KR20230068533A - Catalyst for Depolymerisation of Polyethylene Terephthalate and Preparing Method of the Same - Google Patents

Abstract

The present invention relates to a catalyst for a depolymerization reaction of polyethylene terephthalate and a manufacturing method thereof, and more specifically, to a catalyst for a depolymerization reaction of polyethylene terephthalate, which is not only colorless, but also has excellent durability while producing BHET in high yield in a glycolysis depolymerization reaction using pigment-containing colored PET as a raw material, and which can maintain the yield even if the catalyst is repeatedly reused as the catalyst is advantageous to be recovered and reused, and a manufacturing method thereof.

Description

Catalyst for Depolymerization of Polyethylene Terephthalate and Preparing Method of the Same}

The present invention relates to a catalyst for depolymerization of polyethylene terephthalate and a method for preparing the same, and more particularly, to a catalyst for depolymerization of polyethylene terephthalate used in a glycolysis depolymerization of polyethylene terephthalate and a method for preparing the same It is about.

Polyethylene terephthalate (hereinafter referred to as 'PET') is a polymer manufactured through esterification and condensation polymerization of terephthalic acid (TPA) or dimethyl terephthalate (DMT) and ethylene glycol (EG) as main raw materials. It has physical properties, processability, economic efficiency, etc., and is eco-friendly, so it is used in a wide range of fields such as food and beverage containers and packaging materials, textiles for clothing, films, and others.

As such PET is the most widely used among general synthetic resins, a large amount of PET waste is generated every year, and it has recently become a major culprit of serious environmental pollution due to its property of not being easily decomposed naturally. Accordingly, recycling of waste such as waste PET, such as beverage bottles that are discarded after use, is emerging as a great concern.

Physical or chemical methods are largely used to recycle waste PET. The physical recycling method is to collect, wash, and pulverize waste PET and reuse it. It is difficult to apply to colored PET containing pigments, etc., and its purity cannot be guaranteed, so it is not widely applied, and physical properties are not secured.

Meanwhile, the chemical recycling method is to break the ester bonds of waste PET and oligomers regardless of the degree of contamination, and is divided into glycolysis, which is an oligomer recovery method, and methanolysis, and hydrolysis, which are monomer recovery methods. Specifically, in order to chemically recycle PET, the PET polymer chain is decomposed through decomposition reactions such as glycolysis by glycol-based compounds, methanolysis by methanol, and hydrolysis by water, and then goes through a separation and purification process. Monomers such as BHET, DMT, and TPA or polyester oligomers were obtained. The materials thus obtained can be used to synthesize polyesters.

In particular, the glycolysis depolymerization reaction has the advantage that depolymerization is performed at a lower temperature and pressure than other chemical recycling processes, and the treatment process is simple. This glycolysis depolymerization reaction is specifically a method of recovering bis-hydroxyethyl terephthalate (BHET) by reacting PET with ethylene glycol (EG). BHET and oligomers are produced using an excess of glycol, usually EG, in the temperature range of 180° C. to 250° C. under pressure. Before the produced BHET is used to produce new PET polymers, it is usually necessary to undergo a purification process to remove catalysts or pigments using melt filtration under pressure. The depolymerization is usually performed in the presence of a transition metal acetate catalyst such as zinc acetate or lithium acetate or a zinc-based catalyst. However, these conventional catalysts have disadvantages in that selectivity of BHET is low during reaction equilibrium and separation and recovery of the catalyst are difficult.

Homogeneous catalysts such as zinc acetate catalysts have a fast reaction rate and produce BHET well, but the BHET monomer is polymerized into a dimer or trimer, which again undergoes a decomposition process to reach a reaction equilibrium state. At this time, the yield of BHET is about 90% and the yield of dimer is about 10%. In particular, the yield of BHET in a reaction equilibrium state varies depending on the reaction conditions, that is, the PET/EG ratio, and the yield of BHET in a reaction equilibrium state increases as an excessive amount of EG is used. As such, the homogeneous catalyst has a disadvantage in that the selectivity of BHET is low during reaction equilibrium. Another disadvantage is that it is difficult to separate and recover the catalyst. In order to recover all the active components of the homogeneous catalyst, a distillation process that consumes a lot of energy must be performed. Also, if some metal components remain, the final product (BHET) Since it remains, there is a limit to its use in the production of PET for drinking containers.

Accordingly, Korean Patent Publication No. 2021-0067749 discloses a recycling method of waste PET using a fibrous perovskite catalyst in the glycolysis depolymerization reaction of waste PET to obtain BHET in high yield, but the catalyst of the prior art Even if a heterogeneous catalyst such as the above is applied, depolymerization generated in the depolymerization reaction has a high molecular weight, so it is difficult to separate and recover the catalyst without catalyst residue, and when reused, leaching of catalytically active components occurs, making it impossible to obtain high-purity BHET. There was a problem.

In addition, Korean Patent Publication No. 2021-0066354 discloses a method of generating BHET after adsorbing and removing pigments using Teflon resin before, after, and during the depolymerization process to remove pigments during the depolymerization process of colored PET. The prior art also had a problem in that a pigment purification process had to be performed several times before, after, and in the middle of the depolymerization process in order to remove the pigment from the colored PET.

