas production unit for producing a first synthesis gas from the second gas; a second synthesis gas production unit for producing a second synthesis gas by converting carbon monoxide in the first synthesis gas into hydrogen and carbon dioxide through a water gas shift reaction; and a third reactor for producing methanol through a methanol conversion reaction from the second synthesis gas; and a fourth reactor for producing a light olefin through an olefin conversion reaction from the methanol.

[0030] In one example, the purification unit may include an impurity removal unit that removes impurities; and an olefin separation unit that separates and recovers olefin.

[0031] In one example, the first synthesis gas generation unit may include an amine scrubber that receives the second gas and separates carbon dioxide; and a reverse Bodah reactor that receives the carbon dioxide separated from the amine scrubber and performs a reverse Bodah reaction.

[0032] In one example, the first to fourth reactors may include a fluidized bed reactor or a fixed bed reactor.

[0033] In one example, the reverse osmosis reactor may include a fluidized bed reactor or a fixed bed reactor.

[0034] According to one embodiment of the present disclosure, light olefins can be produced with high efficiency by pyrolyzing waste plastics.

[0035] According to one embodiment of the present disclosure, the generation of carbon dioxide can be minimized during the process of manufacturing light olefins.

[0036] Figure 1 is a schematic diagram showing a method for producing a light olefin according to the present disclosure.

[0037] Figure 2 is a schematic diagram showing a method for producing a hard olefin according to one embodiment of the present disclosure.

[0038] Figure 3 is a schematic diagram showing a light olefin manufacturing device according to the present disclosure.

[0039] Figure 4 is a schematic diagram showing a rigid olefin manufacturing device according to one embodiment of the present disclosure.

[0040] Figure 5 is a schematic diagram showing an olefin separation unit according to one embodiment of the present disclosure.

[0041] As used herein, the singular forms of terms may be construed to include the plural forms as well, unless otherwise specified.

[0042] The numerical ranges used herein include the lower and upper limits, all values ​​within those limits, all values ​​delimited by these limits, and all possible combinations of the upper and lower limits of numerical ranges defined in different ways. Unless otherwise specified herein, values ​​outside the numerical range that may arise due to experimental error or rounding of values ​​are also included in the defined numerical range.

[0043] The term "includes" as used herein is an open-ended description having the equivalent meaning of expressions such as "comprises," "contains," "has," and "characterizes," and does not exclude additional elements, materials, or processes not listed.

[0044] The unit of % used in this specification without special mention means weight % unless otherwise defined.

[0045] Since waste plastics are a mixture of hydrocarbon fractions with various boiling points and molecular weight distributions, the process of producing pyrolysis oil from waste plastics simultaneously produces both liquid pyrolysis oil and gaseous pyrolysis gas, with as much pyrolysis gas being produced as the liquid pyrolysis oil. Although this pyrolysis gas contains hydrocarbons that serve as raw materials for light olefins, most of it is emitted as exhaust gas. Therefore, the inventors of the present disclosure have devised a conversion method and conversion device capable of pyrolyzing waste plastics to produce light olefins with high efficiency.

[0046] The present disclosure provides a method for producing a light olefin, comprising the steps of S1) producing pyrolysis oil and pyrolysis gas by pyrolyzing waste plastic; S2) separating the pyrolysis oil and pyrolysis gas; S3) purifying the separated pyrolysis gas to produce a first gas; S4) producing a second gas by subjecting the first gas to a steam reforming reaction; S5) producing 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 produce a second synthesis gas; S7) converting the second synthesis gas into methanol through a methanol conversion reaction; and S8) converting the methanol into a light olefin through an olefin conversion reaction.

[0047] The method for producing light olefins according to the present disclosure can prevent environmental pollution by minimizing carbon dioxide emissions compared to conventional light olefin production processes, while not only recovering liquid pyrolysis oil during the process of pyrolyzing waste plastics, but also recovering high value-added light olefins through pyrolysis of waste plastics, thereby efficiently converting waste resources.

[0048] The above step S1) is a step of producing pyrolysis oil and pyrolysis gas by pyrolysis of waste plastic. Specifically, referring to FIG. 1, waste plastic (300) is introduced into a pyrolysis reactor, pyrolysis is performed, and pyrolysis gas and pyrolysis oil (100) are produced.

[0049] Specifically, the above waste plastic (300) may be household plastic waste (household plastic waste) or industrial plastic waste (industrial plastic waste). The household plastic may be polyolefin-based waste plastic, and specifically, may be a mixed plastic of PVC, PS, PET, and PBT other than PE and PP.

[0050] The above pyrolysis reaction may be performed in a batch reactor. Specifically, it may be performed in any reactor capable of stirring and temperature control, and for example, pyrolysis may be performed in a rotary kiln type batch reactor, but the present disclosure is not limited thereto.

[0051] The above thermal decomposition temperature may be specifically 300°C to 900°C, more specifically 400°C to 600°C.

[0052] The above pyrolysis reaction may be carried out in a non-oxidizing atmosphere. The non-oxidizing atmosphere is an atmosphere in which waste plastic does not oxidize (burn), and efficient pyrolysis can proceed in the atmosphere. The non-oxidizing atmosphere is, for example, an atmosphere in which the oxygen concentration is adjusted to 1% by volume or less, and may be an atmosphere of an inert gas such as nitrogen, water vapor, carbon dioxide, and argon. The pyrolysis process can be stably performed in a low-oxygen atmosphere in which the oxygen concentration is 1% by volume or less. The pyrolysis reaction can be carried out in a non-oxidizing atmosphere for 50 to 550 minutes, specifically, for 150 to 350 minutes. When the above holding time is satisfied, the non-oxidizing atmosphere composition can be activated and sufficient pyrolysis can proceed, and energy consumption and operating time can be minimized, which is preferable.

