KR101755523B1 - Polyoxometalate catalyst, preparing method thereof, and preparing method of cyclic carbonates using the same - Google Patents

Abstract

A process for producing the polyoxometallate catalyst, and a process for producing the cyclic carbonate using the polyoxometallate catalyst.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a polyoxometallate catalyst, a method for producing the same, and a process for producing a cyclic carbonate using the catalyst,

The present invention relates to a polyoxometallate catalyst, a process for producing the polyoxometallate catalyst, and a process for producing a cyclic carbonate using the polyoxometallate catalyst.

The efficient transformation of said carbon dioxide (CO ₂ ) to useful compounds such as formic acid, methanol, ureas, carboxylates, polycarbonates and polyurethanes is particularly advantageous when CO ₂ is potentially cheaper And it is very attractive because it is a rich C1 building block. Of these compounds, cyclic carbonates produced by the cycloaddition of CO ₂ to the epoxide are attractive chemicals. These compounds are commonly used as electrolyte components in polar lithium-ion batteries, polar aprotic solvents, and chemical intermediates. Typically, these compounds are synthesized using toxic and hazardous reagents such as phosgene. Therefore, the demand for such an efficient catalyst for the conversion of carbon dioxide is increasing. Various metal-based catalysts have shown activity against coupling of epoxide to carbon dioxide; Among them, zinc (Zn) composites have attracted a lot of research attention due to their natural richness, low cost and low toxicity. Many homogeneous catalyst systems such as ZnBr ₂ / n-Bu ₄ , ZnBr ₂ -Ph ₄ PI and hydroxyapatite-bonded zinc complex (ZnHAP) are effective in the production of cyclic carbonates Have been reported. Nonetheless, although zinc glutarate compounds have been studied as heterogeneous catalysts, the need for ZnO nanocrystals for easy catalyst recovery and reutilization, which can be more easily prepared, Still high.

ZnO nanocrystals (ZnO NCs) have recently emerged as heterogeneous catalysts in a variety of reactions, due to their excellent stability, easy synthesis and high surface area as well as low toxicity and cost. However, since the strong Lewis acid / base catalysts exhibit a high conversion rate for the production of cyclic carbonates, the ZnO NCs, which exhibit both weak Lewis acid and base properties, can be used as catalysts for the production of cyclic carbonates Was considered less. Introduction of suitable inorganic molecules onto the surface of NCs is an efficient process in order to improve the activity of the catalyst by changing the surface properties of the metal oxide NCs.

Polyoxometalates (POMs), metal-oxygen cluster compounds, are very well known inorganic molecules that can change the properties of metal and metal oxide NCs by well adhering to their surfaces. POMs have a variety of uses in catalysts due to their excellent redox properties, unique molecular structure, electronic versatility, and ease of availability.

The present invention provides a polyoxometallate catalyst, a process for producing the polyoxometallate catalyst, and a process for producing a cyclic carbonate using the polyoxometallate catalyst.

However, the problems to be solved by the present invention are not limited to the above-mentioned problems, and other problems not mentioned can be clearly understood by those skilled in the art from the following description.

The first aspect of the present invention is directed to a method of forming a ZnO nanoparticle, TiO ₂ nanoparticle, or Al ₂ O ₃ Nanoparticles and a polyoxometallate present on the surface of the nanoparticles.

The second aspect of the present invention is directed to a nanoparticle comprising ZnO nanoparticles, TiO ₂ nanoparticles, or Al ₂ O ₃ TiO ₂ nanoparticles or Al ₂ O ₃ nanoparticles by solvothermal reaction by heating a mixture of a solution containing a precursor for preparing nanoparticles and a solution containing polyoxometallate, There is provided a process for preparing a catalyst according to the first aspect of the present invention, which comprises obtaining a catalyst comprising nanoparticles and a polyoxometallate present on the surface of the nanoparticles.

