KR20240016885A - Catalyst for producing cyclic carbonate from carbon dioxide and method for producing cyclic carbonate using the same - Google Patents

Abstract

The present invention relates to a metal oxide catalyst and a method for producing cyclic carbonate from carbon dioxide using the same. The metal oxide catalyst is represented by the following formula (1), and is used as a catalyst to mildly convert carbon dioxide and alkylene oxide compounds of various structures. Cyclic carbonates can be synthesized selectively and continuously without solvent under the following conditions:
[Formula 1]
XCo ₂ O ₄
In the above formula, X is Zn.

Description

Catalyst for producing cyclic carbonate from carbon dioxide and method for producing cyclic carbonate using the same {CATALYST FOR PRODUCING CYCLIC CARBONATE FROM CARBON DIOXIDE AND METHOD FOR PRODUCING CYCLIC CARBONATE USING THE SAME}

The present invention relates to a catalyst for producing cyclic carbonate from carbon dioxide and a method for producing cyclic carbonate using the same. Specifically, the present invention relates to a metal oxide catalyst and a metal oxide catalyst using the same as a catalyst to react an alkylene oxide compound with carbon dioxide to produce a cyclic carbonate. It is about manufacturing method.

Increasing carbon dioxide emissions in the atmosphere are a major concern in solving environmental problems such as global climate change and ocean acidification. Accordingly, researchers around the world have been working on converting carbon dioxide into value-added products for conservation. To date, various methods are being developed to produce carbon dioxide into value-added compounds such as methanol, urea, formic acid, cyclic carbonates and polycarbonates. Among them, the cyclic addition reaction of carbon dioxide and epoxide to cyclic carbonate is attractive from the perspective of atom economy and has a wide range of applications. Cyclic carbonates can be used as raw materials in the chemical industry, electrolytes in batteries, aprotic polar solvents in the synthesis of organic compounds, and as mediators in the synthesis of polymers and the pharmaceutical industry. The phosgene method has also been used to synthesize cyclic carbonates, but has disadvantages such as using highly toxic gases and producing hydrogen chloride as a by-product. Therefore, the synthesis of cyclic carbonates from the cycloaddition reaction of carbon dioxide and epoxide is a promising methodology and an alternative to the phosgene method. However, due to the stable and inert nature of carbon dioxide, it is difficult to activate the molecule and high energy is required for bond splitting. Also carbon dioxide High temperatures and pressures are needed to activate the molecules. Therefore, because efficient chemical fixation of carbon dioxide is difficult, the development of a catalyst system (or catalyst system or catalyst) to solve this problem is necessary.

In this regard, various homogeneous and heterogeneous catalysts are being studied for cycloaddition reactions. In particular, homogeneous catalysts such as ionic liquids, metal complexes, alkali metal halides, and organic catalysts are being studied. However, such a homogeneous catalyst has the disadvantage that it cannot be easily recovered from the reaction system, increasing post-treatment costs and harsh reaction conditions.

Meanwhile, this problem can be solved using heterogeneous catalysts such as metal-organic frameworks, metal oxides, grafted materials, and organic-inorganic hybrids. However, most heterogeneous catalysts require high pressure and temperature along with time-consuming and complex synthetic procedures. Therefore, there is still a need to develop an efficient catalyst system for chemical fixation of carbon dioxide.

Accordingly, the present invention seeks to provide a metal oxide-based catalyst for chemically immobilizing CO ₂ and epoxide into cyclic carbonate under mild conditions using CO ₂ and having high catalytic activity and cost efficiency.

KR 10-2021-0057803 A

The purpose of the present invention is to provide a metal oxide catalyst and a method for producing cyclic carbonate with high efficiency and selectivity by reacting carbon dioxide and alkylene oxide under mild conditions using the same.

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

In order to achieve the above object, the present invention provides a metal oxide catalyst involved in producing cyclic carbonate from carbon dioxide.

The metal oxide catalyst may have a spinel structure represented by the following formula (1).

[Formula 1]

XCo ₂ O ₄

In the above formula, X is Zn.

Additionally, the present invention provides a method for producing cyclic carbonate by reacting carbon dioxide and alkylene oxide using the compound represented by Formula 1 as a catalyst.

The metal oxide catalyst may have a flake or sphere shape.

The metal oxide catalyst may have a specific surface area of 10 to 60 m ² g ^-1 .

The alkylene oxide may be a compound represented by Formula 2 below, and the cyclic carbonate may be a compound represented by Formula 3 below.

[Formula 2]

[Formula 3]

In the above formula, R ₁ , R ₂ , R ₃ and R ₄ are each independently a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, or a substituted or unsubstituted oxy group.

The compound represented by Formula 2 may be any one selected from compounds represented by Formulas 2-1 to 2-5 below.

[Formula 2-1]

[Formula 2-2]

[Formula 2-3]

[Formula 2-4]

[Formula 2-5]

The compound represented by Formula 3 may be any one selected from compounds represented by Formulas 3-1 to 3-5 below.

[Formula 3-1]

[Formula 3-2]

[Formula 3-3]

[Formula 3-4]

[Formula 3-5]

The metal oxide catalyst may be used in an amount of 0.01 to 5 mol% based on the alkylene oxide.

The method for producing the cyclic carbonate may be to produce the cyclic carbonate by further including an inorganic salt.

The inorganic salt may be KI.

The inorganic salt may be used in an amount of 0.01 to 7 mol% based on the alkylene oxide.

The reaction temperature may be 80 to 140 °C.

The reaction pressure may be 1 to 5 MPa.

The reaction time may be 1 to 8 hours.

The present invention uses ZnCo ₂ O ₄ , a metal oxide, as a heterogeneous catalyst that is insoluble in carbon dioxide and various alkylene oxide compounds as reactants and cyclic carbonate as a product, and uses the catalyst and an inorganic salt together to produce a heterogeneous catalyst under mild conditions. Cyclic carbonates can be produced at high conversion rates and selectively without solvents.

