Benzene production method

Abstract

To provide a manufacturing method of benzene, capable of obtaining benzene which is a low molecular hydrocarbon in high yield by heat decomposition and desulfurization reaction of PPS.SOLUTION: A manufacturing method of benzene includes a step of obtaining a reaction product including benzene by bringing a polyphenylene sulfide resin into contact with a zeolite catalyst for heat decomposition and desulfurization reaction of the polyphenylene sulfide resin, wherein the manufacturing method of benzene is characterized by that the zeolite catalyst is a proton exchange type zeolite and a molar ratio of SiO2 and Al2O3, (SiO2 / Al2O3 ratio), is 5-100.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing benzene by thermally decomposing a polyphenylene sulfide resin. [Background technology]

[0002] Polyphenylene sulfide (PPS) resin is a super engineering plastic used as a replacement for metal components to reduce the weight and increase electronics in automobiles. In recent years, automobile development has become more fuel-efficient and autonomous, and PPS demand is expected to grow further. This trend is expected to lead to an increase in PPS waste, but no clear disposal method has yet been established. Currently, PPS is incinerated as a component of automobile shredder residue (ASR). However, concerns remain about the sulfur content of PPS, which could damage incinerators. As the proportion of PPS components in automobiles increases, disposal may become less viable. Furthermore, recent global regulations and agreements regarding plastic waste require effective recycling and other uses for PPS waste, but no established method has yet been established. One method of recycling plastics is chemical recycling through oil-gasification. In the oil-gasification process, waste plastics are converted into low-molecular-weight hydrocarbons through thermal decomposition, and many methods using solid catalysts to improve reactivity and product selectivity have been investigated (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2019-527758 Summary of the Invention [Problem to be solved by the invention]

[0004] However, there is no information about thermal decomposition of PPS, which has sulfur sulfide bonds, using a solid catalyst. Generally, the thermal decomposition reaction of PPS requires high temperatures, and there are problems such as the production of various compounds and sulfur compounds, so the recycling of PPS has not been sufficiently studied. Therefore, an object of the present invention is to provide a method for producing benzene, a low-molecular-weight hydrocarbon, from PPS in high yield by subjecting it to thermal decomposition and desulfurization reactions.Another object of the present invention is to provide a method for recycling PPS, which can effectively recycle PPS waste by subjecting PPS to thermal decomposition and desulfurization reactions to produce benzene in high yield. [Means for solving the problem]

[0005] As a result of extensive research into solving the above problems, the inventors discovered that the above problems can be solved by using a specific solid catalyst when pyrolyzing PPS, and thus completed the present invention.

[0006] That is, the present invention includes the following aspects. [1] A method for producing benzene, comprising the step of contacting a polyphenylene sulfide resin with a zeolite catalyst to obtain a reaction product containing benzene through thermal decomposition and desulfurization of the polyphenylene sulfide resin, The zeolite catalyst is a proton-exchanged zeolite, and has a molar ratio of SiO2 to Al2O3 (SiO2 / Al2O3 ratio) of 5-100. [2] The method for producing benzene according to [1], wherein the thermal decomposition and desulfurization reactions are carried out under a temperature condition of 500 to 700°C. [3] The method for producing benzene according to [1] or [2], wherein the zeolite catalyst is a ZSM-5 type zeolite catalyst. [4] A method for recycling polyphenylene sulfide resin, comprising the step of contacting polyphenylene sulfide resin or waste plastics containing polyphenylene sulfide resin with a zeolite catalyst to obtain a reaction product containing benzene through thermal decomposition and desulfurization of the polyphenylene sulfide resin, The method for recycling a polyphenylene sulfide resin, wherein the zeolite catalyst is a proton-exchanged zeolite and has a molar ratio of SiO2 to Al2O3 (SiO2 / Al2O3 ratio) of 5-100. [Effects of the Invention]

[0007] The present invention provides a method for producing benzene, a low-molecular-weight hydrocarbon, from PPS in high yield through thermal decomposition and desulfurization. Furthermore, by subjecting PPS to thermal decomposition and desulfurization to produce benzene in high yield, it is also possible to provide a method for recycling PPS, which allows for the effective recycling of PPS waste. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing the structural formula of a compound that was the subject of the selectivity measurement in Example 1, among the reaction products produced by the thermal decomposition reaction in Example 1. [Figure 2] FIG. 1 is a schematic diagram illustrating the reaction mechanism of the thermal decomposition and desulfurization reaction of PPS in the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0009] The present invention will be described in detail below. Note that the following explanation of the constituent elements is an example for explaining the present invention, and the present invention is not limited to these contents.

[0010] (Benzene manufacturing method) The method for producing benzene of the present invention includes a step of contacting a polyphenylene sulfide (PPS) resin with a zeolite catalyst to thermally decompose and desulfurize the polyphenylene sulfide resin to obtain a reaction product containing benzene. The zeolite catalyst is a proton-exchanged zeolite having a molar ratio of SiO2 to Al2O3 (SiO2 / Al2O3 ratio) of 5 to 100. By using the above-mentioned specific zeolite catalyst in the PPS thermal decomposition reaction, the present invention can lower the temperature required for the PPS decomposition reaction and obtain benzene in high yield (improving benzene selectivity) due to the desulfurization effect.

