KR20230080202A - Catalyst for depolymerization of polystyrene and depolymerization process of polystyrene using the same - Google Patents

Abstract

The present invention relates to a catalyst for polystyrene depolymerization. The catalyst for polystyrene depolymerization of the present invention is environmentally friendly, economical, and can be easily prepared. The catalyst for polystyrene depolymerization of the present invention is excellent in energy saving efficiency when applied to the polystyrene depolymerization reaction. When the catalyst for polystyrene depolymerization of the present invention is applied to the polystyrene depolymerization reaction, the yield and selectivity of styrene monomer are high.
In addition, the present invention relates to a method for depolymerizing polystyrene. The polystyrene depolymerization method of the present invention is excellent in energy saving efficiency and has high yield and selectivity of styrene monomer.

Description

Catalyst for depolymerization of polystyrene and depolymerization process of polystyrene using the same}

The present invention relates to a catalyst for polystyrene depolymerization.

Further, the present invention relates to a method for depolymerizing polystyrene using the catalyst.

Along with industrial development, plastic usage is increasing worldwide. Most plastics are discarded after use, which causes many environmental problems. Waste plastic (plastic that is discarded after use) is mainly disposed of in landfills. However, waste plastics take a long time to biodegrade in the soil, and landfills are scarce. Therefore, a method of treating waste plastic through a process of decomposing (pyrolysing) waste plastic by applying predetermined heat rather than a landfill method is advantageous from an environmental or economical point of view.

The direction of development of waste plastic pyrolysis treatment technology is to solve the two tasks of low-emission waste treatment and recovery of raw materials with one technology. On the other hand, waste polystyrene or styrene foam (hereinafter, referred to as "polystyrene") can be easily obtained by pyrolyzing styrene monomer (monomer) with high added value. At this time, components other than the styrene monomer (eg, gasoline, etc.) are recovered as other effective chemicals and can be used in other processes. Therefore, since polystyrene is more advantageous in terms of economic efficiency than other types of plastic waste, research on its thermal decomposition is attracting attention.

There are largely two methods for preparing styrene monomer by chemically decomposing polystyrene, that is, depolymerizing polystyrene. First, it is a thermal pyrolysis method, which is a method of simply applying only thermal energy (without a catalyst). Second, it is a catalytic pyrolysis method in which a catalyst is added during the heating process.

The former has a high thermal decomposition temperature, and it is difficult to obtain a high-quality product because the molecular weight and shape of the product show various distributions. In addition, there is a risk that the process may be stopped due to carbon deposition in the reactor by the former product.

The latter uses highly acidic or basic catalysts. When a strong acidic catalyst is used, ethyl benzene and α-methyl styrene are produced due to continuous cracking and hydrogenation reactions following beta cleavage of carbon-carbon bonds. A large amount of by-products are produced.

The strong basic catalyst is used in a supported state on a support such as silica, alumina or a porous material (see Patent Document 1). These catalysts are expensive to manufacture, difficult to manufacture, and a large amount of wastewater that causes environmental pollution is generated in the process.

As a catalyst used in the thermal decomposition process of polystyrene, metal oxide catalysts such as MgO and BaO are known in the prior art (see Non-Patent Document 1). However, since such a metal oxide catalyst has a low specific surface area, the activity required for thermal decomposition of polystyrene is low.

A composite oxide catalyst containing magnesium (Mg) and aluminum (Al) as main components has also been considered because of its strong alkalinity. However, there is no example of applying it as a catalyst for thermal decomposition of polystyrene. On the other hand, the above complex oxide catalyst can be obtained by calcining a hydrotalcite (layered double hydroxide of a material represented by the general formula Mg ₆ Al ₂ Co ₃ (OH) ₁₆ 4H ₂ O) material. there is. Various methods are known as a method of obtaining such a hydrotalcite material. Among them, the co-precipitation method is the most widely known. In the co-precipitation method, co-precipitation conditions such as co-precipitation rate and pH are not established, the required time is long, and a large amount of wastewater that causes environmental pollution is produced. It is unsuitable for mass production of catalysts.