In addition, since the catalyst of the present invention is a heterogeneous system, after reaction, the product and catalyst can be separated by simple precipitation and filtration, and the separated catalyst can be reused without a separate treatment process.

In addition, when using the catalyst of the present invention to react between carbon dioxide and an alkylene oxide compound, cyclic carbonate can still be produced with an excellent conversion rate despite reuse of the catalyst.

The effects of the present invention are not limited to the effects described above, and should be understood to include all effects that can be inferred from the configuration of the invention described in the detailed description or claims of the present invention.

Figure 1 shows a schematic diagram of the metal oxide catalyst synthesis method for producing cyclic carbonate from carbon dioxide according to the present invention.
Figure 2 shows the results of TGA analysis of the precursor of the catalyst prepared according to an embodiment of the present invention. Figure 2a shows the results of TGA analysis of the precursor of ZnCo-F, and Figure 2b shows the result of TGA analysis of the precursor of ZnCo-S. This shows the results of TGA analysis.
Figure 3 shows the results of XRD analysis to confirm the composition of the catalyst prepared according to an embodiment of the present invention and the results of XPS analysis to confirm the elements and oxidation state of the optimized catalyst. These are the XRD analysis results of the -S catalyst, and Figures 3d to 3d show the XPS analysis results of the ZnCo-F catalyst.
Figure 4 shows the results of overall XPS spectrum analysis of the ZnCo-F catalyst prepared according to an embodiment of the present invention.
Figure 5 shows the FE-SEM analysis results and EDX analysis results of the ZnCo-F catalyst prepared according to an embodiment of the present invention.
Figure 6 shows the FE-SEM analysis results and EDX analysis results of the ZnCo-S catalyst prepared according to an embodiment of the present invention.
Figure 7 shows the BET analysis results and TPD analysis results of the catalyst prepared according to an embodiment of the present invention. Figure 7a shows the BET analysis results of the ZnCo-F catalyst, and Figure 7b shows the BET analysis results of the ZnCo-S catalyst. The analysis results are shown, and Figure 7c shows the CO ₂ TPD analysis results of the ZnCo-F and ZnCo-S catalysts, and Figure 7d shows the NH ₃ TPD analysis results of the ZnCo-F and ZnCo-S catalysts.
Figure 8 shows the results of confirming the effect of reaction parameters (catalyst loading, pressure, temperature and time) on the cycloaddition reaction of propylene oxide and CO ₂ using a catalyst prepared according to an embodiment of the present invention, Figure 8a is the result of confirming the effect of catalyst loading, Figure 8b is the result of confirming the effect of Co ₂ pressure on the cycloaddition reaction, Figure 8c is the result of confirming the effect of catalyst performance according to reaction temperature change, and Figure 8d is the result of confirming the effect of catalyst performance on the reaction time. This is the result of confirming the effect of change in propylene oxide conversion rate (here, reaction conditions: a) 120 ℃, 2.5 MPa, 3 hb) ZnCo-F/KI 0.25: 0.5, 120 ℃, 3 hc) ZnCo-F/KI 0.25: 0.5, 2 MPa, 3 hd) ZnCo-F/KI 0.25: 0.5, 120 ℃, 2 Mpa).
Figure 9a shows the results of confirming the reusability of the catalyst for chemical fixation of CO ₂ from propylene oxide to propylene carbonate, and Figure 9b shows the results of confirming the reusability of the catalyst for new ZnCo-F (fresh-ZnCo-F) and used ZnCo-F (used ZnCo-F). -ZnCo-F) This is the FT-IR spectrum analysis result of the catalyst, and Figure 9c shows the XRD analysis result of new ZnCo-F and used ZnCo-F (here, reaction conditions: a) propylene oxide (20 g, 344.3 mmol) ), 120 °C, 2 MPa, 3 hours).
Figure 10 shows a possible reaction mechanism for the synthesis of cyclic carbonate from carbon dioxide using the ZnCo-F/KI catalyst prepared according to an example of the present invention.
Figure 11 shows the results of gas chromatography analysis of the cycloaddition reaction of the present invention performed at various temperatures (80, 100, and 120 °C), where PO stands for Propylene oxide and PC stands for Propylene carbonate. do.

It should be noted that in the following description, only the parts necessary to understand the embodiments of the present invention are described, and other parts of the description may be omitted as long as they do not distract from the gist of the present invention.

The terms or words used in the specification and claims described below should not be construed as limited to their usual or dictionary meanings, and the inventor should use the concept of terminology appropriately to explain his/her invention in the best way. It must be interpreted as meaning and concept consistent with the technical idea of the present invention based on the principle that it can be defined clearly. Therefore, the embodiments described in this specification and the configurations shown in the drawings are only preferred embodiments of the present invention, and do not represent the entire technical idea of the present invention, and therefore, various equivalents can be substituted for them at the time of filing the present application. It should be understood that there may be variations.

Hereinafter, the present invention will be described in detail.

The present invention provides a metal oxide catalyst involved in producing cyclic carbonate from carbon dioxide.

The metal oxide catalyst may have a spinel structure represented by the following formula (1):

[Formula 1]

XCo ₂ O ₄

In the above formula, X is Zn.

The metal oxide catalyst may have a flake or sphere shape and have a specific surface area of 10 to 60 m ² g ^-1 . In the present invention, the metal oxide catalyst has the advantage of excellent catalytic activity due to its high surface area.

In the present invention, the metal oxide having excellent activity and a large surface area can be prepared using a conventional urea assisted hydrothermal method or solvothermal method.

Additionally, the present invention provides a method for producing cyclic carbonate by reacting carbon dioxide and alkylene oxide using the compound represented by Formula 1 as a catalyst.

The alkylene oxide may be a compound represented by Formula 2 below, and the cyclic carbonate may be a compound represented by Formula 3 below.

[Formula 2]

[Formula 3]

In the above formula, R ₁ , R ₂ , R ₃ and R ₄ are each independently a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, or a substituted or unsubstituted oxy group.

