JP2022175167A - Conversion catalyst for thermal decomposition product of hydrocarbon-based plastic and production method of lower hydrocarbon using the same - Google Patents

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

The present invention provides a pyrolysis product conversion catalyst that enables the conversion of pyrolysis products of hydrocarbon-based plastics into useful substances. C) Aliphatic hydrocarbons consisting of paraffins, olefins, diolefins, etc. of 1 to 30 are highly efficiently converted into olefins, paraffins, aromatic hydrocarbons, etc. having 2 to 8 carbon atoms that are useful as petrochemical products. The present invention relates to a conversion catalyst for pyrolysis products of hydrocarbon-based plastics that enables well-balanced and stable conversion, and a method for producing lower hydrocarbons using the same.

In recent years, the problem of global warming and the problem of marine plastics have come under close scrutiny, and attention has been focused on chemical recycling in which waste plastics are chemically decomposed and reused as raw materials for petrochemical products. In particular, thermal cracking technology converts thermoplastic polyolefin (polyethylene, polypropylene), which accounts for half of waste plastics, into hydrocarbon oil, and if this hydrocarbon oil is used as a raw material for naphtha crackers, etc., This is an important technology that enables the recycling of plastics.

Oil conversion technology by pyrolysis of waste plastics has been known for a long time, and when pyrolyzed under oxygen-free and non-catalytic conditions, products with a wide carbon number distribution of C1 to C30, that is, hydrocarbon oils are produced. can get. Of these, C5 to C10 light oil can be used as raw material oil for naphtha crackers, but C11 or higher kerosene, light oil, heavy oil, and wax are used as fuel, and the added value of products was not high.

As a method for increasing the added value of products, a method of thermally decomposing polyolefin (waste) plastics and contacting the product generated by the thermal decomposition with a catalyst layer such as zeolite to recover hydrocarbon oil (for example, Patent Document 1, Non-Patent Document 1) has been proposed.

Further, a waste plastic treatment method has been proposed (see, for example, Patent Document 2) in which hydrocarbon oil is recovered by contacting a pyrolysis product obtained by vaporizing waste plastic by pyrolysis with a boron-containing silicate catalyst. Furthermore, a method for treating waste plastics using a gallium-containing silicate catalyst (see, for example, Patent Document 3), and the like have been proposed.

JP-A-63-178195 Patent No. 4341162 Patent No. 4103198

Kobunshi, Vol.45, p.311 (1996)

However, in the method proposed in Patent Document 1, by using a ZSM-5 catalyst, the carbon number distribution of the hydrocarbon oil is reduced from C5 to C38 to C5 to C21, but it still has a value added of C11 or more. There was a problem that there were many fractions of low kerosene, light oil, and heavy oil. In the method proposed in Non-Patent Document 1, in addition to ZSM-5, thermal decomposition is performed using HY, REY, and Ni/ReY catalysts. Although the selectivity is increased, these Y-type zeolites are poor in thermal stability, and there are still many fractions of C9 or higher with low added value, and they are not sufficient as industrial catalysts.

In the method proposed in Patent Document 2, by using a boron-containing silicate catalyst, the molecular weight of the hydrocarbon oil is significantly reduced, and in particular, the total selectivity for C3 and C4 olefins and paraffins is increased. It is difficult to produce such components with existing plants, for example, the load on a specific distillation column in an ethylene plant (naphtha cracker) increases, and the operating rate of the naphtha cracker has to be excessively reduced, or It was not economically rational, such as the need to install a new distillation column. In addition, the boron-containing silicate is difficult to synthesize and is difficult to obtain, and its coking resistance is not sufficient, so satisfactory investigations have not been made in terms of catalyst life. Furthermore, in the method proposed in Patent Document 3, by using a gallium-containing silicate catalyst, the carbon number distribution is C1 to C13, and the selectivity for benzene (C6), toluene (C7), and xylene (C8) in particular is increased. However, in gallium-containing silicates, especially gallosilicates, it is difficult to insert Ga metal into the silicate skeleton, and it is difficult to synthesize industrially with good reproducibility. Since it was not sufficient, there was still room for improvement in terms of catalyst life.

Accordingly, a hydrocarbon-based plastic pyrolysis product conversion catalyst that enables highly efficient conversion of hydrocarbon-based plastic pyrolysis products into C2 to C8 hydrocarbons useful as petrochemical products, and the same. The emergence of a method for producing the lower hydrocarbons used has been desired.

As a result of intensive studies to solve the above problems, the present inventors have found that a conversion catalyst containing a specific 10-membered ring pore zeolite is resistant to thermal decomposition products of hydrocarbon plastics as a raw material. In addition to being excellent in coking properties, catalyst life, etc., the selectivity of paraffins, olefins, and aromatic hydrocarbons having 2 to 8 carbon atoms useful as petrochemical products is improved, and it is found that it becomes a catalyst that exhibits excellent performance. The present invention has been completed.

That is, the present invention provides a conversion catalyst for pyrolysis products of hydrocarbon-based plastics, which is characterized by being a conversion catalyst containing zeolite that satisfies the following characteristics (i) to (iii): The present invention relates to a material conversion catalyst and a method for producing lower hydrocarbons using the same.
(i) an average particle size of 100 nm or less;
(ii) 10-membered ring pore zeolite of MFI type or MEL type.
(iii) Bronsted acid content on the outer surface is 0.1 to 10.0 μmol/g.

