KR100541039B1 - Recovery method of styrene monomer from waste expanded polystyrene containing flame retarding agent - Google Patents

Abstract

The present invention relates to a method for recovering styrene monomer from waste polystyrene containing a flame retardant, and more particularly, in a method for recovering styrene monomer by pyrolysing waste polystyrene in the presence of a catalyst, particularly waste polystyrene containing a conventional flame retardant. Side reaction problem due to decomposition of flame retardant by using Bronsted basic acid catalyst instead of metal oxide catalyst which produces bromic acid and bromine-containing compounds in pyrolysis reaction, reducing the yield of styrene monomer and producing toluene, ethylbenzene, etc. Recovery of styrene monomer from polystyrene containing flame retardant improves the economics by recycling the conventionally discarded waste into a more value-added recycling method by recovering high yield of styrene monomer. It is about a method.

Waste Polystyrene, Styrene Monomer, Pyrolysis Reaction, Catalyst, Brenstead Base

Description

Recovery method of styrene monomer from waste expanded polystyrene containing flame retarding agent}             

 1 shows an apparatus for producing styrene by pyrolysing waste polystyrene in the presence of a catalyst according to the present invention.

[Description of main parts of drawing]

 1. heating furnace 2. pyrolysis reactor 3. temperature measuring instrument

 4. Agitator 5. Condenser 6. Oil collector

 7. Photoion Detector

The present invention relates to a method for recovering styrene monomer from waste polystyrene containing a flame retardant, and more particularly, in a method for recovering styrene monomer by pyrolysing waste polystyrene in the presence of a catalyst, particularly waste polystyrene containing a conventional flame retardant. In the pyrolysis of methylene, bromine and bromine-containing compounds are used to reduce the yield of styrene monomers, and side reactions due to decomposition of flame retardants are carried out using catalysts having a strong Brenstead basicity instead of metal oxide catalysts that produce toluene and ethylbenzene. By recovering high yields of styrene monomers by improving the problem, the conventionally discarded wastes can be recycled in higher value-added recycling methods to improve the economics, and the styrene monomers from polystyrene containing flame retardants have also improved environmental problems. It is about collection method .

In recent years, waste polystyrene is generated in Korea by the use of 300,000 tons of electronic products, packaging materials, boxes, cushioning materials, food plates, and cold storage containers, which are recycled in the manufacture of recycled resins, lightweight concrete, and adhesives. .

However, the recycling is recycled using a physical method, the added value is very low and a large amount of waste polystyrene is generated that can not be recycled after repeated regeneration.

In addition, a large amount of waste foam polystyrene emitted from the agricultural and fish market or construction waste is not clean compared to other waste polystyrene, so it is difficult to use a physical regeneration method.

In particular, the waste is about 50 times more than that of other wastes, and the landfill or physical recycling is difficult to be disposed of by landfill or incineration, but the incineration method causes serious environmental problems due to the generation of dioxins.

Therefore, by recovering and recycling the raw materials such as styrene monomer through the recovery method of chemically treating the waste polystyrene as described above, the economic efficiency can be greatly improved, which is a very valuable method in terms of resource circulation.

This chemical method was first attempted by Nishizaki in 1997 to recover polystyrene from styrene monomer. The method has been reported that about 50% of the styrene monomer can be recovered from the polystyrene by pyrolysis at a temperature of 733 ° K. The action of the catalyst has been examined and developed as a method for increasing the yield of the styrene monomer.

As a method of using the catalyst, a technique for recovering styrene using sulfate (Korean Patent No. 2001-0087093), a binary catalyst prepared by supporting a basic catalyst on silica and alumina with a metal oxide as a main catalyst Technology (Korean Patent No. 2002-200074) has been reported. In addition, studies on the recovery of styrene from polystyrene have been published in the literature by many researchers, and in particular, Ueno of Japan has proposed a reaction mechanism as follows [Ind. Eng. Chem. Res. 34, 4515 (1995).

