KR102704507B1 - Catalyst and method for pyrolyzing residual oil of pyrolyzed waste polystyrene - Google Patents

Abstract

The present invention relates to a catalyst and a pyrolysis method for pyrolyzing residual oil from waste polystyrene pyrolysis, wherein the catalyst is an ultra-stable Y zeolite (US Y zeolite), or a zeolite having an MWW structure is included together with 2-propanol to pyrolyze residual oil from waste polystyrene pyrolysis, thereby increasing the selectivity of cumene among the pyrolysis products of the residual oil.

Description

Catalyst and method for pyrolyzing residual oil of pyrolyzed waste polystyrene

The present invention relates to a catalyst and a method for pyrolyzing residual oil obtained by pyrolyzing waste polystyrene, and more particularly, to a catalyst that improves selectivity to cumene and a pyrolysis method using the catalyst.

Polystyrene is a plastic commonly encountered in everyday life, used in food containers such as dairy product and disposable cup lids, agricultural and marine product packaging trays, and styrofoam for home appliance packaging. As the population and industrial activities increase, its proportion in modern industrial society is increasing, and the massive amount of waste polystyrene generated as a result is causing serious social and environmental problems, so research is being conducted to recycle it.

As a method of recycling waste polystyrene, thermal decomposition under appropriate pressure, temperature, and inert atmosphere is receiving more attention than simple physical addition or processing. In the case of thermal decomposition, the polymer structure is decomposed to obtain a liquid or gaseous mixture of hydrocarbons with a small number of carbon atoms, which is then reused as an industrial compound with added value. By obtaining styrene monomer and a usable compound with added value through thermal decomposition, waste polystyrene has advantages in environmental and economic aspects.

Technologies related to such polystyrene pyrolysis are being actively studied, and technologies for recovering styrene monomer from waste polystyrene or obtaining useful compounds such as oil from waste polystyrene have been reported, as in Korean Patent Registration No. 10-0468047.

However, during the process of pyrolyzing polystyrene into monomers, a significant amount of residual oil is generated that is not completely pyrolyzed. Depending on the method of handling this residual oil, the economic feasibility and environmental impact of polystyrene pyrolysis can vary greatly. Therefore, much research is being conducted on handling this residual oil. Among these, there is an attempt to further increase the amount of oil or styrene monomer recovered by pyrolyzing the residual oil again.

As part of the above research, non-patent document 1 discloses a method for thermally decomposing residual oil generated from thermal decomposition of waste polystyrene using a ZSM-5 zeolite catalyst. However, in the case of the above prior document, it only discloses that styrene monomer, toluene, benzene, and ethylbenzene can be obtained by thermal decomposition of residual oil, and does not disclose at all a method for selectively obtaining cumene, which has a relatively high utilization rate among the thermal decomposition products of the residual oil.

Non-patent Document 2 relates to the selective production of ethylbenzene and benzene by pyrolysis of polystyrene, using USY (ultra-stable Y) zeolite as a catalyst. According to the document, the selectivity of the yield of ethylbenzene and benzene varies depending on the molar ratio of SiO ₂ /Al ₂ O ₃ , and when the molar ratio of SiO ₂ /Al ₂ O ₃ of USY zeolite is 5.3, it exhibits the highest selectivity for ethylbenzene and benzene due to the high surface area, large pores, and abundant strong acid sites. However, there is no mention of pyrolysis of polystyrene pyrolysis residue.

Japanese Patent No. 6956187 (October 6, 2021) relates to the conversion of waste plastics into propylene and cumene. It discloses stepwise pyrolysis of waste plastics to produce benzene and propene from residual oil, and synthesis of these to produce cumene, using MCM-22 as an alkylation catalyst.

However, in the case of the above prior literature, cumene is manufactured by obtaining benzene and propylene from waste plastics, respectively, and then synthesizing them, so the process of manufacturing cumene from residual oil is somewhat complicated.

Korean Patent Registration No. 10-0468047 (January 14, 2005) Japanese Patent No. 6956187 (2021.10.06.)

Korean J. Chem. Eng., 20(1), (2003)0 133-137 J. Wang, et al. Energy Conversion and Management 200 (2019) 112088

Accordingly, the inventors of the present invention go beyond the conventional pyrolysis technology of waste polystyrene to provide a method for reducing environmental pollution and improving economic efficiency by pyrolyzing residual oil generated during the pyrolysis, and for selectively producing cumene among the products generated through the pyrolysis of residual oil.

