KR20220076183A - Catalyst and method for preparing of styrene monomer from polystyrene using the same - Google Patents

Abstract

The present invention provides a catalyst used in a reaction for thermal decomposition of polystyrene into a styrene monomer, wherein the catalyst is prepared by a solid phase reaction, and includes an alkaline earth metal; And in the presence of a composite oxide catalyst containing a group 13 element and the catalyst, it provides a method for producing a styrene monomer, comprising the step of thermally decomposing polystyrene. The method for producing a styrene monomer according to the present invention can relatively lower the thermal decomposition temperature, thereby having an energy saving effect, and increasing the selectivity of the styrene monomer, thereby increasing the yield of the styrene monomer.

Description

Catalyst and method for preparing styrene monomer from polystyrene using the same

The present invention relates to a catalyst used for pyrolysis of polystyrene into styrene monomer and a method for producing a styrene monomer using the same. Specifically, the present invention relates to a method for saving energy and for producing a styrene monomer from polystyrene with high efficiency.

With industrial development, a large amount of plastic is being used around the world. However, many plastics are discarded after use, causing many environmental problems. Waste plastics are currently being treated mainly by landfill, but the biodegradation time in the soil is long and the shortage of landfills causes serious environmental problems.

That is, the pyrolysis treatment of waste plastics has been developed with the aim of solving two problems of low-pollution treatment of waste and recovery of raw materials with one technology. On the other hand, waste polystyrene or styrene foam is easy to recover value-added styrene monomer through thermal decomposition, and other components can be recovered and used as other effective chemicals such as gasoline, which is of great interest in terms of securing economic feasibility than other types of plastic waste. being targeted

Conventionally, as a method of chemically decomposing waste polystyrene to produce a styrene monomer, a thermal pyrolysis method using only thermal energy and a catalytic pyrolysis method using a catalyst are known.

The method for producing a styrene monomer using a pyrolysis method has disadvantages such as a high thermal decomposition temperature, poor quality due to a variety of molecular weight and shape distribution of the product, and interruption of the process due to carbon deposition accumulated due to the product. In addition, in the method of producing a styrene monomer using catalytic pyrolysis, a catalyst of a strong acid or a strong base can generally be used. When a catalyst with high acidity is used, continuous cracking and hydrogenation reaction due to beta cleavage of carbon-carbon bonds. Due to this, there is a problem in that a large amount of by-products such as ethyl benzene and α-methyl styrene are generated.

Therefore, there is a need for a method for producing a styrene monomer with high selectivity.

Korean Patent Publication No. 2003-0081717

An object of the present invention is to provide a catalyst for preparing a styrene monomer and a method for preparing a styrene monomer using the same, which increases the selectivity to the styrene monomer to increase the yield of the styrene monomer.

An exemplary embodiment of the present invention is a catalyst used in a reaction for thermally decomposing polystyrene into a styrene monomer, wherein the catalyst is prepared by a solid phase reaction, and includes an alkaline earth metal; And it provides a complex oxide catalyst comprising a group 13 element.

In addition, an exemplary embodiment of the present invention provides a method for producing a styrene monomer, comprising the step of thermally decomposing polystyrene in the presence of the catalyst.

The catalyst used in the method for producing a styrene monomer according to an exemplary embodiment of the present invention can relatively lower the thermal decomposition temperature, thereby having an energy-saving effect, and increasing the selectivity of the styrene monomer, thereby increasing the yield of the styrene monomer. .

In addition, the catalyst used in the method for preparing a styrene monomer according to an exemplary embodiment of the present invention can be prepared by a simple manufacturing method, thereby shortening the manufacturing time, having high thermal stability and reusability, and showing relatively basicity. Therefore, less by-products other than the styrene monomer are produced.

1 is a view schematically showing a process for producing a styrene monomer from polystyrene, according to an embodiment of the present invention.

Advantages and features of the present invention and methods of achieving them will become apparent with reference to the embodiments described below in detail in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various different forms, and only these embodiments allow the disclosure of the present invention to be complete, and common knowledge in the art to which the present invention pertains It is provided to fully inform those who have the scope of the invention, and the present invention is only defined by the scope of the claims. Like reference numerals refer to like elements throughout.

Unless otherwise defined, all terms (including technical and scientific terms) used herein may be used with the meaning commonly understood by those of ordinary skill in the art to which the present invention belongs. In addition, terms defined in a commonly used dictionary are not to be interpreted ideally or excessively unless clearly defined in particular.