Accordingly, there is a need to develop a technology capable of stably reusing the depolymerization catalyst after use while obtaining high-purity BHET in high yield by the glycolysis depolymerization method of PET without going through multiple purification processes.

Korean Patent Publication No. 2021-0067749 (published date: 2021.06.08) Korean Patent Publication No. 2021-0066354 (published date: 2021.06.07)

One object of the present invention is to produce BHET in a high yield in the glycolysis depolymerization reaction of PET, to have excellent durability, and to maintain the yield of BHET even if the catalyst is repeatedly reused because it is advantageous to recover and reuse the catalyst. It is an object of the present invention to provide a catalyst for depolymerization of polyethylene terephthalate and a method for preparing the same.

Another object of the present invention is to provide a catalyst for depolymerization of polyethylene terephthalate capable of obtaining BHET in high yield simultaneously with the removal of pigment in the glycolytic depolymerization of colored PET containing pigments and a method for preparing the same. there is.

Another object of the present invention is to provide a method for producing BHET by glycolysis depolymerization of PET using the above catalyst.

In order to achieve the above object, one embodiment of the present invention is a catalyst for depolymerization of polyethylene terephthalate, wherein the catalyst is characterized in that iron, a catalytically active component, is surrounded by a carbon material. A catalyst for a depolymerization reaction is provided.

In a preferred embodiment of the present invention, the catalyst may be formed by carbonizing an iron-organic ligand skeleton.

In a preferred embodiment of the present invention, the iron-organic ligand framework may be characterized in that it is a Fe-based MOF in which iron (Fe) is the central metal.

In a preferred embodiment of the present invention, the depolymerization of polyethylene terephthalate may be a reaction between polyethylene terephthalate and glycol.

Another embodiment of the present invention includes preparing a catalyst for the depolymerization reaction of polyethylene terephthalate by carbonizing an iron-organic ligand framework in an inert atmosphere, wherein iron, a catalytically active component, is converted into a carbon material. Provided is a method for preparing a catalyst for depolymerization of polyethylene terephthalate, characterized in that it is surrounded.

In another preferred embodiment of the present invention, the iron-organic ligand framework may be a Fe-based MOF in which iron (Fe) is the central metal.

In another preferred embodiment of the present invention, the iron-organic ligand skeleton may be obtained by mixing an iron precursor and an organic ligand compound in an organic solvent at a molar ratio of 1:0.5 to 3.0 and then reacting them.

In another preferred embodiment of the present invention, the method for preparing the catalyst for the depolymerization of polyethylene terephthalate further includes carbon precursor to the iron-organic ligand skeleton prior to carbonization of the iron-organic ligand skeleton to perform carbonization. that can be characterized.

In another preferred embodiment of the present invention, the carbon precursor is furfuryl alcohol, divinylbenzene, urea, glucose, sucrose ethylene glycol, glycerol (glycerol), xylitol (xylitol) and melamine (melamine) may be characterized in that at least one selected from the group consisting of.

In another preferred embodiment of the present invention, the carbonization may be performed at 600 ° C to 1200 ° C.

Another embodiment of the present invention provides a method for preparing BHET, characterized in that BHET is produced by reacting polyethylene terephthalate with glycol in the presence of the catalyst for depolymerization of polyethylene terephthalate.

In another preferred embodiment of the present invention, the glycol may be characterized in that 100 parts by weight to 3000 parts by weight based on 100 parts by weight of polyethylene terephthalate.

The catalyst according to the present invention can produce BHET with a high conversion rate and yield by promoting the glycolysis depolymerization reaction of PET with high catalytic activity. Not only does it not disappear, but as the catalyst itself exhibits magnetism, the catalyst can be easily separated and recovered from the reaction product using a magnet, and the catalyst activity can be maintained even when the catalyst is reused.

In addition, since the catalyst according to the present invention includes a carbon body, it is possible to obtain BHET in high yield simultaneously with the removal of pigment, and thus an additional pre-step process for classifying and selecting PET raw materials or a purification step process for removing pigments. can be omitted, so it can be used industrially very usefully.

1 is a SEM picture and a TEM picture of a catalyst and an iron-organic ligand framework prepared in Preparation Example 1 of the present invention, (a) is a SEM picture of an iron-organic ligand framework, and (b) is Preparation Example 1 It is a SEM picture of the catalyst prepared in, (c) is a TEM picture of the catalyst prepared in Preparation Example 1, (d) is an enlarged TEM of (c).
Figure 2 is an XRD measurement graph of the catalyst for repeated reactions of the catalyst according to the present invention.

Unless defined otherwise, 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 nomenclatures used herein are those well known and commonly used in the art.

Terms such as 'having', 'includes', 'includes' or 'has' described in this specification indicate that a feature, numerical value, step, operation, component, part or combination thereof described in the specification exists. It does not rule out the possibility that other features, values, steps, operations, components, parts, or combinations thereof not mentioned may exist or be added.

Hereinafter, the catalyst for depolymerization of polyethylene terephthalate and the preparation method thereof according to the present invention will be described in detail.