A third aspect of the invention is directed to a method of making a ZnO nanoparticle, TiO ₂ nanoparticle, or Al ₂ O ₃ A cyclic carbonate having 2 to 5 carbon atoms by the cyclization addition reaction of an alkylene oxide having 2 to 5 carbon atoms with CO ₂ in the presence of a nanoparticle and a catalyst containing polyoxometallate present on the surface of the nanoparticle Which comprises reacting a cyclic carbonate of formula

According to one embodiment of the present disclosure, there are provided polyoxometallates and ZnO nanoparticles, TiO ₂ nanoparticles, or Al ₂ O ₃ By using nanoparticles, a polyoxometallate catalyst can be easily produced by one-pot synthesis, which is used for a cyclic carbonate production reaction by the cyclization addition reaction of CO ₂ .

The polyoxometallate-based catalyst according to one embodiment herein exhibits significantly improved catalytic performance as compared to conventional catalysts prepared without polyoxometallate and can be reused many times without reduction in activity I have.

1 (a) to 1 (d) are graphs showing XRD patterns of a polyoxometallate-ZnO catalyst in one embodiment of the present invention.
Figures 2 (a) - (d) are SEM and TEM images of a polyoxometallate-ZnO catalyst in one embodiment of the present application.
3 (a) to 3 (d) are elemental mapping images of a polyoxometallate-ZnO catalyst in one embodiment of the present invention.
Figures 4 (a) and 4 (b) are graphs showing FT-IR spectra of the polyoxometallate-ZnO catalyst in one embodiment of the present application.
5 is a graph showing the activity of the polyoxometallate-ZnO catalyst for the cyclization addition reaction of CO ₂ in one embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. It should be understood, however, that the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In the drawings, the same reference numbers are used throughout the specification to refer to the same or like parts.

Throughout this specification, when a part is referred to as being "connected" to another part, it is not limited to a case where it is "directly connected" but also includes the case where it is "electrically connected" do.

Throughout this specification, when a member is " on " another member, it includes not only when the member is in contact with the other member, but also when there is another member between the two members.

Throughout this specification, when an element is referred to as " including " an element, it is understood that the element may include other elements as well, without departing from the other elements unless specifically stated otherwise. The terms " about ", " substantially ", etc. used to the extent that they are used throughout the specification are intended to be taken to mean the approximation of the manufacturing and material tolerances inherent in the stated sense, Accurate or absolute numbers are used to help prevent unauthorized exploitation by unauthorized intruders of the referenced disclosure. The word " step (or step) " or " step " used to the extent that it is used throughout the specification does not mean " step for.

Throughout this specification, the term " combination (s) thereof " included in the expression of the machine form means a mixture or combination of one or more elements selected from the group consisting of the constituents described in the expression of the form of a marker, Quot; means at least one selected from the group consisting of the above-mentioned elements.

Throughout this specification, the description of "A and / or B" means "A or B, or A and B".

Hereinafter, embodiments and examples of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to these embodiments and examples and drawings.

The first aspect of the present invention is directed to a method of forming a ZnO nanoparticle, TiO ₂ nanoparticle, or Al ₂ O ₃ Nanoparticles and a polyoxometallate present on the surface of the nanoparticles.

In one embodiment of the present invention, the polyoxometallate may be represented by the following general formula (1), but is not limited thereto:

[Chemical Formula 1]

H _(e-az) A _a ^{z +} [X _x M ¹ _m M ² _n O _y ] ^e- ;

In Formula 1, H is hydrogen; A is an alkali metal element selected from Group 1 of the periodic table; X is an element selected from group 14 or group 15 of the periodic table; M ¹ is an element selected from the group consisting of molybdenum, vanadium, tungsten, niobium, tantalum, and combinations thereof; M ² is an element selected from the group consisting of cobalt, iron, zinc, titanium, zirconium, palladium, and combinations thereof; O is oxygen; a is the number of elements A; z is the charge of the element A; e is the charge of the polyoxometallate anion; x is 1 to 5; m is from 5 to 20; n is from 0 to 10; y is from 18 to 62; and a is 0 to 6.

In one embodiment of the present invention, X may be Si, P, Ge, or As, but may not be limited to, elements corresponding to group 14 or group 15 of the periodic table.

