KR102278269B1 - BIOMASS-DERIVED SiO₂ CATALYST FOR TPA HYDROLYSIS OF PET, MANUFACTURING THEREOF, AND TPA HYDROLYSIS OF PET USING THE CATALIST - Google Patents

Abstract

According to a preferred embodiment of the present invention, the SiO ₂ catalyst is characterized in that it is extracted from biomass. Using the biomass-derived SiO ₂ catalyst according to the present invention, a method for producing the same, and a method for decomposing PET using the same, it is possible to produce high-purity terephthalic acid (TPA) in a time faster than the hydrolysis rate of PET under conventional neutral conditions In addition, the prepared terephthalic acid can be usefully used as a raw material for polyester fibers.

Description

Biomass-derived SiO₂ catalyst for TPA decomposition of PET, manufacturing method thereof, and TPA decomposition method of PET using same

The present invention relates to a biomass-derived SiO ₂ catalyst for TPA decomposition of PET, a manufacturing method thereof, and a TPA decomposition method of PET using the same. Specifically, a SiO ₂ catalyst for TPA decomposition of PET derived from biomass and microwave It relates to a method of hydrolyzing polyethylene terephthalate into terephthalic acid using

Rice, the main grain in Asia including Korea, is about 4.68 million tons (cultivated area about 920,000 ha) as of 2009 in Korea, and about 5 million tons of rice are produced every year. Rice husks are agricultural wastes generated during the threshing process of rice, and generally account for about 20% of rice by weight. In Korea alone, about 90 to 1 million tons of rice husks are generated each year as a by-product of the milling process.

However, despite research on various uses of rice husk since the mid-1900s, in Korea, most of the rice hull is used as a rug for livestock facilities such as cattle and pigs, and as an interior insulation material.

Rice husks are largely divided into organic and inorganic components, with about 80% organic and 20% inorganic. Organic matter is composed of vegetable polymers such as cellulose, hemicellulose and lignin, and inorganic matter is mostly composed of silica. The silica component contained in the rice husk is protected by a polymer with high physical and chemical resistance such as lignin.

Therefore, in order to increase the utility of such rice hulls, research on using rice husk as a raw material, technology development for manufacturing wood materials or synthetic wood using rice husk as a material, and research on separating/extracting silica present in rice hulls Various R&D activities have been carried out continuously.

On the other hand, PET (Polyethylene Terephthalate), which can be obtained by polycondensation of terephthalic acid and ethylene glycol, has good rigidity, electrical properties, weather resistance, and heat resistance. Therefore, it has good resistance to oil.

Accordingly, it is used as household goods, toys, electrical insulators, home appliance cases, packaging materials, etc. In particular, because it is light and has no taste and smell, it accounts for most of plastic beverage bottles.

However, despite these advantages, the waste PET resin is decomposed very slowly due to its high resistance to atmospheric and biological materials, causing environmental problems.

Chemical recycling methods, such as glycol lysis, hydrolysis, methanolysis, etc., are disclosed as a method of recycling such waste PET resin.

The glycolysis method is a method widely used commercially as a method of depolymerizing PET using glycol such as ethylene glycol. However, it has the advantage of low operating cost and little pollution of waste PET as a raw material, but has a disadvantage in that it is difficult to purify due to the high molecular weight of the depolymerized product.

Hydrolysis is a method for decomposing PET by water, alkali, etc., and is widely used for the production of terephthalic acid, but has a disadvantage in that it requires a lot of manufacturing cost.

Metanolysis is the most widely used depolymerization method using methanol. However, while there is an advantage that is not related to the contamination state of the waste PET, there is a disadvantage that the manufacturing cost is high because it has to be operated at a high temperature and pressure.

Among the above methods, since terephthalic acid can be used again as a raw material for polyester fibers, many studies have been conducted on a hydrolysis method for separating terephthalic acid and ethylene glycol from waste PET resin.

Korean Patent Registration No. 10-0429385 proposes a method for producing high-purity terephthalic acid by salting out and refining terephthalic acid produced after hydrolysis of PET with acid. However, the method has a disadvantage in that it requires a high-temperature heat treatment process in the purification process.

In addition, Korean Patent Registration No. 10-0224466 proposes a method of hydrolyzing PET with alkali metal hydroxide/earth metal to form alkali metal/earth metal salt of terephthalic acid and dissolving it in water to separate it, but the alkalinity is too strong. Therefore, there is a problem in that the reaction is radical and thus a lot of side reactants are generated, and a crystal growth step is additionally required in the final separation step of terephthalic acid.

In order to solve this problem, Korean Patent Laid-Open No. 10-2005-0049566 and U.S. Patent No. 4,542,239 propose a method of reacting PET with ammonium hydroxide, but the reaction environment is high temperature and high pressure, and the final product, terephthalic acid, is There is no explicit mention of purity.