The inventors of the present invention have found that a catalyst obtained by carbonizing an iron-organic ligand skeleton containing iron as the central metal of the metal-organic framework produces BHET (bis-hydroxyethyl terephthalate) in a higher yield than conventional catalysts for depolymerization of polyethylene terephthalate. It is confirmed that the catalyst active material is not leached or lost due to excellent durability, the catalyst used after the reaction can be easily separated and recovered from the reaction product, and the catalyst activity can be maintained even when the catalyst is reused. and completed the present invention.

In addition, it was confirmed that the catalyst for depolymerization of polyethylene terephthalate according to the present invention can obtain BHET in high yield simultaneously with pigment removal even in the glycolytic depolymerization of pigment-containing colored PET.

The catalyst for depolymerization of polyethylene terephthalate according to the present invention is characterized in that iron, which is a catalytically active component, is surrounded by a carbon material.

As a preferred embodiment of the carbon body, the carbon body may include a carbon body prepared by heat-treating a metal organic framework at a high temperature.

The metal-organic framework (MOF) is a hybrid material in which a metal or metal-organic cluster is connected to an organic linker through a coordinate bond to form a skeleton, and the metal-organic cluster is a node in the skeleton. ) can be Therefore, MOF is a crystalline compound having a molecular or nano-sized pore structure, and is also referred to as 'organic-inorganic hybrid nanoporous body' or 'porous coordination polymers'.

The metal organic framework (MOF) is basically a porous material having properties similar to those of zeolite, and is synthesized using solvothermal synthesis, microwave and ultrasonic synthesis, mechanical friction, and ions using an ionic liquid as a synthetic solvent. It can be easily prepared by an ionothermal synthesis method. For example, in the solvothermal synthesis method, a transition metal precursor, an organic ligand, and an organic solvent are placed in a container, sealed, and heated to form a metal-organic framework (MOF). ) can be easily prepared.

Further, in the metal-organic framework (MOF), it is possible to control the activity of a catalyst, the size of pores, and the diameter of a window by changing the components of a central metal-organic ligand. Specifically, when the central metal of the metal-organic framework is changed to a catalytically active component in the depolymerization reaction of polyethylene terephthalate, a catalyst in which the catalytically active component is fixed inside the organic ligand skeleton can be prepared without additional catalytically active components being supported or impregnated therewith. can

Accordingly, in the present invention, by using the above-described characteristics of the metal-organic framework (MOF), iron, which exhibits high activity in the glycolysis depolymerization reaction of polyethylene terephthalate and exhibits magnetism, is used as the central metal of the metal-organic framework (MOF). By immobilizing organic ligands as catalytically active components and carbonizing them, the carbon-carbon bonds of the organic ligands constituting the skeleton in the metal-organic framework are broken, and new carbon-carbon bonds are created, forming a carbon body surrounding iron, the central metal. It was possible to obtain a catalyst in which iron, a catalytically active component, was surrounded by a carbon body.

In such a catalyst, iron, a catalytically active component, is physically and chemically encapsulated in the internal space of the metal-organic framework, so that it is not leached or lost during the reaction, and iron, a catalytically active component, forms a chemical bond with the organic ligand constituting the catalyst skeleton, resulting in It is possible to prevent the deterioration of catalytic activity that can occur, and in the case of depolymerization generated in the depolymerization reaction, it is easy to separate and recover the catalyst using a magnet even when it is difficult to separate the catalyst due to its high molecular weight.

Metalorganic frameworks (hereinafter referred to as iron-organic ligand frameworks) containing iron as a central metal are non-limiting examples, such as PCN-250, PCN-600, Fe-MOF-74, MIL53, MIL-88, MIL -89, MIL-96, MIL-100, MIL-101, MIL-102, MIL-126, MIL-127, and one or more functionalized MOFs thereof may be used.

In addition, the iron-organic ligand framework can be applied without limitation as long as it is a method capable of preparing a metal-organic framework containing iron as a central metal, preferably by mixing an iron precursor and an organic ligand compound in an organic solvent, By reacting, an iron-organic ligand skeleton can be prepared. In this case, the iron precursor and the organic ligand compound may be mixed in a molar ratio of 1:0.5 to 3.0.

The iron precursor may be at least one selected from the group consisting of organic compounds and inorganic compounds containing iron ions, and specifically, may be iron chlorides, sulfides, nitrides, hydrates, metallic iron powders, and the like.

In addition, the organic ligand compound of the metal-organic framework is also called a linker, and any organic compound having a functional group that can be coordinated is possible, and the functional group that can be coordinated is a carboxylic acid group, a carboxylic acid anionic group, an amino group (-NH ₂ ), imino group (-NH), amide group (-CONH ₂ ), sulfonic acid group (-SO ₃ H), sulfonic acid anion group (-SO ₃ -), methanedithioic acid group (-CS ₂ H) , a methanedithioic acid anion group (-CS ₂ -), a pyridine group or a pyrazine group, and the like may be exemplified. In order to induce a more stable organic-inorganic hybrid, an organic compound having two or more coordinating sites, for example bidentate or tridentate, is advantageous. As organic compounds, if there is a site for coordination, neutral organic compounds such as bipyridine and pyrazine, terephthalate, naphthalene dicarboxylate, benzene tricarboxylate, glutarate, succinate, etc. Anionic organic compounds as well as cationic materials are possible.