In the present specification, when a part "includes" a certain component, it means that other components may be further included, rather than excluding other components, unless otherwise stated.

Hereinafter, the present invention will be described in detail.

An exemplary embodiment of the present invention is a catalyst used in a reaction for thermally decomposing polystyrene into a styrene monomer, wherein the catalyst is prepared by a solid phase reaction, and includes an alkaline earth metal; And it provides a complex oxide catalyst comprising a group 13 element.

The catalyst according to an exemplary embodiment of the present invention has an energy saving effect by relatively lowering the thermal decomposition temperature in the reaction of thermally decomposing polystyrene into a styrene monomer, and increases the selectivity of the styrene monomer to increase the yield of the styrene monomer can increase

In addition, since the catalyst according to an exemplary embodiment of the present invention has high thermal stability and reusability, and shows relatively basicity, less by-products other than the styrene monomer may be generated.

In the present specification, the group 13 element may be boron, aluminum, gallium, indium, thallium, or nihonium. In one embodiment of the present specification, the group 13 element may be aluminum.

In the present specification, the alkaline earth metal includes beryllium, magnesium, calcium, strontium, barium or radium. In one embodiment of the present specification, the alkaline earth metal may be magnesium.

In an exemplary embodiment of the present invention, the group 13 element is aluminum, and the alkaline earth metal is magnesium. In one exemplary embodiment, the composite oxide catalyst has a structure of Mg ₃ (Al) ₁ O.

In one embodiment, the composite oxide may be prepared by a solid phase reaction by mixing a group 13 element precursor powder and an alkaline earth metal precursor powder. In one embodiment, the precursor powder may be a nitrate hydrate.

In one embodiment, the content of the alkaline earth metal in the composite oxide may be 3 moles based on 1 mole of the group 13 element.

In an exemplary embodiment of the present invention, the composite oxide is prepared by a solid-state reaction.

Conventional composite oxide catalysts have been generally prepared by co-precipitation. However, when the composite oxide catalyst is prepared by the co-precipitation method, there are problems in that the production conditions such as the co-precipitation rate are difficult, the production time is long, the initial investment cost is high, and the energy consumption is high. On the other hand, in the case of the catalyst according to an exemplary embodiment of the present invention, it is possible to shorten the production time by using a relatively simple production method, solid-phase reaction.

Another exemplary embodiment of the present invention provides a method for producing a styrene monomer, comprising the step of thermally decomposing polystyrene into a styrene monomer in the presence of the above-described catalyst.

In an exemplary embodiment of the present specification, the catalyst is added in an amount of 1 part by weight or more and 30 parts by weight or less, based on 100 parts by weight of polystyrene. When the catalyst is added in an amount of less than 1 part by weight based on 100 parts by weight of polystyrene, there is a problem that the decomposition of polystyrene is not performed well because the catalyst is too small, and the catalyst is added in excess of 30 parts by weight based on 100 parts by weight of polystyrene In this case, additional cracking and hydrogenation reactions occur to generate a large amount of by-products other than the styrene monomer, thereby lowering the final yield of the styrene monomer.

In another exemplary embodiment, the thermal decomposition may be performed at a temperature of 250 °C or higher and 500 °C or lower. When the pyrolysis temperature is less than 250 ° C., there is a problem in that polystyrene is not decomposed well. There is a problem in that the final yield of the oil containing the styrene monomer is lowered because it cannot be recovered and cannot be recovered.

1 is a view schematically showing a process for producing a styrene monomer from polystyrene, according to an embodiment of the present invention. Specifically, the styrene monomer manufacturing apparatus is provided with a regulator 1, a flow meter, and a gas meter 2 for controlling and monitoring the flow rate of nitrogen introduced into the reaction vessel. The reaction vessel 3 is provided with a nitrogen introduction tube and a heating mantle into which nitrogen is introduced, so that the reaction vessel containing polystyrene and the catalyst can be heated. In addition, the reaction vessel is provided with a condenser for condensing the decomposition product and a cold trap 4 for collecting the decomposition product liquefied by the condenser. A gas meter 5 for measuring the amount of gas components not condensed in the condenser is provided behind the cold trap 4, and optionally, an analysis device for analyzing the gas components may be installed. The analysis apparatus is not particularly limited as long as it can analyze gas components, and gas chromatography, GC-MASS, and the like may be mentioned.