The present invention provides a catalyst for pyrolysis of waste polystyrene pyrolysis residue, which comprises ultra-stable Y zeolite (USY) and is characterized by a higher selectivity for cumene than other pyrolysis products, in order to solve the above problems.

In one embodiment of the present invention, the SiO ₂ /Al ₂ O ₃ molar ratio of the ultra-stable Y-zeolite may be in a range of more than 5 and less than or equal to 10.

As another embodiment of the present invention, the present invention provides a catalyst for pyrolysis reaction of waste polystyrene pyrolysis residue oil, characterized in that it includes a zeolite having an MWW structure as a catalyst for selectively forming cumene by pyrolysis of waste polystyrene pyrolysis residue oil in the presence of 2-propanol.

In addition, the present invention provides a method for pyrolysis of waste polystyrene pyrolysis residue, characterized in that the selectivity for cumene is higher than that for other pyrolysis products by using a catalyst including an ultra-stable Y-zeolite.

At this time, the ultra-stable Y-zeolite catalyst may be included in an amount of 1 to 50 parts by weight per 100 parts by weight of the residual oil, and the thermal decomposition temperature of the residual oil may be 275 to 350°C.

The present invention provides a method for pyrolysis of waste polystyrene pyrolysis residue, which is another method for pyrolysis of waste polystyrene pyrolysis residue, in which the pyrolysis is performed by contacting the zeolite having an MWW structure in the presence of 2-propanol, thereby increasing the selectivity for cumene among pyrolysis products.

In the above method, the thermal decomposition temperature of the waste polystyrene pyrolysis residue oil may be 275 to 350°C, the zeolite having the MWW structure may be 1 to 50 parts by weight with respect to 100 parts by weight of the residue oil, and 2-propanol may be 1 to 10 parts by weight with respect to 100 parts by weight of the residue oil.

According to the present invention, waste polystyrene pyrolysis residue can be pyrolyzed into useful components, which is advantageous in terms of environmental pollution and economic aspects.

In addition, there is an advantage of being able to increase the selectivity of cumene among the pyrolysis products from the above residual oil.

Figure 1 is a graph showing the components of residual oil resulting from thermal decomposition of waste polystyrene according to one embodiment of the present invention, analyzed by gas chromatography.
FIG. 2 is a graph showing the product distribution according to the SiO ₂ /Al ₂ O ₃ molar ratio of USY zeolite according to one embodiment of the present invention.
FIG. 3 is a graph showing the product distribution according to the SiO ₂ /Al ₂ O ₃ molar ratio of a ZSM-5 catalyst according to one embodiment of the present invention.
FIG. 4 is a product distribution graph when residual oil is thermally decomposed including a catalyst and 2-propanol according to one embodiment of the present invention.
FIG. 5 is a product distribution graph when residual oil is thermally decomposed using only a catalyst without 2-propanol according to one embodiment of the present invention.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In general, the nomenclature used herein is well known and commonly used in the art.

Whenever it is said throughout this specification that a part "includes" a component, this does not exclude other components, but rather includes other components, unless otherwise stated.

Hereinafter, the present invention will be described in detail.

The present invention goes further than the conventional technology of pyrolyzing waste polystyrene to recover styrene monomer, and provides a pyrolysis catalyst for waste polystyrene pyrolysis residue oil and a pyrolysis method for waste polystyrene pyrolysis residue oil, which can reduce environmental pollution by re-pyrolyzing a large amount of residual oil generated during the pyrolysis of waste polystyrene without incinerating or discarding it, and can also increase the selectivity of cumene among the products resulting from the pyrolysis of the residual oil.

The above-mentioned pyrolysis residue of waste polystyrene refers to a substance that is not completely pyrolyzed during the process of depolymerizing waste polystyrene into styrene monomer, etc., or pyrolyzed into industrially useful compounds such as benzene, styrene, and cumene, or that is not gasified during the pyrolysis process even after being decomposed because its molecular weight is still considerably high.

In one embodiment of the present invention, ultra-stable Y-zeolite (USY) is used as the thermal decomposition catalyst.

The above USY is a type of Y-type zeolite, and is a Y-type zeolite having a SiO ₂ /Al ₂ O ₃ molar ratio of > 5, in which aluminum is removed from the Y-type zeolite framework by heat treatment at high temperature in the presence of steam or dealumination of aluminum-rich Y-type zeolite. USY exhibits higher thermal and hydrothermal stability and higher catalytic activity than conventional aluminum-rich Y zeolite.