[0053] Step S2) is a step of separating the pyrolysis oil and pyrolysis gas (100) into gas and liquid, recovering the pyrolysis oil (310) and capturing only the pyrolysis gas (110).

[0054] Referring to Figure 1, the pyrolysis oil and pyrolysis gas (100) generated by pyrolyzing waste plastic are separated into gas and liquid phases, and the liquid phase pyrolysis oil (310) is recovered, and only the gas phase pyrolysis gas (110) is captured and can be fed into a subsequent process.

[0055] The above pyrolysis gas (110) may include hydrogen, carbon monoxide, carbon dioxide, methane, olefins, and C2 to C4 hydrocarbons.

[0056] The above pyrolysis oil (310) may include one or more oils selected from the group consisting of aromatic oils, naphtha oils, and heavy oils.

[0057] According to one implementation example, the pyrolysis oil (310) recovered in step S2) can be recovered as a specific oil fraction through a purification and separation process.

[0058] Step S3) is a step of purifying the pyrolysis gas (110) separated in step S2) to produce a first gas (120).

[0059] The pyrolysis gas (110) generated by pyrolyzing waste plastic may contain one or more impurities selected from the group consisting of tar, sulfur, nitrogen, and chlorine. Specifically, the pyrolysis gas (110) may contain water-soluble impurities such as H2S, HCl, HOCl, and NH3, and insoluble impurities such as tar. These impurities contained in the pyrolysis gas (110) may induce deactivation of a catalyst, thereby reducing the efficiency of a subsequent process. Therefore, by removing the impurities from the pyrolysis gas (110) and purifying it, the efficiency of the overall process can be improved.

[0060] The method for purifying the pyrolysis gas (110) may be one or a combination of two or more selected from the group consisting of using a high-pressure dust collection filter, water washing, alkaline solution washing, and passing through a ceramic filter. However, the method is not limited to the above method as long as it can remove impurities contained in the pyrolysis gas (110). When water washing or alkaline solution washing is used, water-soluble impurities such as H2S, HCl, HOCl, and NH3 contained in the pyrolysis gas (110) can be removed, and when the pyrolysis gas is passed through a ceramic filter or dust collection filter, insoluble impurities such as tar and dust can be removed. Through the above-described purification process, the pyrolysis gas (110) can be purified and converted into the first gas (120).

[0061] The first gas (120) may include hydrogen, carbon monoxide, carbon dioxide, methane, olefins, and C2 to C4 hydrocarbons.

[0062] In one embodiment of the present disclosure, referring to FIG. 2, the step S3) may include a step of removing impurities from the separated pyrolysis gas (110) to produce a first gas (120); and a step of separating olefin from the first gas (120).

[0063] The step of removing impurities from the pyrolysis gas (110) is the same as the impurity removal method described above. The first gas (120) is separated from the olefin contained in the first gas (120) through an olefin separation process to form an olefin stream, and components other than the olefin contained in the first gas (120) can be input to the subsequent process, step S4).

[0064] Since the S3) step includes an impurity removal process and an olefin separation process, the olefin stream separated from the pyrolysis gas (110) can be recovered by mixing with the olefin-containing product (170) that is ultimately converted and produced from the pyrolysis gas (110), thereby further improving the overall olefin recovery rate. In addition, since there is no need to additionally convert olefin into hydrogen and carbon monoxide in the subsequent steam reforming process, more efficient process operation is possible.

[0065] The step of separating olefins can be performed by passing the first gas (120) through an adsorption tower and a distillation tower filled with an adsorbent, and can include a step of supplying the first gas (120) to the adsorption tower to adsorb olefins; and a step of supplying the adsorbed olefins to the distillation tower to recover olefins.

[0066] For example, a first gas (120) containing olefins may be moved to an adsorption tower filled with an adsorbent and come into contact with the adsorbent. At this time, the olefins contained in the first gas (120) may be adsorbed to the adsorbent to form an olefin-adsorbent, and the olefins contained in the first gas (120) may be separated from the first gas (120), and the olefin-adsorbent may be moved to a distillation tower. In the distillation tower, the olefin-adsorbent may be separated into an olefin stream and an adsorbent by distillation. The separated olefin stream may be mixed with an olefin-containing product (170) that is ultimately converted from the pyrolysis gas and recovered, and the adsorbent may be reused by being fed back into the olefin separation step.

[0067] The adsorbent filled in the above adsorption tower may include at least one selected from the group consisting of a π-complex adsorbent that selectively forms an adsorbent with olefin, an X-type zeolite, a Y-type zeolite, and an A-type zeolite adsorbent.

[0068] The step of adsorbing the above olefin can be performed under conditions of a pressure of 1 atm to 35 atm and a temperature of 20°C to 150°C.

[0069] The step of recovering olefins can be performed under conditions of a pressure of 1 atm to 35 atm and a temperature of 20°C to 150°C.

[0070] As step S3) further includes a purification process and an olefin separation process, the gas supplied to step S4) may include hydrogen, carbon monoxide, carbon dioxide, methane, and C2 to C4 hydrocarbons.

[0071] Step S4) is a step of converting the product of step S3) into a second gas (130) through a steam reforming reaction. In step S4), the hydrocarbon contained in the product of step S3) is reacted with steam through a steam reforming reaction to convert it into carbon monoxide and hydrogen gas, thereby producing a second gas (130). The steam reforming reaction may be performed by one or more of the following reaction formulas.

[0072] [Reaction Formula 1]

[0073] CH4+ H2O → CO + 3H2

[0074] [Reaction Formula 2]

[0075] C x H y +nH2O→xCO+(x+y / 2)H2

[0076] The second gas (130) contains hydrogen and carbon monoxide, and may also contain carbon dioxide and unreacted methane from the steam reforming reaction.