In one embodiment of the invention, the polyoxometallate is selected from the group consisting of H ₃ [PW ₁₂ O ₄₀ ], H ₅ [PW ₁₁ CoO ₃₉ ], H ₅ [PW ₁₁ ZnO ₃₉ ], H ₃ [PW ₁₁ FeO ₄₀ ] But are not limited to, those selected from the group consisting of combinations thereof, and the like.

In one embodiment of the invention, the polyoxometallate may be present in solution in the form of an anion represented as [X _x M ¹ _m M ² _{n y y} ] ^{e -} , but may not be limited thereto.

In one embodiment of the invention, the polyoxometallate is selected from the group consisting of H ₃ [PW ₁₂ O ₄₀ ], H ₅ [PW ₁₁ CoO ₃₉ ], H ₅ [PW ₁₁ ZnO ₃₉ ], or H ₃ [PW ₁₁ FeO ₄₀ ] Or in the form of anions such as PW ₁₂ O ₄₀ ^-3 , PW ₁₁ CoO ₃₉ ^-5 , PW ₁₁ ZnO ₃₉ ^-5, or PW ₁₁ FeO ₄₀ ^-5 , but may not be limited thereto.

In one embodiment of the present invention, when A in Formula 1 is absent, specifically, when a in Formula 1 is 0, the polyoxometallate is H _e [X _x M ¹ _m M ² _n O _y] may be, but may be represented as ^e-, not limited to this.

In one embodiment of the present invention, the polyoxometallate has a property of adhering well to the surface of the nanoparticles, so that the ZnO nanoparticles, TiO ₂ nanoparticles, or Al ₂ O ₃ And may be attached to the surface of the nanoparticles to change the properties of the nanoparticles, but the present invention is not limited thereto. For example, as the poloxomometalate is attached to the surface of the ZnO nanoparticles, both a Lewis acidic site and a weak Lewis basic site exist, and the properties of the ZnO nanoparticles May vary, but may not be limited thereto.

In one embodiment of the present invention, the polyoxometallate may be attached to or supported on the nanoparticles, but may not be limited thereto. For example, the polyoxometallate may be attached to the surface of the nanoparticles, but may not be limited thereto.

, The catalyst may exhibit higher activity compared to a catalyst that does not contain polyoxometallate due to the synergy between the polyoxometallate and the nanoparticles, .

In one embodiment of the present invention, the catalyst may be used in a reaction for producing cyclic carbonates by cyclization addition reaction of an alkylene oxide having 2 to 5 carbon atoms with CO ₂ , have. For example, the alkylene oxide may include, but is not limited to, ethylene oxide, propylene oxide and isomers thereof, butylene oxide and isomers thereof, or pentylene oxide and isomers thereof.

In one embodiment of the present invention, since the catalyst other than the reaction for producing the cyclic carbonates is used as a catalyst in various reactions through inherent acidity and oxidation-reduction properties, the polyoxometallate according to the present invention - Metal oxide catalysts can also be applied to various catalytic reactions.

In one embodiment of the present invention, the catalyst may exhibit a conversion rate of at least about 80% in the reaction for producing cyclic carbonates, but may not be limited thereto. For example, the conversion of the catalyst may be at least about 80%, at least about 85%, at least about 90%, at least about 95%, or at least about 97%.

In one embodiment of the present invention, dimethylaminopyridine (DMAP) may additionally be included as a cocatalyst, but may not be limited thereto. The dimethylaminopyridine is a substance having a Lewis basic property, for example, can act as a cocatalyst in the catalytic reaction through the polyoxometallate to produce the cyclic carbonate more effectively, but it is not limited thereto have.

In one embodiment of the present invention, the catalyst may be reusable, but it is not limited thereto. For example, the catalyst does not show a significant decrease in activity even after being used in the reaction, and thus may be reused several times, but it may not be limited thereto.

In one embodiment of the present invention, the ZnO nanoparticles may be monocrystalline, but the present invention is not limited thereto.

In one embodiment of the present invention, the ZnO nanoparticles are monocrystalline and may have, for example, wurtzite hexagonal structures, but are not limited thereto. For example, in the ZnO nanoparticles, the O ion of the ZnO nanoparticles may be located at a hexagonal site, and the Zn ion may have a Wurtzite hexagonal structure located at a tetrahedral interstitial site However, the present invention is not limited thereto.