[0011] <Polyphenylene sulfide (PPS) resin> The PPS resin used in the present invention is a polymer containing p-phenylene sulfide as a main structural unit, and may contain phenylene sulfide sulfone units or phenylene sulfide ketone units in addition to p-phenylene units, and may be a random copolymer, a block copolymer, or a mixture thereof. The form of the PPS resin is not particularly limited, and may be powder, granules, pellets, fibers, films, molded products, or the like.

[0012] <Zeolite catalyst> Zeolite is a general term for crystalline aluminum silicon salts. The zeolite used in the present invention is a proton-exchanged zeolite. In other words, protons (H + ) is introduced, and hydrogen ions (H + ) is a zeolite containing Examples of the zeolite framework structure include various types of zeolites such as ZSM-5 type, beta type, mordenite type, Y type, ferrierite type, etc. Among these zeolites, it is more preferable to use ZSM-5 type zeolite in the present invention. These zeolites may be used alone or in combination of two or more.

[0013] The zeolite used in the present invention may be commercially available, and examples of such zeolites include HSZ (registered trademark) manufactured by Tosoh Corporation, such as 840HOA and 822HOA of the HSZ-800 series, 931HOA of the HSZ-900 series, 620HOA and 660HOA of the HSZ-600 series, and 330HUA, 331HSA, and 350HUA of the HSZ-300 series. Of these, 840HOA of the HSZ-800 series is more preferred.

[0014] Furthermore, the zeolite used in the present invention has a molar ratio of SiO2 to Al2O3 (SiO2 / Al2O3 ratio) of 5 to 100, but the SiO2 / Al2O3 ratio is preferably 5 to 50, more preferably 10 to 45, and even more preferably 10 to 40.

[0015] The SiO2 / Al2O3 ratio of a zeolite can be measured using X-ray fluorescence analysis (XRF). Generally, proton-exchanged zeolites act as solid acid catalysts, and it is known that the greater the number of acid sites, which can be measured by ammonia temperature-programmed desorption (NH3-TPD), the greater the catalytic effect. Zeolites have a higher number of acid sites when the SiO2 / Al2O3 ratio is low, but conversely, the number of acid sites decreases below a certain SiO2 / Al2O3 ratio, so there is an optimal range for the SiO2 / Al2O3 ratio.

[0016] Furthermore, it is generally known that the activity of a solid catalyst is proportional to its specific surface area, and the specific surface area of ​​a solid is inversely proportional to its particle size. Therefore, the zeolite used in the present invention preferably has an average particle size of less than 100 μm, more preferably less than 50 μm, and even more preferably less than 15 μm.

[0017] <Temperature conditions for pyrolysis and desulfurization> The thermal decomposition and desulfurization reaction of PPS is preferably carried out under temperature conditions of 500 to 700°C. As will be shown in the examples below, in the present invention, by using a specific zeolite during the thermal decomposition of PPS, it is possible to proceed with the thermal decomposition and desulfurization reaction of PPS even at a relatively low temperature of 500°C, and to produce benzene in a high yield.

[0018] In the thermal decomposition and desulfurization reaction steps, the amount of zeolite catalyst used relative to the PPS resin is preferably 100 parts by mass of PPS resin: 100 to 1000 parts by mass of zeolite catalyst.

[0019] <Products of thermal decomposition and desulfurization> According to the present invention, products obtained by the thermal decomposition and desulfurization reaction of PPS include, for example, 1. benzene, 2. benzenethiol, 3. benzenedithiol, 4. diphenyl sulfide, and 5. (4-thio)diphenyl sulfide, as shown in FIG. 1. These products are believed to be obtained, for example, via the reaction mechanism shown in FIG. As shown in the examples of Comparative Examples 1 to 3 below in which no catalyst is used, (4-thio)diphenyl sulfide (5) and benzenethiol (2) in FIG. 2 can be obtained in some amounts by thermal decomposition of PPS. However, in Examples 1 to 3 below, the amounts of symbol 5. (4-thio)diphenyl sulfide and symbol 2. benzenethiol are reduced, and the amounts of symbol 4. diphenyl sulfide and symbol 1. benzene are increased. This is thought to be due to the effect of the specific catalyst used in the present invention, which promoted desulfurization of the terminal thiol group from compound 5 to compound 4 and from compound 2 to compound 1. Furthermore, it is believed that the production of diphenyl sulfide (4) and benzene (1) from PPS is also due to the effect of the specific catalyst used in the present invention. It is presumed that the acid sites of the zeolite selectively desulfurized the sulfide bonds (-S-) of the PPS, cleaving the sulfide bonds and producing benzene in high yield. Thus, it is believed that when PPS is thermally decomposed using the specific zeolite catalyst specified in the present invention, the desulfurization effect can be promoted and the decomposition property can be improved, which further promotes the conversion of PPS into lower molecular weight compounds and makes it possible to efficiently produce benzene.