[0077] The steam reforming reaction of the above step (S4) can be performed at a temperature of 600°C to 1400°C and a pressure of 30 KPa to 2000 KPa.

[0078] The above step S4) may be operated without a catalyst, but may be operated using a catalyst to increase the reaction conversion rate at a low temperature of about 600°C to 700°C. The catalyst of the above step S4) may be a composite catalyst in which a hydrogenation metal is supported on a support. The hydrogenation metal may include one or more selected from nickel, vanadium, iron, platinum, palladium, and ruthenium. The hydrogenation metal may be a commonly known metal such as nickel, vanadium, or iron, and in the case where the impurity content of raw materials such as organic waste is low during the heat treatment process, a precious metal may be used. The precious metal may be platinum, palladium, or ruthenium. The support may be a solid acid material such as an oxide or a zeolite. Specifically, the support may be ZSM-5, ZSM-11, USY zeolite, Ferrierite, Mordenite, MCM-22, SUZ-4 or L-type zeolite, silica, alumina, silica-alumina, carbon, zirconia, titania, etc.

[0079] Step S5) is a step of producing a first synthesis gas (140) from the second gas (130) generated in step S4), referring to FIG. 1.

[0080] The first synthesis gas (140) may contain hydrogen and carbon monoxide as main components.

[0081] In one implementation example, referring to FIG. 2, step S5) may include a step of separating the second gas (130) into a first stream (210) containing carbon dioxide and a second stream (220) containing hydrogen and carbon monoxide; a step of converting the first stream (210) into a third stream (230) containing carbon monoxide through a reverse Budar reaction; and a step of mixing the third stream (230) and the second stream (220) to produce a first synthesis gas (140).

[0082] Referring to FIG. 2, the second gas (130) is introduced into a 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 in which a reverse Buta reaction is performed, and the second stream (220) can be supplied to a first synthesis gas production unit. The first stream (210) is converted into carbon monoxide through the reverse Buta reaction to form a third stream (230), which can be introduced to the first synthesis gas production unit. In the first synthesis gas production unit, the second stream (220) and the third stream (230) can be mixed to produce the first synthesis gas (140). As the S5) step includes steps according to the above-described embodiment, the content of carbon monoxide, which is a reactant of the water-gas shift reaction, which is a subsequent process, can be increased, and the content of carbon dioxide, which is a product of the reaction, can be decreased, thereby improving the reactivity of the water-gas shift reaction, and thus the efficiency of the overall light olefin production process can be improved.

[0083] The step of separating carbon dioxide from the second gas (130) is not limited to any method capable of separating carbon dioxide from the second gas (130), but may be performed using various carbon dioxide separation units. In one embodiment, the step may be performed using an amine scrubber. Typically, an amine scrubber binds and removes carbon dioxide through an amine-based material, and can separate components such as carbon dioxide and hydrogen sulfide from gas vapor, and recover a gas containing hydrogen, carbon monoxide, or an inert gas.

[0084] Specifically, as the first Amine Scrubber stage, a second gas is injected into an amine solution at a temperature of 40°C to 100°C to capture carbon dioxide, and as the second Amine Scrubber stage, the amine solution is heated to 100°C to 200°C to separate the amine solution and carbon dioxide. When the above-described Amine Scrubber is used, carbon dioxide can be separated at a lower temperature compared to the CCS unit described below, which may be advantageous in terms of process stability.

[0085] In another embodiment, the separation of carbon dioxide can be performed using a CCS unit (Carbon capture and storage unit). The CCS unit can adsorb and separate carbon dioxide using an adsorbent comprising one or more selected from calcium oxide, calcium hydroxide, dolomite, limestone, and trona. Specifically, the adsorbent can be calcium oxide. The adsorption of carbon dioxide in the CCS unit can be performed at a temperature of 500°C to 800°C and a pressure of 300 KPa to 500 KPa. Under the above conditions, the carbon dioxide adsorption efficiency can be excellent. Specifically, the temperature can be 500°C to 700°C and the pressure can be 500 KPa to 150 KPa, and more specifically, the temperature can be 550°C to 650°C and the pressure can be 50 KPa to 100 KPa. In the above CCS unit, carbon dioxide adsorbed on the adsorbent is desorbed again, and the desorption can be performed at a temperature of 500°C to 1000°C and a pressure of 300KPa to 500KPa. Under the above conditions, carbon dioxide desorption efficiency can be excellent. Specifically, the temperature can be 700°C to 950°C and a pressure of 50KPa to 150KPa, and more specifically, the temperature can be 850°C to 950°C and a pressure of 50KPa to 100KPa.

[0086] The step of converting the first stream (210) into a third stream (230) containing carbon monoxide through a reverse Boudouard reaction is a step of converting carbon dioxide contained in the first stream (210) into carbon monoxide through a reverse Boudouard reaction. By additionally converting carbon dioxide into carbon monoxide through the reverse Boudouard reaction, environmental pollution can be prevented in terms of reducing the amount of carbon dioxide emitted. In addition, the overall light olefin production yield can be improved in terms of increasing the content of reactants in subsequent processes. The reverse Boudouard reaction may be accompanied by the following reaction scheme 3.

[0087] [Reaction Formula 3]

[0088] C+CO2→ 2CO

[0089] In one embodiment, the reverse-Buda reaction may be performed by supplying carbon such as activated carbon in order to smoothly perform the reverse-Buda reaction, and in another embodiment, the reverse-Buda reaction may be performed by supplying and using a catalyst deactivated by coke or the like in step (S1) as a carbon source. Specifically, the carbon source may be char derived from the organic waste, and more specifically, char derived from pyrolysis of waste plastic or char derived from biomass. Alternatively, high-purity graphite may be included to prevent the possibility of impurity gases being introduced by an external carbon source.