The present invention will be described in detail below.

The thermal decomposition product conversion catalyst of the present invention is useful as a petrochemical product even for thermal decomposition products of hydrocarbon plastics, which have been difficult to use as raw materials in the past because they contain a wide variety of components. It is a catalyst that enables highly selective conversion to lower hydrocarbons, especially olefins having 2 to 8 carbon atoms, paraffins, aromatic hydrocarbons, etc., and (i) average particle size (hereinafter referred to as PD ) is PD ≤ 100 nm, (ii) 10-membered ring pore zeolite that is MFI type or MEL type, (iii) Bronsted acid point on the outer surface is 0.1 to 10.0 μmol / g It contains zeolites that also satisfy the requirements.

The zeolite constituting the thermal decomposition product conversion catalyst of the present invention has (i) a PD ≤ 100 nm, and is particularly excellent in thermal stability, so it is desirable that 5 nm ≤ PD ≤ 100 nm. Here, if the PD exceeds 100 nm, the efficiency of conversion of thermal decomposition products of hydrocarbon-based plastics into lower hydrocarbons will be poor.

In addition, PD in the present invention is not limited to the method of measurement. For example, 100 or more arbitrary particles are selected from a photograph of a scanning electron microscope (SEM) or a transmission electron microscope (TEM), and the average diameter is determined. method, a method of calculation using the following formula (1) from the outer surface area of zeolite, and any other method.
PD=6/S×(1/(2.29×10 ⁶ )+0.18×10 ⁻⁶ ) (1)
(Here, S indicates the outer surface area (m ² /g).)
The outer surface area (S (m ² /g)) in formula (1) can be obtained from a t-plot method using a general nitrogen adsorption method at liquid nitrogen temperature. For example, when t is the thickness of the adsorption amount, linear approximation is applied to the measurement points in the range of 0.6 to 1 nm with respect to t, and the outer surface area of the zeolite is obtained from the slope of the obtained regression line.

Among them, the method using SEM or TEM is preferable because it enables easy measurement.

The zeolite constituting the thermal decomposition product conversion catalyst of the present invention is (ii) MFI type or MEL type 10-membered ring pore zeolite. Here, examples of MFI-type zeolites include aluminosilicate compounds belonging to the structure code MFI defined by the International Zeolite Society. Here, when zeolite other than MFI type or MEL type 10-membered ring pore zeolite is included, the efficiency of the conversion reaction of thermal decomposition products of hydrocarbon-based plastics is inferior.

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

In the zeolite constituting the thermal decomposition product conversion catalyst of the present invention, the conversion efficiency of the thermal decomposition products of hydrocarbon plastics, especially lower hydrocarbons such as olefins having 2 to 8 carbon atoms, paraffins, and aromatic hydrocarbons (iv) The amount of B acid is preferably 0.01 to 1.0 mmol/g, more preferably 0.1 to 1.0 mmol/g, because the catalyst has excellent selectivity to hydrogen.

Here, the B acid amount of zeolite indicates the amount of Bronsted acid points (hereinafter sometimes referred to as B acid points), and indicates the acidic OH groups present in the zeolite. Zeolites usually have B acid sites on their outer surface and within the (micro)pores. And, having only a few B acid sites on the outer surface means that most of the B acid sites are present in the (micro)pores.

As a method for confirming the amount of B acid on the outer surface of the zeolite, any method can be used as long as it can be confirmed. It can be confirmed by adsorption of quinoline. 2,4-dimethylquinoline has an adsorption property with B acid sites (acidic OH groups) present in zeolite (including inside pores). However, when the (micro)pore diameter of the zeolite is smaller than the 2,4-dimethylquinoline molecule, such as the MFI type, it cannot penetrate into the (micro)pores, and the B acid site in the (micro)pores and cannot be absorbed. That is, it adsorbs only to the B acid sites on the outer surface of the zeolite. Therefore, by determining the adsorption amount of 2,4-dimethylquinoline to the B acid sites on the outer surface of the MFI zeolite, the amount of B acid on the outer surface can be quantified.

As a more specific method, an infrared absorption spectrum at 150° C. is measured for zeolite that has undergone degassing and dehydration treatment at 400° C. for 2 hours as a pretreatment of the zeolite. Then, 2,4-dimethylquinoline gas is introduced into the degassed and dehydrated zeolite and adsorbed for 30 minutes. An adsorbed zeolite is prepared and an infrared absorption spectrum is measured at 150°C. That is, in the infrared absorption difference spectrum before and after 2,4-dimethylquinoline adsorption, by quantifying the infrared absorption difference (decrease) in the range of 3600 to 3650 cm ^-1 , the amount of B acid on the outer surface can be obtained. can. 2,4-Dimethylquinoline also adsorbs to silanol sites on the zeolite surface, and absorption derived from O—H stretching vibration of silanol is observed at 3700 to 3800 cm ⁻¹ . On the other hand, the absorption derived from the O-H stretching vibration of the B acid point on the outer surface of the zeolite is observed at 3600 to 3650 cm ^-1 , and 2,4-dimethylquinoline is adsorbed to the O-H stretching vibration of the B acid point. The decrease in the infrared absorption spectrum in the range of 3600-3650 cm ^-1 derived from 2,4-dimethylquinoline indicates that 2,4-dimethylquinoline was adsorbed to the B acid sites on the outer surface of the zeolite.

