JP2018141140A - Phthalate plastic chemical recycling method, and composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a phthalate plastic chemical recycling method that makes it possible to produce a substance to be a raw material allowing efficient production of recycled products, the substance avoiding problems such as blockage of piping in a thermal decomposition reaction device.SOLUTION: A phthalate plastic chemical recycling method includes obtaining an aromatic compound by thermally decomposing phthalate plastic in the presence of a nickel catalyst.SELECTED DRAWING: None

Description

  The present invention relates to a method and a composition for chemical recycling of phthalic acid plastics.

Phthalic acid plastics are used in various applications. Among them, polyesters having aromatic dicarboxylic acid as the main dicarboxylic acid component, particularly polyethylene terephthalate (PET), are widely used for clothing and beverage bottles because of their excellent strength, barrier properties, and optical transparency. Therefore, the amount discarded after use is very large, and the processing method becomes a problem.
These phthalate plastics are often disposable, and establishment of recycling technology is desired in order to solve problems such as resource depletion and shortage of final disposal sites.
At present, the recycling of phthalic acid-based plastics is mainly a so-called material recycling method in which waste plastic is used again as a resin material for the same product or another plastic product. However, since this recycling method is expensive and the market size of recycled products is close to the limit, development of a new recycling technology is required.
As a recycling method of waste plastic, in addition to the above material recycling, it can be pyrolyzed at a high temperature to become a chemical raw material such as synthesis gas or cracked oil, or it can be chemically decomposed and converted back to a monomer, etc. There is so-called chemical recycling that is used in the process.
For example, as one of chemical recycling methods, a method of obtaining an aromatic hydrocarbon such as benzene, which is a chemical raw material by thermally decomposing PET and thermally decomposing PET is disclosed (for example, Patent Documents). 1).
In addition, a method is disclosed in which terephthalic acid, which is a raw material of PET, can be obtained by thermally decomposing PET using high-temperature water (see, for example, Patent Document 2).

However, in chemical recycling, from the viewpoint of whether the raw material obtained by pyrolysis is a substance that is closer to the raw material of the recycled product, or a substance that does not cause the problem of piping blockage in the apparatus during the pyrolysis reaction. Has not been able to provide a sufficiently satisfactory chemical recycling method.
Accordingly, the present invention provides a chemical recycling method capable of obtaining a substance that is a raw material capable of efficiently producing a recycled product and is less likely to cause problems such as blockage of piping in a thermal decomposition reactor. Objective.

Means for solving the problems are as follows. That is,
The chemical recycling method of the present invention includes:
An aromatic compound is obtained by thermally decomposing a phthalic acid plastic in the presence of a nickel catalyst.

  ADVANTAGE OF THE INVENTION According to this invention, the chemical recycling method which can obtain the substance used as the raw material which can produce | generate a recycled product efficiently, Comprising: It is hard to produce problems, such as obstruction | occlusion of piping in a thermal decomposition reaction apparatus, can be provided. .

FIG. 1 is a schematic view showing an example of a thermal decomposition reaction apparatus used in the present invention.

When PET is pyrolyzed by the method described in Patent Document 1, benzene is produced. However, in order to obtain a final product such as a polymer using benzene as a raw material, it is necessary to convert it into a precursor of the final product through a multistage reaction. In other words, when benzene is used as a raw material, the production efficiency of recycled products is poor. Therefore, a chemical recycling method that can generate a substance closer to the raw material of the recycled product is desired.
When PET is thermally decomposed by the method described in Patent Document 2, terephthalic acid, which is a raw material of PET, is generated. However, since terephthalic acid is a substance having a high melting point and sublimation properties, if it is produced in a large amount during the decomposition reaction, it will block the piping in the thermal decomposition reaction apparatus. Therefore, it is necessary to control the production amount of terephthalic acid.