[0090] If unreacted carbon dioxide remains during the reverse-Buda reaction, the carbon dioxide can be separated from the product and the reverse-Buda reaction can be repeated one or more times using the separated carbon dioxide. Accordingly, carbon dioxide can be converted into carbon monoxide with very high efficiency.

[0091] The above reverse Boudouard reaction may be carried out at a temperature of 700°C to 1000°C and a pressure of 50 KPa to 200 KPa. Under the above conditions, the conversion efficiency of carbon dioxide to carbon monoxide and the catalyst regeneration efficiency may be excellent. Specifically, the temperature may be 800°C to 1000°C and the pressure may be 50 KPa to 150 KPa, and more specifically, the temperature may be 950°C to 1000°C and the pressure may be 100 KPa to 150 KPa.

[0092] The step of producing the first synthesis gas (140) may mean mixing the second stream (220) separated from the second gas (130) and the third stream (230) converted from the first stream (210) through a reverse reaction, and the two streams may be mixed to produce the first synthesis gas (140).

[0093] Step S6) is a step of producing a second synthesis gas (150) by converting carbon monoxide contained in the first synthesis gas (140) generated in step S5) into hydrogen through a water-gas shift reaction. The water-gas shift reaction may involve the following chemical formula 4.

[0094] [Chemical Formula 4]

[0095] CO + H2O → H2 + CO2

[0096] The water-gas shift reaction can be carried out in the presence of a catalyst comprising one or more metals selected from the group consisting of Fe, Cr, Cu, and Zn. The water-gas shift reaction can be carried out at a temperature of 100°C to 400°C, specifically 100°C to 300°C, and at a pressure of 20 bar to 80 bar, specifically 25 bar to 70 bar.

[0097] The second synthesis gas produced by the above-described water-gas shift reaction may have a hydrogen:carbon monoxide ratio of 1.5 to 3:1, specifically 1.9 to 2.1:1. As the hydrogen:carbon monoxide ratio in the second synthesis gas satisfies the above-described range, the subsequent methanol synthesis process can be efficiently performed.

[0098] Step S7) is a step of producing methanol through a methanol conversion reaction using hydrogen and carbon monoxide contained in the second synthesis gas (150) as reactants. The hydrogenation reaction of carbon dioxide may involve the following chemical formula 5.

[0099] [Chemical Formula 5]

[0100] CO + 2H2→ CH3OH

[0101] In one embodiment, step S7) may be performed under a Cu-based catalyst. Specifically, in order to facilitate methanol conversion at low temperatures, the Cu-based catalyst may be a Cu-based methanol synthesis catalyst, and the support of the Cu-based catalyst may use at least one selected from the group consisting of SiO2, ZrO2, Ga2O3Al2O3, MgO, and TiO2. Specifically, the Cu-based methanol synthesis catalyst may be Cu / Zr / Al2O3.

[0102] The above step S7) can be performed at a temperature of 400°C to 600°C, specifically 430°C to 530°C, and at a pressure of 0.1 MPa to 10 MPa, specifically 0.1 MPa to 5 MPa.

[0103] Referring to FIG. 2, the second synthesis gas (150) can produce a methanol-containing product (160) including methanol and water through a methanol conversion reaction, and the product can contain methanol in an amount of 10 wt% or more, 20 wt% or more, 30 wt% or more, 50 wt% or more, 90 wt% or less, 80 wt% or less, or 70 wt% or less, based on the total content, and specifically, can contain 10 to 90 wt%, and more specifically, 30 to 70 wt%.

[0104] Methanol contained in the methanol-containing product (160) can be converted into an olefin-containing product (170) through an olefin conversion reaction. Methanol contained in the methanol-containing product (160) in step S7) can be converted into olefin by contacting an olefin conversion catalyst in step S8).

[0105] In one embodiment, the step S8) may be performed 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 silicoaluminaphosphate (SAPO) molecular sieve catalyst, and specifically, may be at least one 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.

[0106] Step S8) can be performed at a temperature of 200°C to 600°C, specifically 300°C to 500°C, and at a pressure of 1 bar to 10 bar, specifically 1 bar to 5 bar.

[0107] In one embodiment, the step S8) may further include a step of removing moisture from the olefin-containing product (170). Since the olefin-containing product (170) may include water and light olefins, the step of removing moisture may be further included to recover only olefins. The method of removing moisture may use a known method, and is not limited thereto.

[0108] In one implementation example, the olefin-containing product (170) recovered in the step S8) may be mixed with the olefin stream separated in the step S5) to be recovered as an olefin product (240), and moisture may be removed from the olefin product (240) to recover only the olefin.

[0109] The present disclosure comprises: a first reactor (10) for pyrolyzing organic waste to produce pyrolysis oil and pyrolysis gas; a purification unit (20) for receiving the pyrolysis gas and producing purified pyrolysis gas; a second reactor (30) for receiving the purified pyrolysis gas and producing a second gas through a steam reforming reaction; a first synthesis gas producing unit (40) for receiving the second gas from the second reactor (30) and producing a first synthesis gas (140); a second synthesis gas producing unit (50) for receiving the first synthesis gas (140) and converting carbon monoxide into hydrogen and carbon dioxide through a water gas shift reaction to produce a second synthesis gas (150); and a third reactor (60) for receiving the second synthesis gas (150) and producing methanol through a methanol conversion reaction. And a light olefin production device (1000) including a fourth reactor (70) that produces light olefin through an olefin conversion reaction of the methanol is provided.