In the present specification, substituted or unsubstituted may mean substituted or unsubstituted with one or more substituents selected from the group consisting of a deuterium atom, a halogen atom, an oxy group, an alkyl group, an alkenyl group, and an alkynyl group. Additionally, each of the above-exemplified substituents may be substituted or unsubstituted. For example, a biphenyl group may be interpreted as an aryl group, or as a phenyl group substituted with a phenyl group.

In this specification, examples of halogen atoms include fluorine atom, chlorine atom, bromine atom, or iodine atom.

In this specification, an alkyl group refers to a monovalent straight-chain or branched saturated hydrocarbon radical composed of only carbon and hydrogen atoms. Examples of such alkyl radicals include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, Includes, but is not limited to, pentyl, hexyl, octyl, dodecyl, etc.

As used herein, an alkenyl group refers to a hydrocarbon group containing at least one carbon double bond at the middle or end of an alkyl group having 2 or more carbon atoms. Alkenyl groups can be straight or branched. The number of carbon atoms is not particularly limited, but is 2 to 30, 2 to 20, or 2 to 10. Examples of alkenyl groups include, but are not limited to, vinyl, 1-butenyl, 1-pentenyl, 1,3-butadienyl aryl, styrenyl, and styrylvinyl groups.

As used herein, an alkynyl group refers to a hydrocarbon group containing at least one carbon triple bond at the middle or end of an alkyl group having 2 or more carbon atoms. Alkynyl groups can be straight or branched. The number of carbon atoms is not particularly limited, but is 2 to 30, 2 to 20, or 2 to 10. Specific examples of alkynyl groups may include, but are not limited to, ethynyl groups, propynyl groups, etc.

In the present specification, an oxy group may mean an oxygen atom bonded to an alkyl group as defined above. Oxy groups may include alkoxy groups and aryloxy groups. Alkoxy groups may be straight chain, branched or cyclic. The number of carbon atoms of the alkoxy group is not particularly limited, but may be, for example, 1 to 20 or 1 to 10. Examples of oxy groups include methoxy, ethoxy, n-propoxy, isopropoxy, butoxy, pentyloxy, hexyloxy, octyloxy, nonyloxy, decyloxy, and benzyloxy, but are limited to these. That is not the case.

In the present invention, the compound represented by Formula 2 may be any one selected from compounds represented by Formulas 2-1 to 2-5, but is not limited thereto.

[Formula 2-1]

[Formula 2-2]

[Formula 2-3]

[Formula 2-4]

[Formula 2-5]

In the present invention, the compound represented by Formula 3 may be any one selected from compounds represented by the following Formulas 3-1 to 3-5, but is not limited thereto.

[Formula 3-1]

[Formula 3-2]

[Formula 3-3]

[Formula 3-4]

[Formula 3-5]

In the present invention, the metal oxide catalyst is preferably used in an amount of 0.01 to 5 mol%, more preferably 0.1 to 3 mol%, and even more preferably 1 to 2 mol% relative to the alkylene oxide. If the amount of the metal oxide catalyst used is less than 0.01 mol%, the reaction rate is too slow, and if it is more than 5 mol%, the reaction rate and selectivity are no longer improved, reducing the economic efficiency of catalyst use.

In the present invention, a cyclic carbonate can be prepared by further including an inorganic salt along with the metal oxide catalyst for high conversion and selectivity, and the inorganic salt is preferably KI.

In the present invention, the inorganic salt is preferably used in an amount of 0.01 to 7 mol%, more preferably 0.1 to 4 mol%, and even more preferably 1 to 2 mol% relative to the alkylene oxide, and the inorganic salt If the amount of salt used is less than 0.01 mol% or more than 7 mol%, reaction performance may deteriorate.

In the present invention, when an inorganic salt is further included, the metal oxide catalyst and the inorganic salt are included in a molar ratio of 1:1 to 10, preferably 1:1 to 5, and more preferably 1:3 to improve reaction performance. It is desirable from this point of view.

In the present invention, the cyclic carbonate can be prepared through a typical cycloaddition reaction, and the reaction temperature is 80 to 140 ° C, preferably 100 to 130 ° C, and more preferably 120 ° C. there is. At this time, if the reaction temperature is too low, the reaction rate may slow down, and if the reaction temperature is too high, alkylene oxide may decompose and the final yield may decrease.

Additionally, in the above reaction, carbon dioxide may be supplied to the reactor at a pressure of 1 to 5 MPa, preferably 1 to 3 MPa, and more preferably 2 MPa. If the reaction pressure is less than 1 MPa, the reaction rate is significantly slow, and if it exceeds 5 MPa, there is no effect of increasing the reaction rate, which is uneconomical.

Additionally, the reaction time may be 1 to 8 hours, preferably 2 to 5 hours, and even more preferably 3 hours. If the reaction time is less than 1 hour, the reaction rate is significantly slow and the conversion rate of alkylene oxide may be reduced, and if the reaction time is longer than 8 hours, there is no effect of increasing the reaction rate, which is uneconomical.

The above description explains the technical idea of the present invention using one embodiment, and those skilled in the art will be able to make various modifications and variations without departing from the essential characteristics of the present invention. Accordingly, the embodiments described in the present invention are not intended to limit the technical idea of the present invention, but are for illustrative purposes, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be interpreted in accordance with the claims, and all technical ideas within the equivalent scope should be interpreted as being included in the scope of rights of the present invention.