(Chemical recycling method)
As described above, the chemical recycling method of the present invention includes a step of thermally decomposing a phthalic acid plastic in the presence of a nickel catalyst.
By the method of the present invention, it is possible to suppress the production of benzene and mainly produce terephthalic acid and benzoic acid. Furthermore, according to the present invention, since benzoic acid can be produced in a high yield, the amount of terephthalic acid produced can be suppressed to 30% by mass or less with respect to the obtained decomposition product, and the piping during the pyrolysis reaction can be reduced. The problem of blockage can be effectively prevented.
More specifically, the chemical recycling method of the present invention includes a step of mixing a phthalic plastic and a nickel catalyst, and a step of decomposing the phthalic plastic by heating the mixture obtained in the mixing step. Have.

<Nickel catalyst>
The nickel catalyst is not limited to pure nickel, but may be nickel oxide or nickel hydroxide. Further, it may be silica-supported nickel or alumina-supported nickel using a support such as silica or alumina.
Since nickel aggregates due to sintering when used alone, there is a concern about a decrease in surface area, that is, a decrease in active sites. Therefore, supported nickel that can increase the surface area, that is, increase the active points is preferable. The carrier is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably silica or alumina that is thermally and chemically stable and has no toxicity.
A nickel catalyst may be used individually by 1 type and may use 2 or more types together.
In addition to the nickel catalyst, another metal catalyst may be used, and these may be used in combination.

In the silica-supported nickel and the alumina-supported nickel, the BET specific surface areas of the silica support and the alumina support supporting nickel are not particularly limited and can be appropriately selected depending on the purpose. ^However, preferable to be 100m ² / g~700m 2 / ^g, more preferably a 300m ² / g~600m 2 / g.
If the specific surface area is small, the active point of the catalyst is reduced, and a sufficient catalytic effect cannot be obtained. Therefore, the production rate of terephthalic acid increases, which may cause clogging of the pipe. If it is too large, thermal decomposition proceeds excessively due to an excessive catalytic effect due to an increase in active sites, and an aromatic compound cannot be obtained sufficiently.
If the BET specific surface area of the support is 100 m ² / g or more, a sufficient catalytic effect can be obtained. If the BET specific surface area is 700 m ² / g or less, the thermal decomposition reaction proceeds excessively due to an excessive catalytic effect, and terephthalate The yield of acid and benzoic acid decreases, and the problem that benzene is produced can be effectively prevented.
The shape of the carrier is not particularly limited as long as the BET specific surface area is realized, and can be selected according to the purpose and reaction scale such as sphere, pellet, hollow, honeycomb, porous and the like.

In the present invention, the BET specific surface area can be measured as follows.
[Method for measuring BET specific surface area]
Using a fully automatic BET specific surface area measuring apparatus ("Macsorb Model-1201" manufactured by Mountec Co., Ltd.), the measurement is performed by the nitrogen adsorption one-point method. The measurement sample is pretreated by heating at 200 ° C. for 2 hours.

There is no restriction | limiting in particular as addition amount of the said silica carrying nickel catalyst, According to the objective, it can select suitably. However, the addition amount of the nickel catalyst is preferably 2% by mass to 40% by mass and more preferably 2% by mass to 30% by mass with respect to the phthalic acid-based plastic.
If the amount of the catalyst added is too small, the catalyst effect cannot be sufficiently obtained, so that the production rate of terephthalic acid increases and there is a possibility that the piping is blocked. When the amount is too large, thermal decomposition proceeds excessively due to an excessive catalytic effect, and a sufficient aromatic compound cannot be obtained.
When the addition amount of the silica-supported nickel catalyst is 2% by mass or more, the reaction rate can be prevented from being lowered, and the decomposition reaction can be performed efficiently. If the addition amount is 40% by mass or less, the thermal decomposition reaction proceeds excessively, and the production amount of gaseous components such as CO ₂ and benzene is increased, thereby effectively preventing the problem that aromatic compounds cannot be obtained sufficiently. be able to. Moreover, if it is 2 mass%-30 mass%, an aromatic compound can fully be obtained, suppressing the production amount of benzene.