[0110] Using a light olefin manufacturing device according to the present disclosure, light olefins can be manufactured at high yields from the pyrolysis of waste plastics generated during pyrolysis. Furthermore, carbon dioxide emitted as exhaust gas can be captured and used as a raw material for manufacturing light olefins, thereby preventing environmental pollution. Furthermore, by linking the pyrolysis oil generated during pyrolysis to a post-treatment process for the pyrolysis oil, high-quality pyrolysis oil can be recovered. In other words, by pyrolyzing waste plastics, not only pyrolysis oil but also the pyrolysis gas generated during pyrolysis can be converted to produce high-value-added hydrocarbons, thereby achieving an excellent recycling effect of waste resources.

[0111] In one embodiment, the first and fourth reactors used in the light olefin production apparatus according to the present disclosure may be batch reactors, fluidized bed reactors, or fixed bed reactors. Each reactor may be a fluidized bed reactor or a fixed bed reactor without limitation, but using a fluidized bed reactor may be advantageous in terms of process efficiency.

[0112] Referring to FIG. 3, waste plastic (300) is introduced into the first reactor (10), and a pyrolysis reaction is performed so that the waste plastic (300) is converted into pyrolysis oil (310) and pyrolysis gas (100), which are liquid and gaseous hydrocarbons with various boiling points. The pyrolysis oil (310) moves to the post-treatment process along a pipe connected to the first reactor for post-treatment, and the pyrolysis gas (100) is supplied to the purification unit (20).

[0113] The above purification unit (20) includes a sprayer that sprays liquid, and removes water-soluble impurities such as H2S, HCl, HOCl, and NH3 by contacting the pyrolysis gas (100) with a weakly basic solution containing water or sodium carbonate, or removes dust using a high-pressure dust collecting filter, and removes insoluble impurities such as tar by including a ceramic filter, etc.

[0114] In one implementation example, the purification unit (20) may include an impurity removal unit (20) that removes impurities; and an olefin separation unit (21) that separates and recovers olefin.

[0115] Referring to FIG. 4, the pyrolysis gas (100) generated in the first reactor is introduced into the purification unit (20) to discharge impurities to the outside, and the first gas (120) from which the impurities have been removed is introduced into the olefin separation unit (21). The olefin contained in the first gas (120) is separated by the olefin separation unit (21) to form an olefin stream, and the first gas from which the olefin has been separated moves to the second reactor (30). At this time, the olefin stream separated from the first gas can be recovered by being mixed with the olefin-containing product (170) finally converted from the pyrolysis gas.

[0116] Referring to FIGS. 3 and 4, the second reactor (30) receives the first gas (120) from the purification unit (20) and converts the first gas (120) into the second gas (130) through a steam reforming reaction. Specifically, the first gas (120) supplied from the purification unit (20) can be converted into hydrogen, carbon monoxide, and carbon dioxide through a steam reforming reaction in the second reactor (30) to produce the second gas (130) containing hydrogen and carbon monoxide as main components.

[0117] Referring to FIG. 3, the first synthesis gas production unit (40) receives the second gas (130) from the second reactor (30) and produces the first synthesis gas (140).

[0118] In one implementation example, referring to FIG. 4, the first synthesis gas generation unit (40) may further include an amine scrubber (41) that receives the second gas (130) and separates carbon dioxide; and a reverse Buda reactor (42) that receives the carbon dioxide separated from the amine scrubber (41) and performs a reverse Buda reaction.

[0119] Since the above first synthesis gas generation unit (40) further includes an amine scrubber (41) and a reverse catalytic converter (42), carbon dioxide contained in the first synthesis gas can be converted into carbon monoxide, thereby reducing carbon dioxide emissions and preventing environmental pollution, and can improve the reaction activity of a methanol conversion process in the future.

[0120] Referring to FIG. 4, the second gas (130) generated in the second reactor (30) can be introduced into an amine scrubber (41) and separated into a first stream (210) containing carbon dioxide and a second stream (220) not containing carbon dioxide. The first stream (210) is introduced into a reverse condenser 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, and the third stream (230) is mixed with the second stream (220) separated in the amine scrubber (41) to supply the first synthesis gas (140) to the first synthesis gas generation unit (40).

[0121] The second synthesis gas generation unit (50) receives the first synthesis gas (140) from the first synthesis gas generation unit (40) and converts the carbon monoxide and water vapor contained in the first synthesis gas (140) into hydrogen by reacting to generate the second synthesis gas (150).

[0122] The above second synthesis gas (150) may contain hydrogen and carbon monoxide as main components.

[0123] The third reactor (60) receives second synthesis gas (150) containing carbon monoxide and hydrogen from the second synthesis gas generation unit (50), converts hydrogen and carbon monoxide into methanol through a methanol conversion reaction by reacting with each other, and can produce a product containing the methanol.

[0124] The fourth reactor (70) can receive a product containing methanol from the third reactor (60) and convert the methanol in the first mixture into light olefin to produce a product containing olefin and water.

[0125] In one embodiment, the second mixture produced in the fourth reactor (70) is supplied to a separation tower to separate water and an olefin-containing product (170) so that only the olefin product (170) can be recovered, and the separated olefin can be recovered by mixing with the olefin stream separated in the olefin separation unit (21).

[0126] Hereinafter, the present disclosure will be described in more detail through examples.

[0127] (Example 1)

[0128] The waste plastic mixture was dried in a 60°C oven to remove moisture from the raw material. The composition of the dried waste plastic mixture is shown in Table 1 below.