Therefore, it is environmentally friendly, can be easily manufactured economically, and at the same time has excellent energy saving efficiency when applied to the manufacturing process of styrene monomer, specifically the pyrolysis process of polystyrene, more specifically the process of depolymerization of polystyrene. It is necessary to study complex oxide catalysts with high yield and selectivity.

Korean Patent Publication No. 10-2003-0081717

Industrial & Engineering Chemistry Research, pp. 13411-13422

An object of the present invention is to provide a catalyst for polystyrene depolymerization that is environmentally friendly, economical, and easily prepared.

The present invention is intended to provide a catalyst with excellent energy saving efficiency when applied to the depolymerization reaction of polystyrene.

An object of the present invention is to provide a catalyst with high yield and selectivity of styrene monomer when applied to polystyrene depolymerization.

The object of the present invention is not limited to the above object.

The catalyst for polystyrene depolymerization of the present invention is prepared by a solid phase reaction and includes a complex oxide having an alkaline earth metal and a group 13 element, and the molar ratio (A) of the alkaline earth metal (A) and the group 13 element (B) in the complex oxide /B) is within the range of 0.05 to 20.

The polystyrene depolymerization method of the present invention includes the step of thermally decomposing polystyrene by applying heat to a raw material including the catalyst and polystyrene.

The catalyst for polystyrene depolymerization of the present invention is environmentally friendly, economical, and can be easily prepared.

The catalyst for polystyrene depolymerization of the present invention is excellent in energy saving efficiency when applied to the polystyrene depolymerization reaction.

When the catalyst for polystyrene depolymerization of the present invention is applied to the polystyrene depolymerization reaction, the yield and selectivity of styrene monomer are high.

The polystyrene depolymerization method of the present invention is excellent in energy saving efficiency and has high yield and selectivity of styrene monomer.

Figure 1 schematically shows the process of proceeding with the method of the present invention.

The present invention relates to catalysts. Specifically, the present invention relates to a catalyst suitable for the decomposition reaction of waste plastics.

The raw material of the decomposition reaction to which the catalyst of the present invention is applied is polystyrene. In addition, the present invention is intended to provide a catalyst whose effect is maximized when applied to a reaction for obtaining a styrene monomer by decomposition, that is, depolymerization of polystyrene.

There are various reactions to obtain styrene monomer from polystyrene. In particular, the complex oxide catalyst of the present invention is suitable for a reaction in which a styrene monomer is obtained by depolymerizing polystyrene through thermal decomposition of the polystyrene.

A depolymerization reaction, as is known, refers to a process in which a compound having a single structure is obtained by decomposing a chain constituting a polymer as a reverse reaction of the polymerization reaction.

The catalyst of the present invention includes complex oxides. The complex oxide may refer to an oxide of a metal and/or metalloid having a plurality of different metal and/or metalloid components. For example, an oxide of one metal component, such as MgO or Al ₂ O ₃ , does not correspond to the composite oxide of the present invention. In particular, no prior art is known in which the composite oxide of the present invention is applied to a polystyrene depolymerization reaction and/or a polystyrene thermal decomposition process.

In the depolymerization reaction of polystyrene, the catalyst of the present invention can reduce the decomposition temperature compared to the conventional catalyst. Therefore, the catalyst of the present invention can save energy required for the reaction. In addition, the catalyst of the present invention shows basicity. Accordingly, selectivity and/or yield of styrene monomer in the reaction may be increased.

In the present invention, the terms "selectivity" and "yield" are applied with known meanings. That is, in the present invention, selectivity refers to a measure of how much a desired product is produced compared to a non-target product. In the present invention, yield refers to a measure of how much a desired product is produced compared to how much a reactant is consumed. Unless otherwise specified, the selectivity refers to overall selectivity, and the yield refers to overall yield.

The catalyst of the present invention includes a complex oxide, and the complex oxide catalyst has excellent thermal stability in the depolymerization reaction of polystyrene because of its composition described later. In addition, the composite oxide catalyst can be easily separated from the reactants and products of the depolymerization reaction due to its composition, which will be described later, and cannot be easily deactivated, and thus has excellent reusability.