The present invention relates to a catalyst for thermally decomposing residual oil by thermal decomposition of waste polystyrene, wherein the selectivity for cumene can be increased by using USY. Preferably, the molar ratio of SiO ₂ /Al ₂ O ₃ of the USY can be in a range of more than 5 and less than 10. When the molar ratio of SiO ₂ /Al ₂ O ₃ of the USY is in the above range, the conversion rate of the residual oil and the selectivity for cumene are maintained high.

In addition, the present invention provides a pyrolysis method for pyrolyzing waste polystyrene pyrolysis residue to obtain a pyrolysis product containing cumene.

The above thermal decomposition method is performed using ultra-stable Y-zeolite, and the content of the catalyst can be in the range of 1 to 50 parts by weight, preferably in the range of 3 to 10, per 100 parts by weight of waste polystyrene thermal decomposition residue oil.

If the content of the catalyst is 1 part by weight or less, the thermal decomposition of the residual oil may be minimal, and if it is 50 parts by weight or more, the increase in the thermal decomposition rate is not significant even with the added catalyst, making it inefficient.

The thermal decomposition of the above waste polystyrene thermal decomposition residue can be performed in the range of 275 to 350°C. If the temperature is lower than 275°C, thermal decomposition may not occur, and if it exceeds 350°C, the yield of cumene may decrease due to excessive thermal decomposition.

The pressure during the above thermal decomposition can be 1 to 10 atm. If the pressure is less than 1 atm, thermal decomposition may not occur, and if it exceeds 10 atm, the increase in thermal decomposition rate is not significant, making it inefficient.

In the present invention, the step of thermally decomposing waste polystyrene can be performed by a general thermal decomposition method for waste polystyrene, and the method is not limited thereto. In consideration of the content of waste polystyrene, the phase form (liquid, solid, gaseous) of the product by thermal decomposition, etc., the thermal decomposition temperature, thermal decomposition time, heating rate, moisture content, etc. can be varied.

For example, waste polystyrene can be crushed into a certain size, a crusher can be used to remove metal foreign substances from the crushed polystyrene, the polystyrene from which the foreign substances have been removed can be melted, and then placed in a pyrolysis reactor to heat it to a pyrolysis temperature to perform pyrolysis.

In addition, the present invention provides a method for pyrolysis of waste polystyrene pyrolysis residue, wherein the method comprises pyrolysis of waste polystyrene pyrolysis residue in the presence of 2-propanol.

By performing thermal decomposition of the residual oil under conditions containing 2-propanol, the selectivity of cumene among thermal decomposition products increases.

When thermally cracking waste polystyrene pyrolysis residue in the presence of 2-propanol, a zeolite with an MWW structure is used as a catalyst. The MWW structure is one of the zeolite framework topologies existing in a lamellar form, and the MWW framework structure is multilayered including two independent pore systems, one of which is a pore system of two-dimensional sinusoidal 10-membered ring (10-MR) channels with an elliptical ring cross-section of 4.1 Å × 5.1 Å and the other is a pore system including a large 12-MR giant cage connected to the 10-MR windows.

The zeolite of the MWW structure is a crystalline molecular sieve having an X-ray diffraction pattern including d-spacing maxima of 12.4±0.25, 6.9±0.15, 3.57±0.07 and 3.42±0.07 Å. The zeolite of the MWW structure according to the present invention may be, but is not limited to, MCM-22, PSH-3, SSZ-25, ERB-1, ITQ-1, ITQ-2, MCM-36, MCM-49, MCM-56, UZM-8 and mixtures thereof, and preferably may be MCM-22.

In the present invention, the selectivity of cumene among the thermal decomposition products of the residual oil increases by using the zeolite having the MWW structure.

At this time, the zeolite of the MWW structure is included in an amount of 1 to 50 parts by weight, preferably 3 to 10 parts by weight, per 100 parts by weight of waste polystyrene pyrolysis residue. If it is less than 1 part by weight, the pyrolysis reaction does not occur efficiently, so that the amount of benzene produced decreases, and thus the production of cumene may be reduced, which may cause a problem. If it exceeds 50 parts by weight, there is a concern that the production of cumene may be reduced due to the decomposition of 2-propanol.

The SiO ₂ /Al ₂ O ₃ molar ratio of the zeolite of the above MWW structure does not significantly affect the composition, but is generally preferably in the range of 10 to 50.