[0129] PETPEPPPSPCPVCOthersComposition(%)3.760.323.80.42.80.19.0

[0130]

[0131] 5,000 g of a dried waste plastic mixture was introduced into a first reactor of a rotary kiln type and treated at 600°C for 1 hour to carry out pyrolysis, after which pyrolysis gas and pyrolysis oil were separated. The yields of pyrolysis oil and pyrolysis gas contained in the pyrolysis recovery are as shown in Table 2 below, and the composition of the pyrolysis gas is as shown in Table 3.

[0132] Recovery yield (%) Pyrolysis oil 59.7 Pyrolysis gas 31.8 Solid product 8.5

[0133] H2CO2COC1C2C3C4paraffinolefinparaffinolefinComposition (mol%)7.90.60.615.19.931.93.521.88.7

[0134] The above pyrolysis gas was purified by feeding it into a wet scrubber containing an aqueous sodium hydroxide (NaOH) solution to produce a first gas from which impurities were removed. The composition of impurities contained in the first gas before and after feeding it into the wet scrubber was analyzed and is shown in Table 4 below. As shown in Table 4 below, it was confirmed that the impurities contained in the first gas were effectively removed through the purification process.

[0135] Impurity Gas Before impurity removal (ppm) After impurity removal (ppm) HCl234<2 H2S1102<3 COS19N / DNH3337<2

[0136] The first gas from which impurities have been removed passes through an olefin separation unit including a demethanizer, a deethanizer, and a depropanizer, as illustrated in Fig. 5, to separate the olefins contained in the first gas. More specifically, the first gas passes through the demethanizer to separate C1 compounds. The first gas from which the C1 compounds have been separated passes through the deethanizer to separate C2 compounds. The first gas from which the C2 compounds have been separated passes through the depropanizer to selectively separate only the C3 compounds, thereby obtaining a purified first gas. The separated C2 compounds were separated into ethane (C2H6) and ethylene (C2H4) in a C2 splitter, and the separated C3 compounds were separated into propane (C3H8) and propylene (C3H6) in a C3 splitter. Ethylene and propylene were mixed with the final light olefin stream produced, and purified first gas was produced by mixing C1 compounds, ethane, propane, butane, butylene, BTX (Benzene, Toluene, Xylene), etc., excluding the light olefins. The composition of the purified first gas passing through the olefin separation unit is shown in Table 5 below.

[0137] Composition (mol%)Weight (g)Composition (mol)H216.915.57.8CO21.325.50.6CO1.113.50.5C132.9241.515.1C221.5296.59.9C37.6153.03.5C418.8405.08.6total1001150.546.0

[0138] 100 mol of purified first gas was injected into the second reactor, which was a fluidized bed reactor filled with 100 g of Ni / Al2O3 catalyst, and steam reformed. The catalyst was used after reduction under an H2 gas atmosphere flowing at 900°C and a flow rate of 3.03 Nl / min. The steam reforming reaction was performed for 120 hours, with a total flow rate of 3.33 Nl / min and a space velocity of 2.0 L / g. cat · A steam reforming reaction was performed under conditions of h and a steam / methane (S / C) ratio of 3. Subsequently, steam was removed to obtain a second gas. The compositions of the purified first and second gases are shown in Table 6 below.

[0139] Purified first gas (mol) Second gas (mol) Dry gas 37.13.0CO2 0.60.2CO0.573.4H2 7.8186.4

[0140] The second gas was introduced into the Amine Scrubber, and the first stream containing carbon dioxide in the second gas was captured in the Amine Scrubber and separated into a second stream from which carbon dioxide was removed. Specifically, the second gas was introduced into the first Amine Scrubber, and CO2 was captured in an aqueous solution containing 12 wt% NH3 under the conditions of 50 to 60°C, 10 to 20 bar, a processing capacity of 0.5 Nl / hr, and a second gas mole fraction of 1, and the uncaptured gas was recovered as the second stream. The solution used in the first Amine Scrubber was introduced into the second Amine Scrubber, and separated into an NH3 aqueous solution and CO2 at 100°C, and the CO2 was recovered as the first stream.

[0141] The first stream was fed into a fluidized bed reverse-Buda reactor and the third stream was produced through the reverse-Buda reaction. The reverse-Buda reactor used a Ni / Al2O3 catalyst (coke ratio 32.1%) used in the steam reforming reaction, and high-purity graphite was additionally added to the reactor as an external carbon source. The reverse-Buda reaction was performed under N2 gas at 750°C, a CO2 flow rate of 2.33 Nl / min, and a space velocity of 2.0 L / g. cat · It was performed under the condition of h. The composition of the gas contained in the first, second, and third streams was analyzed and shown in Table 7.

[0142] 1st stream (mol) 2nd stream (mol) 3rd stream (mol) Dry gas 0 3.0 N / D CO 2 4 3.3 0.1 2 2.1 CO 0 7 3.1 4 0.7 H 2 0 1 8 3.0 N / D Carbon 2 1.3-N / D

[0143] The first synthesis gas was produced by mixing the second and third streams. The first synthesis gas was produced at 165°C, 35 bar, and a space velocity of 1.4 L / g. cat · Under the reaction conditions of h and the Cu / Zn / Al2O3 catalyst, the second synthesis gas was converted into CO:H2=1:2 through the water gas shift reaction. The second synthesis gas was reintroduced into the amine scrubber to further remove the remaining carbon dioxide, and the remaining carbon dioxide separated from the first synthesis gas was recovered in the reverse Buda reactor. The gas compositions of the first synthesis gas, the second synthesis gas, and the second synthesis gas from which carbon dioxide was removed are shown in Table 8 below.