As described above, the catalyst of the present invention comprises a complex oxide, and the complex oxide contains (or has) at least two different metal and/or metalloid components. Specifically, the complex oxide contains at least an alkaline earth metal and a Group 13 element as its components. In addition, since the complex oxide is an oxide, it may further include oxygen in addition to the above components. The oxygen may be derived from precursors of each of the alkaline earth metal and Group 13 elements constituting the complex oxide.

Alkaline earth metals may refer to Group 2 elements on the periodic table. Examples of alkaline earth metals include beryllium, magnesium, calcium, stronnium, barium or lithium. In one embodiment, magnesium may be employed as the alkaline earth metal.

A group 13 element, literally, can refer to a group 13 element on the periodic table. For example, group 13 elements include boron, aluminum, gallium, indium, thallium, or nihonium. Among the above, boron is commonly known as a metalloid, and the other elements are known as metals. In one embodiment, aluminum may be used as the Group 13 element.

The complex oxide is prepared by a solid state reaction. A solid phase reaction may refer to a reaction in which reactant(s) react in a solid state to form a product. Specifically, the complex oxide may be prepared by mixing a solid precursor of an alkaline earth metal and a precursor of a group 13 element. For example, the precursors may each independently have a powder form.

That a specific component has a powder form means that it exists in a solid state at room temperature and has a predetermined particle size.

The term room temperature means a temperature in its natural state that is not particularly heated or cooled. For example, room temperature may be a temperature in the range of 20 °C to 30 °C, about 25 °C or about 23 °C.

In order to obtain a complex oxide by mixing the precursors, it is preferable to use a compound containing at least a corresponding element and oxygen as the precursor. In one embodiment, the alkaline earth metal precursor may be a nitrate hydrate of the alkaline earth metal. In addition, the group 13 element precursor may be a nitrate hydrate of the group 13 element.

In the process of mixing the precursors to cause a solid phase reaction, a predetermined salt may be included in the mixture of the precursors. These salts can create a state in which the precursors can more smoothly form the composite metal oxide when heat for sintering is applied to the mixture. Examples of such salts include carbonates of alkali metal ions such as sodium ions and potassium ions, or carbonates of non-metallic cations. On the other hand, considering the efficiency of the manufacturing process, carbonate salts of non-metallic cations, such as ammonium bicarbonate, can be easily removed during the sintering process of the mixture, which is more advantageous. This is because when carbonate of alkali metal ions is applied, it is not easily removed from the product even through heat treatment due to its high melting point, and an additional washing process may be required.

It is good if the content of the salt is also controlled. This is because the precursors can have a composition suitable for the present invention. For example, the ratio (D/C) of the number of moles (D) of the salt to the total number of moles (C) of each of the precursors may be in the range of 1 to 2.

As described above, conventional composite oxides or catalysts containing them are generally prepared by a co-precipitation method. The co-precipitation method is a method of depositing a plurality of reactants in a specific solvent (or solvent) to simultaneously precipitate them, and then precipitate these precipitates. However, this method has strict manufacturing conditions such as co-precipitation speed, takes a long reaction time, high initial investment cost, and high energy consumption. In the present invention, the coprecipitation method is not applied when obtaining a composite oxide. The composite oxide or composite oxide is prepared by a solid-state reaction. Through this, the composite oxide can be produced within a short time, and at least does not have a problem when produced by the coprecipitation method. The composite oxide prepared by the coprecipitation method has significantly lower crystallinity and specific surface area than the composite metal oxide of the present invention.

In addition, in the catalyst of the present invention, the pH (or pOH) of the catalyst is adjusted by appropriately adjusting the ratio of the components of the catalyst. Through this, the catalyst of the present invention improves the yield and/or selectivity of styrene monomer in the polystyrene depolymerization reaction.

The catalyst of the present invention has a high pH only within the composition range described below, and this characteristic of the catalyst improves the yield and/or selectivity of styrene monomer in the polystyrene depolymerization reaction.