In the case of the carbonic acid anion, for example, an anion having an aromatic ring such as terephthalate, an anion of a linear carbonic acid such as formate, or an anion having a non-aromatic ring such as cyclohexyl dicarbonate may be used. Organic compounds having a coordination site as well as organic compounds that potentially have a coordination site and are converted to be coordinated under reaction conditions can be used. That is, even if an organic acid such as terephthalic acid is used, it can be combined with a metal component as terephthalate after the reaction. Representative examples of organic compounds that can be used include benzenedicarboxylic acid, naphthalenedicarboxylic acid, benzenetricarboxylic acid, naphthalenetricarboxylic acid, pyridinedicarboxylic acid, bipyridyldicarboxylic acid, formic acid, oxalic acid, malonic acid, succinic acid, glutaric acid, and hexane. organic acids selected from dioic acid, heptanedioic acid, or cyclohexyldicarboxylic acid, and their anions, pyrazine, bipyridine, and the like. In addition, one or more organic compounds may be mixed and used.

On the other hand, organic solvents used in the synthesis of metal-organic frameworks other than the iron precursor and organic ligand compounds are water, alcohols such as methanol, ethanol, and propanol, ketones such as acetone and methyl ethyl ketone, hexane, heptane, and octane. Any material such as hydrocarbons can be used, and two or more solvents can be mixed and used, and water is the most suitable.

The reaction between the iron precursor and the organic ligand compound for the synthesis of the metal-organic framework is not practically limited, but may be at 100 °C to 300 °C, preferably at a temperature of 100 °C to 250 °C. If the reaction temperature is too low, the reaction rate is slow, making it ineffective. If the reaction temperature is too high, it is easy to obtain a material without pores. It is economical.

By carbonizing the iron-organic ligand framework, organic clusters in the iron-organic ligand framework or carbon-carbon bonds of organic ligands are generated so that a carbon having a hexagonal crystal structure is the central metal of the iron-organic ligand framework. It can be produced in a form surrounded by phosphorus iron.

At this time, the carbonization can be carried out at 600 ° C. to 1200 ° C. for 1 to 6 hours, and the carbonization atmosphere is preferably carried out under an inert gas mixed with helium, nitrogen, argon or some hydrogen for metal reduction.

When the carbonization temperature is less than 600 ° C. or 1 hour, conversion to a carbon body does not occur and some structures of the MOF may be broken or may remain in a dry state. When the carbonization temperature exceeds 1200 ° C. or 6 hours, Due to the solid solution reaction of the metal, the dispersity of iron may be greatly reduced, and problems in that the iron moves out of the carbon body and the surface area is rapidly reduced may occur.

The catalyst according to the present invention is produced in a form in which iron, a catalytically active component, is surrounded by a carbon body by carbonizing a metal-organic framework containing iron as a central metal at a high temperature, thereby preventing leaching or disappearance of the catalytically active component, and reacting In the case of using colored PET containing pigments as a raw material, it can also perform the role of adsorbing and removing pigments, so the additional pre-step process of classifying and sorting PET raw materials or the purification step process to remove pigments can be omitted. and colorless BHET can be prepared from colored PET.

Meanwhile, the catalyst according to the present invention may be carbonized by adding a carbon precursor to the iron-organic ligand framework before the carbonization step in order to increase the specific surface area and adsorption capacity of the catalyst by increasing the carbon content.

In this case, less than 50 parts by weight of the carbon precursor may be added based on 100 parts by weight of the iron-organic ligand framework. When the carbon precursor exceeds 50 parts by weight based on 100 parts by weight of the iron-organic ligand framework, the carbon precursor is present in excess outside the iron-organic ligand framework particles, so the surface area and pore size are reduced, and the iron active component A problem in that the thickness of the surrounding carbon body is increased and the catalytic activity is lowered may occur. It is preferable that the thickness of the carbon body is 10 nm to 100 nm.

In addition, the carbon material preferably has a specific surface area of 100 m ² /g or more and a pore volume of 0.1 cm ³ /g or more.

The carbon precursor is furfuryl alcohol, divinylbenzene, urea, glucose, sucrose ethylene glycol, glycerol, xylitol and melamine (melamine) may be one or more selected from the group consisting of.

The catalyst according to the present invention increases the carbon content of the iron-organoligand skeleton by adding a carbon precursor, thereby improving the adsorption capacity for the pigment contained in the colored PET while maintaining the catalytic activity.

In addition, the present invention provides a method for producing BHET, characterized in that BHET is prepared by reacting polyethylene terephthalate with glycol in the presence of the catalyst for depolymerization of polyethylene terephthalate (PET).

In this case, the catalyst for depolymerization of polyethylene terephthalate (PET) according to the present invention may be used in an amount of 3 parts by weight to 20 parts by weight based on 100 parts by weight of polyethylene terephthalate. When the above range is satisfied, the glycolysis reaction efficiency is excellent and effective in terms of increasing the reactivity, but this is only one non-limiting example and is not limited to the above numerical range.