KR 10-0429385 B1 (2004.04.29. Announcement) KR 10-0224466 B1 (199.10.15. Announcement) KR 10-2005-0049566 A (published on May 27, 2005) USP 4,542,239 (1985.09.17. Announcement)

_{An object of the present invention is to prepare a SiO 2} catalyst for TPA decomposition of PET by using rice hull, and by using it to react polyethylene terephthalate in a microwave reactor, a method for easily producing solid terephthalic acid is to provide

Another object of the present invention is to provide a method for producing terephthalic acid of high purity by lowering the impurity content in terephthalic acid when hydrolyzing polyethylene terephthalate under neutral conditions.

The problem to be solved by the present invention is not limited to the problem(s) mentioned above, and another problem(s) not mentioned will be clearly understood by those skilled in the art from the following description.

According to a preferred embodiment of the present invention, the SiO ₂ catalyst for TPA decomposition of PET is characterized in that it is extracted from biomass.

In one embodiment, the biomass is preferably rice husk.

In one embodiment, the _{surface of the biomass-derived SiO 2} catalyst for TPA decomposition of PET is preferably modified by a thiol functional group (-SH).

In one embodiment, the _{specific surface area of the SiO 2} catalyst is 151.92 ~ 281.02 m ² /g, and the pore size is preferably 0.57 ~ 0.66 nm.

According to another preferred embodiment of the present invention, a _{method for producing a biomass-derived SiO 2} catalyst for TPA decomposition of PET includes the steps of: (A) pulverizing rice hulls and then acid-treating; and (B) heat-treating the acid-treated rice hull of step (A).

In another embodiment, the acid treatment in step (a) is performed using an acidic solution containing one selected from the group consisting of sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, and mixtures thereof, at 40 to 150 ° C. It is preferably carried out for 10 minutes to 3 hours.

In another embodiment, after the acid treatment of step (a), it is preferable to further include the step of filtering and washing the acid-treated rice husk.

In another embodiment, the heat treatment in step (b) is preferably performed for 2-3 hours by increasing the temperature of 600 ~ 700 ℃ by 3.5 ℃ per minute at room temperature.

In another embodiment, the step (b) and then further comprising the step of modifying the surface of the SiO ₂ catalyst, the step of modifying the surface of the SiO ₂ catalyst, the SiO ₂ catalyst and mercaptopropyl trimethoxysilane (Mercaptopropyl trimethoxysilane) was added to a toluene (Tolyene) solvent to prepare a mixture; washing the mixture; and drying the washed mixture.

_{TPA decomposition method of PET using biomass-derived SiO 2} catalyst according to another preferred embodiment of the present invention, polyethylene terephthalate (Polyethylene terephthalate), biomass-derived SiO ₂ catalyst, and water are mixed and irradiated with microwaves to It is characterized in that polyethylene terephthalate is hydrolyzed to terephthalic acid.

In another embodiment, the method of hydrolyzing polyethylene terephthalate into terephthalic acid comprises (a) _{reacting polyethylene terephthalate, biomass-derived SiO 2} catalyst and water in a microwave reactor to prepare a mixture in which terephthalic acid is precipitated step; (b) dissolving terephthalic acid by mixing sodium hydroxide with the mixture; (c) filtering the mixture in which the terephthalic acid is dissolved to remove the residue and the catalyst; (d) forming and obtaining a precipitate by adding an acidic solution to the mixture from which the residue and the catalyst are removed; and (e) drying the obtained precipitate.

In another embodiment, the acidic solution is preferably one selected from the group consisting of sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, and mixtures thereof.

Using the biomass-derived SiO ₂ catalyst for TPA decomposition of PET, its preparation method, and the PET TPA decomposition method using the same according to the present invention, high-purity terephthalic acid (TPA) in a time faster than the PET hydrolysis rate under conventional neutral conditions ) can be produced, and the prepared terephthalic acid can be used again as a raw material for polyester fibers.

1 shows a method for preparing a _{biomass-derived SiO 2} catalyst for TPA decomposition of PET.
2 shows a method for hydrolyzing polyethylene terephthalate to terephthalic acid.
3(a) to 3(f) show SEM images of Examples 1 and 2.
4 is an analysis of the X-ray diffraction pattern of _{the SiO 2} catalyst prepared according to Example 1.
5(a) to 5(f) show the results of measuring XPS _{of the SiO 2 catalysts prepared according to Examples 1 and 2;}
Figures 6 (a) and 6 (b) shows the XPS quantitative analysis of _{the SiO 2 catalyst prepared according to Examples 1 and 2.}
7(a) and 7(b) show N ₂ adsorption/desorption isotherms of _{SiO 2 catalysts prepared according to Examples 1 and 2;}
8 shows the NH ₃ -TPD measurement results _{of the SiO 2} catalysts prepared according to Examples 1 and 2;
9(a) and 9(b) are graphs showing the yield of TPA according to time and temperature.
10(a) and 10(b) are NMR analysis of terephthalic acid (TPA).
11(a) and 11(b) are graphs showing reaction rate constant values with respect to concentration and time.

Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the accompanying drawings.

