KR20210062142A - A method for manufacturing syngas from bis(2-hydroxyethyl)terephthalate using plasma process - Google Patents

Abstract

The present invention relates to a method for manufacturing synthesis gas from bis(2-hydroxyethyl)terephthalate using a plasma process and, more particularly, to a synthesis gas production method comprising: a step of introducing bis(2-hydroxyethyl) terephthalate into a plasma reactor; and a plasma gasification step of generating syngas by a plasma gasification reaction. One aspect of the present invention is to provide the method for obtaining synthesis gas by processing a series of processes for reacting BHET with plasma.

Description

A method for manufacturing syngas from bis(2-hydroxyethyl) terephthalate using plasma process}

The present invention relates to a method for producing syngas from bis(2-hydroxyethyl) terephthalate using a plasma process, and in particular, chemical recycling (pyrolysis, hydrosis, glycolysis, etc.) of a polyethylene terephthalate (PET) polymer film. The present invention relates to a technology for producing syngas such as _{H 2} and CO with high added value by processing a series of processes of reacting bis(2-hydroxyethyl) tetrephthalate (BHET) monomers generated through plasma with plasma.

PET is a polyester produced using terephthalic acid (TPA) or dimethylterephthalate (DMT) as a raw material. It is known to have. Since the mid-1970s, PET has been used to make beverage containers in the United States, Canada, and Western Europe, and recently, it has been used in various industries and life fields such as audio and video tapes and textile manufacturing, and demand and consumption are expected to continue to increase. do.

On the other hand, in addition to the excellent characteristics of PET, it has been raised as a problem that causes serious environmental pollution problems due to the characteristics that PET does not decompose in nature. As a method of recycling such waste PET, physical and chemical methods are known. The former physical recycling method is used in the form of PET clips or flakes, and the latter chemical method is used to decompose polymerized waste PET into monomers or oligomers, which are raw materials. And from an industrial aspect, it is more preferable to use a chemical method.

Chemical methods developed so far include methanol degradation, glycolysis, hydrolysis, aminolysis, and ammonolysis. Among the listed methods, methanol decomposition, the corresponding process, and hydrolysis are widely used. However, among the above decomposition methods, methanol decomposition and hydrolysis are extremely limited in the quality and quantity of products produced when decomposing PET, and the decomposition reaction time is long, and only one of TPA or DMT, which is a raw material for PET synthesis, can be produced. Do. Accordingly, it has a disadvantage that it is bound to be limitedly used in each PET production process using these as raw materials.

In order to solve the above-described problems of the prior art, Korean Patent No. 10-1170506 discloses a process capable of producing BHET relatively easily compared to methanol decomposition and hydrolysis.

_{Therefore, if a technology capable of producing syngas such as H 2} and CO with high added value from BHET generated in the waste plastic recycling process is developed, it is expected that it can be widely applied to research institutes and companies that research waste plastic recycling. do.

Accordingly, one aspect of the present invention is to provide a method of obtaining a synthesis gas by processing a series of processes of reacting BHET with plasma.

According to one aspect of the present invention, a method for producing syngas, including the step of introducing bis(2-hydroxyethyl) terephthalate into a plasma reactor and a plasma gasification step of generating syngas by a plasma gasification reaction. Is provided.

The present invention can provide a process solution integrated with the conventional waste plastic (polymer) recycling process by processing a series of processes of reacting the BHET monomer produced by this with plasma, not recycling of the conventional waste plastic (polymer). It is expected to be.

1 schematically shows an example of a plasma device used in an embodiment of the present invention.
2 is a graph showing the results of checking applied power and gas temperature according to the presence or absence of BHET.
3(a) shows an ICCD camera analysis image when BHET is not added, FIG. 3(b) is a case where BHET is input, and FIG. 3(c) shows an ICCD camera analysis image when BHET is input and an OH filter is applied.
4 shows the change in the concentration of the generated gas according to the plasma reaction time.
5 shows the entire OES spectrum when plasma reacts with BHET.
6 shows a gas temperature measurement location using a thermal imaging camera, (a) before reaction with BHET (b) shows an image during reaction with BHET.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. However, embodiments of the present invention may be modified into various other forms, and the scope of the present invention is not limited to the embodiments described below.

The present invention relates to a technology for obtaining a synthesis gas containing _{H 2} , CO and the like having high added value by processing a series of processes of reacting a BHET monomer with plasma.

In more detail, the synthesis gas production method of the present invention includes a step of introducing bis(2-hydroxyethyl) terephthalate (hereinafter'BHET') into a plasma reactor and a plasma gasification step of generating a synthesis gas by a plasma gasification reaction. To include.