The polyethylene terephthalate is a reaction raw material for producing BHET, and may be colorless polyethylene terephthalate and/or colored polyethylene terephthalate containing pigments, and may be new material and/or used waste.

In addition, the glycol may be used as one or two or more of ethylene glycol, diethylene glycol, triethylene glycol, glycerol, propanediol, butanediol, pentanediol, hexanediol, and the like, but is not limited thereto. The glycol may be used in an amount of 100 to 3000 parts by weight, preferably 400 to 2000 parts by weight, based on 100 parts by weight of polyethylene terephthalate. If the glycol content is less than 100 parts by weight based on 100 parts by weight of polyethylene terephthalate, the reaction time may be extended and a large amount of high molecular weight PET component may remain, and if it exceeds 3000 parts by weight, residual glycol ash As the quantity increases, a problem in that the recovery process time becomes longer may occur.

The depolymerization reaction of polyethylene terephthalate and glycol may be carried out at 180 °C to 250 °C for 1 hour to 10 hours under atmospheric pressure, preferably at 190 °C to 230 °C for 1 hour to 5 hours. When the reaction is carried out at less than 180 ° C, the reaction time may take too long because the depolymerization rate is slow, and when the temperature exceeds 250 ° C, the pressure in the reactor increases due to the volatilization of glycol, and the produced BHET is converted into a dimer or A problem of conversion to oligomers may occur. In addition, when the reaction time is less than 1 hour, the depolymerization rate may be lowered, and when the reaction time exceeds 10 hours, there is no change in the depolymerization rate and the reaction equilibrium between the BHET monomer and the dimer is achieved. It is preferable to keep it within the above range.

After completion of the reaction, the temperature may be lowered to 100 °C and then the product may be discharged from the reactor. In the depolymerization reaction, process sludge generated in the PET synthesis process and low boiling point organic compounds or moisture present in PET can be removed, and when the catalyst is recovered, it can be separated and recovered from reactants and products using a magnet.

Hereinafter, the present invention will be described in more detail through examples. Since these examples are intended to illustrate the present invention only, the scope of the present invention should not be construed as being limited by these examples.

<Preparation Example 1: Preparation of Fe@C Catalyst>

10 g of MIL-100 (Fe) whose central metal is iron was placed in a boat-type alumina crucible, and the crucible was placed in a tube-type furnace. While injecting Ar, the temperature was raised from room temperature to 800° C. at 5° C./min, carbonized at 800° C. for 3 hours, and then cooled at room temperature to prepare a catalyst (Fe@C) in which iron was encapsulated in a carbon body.

The prepared catalyst is shown in FIG. 1 by measuring catalyst morphological characteristics using a scanning electron microscope (SEM) (Tescan Mira 3 LMUFEG, acceleration voltage: 10 kV) and a transmission electron microscope (TEM) (Technai G2 Retrofit). .

As shown in FIG. 1, it was confirmed that the prepared catalyst was in a form in which iron was surrounded by a carbon body.

<Preparation Example 2: Preparation of Fe@C-FA Catalyst>

0.5 g of furfuryl alcohol dispersed in 2 g of ethyl alcohol was impregnated with 1.0 g of MIL-100 (Fe) whose central metal was iron, and the furfuryl alcohol was polymerized while evaporating ethyl alcohol at 50 °C. It was then placed in a boat-type alumina crucible, and the crucible was placed in a tube-type furnace. While injecting Ar, the temperature was raised from room temperature to 800° C. at 5° C./min, carbonized at 800° C. for 3 hours, and then cooled at room temperature to prepare a catalyst (Fe@C-FA) surrounded by iron in a carbon body.

<Comparative Preparation Example 1: Fe ₃ O ₄ /C Catalyst Manufacturing>

Put 1.0 g of activated carbon (Sigma-Aldrich) and 0.362 g of Fe(NO ₃ ) ₃ 9H ₂ O into a 250 ml three-necked flask containing 50 ml of degassed distilled water, disperse in an ultrasonic bath at room temperature for 60 minutes, and then disperse in Ethylene. After adding 0.9 g of diamine, it was dispersed by ultrasonic treatment for 30 minutes. Then, it was put into a 100 ml hydrothermal reactor, reacted at 180 °C and 400 rpm for 12 hours, cooled, and filtered. The filtered material was washed with 250 ml of degassed distilled water and 100 ml of absolute ethanol, dried at 100 °C for 24 hours, and then calcined at 500 °C under Ar conditions to form a catalyst (Fe ₃ O ₄ / C) was prepared.

<Example 1>

Example 1-1

2 g of polyethylene terephthalate (PET, Lotte Chemical) cut into 0.5 cm × 0.5 cm size, 20 g of ethylene glycol (EG) and 0.1 g of the catalyst prepared in Preparation Example 1 were added to a 250 ml three-necked flask, and the mixture A depolymerization reaction was performed by stirring at 400 rpm for 3 hours at 190 °C under a reflux system. After completion of the reaction, the catalyst was separated and recovered using magnetism, filtered at high temperature to remove unreacted PET, and then the yield of BHET and by-products such as dimer were calculated using HPLC. The filtered unreacted PET was washed with distilled water and acetone, dried, and the mass was measured to calculate the PET conversion.