In addition, as a method for measuring the B acid amount of the zeolite (B acid points existing on the outer surface and in the (micro)pores), any method can be used as long as it can be measured. It can be confirmed by, for example, adsorption of pyridine, which has an adsorption property to the B acid site. Pyridine has an adsorption property with B acid sites (acidic OH groups) present in zeolite (including inside pores). It can also penetrate into the interior and can also adsorb B-acid sites on the outer surface and within the (micro)pores. Therefore, it is possible to quantify the amount of all B acids present in the zeolite, including the B acid sites present in the pores of the MFI zeolite.

As a more specific method, an infrared absorption spectrum at 150° C. is measured for zeolite that has undergone degassing and dehydration treatment at 400° C. for 2 hours as a pretreatment of the zeolite. Then, pyridine gas is introduced into the degassed and dehydrated zeolite and adsorbed for 10 minutes, excess pyridine is removed by exhaust at 150 ° C., pyridine-adsorbed zeolite is prepared, and infrared absorption spectrum is measured at 150 ° C. conduct. That is, in the infrared absorption difference spectrum before and after pyridine adsorption, by quantifying the infrared absorption difference (decrease) in the range of 1515 to 1565 cm ⁻¹ , the B acid amount including the inside of the pores can be obtained.

The zeolite constituting the thermal decomposition product conversion catalyst of the present invention is particularly excellent in conversion efficiency of thermal decomposition products of hydrocarbon plastics and selectivity for olefins having 2 to 8 carbon atoms, paraffins, and aromatic hydrocarbons. Since it serves as a catalyst, it is preferable that the outer surface has a small number of B acid sites, and most of the B acid sites are present in the (micro) pores. The B acid sites present on the outer surface are , preferably 1 to 10% of the total B acid sites. The ratio of B acid sites on the outer surface is obtained by converting the B acid amount on the outer surface of the zeolite described above to the B acid amount present in the zeolite (including the inside of the pores).

As a method for producing the zeolite, any method can be used as long as it is possible to produce a zeolite that satisfies the properties described in (i) to (iii) above. Then, a zeolite having a specific amount of trace B acid sites on the outer surface, that is, as a method for selectively removing B acid sites on the surface of the zeolite, a zeolite that satisfies the characteristics of (i) to (ii) is produced. For example, a part or all of the calcination treatment (heat treatment) may be hydrothermal (steam) treatment, and an ion exchange treatment may be added before or after the calcination treatment.

Then, as a method for synthesizing a zeolite that satisfies the characteristics of (i) to (ii), by using a generally known method, a PD ≤ 100 nm, an MFI type or MEL type 10-membered ring pore skeleton structure can be a zeolite having Specifically, it can be produced by mixing a compound containing an alkali metal and/or an alkaline earth metal as a cation, an organic structure-directing agent, and an aluminosilicate gel, and firing the resulting crystal. Examples of compounds containing alkali metals and alkaline earth metals in this case include sodium hydroxide, potassium hydroxide, calcium hydroxide, magnesium hydroxide and the like, with sodium hydroxide being preferred. Examples of organic structure directing agents include tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, tetraethylammonium hydroxide and the like. Moreover, as an aluminosilicate gel, amorphous aluminosilicate gel etc. can be mentioned, for example.

Furthermore, when making a zeolite that satisfies the characteristics of (i) to (iii), ion exchange is performed before calcining the crystals obtained by the above, and part or all of the calcination is performed by hydrothermal treatment. After that, it can be produced by a method of further ion-exchanging, a method of calcining the crystal obtained by the above, ion-exchanging it to obtain a proton-type zeolite, and then calcining it in a hydrothermal atmosphere. Become.

As for the firing conditions at that time, the treatment temperature is preferably 300 to 900°C, and particularly preferably 400 to 700°C. The treatment time is industrially preferably 5 minutes to 25 hours. The atmosphere can also include, for example, one or a combination of two or more of nitrogen, air, oxygen, argon, and other inert gases. A hydrothermal (steam) treatment is performed in part or all of the sintering step to desorb aluminum at the B acid site. The treatment temperature for the hydrothermal treatment is preferably 400 to 750°C, more preferably 500 to 650°C. Also, the water vapor concentration is preferably 5 to 100%, particularly preferably 10 to 80%.

Moreover, the ion exchange is performed before and after the baking process, and may be performed by dividing the ion exchange into a plurality of times. Ion exchange includes ion exchange using acids such as ammonium chloride, hydrochloric acid and nitric acid, and those using hydrochloric acid and nitric acid are preferred. Ion exchange can also be replaced by washing with water.

The zeolite that constitutes the thermal decomposition product conversion catalyst of the present invention exhibits high catalytic performance as it is, but since it becomes a catalyst that exhibits even higher coking resistance and catalyst life, (v) sodium, potassium, calcium, and silver , and zinc, and the metal-containing zeolite preferably contains 0.05 to 5.0 wt% of the metal. Among these metals, zinc- and/or calcium-containing zeolites are more preferable because they increase the selectivity of olefins having 2 to 8 carbon atoms, paraffins, and aromatic hydrocarbons. In addition, the method of introducing the metal is not limited, and any method such as impregnation support, ion exchange, physical mixing, and vapor deposition is possible.