In addition, the 2-propanol may be 1 to 10 parts by weight, preferably 2.5 to 5 parts by weight, per 100 parts by weight of the residual oil. When the 2-propanol is less than 1 part by weight, the production of cumene is reduced due to a lack of 2-propanol, and when it exceeds 10 parts by weight, the production amount of cumene is not large even with the added 2-propanol, making it inefficient.

The thermal decomposition temperature of the waste polystyrene thermal decomposition residue containing the above 2-propanol may be 275 to 350°C, preferably 300 to 325°C. When the thermal decomposition temperature is in the range of 275 to 350°C, the production of cumene is high.

Hereinafter, examples will be described in more detail to explain the present invention. However, the following examples are only preferred embodiments of the present invention, and the present invention is not limited to the following examples.

<Example>

Waste polystyrene pyrolysis residue

Waste Styrofoam discharged from households is reduced and crushed, thermally decomposed at 400℃ for 1 hour, and compounds with boiling points below 180℃, such as benzene, toluene, and styrene, are separately captured, and the remaining waste polystyrene thermal decomposition residue is obtained.

The components of the residue oil manufactured above were analyzed by gas chromatography and are shown in Fig. 1 and Table 1.

No. R.T
(min) Compound % area 1 9.710 Benzene, 1,1'-(1,3-propanediyl)bis- 14.983 2 9.996 Benzene, 1,1'-(1-methyl-1,3-propanediyl)bis- 1.862 3 10.310 2,4-Diphenyl-1-butane 11.148 4 12.300 Naphthalene, 2-phenyl- 1.995 5 13.309 Naphthalene, 2-(phenylmethyl)- 2.731 6 13.665 m-Terphenyl 3.479 7 15.710 1,3,4-Oxadiazole, 4,5-dihydro-2,4,5-triphenyl- 4.811 8 15.755 Cyclohexane, 1,3,5-triphenyl- 4.853 9 17.212 1,1':2',1''-Terphenyl, 4'-phenyl- 7.605 10 17.369 Tetracyclo[16.3.1.1(4,8).1(11,15)]tetracosa-1(22),4,6,8(24),11,13,15(23),18,20-nonaene 4.128 11 18.604 1,1':3',1''-Terphenyl, 5'-phenyl- 33.305

Pyrolysis of waste polystyrene pyrolysis residue

(Experimental Example 1) SiO of ultra-stable Y-zeolite in the absence of 2-propanol ₂ /Al ₂ O ₃ Thermal decomposition of residual oil according to molar ratio

The above-mentioned manufactured residual oil was injected into a reactor and thermally decomposed at 300°C, 1 atm (N ₂ ) using 5 wt% of an ultra-stable Y-zeolite catalyst under the conditions of 500 rpm for 1 hour. However, the SiO ₂ /Al ₂ O ₃ molar ratio of the ultra-stable Y-zeolite catalyst was varied to 5.1, 5.2, 30, and 80.

(Experimental Example 2) Thermal decomposition of residual oil by ZSM5 zeolite in the absence of 2-propanol

The residual oil was thermally decomposed in the same manner as in Experimental Example 1, except that ZSM5 (CBV-3024E) was used as a zeolite catalyst and the SiO ₂ /Al ₂ O ₃ molar ratio was set to 23, 30, 50, and 280.

Figure 2 shows the product yield distribution of the residue according to the SiO ₂ /Al ₂ O ₃ molar ratio of the ultra-stable Y-zeolite in the residue pyrolysis using the ultra-stable Y-zeolite catalyst. In the figure, a-MS stands for alpha methylstyrene. As shown in Figure 2, the product distribution of the residue changes according to the SiO ₂ /Al ₂ O ₃ ratio of the ultra-stable Y-zeolite catalyst, and when the SiO ₂ /Al ₂ O ₃ ratio is 5.1 and 5.2 wt%, cumene is produced at a remarkably high rate of 40 wt% in yield.

Figure 3 shows the product yield distribution of residual oil according to the SiO ₂ /Al ₂ O ₃ molar ratio of ZSM5 in residual oil thermal decomposition using ZSM5 zeolite catalyst.

Through this, it can be seen that the ZSM5 catalyst generally shows high benzene selectivity. However, when the ultra-stable Y-zeolite is used as a catalyst according to the present invention, the selectivity for cumene is shown to be high.