Examples 1-2 to 1-6

BHET was prepared in the same manner as in Example 1-1, but with the catalyst content and ethylene glycol content shown in Table 1.

<Examples 2 to 4>

BHET was prepared in the same manner as in Example 1-1, but under the conditions shown in Table 1.

<Comparative Example 1>

BHET was prepared in the same manner as in Example 1-1, but BHET was prepared without adding a catalyst.

<Comparative Examples 2 to 5>

BHET was prepared in the same manner as in Example 1-1, but under the conditions shown in Table 1.

In the table below, colorless PET is polyethylene terephthalate (PET, Lotte Chemical), and orange PET (PET, LG Household & Health Care) is used.

Example, Comparative Example Reaction conditions division catalyst PET EG
(g) reaction
temperature
(℃) reaction
hour
(hr) manufacturing example sign weight (g) color weight (g) Example 1-1 Preparation Example 1 Fe@C 0.10 colorless 2.0 20 190 3 Example 1-2 Preparation Example 1 Fe@C 0.20 colorless 2.0 20 190 3 Examples 1-3 Preparation Example 1 Fe@C 0.05 colorless 2.0 20 190 3 Example 1-4 Preparation Example 1 Fe@C 0.02 colorless 2.0 20 190 3 Example 1-5 Preparation Example 1 Fe@C 0.01 colorless 2.0 20 190 3 Example 1-6 Preparation Example 1 Fe@C 0.25 colorless 5.0 20 190 3 Example 2 Preparation Example 1 Fe@C 0.25 Orange 5.0 20 190 3 Example 3 Preparation Example 2 Fe@C-FA 0.10 colorless 2.0 20 190 3 Example 4 Preparation Example 2 Fe@C-FA 0.25 Orange 5.0 20 190 3 Comparative Example 1 - - colorless 2.0 20 190 3 Comparative Example 2 zinc acetate Zn-Acet 0.10 colorless 2.0 20 190 3 Comparative Example 3 zinc acetate Zn-Acet 0.25 Orange 5.0 20 190 3 Comparative Example 4 Comparative Manufacturing Example 1 Fe ₃ O ₄ -AC 0.10 colorless 2.0 20 190 3 Comparative Example 5 Comparative Manufacturing Example 1 Fe ₃ O ₄ -AC 0.25 Orange 5.0 20 190 3

<Experimental Example 1: Evaluation of Catalyst Characteristics>

In order to evaluate the characteristics of the catalysts prepared in Preparation Examples 1 and 2, the specific surface area was evaluated using the Brunauer-Emmett-Teller (BET) method from the nitrogen adsorption results, and the pore volume was P / P0 = 0.99 was measured by the single point method, and the pore size distribution was measured using the Barrett-Joyner-Halenda method and shown in Table 2, respectively.

Catalyst characteristics analysis results according to the catalyst manufacturing method division Specific surface area (m ² /g) Pore volume (cm ³ /g) Average pore size (nm) Preparation Example 1 Fe@C 233.3 0.32 5.5 Preparation Example 2 Fe@C-FA 244.0 0.19 7.0

As shown in Table 2, in the case of the catalyst of Preparation Example 2 in which the catalyst of Preparation Example 1 was mixed with the carbon precursor, the pore volume decreased and the specific surface area increased compared to the catalyst of Preparation Example 1.

<Experimental Example 2: Catalytic activity evaluation>

In order to compare and analyze the BHET yield according to the catalyst content, the PET conversion rate and the BHET yield for BHET obtained in Examples 1-1 to 1-6 were calculated according to the following formulas 1 and 2, respectively, and the results are shown in Table 3 below. . All of the catalysts in Table 3 were Fe@C, in which iron produced in Preparation Example 1 was surrounded by a carbon body, and PET was colorless PET.

In addition, in order to compare and analyze the BHET yield according to the type of catalyst, the PET conversion rate and BHET yield for BHET obtained in Example 1-1, Example 3 and Comparative Examples 1, 2, and 4 were calculated by the following equations 1 and 2, respectively. , The results are shown in Table 4 below. PET in Table 4 was colorless PET.