For example, by applying a coaxial transmission line resonator (CTLR) device, a plasma for a reaction process can be generated by applying an AC voltage to an electrode of the device, and ions, electrons, and anions can be generated in the air. Using such a plasma reactor, it is possible to provide an integrated process of gasification of BHET monomers obtained through depolymerization rather than polymer materials.

Plasma that can be used in the present invention includes air as well as inert gas such as argon and helium, so that purchase of inert gas and incidental costs can be reduced. Preferably, air is used as the discharge gas.

Meanwhile, the BHET (bis(2-hydroxyethyl) terephthalate) applied to the present invention may be obtained from waste PET. For example, after pulverizing the waste PET, ethylene glycol may be added and reacted for 20 to 45 minutes in a supercritical state of high temperature and high pressure. At this time, PET may generally be a polymer synthesized from TPA, DMT, and ethylene glycol, but is not limited thereto, but various waste PETs such as waste PET molded products, waste PET fibers, waste PET films, waste PET beverage containers, etc. It includes, and is preferably pulverized to an effective diameter of 10 mm or less using dry ice. The reaction is carried out in an autoclave, and the final reaction product, BHET, is dispersed by cooling the reactant reacted for 20 to 45 minutes under supercritical conditions in cold water, and then boiling water by heating and cooling again to solidify. Compounds can be obtained. Meanwhile, the supercritical temperature condition is preferably 719.7 K or more and 1300 K or less. When the temperature condition is 1300 K or more, damage to the reactor and mass production are difficult, and when the temperature is less than 719.7 K, the high yield and short reaction time expected in the supercritical condition cannot be expected. In addition, the supercritical pressure condition is preferably 7.7 Mpa or more and 15 Mpa or less. If the pressure condition is more than 15 Mpa, the damage of the reactor and the cost of manufacturing the reactor increase, making mass production difficult, and if it is less than 7.7 Mpa, the reaction time for raw materialization of waste PET is long and the yield decreases. Therefore, most preferably, waste PET is pulverized using dry ice, and then ethylene glycol is added, and at 30 under a temperature condition of 719.7 K or more and 1300 K or less, and a pressure condition of 7.7 Mpa or more and 15 Mpa or less. When reacted for 35 minutes, BHET can be obtained in a yield of 90% or more.

The plasma gasification step is performed at a low frequency, a radio frequency, and a microwave frequency, and may operate at, for example, a radio frequency of 875 MHz.

The present invention has the advantage that gasification is possible even at a temperature lower than that of a general thermal process because the physical (sputtering) and chemical (active radical reaction) properties of the plasma are used. More specifically, in the present invention, the plasma gasification step may be performed in a temperature range of 50 to 250°C under atmospheric pressure conditions, and preferably may be performed in a temperature range of 150 to 250°C under atmospheric pressure conditions. As a heat treatment process for treating existing waste plastics, the required temperature is about 400°C, and if the process is applied, the gasification process can be applied at a temperature lower than 100°C. However, if the temperature is less than 50°C in the plasma gasification step under atmospheric pressure, the plasma and BHET reaction may not sufficiently occur, and accordingly, the BHET may not be gasified. In addition, in the case of a temperature exceeding 250°C, the amount of gas generated by the reaction between plasma and BHET becomes indistinct compared to the energy used to increase the gas temperature of the plasma. As a result, the process can be applied even in a temperature range exceeding 250°C, but the process cost increases compared to the efficiency, which is not preferable in terms of process economy.

On the other hand, in the present invention, the plasma gasification step is preferably performed for 13 to 20 minutes, and the reaction time is more preferable in terms of process economy as the reaction and treatment time with BHET through plasma is shorter. For example, the plasma and BHET reaction and treatment time for the gasification process for obtaining the first syngas (Ex_CO) may be performed for 13 to 20 minutes. When the plasma gasification step is performed in less than 13 minutes, the generation of CO may be insufficient, and when the process treatment time exceeds 20 minutes, generation of CO is possible, but the yield of CO decreases during the process, and the process economy Not recommended. Not desirable for fair economy.

The synthesis gas obtained by the present invention includes hydrogen and carbon monoxide, and more specifically, CH ₄ , NO, NO ₂ , H ₂ and CO. For example, the hydrogen and carbon monoxide can be obtained in 3% by volume and 2% by volume, respectively, based on the total synthesis gas.