<Phthalic acid plastic>
The phthalic acid plastic is not limited to a pure one, and each article containing the phthalic plastic as a main component can be used. Examples of raw materials for phthalic acid plastics include aromatic plastics containing aromatic dicarboxylic acid as the main dicarboxylic acid component.
Aromatic plastics include, for example, polyethylene terephthalate (PET) having ethylene terephthalate as the main repeating unit; poly (ethylene terephthalate / isophthalate); polytetramethylene terephthalate having tetramethylene terephthalate as the main repeating unit; 1,3-phenylene terephthalate And poly (1,3-phenylene terephthalate) having a main repeating unit.
These may be either homopolymers or copolymers, and the copolymer contains an aliphatic dicarboxylic acid such as adipic acid as a dicarboxylic acid component as long as the aromatic dicarboxylic acid is the main dicarboxylic acid component. May be.
The phthalic acid plastic may contain an additive. The additive is not particularly limited, and any known additive such as an antioxidant, a flame retardant, and a nucleating agent may be used.
Although the present invention is directed to phthalic plastics, it may contain materials other than phthalic plastics such as polyethylene, polypropylene, and polystyrene.

<Mixing process and pyrolysis process>
The thermal decomposition temperature can be appropriately set as long as it is a temperature at which the phthalic acid plastic can be thermally decomposed, but is preferably 300 ° C to 700 ° C, more preferably 350 ° C to 600 ° C. When the thermal decomposition temperature is 300 ° C. or higher, a thermal decomposition product can be generated, and an aromatic compound can be sufficiently recovered. On the other hand, if the thermal decomposition temperature is 700 ° C. or lower, the deoxygenation and dehydrogenation reactions proceed too much, increasing the amount of carbides and benzene produced, and the target aromatic compound cannot be sufficiently recovered. Can be effectively prevented.
If it is 350 to 600 degreeC, a phthalic acid type plastic will fuse | melt and it can contact the catalyst uniformly, and can suppress the reaction nonuniformity of a decomposition product.
There is no restriction | limiting in particular as a pressure at the time of thermal decomposition, Although it can select suitably according to the objective, Since the reaction nonuniformity of a decomposition product can be suppressed, it is preferable that it is a pressurized state. The pressurization may be performed by enclosing an inert gas in a reaction vessel which is a thermal decomposition reaction apparatus, or by keeping the gas generated by the thermal decomposition in the reaction vessel. The pressure can be controlled using a pressure relief valve.
The method for heating the pyrolysis tank in the pyrolysis reactor is not particularly limited as long as it can raise the temperature to a predetermined pyrolysis temperature and can maintain the temperature, and any known method can be used. be able to. For example, a burner method in which gas or liquid fuel is burned to use combustion heat, or electrical heating such as resistance heating, dielectric heating, or arc heating can be used.
A heat medium such as a liquid such as mineral oil or a powder such as sand may be mixed for the purpose of improving the thermal efficiency of the raw material compound during pyrolysis. When a heat medium is mixed, local heating can be prevented during the thermal decomposition reaction, and an effect of suppressing the formation of carbides can be obtained.
The pyrolyzate produced by the thermal decomposition can be recovered in a condensing tank after being vaporized. An exhaust pressure valve is connected to the condensing tank, and a gas component can be recovered using a Tedlar bag. The gaseous components include non-flammable gases such as carbon dioxide and flammable gases such as carbon monoxide, methane, and butane.
The cooling method of the condensing tank is not particularly limited as long as the pyrolyzate can be cooled, and uses an air cooling method using a cooling fan, a method using a cooling medium and a heat exchanger, and a Peltier effect. Any known method such as a cooling method for generating a temperature gradient from the voltage difference may be used.