Specifically, in the composite oxide, the ratio between the number of moles occupied by the alkaline earth metal and the number of moles occupied by the Group 13 element is controlled. If the number of moles occupied by the alkaline earth metal is A and the number of moles occupied by the group 13 element is B, the ratio of A to B (A/B) in the composite oxide of the present invention is in the range of 0.05 to 20. Within the range of the ratio, the lattice expansion of the alkaline earth metal in the complex oxide is maximized to increase the pH of the complex oxide. As the pH of the catalyst increases, that is, as the catalyst has a strong basicity, the yield and selectivity of the polystyrene depolymerization reaction increase remarkably. As a result, when the complex oxide is applied as a catalyst in the polystyrene depolymerization reaction, the yield and/or selectivity of the styrene monomer is improved.

In another embodiment, the lower limit of the ratio (A/B) may be 0.07 or 0.1. In another embodiment, the upper limit of the ratio (A/B) may be 17, 15, 13, 10, 5, 3 or 2.

The ratio may be determined according to the mixing ratio of the alkaline earth metal precursor and the group 13 element precursor applied in the manufacturing process of the composite oxide.

In the present invention, if a specific numerical value is within a specific range, for example within the range of a to b, this may mean that the numerical value is greater than or equal to a and less than or equal to b.

In the composite oxide, the molar ratio of oxygen is determined according to the number of moles of oxygen included in the precursor used to prepare the composite oxide or the mixing ratio between the precursors, and is not particularly limited.

As described above, in the composite oxide of the present invention, the alkaline earth metal may be magnesium, and the group 13 element may be aluminum. Thus, the metal oxide catalyst of the present invention may have a general formula of, for example, Mg _x Al _y O. In the above, x and y may each independently range from 1 to 20, 1 to 15, or 1 to 10. However, the relationship between the ratio (A/B) of the alkaline earth metal and Group 13 element in the composite oxide described above must be satisfied.

In another aspect, the present invention relates to a method for depolymerizing polystyrene. Hereinafter, the corresponding method may also be referred to as “the method of the present invention”. The method of the present invention utilizes the catalyst described above.

In the method of the present invention, heat is applied to a raw material having a specific composition to thermally decompose the raw material. That is, the method of the present invention includes a step of applying heat to a specific raw material. Since the method of the present invention is a polystyrene depolymerization method, the raw material includes at least polystyrene. In addition, since the method of the present invention uses the catalyst, the raw material further includes the catalyst. Since the raw material includes polystyrene, when heat is applied to the raw material, the polystyrene is thermally decomposed. That is, the depolymerization reaction of polystyrene proceeds through the thermal decomposition. As a result, a styrene monomer is obtained. That is, the method of the present invention includes at least the step of thermally decomposing polystyrene by applying heat to a raw material including the catalyst and polystyrene.

In one embodiment, the application amount of the catalyst may be appropriately adjusted. For example, the content of the catalyst may be within the range of 0.01 part by weight to 30 parts by weight based on 100 parts by weight of the polystyrene. When the catalyst is included within the above range, the polystyrene depolymerization reaction may properly proceed, and additional reactions may not occur, so that the styrene monomer may be obtained more smoothly.

In another embodiment, the lower limit of the content of the catalyst may be 0.05 parts by weight, 0.1 parts by weight, 0.5 parts by weight, 1.0 parts by weight, 1.5 parts by weight or 2.0 parts by weight. In another embodiment, the upper limit of the content of the catalyst may be 25 parts by weight, 20 parts by weight, 15 parts by weight, 10 parts by weight, 5.0 parts by weight, 3.0 parts by weight or 2.0 parts by weight.

In one embodiment, the treatment temperature of the thermal decomposition step may also be appropriately controlled. In one embodiment, the thermal decomposition of the polystyrene may be performed at a temperature in the range of 250 °C to 500 °C. Within the above range, polystyrene depolymerization can proceed smoothly, the amount of low molecular weight products (products and by-products having a lower molecular weight than styrene monomer) can be minimized, and styrene monomer can be obtained in the form of liquid oil, which is an easy-to-recover form. there is.