And when it is used as a thermal decomposition product conversion catalyst, it is preferable to give a shape as a molded body because it becomes a catalyst excellent in handleability and catalytic performance. Any method may be used to shape the zeolite powder. Examples include a method of mixing further additives in a predetermined proportion and molding the mixture into a predetermined shape to form a green body, and a method of accompanying sintering to form a green body. In particular, when it is used as a catalyst for converting thermal decomposition products of hydrocarbon plastics, it should not only have excellent moldability as a molded article, but also exhibit high crushing strength and be excellent in handleability and catalyst life. For this reason, it is preferable to use a molded body composed of the zeolite and a binder, and it is more preferable to use a molded body composed of the zeolite and silica because it exhibits better catalytic performance. Any silica may be used as long as it belongs to the category called silica, and it may have a specific crystal structure or may be non-crystalline. Furthermore, there are no restrictions on the particle size, aggregation size, etc. of silica. In addition, the blending ratio of the zeolite and silica is arbitrary, and the zeolite: silica = 50 to 95: 50 to 5 (weight ratio ), more preferably 60-90:40-10.

The thermal decomposition product conversion catalyst may have any shape, for example, cylindrical shape, cylindrical shape, triangular prism shape, square prism shape, pentagonal prism shape, polygonal prism shape such as hexagonal prism shape, hollow polygonal prism shape, etc. Shapes, spheres, and the like can be mentioned, and among them, columnar shapes and cylindrical shapes are preferable because they provide catalysts with excellent continuous productivity and high crushing strength. In addition, the size such as diameter, width, and length, and the density such as bulk density and true density can be arbitrarily selected in consideration of packing efficiency. , paraffin, aromatic hydrocarbons, etc., it should have a cylindrical shape with a diameter of 1.0 to 10 mm or a thickness of 0.5 to 5.0 mm. Preferably.

The thermal decomposition product conversion catalyst of the present invention is produced by contacting hydrocarbons, which are thermal decomposition products of hydrocarbon-based plastics, with hydrocarbons, particularly lower hydrocarbons useful as petrochemical products, i.e., lower hydrocarbons having 2 carbon atoms. It enables highly selective production of olefins of ∼8, paraffins and aromatic hydrocarbons. There are no restrictions on the thermal decomposition products of hydrocarbon-based plastics, which are the raw materials at that time, as long as they can be obtained by thermally decomposing hydrocarbon-based plastics. , since it can contribute to solving social issues in terms of both securing resources and processing waste, hydrocarbon plastics that do not have oxygen atoms or nitrogen atoms in the plastic structure and exhibit thermoplasticity, and furthermore, It is preferably a pyrolysis product of a waste product in the production and processing of used waste plastics and/or hydrocarbon plastics. Hydrocarbon-based plastics include, for example, polyethylene, polypropylene, ethylene-propylene rubber, polystyrene, etc. Plastics in which chlorine atoms are separated and removed from chlorinated plastics such as vinyl chloride resin, vinylidene chloride resin, and chlorinated polyethylene. is mentioned.

The thermal decomposition products of hydrocarbon-based plastics are not particularly limited as long as they are hydrocarbons generated by thermal decomposition of hydrocarbon-based plastics. Mention may be made of products that melt below and pyrolyze this melt. Thermal decomposition products of hydrocarbon-based plastics are generally mixtures of aliphatic hydrocarbons consisting of paraffins, olefins, and diolefins with a carbon number distribution of C1 to C30, and the mixture ratio, etc., of hydrocarbon-based plastics, It can be appropriately selected depending on the thermal decomposition conditions and the like.

The thermal decomposition product conversion catalyst of the present invention highly selectively converts lower hydrocarbons, particularly olefins having 2 to 8 carbon atoms, paraffins, and aromatic hydrocarbons, by contacting thermal decomposition products of hydrocarbon plastics. The reaction temperature at that time is not particularly limited, and the range of 350 to 650 ° C. is preferable because it becomes a more efficient production method, and the selectivity of useful components is high. to 500 to 600° C. is more preferable. Moreover, there is no restriction 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 thermal decomposition products is not particularly limited as a ratio of the volume of the raw ^{thermal decomposition} product gas to the volume of the catalyst. . In that case, it can be diluted with a single or mixed gas selected from an inert gas such as nitrogen, hydrogen, carbon monoxide and carbon dioxide.

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

With the thermal decomposition product conversion catalyst of the present invention, the thermal decomposition products of hydrocarbon plastics are efficiently reduced in molecular weight and the cyclization dehydrogenation reaction proceeds efficiently, and lower hydrocarbons useful as petrochemical products, i.e., carbon number It is possible to produce 2 to 8 olefins, paraffins and aromatic hydrocarbons with high selectivity, particularly at a selectivity of 60% or more. In addition, since each component of olefins with 2 to 8 carbon atoms, paraffins, and aromatic hydrocarbons is produced in a well-balanced manner, efficient combined operation with existing plants can be performed without installing a new distillation column. be possible. Specifically, since the distillation column for each component of the ethylene plant can be fully utilized, the ethylene plant can be efficiently operated without excessively lowering the operating rate of the naphtha cracker.

Here, the thermal decomposition product conversion catalyst of the present invention is excellent in selectivity, efficiency, catalyst life, and coking resistance, but it does not produce lower hydrocarbons using thermal decomposition products of hydrocarbon plastics as raw materials. In production, coke is generated on the catalyst as the catalytic reaction progresses, and it is inevitable that the catalytic performance is lowered due to coke adhesion. A method for regenerating a catalyst whose catalytic performance has deteriorated is not particularly limited, but, for example, combustion removal with oxygen is preferably used. The coke attached to the thermal decomposition product conversion catalyst of the present invention is efficiently removed by contacting the catalyst with a gas containing 2 to 25% by weight of oxygen at 380 to 530 ° C., and the performance of the catalyst is improved. It is preferable to contact a gas with an oxygen content of 5 to 25% by weight and a temperature of 400 to 450° C. because it is particularly excellent in regeneration efficiency.