Preparation example

Zinc nitrate hexahydrate, [Zn(NO ₃ )6H ₂ O, (99%)], Cobalt nitrate hexahydrate, [Co(NO ₃ ) _{2.6H 2} O, (99%) )]), Urea, [CO(NH ₂ ) ₂ , (98%)]), Zinc acetate dihydrate, [Zn(CH ₃ COO) ₂ 2H ₂ O, (99%)]) , Cobalt acetate tetrahydrate, [Co(CH ₃ COO) ₂ 4H ₂ O, (99%)], ethylene glycol (HOCH ₂ CH ₂ OH, AR]), ethanol, [ C ₂ H ₅ OH]) and acetone ([(CH ₃ ) ₂ CO]) were purchased from Alfa Aesar. Propylene oxide (C ₃ H ₆ O), Epichlorohydrin (C ₃ H ₅ ClO), allyl glycidyl ether (C ₆ H ₁₀ O ₂ ), tert-butyl glycyrrhizate Reactants such as tert-Butyl glycidyl ether (C ₇ H ₁₄ O ₂ ) and 1,2 Epoxy butane (C ₄ H ₈ O) were purchased from Sigma Aldrich and used without further purification.

Example

Example 1: ZnCo ₂ O ₄ synthesis of catalysts

1-1. Synthesis of ZnCo ₂ O ₄ flakes

ZnCo ₂ O ₄ flakes were synthesized using a urea assisted hydrothermal method. Specifically, a pink solution was prepared by dissolving 0.02M zinc nitrate hexahydrate, 0.04M cobalt nitrate hexahydrate, and 0.6M urea in 150 ml of deionized water for 30 minutes at room temperature. Then, the pink solution was transferred to a 200 ml Teflon lined stainless steel autoclave and reacted at 120 °C for 8 hours. After 8 hours, the autoclave was allowed to cool naturally at room temperature, and the obtained precipitate was washed several times with ethanol and deionized water and dried in a vacuum oven at 80 °C overnight. After drying, the obtained powder was annealed in an electric furnace at 400 °C for 2 hours at a rate of 3 °C per minute to obtain a pure crystalline phase of ZnCo ₂ O ₄ flakes. In the present invention, the ZnCo ₂ O ₄ flakes were named ZnCo-F ( Figure 1a).

1-2. Synthesis of ZnCo ₂ O ₄ solid spheres

ZnCo ₂ O ₄ solid spheres were synthesized using a solvothermal method. Specifically, 0.02M zinc acetate dihydrate and 0.04M cobalt acetate tetrahydrate were dissolved in 100ml of ethylene glycol for 30 minutes to prepare a pink solution. The homogeneously dissolved solution was transferred to a 200ml round bottom flask and reacted in an oil bath at 170°C for 2 hours. As the reaction time progressed, the initially pink solution turned purple. After reacting for 2 hours, the obtained solution was naturally cooled to room temperature. The precipitate was washed several times with acetone and deionized water and then dried at 80°C in a vacuum oven overnight. After drying, the obtained powder was annealed in air at a temperature increase rate of 0.5°C per minute in an electric furnace at 350°C for 5 hours to obtain crystalline ZnCo ₂ O ₄ spheres. In the present invention, the ZnCo ₂ O ₄ spheres were named ZnCo-S. (Figure 1b).

Example 2: Cyclic Carbonate Synthesis

2-1. Synthesis of a compound (4-methyl-1,3-dioxolan-2-one) represented by Formula 3-1

Alkylene oxide (20g, 344.3mmol) represented by the following formula 2-1, ZnCo-F (0.25g, 0.29mol%) prepared in Example 1-1, and inorganic salt (KI) (0.5g, 0.87mol) %) was added to a 100 ml Teflon-lined stainless steel autoclave. The inside of the autoclave reactor was purged three times with CO ₂ to remove air, and then the reactor was pressurized (2 MPa). Reaction was performed at 120°C for 3 hours. After reacting for 3 hours, the reactor was naturally cooled to room temperature, and the CO ₂ remaining inside the reactor was slowly released. Afterwards, the catalyst was separated by centrifugation, and the product (a compound represented by the following formula 3-1) was confirmed by gas chromatography ( ¹ H NMR, ¹³ C NMR). The chemical structure of the product is as follows.

[Formula 3-1]

^1H NMR (400 MHz, DMSO-d6): ∂4.94-4.86(1H, m), 4.59-4.55(1H, 16, t), 4.08-4.04(1H, m), 1.38-1.36 (3H, d)

¹³ C NMR (100 MHz, DMSO-d6): ∂155.35, 74.21, 70.92, 19.20

2-2. Synthesis of a compound (4-((allyloxy)methyl)-1,3-dioxolan-2-one) represented by Formula 3-2

In Example 2-1, the procedure was carried out under the same materials and conditions except that alkylene oxide represented by the following formula 2-2 was used instead of the alkylene oxide represented by the formula 2-1, and the result was obtained by the formula 3-2 below. The indicated compounds were synthesized.

[Formula 2-2]

[Formula 3-2]

¹ H NMR (400 MHz, DMSO-d6): ∂5.93-5.83(1H,m), 5.29-5.15(2H, m), 4.96-4.91(1H, m), 4.55-4.51(1H, 16, t) , 4.29-4.26(1H, m), 4.02-4(2H, m), 3.68-3.56(2H, m)

¹³ C NMR (100 MHz, DMSO-d6): ∂154.98, 134.61, 116.74, 75.48, 71.38, 69.11, 66.10

2-3. Synthesis of a compound (4-ethyl-1,3-dioxolan-2-one) represented by Formula 3-3

In Example 2-1, the procedure was carried out under the same materials and conditions except that alkylene oxide represented by the following formula 2-3 was used instead of the alkylene oxide represented by the formula 2-1, and the result was obtained by the formula 3-3 below. The indicated compounds were synthesized.

[Formula 2-3]

[Formula 3-3]

^1H NMR (400 MHz, DMSO-d6): ∂4.78-4.71(1H, m), 4.59-4.55(1H, 16, t), 4.17-4.13(1H, m), 1.75-1.68(2H, m) , 0.94-0.90 (3H, t, 16)

¹³ C NMR (100 MHz, DMSO-d6): ∂155.16, 78.17, 69.06, 26.19, 8.51

2-4. Synthesis of a compound (4-(chloromethyl)-1,3-dioxolan-2-one) represented by Chemical Formula 3-4

In Example 2-1, the procedure was carried out under the same materials and conditions except that alkylene oxide represented by the following formula 2-4 was used instead of the alkylene oxide represented by the formula 2-1, and the result was obtained by the formula 3-4 below. The indicated compounds were synthesized.