First, when metal oxides such as Co ₃ O ₄ , Fe ₂ O ₃ , Cr ₂ O ₃ , and CuO, which are highly acidic, are used as catalysts, styrene and dimer are bonded to polystyrene by the help of a catalyst, as shown in Scheme 1. Carbocation is generated by the cleavage of, and the pyrolysis reaction proceeds as the styrene is serially separated. However, since carbo cations are unstable due to lack of two electrons, they cause side reactions such as attacking surrounding benzene rings, resulting in a poor yield of styrene monomer.

On the other hand, in the case of using a basic catalyst such as BaO, K ₂ O, MgO, ZnO, CaO, as shown in Scheme 2, the octet law is satisfied to produce a stable carboanion without an electron shortage state. The pyrolysis reaction proceeds as the styrene is serially separated. Since the side reactions are reduced based on the stability of the carboanion, the production of oil is increased due to the reduction of heavy oil, and the yield of styrene monomer contained in the oil is greatly increased.

However, in the case of the waste polystyrene containing no flame retardant, the results of the previous studies were in agreement. However, when the flame retardant is contained in the polystyrene, the existing catalysts are activated by bromic acid and bromine-containing compounds produced by pyrolysis of the flame retardant. Because of this interference, the yield of styrene monomer is decreased and byproducts such as toluene and ethylbenzene are greatly increased, and thus, development of a method for treating waste polystyrene and a polystyrene recovery containing a flame retardant is very necessary.

The inventors of the present invention have made efforts to improve side reaction problems caused by bromic acid and bromine-containing compounds produced by pyrolysis of flame retardants even when using catalysts in waste polystyrene containing flame retardants. By using a basic catalyst having a strong Bendstead basicity, the catalyst assists in the production of carboanions, inactivates pyrolysates of flame retardants or flame retardants and promotes pyrolysis reactions, thereby increasing the content and recovery of commercially useful styrene monomers. The purpose is to provide a recovery method that greatly improves the

It is another object of the present invention to provide a pyrolysis catalyst for recovering styrene monomer, which is used for recovering styrene monomer by pyrolysing waste polystyrene.

The present invention is a method for recovering styrene monomer by pyrolyzing waste polystyrene containing a flame retardant,
The catalyst for simultaneously decomposing the waste polystyrene and the flame retardant is selected from hydrates, carbonates, phosphates and borate salts of Na and K having an aqueous solution of Brested bases of 8 to 14, and the pyrolysis reaction is carried out at a temperature of 200 to 1000 ° C. It is characterized by the process of styrene monomer from waste polystyrene containing a flame retardant carried out over time.

The present invention will be described in detail as follows.

The present invention relates to a method for recovering styrene monomer from waste polystyrene by pyrolysis in the presence of a catalyst, wherein a flame retardant which reduces the selectivity of a conventional catalyst by using a Brensted basic catalyst in place of an existing acid or basic metal oxide catalyst is disclosed. The present invention relates to a method for recovering styrene monomer in a high yield from polystyrene.

As the catalyst used to efficiently recover the styrene monomer in the present invention, the Brentstead base is also in an aqueous solution of 8 to 14, and those selected from alkali metal hydroxides, carbonates, phosphates, and borate salts may be used. Specific examples are Na and K, oxalate, carbonate, phosphate and borate And the like can be used. When the basicity is out of the range of the basicity, that is, the basicity of 0 to 7 does not effectively suppress the influence of the flame retardant component or its pyrolysate, a large amount of by-products are generated during the pyrolysis reaction.

The catalyst having a Brenstead basicity of 8 to 14 helps to produce carboanions and increases the yield of styrene contained in the oil. Particularly, the catalyst having a strong basicity, in pepolystyrene containing a flame retardant, which is difficult to decompose by conventional methods among waste polystyrene, reacts with the bromine component contained in the flame retardant to deactivate the flame retardant to increase the pyrolysis yield and increase the basicity during the pyrolysis reaction. Adjust and disassemble effectively.