Examples of the gas 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, or neon. In addition, the amount of gas supplied during regeneration and the regeneration time are not particularly limited as long as the catalyst can be regenerated. Therefore, it is preferable to supply under the condition of gas volume/catalyst volume=200 to 700 per hour, and the regeneration time is preferably 30 to 65 hours.

The thermal decomposition product conversion catalyst of the present invention is stable over a long period of time and is useful as a petrochemical product because it has high coking resistance and a long catalyst life even when using thermal decomposition products of hydrocarbon plastics. Industrial utility is expected because it is possible to highly selectively produce paraffins, olefins, and aromatic hydrocarbons having 2 to 8 carbon atoms.

EXAMPLES The present invention will be specifically described below with reference to Examples, but the present invention is not limited to these Examples.

The 10-membered ring pore zeolites used in Examples and Comparative Examples were prepared based on Japanese Patent No. 6070336. Also, the zeolite and the thermal decomposition product conversion catalyst were evaluated and measured by the following methods.

～Measurement of 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). For TEM, a transmission electron microscope (manufactured by JEOL Ltd., (trade name) JEM-2100, acceleration voltage of 200 kV, observation magnification of 30,000 times) was used, and a sample lightly pulverized in a mortar was ultrasonically dispersed in acetone. A microscopic sample was prepared by dropping the solution onto a plastic support film and air-drying, and a photograph was taken. For each primary particle in the photograph, the average diameter in the direction perpendicular to the longest diameter and its midpoint was measured, and the average of a total of 300 particles was taken as the average particle diameter.

SEM uses a scanning electron microscope (manufactured by Keyence Corporation, (trade name) VE-9800, acceleration voltage 20 kV, observation magnification 2000 times), and a sample lightly pulverized in a mortar is placed on a sample stage and deposited with gold. was used as a specimen for microscopy, and a photograph was taken. The length of one side of 150 particles in the photograph was measured, and the average value was taken as the average crystal diameter.

~ 2,4-dimethylquinoline adsorption infrared absorption spectroscopy (external surface B acid amount) ~
Infrared absorption spectroscopy was measured by a transmission method using an FT-IR measurement device ((trade name) FT/IR-6700, manufactured by JASCO Corporation). A spectrum was obtained with 256 integrations using an MCT detector. The sample was formed into a disc with a diameter of 13 mm, and placed vertically on the infrared light path by placing it on a disc holder in a quartz vacuum degassing cell. As pretreatment of the sample, the temperature was raised to 400° C. at a rate of 10° C./min under vacuum evacuation and held for 2 hours. After cooling to 150° C., an infrared absorption spectrum was measured before adsorption of 2,4-dimethylquinoline. A 2,4-dimethylquinoline gas was introduced and adsorbed for 30 minutes, and after evacuating at 150° C. for 1 hour, the infrared absorption spectrum after adsorption of 2,4-dimethylquinoline was measured. By taking the difference between the infrared absorption spectrum after adsorption of 2,4-dimethylquinoline and the spectrum before adsorption, the change in infrared absorption due to adsorption was measured. Of this difference spectrum, the peak near 3600 cm ⁻¹ is the peak of the absorption spectrum of 2,4-dimethylquinoline adsorbed to Bronsted acid. The outer surface B acid amount was obtained from the following formula (2).
B acid amount (μmol/mg) = A S/(W ε) (2)
(Where, A: peak area intensity of target peak (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 (total B acid content) ~
In the above 2,4-dimethylquinoline adsorption infrared absorption spectroscopic measurement, the measurement was performed using the same apparatus and the same method, except that pyridine gas was introduced and adsorbed for 10 minutes.

However, the peak near 1545 cm in the difference spectrum is used as the peak of the absorption spectrum of pyridine adsorbed on Bronsted acid, and the integrated extinction coefficient is 1.67 ^{cm μmol −1 .} The amount of acid was determined.

~ Outer surface B acid ratio ~
The ratio obtained by dividing the outer surface B acid amount by the total B acid amount was defined as the outer surface B acid ratio.

～Measurement of powder X-ray diffraction～
Using an X-ray diffraction measurement device ((trade name) X'pert PRO MPD, manufactured by Spectris), the measurement was performed in the atmosphere using CuKα1 at a tube voltage of 45 kV and a tube current of 40 mA. A range of 0.04 to 5 degrees was analyzed at 0.08 degrees/step and 200 seconds/step. In addition, the background is removed by correcting the direct beam absorptance.

The crystal structure was identified by visually confirming the presence or absence of peaks. Alternatively, a peak search program may be used. A general program can be used for the peak search program. For example, the horizontal axis is 2θ (degrees) and the vertical axis is intensity (a.u.). After smoothing the measurement results with the SAVITSKY & GOLAY formula and the sliding polynomial filter, when performing the second derivative, three or more continuous points If there is a negative value for

~ SiO ₂ /Al ₂ O ₃ molar ratio, measurement of metal introduction amount ~
The SiO ₂ /Al ₂ O ₃ molar ratio of zeolite and the amount of introduced transition metal were determined by dissolving zeolite in a mixed aqueous solution of hydrofluoric acid and nitric acid, and performing inductively coupled plasma emission with an ICP device ((trade name) OPTIMA3300DV, manufactured by PerkinElmer). It was measured and determined by spectroscopic analysis (ICP-AES).