[Equation 1] PET conversion rate (%) = {(Initial PET mass (g) - (PET mass after reaction (g)) / (Initial PET mass (g))} × 100

[Equation 2] BHET yield (%) = {(number of moles of BHET produced)/(number of moles of initial PET)} × 100

PET conversion test results according to the weight ratio of raw materials (colorless PET, 3 hr reaction at 190 ° C) division PET EG
(g) catalyst PET
conversion rate
(%) BHET
transference number
(%) Dimer
transference number
(%) weight (g) type weight (g) Compared to PET (wt%) Example 1-1 2.0 20.0 Fe@C 0.10 5.0 100 97.0 3.0 Example 1-2 2.0 20.0 Fe@C 0.20 10.0 100 96.7 3.3 Example 1-3 2.0 20.0 Fe@C 0.05 2.5 100 96.8 3.2 Example 1-4 2.0 20.0 Fe@C 0.02 1.0 97.5 94.1 3.4 Example 1-5 2.0 20.0 Fe@C 0.01 0.5 86.5 82.5 4.2 Example 1-6 5.0 20.0 Fe@C 0.25 5.0 100 89.8 9.6

As shown in Table 3, under the condition that the weight of EG is 10 times the weight of PET, the PET conversion rate and BHET yield change according to the catalyst content (wt% of catalyst relative to the weight of PET), especially when the catalyst content is 1.0 wt. % or more, it was confirmed that the conversion rate of PET was 97% or more and the yield of BHET was 94% or more. In addition, it can be seen that the yield of BHET decreases when the ratio of EG to PET decreases as in Examples 1-6.

PET conversion test results for each type of catalyst (colorless PET, 3 hr reaction at 190 ° C) division PET EG
(g) catalyst PET
conversion rate
(%) BHET
transference number
(%) Dimer
transference number
(%) weight (g) type weight (g) Compared to PET (wt%) Example 1-1 2.0 20.0 Fe@C 0.10 5.0 100 97.0 3.0 Example 3 2.0 20.0 Fe@C-FA 0.10 5.0 100 96.9 3.1 Comparative Example 1 2.0 20.0 - - - 6.0 1.7 3.0 Comparative Example 2 2.0 20.0 zinc acetate 0.10 5.0 100 95.3 4.7 Comparative Example 4 2.0 20.0 Fe ₃ O ₄ -AC 0.10 5.0 42.7 29.7 6.4

As shown in Table 4, Comparative Example 1 in which no catalyst was added showed almost no PET conversion, and when a catalyst was used, the PET conversion rate clearly increased.

However, according to the present invention, the PET conversion and BHET yields of Examples 1-1 and 3 prepared by coating the surface of iron particles with carbon were higher than those of Comparative Examples 1, 2, and 4.

<Experimental Example 3: Catalytic activity measurement according to catalyst reuse>

In order to measure the activity according to the reuse of the catalyst, the reaction was carried out in the same way as in Example 1-1 using the catalyst of Preparation Example 1, and after the reaction was completed, the catalyst used in the reaction was reused as it is and the same reaction was carried out again. The experiment was repeated 20 times. After each reaction was completed, the product was recovered and analyzed, and the results are shown in Table 5 below. In addition, XRD data of the catalyst after each reaction was completed was analyzed, and the results are shown in FIG. 2 .

Catalyst repeated use test results (Preparation Example 1 catalyst, colorless PET, 3 hr reaction at 190 ° C.) number of iterations PET conversion rate (%) BHET yield (%) Dimer yield (%) 1 time 100 96.9 3.1 Episode 2 100 96.1 3.9 3rd time 100 96.3 3.7 4 times 100 96.1 3.9 5 times 100 96.1 3.9 6 times 100 96.4 3.6 Episode 7 100 96.3 3.7 Episode 8 100 96.4 3.6 Episode 9 100 96.4 3.6 10 times 100 96.9 3.1 Episode 11 100 96.2 3.8 Episode 12 100 96.3 3.7 Episode 13 100 96.2 3.8 Episode 14 100 96.3 3.7 Episode 15 100 96.2 3.8 Episode 16 100 96.3 3.7 Episode 17 100 96.1 3.9 Episode 18 100 96.2 3.8 Episode 19 100 96.3 3.7 20 times 100 96.1 3.9

As shown in Table 5, in the case of the catalyst of Preparation Example 1, even when reused 20 times, the conversion rate of PET was 100% and the BHET selectivity was 96% or more. It was confirmed that the catalytic activity was maintained without leaching of the catalytically active component.

In addition, as shown in FIG. 2, whenever the depolymerization reaction was repeatedly performed, the size of the peak shown in the XRD data of the catalyst remained unchanged, confirming that the activity and components of the catalyst were stably maintained even when reused.

On the other hand, in the case of the catalyst of Comparative Preparation Example 1 in which the catalytically active component was not surrounded by a carbon body, it was confirmed that the reaction activity was low (PET conversion rate of 42.7%), and the catalyst was leached and rapidly deactivated when reused (see Table 6 below).

Catalyst repeated use test results (Comparative Preparation Example 1 catalyst, colorless PET, 3 hr reaction at 190 ° C.) number of iterations PET conversion rate (%) BHET yield (%) Dimer yield (%) 1 time 42.7 29.7 6.4 Episode 2 26.8 21.7 5.8

<Experimental Example 5: Catalytic activity measurement according to the application of colored PET>

In the depolymerization reaction of colored PET, the PET conversion and BHET yields for BHET obtained in Examples 2 and 4 and Comparative Examples 3 and 5 were calculated according to Equations 1 and 2, respectively, in order to compare and analyze the yield of BHET according to the type of catalyst, The presence or absence of a pigment contained in the obtained BHET was visually observed.