The plasma generating apparatus for the gasification process of the present invention may include a plasma generating unit and a power supply unit for supplying power, and at this time, the plasma generating unit may use any device capable of generating plasma.

Specifically, there are a low-frequency plasma generator of direct current or several KHz or less, a plasma generator that generates an AC arc discharge, a high-frequency plasma generator by a radio frequency magnetic field, a plasma generator by microwave, and the like. For example, it may be a pulsed plasma, a DC plasma, an AC plasma, or the like, and is preferably a plasma based on a radio frequency or a microwave frequency.

FIG. 1 schematically shows an example of a plasma device that can be used in the present invention, and referring to FIG. 1, a description of the power and gas supply stage is performed by a signal generator for applying frequency and power to the CTLR. ) And a power amplifier (2) exist, and a bi-directional coupler (Bi-directional coupler), a power sensor (4, 5), and a power meter ( Power meter, 6, 7) can be present.

The power used in the actual process (Microwave/Plasma) can be calculated by measuring the incident power and the reflected power using the above device and then calculating the difference between the two powers.

In addition, a mass flow controller (MFC) capable of quantitatively supplying air for generating air plasma to the CTLR may be used.

On the other hand, the standard of the reactor is not particularly limited, but for example, one having a standard of 120 mm in width, 50 mm in length, and 100 mm in height (excluding air holes and CTLR) may be used. At the top of the reactor, a CTLR that generates plasma using a microwave source can be fixed and fixed after mounting so that it can react with BHET. On the left side of the reactor, an air hole for collecting or measuring the gasified BHET by reacting with the plasma is arranged, and on the right side of the reactor, a device inlet can be designed to insert a conductive device to ignite the CTLR. It is desirable to design it to be located at a long distance from the device to minimize the impact.

It is preferable to design the lower end of the reactor to be able to close or open the device inlet in order to lower the pressure when the pressure is full. If the bottom part of the reactor is designed to place BHET, direct reaction with plasma may be possible.

Furthermore, the front surface of the reactor may be made of quartz to enable reaction analysis through a program through OES (Optical emission spectroscopy) measurement.

Hereinafter, the present invention will be described in more detail through specific examples. The following examples are only examples to aid understanding of the present invention, and the scope of the present invention is not limited thereto.

Example

One. plasma Gasification experiment

In order to produce a synthesis gas from bis(2-hydroxyethyl) terephthalate (hereinafter referred to as'BHET') by the synthesis gas production method of the present invention, a frequency of 875 MHz, an input power of 9 to 16 W, Plasma gasification was performed by reacting 1.5 g or 2 g of BHET using air as a discharge gas under gas flows of 1.5 and 2 slm.

1 schematically shows the apparatus used for this experiment and shows a schematic gasification process through the BHET depolymerization reaction extracted from waste PET.

The experimental process will be described in detail with reference to FIG. 1 as follows.

As shown in FIG. 1, a device for supplying power and gas to the CTLR to generate plasma, a reactor for BHET depolymerization reaction, and a CTLR, and a device for analyzing and collecting gas generated by the depolymerization reaction were provided.

At this time, the method of generating gas through the depolymerization reaction of BHET will be described, a method of generating plasma by fixing CTLR in the reactor designed above, and placing BHET in powder form on the bottom of the reactor to directly react to gasify it. to be.

Finally, the method of collecting and analyzing the generated gas is a structure that discharges the gas through the air hole on the left side of the reactor. The generated gas is extracted through a gas collector (manufactured by Gas collector 10, SANT), and a Tedlar bag (Tedlar bag) Bag) or polyester and aluminum sampling bag (manufactured by Top Trading ENG). After that, gas chromatography (GC, Agilent 7890A) equipment was equipped with a TCD column to perform analysis.

In addition, by measuring the concentration of gas generated in-situ through a portable gas meter (Vario plus, manufactured by MRU) and analyzing the result of OES measurement, the base data of the gas analysis result is supplemented.

2. BHET Input power and gas temperature check according to the presence or absence

In the plasma gasification experiment of 1. above, while changing the gas flow to 1.5 and 2 slm, the gas temperature change according to the applied power was confirmed. The gas temperature was measured based on the strongest brightness in the plasma plume generated from CTLR using a thermal imaging camera. 6 shows a gas temperature measurement location using a thermal imaging camera, (a) before reaction with BHET (b) shows an image during reaction with BHET.

As a result, as can be seen in FIG. 2, when BHET was introduced, the gas temperature was increased, and it was confirmed that the gasification reaction occurred even at less than 317°C, the boiling point of BHET by the plasma gasification process. In addition, the results of this experiment show the chemical/physical properties of the plasma process.