~Production equipment for lower hydrocarbons and method for producing the same~
Using the catalysts obtained in Examples and Comparative Examples, lower hydrocarbons were produced by the following method, and the performance of these catalysts as conversion catalysts for thermal decomposition products of hydrocarbon plastics was evaluated.

The production equipment for lower hydrocarbons consists of a stainless steel autoclave (inner volume: 200 ml) that melts and thermally decomposes hydrocarbon-based plastics, and a stainless steel reaction tube (inner diameter: 16 mm, length: 600 mm) that converts thermal decomposition products into lower hydrocarbons. ) was used. Here, the middle stage of the stainless steel reaction tube was filled with a molded body of catalyst, and pretreatment was performed by heating at 530° C. under dry air circulation.

A stainless steel autoclave was charged with high-density polyethylene (HDPE), which was lost during the manufacturing process of a low-pressure polyethylene manufacturing facility, and purged with nitrogen. By slowly raising the temperature to 180°C, HDPE was brought into a molten state, then heated to 450°C under nitrogen gas flow (40 ml/min) and thermally decomposed to obtain a thermal decomposition product, which is a hydrocarbon mixture. . The pyrolysis products were fed into a stainless steel reaction tube by nitrogen gas, contacted with a pyrolysis product conversion catalyst, and reacted. A ceramic tubular furnace was used to control the temperature of the catalyst (molded body) layer.

A reaction outlet gas and a reaction liquid were sampled, and gas components and liquid components were individually analyzed using a gas chromatograph. The gas component is measured by a gas chromatograph (manufactured by Shimadzu Corporation, (trade name) GC) equipped with a TCD detector and having a packing material (manufactured by Waters, (trade name) PorapakQ or GL Sciences, (trade name) MS-5A). -1700). The liquid components were analyzed using a gas chromatograph (manufactured by Shimadzu Corporation, (trade name) GC-2015) equipped with an FID detector and having a capillary column (manufactured by GL Sciences, (trade name) TC-1) as a separation column. .

The reaction conditions were set as follows.

(Catalytic reaction conditions during production of lower hydrocarbons)
Catalyst weight: 3.8 g.
Flowing gas: Nitrogen 40 ml/min.
Reaction temperature: 530°C or 585°C.
Reaction time: 24 hours.

~ Catalyst activity test method as an indicator of catalyst life ~
After the performance evaluation of the hydrocarbon-based plastic thermal decomposition product conversion catalyst in the above-mentioned lower hydrocarbon production equipment, the stainless steel autoclave was separated from the stainless steel reaction tube, and the following C4 fraction was used to perform the stainless steel reaction. An activity test of the pyrolysis product conversion catalyst packed in a tube was carried out. The conversion rate of the C4 fraction 1 hour after the start of the reaction was used as an indicator of the life of the catalyst.

(Catalytic reaction conditions in catalytic activity test)
C4 fraction: isobutane 2Nml/min, normal butane 5Nml/min, trans-2-butene 8Nml/min, 1-butene 15Nml/min, isobutene 3Nml/min, propane 7Nml/min, propylene 2Nml/min Diluent gas; nitrogen 42Nml / minute.
Reaction temperature: 530°C.
Reaction time: 1 hour.

Example 1
The amorphous aluminosilicate gel was added to and suspended in an aqueous solution of tetrapropylammonium hydroxide and sodium hydroxide. MFI-type zeolite was added as seed crystals to the resulting suspension to prepare a raw material composition. The amount of seed crystals added at that time was 0.7% by weight with respect to the weight of Al ₂ O ₃ and SiO ₂ 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.

The resulting raw material composition was sealed in a stainless steel autoclave and crystallized at 115° C. for 4 days with stirring to obtain a slurry mixture. After solid-liquid separation of the slurry mixed liquid after crystallization by a centrifugal sedimentation machine, the solid particles were washed with a sufficient amount of pure water and dried at 110° C. to obtain a dry powder.

The obtained dry powder was dispersed in 1 mol/L of room temperature hydrochloric acid, filtered, washed with a sufficient amount of pure water, filtered again, and dried at 100° C. overnight. After baking at 550° C. for 1 hour in air, it was treated with 30% water vapor at 600° C. for 2 hours.

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

Table 1 shows the physical properties of the obtained zeolite. The zeolite was a 10-membered ring pore zeolite having an MFI-type zeolite framework structure, and had an average particle size of 25 nm as measured using a TEM.

To 100 parts by weight of the zeolite prepared above, 25 parts by weight of silica (manufactured by Nissan Chemical Industries, Ltd., (trade name) Snowtex N-30G), 5 parts by weight of cellulose, and 40 parts by weight of pure water were added and kneaded. Then, the kneaded material was formed into a columnar compact having a diameter of 1.5 mm and a length of 1.0 to 7.0 mm (average length of 3.5 mm). It was dried overnight at 100°C. The molded body after drying was calcined at 600° C. for 2 hours in an air stream to obtain a molded body, which was used as a conversion catalyst for thermal decomposition products of hydrocarbon-based plastics.