Pigment removal test results using colored PET division Example 2 Example 4 Comparative Example 3 Comparative Example 5 catalyst Preparation Example 1 Preparation Example 2 Zn(OAc) ₂ Comparative Preparation Example 1 Conversion rate (%) 100 100 100 49.7 BHET yield (%) 89.2 90.2 87.8 32.8 Dimer yield (%) 10.0 9.8 9.7 7.8 oligomer yield (%) 0.7 - 0.7 8.8

In the case of the BHET obtained in Examples 2 and 4, it was confirmed that the pigment was removed because the orange color was clearly removed even when observed with the naked eye compared to the BHET obtained in Comparative Examples 3 and 5. In particular, in the case of the BHET obtained in Example 4, it was confirmed that the BHET obtained from colorless PET exhibited similar transparency to the BHET of Example 1.

<Experimental Example 6: Catalyst stability evaluation according to the application of colored PET>

In the depolymerization reaction of colored PET, the reaction was conducted in the same manner as in Example 1-1 to which the catalyst of Preparation Example 1 was applied in order to measure the stability of the catalyst according to reuse, and after the reaction was completed, the catalyst used in the reaction was removed. It was reused as it was and the experiment was repeated 10 times in the same way. After each reaction was completed, the yield and conversion rate of the product produced were measured and shown in Table 8.

Pigment removal test result when using catalyst repeatedly for colored PET division PET conversion rate (%) BHET yield (%) Dimer yield (%) 1 time 100 96.4 3.6 Episode 2 100 96.6 3.4 3rd time 100 96.4 3.6 4 times 100 96.5 3.5 5 times 100 96.4 3.6 6 times 100 96.4 3.6 Episode 7 100 96.8 3.2 Episode 8 100 96.8 3.2 Episode 9 100 96.7 3.3 10 times 100 96.5 3.4

In addition, after the reaction was completed in the same manner as in Example 2 to which the catalyst of Preparation Example 2 was applied, the experiment was repeated three times in the same manner by reusing the catalyst used in the reaction as it is. As a result of observing the color change of the produced BHET after each reaction was completed, it was found that it was discolored to a higher degree than the color of the raw material even after repeated use, and the orange pigment was removed even after repeated use.

Therefore, the catalyst according to the present invention can produce BHET in a high yield in the glycolysis depolymerization reaction of PET, has excellent durability, and is advantageous in recovering and reusing the catalyst, so that the yield can be maintained even if the catalyst is repeatedly reused. I was able to confirm. In addition, it was confirmed that even in the glycolysis depolymerization reaction of pigment-containing colored PET, BHET could be obtained in high yield simultaneously with the removal of the pigment.

The present invention is not limited by the above-described embodiments, and those skilled in the art that various substitutions, modifications, and changes are possible within the scope without departing from the technical spirit of the present invention will be clear to

Claims (11)

A catalyst for depolymerization of polyethylene terephthalate,
The catalyst is a catalyst for depolymerization of polyethylene terephthalate, characterized in that iron, which is a catalytically active component, is surrounded by a carbon body.
According to claim 1,
The catalyst for the depolymerization reaction of polyethylene terephthalate, characterized in that formed by carbonizing the iron-organic ligand skeleton.
According to claim 2,
The iron-organic ligand skeleton is a catalyst for depolymerization of polyethylene terephthalate, characterized in that the MOF with iron (Fe) as the central metal.
According to claim 1,
A catalyst for depolymerization of polyethylene terephthalate, characterized in that the depolymerization reaction of polyethylene terephthalate is a reaction between polyethylene terephthalate and glycol.
In the method for preparing a catalyst for depolymerization of polyethylene terephthalate,
A method for preparing a catalyst for depolymerization of polyethylene terephthalate, characterized in that iron (Fe), a catalytically active component, is surrounded by a material containing a carbonaceous material, including the step of carbonizing an iron-organic ligand framework in an inert atmosphere. .
According to claim 5,
The method of preparing a catalyst for depolymerization of polyethylene terephthalate, characterized in that the iron-organic ligand skeleton is an MOF with iron (Fe) as a central metal.
According to claim 5,
The method for preparing a catalyst for depolymerization of polyethylene terephthalate is depolymerization of polyethylene terephthalate, characterized in that carbonization is carried out by further including a carbon precursor in the iron-organic ligand skeleton prior to carbonization of the iron-organic ligand skeleton. A method for preparing a catalyst for a reaction.
According to claim 7,
The carbon precursor is furfuryl alcohol, divinylbenzene, urea, glucose, sucrose ethylene glycol, glycerol, xylitol and melamine A method for preparing a catalyst for depolymerization of polyethylene terephthalate, characterized in that it is at least one selected from the group consisting of (melamine).
According to claim 5,
The carbonization is a method for producing a catalyst for depolymerization of polyethylene terephthalate, characterized in that carried out at 600 ℃ ~ 1200 ℃.
A method for producing BHET, characterized in that BHET is produced by reacting polyethylene terephthalate with glycol in the presence of the catalyst for depolymerization of polyethylene terephthalate according to any one of claims 1 to 4.
According to claim 10,
The glycol is a method for producing BHET, characterized in that 100 to 3000 parts by weight based on 100 parts by weight of polyethylene terephthalate.

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