Advantages and features of the present invention, and a method of achieving the same, 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 by the embodiments disclosed below, but may be implemented in various different forms, and only the present embodiments allow the disclosure of the present invention to be complete, and it is common in the art to which the present invention pertains. It is provided to fully inform those with the knowledge of the scope of the invention. Moreover, the invention is only defined by the scope of the claims.

Furthermore, in the description of the present invention, when it is determined that related known techniques may obscure the gist of the present invention, detailed description thereof will be omitted.

Prior to the description of the present invention, the biomass described in the present invention may be rice husk.

_{SiO 2} nanoparticles for TPA decomposition of PET prepared from the biomass may be a _{SiO 2 catalyst.}

In addition, the surface-modified SiO ₂ catalyst by a thiol functional group is expressed as a Thiol-SiO _{2 catalyst.}

_{An object of the present invention is to prepare a SiO 2} catalyst for decomposing TPA of PET using rice husk, and by using it to react polyethylene terephthalate in a microwave reactor to provide a method for easily decomposing solid terephthalic acid is to do

Another object of the present invention is to provide a method for producing terephthalic acid of high purity by lowering the impurity content in terephthalic acid when hydrolyzing polyethylene terephthalate under neutral conditions.

_{The present invention provides a SiO 2} catalyst for TPA decomposition of PET extracted from biomass and a method for producing the same, and uses the _{SiO 2} catalyst derived from biomass for TPA decomposition of PET to hydrolyze polyethylene terephthalate. provide a way

Biomass according to an embodiment of the present invention may be rice husk.

_{The SiO 2} catalyst for TPA decomposition of PET according to an embodiment of the present invention is extracted from biomass, and the SiO ₂ catalyst may have a surface modified by a thiol functional group (-SH).

The specific surface area of the SiO ₂ catalyst may be 151.92 ~ 281.02 m ² /g, and the pore size may be 0.57 ~ 0.66 nm.

_{Hereinafter, a method for producing a biomass-derived SiO 2} catalyst for TPA decomposition of PET according to an embodiment of the present invention will be described with reference to FIG. 1 .

1 shows a method for preparing a _{biomass-derived SiO 2} catalyst for TPA decomposition of PET.

_{A method for producing a biomass-derived SiO 2} catalyst for TPA decomposition of PET according to an embodiment of the present invention comprises the steps of (A) pulverizing rice hulls and then acid-treating (S10); And (B) step (S20) of heat-treating the acid-treated rice hull of the (A) step (S10); is provided including.

The (a) step (S10) is a step of pulverizing the rice hulls and acid treatment.

The reason for pulverizing the rice hull to a certain size is to increase the efficiency of the acid treatment process after pulverization and to increase the purity of _{SiO 2 finally produced.}

The method of pulverizing the rice hull is not limited, and may be specifically milled.

The milling may be performed using a commonly used milling machine, such as a knee-type milling machine, a bed-type milling machine, a universal milling machine, and an upright milling machine.

The grain size of the milled rice hull may be 50 ~ 500㎛.

The acid treatment of (A) step (S10) is to remove impurities contained in the rice husk, and may be an acidic solution of 7 to 15%, specifically, a 10% acidic solution.

The acidic solution may be one selected from the group consisting of sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, and mixtures thereof, specifically hydrochloric acid.

The acid treatment in step (a) of step (A) (S10) is performed using an acidic solution containing one selected from the group consisting of sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, and mixtures thereof, from 40 to It may be carried out at 150 ° C. for 10 minutes to 3 hours, specifically, it may be carried out at 50 to 100 ° C. for 20 to 2 hours using hydrochloric acid, and more specifically, it is carried out at 60 ° C. for 30 minutes using hydrochloric acid. can be

The acid treatment of the pulverized rice hulls may be performed one or more times, and specifically, it may be performed 1 to 10 times, and may be performed differently depending on the type and concentration of the acidic solution.

The acid treatment in step (A) (S10) may be performed with the pulverized rice hull and the acid solution in a solid-liquid ratio (g:ml) of 1:5 to 15, specifically, to be performed at a solid-liquid ratio of 1:10. can

After the acid treatment of the (A) step (S10), the method may further include filtering and washing the acid-treated rice husk.

The filtration is not limited as long as it is a method capable of obtaining _{SiO 2 nanoparticles.}

The washing may be performed 1 to 4 times with distilled water, toluene, acetone, or the like.

The (b) step (S20) is a step of heat-treating the acid-treated rice husk of the (a) step (S10).

The heat treatment of step (B) (S20) may be performed at a temperature of 600 ~ 700 °C for 2-3 hours by increasing the acid-treated rice husk by 3.5 °C per minute at room temperature.

When the heat treatment is performed under the conditions described above _{, a SiO 2} ^{catalyst having a high specific surface area (151.92 ~ 281.02 m 2} /g) and large pores (0.57 ~ 0.66 nm) can be obtained.