<Aromatic compound produced>
The aromatic compound obtained by the thermal decomposition of the phthalic acid plastic by the chemical recycling method of the present invention is not particularly limited, for example, terephthalic acid, isophthalic acid, benzoic acid, benzene, toluene, biphenyl, toluic acid, etc. Is mentioned.
However, according to the present invention, the production of benzene can be suppressed, and mainly terephthalic acid and benzoic acid can be obtained.
When an aromatic compound is used as a raw material for a chemical product, for example, when polystyrene is produced using benzene as a raw material, it is necessary to synthesize ethylbenzene from benzene, styrene from ethylbenzene, and further pass through a polymerization reaction. Each reaction requires the supply of substances and energy other than benzene. In order to obtain a chemical product without going through such a multi-step reaction, it is necessary to obtain terephthalic acid and benzoic acid that can be directly used as raw materials for chemical products such as PET and sodium benzoate as an additive. preferable.
According to the present invention, production of benzene can be suppressed, and terephthalic acid and benzoic acid can be mainly produced. The method of the present invention is a more practical chemical recycling method in that a substance closer to the raw material of the recycled product can be generated.
Furthermore, in the present invention, benzoic acid can be obtained in a higher yield, and the production rate of terephthalic acid can be suppressed to 30% or less with respect to the obtained decomposition product.
Since terephthalic acid has a high melting point and a sublimation property, when it is contained in a large amount in the pyrolysis product, there is a risk of blocking the piping of the pyrolysis reactor. Therefore, it is preferable to produce benzoic acid having a relatively low melting point. The amount of terephthalic acid produced is not particularly limited as long as the pipe is not clogged. However, when a piping blockage occurs, there is a risk that the device may explode due to the ignition of flammable gas generated by pyrolysis.Therefore, the generation amount that does not easily cause piping blockage, that is, the content in the pyrolysis product is small. It is preferable that it is 30% or less.
The method of the present invention in which benzoic acid having a relatively low melting point is obtained in a higher yield is a chemical recycling method that can effectively prevent the problem of clogging of piping during the thermal decomposition reaction.

<Decomposition product to be produced>
When the chemical recycling method of the present invention is applied to a phthalic acid plastic, the production of benzene can be suppressed. In addition, terephthalic acid and benzoic acid are produced in a preferable balance. By increasing the production of benzoic acid, the amount of terephthalic acid produced is suppressed to such an extent that the piping is not likely to be clogged.
When a phthalic acid plastic is thermally decomposed, the resulting decomposition product contains aromatic compounds such as terephthalic acid, benzoic acid, biphenyl, toluic acid, and benzene, gas, residue, volatile matter, and other components.
When the phthalic acid plastic is pyrolyzed by the chemical recycling method of the present invention, the structure of the resulting decomposition product of the present invention is as follows.
The decomposition product of the present invention includes an aromatic compound of terephthalic acid and benzoic acid.
In the decomposition product of the present invention, the proportion of benzene is 5% by mass or less. More preferably, it is 1 mass% or less, More preferably, it is below a detection limit value (0.05 mass%).
In the decomposition product of the present invention, the proportion of terephthalic acid is 30% by mass or less. More preferably, it is in the range of 20% by mass or more and less than 25% by mass.
In the decomposition product of the present invention, when the proportion of terephthalic acid is in the range of 20% by mass or more and less than 25% by mass, or the proportion of benzoic acid is 10% by mass or more, terephthalic acid and benzoic acid The production amount is well balanced and more preferable.

Examples of the present invention will be described below, but the present invention is not limited to the following examples.
PET was used for the phthalic acid plastic to be thermally decomposed, and the apparatus shown in FIG. 1 was used as the thermal decomposition reaction apparatus. In FIG. 1, reference numeral X denotes a sample / catalyst, reference numeral 1 denotes a thermal decomposition tank, reference numeral 2 denotes an electric furnace, reference numeral 3 denotes a stirrer, reference numeral 4 denotes a condensing tank, reference numeral 5 denotes an exhaust pressure valve, reference numeral 6. Indicates Tedlar back.

(Production Example 1)
<Adjustment of Ni / SiO ₂ -1>
In a 200 mL beaker, 1.5 parts by mass of nickel (II) formate dihydrate and 98.5 parts by mass of pure water were weighed, heated to 80 ° C. and dissolved to obtain a 0.08 mol / L nickel formate aqueous solution. Add 96 parts by mass of nickel formate aqueous solution and 4 parts by mass of silica gel (BET specific surface area 300 m ² / g, particle size 40-75 μm) to a 300 mL eggplant flask, impregnate at 80 ° C. for 6 hours, and then dry by vacuum distillation. The dried product was dried at 120 ° C. for 6 hours.
The catalyst prepared above was sealed in a tubular electric furnace and sintered at 550 ° C. for 2 hours in a nitrogen atmosphere. After sintering, the gas in the system was changed to hydrogen and reduced at 500 ° C. for 2 hours to obtain silica-supported nickel Ni / SiO ₂ -1.