In an exemplary embodiment of the present invention, in the method for preparing a styrene monomer from polystyrene, a general method for preparing a styrene monomer may be applied, but not limited thereto, except for using the catalyst described above.

Hereinafter, examples will be given to describe the present invention in detail. However, the embodiments according to the present invention may be modified in various other forms, and the scope of the present invention is not to be construed as being limited to the embodiments described below. The embodiments of the present specification are provided to more completely explain the present invention to those of ordinary skill in the art.

Preparation Example 1

19.6 g of magnesium nitrate hydrate (Mg(NO ₃ ) 2.6H ₂ O) _and 9.6 g of aluminum nitrate hydrate (Al(NO ₃ ) _{3.9H 2} O) were added to a mortar, mixed and evenly dispersed. 26.8 g of ammonium bicarbonate (NH ₃ HCO ₃ ) was added to the precursor mixture, and a solid phase reaction was performed while mixing evenly for a predetermined time using a pestle, and carbon dioxide, hydrogen, and oxygen were generated in the reaction process. After a certain period of time, when the solid phase reaction is finished, that is, when the production of carbon dioxide, hydrogen, and oxygen stops, _it is dried in a dry oven at ₁₁₀ ° C. A complex oxide catalyst having a structure was obtained.

Example 1

0.2 g of the composite oxide catalyst prepared in Preparation Example 1 and 10 g of polystyrene were put into a 100 ml round-bottom flask, and the inside was heated to 350° C., which is a reaction temperature, using a heating mantle to proceed with the reaction. The products including the styrene monomer produced by the pyrolysis reaction passed through the condenser and were obtained in the form of oil in a cold trap. The yield of the obtained oil can be calculated by comparing the weight of the injected polystyrene, and the final yield of the styrene monomer was calculated by analyzing the compound in the oil using gas chromatography (GC).

Comparative Example 1

A pyrolysis reaction of polystyrene was performed in the same manner as in Example 1, except that no catalyst was used in Example 1.

Comparative Example 2

In Example 1, a pyrolysis reaction of polystyrene was performed in the same manner as in Example 1, except that a Sn-β zeolite catalyst was used instead of the composite oxide catalyst prepared in Preparation Example 1.

Comparative Example 3

In Example 1, a pyrolysis reaction of polystyrene was performed in the same manner as in Example 1, except that an H-β zeolite catalyst was used instead of the composite oxide catalyst prepared in Preparation Example 1.

Comparative Example 4

In Example 1, the polystyrene pyrolysis reaction was performed in the same manner as in Example 1, except that a commercially available MgO catalyst was used instead of the composite oxide catalyst prepared in Preparation Example 1.

The results of the thermal decomposition of the polystyrenes of Example 1 and Comparative Examples 1 to 4 are shown in Table 1 below.

Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 catalyst base catalyst; Mg ₃ (Al) ₁ O catalyst free acid catalyst;
Sn-β zeolite acid catalyst;
H-β zeolite base catalyst;
MgO PS conversion rate (%) 82 70 61 71 74 Oil Yield (%) 76 63 53 58 71 SM Yield (%) 59 49 35 19 53 GC Area
(%, in liquid) toluene 7 7 10 11 8 EB 2 3 10 32 4 AMS 9 9 12 12 9 SM 78 78 66 33 75 Etc 4 3 2 12 4

In Table 1, PS denotes polystyrene, SM denotes styrene monomer, EB denotes ethyl benzene, and AMS denotes α-methyl styrene.

Looking at the results in Table 1, it was confirmed that the method for producing a styrene monomer according to an exemplary embodiment of the present invention has a high PS conversion rate, an oil yield, and a high styrene monomer yield.

Claims (5)

As a catalyst used in the reaction of pyrolysis of polystyrene to styrene monomer,
The catalyst is prepared in a solid phase reaction,
alkaline earth metal; And a composite oxide catalyst comprising a group 13 element. According to claim 1,
The group 13 element is aluminum,
The alkaline earth metal is a catalyst that is magnesium. A process for producing a styrene monomer, comprising the step of pyrolyzing polystyrene in the presence of the catalyst according to claim 1 or 2 . 4. The method of claim 3,
The catalyst is, based on 100 parts by weight of polystyrene, 1 part by weight or more and 30 parts by weight or less of the method for producing a styrene monomer. 4. The method of claim 3,
The thermal decomposition step is a method for producing a styrene monomer that is carried out at a temperature of 250 ℃ or more, 500 ℃ or less.

Images