Step of step (b) (S10) and then further comprising the step of modifying the surface of the SiO ₂ catalyst, and modify the surface of the SiO ₂ catalyst, the SiO ₂ catalyst and mercaptopropyl trimethoxysilane (Mercaptopropyl trimethoxysilane ) to prepare a mixture by adding the toluene (Tolyene) solvent; washing the mixture; and drying the washed mixture.

The washing of the mixture may be performed 1 to 4 times with distilled water, toluene, acetone, or the like.

Drying the washed mixture may be vacuum dried at 50 ~ 70 ℃ for 12 ~ 26 hours.

2 shows a method for hydrolyzing polyethylene terephthalate to terephthalic acid.

_{TPA decomposition method of PET using a biomass-derived SiO 2} catalyst according to another embodiment of the present invention, polyethylene terephthalate (Polyethylene terephthalate), a biomass-derived SiO ₂ catalyst, and water are mixed and irradiated with microwave to the polyethylene terephthalate It is characterized in that the phthalate is hydrolyzed to terephthalic acid.

Specifically, the method of hydrolyzing polyethylene terephthalate to terephthalic acid using a biomass-derived SiO ₂ catalyst is (a) a mixture in which terephthalic acid is precipitated by reacting _{polyethylene terephthalate, a biomass-derived SiO 2 catalyst, and water in a microwave reactor.} manufacturing (S100); (b) dissolving terephthalic acid by mixing sodium hydroxide with the mixture (S200); (c) filtering the mixture in which the terephthalic acid is dissolved to remove the residue and the catalyst (S300); (d) forming and obtaining a precipitate by adding an acidic solution to the mixture from which the residue and catalyst are removed (S400); And (e) drying the obtained precipitate (S500); is provided including.

Scheme 1 below shows a process in which polyethylene terephthalate is hydrolyzed to terephthalic acid.

[Scheme 1]

The step (a) (S100) is a step of hydrolyzing polyethylene terephthalate into terephthalic acid using a _{SiO 2 catalyst for TPA decomposition of PET derived from biomass.}

The hydrolysis may be performed in a microwave reactor.

The microwave reactor (Anton Paar, Monowave 400, UK) may be equipped with temperature and pressure sensors.

Since the description of the microwave reactor is outside the scope of the present invention, a description thereof will be omitted.

The SiO _{2 catalyst may be a SiO 2} catalyst derived from biomass, and the biomass may be rice husk.

_{In addition, the SiO 2} catalyst for TPA decomposition of PET derived from biomass may have a surface modified by a thiol functional group.

Since the SiO ₂ catalyst has been described above, a description thereof will be omitted.

Since it is obvious that water is required to hydrolyze the polyethylene terephthalate, a description thereof will be omitted.

Referring to Scheme 1, when the polyethylene terephthalate is hydrolyzed, a mixture in which terephthalic acid is precipitated is prepared.

The mixture may be terephthalic acid, ethylene glycol, polyethylene terephthalate and a catalyst.

The (b) step (S200) is a step of dissolving terephthalic acid by mixing sodium hydroxide with the mixture.

By dissolving terephthalic acid in step (S200) of (b), impurities may be removed in the next step.

Here, impurities are unreacted polyethylene terephthalate and catalyst.

The step (c) (S300) is a step of removing the residue and the catalyst by filtering the mixture in which the terephthalic acid is dissolved.

The residue is undecomposed polyethylene terephthalate.

The (c) step (S300) is not limited as long as it is a method capable of removing undecomposed polyethylene terephthalate and catalyst.

In step (d) (S400), an acidic solution is added to the mixture from which the residue and catalyst are removed to form and obtain a precipitate.

The acidic solution may be one selected from the group consisting of sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, and mixtures thereof, preferably hydrochloric acid.

The (e) step (S500) is a step of drying the obtained precipitate.

The method of drying the obtained precipitate is not limited.

Hereinafter, the present invention will be described in more detail by way of Examples and Experimental Examples. However, the following examples and experimental examples are only for illustrating the present invention, and the scope of the present invention is not limited thereto.

Example 1: Preparation of _{biomass-derived SiO 2} catalyst for TPA decomposition of PET

First, using a grinder, the grain size of the rice hull was prepared by grinding it to 150 μm.

10 g of pulverized rice husk was immersed in 100 ml of hydrochloric acid (10 % HCl) aqueous solution for 15 hours.

Next, after removing the aqueous hydrochloric acid solution using a filter, the rice husk was washed twice with distilled water.

Finally, the washed rice hulls were heated at a rate of 3.5° C. per minute at room temperature and annealed at a temperature of 650° C. for 3 hours to prepare a _{biomass-derived SiO 2 catalyst for decomposing TPA of PET.}

Example 2: Preparation of _{SiO 2} catalyst for TPA decomposition of surface-modified PET

_{First, 0.5 g of a biomass-derived SiO 2} catalyst for TPA decomposition of PET prepared according to Example 1 and 0.5 ml of mercaptopropyl trimethoxysilane were mixed in 200 ml of toluene and then for 24 hours It was refluxed and washed with toluene and acetone.