(Production Example 2)
<Adjustment of Ni / SiO ₂ -2>
Except that silica gel (BET specific surface area 300 meters ² / g, particle size 40～75Myuemu) Production Example 1 was changed to silica gel (BET specific surface area 300 meters ² / g, particle size 75-150) in a similar manner, a silica supported nickel Ni / SiO ₂ -2 was obtained.

(Production Example 3)
<Preparation of Ni / _SiO 2 -3>
In the same manner as in Production Example 1, except that silica gel (BET specific surface area 300 m ² / g, particle size 40 to 75 μm) was replaced with silica gel (BET specific surface area 550 m ² / g, particle size 75 to 150 μm), silica-supported nickel Ni / SiO ₂ -3 was obtained.

(Production Example 4)
<Adjustment of Ni / SiO ₂ -4>
In the same manner as in Production Example 1, except that silica gel (BET specific surface area 300 m ² / g, particle size 40 to 75 μm) was replaced with silica gel (BET specific surface area 700 m ² / g, particle size 75 to 150 μm), silica-supported nickel Ni / SiO ₂ -4 was obtained.

(Production Example 5)
<Preparation of Ni / _SiO 2 -5>
In the same manner as in Production Example 1, except that silica gel (BET specific surface area 300 m ² / g, particle size 40 to 75 μm) was replaced with silica gel (BET specific surface area 80 m ² / g, particle size 40 to 75 μm), silica-supported nickel Ni / to obtain a _SiO 2 -5.

(Production Example 6)
<Adjustment of Ni / Al ₂ O ₃ >
In the same manner as in Production Example 1, except that silica gel (BET specific surface area 300 m ² / g, particle size 40 to 75 μm) was changed to alumina (BET specific surface area 200 m ² / g, particle size 75 μm), alumina-supported nickel Ni / Al ₂ O ₃ was obtained.

Example 1
In a thermal decomposition reaction apparatus equipped with a condenser and a Tedlar bag, 30 g of PET and 5 mass% of Ni / SiO ₂ -1 were encapsulated in a mass part of PET and reacted at 350 ° C. for 1 hour. Immediately after completion of the reaction, the reaction product was air-cooled, and the decomposition product was collected in a coagulation tank, a thermal decomposition tank, and a Tedlar bag.
The decomposition products collected in the coagulation tank and the thermal decomposition tank were extracted with acetone, and the acetone soluble components were qualitatively and quantitatively analyzed by GC-FID and GC-MS. Acetone insolubles were extracted with an aqueous sodium hydroxide solution and subjected to solid-liquid separation. The solid phase was a residue, and the precipitate formed by adding hydrochloric acid to the liquid phase was collected as terephthalic acid (TPA).
Table 1 below shows the results of qualitative and quantitative analysis by GC-FID and GC-MS of the catalyst of Example 1, thermal decomposition temperature conditions, and the obtained decomposition product.

The evaluation criteria for terephthalic acid (TPA), benzoic acid, and benzene in the quantitative results in Table 1 are as follows.
If the proportion of terephthalic acid (TPA) in the decomposition product is 30% by mass or more, the piping may be blocked. Further, if the proportion of terephthalic acid is less than 5% by mass, the proportion of other aromatic compounds, particularly benzene, is not preferable. On the other hand, when the proportion of terephthalic acid is 20% by mass or more and less than 25% by mass, the production amount balance with benzoic acid is good and the most preferable. Considering the balance of the amount of production between aromatic compounds such as terephthalic acid, benzoic acid and benzene, the evaluation criteria were set as follows.