The present invention using the strong catalyst of the Brentstead base is made of the following process using the apparatus shown in FIG.

In order to easily discharge the styrene-containing oil produced by the pyrolysis process, a flame retardant and a nonflammable flame retardant having an irregular size of about 3 to 5 cm are contained in a flow of nitrogen gas of 30 to 40 ml / min. 1 L capacity continuous flow tank stirring (CSTR) pyrolysis reactor (2) equipped with a cooler capable of cooling and condensing the product of the used waste polystyrene and Brenstead basic catalyst in the heating furnace (1) shown in FIG. After heating to the reaction temperature of 200 ~ 1000 ℃ with a temperature measuring device (4) and stirred with a stirrer (5) at a rotational speed of 150 to 300 rpm and reacted for 1 to 2 hours. After the reaction, the cracked gas is liquefied into a condenser 5 to be obtained as an oil and collected 6 in a recovery tank. The collected oil may determine the content of styrene monomer by analyzing the oil component using gas chromatography.

The collected oil includes benzene, toluene, ethylbenzene, and alphamethyl styrene as by-products together with the styrene monomer, and the styrene monomer is used as a raw material industrially, so that the higher the yield, the more economical and excellent in terms of resource recycling. Has an effect.

Hereinafter, the present invention will be described in more detail with reference to the following examples, which are not intended to limit the present invention.

Waste polystyrene used in the present invention is a crushed product of building insulation containing a large amount of flame retardant (Examples 1 to 8 and Comparative Examples 1 and 2) and a reduced ingot (Ingot) collected in the center of the Garak-dong agricultural and fish market containing a small amount of flame retardant Example 10 and Comparative Examples 3-4) were used.

Example 1

      1 with a cooler in the heating furnace 1 shown in FIG. 1, 200 g of irregularly sized crushed particles within 3 cm of waste polystyrene containing flame retardant and 1.0% of catalyst NaOH in a state of flowing 30 ml / min of nitrogen gas. It was placed in a continuous flow tank stirring (L) capacity (CSTR) pyrolysis reactor (2) and confirmed by heating to a reaction temperature of 370 ℃ with a temperature measuring device (4) and then reacted by stirring at a rotation speed of 200 rpm with a stirrer (5). After the reaction, the cracked gas was liquefied with a condenser (5) and collected (6) in an oil recovery tank. The collected oil was measured for thermal decomposition by volumetric measurement over time using a measuring cylinder, and the analysis of the oil was carried out by a capillary column (HP-5, 30 m × 0.32 mm × 1.0 μm, Crosslinked 5% PH ME Siloxane). ) Was equipped with GC / FID (DONAM Instrument). Yield and component analysis of the collected oil are shown in Table 1 below.

Example 2

Prepared in the same manner as in Example 1, but was carried out in place of 1.0% KOH with the catalyst. Yield and composition analysis of the collected oils are shown in Table 1 below.

Example 3

Prepared in the same manner as in Example 1, but was carried out in place of 1.0% NaHCO _{3 with} the catalyst. Yield and component analysis of the collected oil are shown in Table 1 below.

Example 4

Prepared in the same manner as in Example 1, but was performed in place of 1.0% Na ₂ CO ₃ with the catalyst. Yield and component analysis of the collected oil are shown in Table 1 below.

Example 5

Prepared in the same manner as in Example 1, but was performed in place of 1.0% Na ₂ HPO ₄ with the catalyst. Yield and component analysis of the collected oil are shown in Table 1 below.

Example 6

Prepared in the same manner as in Example 1, but was carried out by replacing the Na ₃ PO ₄ 1.0% with the catalyst. Yield and component analysis of the collected oil are shown in Table 1 below.

Example 7

Prepared in the same manner as in Example 1, but was performed in place of 1.0% Na ₂ HBO ₃ with the catalyst. Yield and component analysis of the collected oil are shown in Table 1 below.

