Olefin production process

Abstract

An object of the present invention is to provide an olefin production method that suppresses a decrease in olefin yield and reduces catalyst poisoning in catalytic cracking using waste plastics as a raw material. [Solution] A method for producing olefins, comprising: a thermal decomposition step of thermally decomposing a waste plastic raw material containing polyolefins to obtain a hydrocarbon stream containing olefins; a hydrogenation step of hydrogenating the hydrocarbon stream while leaving at least a portion of the olefins to obtain a hydrogenated product; a crude olefin production step of obtaining crude olefins from the hydrogenated product using a catalyst containing zeolite; and a separation step of separating olefins having 2 to 4 carbon atoms from the crude olefins.

Description

[Technical Field]

[0001] The present invention relates to a process for producing olefins. [Background technology]

[0002] Plastic products are made, for example, from petrochemical products obtained by cracking hydrocarbons derived from crude oil. There are many cracking methods, but fluid catalytic cracking is an example of a cracking method that uses a catalyst. In fluid catalytic cracking, hydrocarbon oil is catalytically cracked using a catalyst containing zeolite or the like, and petrochemical products, fuel oil, etc. are obtained by separation and purification.

[0003] In the above-described fluid catalytic cracking, it is known that high molecular weight components such as heavy oil contained in crude oil or aromatic components undergo polycondensation to form carbonized products (also called coke), and this coke forms on the catalyst surface, deteriorating catalytic activity. Therefore, in fluid catalytic cracking, the coke formed on the catalyst surface is burned and removed from the catalyst to regenerate the catalyst and maintain catalytic activity (see Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-305490 Summary of the Invention [Problem to be solved by the invention]

[0005] Meanwhile, the regeneration and reuse of plastics has been attracting attention from the viewpoint of resource recycling. For example, processes such as reuse, material recycling, and chemical recycling are being carried out to recycle waste plastics. In particular, chemical recycling has the potential to overcome the limitations of performance degradation caused by recycling, as it can chemically decompose plastics and regenerate them into petrochemical raw materials.

[0006] However, when catalytic cracking is performed using a hydrocarbon stream obtained by thermally cracking waste plastic raw materials, the thermal cracking products of the waste plastic raw materials contain poisonous substances such as chlorine-containing compounds that poison the catalyst used in catalytic cracking, which causes a problem of deterioration in catalyst activity regardless of the presence or absence of coke. Although the thermal cracking and catalytic cracking of waste plastics are performed continuously, if one attempts to remove the poisonous substances from the waste plastic raw materials before performing these steps, the concentration of olefins contained in the hydrocarbon stream used as the raw material for catalytic cracking, which can increase the yield of olefins obtained by catalytic cracking, may decrease, resulting in a risk of reducing the yield of olefins and other desired petrochemical raw materials.

[0007] In view of the above problems, an object of the present invention is to provide a method for producing olefins that suppresses a decrease in olefin yield and reduces catalyst poisoning in catalytic cracking using waste plastics as a raw material. [Means for solving the problem]

[0008] The method for producing an olefin according to the present invention comprises the steps of: a pyrolysis step of pyrolyzing a waste plastic raw material containing polyolefins to obtain a hydrocarbon stream containing olefins; a hydrogenation step of hydrogenating the hydrocarbon stream while retaining at least a portion of the olefins to obtain a hydrogenated product; a crude olefin production step of obtaining crude olefins from the hydrogenated product using a catalyst containing zeolite; and a separation step of separating olefins having 2 to 4 carbon atoms from the crude olefins. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a method for producing olefins that suppresses a decrease in the yield of olefins and reduces catalyst poisoning in catalytic cracking using waste plastics as a raw material. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, a method for producing an olefin according to an embodiment of the present invention will be described, but the present invention is not limited to the following embodiment.

[0011] The olefin production method according to the present embodiment includes a thermal decomposition step of thermally decomposing a waste plastic raw material containing polyolefins to obtain a hydrocarbon stream containing olefins; a hydrogenation step of hydrogenating the hydrocarbon stream while leaving at least a portion of the olefins to obtain a hydrogenated product; a crude olefin production step of obtaining crude olefins from the hydrogenated product using a catalyst containing zeolite; and a separation step of separating olefins having 2 to 4 carbon atoms from the crude olefins.

[0012] First, an olefin production apparatus used in the olefin production method according to this embodiment will be described. a pyrolysis device for pyrolyzing a waste plastic raw material containing polyolefins to obtain a hydrocarbon stream containing olefins; a hydrogenation unit for hydrogenating the hydrocarbon stream while retaining at least a portion of the olefins to obtain a hydrogenated product; a catalytic cracking unit for obtaining crude olefins from the hydrogenated product using a catalyst containing zeolite; a separation device for separating olefins having 2 to 4 carbon atoms from the crude olefins; It is equipped with:

[0013] [Pyrolysis equipment] The thermal cracking apparatus is an apparatus for thermally decomposing a waste plastic raw material containing polyolefins to obtain a hydrocarbon stream containing olefins. More specifically, the thermal cracking apparatus is an apparatus for thermally decomposing the waste plastic raw material containing polyolefins to produce a pyrolysate, and obtaining a hydrocarbon stream from the pyrolysate. The thermal cracking apparatus has a reaction vessel for thermally decomposing the waste plastic raw material. The hydrocarbon stream obtained in the thermal cracking apparatus is supplied to a hydrogenation apparatus described below.