Using the obtained hydrocarbon-based plastic thermal decomposition product conversion catalyst, lower hydrocarbons were produced at a temperature of 585° C., and the catalytic reaction was evaluated. Table 1 shows the results. Useful components such as olefins having 2 to 8 carbon atoms, paraffins and aromatic hydrocarbons were obtained with high selectivity. In addition, high catalytic performance was maintained even after completion of the reaction, enabling stable production and excellent coking resistance.

Example 2
Crystallization of zeolite by autoclaving, washing, and drying were performed in the same manner as in Example 1. The obtained dry powder was dispersed in 1 mol/L of room temperature hydrochloric acid, filtered, washed with a sufficient amount of pure water, filtered again, and dried at 100° C. overnight. After baking at 550° C. for 1 hour in air, it was treated with 45% water vapor at 600° C. for 3 hours.

The obtained powder is dispersed in 1 mol/L of hydrochloric acid at 40° C. and filtered, the solid particles are washed with a sufficient amount of pure water, filtered again, and dried at 100° C. overnight to obtain MFI zeolite. Obtained. Table 1 shows the physical properties of the obtained MFI-type zeolite.

To 100 parts by weight of the MFI type zeolite prepared above, 25 parts by weight of silica (manufactured by Nissan Chemical Industries, Ltd., (trade name) Snowtex N-30G), 5 parts by weight of cellulose, and 40 parts by weight of pure water were added and kneaded. . Then, the kneaded product was formed into a columnar compact having a diameter of 1.5 mm and a length of 1.0 to 7.0 mm (average length of 3.4 mm). It was dried overnight at 100°C. The molded body after drying was calcined at 600° C. for 2 hours in an air stream to obtain a molded body, which was used as a conversion catalyst for thermal decomposition products of hydrocarbon-based plastics.

Using a hydrocarbon-based plastic thermal decomposition product conversion catalyst, lower hydrocarbons were produced from the obtained compact at a temperature of 585° C., and the catalytic reaction was evaluated. Table 1 shows the results. Useful components such as olefins having 2 to 8 carbon atoms, paraffins and aromatic hydrocarbons were obtained with high selectivity. In addition, high catalytic performance was maintained even after completion of the reaction, enabling stable production and excellent coking resistance.

Example 3
Crystallization of zeolite by autoclaving, washing, and drying were performed in the same manner as in Example 1.

After firing the obtained dry powder at 550 ° C. in air, the obtained powder is dispersed in 1 mol / L of hydrochloric acid at room temperature, filtered, and then the solid particles are washed with a sufficient amount of pure water. After filtration, it was dried overnight at 100°C.

The obtained powder was calcined in air at 550° C. for 1 hour and then treated with 20% water vapor at 600° C. for 60 minutes. Table 1 shows the physical properties of the obtained MFI-type zeolite.

To 100 parts by weight of the MFI type zeolite prepared above, 25 parts by weight of silica (manufactured by Nissan Chemical Industries, Ltd., (trade name) Snowtex N-30G), 5 parts by weight of cellulose, and 40 parts by weight of pure water were added and kneaded. . Then, the kneaded material was formed into a columnar compact having a diameter of 1.5 mm and a length of 1.0 to 7.0 mm (average length of 3.5 mm). It was dried overnight at 100°C. The molded body after drying was calcined at 600° C. for 2 hours in an air stream to obtain a molded body, which was used as a conversion catalyst for thermal decomposition products of hydrocarbon-based plastics.

Using the obtained hydrocarbon-based plastic thermal decomposition product conversion catalyst, lower hydrocarbons were produced at a temperature of 585° C., and the catalytic reaction was evaluated. Table 1 shows the results. Useful components such as olefins having 2 to 8 carbon atoms, paraffins and aromatic hydrocarbons were obtained with high selectivity. In addition, high catalytic performance was maintained even after completion of the reaction, enabling stable production and excellent coking resistance.

Comparative example 1
Crystallization of zeolite by autoclaving, washing, and drying were performed in the same manner as in Example 1.

After baking the obtained dry powder at 550 ° C. in air, the obtained powder is dispersed in 1 mol / L hydrochloric acid at room temperature, filtered, and then the solid particles are washed with a sufficient amount of pure water. After filtration, it was dried at 100° C. overnight to obtain zeolite. Table 1 shows the physical properties of the obtained zeolite.

To 100 parts by weight of the zeolite prepared above, 25 parts by weight of silica (manufactured by Nissan Chemical Industries, Ltd., (trade name) Snowtex N-30G), 5 parts by weight of cellulose, and 40 parts by weight of pure water were added and kneaded. Then, the kneaded product was formed into a columnar compact having a diameter of 1.5 mm and a length of 1.0 to 7.0 mm (average length of 3.6 mm). It was dried overnight at 100°C. The molded body after drying was calcined at 600° C. for 2 hours under air circulation to obtain a molded body.

Using the obtained compact as a catalyst, lower hydrocarbons were produced under conditions of 585° C., and the catalytic reaction was evaluated. Table 1 shows the results. The selectivity for olefins having 2 to 8 carbon atoms, paraffins and aromatic hydrocarbons was low, and the catalytic activity was remarkably lowered, resulting in poor performance as a thermal decomposition product conversion catalyst.