[Formula 2-4]

[Formula 3-4]

^1H NMR (400 MHz, DMSO-d6): ∂5.16-5.11(1H, m), 4.63-4.59(1H, t, 16), 4.31-4.28 (1H, m), 4.03-3.92(2H, m)

¹³ C NMR (100 MHz, DMSO-d6): ∂154.95, 75.40, 67.33, 45.73

2-5. Synthesis of a compound (4-(tert-butoxymethyl)-1,3-dioxolan-2-one) represented by Formula 3-5

In Example 2-1, except that alkylene oxide represented by Formula 2-5 was used instead of alkylene oxide represented by Formula 2-1, the procedure was performed under the same materials and conditions as Formula 3-5 below. The indicated compounds were synthesized.

[Formula 2-5]

[Formula 3-5]

^1H NMR (400 MHz, DMSO-d6): ∂4.90-4.85(1H, m), 4.53-4.49(1H, t, 16), 4.25-4.22(1H, m), 3.62-3.58(1H, m) , 3.50-3.48(1H, m), 1.15(9H, s)

¹³ C NMR (100 MHz, DMSO-d6): ∂155.03, 75.63, 72.99, 66.15, 61.34, 27.11

Experiment example

Experimental Example 1: Confirmation of catalyst characteristics

1-1. TGA analysis

The pure phase formation temperature of ZnCo-F and ZnCo-S prepared in Examples 1-1 and 1-2 was confirmed through TGA analysis (FIG. 2). A total weight loss of 26.50 and 51.48% was observed for the pre-annealed powders (hereinafter “precursors”) of ZnCo-F and ZnCo-S prepared in Examples 1-1 and 1-2, respectively. As observed from the TGA curve in Figure 2, it can be seen that temperatures of 400 and 350 °C were used to convert the precursors into ZnCo-F and ZnCo-S catalysts, respectively.

1-2. XRD analysis

The phase purity and crystal structure of the ZnCo-F and ZnCo-S catalysts prepared after annealing were confirmed through ). As can be seen in Figure 3a, the ZnCo-F and ZnCo-S catalysts exhibit nine high intensity diffraction peaks that can be well assigned to the standard data of the face-centered cubic orthogonal ZnCo ₂ O ₄ structure (JCPDS No. 23-1390). Pay it. At 2θ values of 18.98, 31.28, 36.86, 38.61, 44.8, 55.73, 59.33, 65.31 and 77.08°, the peaks are (111), (220), (311), (222), (400), (422), (511) ), (440), and (533), respectively. The absence of extra peaks clearly indicates phase purity of the synthesized material.

1-3. XPS analysis

The elements and oxidation states in the ZnCo-F catalyst were confirmed through XPS analysis (Thermo Fisher, USA, ESCALAB MLII spectrometer equipped with Al Kα (1486.6 eV) X-ray source). Referring to Figure 4, it can be seen that the entire XPS spectrum of the ZnCo-F catalyst indicates the presence of Zn, Co, O, and C elements. Additionally, the peaks of Zn, Co, and O elements were fitted using the Gaussian fitting method. Figure 3b shows the deconvoluted XPS spectrum of Zn 2p, showing two peaks at 1043.2 and 1020.1 eV attributed to Zn 2p _1/2 and Zn 2p _3/2 , respectively. This indicates that Zn ²⁺ exists in the ZnCo-F catalyst. _Additionally , the _deconvoluted Peaks tuned to 779.16 and 794.13 eV represent Co ³⁺ and 780.54 and 795.7 eV represent Co ²⁺ . The integrated area of the Co ³⁺ peak is larger than that of the Co ²⁺ peak, indicating that Co ³⁺ is the main oxidation state of the ZnCo-F catalyst. It can also be seen in Figure 3c the presence of satellite peaks (marked “Sat.”) at 788.8 eV and 804.0 eV, which evidence the presence of Co cations in the +3 oxidation state. Figure 3d shows a high-resolution scan spectrum of O 1s that can be fit to three peaks. The peak at 529.0 eV (O2) corresponds to the metal-oxygen bond, while the peaks at 528.1 (O1) and 530.7 eV (O3) correspond to weakly coordinated oxygen ions at the surface.

1-4. FE-SEM analysis

The shape of the synthesized ZnCo ₂ O ₄ catalyst was confirmed through FE-SEM analysis, and the results are shown in Figures 5 and 6. Figure 5 shows the FE-SEM image and EDX color mapping results of the ZnCo-F catalyst. Figures 5a to 5c are images showing the hierarchical flake like ZnCo-F catalyst structure at different magnifications. Referring to Figures 5A-5C, it can be seen that the flake size ranges from 4-6 μm with an average thickness of 60 nm. Additionally, EDX color mapping was performed to confirm the elemental composition and distribution within the flake-like structure (Figure 5d). Referring to Figure 5d, elemental color mapping can confirm the uniform distribution of Zn, Co, and O elements within the scanned area of the flake. Additionally, the atomic percentages of Zn, Co, and O elements in the ZnCo-F catalyst obtained from EDX analysis are shown in Table 1 below.

ingredient Line type apparent concentration k ratio weight% Weight standard deviation% atom% O K series 27.38 0.09215 30.65 0.26 62.68 Co K series 35.04 0.35036 47.61 0.33 26.43 Zn L series 4.41 0.04414 21.74 0.32 10.88 Total: - - - 100.00 - 100.00

Meanwhile, Figure 6 shows the FE-SEM image and EDX color mapping results of the ZnCo-S catalyst. Figures 6a to 6c show solid spheres of the ZnCo-S catalyst with an average diameter of 0.7 μm at different magnifications. Uniform distribution of Zn, Co, and O elements in the solid sphere was confirmed by EDX analysis (FIG. 6d). Additionally, the elemental compositions of Zn, Co, and O elements observed in ZnCo-S are shown in Table 2.

ingredient Line type apparent concentration K ratio weight% Weight standard deviation% atom% O K series 27.10 0.09120 30.79 0.22 63.29 Co K series 26.19 0.26192 34.40 0.27 19.20 Zn L series 8.87 0.08867 34.80 0.28 17.51 Total: 100.00 100.00

1-5. BET Analysis

The surface area, pore volume, and pore size distribution of the catalyst were confirmed through BET (Brunauer-Emmett-Teller) analysis, and the results are shown in Table 3 below.

catalyst surface area
(m ² g ^-One ) pore volume
(cm ³ g ^-One ) pore size
(nm) ZnCo-F 40.89 0.21 20.58 ZnCo-S 25.70 0.10 16.36

Referring to Table 3 above, the ZnCo-F and ZnCo-S catalysts of the present invention may have excellent catalytic activity due to their high surface area.