[0014] Examples of the thermal decomposition apparatus include a stirred tank thermal decomposition apparatus, a rotary thermal decomposition apparatus, an internal circulating fluidized bed apparatus, and an external circulating fluidized bed apparatus. The stirred tank thermal decomposition apparatus pyrolyzes waste plastics supplied to a reaction vessel by heating the waste plastics from the outside while stirring the waste plastics in the reaction vessel with an agitator. The rotary thermal decomposition apparatus pyrolyzes waste plastics supplied to a reaction vessel while rotating the reaction vessel. The internal circulating fluidized bed apparatus and the external circulating fluidized bed apparatus are apparatuses that can promote thermal decomposition by a fluidized bed formed by fluidized solid particles. The thermal decomposition apparatus may be used alone, or two or more types may be combined and connected in parallel or in series. When two or more types of the thermal decomposition apparatus are combined and connected in parallel, all of the thermal decomposition apparatuses may be operated simultaneously, or some of the thermal decomposition apparatuses may be shut down. The thermal decomposition apparatus is preferably at least one selected from the group consisting of a stirred tank thermal decomposition apparatus, a rotary thermal decomposition apparatus, an internal circulating fluidized bed apparatus, and an external circulating fluidized bed apparatus.

[0015] The internal pressure of the thermal decomposition apparatus is preferably between atmospheric pressure -50 kPaG and atmospheric pressure +50 kPaG.

[0016] The thermal decomposition apparatus may include at least one of a reflux device and a condenser. The reflux device and the condenser liquefy at least a portion of the thermal decomposition product. The thermal decomposition apparatus may include piping connecting the reaction vessel with at least one of the reflux device and the condenser to supply at least a portion of the liquefied thermal decomposition product back to the reaction vessel. The thermal decomposition apparatus may include multiple reflux devices or multiple condensers.

[0017] The thermal decomposition device may heat the waste plastic raw material using any heat source. Examples of the heat source include heat from burning fuel, heat generated by an electric heater, and heat generated during exhaust gas treatment. Examples of the fuel include gaseous pyrolysis products contained in the pyrolysis product, natural gas, etc. The thermal decomposition device may use one type of heat source alone or a combination of two or more types of heat sources.

[0018] [Hydrogenation unit] The hydrogenation unit is a unit that hydrogenates the hydrocarbon stream while retaining at least a portion of the olefins to obtain a hydrogenated product, which is supplied to a catalytic cracking unit described below.

[0019] Examples of the hydrogenation apparatus include a fixed-bed reactor, a fluidized-bed reactor, and a slurry-bed reactor. The hydrogenation apparatus may be used alone, or two or more types may be combined and connected in parallel or series. The hydrogenation apparatus is preferably at least one selected from the group consisting of a fixed-bed reactor, a fluidized-bed reactor, and a slurry-bed reactor.

[0020] The hydrogenation unit may be supplied with a vaporized hydrocarbon stream, a liquefied hydrocarbon stream, or a mixture of a vaporized hydrocarbon stream and a liquefied hydrocarbon stream.

[0021] The hydrogenation unit may be an apparatus that hydrogenates the hydrocarbon stream while leaving at least a portion of the olefins, and then washes the hydrogenated product with water to obtain the hydrogenated product. The olefin production apparatus according to this embodiment may further include a water washing unit that washes the hydrogenated product obtained in the hydrogenation unit with water and supplies it to a catalytic cracking unit described below.

[0022] Hydrogen is supplied to the hydrogenation device. Hydrogen may be supplied to the hydrogenation device from an external source, or hydrogen obtained in a separation device described below may be supplied to the hydrogenation device.

[0023] [Catalytic cracking equipment] The catalytic cracking unit is a unit that obtains crude olefins, which will be described later, from the hydrogenated product using a catalyst containing zeolite. The catalytic cracking unit may be a unit to which the hydrogenated product is supplied, and which brings the hydrocarbons in the hydrogenated product into contact with a catalyst containing zeolite to crack the hydrocarbons, thereby obtaining the crude olefins. The crude olefins obtained in the catalytic cracking unit are supplied to a separation unit, which will be described later.

[0024] Examples of the catalytic cracking unit include a fluidized bed catalytic cracking unit, a moving bed catalytic cracking unit, and a fixed bed catalytic cracking unit. The fluidized bed catalytic cracking unit is a unit that cracks hydrocarbons by contacting a fluidized particulate catalyst with the hydrocarbons. The moving bed catalytic cracking unit is a unit that cracks hydrocarbons by contacting a granular catalyst with the hydrocarbons while moving from the top to the bottom within the unit. The catalytic cracking unit may be used alone, or two or more types may be used in combination, connected in parallel or in series. The catalytic cracking unit is preferably at least one of a fluidized bed catalytic cracking unit and a moving bed catalytic cracking unit, and more preferably a fluidized bed catalytic cracking unit.

[0025] [Separation device] The separation device is a device that separates olefins having 2 to 4 carbon atoms from crude olefins. The separation device may be a device that further separates hydrogen from the crude olefins. That is, the separation device may be a device that separates olefins having 2 to 4 carbon atoms and hydrogen from the crude olefins. The olefins having 2 to 4 carbon atoms obtained by the separation device may be used as various petrochemical feedstocks. The hydrogen obtained by the separation device may be supplied to the hydrogenation device and used for hydrogenation.

[0026] Examples of the separation apparatus include a distillation apparatus, a gas-liquid separation apparatus, an adsorption separation apparatus, a membrane separation apparatus, and a washing apparatus. The separation apparatus may be used alone, or two or more types may be combined and connected in parallel or series. When using a single separation apparatus, the separation apparatus is preferably a distillation apparatus. When using a plurality of separation apparatuses, the plurality of separation apparatuses are preferably at least two types selected from the group consisting of a distillation apparatus, a gas-liquid separation apparatus, an adsorption separation apparatus, a membrane separation apparatus, and a washing apparatus.

[0027] Next, the olefin production method according to this embodiment will be described. The olefin production method according to this embodiment includes a thermal cracking step, a hydrogenation step, a crude olefin production step, and a separation step.

[0028] (pyrolysis process) The thermal decomposition process is a process of thermally decomposing a waste plastic raw material containing polyolefins to obtain a hydrocarbon stream containing olefins. More specifically, the thermal decomposition process is a process of thermally decomposing a waste plastic raw material containing polyolefins to form a pyrolysate, and obtaining a hydrocarbon stream containing olefins from the pyrolysate. The thermal decomposition process includes a reaction of reducing the molecular weight of polymer components contained in the waste plastic raw material and converting them into hydrocarbons. In other words, the hydrocarbon stream obtained in the thermal decomposition process contains hydrocarbons. In the thermal decomposition process, a pyrolysis residue may be generated from the waste plastic raw material.

[0029] The thermal decomposition step can be carried out using the above-mentioned thermal decomposition apparatus, preferably at least one selected from the group consisting of a stirred tank thermal decomposition apparatus, a rotary thermal decomposition apparatus, an internal circulating fluidized bed apparatus, and an external circulating fluidized bed apparatus.

[0030] The waste plastic raw materials refer to plastic products that have been used for some final purpose.

[0031] Examples of polyolefins contained in the waste plastic raw material include olefin-based polymers containing monomer units derived from α-olefins. The olefin-based polymers may be olefin homopolymers or copolymers containing monomer units derived from olefins. The waste plastic raw material may contain, as the olefin-based polymer, at least one of an olefin homopolymer and a copolymer containing monomer units derived from olefins.

[0032] Examples of the monomer derived from olefin include ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-undecene, and 1-dodecene.

[0033] The copolymer containing monomer units derived from an olefin may be a copolymer containing monomer units derived from two or more different olefins, or may be a copolymer containing monomer units derived from an olefin and monomer units other than the monomer units derived from an olefin. The waste plastic raw material may contain, as the olefin-based polymer, one type or two or more types of copolymers containing monomer units derived from an olefin.

[0034] Examples of the monomer other than the olefin-derived monomer unit include alkylene oxides such as ethylene oxide, esters such as ethylene terephthalate, etc. The monomer other than the olefin-derived monomer unit may be alkylene oxide or ethylene terephthalate.

[0035] Examples of copolymers containing monomer units derived from olefins include propylene copolymers containing monomer units derived from propylene. Examples of the propylene copolymers include propylene-ethylene copolymers, propylene-1-butene copolymers, propylene-1-hexene copolymers, propylene-1-octene copolymers, propylene-ethylene-1-butene copolymers, propylene-ethylene-1-hexene copolymers, and propylene-ethylene-1-octene copolymers. The propylene copolymers may be random copolymers or heterophasic propylene polymer materials.

[0036] The waste plastic raw material may contain polymer components other than the polyolefins, such as chlorinated polyethylene, polyvinyl chloride (PVC), polyvinylidene chloride (PVDC), polyethylene terephthalate (PET), polybutylene terephthalate, polystyrene, nylon 66, etc.

[0037] From the viewpoint of increasing the content of polyolefins contained in the waste plastic raw material, the waste plastic raw material may be pre-treated before being supplied to the pyrolysis device. Examples of the pre-treatment include a sorting treatment, a crushing treatment, a cleaning treatment, a drying treatment, a melting treatment, and a dechlorination treatment. The sorting treatment is a treatment for sorting plastics containing polyolefins from the waste plastic raw material. The crushing treatment is a treatment for crushing the sorted plastics. The cleaning treatment is a treatment for cleaning the crushed plastics. The drying treatment is a treatment for drying the cleaned plastics. The melting treatment is a treatment for heating plastics to liquefy them. The dechlorination treatment is a treatment for removing chlorine contained in plastics.

[0038] The content of the polyolefin in the pretreated waste plastic raw material is preferably 80% by mass or more, more preferably 85% by mass or more, and even more preferably 90% by mass or more, relative to 100% by mass of the waste plastic raw material.

[0039] The hydrocarbon stream according to the present embodiment comprises hydrocarbons, and may include oxygen-containing compounds, nitrogen-containing compounds, sulfur-containing compounds, and chlorine-containing compounds.

[0040] Examples of the hydrocarbon include alkanes such as methane, ethane, and propane; olefins such as ethylene, propylene, and butene; diolefins such as butadiene; aromatic hydrocarbons such as benzene, toluene, and xylene; cycloalkanes such as cyclohexane, etc. The hydrocarbon stream contains the olefins as the hydrocarbons.

[0041] Examples of the oxygen-containing compounds include organic compounds having an oxygen functional group such as a carboxyl group, a hydroxyl group, or an ether group, carbon dioxide, and carbon monoxide. Examples of the nitrogen-containing compounds include organic compounds having a nitrogen functional group such as an amino group or an isocyanate group, nitrogen ring compounds, nitric oxide, and nitrogen dioxide. Examples of the sulfur-containing compounds include organic compounds having a sulfur functional group such as a thiol group, a thioether group, or a sulfonyl group, sulfur ring compounds, and hydrogen sulfide. Examples of the chlorine-containing compounds include chlorine-containing alkanes such as methyl chloride and chloroform, and chlorine-containing aromatic compounds.

[0042] In the thermal cracking step, the hydrocarbon stream may be vaporized or liquefied. In the thermal cracking step, the hydrocarbon stream is preferably liquefied. Since the hydrocarbon stream is liquefied in the thermal cracking step, transportation of the hydrocarbon stream is facilitated, so the thermal cracking step and the steps downstream of the thermal cracking step can be carried out at different locations. That is, in the olefin production method according to this embodiment, the thermal cracking step and the steps downstream of the thermal cracking step may be carried out intermittently.

[0043] In the thermal decomposition step, at least a portion of the pyrolysate may be liquefied, and at least a portion of the liquefied pyrolysate may be supplied again to the pyrolysis device.

[0044] The heat source in the thermal decomposition step may be heat generated by burning fuel, heat generated by an electric heater, or heat generated during exhaust gas treatment. Examples of the fuel include gaseous pyrolysates contained in the pyrolysate, natural gas, etc. The thermal decomposition step may be carried out using one type of heat source alone or a combination of two or more types of heat sources.

[0045] In the pyrolysis step, virgin plastic raw materials containing polyolefins may be further pyrolyzed. The virgin plastic raw materials refer to polymers produced by a process including a polymerization step, resin compositions containing the polymers, or plastic products using the polymers or resin compositions, which have not been used for any end use. The polyolefins contained in the virgin plastic raw materials are the same as the polyolefins contained in the waste plastic raw materials.

[0046] In the thermal decomposition step, the temperature at which thermal decomposition is carried out is preferably 350°C or higher and 800°C or lower, more preferably 370°C or higher and 600°C or lower, and even more preferably 380°C or higher and 550°C or lower.

[0047] By setting the temperature of the thermal cracking step within the above range, the yield of the hydrocarbon stream is improved.

[0048] In the thermal decomposition step, the pressure at which thermal decomposition is carried out is preferably atmospheric pressure -50 kPaG or more and atmospheric pressure +50 kPaG or less.

[0049] When the pressure in the thermal decomposition step is within the above range, the thermal decomposition is promoted.

[0050] (Hydrogenation process) The hydrogenation step is a step of hydrogenating the hydrocarbon stream while retaining at least a portion of the olefins to obtain a hydrogenated product.

[0051] The hydrogenation step can be carried out using the above-mentioned hydrogenation apparatus, preferably at least one selected from the group consisting of a fixed-bed reactor, a fluidized-bed reactor, and a slurry-bed reactor.

[0052] The hydrocarbon stream contains the above-described hydrocarbons. In one aspect, the hydrocarbon stream according to this embodiment contains a poisoning substance that reduces the activity of a catalyst used in the crude olefin production step. That is, the hydrogenation step may be a step of hydrogenating the poisoning substance contained in the hydrocarbon stream while leaving at least a portion of the olefins remaining, to obtain a hydrogenated product.

[0053] The poisoning substance may be a substance derived from at least one selected from the group consisting of a nitrogen-containing compound, a sulfur-containing compound, an oxygen-containing compound, and a chlorine-containing compound. That is, the hydrogenation step may be a step of obtaining a hydrogenation product by hydrogenating a substance derived from at least one selected from the group consisting of a nitrogen-containing compound, a sulfur-containing compound, an oxygen-containing compound, and a chlorine-containing compound contained in the hydrocarbon stream while leaving at least a portion of the olefins.

[0054] The nitrogen-containing compound, sulfur-containing compound, oxygen-containing compound, and chlorine-containing compound in the hydrogenation step are the same as those described in the section on the thermal decomposition step.

[0055] The hydrogenation step hydrogenates substances derived from at least one selected from the group consisting of nitrogen-containing compounds, sulfur-containing compounds, oxygen-containing compounds, and chlorine-containing compounds contained in the hydrocarbon stream, thereby making it possible to decompose these substances into ammonia, hydrogen chloride, hydrogen sulfide, water, etc., and to easily remove the poisonous substances from the hydrogenation product supplied to the catalytic cracking unit.

[0056] The hydrogenation step may involve hydrogenating the hydrocarbon stream using a hydrogenation catalyst.

[0057] The hydrogenation catalyst is not particularly limited. Examples of the hydrogenation catalyst include a catalyst containing at least one support selected from the group consisting of alumina, silica, silica-alumina, zeolite, magnesia, and clay, and a metal. The hydrogenation catalyst preferably contains at least one support selected from the group consisting of alumina, silica, silica-alumina, zeolite, magnesia, and clay, and a metal. Examples of the metal include molybdenum, nickel, cobalt, tungsten, palladium, platinum, and copper. The metal is preferably at least one selected from the group consisting of molybdenum, nickel, cobalt, tungsten, palladium, platinum, and copper.

[0058] When the hydrogenation catalyst contains a metal, the content of the metal, calculated as the metal element, is preferably 0.3 mass% or more and 20 mass% or less, more preferably 0.5 mass% or more and 15 mass% or less, and even more preferably 1 mass% or more and 10 mass% or less, relative to 100 mass% of the hydrogenation catalyst.

[0059] By setting the content of the metal within the above range, the hydrocarbon stream can be sufficiently hydrogenated while the olefins are not excessively hydrogenated, and a sufficient amount of the olefins can remain.

[0060] In the hydrogenation step, the hydrogenation catalyst may form a fixed bed, a fluidized bed, or a slurry bed. When the hydrogenation catalyst forms a fixed bed, the fixed bed is formed of the molded hydrogenation catalyst. The molded hydrogenation catalyst may have a spherical, cylindrical, or ring-like shape.

[0061] When the hydrogenation catalyst forms a fixed bed, the outermost diameter of the molded hydrogenation catalyst is preferably 0.5 mm or more and 8 mm or less, more preferably 0.8 mm or more and 5 mm or less. The outermost diameter of the molded hydrogenation catalyst refers to the distance between the most distant positions on the surface of one molded hydrogenation catalyst. When the hydrogenation catalyst forms a fluidized bed or a slurry bed, the particle size of the hydrogenation catalyst is preferably 10 μm or more and 500 μm or less, more preferably 20 μm or more and 200 μm or less.

[0062] In the hydrogenation step, hydrogen is supplied to the hydrogenation device. In the hydrogenation step, hydrogen may be supplied to the hydrogenation device from an external source, or hydrogen obtained in a separation step described below may be supplied.

[0063] In the hydrogenation step, the hydrocarbon stream may be vaporized or liquefied, and in the hydrogenation step, some of the hydrocarbon stream may be vaporized and other hydrocarbon stream may be liquefied.

[0064] In the hydrogenation step, the temperature at which hydrogenation is carried out is preferably 150°C or higher and 300°C or lower, and more preferably 170°C or higher and 250°C or lower.

[0065] The temperature at which hydrogenation is carried out in the hydrogenation unit is 150°C, so that the hydrocarbon stream can be sufficiently hydrogenated.The temperature at which hydrogenation is carried out in the hydrogenation unit is 300°C or less, so that the olefins are not excessively hydrogenated, and a sufficient amount of the olefins can remain.

[0066] In the hydrogenation step, the pressure at which hydrogenation is carried out is preferably 1 MPaG or more and 5 MPaG or less, and more preferably 1.2 MPaG or more and 3 MPaG or less.

[0067] By carrying out hydrogenation in the hydrogenation unit at a pressure of 1 MPaG or more, the hydrocarbon stream can be sufficiently hydrogenated, whereas by carrying out hydrogenation in the hydrogenation unit at a pressure of 5 MPaG or less, the olefins are not excessively hydrogenated, allowing a sufficient amount of the olefins to remain.

[0068] In the hydrogenation step, the ratio of the volume of the hydrogen to the volume of the hydrocarbon stream is preferably 40 or more and 200 or less, more preferably 50 or more and 100 or less. The "volume" of the hydrocarbon stream and the "volume" of the hydrogen are converted into values ​​of "volume at 0°C and 1 atmospheric pressure."

[0069] The hydrocarbon stream can be sufficiently hydrogenated by setting the ratio of the volume of the hydrogen to the volume of the hydrocarbon stream in the hydrogenation unit to 40 or more. The ratio of the volume of the hydrogen to the volume of the hydrocarbon stream in the hydrogenation unit to 200 or less prevents the olefins from being excessively hydrogenated, allowing a sufficient amount of the olefins to remain.

[0070] The liquid hourly space velocity (LHSV) of the hydrocarbon stream in the hydrogenation unit is preferably 0.1 h -1 Over 6 hours -1 More preferably, 0.5 hours or less -1 More than 3 hours -1 The following is the result.

[0071] The liquid hourly space velocity (LHSV) of the hydrocarbon stream in the hydrogenation unit is 6 h -1 The hydrocarbon stream can be sufficiently hydrogenated by the liquid hourly space velocity (LHSV) of the hydrocarbon stream in the hydrogenation unit being 0.1 h or less. -1 By satisfying the above conditions, the olefin is not excessively hydrogenated, and a sufficient amount of the olefin can remain.

[0072] The hydrogenation step is preferably a step in which the hydrocarbon stream is hydrogenated and then further washed with water to obtain the hydrogenated product.

[0073] In the washing with water, water or a basic aqueous solution may be used.

[0074] The content of olefins in the hydrogenation product in the hydrogenation step is preferably 20% by mass or more, more preferably 25% by mass or more and 85% by mass or less, and even more preferably 30% by mass or more and 85% by mass or less.

[0075] The olefin content in the hydrogenation product of the hydrogenation step can be measured by type analysis standardized to JPI-5S-49. In this measurement, hydrocarbon components can be classified and quantified using HPLC into five categories: saturated hydrocarbons, olefins, one-ring aromatic hydrocarbons, two-ring aromatic hydrocarbons, and three- or more-ring aromatic hydrocarbons.

[0076] (Crude olefin production process) The crude olefin production step is a step of obtaining crude olefins from the hydrogenation product using a catalyst containing zeolite. The crude olefin production step may be a step of obtaining crude olefins by supplying the hydrogenation product to a catalytic cracking unit that brings the hydrocarbons in the hydrogenation product into contact with a catalyst containing zeolite to crack the hydrocarbons (also referred to as catalytic cracking). The catalytic cracking includes a reaction of cleaving a carbon-carbon single bond contained in one hydrocarbon molecule to produce two olefin molecules having a carbon-carbon double bond. That is, the crude olefins include olefins produced by catalytic cracking of the hydrocarbons. In the crude olefin production step, the hydrogenation product obtained in the hydrogenation step is supplied to the catalytic cracking unit.

[0077] The crude olefin production step can be carried out using the above-mentioned catalytic cracking unit. The crude olefin production step can be carried out preferably using at least one of a fluidized bed catalytic cracking unit and a moving bed catalytic cracking unit, and more preferably using a fluidized bed catalytic cracking unit.

[0078] The hydrocarbons and the hydrogenation products in the crude olefin production step are the same as those described in the thermal cracking step and the hydrogenation step.

[0079] Examples of catalysts containing zeolite include catalysts containing beta zeolite, faujasite zeolite, L zeolite, ferrierite zeolite, mordenite zeolite, and MFI zeolite. The catalyst containing zeolite is preferably a catalyst containing MFI zeolite. The catalyst containing MFI zeolite has an MFI structure.

[0080] The catalyst containing zeolite is preferably an H-type zeolite having hydrogen cations as acid sites.

[0081] The zeolite-containing catalyst preferably further contains at least one of silica and alumina. The zeolite-containing catalyst may further contain at least one atom selected from the group consisting of titanium, chromium, manganese, iron, cobalt, nickel, copper, ruthenium, rhodium, palladium, silver, iridium, platinum, boron, nitrogen, sodium, potassium, magnesium, phosphorus, zinc, and gallium.

[0082] The amount of acid sites of the catalyst measured by an ammonia temperature programmed desorption method at 250 to 650°C is preferably more than 0 μmol / g and not more than 800 μmol / g. The amount of acid sites of the catalyst measured by an ammonia temperature programmed desorption method at 250 to 650°C may be 5 μmol / g or more, 10 μmol / g or more, 20 μmol / g or more, 30 μmol / g or more, 40 μmol / g or more, or even 50 μmol / g or more. The amount of acid sites of the catalyst measured by an ammonia temperature programmed desorption method at 250 to 650°C may be 700 μmol / g or less, 600 μmol / g or less, 500 μmol / g or less, 400 μmol / g or less, 300 μmol / g or less, 200 μmol / g or less, or 100 μmol / g or less.

[0083] The amount of acid sites in the catalyst can be measured by ammonia temperature programmed desorption spectrometry, for example, using a temperature programmed desorption apparatus TPD-1-Atw (manufactured by Microtrack Bell) according to the following measurement method.

[0084] 50 mg of hydrogenation catalyst was weighed, and helium was passed through it at 50 mL / min for 60 minutes at 500°C. The temperature was then lowered to 250°C, and 0.5% ammonia / helium was passed through it at 100 mL / min for 30 minutes at 250°C to adsorb the ammonia onto the hydrogenation catalyst surface. Helium was then passed through it at 50 mL / min for 30 minutes at 100°C. The catalyst was then heated from 250°C to 650°C at a heating rate of 10°C / min while passing helium through it at 50 mL / min. The amount of ammonia desorbed per unit mass was measured using a quadrupole mass spectrometer. The amount of ammonia desorbed per unit mass was calculated from the area value of the TPD spectrum obtained by the absolute calibration curve method, and this was determined as the number of acid sites per unit mass of the catalyst.

[0085] The amount of acid sites in the catalyst containing the zeolite can be increased by lowering the silica / alumina ratio during the synthesis of the zeolite, and can be decreased by increasing the silica / alumina ratio.

[0086] When the number of acid sites of the catalyst is within the above range, the yield of olefins in the olefin production method is improved.

[0087] The average particle size of the catalyst containing zeolite may be 50 μm or more and 120 μm or less, or 60 μm or more and 90 μm or less.

[0088] The average particle size of a catalyst containing zeolite is determined based on volumetric particle size distribution data measured by laser diffraction in accordance with the method specified in JIS R1629, and refers to the particle size when the cumulative total from the smallest particle size reaches 50% in the particle size distribution data (also referred to as the 50% equivalent particle size). The particle size defined in this way is generally referred to as the "50% equivalent particle size" and is sometimes expressed as "D50."

[0089] When the average particle size of the zeolite-containing catalyst is within the above range, the proportion of unreacted hydrocarbons in the crude olefin production step can be reduced.

[0090] In the crude olefin production step, the catalyst containing zeolite may form a fluidized bed, a moving bed, or a fixed bed.

[0091] In the crude olefin production step, the weight hourly space velocity (WHSV) required for catalytic cracking of the zeolite-containing catalyst is preferably 0.5 h -1 More than 30h -1 More preferably, it is 1 hour or less. -1 Over 15 hours -1 The following is the result.

[0092] By setting the residence time required for catalytic cracking of the zeolite-containing catalyst in the crude olefin production step within the above-mentioned range, the proportion of unreacted hydrocarbons in the crude olefin production step can be reduced.

[0093] The crude olefin comprises an olefin, and preferably comprises an olefin and hydrogen.

[0094] Examples of the olefin contained in the crude olefin include olefins having 2 to 4 carbon atoms. Examples of the olefins having 2 to 4 carbon atoms include ethylene, propylene, 1-butene, 2-butene, and isobutene. The crude olefin according to this embodiment preferably contains at least one of ethylene and propylene.

[0095] The content of olefins in the crude olefins is preferably 50% by mass or more and 85% by mass or less, more preferably 55% by mass or more and 80% by mass or less. From the viewpoint of improving the yield of olefins in the olefin production method, the content of olefins having 2 to 4 carbon atoms in the crude olefins is preferably 45% by mass or more and 80% by mass or less, more preferably 50% by mass or more and 75% by mass or less.

[0096] In the crude olefin production step, the temperature at which catalytic cracking is carried out is preferably 400°C or higher and 800°C or lower, more preferably 450°C or higher and 650°C or lower, and even more preferably 500°C or higher and 600°C or lower.

[0097] When the temperature in the crude olefin production step is within the above range, the olefin yield in the olefin production process is improved.

[0098] (separation process) The separation step is a step of separating olefins having 2 to 4 carbon atoms from the crude olefins. The separation step is preferably a step of further separating hydrogen from the crude olefins. In the separation step, the crude olefins obtained in the crude olefin production step are supplied to the above-mentioned separation device.

[0099] In one aspect of the olefin production method according to the present embodiment, the separation step is a step of further separating hydrogen from the crude olefin, and the hydrogen is used for hydrogenation in the hydrogenation step.

[0100] The crude olefin and the olefin having 2 to 4 carbon atoms in the separation step are the same as those described in the section on the crude olefin production step.

[0101] The separation step can be carried out using the above-mentioned separation apparatus. The separation step can be carried out using one type of separation apparatus or multiple types of separation apparatus. When the separation step is carried out using one type of separation apparatus, the separation step can be preferably carried out using a distillation apparatus. When the separation step is carried out using multiple types of separation apparatus, the separation step can be preferably carried out using at least two types of separation apparatus selected from the group consisting of a distillation apparatus, a gas-liquid separation apparatus, an adsorption separation apparatus, a membrane separation apparatus, and a washing apparatus.

[0102] By carrying out the olefin production method according to this embodiment in the above-described manner, it is possible to suppress a decrease in the olefin yield and reduce catalyst poisoning in catalytic cracking using waste plastic raw materials.

[0103] The olefin production method according to the present embodiment includes a thermal decomposition step of thermally decomposing a waste plastic raw material containing polyolefins to obtain a hydrocarbon stream containing olefins; a hydrogenation step of hydrogenating the hydrocarbon stream while leaving at least a portion of the olefins to obtain a hydrogenated product; a crude olefin production step of obtaining crude olefins from the hydrogenated product using a catalyst containing zeolite; and a separation step of separating olefins having 2 to 4 carbon atoms from the crude olefins.

[0104] With this configuration, the olefin production method can suppress a decrease in the olefin yield by leaving a portion of the olefins contained in the hydrocarbon stream in the hydrogenation step. Furthermore, by hydrogenating the hydrocarbon stream in the hydrogenation step, substances that poison catalysts contained in waste plastics can be decomposed and discharged, thereby reducing catalyst poisoning.

[0105] In the method for producing an olefin, the hydrogenation product in the hydrogenation step has an olefin content of 20 mass % or more.

[0106] In the olefin production method having such a configuration, the olefin content in the hydrogenated product in the hydrogenation step is 20 mass % or more, thereby improving the yield of the olefin as the final product.

[0107] In the olefin production method, the catalyst has an acid site amount of more than 0 μmol / g and 800 μmol / g or less, as measured at 250 to 650° C. by an ammonia temperature programmed desorption method.

[0108] In the olefin production method having such a configuration, the amount of acid sites in the catalyst is within the above-mentioned numerical range, so that the proportion of unreacted hydrogenation products can be reduced, and the yield of olefins as final products can be improved.

[0109] In the olefin production method, the separation step is a step of further separating hydrogen from the crude olefin, and the hydrogen is used for hydrogenation in the hydrogenation step.

[0110] In the olefin production method having such a configuration, the hydrogen separated from the crude olefin in the separation step is used for hydrogenation in the hydrogenation step, and thus the hydrogen source required in the hydrogenation step can be supplemented with the by-product generated in the crude olefin production step, thereby contributing to a reduction in the environmental load.

[0111] In the olefin production method, the hydrogenation step is a step of hydrogenating the hydrocarbon stream and then washing it with water to obtain the hydrogenated product.

[0112] In the olefin production method having such a configuration, by washing the hydrocarbon stream with water after hydrogenating it, substances in the hydrogenated hydrocarbon stream that may poison the catalyst, such as hydrochloric acid, amines, and hydrogen sulfide, can be removed before the crude olefin production step. This reduces catalyst poisoning and maintains catalyst activity, thereby improving the yield of olefins as a final product.

[0113] The present invention includes the following aspects.

[0114] [1] a pyrolysis step of pyrolyzing a waste plastic raw material containing polyolefins to obtain a hydrocarbon stream containing olefins; a hydrogenation step of hydrogenating the hydrocarbon stream while retaining at least a portion of the olefins to obtain a hydrogenated product; a crude olefin production step of obtaining crude olefins from the hydrogenated product using a catalyst containing zeolite; a separation step of separating olefins having 2 to 4 carbon atoms from the crude olefins, A method for producing olefins. [2] The content of olefins in the hydrogenation product in the hydrogenation step is 20% by mass or more. [1] A method for producing an olefin according to the present invention. [3] The amount of acid sites of the catalyst measured by an ammonia temperature programmed desorption method at 250 to 650°C is more than 0 μmol / g and 800 μmol / g or less. The method for producing an olefin according to [1] or [2]. [4] the separation step is a step of further separating hydrogen from the crude olefin; The hydrogen is used for hydrogenation in the hydrogenation step. The method for producing an olefin according to any one of [1] to [3]. [5] The hydrogenation step is a step of hydrogenating the hydrocarbon stream and then washing it with water to obtain the hydrogenated product. The method for producing an olefin according to any one of [1] to [4].

[0115] The olefin production method according to the present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the spirit of the present invention. In addition, the configurations, methods, etc. of the embodiments other than those described above may be arbitrarily adopted and combined.

Claims

1. a pyrolysis step of pyrolyzing a waste plastic raw material containing polyolefins to obtain a hydrocarbon stream containing olefins; a hydrogenation step of hydrogenating the hydrocarbon stream while retaining at least a portion of the olefins to obtain a hydrogenated product; a crude olefin production step of obtaining crude olefins from the hydrogenated product using a catalyst containing zeolite; a separation step of separating olefins having 2 to 4 carbon atoms from the crude olefins, The content of olefins in the hydrogenation product in the hydrogenation step is 20% by mass or more. A method for producing olefins.

2. The amount of acid sites of the catalyst measured by an ammonia temperature programmed desorption method at 250 to 650°C is more than 0 μmol / g and 800 μmol / g or less. The method for producing an olefin according to claim 1.

3. the separation step is a step of further separating hydrogen from the crude olefin; The hydrogen is used for hydrogenation in the hydrogenation step. The method for producing an olefin according to claim 1 or 2.

4. The hydrogenation step is a step of hydrogenating the hydrocarbon stream and then washing it with water to obtain the hydrogenated product. The method for producing an olefin according to claim 1 or 2.