Figure 1 schematically shows the process of proceeding with the method of the present invention. That is, FIG. 1 shows a polystyrene depolymerization process and equipment required therefor. The apparatus is equipped with a regulator (1), a flow meter and a gas meter (2) for controlling and/or monitoring the flow rate of nitrogen introduced into the reaction vessel. A nitrogen inlet tube into which nitrogen is introduced and a heating mantle are purchased for the reaction vessel 3. Through this, it is possible to heat the reaction vessel containing the raw materials including polystyrene and catalyst. A condenser for condensing the decomposition product and a cold trap 4 for collecting the decomposition product liquefied by the condenser are connected to the reaction vessel. A gas meter (5) is connected behind the cold trap to measure the amount of uncondensed gas components in the condenser. An analysis device for analyzing gas components may be installed behind the cold trap, if necessary. The type of analysis device is not particularly limited as long as it can analyze gas components, and examples thereof include gas chromatography (GC) and GC-MASS analyzers.

The method of the present invention may further include an additional process, for example, a step of recovering the obtained styrene, in addition to the above thermal decomposition process, which may be the same as that applied in the known process for preparing or obtaining a styrene monomer. there is. That is, the method of the present invention may be performed in the same manner as a known method for obtaining styrene monomer through depolymerization of polystyrene, except for performing the depolymerization step.

The present invention will be described in detail through the following examples. However, the following examples do not limit the scope of the present invention.

[Experimental Example 1] Measurement of specific surface area of oxide

The specific surface area of the oxide was measured in the following order.

(1) 0.1 g of the oxide prepared in Examples and Comparative Examples was prepared as a sample.

(2) After the sample was injected into the cell, it was pretreated at 200 °C for 2 hours.

(3) The pretreated sample was put into a specific surface area analyzer (Belsorp-max, manufactured by Bel Japan), and the specific surface area of the oxide was measured under a relative pressure condition of about 0.05-0.3. In the measurement process, the Brunauner-Emmett-Teller (BET) equation was used.

[Experimental Example 2] Measurement of carbon dioxide adsorption amount of complex oxide catalyst

The amount of carbon dioxide adsorbed by the oxide (oxide catalyst, composite oxide catalyst) was measured in the following order. As equipment, Belcat basic from Bel Japan was used.

(1) 0.1 g of the oxide prepared in Examples and Comparative Examples was prepared as a sample.

(2) The sample was injected into a U-shaped quartz tube, and pretreated while flowing helium at a temperature of 150 °C for about 1 hour.

(3) Carbon dioxide was adsorbed on the surface of the sample while supplying carbon dioxide to the pretreated sample at a temperature of 30 °C for 30 minutes.

(4) The content of carbon dioxide desorbed by heat treatment up to 450 ℃ was measured.

[Experimental Example 3] Measurement of conversion rate of polystyrene, oil yield, selectivity and yield of styrene monomer

The oils obtained in the following Examples and Comparative Examples were analyzed using gas chromatography (Gas Chromatography, GC), and based on this, the pyrolysis conversion rate of polystyrene, the oil yield measurement, and the selectivity and yield of styrene monomer were measured.

The instrument used for GC analysis was Agilent's GC7890A. The equipment was equipped with DB-WAX column, Flame Ionization Detector (FID) and Auto sampler. Oil was injected into a vial that met the equipment specifications, and 0.1 μl of oil was automatically injected into the GC analyzer using an auto sampler. By changing the temperature of the oven appropriately, the measured peak was analyzed. By converting the area obtained by integrating the peak, it was possible to confirm the specific gravity occupied by each component.

[Example 1]

0.68 g of magnesium nitrate hydrate (Mg(NO ₃ ) ₂ .6H ₂ O) and 9.94 g of aluminum nitrate hydrate (Al(NO ₃ ) ₃ .9H ₂ O) were put into a mortar and mixed to disperse them evenly, thereby forming a precursor mixture. has manufactured 7.93 g of ammonium bicarbonate (NH ₃ HCO ₃ ) was added to the precursor mixture and stirred uniformly for a predetermined time using a pestle to conduct a solid phase reaction. During the reaction, carbon dioxide, hydrogen and oxygen were produced.