_{Finally, the surface-modified SiO 2} (Thiol-SiO ₂ ) catalyst was prepared by drying in a vacuum oven at 60° C. for 24 hours.

Experimental Example 1: Hydrolysis of non-catalyst PET

First, 0.1 g of polyethylene terephthalate and 12 ml of deionized water were placed in a microwave reactor (Anton Paar, Monowave 400, UK) to prepare a mixture in which terephthalic acid was precipitated.

After the reaction, 1 M sodium hydroxide was added to the mixture in which terephthalic acid was precipitated to dissolve the precipitated terephthalic acid (TPA) in the form of di-2-methyl terephthalic acid (NaTPA), and then filtered to obtain unreacted polyethylene terephthalate. removed.

Next, an excess of hydrochloric acid was added to precipitate TPA, followed by filtration to separate TPA.

Finally, dry TPA was obtained in an oven at 60°C.

Experimental Example 2: Hydrolysis of PET using _{SiO 2} catalyst derived from biomass for TPA decomposition of PET

_{First, 0.1 g of the SiO 2} catalyst prepared according to Example 1, 0.1 g of polyethylene teretalate, and 12 ml of deionized water were placed in a microwave reactor (Anton Paar, Monowave 400, UK) to prepare a mixture in which terephthalic acid was precipitated.

After the reaction, 1 M sodium hydroxide was added to the mixture in which terephthalic acid was precipitated to dissolve the precipitated terephthalic acid (TPA) in the form of di-2-methyl terephthalic acid (NaTPA), and filtered to obtain unreacted polyethylene terephthalate and The SiO ₂ catalyst was removed.

Next, an excess of hydrochloric acid was added to precipitate TPA, followed by filtration to separate TPA.

Finally, dry TPA was obtained in an oven at 60°C.

Experimental Example 3: Hydrolysis of PET using _{SiO 2} catalyst for TPA decomposition of surface-modified PET

First, 0.1 g of the surface-modified SiO ₂ catalyst prepared according to Example 2, 0.1 g of polyethylene teretalate, and 12 ml of deionized water were placed in a microwave reactor (Anton Paar, Monowave 400, UK) to prepare a mixture in which terephthalic acid was precipitated. .

After the reaction, 1 M sodium hydroxide was added to the mixture in which terephthalic acid was precipitated to dissolve the precipitated terephthalic acid (TPA) in the form of di-2-methyl terephthalic acid (NaTPA), and filtered to obtain unreacted polyethylene terephthalate and The surface-modified SiO ₂ catalyst was removed.

Next, an excess of hydrochloric acid was added to precipitate TPA, followed by filtration to separate TPA.

Finally, dry TPA was obtained in an oven at 60°C.

1. SiO ₂ Catalyst characterization

3(a) to 3(f) show SEM images of Examples 1 and 2.

3(a) to 3(c), the SiO _{2 catalyst prepared according to Example 1 is composed of small SiO 2} particles having a size of about 50 nm, and a rod-shaped form having a fine interconnection structure. It can be confirmed that

In addition, referring to FIGS. 3(d) to 3(f), _{it can be seen that the surface-modified SiO 2} catalyst prepared according to Example 2 continues to maintain a fine shape even after the surface is modified.

As a result, it can be confirmed that _{these nanostructures are intrinsic to the SiO 2 catalyst.}

2. SiO ₂ X-ray diffraction analysis of catalysts

4 is an analysis of the X-ray diffraction pattern of _{the SiO 2} catalyst prepared according to Example 1.

Referring to FIG. 4 , the 2θ value appeared in the form of a wide protrusion at 20°, which is consistent with the X-ray diffraction pattern of amorphous silica.

3. SiO ₂ Analysis by X-ray photoelectron spectroscopy (XPS) of catalysts

5(a) to 5(f) show the results of measuring XPS _{of the SiO 2 catalysts prepared according to Examples 1 and 2;}

5(a) to 5(c), the SiO ₂ catalyst prepared according to Example 1 in the O 1s spectrum exhibited a single peak at 532.8 eV, which is oxygen (O) in the Si—O—Si bonding environment. ) corresponds to In addition, in the Si 2p spectrum, the SiO ₂ catalyst prepared according to Example 1 exhibited a single peak at 103.5 eV, which corresponds to silicon (Si) in a Si—O bonding environment. In addition, in the S 2p spectrum, in the SiO ₂ catalyst prepared according to Example 1, a peak corresponding to sulfur was not found.

5(d) to 5(f), the SiO ₂ catalyst prepared according to Example 2 in the O 1s spectrum exhibited a single peak at 532.9 eV. This is a result confirming that the Si-O-Si bond is not changed even after the surface of the catalyst is modified with a thiol functional group.

However, in the Si 2p spectrum, the SiO ₂ catalyst prepared according to Example 2 was deconvolved with one peak representing the Si-O bond (103.8 ev) and another peak representing the Si-S bond (102.4 eV) ( deconvolution), which means that the surface of the catalyst has been modified with a thiol functional group.