Comparative example 2
Proton type MFI type zeolite powder (manufactured by Tosoh Corporation, trade name: HSZ-840HOA) 100 parts by weight, silica (manufactured by Nissan Chemical Industries, Ltd., (trade name) Snowtex N-30G) 40 parts by weight, cellulose 5 Parts by weight and 40 parts by weight of pure water were added and kneaded. Then, the kneaded material was formed into a columnar compact having a diameter of 1.5 mm and a length of 1.0 to 7.0 mm (average length of 3.5 mm). It was dried overnight at 100°C. The molded body after drying was calcined at 600° C. for 2 hours under air circulation to obtain a molded body.

Using the obtained compact as a catalyst, lower hydrocarbons were produced at a temperature of 585° C., and the catalytic reaction was evaluated. Table 1 shows the results. The selectivity of useful components such as olefins having 2 to 8 carbon atoms, paraffins and aromatic hydrocarbons was low, and the catalyst activity was remarkably lowered, resulting in poor performance as a catalyst for converting thermal decomposition products.

Example 4
100 g of the MFI-type zeolite compact obtained in Example 1 was immersed in 109.9 g of a 0.75 mol/L zinc acetate aqueous solution for 30 minutes. After the compact was separated by filtration, it was dried at 110° C. overnight and then calcined at 550° C. for 5 hours under air flow to obtain a zinc-containing MFI zeolite. The zinc content of the resulting zinc-containing MFI zeolite was 2.6 wt%.

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

Using zinc-containing MFI-type zeolite as a catalyst for converting thermal decomposition products of hydrocarbon-based plastics, lower hydrocarbons were produced at a temperature of 530° C., and the catalytic reaction was evaluated. Table 2 shows the results. C2-C8 paraffins, olefins and aromatic hydrocarbons, which are useful as petrochemical products, exhibited high selectivity, and each component was produced in a well-balanced manner.

Example 5
A polyvinyl chloride tube having an inner diameter of 10 mm was filled with 240 g of the MFI-type zeolite compact obtained in Example 1 (filling length: 2.0 m). A 12.1 mmol/L calcium hydroxide aqueous solution was circulated at a linear flow velocity of 26 cm/min for 6 hours. Thereafter, pure water was circulated at the same flow linear velocity, and washing was repeated until the pH fell within the range of 8-10. After the compact was separated by filtration, it was dried at 110° C. overnight and then calcined at 550° C. for 5 hours under air circulation to obtain a calcium-containing MFI zeolite. The calcium content of the obtained calcium-containing MFI zeolite was 0.23 wt%.

The calcium-containing MFI-type zeolite has a 10-membered ring pore structure, an average particle diameter measured using a TEM of 25 nm, an outer surface B acid content of 2.8 μmol/g, and a total B acid content of 0.13 mmol. /g, and the outer surface B acid rate was 2.2%.

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

Example 6
Catalytic reaction was evaluated in the same manner as in Example 1, except that low-density polyethylene (LDPE) was used as the hydrocarbon-based plastic instead of HDPE, and that lower hydrocarbons were produced at a temperature of 530°C. rice field. Table 2 shows the results. Useful components such as olefins having 2 to 8 carbon atoms, paraffins and aromatic hydrocarbons were obtained with high selectivity. In addition, high catalytic performance was maintained even after completion of the reaction, enabling stable production and excellent coking resistance.

The catalyst for converting thermal decomposition products of the present invention and the method for producing lower hydrocarbons using the catalyst exhibit excellent catalytic performance in converting thermal decomposition products of hydrocarbon plastics, particularly waste plastics, into lower hydrocarbons. and its industrial value as a catalyst is extremely high.

Claims (9)

A catalyst for converting thermal decomposition products of hydrocarbon-based plastics, the catalyst containing zeolite that satisfies the following characteristics (i) to (iii).
(i) an average particle size of 100 nm or less;
(ii) 10-membered ring pore zeolite of MFI type or MEL type.
(iii) Bronsted acid content on the outer surface is 0.1 to 10.0 μmol/g. 2. The thermal decomposition product conversion catalyst according to claim 1, further comprising (iv) a Bronsted acid content of 0.01 to 1.0 mmol/g. Further, (v) contains at least one metal selected from sodium, potassium, calcium, silver, and zinc, and the content is 0.05 to 5.0 wt%. 3. or the thermal decomposition product conversion catalyst according to 2. The thermal decomposition product according to any one of claims 1 to 3, further comprising silica and having a cylindrical shape with a diameter of 1.0 to 10 mm or a cylindrical shape with a thickness of 0.5 to 5.0 mm. conversion catalyst. A process for producing lower hydrocarbons, which comprises contacting pyrolysis products of a hydrocarbon-based plastic in the presence of the pyrolysis product conversion catalyst according to any one of claims 1 to 4. 6. The method for producing lower hydrocarbons according to claim 5, wherein the hydrocarbon-based plastic is at least one selected from polyethylene, polypropylene, ethylene-propylene rubber, and polystyrene. 7. The method for producing lower hydrocarbons according to claim 5 or 6, wherein the hydrocarbon-based plastic is a used waste plastic and/or a waste product during the production/processing of the hydrocarbon-based plastic. The method for producing a lower hydrocarbon according to any one of claims 5 to 7, wherein the lower hydrocarbon is an olefin, paraffin or aromatic hydrocarbon having 2 to 8 carbon atoms. The method for producing lower hydrocarbons according to any one of claims 5 to 8, characterized in that the selectivity for lower hydrocarbons is 60% or more.