Example 8

Prepared in the same manner as in Example 1, but was performed in place of 1.0% Na ₃ BO ₃ with the catalyst. Yield and component analysis of the collected oil are shown in Table 1 below.
Example 10

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Prepared in the same manner as in Example 1, except that 200 g of waste polyethylene containing no flame retardant, and replaced with 1.0% NaOH with the catalyst. Yield and component analysis of the collected oil are shown in Table 1 below.

Comparative Example 1

Prepared in the same manner as in Example 1, but performed without the catalyst. Yield and component analysis of the collected oil are shown in Table 1 below.

Comparative Example 2

Prepared in the same manner as in Example 1, but was carried out in place of BaO 1.0% with the catalyst. Yield and component analysis of the collected oil are shown in Table 1 below.

Comparative Example 3

Prepared in the same manner as in Example 1, but was carried out in place of 200 g of waste polyethylene, a catalyst containing no flame retardant. Yield and component analysis of the collected oil are shown in Table 1 below.

Comparative Example 4

Prepared in the same manner as in Example 1, except that 200 g of waste polyethylene containing no flame retardant and 1.0% of BaO was used as a catalyst. Yield and component analysis of the collected oil are shown in Table 1 below.

상기 표 1에서 알 수 있듯이, 난연성 폐폴리스틸렌에 촉매를 사용하지 않은 비교예 1는 브렌스테드 염기도가 강한 NaOH, KOH, NaHCO₃ 등의 염기성 촉매를 사용한 실시예 1 ∼ 9에 비하여 오일 수율이 10 %이상 낮으며, 상기 오일의 성분중 스틸렌 단량체의 함량은 2배 이상 차이를 보였다. 또한, 실시예 1과 같은 조건에 금속 산화물을 촉매로 사용한 비교예 2는 수집된 오일의 수율은 비슷하나 스틸렌 단량체의 함량이 다소 떨어짐을 보였다.

As can be seen from Table 1, Comparative Example 1, which does not use a catalyst in flame retardant waste polystyrene, has an oil yield of 10 compared to Examples 1 to 9 using a basic catalyst such as NaOH, KOH, NaHCO ₃ , which has a strong Brenstead basicity. Lower than%, the content of the styrene monomer in the oil component showed a difference of more than two times. In addition, Comparative Example 2 using a metal oxide as a catalyst under the same conditions as in Example 1 showed that the yield of the collected oil was similar, but the content of the styrene monomer was somewhat decreased.

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On the other hand, Example 10 using NaOH in nonflammable waste polystyrene showed good results almost similar to Comparative Example 4 using BaO showing the best results in nonflammable waste polystyrene, and oil yield compared to Comparative Example 3 using no catalyst. And the styrene monomer selectivity increased by 2.81% and 7.74%, respectively.

In the present invention, when recovering styrene monomer from waste polystyrene by pyrolysis reaction, it is better than the case of non-catalyst using Brenstead basic catalyst, and has similar yield and selectivity as compared with conventional best catalyst (BaO). In the waste polystyrene containing the flame retardant, the oil yield and the selectivity of styrene monomer were increased. Therefore, it improves the economics in terms of recovering and recycling the raw materials as described above, and shows an excellent effect in terms of the environment because the waste is recycled.

Claims (3)

In the method for recovering the styrene monomer by pyrolyzing waste polystyrene containing a flame retardant,  The catalyst for simultaneously decomposing the waste polystyrene and the flame retardant is selected from oxalate, carbonate, phosphate, and borate salts of Na and K having 8 to 14 brensted base in an aqueous solution.  The pyrolysis reaction is a method for recovering the styrene monomer from the waste polystyrene containing a flame retardant, characterized in that carried out for 1 to 2 hours at a temperature of 200 ~ 1000 ℃. delete The method of claim 1, wherein the catalyst is selected from NaOH, KOH, NaHCO _3, Na ₂ CO ₃ , Na ₃ PO ₄ , Na ₂ HPO ₄ , Na ₃ BO ₃ , and Na ₂ HBO ₃ . A method for recovering styrene monomer from waste polystyrene containing a flame retardant.

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