[0020] (How to recycle PPS) As described above, when PPS is thermally decomposed using the specific zeolite catalyst specified in the present invention, benzene, a low-molecular-weight hydrocarbon, can be obtained in high yield. Therefore, by using the PPS thermal decomposition and desulfurization reaction steps described above in the section "Benzene Production Method," an effective method for recycling PPS can be provided. In other words, by bringing polyphenylene sulfide resin or waste plastics containing polyphenylene sulfide resin into contact with the specific zeolite catalyst defined in the present invention to thermally decompose and desulfurize the PPS, benzene can be obtained in high yield, providing an effective method for recycling polyphenylene sulfide resin. [Example]

[0021] The contents and effects of the present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these. In the following, "parts" means "parts by mass."

[0022] (Examples 1 to 3) The pyrolysis reaction was carried out using a pyrolysis apparatus (Frontier Labs) combined with a gas chromatography mass spectrometer (Agilent Technologies). 0.2 mg of powdered polyphenylene sulfide resin was placed in an inactive stainless steel cup specifically designed for use in a pyrolysis apparatus, and 2.0 mg of solid catalyst was placed in the cup so as to cover the resin sample. The cup containing the sample was placed in the sample introduction section of the pyrolysis device, and after the reaction section of the pyrolysis device was heated to the reaction temperature, the sample cup was introduced into the reaction section. The resin sample was instantly heated, causing a catalytic pyrolysis reaction with the solid catalyst, and the pyrolysis products were entrained in the carrier gas. After splitting, the pyrolysis products were introduced into a gas chromatograph mass spectrometer along with the carrier gas, where the components were identified and quantified. The solid catalyst used was proton-exchanged ZSM-5 zeolite (HSZ-840HOA manufactured by Tosoh Corporation, SiO2 / Al2O3 ratio (molar ratio) = 40, average particle size: 10 μm), and the reaction was carried out at temperatures of 500°C, 600°C, and 700°C. Of the pyrolysis products obtained, the structural formulas of the low molecular weight compounds confirmed in this example are shown in Figure 1. The conditions of the example and the selectivities of the confirmed compounds are shown in Table 1. Benzene was obtained with high selectivity under all temperature conditions, confirming the effectiveness of the catalyst in reducing molecular weight and desulfurization.

[0023] (Comparative Examples 1 to 7) The thermal decomposition reaction of polyphenylene sulfide resin was carried out in the same manner as in Example 1, except that the catalyst conditions were changed. In Comparative Examples 1 to 3, the reaction temperatures were 500°C, 600°C, and 700°C without using a catalyst, and in Examples 4 and 5, magnesium oxide, calcium oxide, titanium oxide, and proton-exchanged ZSM-5 zeolite (HSZ-890HOA manufactured by Tosoh Corporation, SiO2 / Al2O3 ratio (molar ratio) = 1500) were used as solid catalysts at a reaction temperature of 600°C. The experimental conditions and the selectivities of the confirmed compounds are shown in Table 1. The comparative examples showed lower benzene selectivity than the examples under all conditions. It was also found that even with proton-exchanged ZSM-5 zeolite, the effects of the present invention cannot be obtained unless the SiO2 / Al2O3 ratio is within the desired range specified in the present invention.

[0024] [Table 1] In Table 1, "Nocat" means no catalyst.

[0025] The above results confirmed that by using a specific zeolite catalyst in the PPS thermal decomposition reaction, the decomposition and desulfurization reactions can be carried out effectively even at a relatively low temperature of 500°C, and that the desulfurization effect makes it possible to obtain benzene in high yield (improving benzene selectivity).

Claims

1. A method for producing benzene, comprising the step of contacting a polyphenylene sulfide resin with a zeolite catalyst to obtain a reaction product containing benzene through thermal decomposition and desulfurization of the polyphenylene sulfide resin, wherein the zeolite catalyst is a proton-exchanged zeolite and is a catalyst containing SiO ２ and Al ２ O ３ The molar ratio (SiO ２ / Al ２ O ３ The method for producing benzene, wherein the ratio of the benzene to the carbonyl group is 5 to 100.

2. The method for producing benzene according to claim 1, wherein the thermal decomposition and desulfurization reactions are carried out under a temperature condition of 500 to 700°C.

3. 3. The method for producing benzene according to claim 1, wherein the zeolite catalyst is a ZSM-5 type zeolite catalyst.

4. A method for recycling polyphenylene sulfide resin, comprising the steps of contacting polyphenylene sulfide resin or waste plastics containing polyphenylene sulfide resin with a zeolite catalyst to obtain a reaction product containing benzene through thermal decomposition and desulfurization of the polyphenylene sulfide resin, The zeolite catalyst is a proton-exchanged zeolite and is SiO ２ and Al ２ O ３ The molar ratio (SiO ２ / Al ２ O ３ A method for recycling polyphenylene sulfide resin, wherein the ratio of the total amount of polyphenylene sulfide resin to the total amount of polyphenylene sulfide resin is 5 to 100.

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