After a certain period of time, when the solid phase reaction was terminated as no more carbon dioxide, hydrogen and oxygen were produced (completed in approximately less than 15 minutes), the mixture was dried in a dry oven at 110 °C. Then, it was calcined at 450 °C for 6 hours to obtain a composite oxide having a composition of Mg ₁ Al ₁₀ O.

[Example 2]

A composite oxide having a composition of Mg ₁ Al ₅ O was prepared in the same manner as in Example 1, except that the contents of magnesium nitrate hydrate, aluminum nitrate, and hydrated ammonium bicarbonate were changed to 1.25 g, 9.11 g, and 7.72 g, respectively. got it

[Example 3]

A composite oxide having a composition of Mg ₁ Al ₃ O was prepared in the same manner as in Example 1, except that the contents of magnesium nitrate hydrate, aluminum nitrate hydrate, and ammonium bicarbonate were changed to 1.87 g, 8.20 g, and 7.49 g, respectively. got it

[Example 4]

A composite oxide having a composition of Mg ₁ Al ₂ O was prepared in the same manner as in Example 1, except that the contents of magnesium nitrate hydrate, aluminum nitrate hydrate, and ammonium bicarbonate were changed to 2.49 g, 7.29 g, and 7.26 g, respectively. got it

[Example 5]

A composite oxide having a composition of Mg ₁ Al ₁ O was prepared in the same manner as in Example 1, except that the contents of magnesium nitrate hydrate, aluminum nitrate, and hydrated ammonium bicarbonate were changed to 3.74 g, 5.47 g, and 6.81 g, respectively. got it

[Example 6]

A composite oxide having a composition of Mg ₂ Al ₁ O was prepared in the same manner as in Example 1, except that the contents of magnesium nitrate hydrate, aluminum nitrate, and hydrated ammonium bicarbonate were changed to 8.72 g, 6.38 g, and 11.12 g, respectively. got it

[Example 7]

A composite oxide having a composition of Mg ₃ Al ₁ O was prepared in the same manner as in Example 1, except that the contents of magnesium nitrate hydrate, aluminum nitrate, and hydrated ammonium bicarbonate were changed to 9.81 g, 4.78 g, and 10.73 g, respectively. got it

[Example 8]

A composite oxide having a composition of Mg ₅ Al ₁ O was prepared in the same manner as in Example 1, except that the contents of magnesium nitrate hydrate, aluminum nitrate, and hydrated ammonium bicarbonate were changed to 10.90 g, 3.19 g, and 10.33 g, respectively. Got it.

[Example 9]

A composite oxide having a composition of Mg ₁₀ Al ₁ O was prepared in the same manner as in Example 1, except that the contents of magnesium nitrate hydrate, aluminum nitrate, and hydrated ammonium bicarbonate were changed to 11.89 g, 1.74 g, and 9.97 g, respectively. got it

[Examples 10 to 18].

A depolymerization process of polystyrene was performed using the complex oxides prepared in Examples 1 to 9 as a catalyst (not subjected to a separate supporting treatment). Each process corresponds to Example 10 to Example 18. Except for changing the type of catalyst, the rest of the process was carried out in the same way. The above process was performed with the apparatus shown in FIG. 1 . Specifically, 0.4 g of the composite oxide prepared in the above example and 20 g of polystyrene were placed in a 100 mL round bottom flask, and the temperature was raised to 350° C. using a heating mantle, and the reaction proceeded for 2 hours. After passing the product through a condenser, the product was obtained in the form of an oil by using a cold trap.

[Comparative Example 1]

Metal oxide (MgO) was obtained in the same manner as in Example 1, except that aluminum nitrate hydrate was not used in Example 1.

[Comparative Example 2]

A metal oxide (Al ₂ O ₃ ) was obtained in the same manner as in Example 1, except that magnesium nitrate hydrate was not used in Example 1.