The second aspect of the present invention is directed to a nanoparticle comprising ZnO nanoparticles, TiO ₂ nanoparticles, or Al ₂ O ₃ TiO ₂ nanoparticles or Al ₂ O ₃ nanoparticles by a solvothermal reaction by heating a mixture of a solution containing a precursor for producing nanoparticles and a solution containing polyoxometallate, There is provided a process for preparing a catalyst according to the first aspect of the present invention, which comprises obtaining a catalyst comprising nanoparticles and a polyoxometallate present on the surface of the nanoparticles.

In one embodiment of the present invention, the polyoxometallate may be represented by the following general formula (1), but is not limited thereto:

[Chemical Formula 1]

H _(e-az) A _a ^{z +} [X _x M ¹ _m M ² _n O _y ] ^e- ;

In Formula 1, H is hydrogen; A is an alkali metal element selected from Group 1 of the periodic table; X is an element selected from group 14 or group 15 of the periodic table; M ¹ is an element selected from the group consisting of molybdenum, vanadium, tungsten, niobium, tantalum, and combinations thereof; M ² is an element selected from the group consisting of cobalt, iron, zinc, titanium, zirconium, palladium, and combinations thereof; O is oxygen; a is the number of elements A; z is the charge of the element A; e is the charge of the polyoxometallate anion; x is 1 to 5; m is from 5 to 20; n is from 0 to 10; y is from 18 to 62; and a is 0 to 6.

In one embodiment of the present invention, the element corresponding to group 14 or group 15 of the periodic table may be Si, P, Ge, or As, but is not limited thereto.

In one embodiment of the invention, the polyoxometallate has a Keggin structure, a Dawson structure, and an Anderson structure, a Lindqvist structure, a Preysler structure, a Vick- But is not limited to, a structure selected from the group consisting of a large-wheel structure, a sandwich-type structure, and combinations thereof.

In one embodiment of the present invention, the polyoxometallate has a property of adhering well to the surface of the nanoparticles, so that the ZnO nanoparticles, TiO ₂ nanoparticles, or Al ₂ O ₃ The nanoparticles are attached to the surface to form ZnO nanoparticles, TiO ₂ nanoparticles, or Al ₂ O ₃ The nature of the nanoparticles can vary, but may not be limited thereto. For example, as the poloxomometalate is attached to the surface of the ZnO nanoparticles, both a Lewis acidic site and a weak Lewis basic site exist, so that the properties of the ZnO nanoparticles It can change.

In one embodiment of the present invention, the catalyst may be reusable, but it is not limited thereto. For example, the catalyst does not show a significant decrease in activity even after it has been used in the reaction, so it can be reused many times.

In one embodiment of the present invention, the ZnO nanoparticles may be monocrystalline, but the present invention is not limited thereto.

In one embodiment of the present invention, the ZnO nanoparticles are monocrystalline and may have, for example, wurtzite hexagonal structures, but are not limited thereto. For example, in the ZnO nanoparticles, the O ion of the ZnO nanoparticles is located in a hexagonal site, and the Zn ion has a Wurtzite hexagonal structure located in a tetrahedral interstitial site But may not be limited thereto.

In one embodiment of the invention, the step of heating the mixture may be performed at a temperature in the range of about 100 < 0 > C or higher, but may not be limited thereto. For example, the step of heating the mixture may include heating the mixture to a temperature of about 100 ° C or higher, about 100 ° C to about 500 ° C, about 100 ° C to about 400 ° C, about 100 ° C to about 300 ° C, From about 200 ° C to about 500 ° C, from about 200 ° C to about 400 ° C, from about 200 ° C to about 300 ° C, from about 300 ° C to about 500 ° C, from about 300 ° C to about 400 ° C, About 180 < 0 > C, or about 120 < 0 > C to about 180 < 0 > C.

In one embodiment of the invention, the polyoxometallate is selected from the group consisting of H ₃ [PW ₁₂ O ₄₀ ], H ₅ [PW ₁₁ CoO ₃₉ ], H ₅ [PW ₁₁ ZnO ₃₉ ], H ₃ [PW ₁₁ FeO ