Catalyst for converting pyrolysis products of hydrocarbon-based plastics and method for producing lower hydrocarbons using the same

Abstract

To provide a conversion catalyst for a thermal decomposition product of a hydrocarbon-based plastic, which has a long catalyst life and excellent selectivity and enables efficient conversion of a thermal decomposition product of a hydrocarbon-based plastic into a lower hydrocarbon and the like.SOLUTION: There is provided a conversion catalyst for a thermal decomposition product of a hydrocarbon-based plastic, which includes a zeolite that satisfies the following characteristics (i) to (iii): (i) has an average particle size of 100 nm or less; (ii) is a 10-membered fine pore zeolite of a MFI type or a MEL type; and (iii) has a Broensted acid amount of 0.1-10.0 μmol / g on an external surface.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a catalyst for converting pyrolysis products of hydrocarbon-based plastics that enables the conversion of pyrolysis products of hydrocarbon-based plastics into useful substances, and in particular to a catalyst for converting aliphatic hydrocarbons, such as paraffins, olefins, and diolefins having 1 to 30 carbon atoms (hereinafter sometimes referred to as C), which are the main components of the pyrolysis products of hydrocarbon-based plastics, into olefins, paraffins, aromatic hydrocarbons, and the like having 2 to 8 carbon atoms that are useful as petrochemical products, in a highly efficient, well-balanced and stable manner, and to a method for producing lower hydrocarbons using the catalyst. [Background technology]

[0002] In recent years, issues such as global warming and marine plastic pollution have come into sharp focus, and chemical recycling, which involves chemically breaking down waste plastics and reusing them as raw materials for petrochemical products, has been attracting attention. Among these, oil-to-plastic technology using thermal decomposition is an important technology that essentially enables the recycling of plastics by converting thermoplastic polyolefins (polyethylene, polypropylene), which account for half of waste plastics, into hydrocarbon oil, which can then be used as raw material for naphtha crackers, etc.

[0003] The technology of converting waste plastics into oil through thermal decomposition has been known for a long time, and when thermal decomposition is carried out under oxygen-free and catalyst-free conditions, a wide range of carbon number distribution products, i.e. hydrocarbon oils, is obtained, from the C5 to C10 light oils, which can be used as feedstock for naphtha crackers, but kerosene, diesel, heavy oil, and waxes with C11 or more are used as fuel and do not add much value to the product.

[0004] As a method for increasing the added value of products, a method has been proposed in which polyolefin-based (waste) plastics are thermally decomposed and the products generated by the thermal decomposition are brought into contact with a catalyst layer such as zeolite to recover hydrocarbon oils (see, for example, Patent Document 1 and Non-Patent Document 1).

[0005] In addition, a method for treating waste plastics has been proposed in which waste plastics are vaporized by pyrolysis, and the resulting pyrolysis product is brought into contact with a boron-containing silicate catalyst to recover hydrocarbon oil (see, for example, Patent Document 2).Furthermore, a method for treating waste plastics using a gallium-containing silicate catalyst (see, for example, Patent Document 3) has also been proposed. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 178195 / 1983 [Patent Document 2] Patent No. 4341162 [Patent Document 3] Patent No. 4103198 [Non-patent literature]

[0007] [Non-Patent Document 1] Polymer, Vol. 45, p. 311 (1996) Summary of the Invention [Problem to be solved by the invention]

[0008] However, in the method proposed in Patent Document 1, although the carbon number distribution of hydrocarbon oils is lowered from C5-C38 to C5-C21 by using a ZSM-5 catalyst, there is still a problem that there is a large amount of low-value-added kerosene, light oil, and heavy oil fractions of C11 and above.In the method proposed in Non-Patent Document 1, thermal cracking is carried out using HY, REY, and Ni / ReY catalysts in addition to ZSM-5, and selectivity to C5-C11 gasoline fractions is particularly high when an REY catalyst is used, but these Y-type zeolites have poor thermal stability and still produce a large amount of low-value-added fractions of C9 and above, so they are not sufficient as industrial catalysts.

[0009] In the method proposed in Patent Document 2, the use of a boron-containing silicate catalyst significantly reduced the molecular weight of hydrocarbon oils, and in particular increased the total selectivity for C3 and C4 olefins and paraffins. However, the production of biased components made it difficult to use in conjunction with existing plants. For example, the load on a specific distillation column in an ethylene plant (naphtha cracker) increased, forcing the naphtha cracker's operating rate to be excessively reduced, or requiring the construction of a new specific distillation column, making the method economically unreasonable. In addition, the synthesis of boron-containing silicates is difficult, making them difficult to obtain, and their coking resistance is insufficient, so satisfactory consideration has not been given to catalyst life. Furthermore, in the method proposed in Patent Document 3, the use of a gallium-containing silicate catalyst increases the selectivity for carbon number distributions of C1 to C13, particularly benzene (C6), toluene (C7), and xylene (C8), and the reduction in molecular weight proceeds in a well-balanced manner. However, with gallium-containing silicates, particularly gallosilicates, it is difficult to insert Ga metal into the silicate framework, making them difficult to synthesize reproducibly and industrially. In addition, the coking resistance is insufficient, so there is still room for improvement in terms of catalyst life.

[0010] Therefore, there has been a demand for a catalyst for converting the pyrolysis products of hydrocarbon plastics that can be converted with high efficiency into C2 to C8 hydrocarbons and other substances that are useful as petrochemical products, as well as a method for producing lower hydrocarbons using the catalyst. [Means for solving the problem]

[0011] As a result of intensive research to solve the above problems, the present inventors have found that a conversion catalyst containing a specific 10-membered ring pore zeolite has excellent coking resistance and catalyst life when using pyrolysis products of hydrocarbon-based plastics as raw materials, and also has improved selectivity for paraffins, olefins, and aromatic hydrocarbons with 2 to 8 carbon atoms, which are useful as petrochemical products, resulting in a catalyst that exhibits excellent performance, and have completed the present invention.

[0012] That is, the present invention relates to a conversion catalyst for pyrolysis products of hydrocarbon-based plastics, characterized in that the conversion catalyst contains a zeolite that satisfies the following characteristics (i) to (iii), and to a method for producing lower hydrocarbons using the same. (i) The average particle size is 100 nm or less. (ii) MFI-type or MEL-type 10-ring pore zeolites. (iii) The Bronsted acid content of the outer surface is 0.1 to 10.0 μmol / g.

[0013] The present invention will be described in detail below.

[0014] The pyrolysis product conversion catalyst of the present invention is a catalyst that enables highly selective conversion of pyrolysis products of hydrocarbon-based plastics, which have traditionally been difficult to use as raw materials due to the wide variety of components they contain, into lower hydrocarbons useful as petrochemical products, particularly lower hydrocarbons such as olefins, paraffins, and aromatic hydrocarbons having 2 to 8 carbon atoms. The catalyst contains a zeolite that satisfies all of the following requirements: (i) an average particle diameter (hereinafter sometimes abbreviated as PD) of PD≦100 nm, (ii) a 10-membered ring pore zeolite of the MFI or MEL type, and (iii) a Bronsted acid site density on the outer surface of 0.1 to 10.0 μmol / g.

[0015] The zeolite constituting the pyrolysis product conversion catalyst of the present invention has (i) a PD≦100 nm, and since it is a catalyst with particularly excellent thermal stability, it is desirable that the PD is 5 nm≦PD≦100 nm. However, if the PD exceeds 100 nm, the efficiency of converting the pyrolysis products of hydrocarbon-based plastics into lower hydrocarbons will be poor.

[0016] The PD in the present invention may be measured by any method without any limitation, and examples thereof include a method of selecting 100 or more particles from a photograph taken with a scanning electron microscope (SEM) or a transmission electron microscope (TEM) and determining their average diameter, and a method of calculating the PD from the external surface area of the zeolite using the following formula (1). PD=6 / S×(1 / (2.29×10 6 ) + 0.18 × 10 -6 ) (1) (where S is the external surface area (m 2 / g) In addition, the external surface area (S(m 2 / g) can be determined by the t-plot method using a general nitrogen adsorption method at liquid nitrogen temperature. For example, when t is the thickness of the adsorption amount, measurement points in the range of 0.6 to 1 nm for t are linearly approximated, and the external surface area of the zeolite is determined from the slope of the resulting regression line.

[0017] Among these, the method using SEM or TEM is preferred because it allows simple measurement.

[0018] The zeolite constituting the pyrolysis product conversion catalyst of the present invention is (ii) an MFI or MEL 10-ring pore zeolite. Examples of MFI zeolites include aluminosilicate compounds that fall under the structure code MFI defined by the International Zeolite Association. Zeolites other than MFI or MEL 10-ring pore zeolites are less efficient in the conversion reaction of pyrolysis products of hydrocarbon plastics.

[0019] The zeolite constituting the pyrolysis product conversion catalyst of the present invention (iii) has an outer surface Brønsted acid amount (hereinafter sometimes referred to as B acid amount) of 0.1 to 10.0 μmol / g, and by having an outer surface B acid amount within a specific range, it exhibits particularly excellent catalytic performance. Here, if the outer surface B acid amount is less than 0.1 μmol / g, the production efficiency and catalytic performance when converting the pyrolysis products of hydrocarbon-based plastics will be poor. On the other hand, if it is more than 10.0 μmol / g, side reactions and coking will easily occur on the catalyst surface, resulting in insufficient catalytic performance.

[0020] The zeolite constituting the pyrolysis product conversion catalyst of the present invention is a catalyst that is excellent in conversion efficiency of pyrolysis products of hydrocarbon-based plastics, particularly in selectivity to lower hydrocarbons such as olefins, paraffins, and aromatic hydrocarbons having 2 to 8 carbon atoms. Therefore, (iv) the amount of B acid is preferably 0.01 to 1.0 mmol / g, and more preferably 0.1 to 1.0 mmol / g.

[0021] Here, the B acid amount of a zeolite indicates the amount of Bronsted acid sites (hereinafter sometimes referred to as B acid sites), and indicates the acidic OH groups present in the zeolite. Usually, a zeolite has B acid sites on its outer surface and in its (micro)pores. And, when a zeolite has only a few B acid sites on its outer surface, it means that most of the B acid sites are present in the (micro)pores.

[0022] The amount of B acid on the outer surface of the zeolite can be confirmed by any method that allows such confirmation. For example, it can be confirmed by adsorption of 2,4-dimethylquinoline, which has adsorption properties for B acid sites. 2,4-Dimethylquinoline has the ability to adsorb to B acid sites (acidic OH groups) present in zeolite (including within the pores). However, when the (micro)pore diameter of the zeolite is smaller than that of the 2,4-dimethylquinoline molecule, as in the case of MFI-type zeolite, 2,4-dimethylquinoline cannot penetrate the (micro)pores and cannot adsorb to the B acid sites within the (micro)pores. In other words, it only adsorbs to the B acid sites on the outer surface of the zeolite. Therefore, the amount of B acid on the outer surface can be quantified by determining the amount of 2,4-dimethylquinoline adsorbed to the B acid sites on the outer surface of MFI-type zeolite.

[0023] More specifically, the infrared absorption spectrum of zeolite is measured at 150°C after degassing and dehydration for 2 hours at 400°C as a pretreatment. 2,4-dimethylquinoline gas is then introduced into the degassed and dehydrated zeolite, adsorbed for 30 minutes, and the excess 2,4-dimethylquinoline is removed by evacuation at 150°C to prepare 2,4-dimethylquinoline-adsorbed zeolite, followed by infrared absorption spectrum measurement at 150°C. In other words, the difference spectrum of infrared absorption before and after 2,4-dimethylquinoline adsorption shows a peak at 3600-3650 cm. -1 The amount of B acid on the outer surface can be obtained by quantifying the difference (decrease) in infrared absorption in the range of 3700 to 3800 cm. 2,4-Dimethylquinoline also adsorbs to the silanol sites on the zeolite surface, but the absorption due to the OH stretching vibration of silanol is in the range of 3700 to 3800 cm. -1 On the other hand, absorption due to the OH stretching vibration of the B acid site on the outer surface of the zeolite is observed at 3600–3650 cm -1 The absorption peak at 3600-3650 cm originates from the OH stretching vibration of the acid site B due to the adsorption of 2,4-dimethylquinoline. -1 The decrease in the infrared absorption spectrum in the range of 2,4-dimethylquinoline indicates that 2,4-dimethylquinoline is adsorbed onto the B acid sites on the outer surface of the zeolite.

[0024] Furthermore, the amount of B acid in the zeolite (the amount of B acid sites present on the outer surface and in the (micro)pores) can be measured by any method that allows such measurement. For example, it can be confirmed by adsorption of pyridine, which has an adsorbability to B acid sites. Pyridine has an adsorbability to B acid sites (acidic OH groups) present in the zeolite (including in the pores), and when the (micro)pore diameter of the zeolite is larger than that of pyridine, it can penetrate into the (micro)pores and adsorb to the B acid sites on the outer surface and in the (micro)pores. Therefore, it is possible to quantify the amount of all B acid present in the zeolite, including the B acid sites present in the pores of MFI zeolite.

[0025] More specifically, the infrared absorption spectrum of zeolite is measured at 150°C after degassing and dehydration for 2 hours at 400°C as a pretreatment. Pyridine gas is then introduced into the degassed and dehydrated zeolite and adsorbed for 10 minutes. Excess pyridine is then removed by evacuation at 150°C to prepare pyridine-adsorbed zeolite, and the infrared absorption spectrum is measured at 150°C. In other words, in the difference spectrum of infrared absorption before and after pyridine adsorption, a peak at 1515-1565 cm is observed. -1 By quantifying the difference (decrease) in infrared absorption within this range, the amount of B acid, including that within the pores, can be obtained.

[0026] The zeolite constituting the pyrolysis product conversion catalyst of the present invention is a catalyst that is particularly excellent in conversion efficiency of pyrolysis products of hydrocarbon-based plastics and selectivity to olefins, paraffins, and aromatic hydrocarbons having 2 to 8 carbon atoms. Therefore, it is preferable that the zeolite has a small number of B acid sites on its outer surface, with most of the B acid sites being present within (micro)pores. The B acid sites present on the outer surface preferably account for 1 to 10% of all B acid sites. The proportion of B acid sites on the outer surface is calculated by dividing the amount of B acid on the outer surface of the zeolite by the amount of B acid present in the zeolite (including within the pores).

[0027] Any method can be used to produce the zeolite as long as it can produce a zeolite that satisfies the above characteristics (i) to (iii). A method for selectively removing B acid sites from the zeolite surface, i.e., a method for producing a zeolite that satisfies the characteristics (i) to (ii), in which part or all of the calcination treatment (heat treatment) is performed using hydrothermal (steam) treatment, can be used, and an ion exchange treatment can be added before or after the calcination treatment.

[0028] Zeolites satisfying the characteristics (i) and (ii) can be synthesized using commonly known methods to obtain zeolites having a PD≦100 nm and a framework structure of MFI or MEL 10-membered ring pores. Specifically, zeolites can be produced by mixing a compound containing an alkali metal and / or alkaline earth metal as a cation, an organic structure-directing agent, and an aluminosilicate gel, and then calcining the resulting crystals. Examples of the alkali metal or alkaline earth metal-containing compound include sodium hydroxide, potassium hydroxide, calcium hydroxide, and magnesium hydroxide, with sodium hydroxide being preferred. Examples of the organic structure-directing agent include tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, and tetraethylammonium hydroxide. Examples of the aluminosilicate gel include amorphous aluminosilicate gel.

[0029] Furthermore, when obtaining a zeolite that satisfies the characteristics (i) to (iii), it is possible to produce the zeolite by a method in which ion exchange is performed before calcining the crystalline product obtained as described above, and part or all of the calcination is performed as a hydrothermal treatment, followed by further ion exchange; or a method in which ion exchange is performed after calcining the crystalline product obtained as described above to obtain a proton-type zeolite, followed by calcining in a hydrothermal atmosphere.

[0030] As for the calcination conditions, the treatment temperature is preferably 300 to 900°C, and particularly preferably 400 to 700°C. The treatment time is preferably 5 minutes to 25 hours from an industrial perspective. The atmosphere can be, for example, nitrogen, air, oxygen, argon, or a combination of two or more of other inert gases. A hydrothermal (steam) treatment is carried out in part or all of the calcination step, thereby eliminating aluminum from the B acid site. The treatment temperature for the hydrothermal treatment is preferably 400 to 750°C, and particularly preferably 500 to 650°C. The steam concentration is preferably 5 to 100%, and particularly preferably 10 to 80%.

[0031] Ion exchange is carried out before or after the calcination step, and may be divided into multiple ion exchanges. Examples of ion exchange include ion exchange using an acid such as ammonium chloride, hydrochloric acid, or nitric acid, with hydrochloric acid and nitric acid being preferred. Ion exchange can also be substituted by washing with water.

[0032] The zeolite constituting the pyrolysis product conversion catalyst of the present invention exhibits high catalytic performance as it is, but to further improve coking resistance and catalyst life, it may contain (v) at least one metal selected from sodium, potassium, calcium, silver, and zinc, and metal-containing zeolites with a content of 0.05 to 5.0 wt% are preferred. Of these metals, zinc- and / or calcium-containing zeolites are more preferred because they enhance selectivity to olefins, paraffins, and aromatic hydrocarbons having 2 to 8 carbon atoms. Furthermore, the method for incorporating the metal is not limited, and any of methods such as impregnation, ion exchange, physical mixing, and vapor deposition are possible.

[0033] When used as a catalyst for converting pyrolysis products, it is preferable to shape the zeolite into a molded body, as this will result in a catalyst with excellent handleability and catalytic performance. Any molding method can be used for shaping, including a method of directly molding the zeolite powder into a predetermined shape by compression molding or the like, a method of mixing the zeolite with a predetermined proportion of a binder, optionally with additional additives in predetermined proportions, and molding the mixture into a predetermined shape, or a method of sintering the mixture to form a molded body. Particularly when used as a catalyst for converting pyrolysis products of hydrocarbon plastics, a molded body consisting of the zeolite and a binder is preferred because it not only has excellent moldability as a molded body but also exhibits high crushing strength, ease of handling, and excellent catalyst life. A molded body consisting of the zeolite and silica is even more preferred because it will result in better catalytic performance. The silica used in this case may be any type that falls within the category known as silica, and may have a specific crystal structure or may be amorphous. Furthermore, there are no limitations on the particle size or aggregate size of the silica. The blending ratio of the zeolite and silica is optional, and in particular, a weight ratio of the zeolite:silica of 50-95:50-5 is preferred, and a weight ratio of 60-90:40-10 is particularly preferred, as this results in a conversion catalyst that exhibits particularly excellent catalytic performance, ease of handling, and catalyst life.

[0034] The thermal cracking product conversion catalyst may have any shape, such as a cylindrical shape, a polygonal prism (e.g., triangular prism, square prism, pentagonal prism, hexagonal prism), a hollow polygonal prism, or a spherical shape. Among these, a cylindrical shape is preferred because it provides a catalyst with excellent continuous productivity and high crushing strength. Furthermore, its size (e.g., diameter, width, length) and density (e.g., bulk density, true density) can be selected as desired, taking into consideration factors such as packing efficiency. A cylindrical shape with a diameter of 1.0 to 10 mm or a thickness of 0.5 to 5.0 mm is preferred because it provides a catalyst that can effectively produce olefins, paraffins, aromatic hydrocarbons, and other compounds having 2 to 8 carbon atoms, which are particularly useful as petrochemical products.

[0035] The pyrolysis product conversion catalyst of the present invention enables highly selective production of hydrocarbons, particularly lower hydrocarbons useful as petrochemical products, i.e., olefins, paraffins, and aromatic hydrocarbons having 2 to 8 carbon atoms, by contacting hydrocarbons, which are pyrolysis products of hydrocarbon-based plastics, as a raw material. The pyrolysis products of hydrocarbon-based plastics used as the raw material are not limited as long as they are obtained by pyrolysis of hydrocarbon-based plastics. Among these, hydrocarbon-based plastics that exhibit thermoplasticity and do not contain oxygen or nitrogen atoms in their structure, as well as pyrolysis products of used waste plastics and / or waste products during the production and processing of hydrocarbon-based plastics, are preferred, since recycling plastic waste as a resource can contribute to solving social issues in both resource conservation and waste disposal. Examples of hydrocarbon-based plastics include polyethylene, polypropylene, ethylene-propylene rubber, and polystyrene. Further examples include vinyl chloride resin, vinylidene chloride resin, and chlorinated polyethylene, which are chlorinated plastics from which the chlorine atoms have been separated and removed.

[0036] The pyrolysis products of hydrocarbon-based plastics are not particularly limited as long as they are hydrocarbons produced by the thermal decomposition of hydrocarbon-based plastics, and examples thereof include products obtained by melting polyolefins such as polyethylene and polypropylene under oxygen-free and catalyst-free conditions and then thermally decomposing the molten material.The pyrolysis products of hydrocarbon-based plastics are generally mixtures of aliphatic hydrocarbons consisting of paraffins, olefins, and diolefins with carbon numbers ranging from C1 to C30, and the mixing ratios thereof can be appropriately selected depending on the hydrocarbon-based plastic, the thermal decomposition conditions, etc.

[0037] The pyrolysis product conversion catalyst of the present invention, when contacted with the pyrolysis products of hydrocarbon-based plastics, can produce lower hydrocarbons, particularly olefins, paraffins, and aromatic hydrocarbons having 2 to 8 carbon atoms, with high selectivity. The reaction temperature is not particularly limited, but is preferably in the range of 350 to 650°C, which results in a more efficient production method, and more preferably in the range of 500 to 600°C, which increases the selectivity of useful components. There is also no limitation on the reaction pressure, and operation is possible within a pressure range of, for example, about 0.05 MPa to 5 MPa. The supply of pyrolysis products is not particularly limited as a ratio of the volume of the raw pyrolysis product gas to the volume of the catalyst, and can be, for example, 1 h -1 ~50,000h -1 In this case, the gas may be diluted with a single or mixed gas selected from an inert gas such as nitrogen, hydrogen, carbon monoxide, and carbon dioxide.

[0038] The lower hydrocarbons produced using the thermal cracking product conversion catalyst of the present invention are preferably olefins, paraffins, and aromatic hydrocarbons having 2 to 8 carbon atoms, and examples thereof include paraffins such as ethane, propane, butane, pentane, hexane, heptane, and octane; olefins such as ethylene, propylene, butene, pentene, hexene, heptene, and octene; and benzene, toluene, xylene, trimethylbenzene, ethylbenzene, and ethyltoluene.

[0039] The pyrolysis product conversion catalyst of the present invention efficiently reduces the molecular weight of pyrolysis products of hydrocarbon-based plastics and promotes cyclodehydrogenation, enabling the highly selective production of lower hydrocarbons useful as petrochemical products, i.e., C2-8 olefins, paraffins, and aromatic hydrocarbons, with selectivity of 60% or more. Furthermore, because the components of C2-8 olefins, paraffins, and aromatic hydrocarbons are produced in a well-balanced manner, efficient combined operation with an existing plant is possible without the need for new distillation columns. Specifically, the distillation columns for each component in the ethylene plant can be fully utilized, enabling efficient operation of the ethylene plant without excessively reducing the operating rate of the naphtha cracker.

[0040] Although the pyrolysis product conversion catalyst of the present invention is excellent in selectivity, efficiency, catalyst life, and coking resistance, in the production of lower hydrocarbons using pyrolysis products of hydrocarbon-based plastics as raw materials, coke forms on the catalyst as the catalytic reaction proceeds, and the coke deposition inevitably reduces catalytic performance. While there are no particular limitations on the method for regenerating a catalyst with reduced catalytic performance, for example, combustion removal with oxygen is preferred. Coke deposited on the pyrolysis product conversion catalyst of the present invention can be efficiently removed by contacting the catalyst with a gas containing 2 to 25% by weight of oxygen at 380 to 530°C, thereby restoring catalytic performance. Contact with a gas containing 5 to 25% by weight of oxygen at 400 to 450°C is particularly preferred due to its excellent regeneration efficiency.

[0041] Examples of gases having an oxygen content of 2 to 25% by weight include those prepared by mixing air or oxygen with an inert gas such as nitrogen, argon, neon, etc. The amount of gas supplied and the regeneration time during regeneration are not particularly limited as long as the catalyst can be regenerated, and in particular, because this allows for efficient removal of coke deposited on the pyrolysis product conversion catalyst of the present invention, it is preferable to supply the gas under conditions of gas volume / catalyst volume = 200 to 700 per hour, and the regeneration time is preferably 30 to 65 hours. [Effects of the Invention]

[0042] The thermal decomposition product conversion catalyst of the present invention has high coking resistance and a long catalyst life, even when using thermal decomposition products of hydrocarbon-based plastics, and therefore enables stable, long-term production of paraffins, olefins, and aromatic hydrocarbons having 2 to 8 carbon atoms, which are useful as petrochemical products, with high selectivity. Therefore, it is expected to be industrially useful. [Example]

[0043] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0044] The 10-membered ring pore zeolite used in the examples and comparative examples was prepared in accordance with Japanese Patent No. 6070336. The zeolite and the catalyst for converting pyrolysis products were evaluated and measured by the following methods.

[0045] ~Measuring average particle size~ The average particle size was measured using a transmission electron microscope (hereinafter sometimes referred to as TEM) and a scanning electron microscope (hereinafter sometimes referred to as SEM). TEM was performed using a transmission electron microscope (JEOL Ltd., (trade name) JEM-2100, accelerating voltage 200 kV, observation magnification 30,000 times). A sample was lightly crushed in a mortar, ultrasonically dispersed in acetone, dropped onto a plastic support film, and air-dried to prepare a microscopic sample. Photographs were taken of the sample. For each primary particle in the photograph, the longest diameter and the average diameter in the perpendicular direction at its midpoint were measured, and the average of a total of 300 particles was used as the average particle size.

[0046] For SEM, a scanning electron microscope (Keyence Corporation, product name VE-9800, accelerating voltage 20 kV, observation magnification 2000x) was used, and a sample lightly crushed in a mortar was placed on a sample stage, gold was vapor-deposited on it, and a photograph was taken. The side length of 150 particles in the photograph was measured, and the average value was taken as the average crystal diameter.

[0047] ~2,4-Dimethylquinoline Adsorption Infrared Absorption Spectroscopy Measurement (Amount of Acid on the Outer Surface)~ Infrared absorption spectroscopy was measured by the transmission method using an FT-IR measurement device (product name FT / IR-6700, manufactured by JASCO Corporation). An MCT detector was used to obtain a spectrum with 256 integrations. The sample was molded into a 13 mm diameter disk and then placed in a disk holder inside a quartz vacuum degassing cell, thereby being positioned perpendicular to the infrared light path. As a pretreatment for the sample, the temperature was raised to 400°C at 10°C / min under vacuum and maintained at that temperature for 2 hours. After cooling to 150°C, the infrared absorption spectrum before 2,4-dimethylquinoline adsorption was measured. 2,4-dimethylquinoline gas was introduced and allowed to adsorb for 30 minutes. After vacuum evacuation at 150°C for 1 hour, the infrared absorption spectrum after 2,4-dimethylquinoline adsorption was measured. The difference between the infrared absorption spectrum after 2,4-dimethylquinoline adsorption and the spectrum before adsorption was calculated, and the change in infrared absorption due to adsorption was measured. The difference spectrum at 3600 cm -1 The peak around this point is the peak of the absorption spectrum of 2,4-dimethylquinoline adsorbed on the Brønsted acid. After determining this area intensity, the amount of outer surface B acid was calculated using the Lambert-Behr law according to the following formula (2). Amount of B acid (μmol / mg)=A S / (W ε) (2) (where A is the peak area intensity of the peak of interest (cm -1 ), S; sample cross-sectional area (cm 2 ), W: sample weight (mg), ε: integrated extinction coefficient, 3.7 cm μmol -1 , respectively.) ~Pyridine adsorption infrared absorption spectroscopy measurement (total B acid amount)~ The same apparatus and method were used in the above 2,4-dimethylquinoline adsorption infrared absorption spectroscopy measurement, except that pyridine gas was introduced and allowed to adsorb for 10 minutes.

[0048] However, the difference spectrum at 1545 cm -1 The peak in the vicinity was used as the peak of the absorption spectrum of pyridine adsorbed on the Brønsted acid, and the integrated extinction coefficient was calculated to be 1.67 cm μmol -1The total amount of B acid was calculated using the above formula (2).

[0049] ~Outer surface B acid rate~ The ratio of the amount of outer surface B acid divided by the total amount of B acid was defined as the outer surface B acid ratio.

[0050] ~Powder X-ray diffraction measurement~ Measurements were taken in air using an X-ray diffraction measurement device (Spectris, product name: X'pert PRO MPD) with a tube voltage of 45 kV and a tube current of 40 mA using CuKα1. The range of 0.04 to 5 degrees was analyzed at 0.08 degree / step and 200 seconds / step. The background, corrected for the absorption rate of the direct beam, was also removed.

[0051] The crystal structure was identified by visually checking for the presence or absence of peaks. Alternatively, a peak search program can be used. Any common peak search program can be used. For example, if the measurement results, with the horizontal axis being 2θ (degrees) and the vertical axis being intensity (au), are smoothed using the Savitsky & Golay equation and a sliding polynomial filter, and then the second derivative is taken, a peak can be determined to exist if three or more consecutive negative values are found.

[0052] ~Measurement of SiO2 / Al2O3 molar ratio and metal introduction amount~ The SiO2 / Al2O3 molar ratio of the zeolite and the amount of transition metal incorporated were determined by dissolving the zeolite in a mixed aqueous solution of hydrofluoric acid and nitric acid and measuring it by inductively coupled plasma atomic emission spectroscopy (ICP-AES) using an ICP apparatus (product name OPTIMA3300DV, manufactured by PerkinElmer).

[0053] ~Production equipment for lower hydrocarbons and its production method~ Using the catalysts obtained in the Examples and Comparative Examples, lower hydrocarbons were produced by the following method, and their performance as catalysts for converting pyrolysis products of hydrocarbon plastics was evaluated.

[0054] The lower hydrocarbon production equipment used consisted of a stainless steel autoclave (internal volume 200 ml) for melting and thermally decomposing hydrocarbon plastics, and a fixed-bed gas-phase flow reactor with a stainless steel reaction tube (inner diameter 16 mm, length 600 mm) for converting the pyrolysis products into lower hydrocarbons. The stainless steel reaction tube was packed with a molded catalyst body in the middle section, and a heat pretreatment was carried out at 530°C under a dry air flow.

[0055] High-density polyethylene (HDPE), which was discarded during the production process of a low-pressure polyethylene manufacturing facility, was placed in a stainless steel autoclave and purged with nitrogen. The temperature was slowly raised to 180°C to melt the HDPE, and then raised to 450°C under a nitrogen gas flow (40 ml / min) to perform thermal decomposition, producing a hydrocarbon mixture called a pyrolysis product. The pyrolysis product was fed into a stainless steel reaction tube using nitrogen gas, where it came into contact with a pyrolysis product conversion catalyst and reacted. The temperature of the catalyst (molded body) layer was controlled using a ceramic tubular furnace.

[0056] The reaction outlet gas and reaction liquid were collected and analyzed separately using a gas chromatograph. The gas components were analyzed using a gas chromatograph (Shimadzu Corporation, product name: GC-1700) equipped with a TCD detector and a packing material (Waters, product name: PorapakQ or GL Sciences, product name: MS-5A). The liquid components were analyzed using a gas chromatograph (Shimadzu Corporation, product name: GC-2015) equipped with an FID detector and a capillary column (GL Sciences, product name: TC-1) as a separation column.

[0057] The reaction conditions were set as follows:

[0058] (Catalytic reaction conditions for producing lower hydrocarbons) Catalyst weight: 3.8g. Flow gas: Nitrogen 40ml / min. Reaction temperature: 530°C or 585°C. Response time: 24 hours.

[0059] ~Catalyst activity testing method as an indicator of catalyst life~ After the performance evaluation of the catalyst for converting pyrolysis products from hydrocarbon plastics in the above-mentioned lower hydrocarbon production equipment was completed, the stainless steel autoclave was separated from the stainless steel reactor tube, and the activity of the catalyst for converting pyrolysis products packed in the stainless steel reactor tube was tested using the following C4 fraction. The conversion rate of the C4 fraction one hour after the start of the reaction was used as an index of catalyst life.

[0060] (Catalytic reaction conditions in catalytic activity testing) C4 fraction: isobutane 2 Nml / min, normal butane 5 Nml / min, trans-2-butene 8 Nml / min, 1-butene 15 Nml / min, isobutene 3 Nml / min, propane 7 Nml / min, propylene 2 Nml / min Dilution gas: Nitrogen 42 Nml / min. Reaction temperature: 530°C. Reaction time: 1 hour.

[0061] Example 1 Amorphous aluminosilicate gel was added to an aqueous solution of tetrapropylammonium hydroxide and sodium hydroxide and suspended. MFI type zeolite was added as seed crystals to the resulting suspension to prepare a raw material composition. The amount of seed crystals added was 0.7 wt% relative to the weight of Al2O3 and SiO2 in the raw material composition. The composition of the raw material composition is as follows: SiO2 / Al2O3 molar ratio = 48, TPA / Si molar ratio = 0.05, Na / Si molar ratio = 0.16, OH / Si molar ratio = 0.21, H2O / Si molar ratio = 10.

[0062] The obtained raw material composition was sealed in a stainless steel autoclave and crystallized for 4 days while stirring at 115°C to obtain a slurry mixture. After crystallization, the slurry mixture was subjected to solid-liquid separation using a centrifugal settler, and the solid particles were washed with a sufficient amount of pure water and dried at 110°C to obtain a dry powder.

[0063] The resulting dry powder was dispersed in 1 mol / L hydrochloric acid at room temperature, filtered, and then the solid particles were washed with a sufficient amount of pure water. After filtering again, the solid particles were dried overnight at 100°C. After calcining in air at 550°C for 1 hour, the powder was treated with 30% water vapor at 600°C for 2 hours.

[0064] The obtained powder was dispersed in 1 mol / L hydrochloric acid at room temperature, filtered, and then the solid particles were washed with a sufficient amount of pure water and filtered again to obtain zeolite.

[0065] The physical properties of the obtained zeolite are shown in Table 1. The zeolite was a 10-ring pore zeolite having an MFI-type zeolite framework structure, and the average particle size measured using TEM was 25 nm.

[0066] 25 parts by weight of silica (manufactured by Nissan Chemical Industries, Ltd., product name Snowtex N-30G), 5 parts by weight of cellulose, and 40 parts by weight of pure water were added to 100 parts by weight of the zeolite prepared above and kneaded. The kneaded mixture was then formed into a cylindrical molded body with a diameter of 1.5 mm and a length of 1.0 to 7.0 mm (average length 3.5 mm). This was dried overnight at 100°C. The dried molded body was calcined in an air stream at 600°C for 2 hours to obtain a molded body, which was used as a catalyst for converting pyrolysis products of hydrocarbon plastics.

[0067] Using the obtained catalyst for converting pyrolysis products of hydrocarbon-based plastics, lower hydrocarbons were produced at a temperature of 585°C, and the catalytic reaction was evaluated. The results are shown in Table 1. Useful components such as olefins, paraffins, and aromatic hydrocarbons with carbon numbers of 2 to 8 were obtained with high selectivity. Furthermore, high catalytic performance was maintained even after the reaction was completed, enabling stable production and also exhibiting excellent coking resistance.

[0068] Example 2 The zeolite crystallization in an autoclave, washing, and drying operations were carried out in the same manner as in Example 1. The obtained dry powder was dispersed in 1 mol / L hydrochloric acid at room temperature and filtered, after which the solid particles were washed with a sufficient amount of pure water, filtered again, and dried overnight at 100°C. After calcining in air at 550°C for 1 hour, it was treated with 45% steam at 600°C for 3 hours.

[0069] The obtained powder was dispersed in 1 mol / L hydrochloric acid at 40°C, filtered, and then the solid particles were washed with a sufficient amount of pure water, filtered again, and dried overnight at 100°C to obtain MFI zeolite. The physical properties of the obtained MFI zeolite are shown in Table 1.

[0070] 25 parts by weight of silica (manufactured by Nissan Chemical Industries, Ltd., product name Snowtex N-30G), 5 parts by weight of cellulose, and 40 parts by weight of pure water were added to 100 parts by weight of the MFI zeolite prepared above and kneaded. The kneaded mixture was then formed into a cylindrical molded body with a diameter of 1.5 mm and a length of 1.0 to 7.0 mm (average length 3.4 mm). This was dried overnight at 100°C. The dried molded body was calcined in an air stream at 600°C for 2 hours to obtain a molded body, which was used as a catalyst for converting pyrolysis products of hydrocarbon plastics.

[0071] The resulting molded body was used in a catalyst for converting pyrolysis products of hydrocarbon-based plastics to produce lower hydrocarbons at a temperature of 585°C, and the catalytic reaction was evaluated. The results are shown in Table 1. Useful components such as olefins, paraffins, and aromatic hydrocarbons with carbon numbers of 2 to 8 were obtained with high selectivity. Furthermore, high catalytic performance was maintained even after the reaction was completed, enabling stable production and also exhibiting excellent coking resistance.

[0072] Example 3 The procedures for crystallization of zeolite in an autoclave, washing, and drying were carried out in the same manner as in Example 1.

[0073] The obtained dried powder was calcined in air at 550°C, dispersed in 1 mol / L hydrochloric acid at room temperature, filtered, and then the solid particles were washed with a sufficient amount of pure water, filtered again, and dried overnight at 100°C.

[0074] The obtained powder was calcined in air at 550° C. for 1 hour, and then treated with 20% steam at 600° C. for 60 minutes. The physical properties of the obtained MFI zeolite are shown in Table 1.

[0075] 25 parts by weight of silica (manufactured by Nissan Chemical Industries, Ltd., product name Snowtex N-30G), 5 parts by weight of cellulose, and 40 parts by weight of pure water were added to 100 parts by weight of the MFI zeolite prepared above and kneaded. The kneaded mixture was then formed into a cylindrical molded body with a diameter of 1.5 mm and a length of 1.0 to 7.0 mm (average length 3.5 mm). This was dried overnight at 100°C. The dried molded body was calcined in an air stream at 600°C for 2 hours to obtain a molded body, which was used as a catalyst for converting pyrolysis products of hydrocarbon plastics.

[0076] Using the obtained catalyst for converting pyrolysis products of hydrocarbon-based plastics, lower hydrocarbons were produced at a temperature of 585°C, and the catalytic reaction was evaluated. The results are shown in Table 1. Useful components such as olefins, paraffins, and aromatic hydrocarbons with carbon numbers of 2 to 8 were obtained with high selectivity. Furthermore, high catalytic performance was maintained even after the reaction was completed, enabling stable production and also exhibiting excellent coking resistance.

[0077] Comparative Example 1 The procedures for crystallization of zeolite in an autoclave, washing, and drying were carried out in the same manner as in Example 1.

[0078] The obtained dry powder was calcined in air at 550°C, dispersed in 1 mol / L hydrochloric acid at room temperature, filtered, and the solid particles were washed with a sufficient amount of pure water. After filtering again, the solid particles were dried overnight at 100°C to obtain zeolite. The physical properties of the obtained zeolite are shown in Table 1.

[0079] 25 parts by weight of silica (manufactured by Nissan Chemical Industries, Ltd., product name Snowtex N-30G), 5 parts by weight of cellulose, and 40 parts by weight of pure water were added to 100 parts by weight of the zeolite prepared above and kneaded. The kneaded mixture was then formed into a cylindrical molded body with a diameter of 1.5 mm and a length of 1.0 to 7.0 mm (average length 3.6 mm). This was dried overnight at 100°C. The dried molded body was calcined in an air stream at 600°C for 2 hours to obtain a molded body.

[0080] The resulting molded product was used as a catalyst to produce lower hydrocarbons at 585°C, and the catalytic reaction was evaluated. The results are shown in Table 1. The selectivity for olefins, paraffins, and aromatic hydrocarbons having 2 to 8 carbon atoms was low, and the catalytic activity decreased significantly, so the product had poor performance as a catalyst for converting pyrolysis products.

[0081] Comparative Example 2 100 parts by weight of proton-type MFI zeolite powder (manufactured by Tosoh Corporation, product name: HSZ-840HOA) were mixed with 40 parts by weight of silica (manufactured by Nissan Chemical Industries, Ltd., product name: Snowtex N-30G), 5 parts by weight of cellulose, and 40 parts by weight of pure water, and the mixture was then formed into a cylindrical molded body with a diameter of 1.5 mm and a length of 1.0 to 7.0 mm (average length 3.5 mm). This was dried overnight at 100°C. The dried molded body was calcined in an air stream at 600°C for 2 hours to obtain a molded body.

[0082] The resulting molded product was used as a catalyst to produce lower hydrocarbons at a temperature of 585°C, and the catalytic reaction was evaluated. The results are shown in Table 1. The selectivity for useful components, namely olefins, paraffins, and aromatic hydrocarbons with 2 to 8 carbon atoms, was low, and the catalytic activity was significantly reduced, so the product had poor performance as a catalyst for converting pyrolysis products.

[0083] [Table 1]

[0084] Example 4 100 g of the MFI zeolite molded body obtained in Example 1 was immersed in 109.9 g of a 0.75 mol / L aqueous zinc acetate solution for 30 minutes. The molded body was separated by filtration, dried overnight at 110°C, and then calcined for 5 hours at 550°C in an air stream to obtain a zinc-containing MFI zeolite. The zinc content of the obtained zinc-containing MFI zeolite was 2.6 wt%.

[0085] The zinc-containing MFI zeolite had a 10-membered ring pore structure, and the average particle diameter measured using TEM was 25 nm, the amount of outer surface B acid was 2.8 μmol / g, the total amount of B acid was 0.06 mmol / g, and the outer surface B acid ratio was 4.7%.

[0086] Using zinc-containing MFI-type zeolite as a catalyst for converting pyrolysis products of hydrocarbon-based plastics, lower hydrocarbons were produced at a temperature of 530°C, and the catalytic reaction was evaluated. The results are shown in Table 2. Paraffins, olefins, and aromatic hydrocarbons with carbon numbers of 2 to 8, which are useful as petrochemical products, showed high selectivity, and each component was produced in a well-balanced manner.

[0087] Example 5 240 g of the MFI zeolite formed body obtained in Example 1 was packed into a polyvinyl chloride tube with an inner diameter of 10 mm (packing length: 2.0 m). A 12.1 mmol / L aqueous calcium hydroxide solution was circulated for 6 hours at a linear flow velocity of 26 cm / min. Thereafter, pure water was circulated at the same linear flow velocity, and washing was repeated until the pH fell within the range of 8 to 10. The formed body was separated by filtration, dried at 110°C overnight, and then calcined at 550°C for 5 hours in an air stream, thereby obtaining a calcium-containing MFI zeolite. The calcium content of the obtained calcium-containing MFI zeolite was 0.23 wt%.

[0088] The calcium-containing MFI zeolite had a 10-membered ring pore structure, and the average particle size measured using TEM was 25 nm, the amount of B acid on the outer surface was 2.8 μmol / g, the total amount of B acid was 0.13 mmol / g, and the outer surface B acid ratio was 2.2%.

[0089] Using calcium-containing MFI-type zeolite as a catalyst for converting pyrolysis products of hydrocarbon-based plastics, lower hydrocarbons were produced at a temperature of 585°C and the catalytic reaction was evaluated. The results are shown in Table 2. Paraffins, olefins, and aromatic hydrocarbons with carbon numbers of 2 to 8, which are useful as petrochemical products, showed high selectivity, and each component was produced in a well-balanced manner.

[0090] Example 6 Catalytic reaction evaluation was carried out in the same manner as in Example 1, except that low-density polyethylene (LDPE) was used instead of HDPE as the hydrocarbon-based plastic and lower hydrocarbons were produced at a temperature of 530°C. The results are shown in Table 2. Useful components, such as olefins, paraffins, and aromatic hydrocarbons having 2 to 8 carbon atoms, were obtained with high selectivity. Furthermore, high catalytic performance was maintained even after the reaction was completed, enabling stable production and providing excellent coking resistance.

[0091] [Table 2] [Industrial Applicability]

[0092] The thermal decomposition product conversion catalyst of the present invention and the method for producing lower hydrocarbons using the same exhibit excellent catalytic performance when converting hydrocarbon plastics, particularly the thermal decomposition products of waste plastics, into lower hydrocarbons, and the industrial value of the catalyst is extremely high.

Claims

1. A catalyst for converting a pyrolysis product of a polyolefin, comprising: A catalyst for converting pyrolysis products, characterized in that it is a conversion catalyst containing a zeolite that satisfies the following characteristics (i) to (iii): (i) The average particle size is 100 nm or less. (ii) 10-ring pore zeolites of MFI type or MEL type. (iii) The Bronsted acid amount of the outer surface is 0.1 to 10.0 μmol / g.

2. The catalyst for converting pyrolysis products according to claim 1, further comprising: (iv) a Bronsted acidity of 0.01 to 1.0 mmol / g.

3. The thermal decomposition product conversion catalyst according to claim 1 or 2, further comprising (v) at least one metal selected from sodium, potassium, calcium, silver, and zinc, the content of which is 0.05 to 5.0 wt %.

4. 4. The pyrolysis product conversion catalyst according to claim 1, further comprising silica and having a cylindrical shape with a diameter of 1.0 to 10 mm or a thickness of 0.5 to 5.0 mm.

5. A method for producing lower hydrocarbons, which comprises contacting a thermal decomposition product of a polyolefin with the thermal decomposition product conversion catalyst according to any one of claims 1 to 4.

6. A method for producing lower hydrocarbons as described in claim 5, characterized in that the polyolefin is at least one selected from polyethylene, polypropylene, and ethylene propylene rubber.

7. A method for producing lower hydrocarbons as described in claim 5 or 6, characterized in that the polyolefin is waste plastics and / or waste products produced during the production and processing of polyolefins.

8. 8. The method for producing lower hydrocarbons according to any one of claims 5 to 7, wherein the lower hydrocarbons are olefins, paraffins, or aromatic hydrocarbons having 2 to 8 carbon atoms.

9. 9. The method for producing lower hydrocarbons according to claim 5, wherein the selectivity for lower hydrocarbons is 60% or more.

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