이상의 온도가 가해질 때 물질의 기화가 발생하지만 본 실험에서의 경우 플라즈마의 도 6에서 보는 바와 같이 이보다 낮은 온도(250℃ 이하) 에서 CO 등의 부가가치가 높은 기체가 추출되었다. In the case of general thermal process, evaporation point (BHET evaporation point: 317

When the above temperature is applied, vaporization of the material occurs, but in the case of this experiment, gas having a high added value such as CO was extracted at a lower temperature (250°C or less) as shown in FIG.

Therefore, this process, which can control the temperature of the plasma according to the difference in applied power (Thermal/Non-Thermal), is expected to control not only the conventional thermal process but also the chemical and physical (sputtering) and chemical (active radical reaction) processes. It is expected.

3. ICCD Camera analysis

In the plasma gasification experiment of 1. above, when the gas flow was 2 slm, the plasma discharge image was confirmed with an ICCD (Intensified Charge-Coupled Device) camera, which is a charge-coupled device (CCD) camera combined with an image amplifier.

The results are shown in Fig. 3, Fig. 3(a) is a case where BHET is not added, Fig. 3(b) is a case where BHET is injected, and Fig. 3(c) is a case where BHET is injected and an OH filter is applied It shows the image of. In the ICCD plasma discharge image during the in-situ BHET reaction, it was confirmed that OH radicals that were not observed in the pure plasma ICCD image without BHET were additionally generated.

This is presumed to be a characteristic characteristic of this plasma process reacting below the evaporation point from the results of the plasma gas temperature measurement experiment result of the CTLR according to the applied power in FIG. 2. As a result, it was confirmed that plasma reaction occurred when BHET was added. In particular, when the OH filter was applied, CH ₂ -OH (Hydroxymethyl) in the BHET structure was relatively easily cut off, and thus OH- was observed. When the OH filter was applied on the ICCD image as described above, OH radicals were newly observed in the plasma.

4. plasma Confirm the change in the concentration of the generated gas according to the reaction time and OES analysis

In the plasma gasification experiment of 1. above, the change in the concentration of the generated gas according to the plasma reaction time was confirmed, and the results are shown in FIG. 4. As a result, it was confirmed that CO generation significantly increased from 13 minutes to 18 minutes, and the amount of CO gas with high added value increased from 100 ppm to 1400 ppm. On the other hand, the yield of CO gas collected after 13 minutes at a specific power (12 W) increases and the yield of CO gas decreases again after 18 minutes. When incomplete combustion starts due to lack of oxygen, CO gas rapidly increases, and CO generated after 13 minutes reacts with the surrounding gas again to stabilize, and it is assumed that the yield of CO gas decreases.

In addition, the entire OES spectrum when the plasma reacts with BHET is shown in FIG. 5, and as a result, the reactivity could be clearly confirmed. From the plasma point of view, when BHET and plasma directly react, CO radicals corresponding to 588.5 nm are released in time through atomic spectrum database lines data (NIST) on OES (Optical Emission Spectroscopy). It was confirmed that it increased accordingly. This active species (radical) is a radical that does not appear in the plasma that does not react with BHET, and is presumed to contribute to the increase in CO gas yield in FIG. 4. In other words, by cracking a specific CO bond of the BHET monomer, related CO active species were observed on the OES, which is expected to increase the yield of CO gas (FIG. 4).

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and variations are possible without departing from the technical spirit of the present invention described in the claims. It will be obvious to those of ordinary skill in the field.

1: Signal generator
2: Power amplifier
3: Bi-directional coupler
4, 5: Power sensor
6, 7: Power meter

Claims (7)

Introducing bis(2-hydroxyethyl)terephthalate into a plasma reactor; And
A method for producing syngas, comprising a plasma gasification step of generating syngas by a plasma gasification reaction.
The method of claim 1, wherein the bis(2-hydroxyethyl) terephthalate is obtained from waste polyethylene terephthalate (PET).
The method of claim 1, wherein the discharge gas in the plasma gasification step is selected from inert gas and air.
The method of claim 1, wherein the plasma gasification step is performed in a radio frequency plasma, a microwave frequency plasma, a pulsed plasma, a DC plasma, or an AC plasma.
The method of claim 1, wherein the plasma gasification step is performed under atmospheric pressure and a temperature range of 50 to 250°C.
The method of claim 1, wherein the plasma gasification step is performed for 13 to 20 minutes.
The method of claim 1, wherein the synthesis gas comprises hydrogen and carbon monoxide.

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