In addition, in the S 2p spectrum, the SiO ₂ catalyst prepared according to Example 2 had peaks corresponding to S 2p1/2 and 2p3/2 at 164.6 eV and 163.5 eV, respectively, which indicates that the surface of the catalyst is modified due to the thiol functional group. It can be confirmed that it appears as

Figures 6 (a) and 6 (b) shows the XPS quantitative analysis of _{the SiO 2 catalyst prepared according to Examples 1 and 2.}

6(a) and 6(b), _{the silicon atomic ratio of the SiO 2} catalyst prepared according to Example 1 is 31.24%, and the oxygen atomic ratio is 64.01%, which is consistent _{with the conventional SiO 2 configuration. It can be seen that the silicon atomic ratio of the SiO 2} catalyst prepared according to Example 2 is 26.26%, the oxygen atomic ratio is 50.65%, and the sulfur atomic ratio is 2.78%.

_{The atomic ratio of the SiO 2} catalyst prepared according to Example 2 is different from that of Example 1 _{because the surface of the SiO 2} catalyst prepared according to Example 2 was modified with a thiol functional group.

As a result of the XPS analysis, it can be seen that the surface modification process _{of the SiO 2 catalyst prepared according to Example 2 was well performed, and even though the surface of the SiO 2} catalyst prepared according to Example 1 was modified, the initial structure was not affected.

4. SiO ₂ Catalyst N ₂ Adsorption/desorption analysis and NH ₃ -TPD analysis

Figure 7 (a) and 7 (b) is in the first embodiment and will illustrating the N ₂ adsorption / desorption isotherms of a SiO ₂ catalyst prepared in accordance with 2, 8 is for example 1 and the SiO ₂ catalyst prepared according to the two NH ₃ -TPD measurement results are shown.

7(a) and 7(b), both SiO ₂ catalysts prepared according to Examples 1 and 2 were mesoporous through multilayer adsorption followed by capillary condensation. solids), exhibited IV type isotherms forming hysteresis loops in the range of 0.4 to 1.0 relative pressure (P/PO).

The specific surface area of the _{SiO 2} catalyst was calculated by the Brunauer-Emmett-Teller (BET) theory (SBET).

The specific surface areas of _{the SiO 2} catalysts prepared according to Examples 1 and 2 were calculated to be ^{281.02 m 2} /g and 151.92 m ^{2 /g.}

In addition, the pore size of the _{SiO 2} catalyst was calculated by the Hgoorvath-Kawazoe (HK) method.

_{The pore sizes of the SiO 2} catalysts prepared according to Examples 1 and 2 were calculated to be 0.57 nm and 0.66 nm, respectively.

Through the two results, _{it can be confirmed that the SiO 2} catalyst hardly changes the surface area and pore size during the thiol reforming process.

Referring to FIG. 8 , in the SiO _{2 catalyst prepared according to Example 1, an NH 3} adsorption peak was confirmed in the low temperature region (LT) of 161.6° C., and the calculated acidic site concentration was 0.00838 mmol/g.

In addition, the SiO _{2 catalyst prepared according to Example 2 also showed an NH 3} adsorption peak in the low-temperature region (LT) of 161.6° C., and the calculated acidic site concentration was 0.00838 mmol/g.

_{However, in the SiO 2} catalyst prepared according to Example 2, _{another NH 3} adsorption peak was confirmed in the high temperature region (HT) of 369.4 ℃ because the thiol functional group on the surface acted as an acidic site, and the calculated acidic site concentration was 0.3. 9319 mmol/g.

5. Calculation of Yield of Terephthalic Acid (TPA) by Hydrolysis of Polyethylene Terephthalate (PET)

_{Polyethylene terephthalate was hydrolyzed using the SiO 2} catalyst prepared according to Examples 1 and 2 to calculate the yield of terephthalic acid.

9(a) and 9(b) are graphs showing the yield of TPA according to time and temperature.

The yield of TPA was calculated by Equation 1 below.

[Equation 1]

Figure 9 (a) is a comparison of the hydrolysis yield of terephthalic acid according to the reaction time at a temperature of 230 ℃.

Referring to FIG. 9(a), the hydrolysis of polyethylene terephthalate without using a catalyst did not react for the initial 5 minutes, and the yield reached 91.74% by reacting for 50 minutes.

_{However, in the hydrolysis of polyethylene terephthalate using the SiO 2} catalyst prepared according to Example 1, the hydrolysis was performed during the initial reaction time of 5 minutes, and the yield reached 92.4% by reacting for 40 minutes. _{In addition, the polyethylene terephthalate hydrolysis reaction using the SiO 2} catalyst prepared according to Example 2 was reacted for 30 minutes, and the yield reached 93.43%.

As a result, the hydrolysis time was reduced by 10 minutes when _{the SiO 2} catalyst according to Example 1 was used, compared to the polyethylene terephthalate hydrolysis reaction _{without using a catalyst, and 10 minutes when the SiO 2} catalyst according to Example 2 was used. It was confirmed that the minutes were further shortened.