<< Terephthalic acid (TPA) >>
: 20% by mass or more and less than 25% by mass ○: 15% by mass or more and less than 20% by mass or 25% by mass or more and less than 30% by mass Δ: 5% by mass or more and less than 15% by mass ×: Less than 5% by mass or 30% by mass or more

<< benzoic acid >>
◎: 10% by mass or more and less than 25% by mass ○: 5% by mass or more and less than 10% by mass or 25% by mass or more and less than 30% by mass Δ: Less than 5% by mass ×: Not detected

<< benzene >>
○: not detected (detection limit (0.05% by mass)) or less Δ: measurable value or more and less than 5% by mass ×: 5% by mass or more

(Example 2)
In Example 1, a decomposition product was obtained in the same manner as in Example 1 except that the reaction temperature was changed from 350 ° C to 400 ° C. The analysis results of the obtained decomposition products are shown in Table 1 below.

(Example 3)
In Example 1, except for changing the Ni / _SiO 2 -1 to Ni / _SiO 2 -2 was obtained decomposition product in the same manner as in Example 1. The analysis results of the obtained decomposition products are shown in Table 1 below.

(Example 4)
A decomposition product was obtained in the same manner as in Example 1 except that Ni / SiO ₂ -1 was replaced with Ni / SiO ₂ -3 in Example 1. The analysis results of the obtained decomposition products are shown in Table 1 below.

(Example 5)
A decomposition product was obtained in the same manner as in Example 1 except that Ni / SiO ₂ -1 was replaced with Ni / SiO ₂ -4 in Example 1. The analysis results of the obtained decomposition products are shown in Table 1 below.

(Example 6)
In Example 1, a decomposition product was obtained in the same manner as in Example 1 except that Ni / SiO ₂ -1 was replaced with Ni / Al ₂ O ₃ . The analysis results of the obtained decomposition products are shown in Table 1 below.

(Example 7)
In Example 1, a decomposition product was obtained in the same manner as in Example 1 except that the addition amount of Ni / SiO ₂ -1 was changed from 5% by mass to 2% by mass. The analysis results of the obtained decomposition products are shown in Table 1 below.

(Example 8)
In Example 1, a decomposition product was obtained in the same manner as in Example 1 except that the addition amount of Ni / SiO ₂ -1 was changed from 5% by mass to 10% by mass. The analysis results of the obtained decomposition products are shown in Table 1 below.

Example 9
In Example 1, a decomposition product was obtained in the same manner as in Example 1 except that the addition amount of Ni / SiO ₂ -1 was changed from 5% by mass to 20% by mass. The analysis results of the obtained decomposition products are shown in Table 1 below.

(Example 10)
In Example 1, a decomposition product was obtained in the same manner as in Example 1 except that the addition amount of Ni / SiO ₂ -1 was changed from 5% by mass to 30% by mass. The analysis results of the obtained decomposition products are shown in Table 1 below.

(Example 11)
In Example 1, a decomposition product was obtained in the same manner as in Example 1 except that the addition amount of Ni / SiO ₂ -1 was changed from 5% by mass to 40% by mass. The analysis results of the obtained decomposition products are shown in Table 1 below.

(Example 12)
In Example 1, a decomposition product was obtained in the same manner as in Example 1 except that the addition amount of Ni / SiO ₂ -1 was changed from 5% by mass to 50% by mass. The analysis results of the obtained decomposition products are shown in Table 1 below.

(Example 13)
In Example 1, a decomposition product was obtained in the same manner as in Example 1 except that Ni / SiO ₂ -1 was replaced with nickel alone. The analysis results of the obtained decomposition products are shown in Table 1 below.

(Example 14)
A decomposition product was obtained in the same manner as in Example 1 except that Ni / SiO ₂ -1 was replaced with Ni / SiO ₂ -5 in Example 1. The analysis results of the obtained decomposition products are shown in Table 1 below.

(Comparative Example 1)
In Example 1, a decomposition product was obtained in the same manner as in Example 1 except that Ni / SiO ₂ -1 was not added. The analysis results of the obtained decomposition products are shown in Table 1 below.

(Comparative Example 2)
In Example 1, Ni / SiO ₂ -1 was decomposed in the same manner except that Ca (OH) ₂ was added, the addition amount was changed from 5% by mass to 50% by mass, and the reaction temperature was changed from 350 ° C. to 700 ° C. I got a thing. The analysis results of the obtained decomposition products are shown in Table 1 below.