[0144] First synthesis gas (mol) Second synthesis gas (mol) Second synthesis gas with CO2 removed (mol) Dry gas 3.0 2.8 2.7 CO 2 2.2 3 7.1 1.5 CO 1 1 3.8 9 8.9 7.1 H 2 18 3.0 19 7.9 19 1.1

[0145] The second synthesis gas, from which residual carbon dioxide was removed, was fed into a fixed-bed reactor filled with a catalyst containing 30 wt% Zr and 50 wt% Cu supported on Al2O3 to undergo methanol conversion. To initiate the reaction, 30 mol of CO2 was additionally fed into the reactor and then the reaction was carried out at 245°C, 35 bar, and 1.6 L / g. cat · The methanol conversion reaction was performed under reaction conditions of h. The methanol conversion reaction was continuously recycled until the methanol recovery rate reached 2750 g (recovery rate 90 wt%), and the methanol-containing product produced after the reaction was recovered.

[0146] The recovered methanol was converted to light olefins under the ZSM-5 catalyst. The ZSM-5 catalyst was introduced into a fixed-bed reactor, and 0.5 ml-MeOH / g cat · Light olefins were produced at h and 400°C. The produced light olefins were mixed with ethylene and propylene separated in the olefin separation unit to recover olefin products, and then moisture was removed to recover only olefins.

[0147] Gas composition analysis was performed using gas chromatography (GC), and the total amount of gas was confirmed using a gas meter. Specifically, the selectivity for each gas was calculated by quantifying it using GC, and the composition of each gas was analyzed based on the total amount confirmed using the gas meter. Here, dry gas refers to hydrocarbon gases with four or fewer carbon atoms.

[0148] Referring to Table 6 above, it can be confirmed that dry gas and carbon dioxide were consumed and converted into carbon monoxide and hydrogen through the reforming reaction of the first gas. Table 7 shows that the second gas produced through the steam reforming reaction was separated into a second stream in which the residual CO2 contained in the second gas was removed by an amine scrubber and a first stream containing the residual CO2, and the first stream was converted into carbon monoxide through the reverse Buta reaction to produce a third stream. Specifically, the first stream contained 43.3 mol of carbon dioxide and no carbon monoxide, but as the carbon dioxide contained in the first stream was converted into carbon monoxide through the reverse Buta reaction, it was confirmed that the third stream contained 22.1 mol of carbon dioxide and 40.7 mol of carbon monoxide. Therefore, it can be seen that carbon dioxide was converted into carbon monoxide through the reverse Buta reaction.

[0149] The present disclosure produces synthesis gas by recovering carbon dioxide contained in secondary gas and then performing a reverse reaction thereon. This not only increases the quantity of synthesis gas obtained, but also reduces the carbon dioxide content contained in the synthesis gas while simultaneously containing greater amounts of carbon monoxide and hydrogen. Consequently, the yield of light olefins ultimately produced can be improved.

[0150] In particular, by performing a steam reforming reaction, catalyst deactivation due to coke generated during the reaction can be minimized, thereby achieving a high synthesis gas production yield. Furthermore, even if coke deposits on the catalyst during the steam reforming reaction, deactivating it, the deactivated catalyst can be used in a reverse-Buddha reaction, utilizing the coke on the catalyst surface as a carbon source for the reverse-Buddha reaction. Therefore, simply performing the reverse-Buddha reaction alone facilitates catalyst regeneration, enabling a continuous process.

[0151] Referring to Table 8, it can be confirmed that a second synthesis gas was produced with a carbon monoxide and hydrogen ratio controlled to approximately 1:2 through the water gas shift process following the reverse Buddha reaction process. By controlling the ratio of carbon monoxide and hydrogen contained in the synthesis gas, the subsequent olefin conversion reaction is efficiently performed, thereby significantly improving the yield of the obtained hydrocarbon. Specifically, the second synthesis gas that went through the water gas shift process contains 197.9 mol and 98.9 mol of H2 and CO, respectively, while containing only 37.1 mol of CO2, which is advantageous in terms of improving the synthesis gas production yield and preventing environmental pollution.

[0152] As the synthesis gas production yield improved, the yield of light olefins produced from methanol increased after converting the synthesis gas to methanol. Specifically, when producing light olefins using the method of Example 1, the methanol conversion rate was 99.3%, and the olefin selectivity was 81%, indicating a significant improvement in the olefin production yield. At the same time, the selectivity for hydrocarbons higher than C4 was low at 11%, and the selectivity for ethylene and propylene among the total recovered olefins was measured to be 5.1% and 41.2%, respectively, confirming a significant improvement in the selectivity for light olefins. In particular, by separating ethylene and propylene contained in the first gas in the ethylene separation unit and mixing them with the light olefin product, not only did the yield of light olefins improve, but the process could also be operated more efficiently.

[0153] Therefore, when producing light olefins by the method according to the present disclosure, the process efficiency is improved, so that synthesis gas can be produced with a high yield, and the yield of light olefins produced therefrom can be improved. Specifically, by performing the steam reforming process and the reverse Budar reaction process, there is an advantage in that the irreversible deactivation of the catalyst is minimized, enabling a continuous process. In addition, since carbon dioxide in the mixed gas is recovered and converted to carbon monoxide, the yield of synthesis gas production is improved, and there is an effect of reducing greenhouse gas emissions. In addition, since synthesis gas with a controlled ratio of hydrogen and carbon monoxide contained in the mixed gas is produced through the water gas shift process, the subsequent process can be performed more efficiently, thereby significantly improving the yield of light olefins produced.

[0154] As described above, the present invention has been described through specific matters and limited examples, but these are provided only to help a more general understanding of the present invention, and the present invention is not limited to the above examples, and those skilled in the art to which the present invention pertains can make various modifications and variations based on this description.

[0155] Therefore, the spirit of the present invention should not be limited to the described embodiments, and all things that are equivalent or equivalent to the scope of the patent claims described below, as well as the claims, are considered to fall within the scope of the present disclosure.