_{This is because the acidity of the SiO 2} catalyst according to Example 2 _{is higher than that of the SiO 2} catalyst according to Example 1, and when the reaction starts, the hydrolysis rate is gradually increased due to the irregular chain separation of polyethylene terephthalate.

After the polyethylene terephthalate was subjected to random chain separation, the hydrolysis rate was rapidly increased, and the terephthalic acid hydrolysis yield reached 97.06%.

Referring to FIG. 9(b), it can be seen that hydrolysis of polyethylene terephthalate did not start at 170° C. or less, and the yield of terephthalic acid increased as the temperature increased when the temperature was increased. In addition, the yield reached 93.43% at a reaction temperature of 230 °C.

As a result, hydrolysis of polyethylene terephthalate without using a catalyst did not proceed at a temperature of 170 ° C. or lower, but when using the SiO ₂ catalyst prepared according to Examples 1 and 2, polyethylene terephthalate hydrolysis was performed at a temperature of 170 ° C. or lower. It can be confirmed that decomposition can proceed.

6. NMR analysis of terephthalic acid (TPA) following hydrolysis of polyethylene terephthalate (PET)

10(a) and 10(b) are NMR analysis of terephthalic acid (TPA).

Referring to FIG. 10( a ), _{terephthalic acid prepared by using the SiO 2} catalyst prepared according to Example 2 showed two peaks for a hydroxy proton and an aromatic single proton, and the chemical shift value was 13.31 ppm, respectively. It was found to be 8.03 ppm.

Referring to FIG. 10(b), _{the terephthalic acid prepared by using the SiO 2} catalyst prepared according to Example 2 showed three peaks in the 13C NMR spectrum, respectively, aromatic carbon quaternary aromatic carbon and carbonyl carbon. , the chemical shift values were 129.7 ppm, 134.8 ppm and 166.4 ppm, respectively.

The above results are confirmed to be consistent with the conventional terephthalic acid data.

7. Kinetic Analysis of Polyethylene Terephthalate (PET) Hydrolysis

The terephthalic acid hydrolysis of polyethylene terephthalate follows Equation 2 below.

[Equation 2]

v = k[A] ²

Here, v is the reaction rate, k is the reaction rate constant, and [A] is the concentration of polyethylene terephthalate.

According to the integrated rate law, the reaction rate constant (k) of the polyethylene terephthalate hydrolysis reaction is determined according to Equation 3 below.

[Equation 3]

1/[A] _t - 1/[A] _O = kt

Here, [A] _t represents the polyethylene terephthalate concentration at a specific reaction time, [A] _O represents the initial polyethylene terephthalate concentration, and t represents a specific reaction time.

11(a) and 11(b) are graphs showing reaction rate constant values with respect to concentration and time.

Referring to FIG. 11( a ), in the absence of a catalyst (no catalyst) and when the catalysts according to Examples 1 and 2 were used, the reaction rate constant (k) values were 0.56055, 0.76866, and 1.33406, respectively.

_{The hydrolysis using the SiO 2} catalyst prepared according to Example 1 exhibited 1.37 times improved hydrolysis properties than the non-catalytic hydrolysis, and the hydrolysis _{using the SiO 2} catalyst prepared according to Example 2 improved hydrolysis by 2.37 times. characteristics were shown.

_{The reason why the hydrolysis properties were improved using the SiO 2} catalyst prepared according to Example 2 was because the activation energy was lowered, which was calculated according to the following Equation 4 (Arrhenius equation) based on the reaction temperature control experiment.

[Equation 4]

k=Ae-Ea/RT

Here, k is the rate constant, A is the prior exponential factor, Ea is the activation energy, R is the gas constant, and T is the absolute temperature.

Equation 4 may be changed to Equation 5 below.

[Equation 5]

11(b), _{the activation energy of polyethylene terephthalate hydrolysis by the SiO 2} catalyst prepared according to Example 2 was calculated as 23.19 kJ/mol, and this value is the polyethylene terephthalate hydrolysis activation energy (56.8). kJ/mol) is reduced by more than half.

8. SiO prepared according to Example 2 ₂ Analysis of Mechanism of Catalyst Polyethylene Terephthalate Hydrolysis

Scheme 2 below shows a process in which polyethylene terephthalate is hydrolyzed to terephthalic acid.

[Scheme 2]

_{First, the thiol functional group on the surface of the SiO 2} catalyst according to Example 2 is easily deprotonated in aqueous conditions to form thiolate and hydronium (OH ₃ ⁺ ) ions.

Next, the generated hydronium ion donates a proton to the nucleophilic center of polyethylene terephthalate.

In polyethylene terephthalate, the oxygen atom of the ester group is positively charged, but the positive charge is more delocalized at the central carbon atom.

Next, the water molecule attacks the positively charged central carbon atom, and the oxygen atom of the ethyl group receives a hydrogen atom from another positively charged oxygen atom, becomes positively charged, and breaks the bond between carbon and oxygen to hydrolyze polyethylene terephthalate. The reaction produces terephthalic acid and ethylene glycol.