(Experimental Example 3) Thermal decomposition of residual oil using MWW type zeolite in the presence of 2-propanol

To 20 g of the above residual oil, 0.1 g of MCM-22 (SiO ₂ /Al ₂ O ₃ = 17) as an MWW type zeolite was added, and 5 g of 2-propanol was added as one of the reactants, followed by thermal decomposition under 0.1 MPa conditions, and the product was analyzed by gas chromatography. The results of the analysis are shown in Fig. 4.

(Experimental Example 4) Thermal decomposition of residual oil using MFI type zeolite in the presence of 2-propanol

The residual oil was thermally decomposed by the same method as in Experimental Example 3, except that ZSM-5 (SiO ₂ /Al ₂ O ₃ = 30) was used as a catalyst, and the results are shown in Fig. 4.

(Experimental Example 5) Thermal decomposition of residual oil using MFI type zeolite in the absence of 2-propanol

Except that 2-propanol was not used in Experimental Example 4 above, residual oil was thermally decomposed in the same manner, and the results are shown in Fig. 5.

(Experimental Example 6) Thermal decomposition of residual oil using MWW type zeolite in the absence of 2-propanol

Except that MCM-22 was used instead of ZSM-5 as a catalyst in Experimental Example 5 above, residual oil was thermally decomposed in the same manner, and the results are shown in Fig. 5.

Comparing Figures 4 and 5, it can be seen that the selectivity of cumene increases when the pyrolysis residue of waste polystyrene is pyrolyzed in the presence of 2-propanol.

However, even in the presence of 2-propanol, the selectivity for cumene was significantly higher in the case of using MWW-type zeolite (Experimental Example 3) than in the case of using MFI-type zeolite, confirming that cumene can be selectively produced.

The above-described embodiments have been described for preferred embodiments of the present invention, but are not limited thereto and may be implemented in various forms without departing from the technical spirit of the present invention.

Claims (10)

In a catalyst for thermally decomposing waste polystyrene thermal decomposition products, products having a boiling point of 180℃ or lower are removed and the remaining waste polystyrene thermal decomposition residue is thermally decomposed.
A catalyst for pyrolysis of waste polystyrene pyrolysis residue, characterized in that the catalyst comprises ultra-stable Y zeolite (USY) and has a higher selectivity for cumene than other pyrolysis products.
In the first paragraph,
A catalyst for thermal decomposition of waste polystyrene thermal decomposition residue, characterized in that the SiO ₂ /Al ₂ O ₃ molar ratio of the above ultra-stable Y-zeolite is in the range of more than 5 and less than 10.
A catalyst for selectively forming cumene by thermally decomposing waste polystyrene pyrolysis residue oil remaining after removing waste polystyrene pyrolysis products having a boiling point of 180℃ or lower in the presence of 2-propanol.
A catalyst for thermal decomposition reaction of waste polystyrene thermal decomposition residue, characterized in that the catalyst comprises a zeolite having an MWW structure.
In a method for removing waste polystyrene pyrolysis products having a boiling point of 180℃ or lower and pyrolyzing the remaining waste polystyrene pyrolysis residue,
A method for pyrolysis of waste polystyrene pyrolysis residue, characterized in that the selectivity for cumene is higher than that for other pyrolysis products by using a catalyst comprising an ultra-stable Y-zeolite.
In paragraph 4,
A method for thermal decomposition of waste polystyrene pyrolysis residual oil, characterized in that the above ultra-stable Y-zeolite catalyst is contained in an amount of 1 to 50 parts by weight per 100 parts by weight of residual oil.
In paragraph 4,
A method for thermal decomposition of waste polystyrene thermal decomposition residual oil, characterized in that the thermal decomposition temperature of the residual oil is 275 to 350°C.
In a method for removing waste polystyrene pyrolysis products having a boiling point of 180℃ or lower and pyrolyzing the remaining waste polystyrene pyrolysis residue,
A method for thermal decomposition of waste polystyrene thermal decomposition residue, characterized by thermal decomposition by contact with a zeolite having an MWW structure in the presence of 2-propanol.
In Article 7,
A method for pyrolysis of waste polystyrene pyrolysis residue, characterized in that the pyrolysis temperature of the waste polystyrene pyrolysis residue is 275 to 350°C.
In Article 7,
A method for thermal decomposition of waste polystyrene pyrolysis residual oil, characterized in that the zeolite having the above MWW structure is present in an amount of 1 to 50 parts by weight per 100 parts by weight of residual oil.
In Article 7,
A method for thermal decomposition of waste polystyrene thermal decomposition residual oil, characterized in that the above 2-propanol is 1 to 10 parts by weight per 100 parts by weight of residual oil.