In addition, referring to Figures 7a and 7b, it can be seen that the nitrogen adsorption-desorption isotherms of ZnCo-F and ZnCo-S catalysts show the characteristics of a type IV loop with an H3 type hysteresis loop where mesopores exist in nature. . The ZnCo-F and ZnCo-S catalysts exhibit BET specific surface areas of 40.89 and 25.70 m ² g ^-1 , respectively. The total pore volume and average pore diameter of the ZnCo-F catalyst were observed to be 0.21 cm ³ g ^-1 and 20.58 nm, respectively. On the other hand, the ZnCo-S catalyst was observed to have a total pore volume of 0.10 cm ³ g ^-1 and an average pore diameter of 16.36 nm.

1-6.TPD analysis

The acidic and basic properties of the catalyst were confirmed through NH ₃ temperature-programmed desorption (NH ₃ -TPD) and CO ₂ temperature-programmed desorption (CO ₂ -TPD), respectively. The acidic and basic properties of the catalyst play an important role in achieving excellent conversion and selectivity in cycloaddition reactions. Therefore, the acidic and basic properties of the catalyst of the present invention were analyzed using NH ₃ and CO ₂ TPD, respectively, and the results are shown in Figures 7c, 7d and Table 4 below.

a) _CO2 TPD analysis of ZnCo-F and ZnCo-S catalyst weak
(<200℃) middle
(200-450℃) strong
(>450℃) total evolution
CO ₂ (mmol g ^-1 ) ZnCo-F 0.41 (73) 0.53 (208) 0.80(502),17.76(860) 19.5 ZnCo-S 0.67(73) 0.87(209) 22.24(854) 23.78 b) NH ₃ TPD analysis of ZnCo-F and ZnCo-S catalyst weak
(<200℃) middle
(200-450℃) strong
(>450℃) total evolution
NH ₃ (mmol g ^-1 ) ZnCo-F 0.40(98) 0.55(212) 0.92(516),16.91(860) 18.78 ZnCo-S 0.58 (102) - 18.75(861) 19.33

The amount of desorption was recorded in various temperature regimes: <200 °C (weak region), 200–400 °C (moderate region), and >400 °C (strong region). Referring to a) of Table 4 above, CO ₂ desorption was recorded in all regions for both catalysts. It can be seen that the ZnCo-F and ZnCo-S catalysts of the present invention exhibit a major peak in the strong region (>450 °C) due to the presence of a strong basic site (Figure 7c). The total basicity of ZnCo-F and ZnCo-S catalysts was calculated to be 19.5 and 23.78 mmol g ^-1 , respectively.

Meanwhile, referring to b) of Table 4, it can be seen that NH ₃ desorption is observed in the entire region for the ZnCo-F catalyst. However, it can be confirmed that the ZnCo-S catalyst shows NH ₃ desorption only in weak and strong regions. Referring to Figure 7d, the presence of strongly acidic sites can be confirmed through the main concentrated peak observed for both catalysts in the strong region. The total acidity of ZnCo-F and ZnCo-S catalysts was calculated to be 18.78 and 19.33 mmol g ^-1 , respectively. If both acidic and basic sites are present in the synthesized catalyst, it can act as a dual-function catalyst. Therefore, the catalyst of the present invention has an excellent surface area and excellent acid-base properties, making it effective in accelerating the CO ₂ utilization reaction.

Experimental Example 2: CO ₂ Confirmation of catalyst performance for chemical fixation of

The ZnCo-F and ZnCo-S catalysts of the present invention were used as sustainable heterogeneous catalysts for CO ₂ utilization. For the cycloaddition reaction to prepare propylene carbonate (Formula 3-1), the reaction was performed on a catalyst using propylene oxide (Formula 2-1) and CO ₂ as model substrates along with an inorganic salt. The presence of strong Lewis acidity, basicity and high surface area of ZnCo ₂ O ₄ along with inorganic salts may be efficient for CO ₂ utilization. Referring to Table 5 below (catalytic performance of the catalyst for chemical fixation of CO ₂ ), the cycloaddition reaction of CO ₂ and propylene oxide to propylene carbonate was initially performed without a catalyst and did not show catalytic performance (Table 5 Item 1).

item catalyst Conversion Rate (%) Selectivity (%) One - - - 2 KCl 0.5 ≥ 99 3 KBr 1.71 ≥ 99 4 KI 19.6 ≥ 99 5 ZnCo-S Trace - 6 ZnCo-F Trace - 7 ZnCo-F/KI 99.9 ≥ 99 8 ZnCo-F/KCl 10.2 ≥ 99 9 ZnCo-F/KBr 17.1 ≥ 99 10 ZnCo-S/KI 95 ≥ 99