_{Without the SiO 2} catalyst prepared according to Example 2, the purity of terephthalic acid may be reduced by inducing incomplete decomposition of ester bonds in polyethylene terephthalate due to high activation energy, and the present invention solves this problem and provides high-purity terephthalate. acid can be produced.

Therefore, using the biomass-derived SiO ₂ catalyst according to the present invention, its manufacturing method, and the TPA decomposition method of PET using the same, it is possible to produce high-purity TPA in a shorter time than conventional PET neutral hydrolysis conditions, The terephthalic acid can be usefully used again as a raw material for polyester fibers.

_{So far, biomass-derived SiO 2} catalyst according to an embodiment of the present invention, a method for producing the same, and a specific example of a TPA decomposition method of PET using the same have been described, but within the limit not departing from the scope of the present invention, various It is obvious that various implementation modifications are possible.

Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined by the following claims as well as the claims and equivalents.

That is, it should be understood that the above-described embodiments are illustrative in all respects and not restrictive, and the scope of the present invention is indicated by the claims to be described later rather than the detailed description, and the meaning and scope of the claims; All changes or modifications derived from the concept of equivalents should be construed as being included in the scope of the present invention.

S10: Rice hull grinding and acid treatment step
S20: Rice husk heat treatment step
S100: mixture preparation step
S200: terephthalic acid dissolution step
S300: Residue and catalyst removal step
S400: step of obtaining a precipitate
S500: sediment drying step

Claims (12)

extracted from biomass,
Characterized in that the surface is modified by a thiol functional group (-SH),
_{Biomass-derived SiO 2} catalyst for TPA decomposition of PET.
The method of claim 1,
The biomass is characterized in that rice husk,
_{Biomass-derived SiO 2} catalyst for TPA decomposition of PET.
delete The method of claim 1,
The specific surface area of the SiO ₂ catalyst is 151.92 ~ 281.02 m ² /g, characterized in that the pore size is 0.57 ~ 0.66 nm,
_{Biomass-derived SiO 2} catalyst for TPA decomposition of PET.
(A) pulverizing the rice hulls and then acid-treating;
(B) heat-treating the acid-treated rice husk of step (a); and
After step (b), modifying the surface of the _{SiO 2 catalyst includes;}
The step of modifying the surface of the SiO _{2 catalyst,}
preparing a mixture by adding the SiO ₂ catalyst and mercaptopropyl trimethoxysilane to a toluene solvent;
washing the mixture; and
Drying the washed mixture; characterized in that it comprises,

Method for producing _{SiO 2} catalyst derived from biomass for TPA decomposition of PET.
6. The method of claim 5,
The acid treatment in step (a) is,
Using an acidic solution containing one selected from the group consisting of sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, and mixtures thereof,
Characterized in that it is carried out at 40 ~ 150 ℃ for 10 minutes ~ 3 hours,
Method for producing _{SiO 2} catalyst derived from biomass for TPA decomposition of PET.
6. The method of claim 5,
After the acid treatment in step (a),
Characterized in that it further comprises the step of filtering and washing the acid-treated rice husk,
Method for producing _{SiO 2} catalyst derived from biomass for TPA decomposition of PET.
6. The method of claim 5,
The heat treatment in step (b) is
Characterized in that it is carried out for 2 to 3 hours at a temperature of 600 ~ 700 ℃ by increasing by 3.5 ℃ per minute at room temperature,
Method for producing _{SiO 2} catalyst derived from biomass for TPA decomposition of PET.
delete Polyethylene terephthalate (PET, Polyethylene terephthalate), a biomass-derived SiO ₂ catalyst whose surface is modified by a thiol functional group (-SH), and water are mixed, and the polyethylene terephthalate is irradiated with microwaves to convert the polyethylene terephthalate into terephthalic acid (TPA). ) characterized in that it is hydrolyzed to,
TPA decomposition method of PET using biomass-derived SiO _{2 catalyst.}
11. The method of claim 10,
The method of hydrolyzing polyethylene terephthalate to terephthalic acid,
(a) preparing a mixture in which terephthalic acid is precipitated by reacting polyethylene terephthalate, a biomass-derived SiO _{2 catalyst, and water in a microwave reactor;}
(b) dissolving terephthalic acid by mixing sodium hydroxide with the mixture;
(c) filtering the mixture in which the terephthalic acid is dissolved to remove the residue and the catalyst;
(d) forming and obtaining a precipitate by adding an acidic solution to the mixture from which the residue and the catalyst are removed; and
(e) drying the obtained precipitate; characterized in that it comprises,
TPA decomposition method of PET using biomass-derived SiO _{2 catalyst.}
12. The method of claim 11,
The acidic solution is
Characterized in that it is one selected from the group consisting of sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, and mixtures thereof,
TPA decomposition method of PET using biomass-derived SiO _{2 catalyst.}

Images