[0156] [Explanation of symbols]

[0157] 10: First reactor 20: Purification unit

[0158] 21: Olefin separation unit 30: Second reactor

[0159] 40: First synthesis gas production unit 41: Amine scrubber

[0160] 42: Reverse Buda Reactor 50: Second Synthesis Gas Generation Unit

[0161] 60: Reactor 3 70: Reactor 4

[0162] 100: Waste plastic pyrolysis product 110: Pyrolysis gas

[0163] 120: 1st gas 130: 2nd gas

[0164] 140: First synthesis gas 150: Second synthesis gas

[0165] 160: Methanol-containing product 170: Olefin-containing product

[0166] 210: First Stream 220: Second Stream

[0167] 230: Third stream 240: Olefin product

[0168] 300: Waste plastic 310: Pyrolysis oil

Claims

1. S1) A step of producing pyrolysis oil and pyrolysis gas by pyrolyzing waste plastic; S2) A step of separating the pyrolysis oil and pyrolysis gas; S3) A step of purifying the separated pyrolysis gas to produce a first gas from which impurities have been removed; S4) A step of producing a second gas by subjecting the first gas to a steam reforming reaction; S5) A step of producing a first synthesis gas from the second gas; S6) A step of producing a second synthesis gas by converting carbon monoxide in the first synthesis gas into hydrogen and carbon dioxide through a water gas shift reaction; S7) A step of converting the second synthesis gas into methanol through a methanol conversion reaction; and S8) A method for producing light olefin, comprising: a step of converting the methanol into light olefin through an olefin conversion reaction.

2. In paragraph 1, The above step S3) is, A step of producing a first gas by removing impurities from the separated pyrolysis gas; and A method for producing light olefin, comprising: a step of separating olefin from the first gas.

3. In paragraph 2, A method for producing light olefins, wherein the above olefins are recovered by mixing with the light olefins of the above step S8).

4. In paragraph 2, A method for producing light olefins, wherein the impurities include one or more selected from the group consisting of tar, sulfur, nitrogen and chlorine.

5. In paragraph 1, A method for producing light olefins, wherein in the step S4), the second gas contains hydrogen, carbon monoxide and carbon dioxide.

6. In paragraph 1, The above step S5) is, A step of separating the second gas into a first stream containing carbon dioxide and a second stream containing hydrogen and carbon monoxide; A step of converting the first stream into a third stream containing carbon monoxide through a reverse reaction; and A method for producing light olefins, comprising: a step of producing a first synthesis gas by mixing the third stream and the second stream.

7. In paragraph 1, A method for producing light olefins, wherein the pyrolysis oil comprises at least one fraction selected from the group consisting of aromatic fractions, naphtha fractions, and heavy fractions.

8. In paragraph 1, A method for producing light olefin, wherein the thermal decomposition temperature of step S1) is 400 ℃ to 600 ℃.

9. In paragraph 1, A method for producing light olefins, wherein the steam reforming reaction in the step S4) is performed under a catalyst, and the catalyst is a composite catalyst in which a hydrogenation metal is supported on a support.

10. In paragraph 9, A method for producing a light olefin, wherein the hydrogenation metal is at least one selected from the group consisting of nickel, vanadium, iron, platinum, palladium, and ruthenium.

11. In paragraph 6, A method for producing light olefins, wherein the above reverse Boudouard reaction is performed at a temperature of 800° C. to 1000° C. and a pressure of 50 KPa to 200 KPa.

12. In paragraph 1, A method for producing light olefins, wherein the second synthesis gas contains hydrogen and carbon monoxide, and the molar ratio of hydrogen:carbon monoxide is 1.9 to 2.1:

1.

13. In paragraph 1, A method for producing light olefin, wherein the step S7) is performed at a temperature of 400°C to 600°C and a pressure of 1 bar to 10 bar.

14. In paragraph 1, A method for producing light olefins, wherein the methanol conversion product of step S7) contains methanol in an amount of 10 wt% or more based on the total weight of the product.

15. In paragraph 1, The above step S8) is a method for producing light olefins, performed under a zeolite catalyst or an AlPO4 molecular sieve catalyst.

16. In paragraph 15, A method for producing light olefins, wherein the zeolite catalyst or AlPO4 molecular sieve catalyst is ZSM-5, SAPO-34 or a combination thereof.

17. A first reactor in which organic waste is pyrolyzed to produce pyrolysis oil and pyrolysis gas; A purification unit that receives the above pyrolysis gas and produces purified pyrolysis gas; A second reactor which receives the purified pyrolysis gas and generates a second gas through a steam reforming reaction; A first synthesis gas producing unit for producing a first synthesis gas from the second gas; A second synthesis gas production unit that converts carbon monoxide in the first synthesis gas into hydrogen and carbon dioxide through a water gas shift reaction to produce a second synthesis gas; and A third reactor for producing methanol through a methanol conversion reaction of the second synthesis gas; and A light olefin production device, comprising a fourth reactor for producing light olefin through an olefin conversion reaction of the above methanol.

18. In paragraph 17, A light olefin production device, wherein the refining unit comprises an impurity removal unit for removing impurities; and an olefin separation unit for separating and recovering olefin.

19. In Article 17, The first synthesis gas production unit is A light olefin production device comprising: an amine scrubber for separating carbon dioxide by receiving the second gas; and a reverse carbide reactor for performing a reverse carbide reaction by receiving carbon dioxide separated from the amine scrubber.

20. In paragraph 17, A light olefin production device wherein the first to fourth reactors include a fluidized bed reactor or a fixed bed reactor.

21. In paragraph 19, The above-mentioned reverse osmosis reactor is a light olefin production device including a fluidized bed reactor or a fixed bed reactor.

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