Then, cycloaddition reactions were performed for inorganic salts such as KCl, KBr, and KI (entries 2, 3, and 4 in Table 5). This showed a shallow conversion of propylene oxide, and the nucleophilic and halogenated anion escape abilities increased in the order of KCl < KBr < KI. Surprisingly, the ZnCo-F and ZnCo-S catalysts alone (without cocatalyst) were not highly active and showed only trace catalytic activity (entries 5 and 6 in Table 5). Therefore, ZnCo-F and ZnCo-S catalysts were used together with inorganic salts for the cycloaddition reaction. ZnCo-F/KI demonstrated excellent conversion of propylene oxide (99.9%) with good selectivity of propylene carbonate (≥99%) under mild reaction conditions (entry 7 in Table 5). From these results, it was confirmed that the presence of a catalyst is important. On the other hand, when the ZnCo-F catalyst was used with KCl and KBr to perform the cycloaddition reaction of propylene oxide and CO ₂ , the catalyst performance was poor (entries 8 and 9 in Table 5). However, ZnCo-F showed superior catalytic performance in the presence of KI compared to KCl and KBr due to the strong nucleophilic nature of KI and excellent escape ability. Cycloaddition reactions were also performed on ZnCo-S/KI, which demonstrated good conversion of propylene oxide (95%) along with good selectivity (≥99%) of propylene carbonate (entry 10 in Table 5).

Then, the reaction parameters (catalyst loading, pressure, temperature and time) for the cycloaddition reaction of propylene oxide and CO ₂ were determined using a ZnCo-F/KI catalyst system with high conversion (99.9%) and selectivity (≥99%). etc.) was investigated. First, the catalyst loading effect was investigated through changes in the ratio of ZnCo-F and KI. Different weights (0.1, 0.25, and 0.5 g) of ZnCo-F catalyst were screened with different KI weights (0.1, 0.25, and 0.5 g). Referring to Figure 8a, it shows that the conversion rate of propylene oxide increases as the weight of KI increases. Complete conversion of propylene oxide to propylene carbonate was observed at a catalytic ratio of 0.25/0.5 of ZnCo-F/KI. Further increase in catalyst concentration (>0.25 g) did not affect the reaction. Additionally, the ratio of ZnCo-F/KI catalyst (0.25/0.5 g) was kept constant to investigate the effect of CO ₂ pressure on the cycloaddition reaction (Figure 8b). Referring to Figure 8b, an increase in propylene oxide conversion with excellent selectivity (≥99%) was observed as the CO ₂ pressure increased from 1 to 2.5 MPa. The catalyst (ZnCo-F/KI) showed excellent conversion of propylene oxide (99.9%) at a pressure value of 2 MPa. It was found that as the pressure of CO ₂ increased in the liquid phase, the solubility of CO ₂ increased, thereby improving catalyst performance. Additionally, it was confirmed that increasing CO ₂ pressure did not affect catalyst performance.

Afterwards, the reaction was performed at various reaction temperatures to examine the effect of temperature on catalyst performance. Referring to Figure 8c, it can be seen that the reaction is sensitive to temperature. The catalyst performance gradually increased from 60 °C to 100 °C, and the catalyst showed excellent propylene oxide conversion (99.9%) at 120 °C. Increasing the reaction temperature from 100 °C to 120 °C increased the conversion rate from 34.8% to 99.9%. This confirmed that the conversion rate at low reaction temperature was not high, possibly because the low reaction temperature could not provide sufficient energy to promote chemical fixation of CO ₂ within a fixed time. Meanwhile, to study the effect of reaction time on the catalytic performance of the cycloaddition reaction, the reaction was performed with time variations. Figure 8d shows the change trend of propylene oxide conversion rate according to reaction time. When using the catalyst prepared according to an example of the present invention, it was confirmed that the conversion rate of propylene oxide increased from 31.1% to 99.9% as the reaction time increased from 1 hour to 3 hours. All the above results can confirm the potential application of ZnCo-F/KI catalyst system for chemical fixation of CO ₂ to propylene carbonate, which shows the excellent It shows excellent conversion rate of propylene oxide (99.9%) along with selectivity.

Meanwhile, in order to confirm the catalytic applicability of the ZnCo-F/KI catalyst of the present invention, various epoxides were investigated along with CO ₂ . The _CO2 utilization of all terminal epoxides with electron donating and electron withdrawing was investigated on ZnCo-F/KI, which showed excellent catalytic performance (Table 6: Substrates of ZnCo-F/KI for cycloaddition reactions Range, reaction conditions: epoxide (20g, 344.3mmol), ZnCo-F/KI 0.25:0.5, 120 ℃, 2.0 Mpa).

item reactant product hour
(h) conversion rate
(%) selectivity
(%) One 3 99.9 ≥ 99 2 2 99.9 ≥ 99 3 5 98 ≥ 99 4 5 81 ≥ 99 5 5 99.9 ≥ 99

The catalyst of the present invention completely converted propylene oxide (99.9%) with excellent selectivity (≥99%) within 3 hours (entry 1 in Table 6). Additionally, it showed excellent conversion of allyl glycidyl ether (99.9%) within 2 h, which may be due to the presence of the terminal allyl functional group of the substrate, which promotes the reaction (entry 2 in Table 6). Additionally, the catalyst performance effects for electron donating and withdrawing groups were confirmed. It was confirmed that a reaction time slightly longer than 3 hours was required to obtain high reaction yield. The catalyst of the present invention achieved conversion rates of 98% for 1,2 epoxy butane and 81% for epichlorohydrin in 5 hours (entries 3 and 4 of Table 6). Additionally, it was confirmed that 5 hours were required to completely convert tert-butyl glycidyl ether (99.9%) due to the steric hindrance effect (entry 5 in Table 6). Additionally, as a result of comparing the catalyst of the present invention with a recently published metal oxide-based catalyst system, it was confirmed that it is very efficient in chemically fixing CO ₂ with epoxide into a cyclic carbonate (Table 7: Ring of epoxide and CO ₂ Comparison of various metal oxides for chemical addition reactions).