[Comparative Example 3]

A composite oxide having a composition of Mg ₁ Al ₂ O was obtained using a known co-precipitation method. Specifically, 4.58 g of magnesium nitrate hydrate (Mg(NO ₃ ) ₂ ^. 6H ₂ O) and 13.40 g of aluminum nitrate hydrate (Al(NO ₃ ) ₃ ^. 9H ₂ O) were dissolved in water and maintained at a pH of 10. did. Then, an aqueous solution of ammonium carbonate ((NH ₄ ) ₂ CO ₃ .10H ₂ O) was slowly dropped to precipitate. The precipitate was aged for 24 hours. After drying in a hot air dryer at 110 ° C., it was baked at 450 ° C. for 6 hours to obtain a composite oxide.

[Comparative Examples 4 to 7]

In Comparative Example 4, the catalyst was not applied, and in Comparative Examples 5 to 7, the polystyrene depolymerization reaction was performed in the same manner as in Example 10, except that the metal oxide or composite oxide of Comparative Examples 1 to 3 was used as a catalyst. proceeded

The characteristics of the catalysts according to Examples 1 to 9 and Comparative Examples 1 to 3 are shown in Table 1 below. In addition, the polystyrene depolymerization reaction results according to Examples 10 to 18 and Comparative Examples 4 to 7 are shown in Table 2 below.

Catalyst characterization catalyst composition specific surface area
(m ² /g) CO ₂ adsorption amount
(mmol/g) Example 1 Mg ₁ -Al ₁₀ -O 304 2.91 Example 2 Mg ₁ -Al ₅ -O 308 3.08 Example 3 Mg ₁ -Al ₃ -O 226 3.19 Example 4 Mg ₁ -Al ₂ -O 156 3.36 Example 5 Mg ₁ -Al ₁ -O 161 2.99 Example 6 Mg ₂ -Al ₁ -O 84 2.94 Example 7 Mg ₃ -Al ₁ -O 43 2.51 Example 8 Mg ₅ -Al ₁ -O 37 1.81 Example 9 Mg ₁₀ -Al ₁ -O 9 2.09 Comparative Example 1 MgO 4 0.04 Comparative Example 2 Al ₂ O ₃ 288 2.36 Comparative Example 3 Mg ₁ -Al ₂ -O 98 2.95

Polystyrene depolymerization reaction process catalyst conversion rate
(%) oil yield
(%) SM selectivity
(%) SM yield
(%) Example 10 Example 1 75 70 77 54 Example 11 Example 2 76 72 75 54 Example 12 Example 3 77 72 75 54 Example 13 Example 4 80 75 74 56 Example 14 Example 5 78 73 77 56 Example 15 Example 6 76 72 75 54 Example 16 Example 7 76 71 74 52 Example 17 Example 8 76 70 75 52 Example 18 Example 9 75 70 76 53 Comparative Example 4 no catalyst 70 65 75 49 Comparative Example 5 Comparative Example 1 74 69 72 50 Comparative Example 6 Comparative Example 2 69 64 72 47 Comparative Example 7 Comparative Example 3 74 69 70 49

It can be seen from Table 1 that the complex oxide of the present invention has excellent catalytic properties (high specific surface area and carbon dioxide adsorption amount) and can be produced relatively quickly.

From Table 2, when the catalyst containing the complex oxide of the present invention is applied as a catalyst for the polystyrene depolymerization reaction, polystyrene can be thermally decomposed with high conversion rate and oil yield, and the selectivity of styrene monomer, the target product of this reaction, and It can be confirmed that the yield is also high.

Claims (4)

It is prepared by a solid phase reaction and includes a complex oxide having an alkaline earth metal and a group 13 element,
The molar ratio (A / B) of the alkaline earth metal (A) and the group 13 element (B) in the composite oxide is in the range of 0.05 to 20
Catalyst for depolymerization of polystyrene. According to claim 1,
The alkaline earth metal is magnesium,
The group 13 element is aluminum,
Catalyst for depolymerization of polystyrene. Comprising the step of thermally decomposing polystyrene by applying heat to a raw material containing the catalyst of claim 1 and polystyrene,
Method for depolymerization of polystyrene. According to claim 3,
The content of the catalyst is in the range of 0.01 part by weight to 30 parts by weight relative to 100 parts by weight of the polystyrene,
Method for depolymerization of polystyrene.

Images