From the result of the said Example, when the nickel catalyst was used, the production | generation of benzene was suppressed and it has confirmed that benzoic acid could be collect | recovered with a high yield. The amount of terephthalic acid (TPA) produced can be suppressed to 30% by mass or less with a low possibility of pipe clogging.
On the other hand, in Comparative Example 1 using no catalyst, although TPA and benzoic acid are produced, the amount of TPA produced exceeds 30% by mass, and there is a high risk of clogging the piping during the thermal decomposition reaction. It was a thing.
Further, in the case of Comparative Example 2 similar to the method of “decomposing at a high temperature of 600 ° C. to 900 ° C. in the presence of calcium hydroxide” described in Patent Document 1, a large amount of benzene was produced. TPA and benzoic acid were not obtained.

  As described above, according to the present invention, a substance that is a raw material capable of efficiently generating a recycled product and that is unlikely to cause problems such as blockage of piping in the thermal decomposition reaction apparatus is generated in a high yield. Can do.

Aspects of the present invention are as follows, for example.
<1> A chemical recycling method for phthalic acid plastics, wherein an aromatic compound is obtained by thermally decomposing phthalic acid plastics in the presence of a nickel catalyst.
<2> The chemical recycling method for a phthalic acid plastic according to <1>, wherein the nickel catalyst contains at least one of silica-supported nickel, alumina-supported nickel, and nickel.
<3> The nickel catalyst contains supported nickel that is at least one of silica-supported nickel and alumina-supported nickel,
The BET specific surface area of the carrier in the supported nickel ^is a chemical recycling process of phthalate-based plastic according to the a ^{100m 2 / g~700m 2 / g <} 2>.
<4> The phthalic acid plastic chemical according to any one of <1> to <3>, wherein the addition amount of the silica-supported nickel catalyst is 2% by mass to 40% by mass with respect to the phthalic acid plastic. Recycling method.
<5> A composition containing terephthalic acid and benzoic acid,
In the composition, the proportion of benzene is 5% by mass or less, and the proportion of terephthalic acid is 30% by mass or less.
<6> The composition according to <5>, wherein the proportion of terephthalic acid in the composition is 20% by mass or more and less than 25% by mass, or the proportion of benzoic acid is 10% by mass or more. It is.
<7> The composition according to any one of <5> to <6>, wherein the composition is a thermal decomposition product of a phthalic acid plastic.

  According to the chemical recycling method according to any one of <1> to <4> and the composition according to any one of <5> to <7>, the conventional problems are solved, and the book The object of the invention can be achieved.

Japanese Patent No. 4565223 Japanese Patent No. 5099416

Claims (7)

  A chemical recycling method for phthalic acid plastics, characterized in that an aromatic compound is obtained by thermally decomposing phthalic acid plastics in the presence of a nickel catalyst.   2. The chemical recycling method for a phthalic acid plastic according to claim 1, wherein the nickel catalyst contains at least one of silica-supported nickel, alumina-supported nickel, and nickel. The nickel catalyst contains supported nickel that is at least one of silica-supported nickel and alumina-supported nickel;
The BET specific surface area of the carrier in the supported ^nickel, 100m ² / ^g~700m 2 / g a chemical recycling process of phthalate-based plastic according to claim 2.   4. The chemical recycling method for a phthalic acid plastic according to claim 1, wherein an addition amount of the silica-supported nickel catalyst is 2% by mass to 40% by mass with respect to the phthalic acid plastic. A composition containing terephthalic acid and benzoic acid,
The composition which the ratio for which benzene accounts among the said compositions is 5 mass% or less, and the ratio for which a terephthalic acid accounts is 30 mass% or less.   The composition according to claim 5, wherein the proportion of terephthalic acid in the composition is 20% by mass or more and less than 25% by mass, or the proportion of benzoic acid is 10% by mass or more.   The composition according to any one of claims 5 to 6, which is a thermal decomposition product of a phthalic acid plastic.