catalyst temperament Catalytic amount enter
(MPa) hour
(h) temperature
(℃) conversion rate
(%) selectivity
(%) transference number
(%) [Zn(II)NMeTPyP] ⁴⁺ [I] ₄ @PCN-224
(Sharma et al., 2019) 10 mmol 50mg 0.8 MPa 24 90 ＞99 - ＞99 M-BTC MOF (M=Mn, Co, Ni)
(Wu et al., 2018) 344.3 mmol
(20 g) 1.5wt% 3.0 MPa 9 105 94.54 95.34 90.13 (Dai et al., 2010) 28.6 mmol 0.5g 2.5 MPa 12 140 - 97.7 76.8 _{CuCo2O4 _}
(Prasad et al., 2019) 17.21 mmol
(1000 mg) 5wt% 2.0 MPa 3 80 98 92 90 Mg-Al
mixed oxides
(Yamaguchi et al., 1999) 4 mmol
(using 3 ml DMF solvent) - 5 atm. 24 120 96 - 88 Mn-Ba (Kulal et al., 2019) 30.1 mmol
(using 11 ml DMF solvent) 20wt% 2.5 MPa
6
160
98.1
-
96
Sn-Ni (Kulal et al., 2019) 30.1 mmol
(using 11 ml DMF solvent) 20wt% 2.5 MPa
8 160 96.9 - 90.2 _{ZnCo2O4 _}
344.3 mmol
(20 g)
Solvent-free 0.29 mol% (1.25 wt%) 2.0 MPa 3 120 99.9 ≥ 99 99.9

Stability is an essential factor for sustainable catalysts and practical applications. The reaction of the present invention was carried out to investigate the reusability of the ZnCo-F catalyst of the present invention for the cycloaddition reaction of CO ₂ and propylene oxide under optimized reaction conditions. After completion of the reaction, the ZnCo-F catalyst was separated using a simple centrifugation method. It was washed with water and then with ethanol, dried in a vacuum oven at 60°C for 8 hours, and then used in a cycloaddition reaction.

Referring to Figure 9a, it shows that the ZnCo-F catalyst was successfully used four times without significant change in catalyst performance. In addition, in Figures 9b and 9c, the FT-IR and XRD spectra of the new catalyst and the used catalyst did not show significant changes, and it can be seen that the structural stability of the ZnCo-F catalyst is high.

A possible reaction mechanism for the synthesis of cyclic carbonate using the ZnCo-F/KI catalyst prepared according to an example of the present invention is shown in Figure 10. In the present invention, the physicochemical results show that the ZnCo-F catalyst can activate CO ₂ and epoxide because it has a good surface area and both strong Lewis acid and strong Lewis base sites exist. The synergistic effect between ZnCo-F and KI can efficiently promote the cycloaddition reaction of CO ₂ and epoxide. Initially, CO ₂ is activated by the Lewis basic site (O ₂ ^- ) of the ZnCo-F catalyst to form anionic carboxylate species. At the same time, the Lewis acidic metal center activated epoxide (I), confirming that Lewis acidity and basicity of the catalyst play an important role in the cycloaddition reaction. Additionally, ring opening of the epoxide to the less sterically hindered carbon atom of the epoxide activated simultaneously by the nucleophilic attack of the iodide anion of KI generates the iodo-alkoxide intermediate (II). The resulting iodine-alkoxide intermediate then interacts with the carboxylate to form alkyl carbonate (III). Finally, it was confirmed that a cyclic carbonate product was generated due to intramolecular cyclization and regeneration of catalyst (IV).

Claims (16)

In the metal oxide catalyst involved in producing cyclic carbonate from carbon dioxide, the metal oxide catalyst has a spinel structure represented by the following formula (1):
[Formula 1]
XCo ₂ O ₄
In the above equation,
X is Zn. According to paragraph 1,
The metal oxide catalyst is a catalyst having a flake or sphere shape. According to paragraph 1,
The metal oxide catalyst has a specific surface area of 10 to 60 m ² g ^-1 . Method for producing cyclic carbonate by reacting carbon dioxide and alkylene oxide using a compound represented by the following formula (1) as a catalyst:
[Formula 1]
XCo ₂ O ₄
In the above equation,
X is Zn. According to paragraph 4,
A method of producing a cyclic carbonate, wherein the alkylene oxide is a compound represented by the following formula (2), and the cyclic carbonate is a compound represented by the following formula (3):
[Formula 2]

[Formula 3]

In the above formula, R ₁ , R ₂ , R ₃ and R ₄ are each independently a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, or a substituted or unsubstituted oxy group. According to paragraph 4,
A method of producing a cyclic carbonate, wherein the compound represented by Formula 2 is any one selected from the compounds represented by Formulas 2-1 to 2-5:
[Formula 2-1]

[Formula 2-2]

[Formula 2-3]

[Formula 2-4]

[Formula 2-5]
According to paragraph 4,
A method of producing a cyclic carbonate, wherein the compound represented by Formula 3 is any one selected from compounds represented by the following Formulas 3-1 to 3-5:
[Formula 3-1]

[Formula 3-2]

[Formula 3-3]

[Formula 3-4]

[Formula 3-5]
According to paragraph 4,
A method for producing a cyclic carbonate, wherein the metal oxide catalyst is used in an amount of 0.01 to 5 mol% based on the alkylene oxide. According to paragraph 4,
The method of producing a cyclic carbonate further includes an inorganic salt. According to clause 9,
A method for producing a cyclic carbonate, wherein the inorganic salt is KI. According to clause 9,
A method for producing a cyclic carbonate, wherein the inorganic salt is used in an amount of 0.01 to 7 mol% based on the alkylene oxide. According to paragraph 4,
A method for producing a cyclic carbonate, wherein the reaction temperature is 80 to 140 °C. According to paragraph 4,
A method for producing a cyclic carbonate, wherein the reaction pressure is 1 to 5 MPa. According to paragraph 4,
A method for producing a cyclic carbonate, wherein the reaction time is 1 to 8 hours. According to paragraph 4,
A method for producing a cyclic carbonate, wherein the metal oxide catalyst has a flake or sphere shape. According to paragraph 4,
A method of producing a cyclic carbonate, wherein the metal oxide catalyst has a specific surface area of 10 to 60 m ² g ^-1 .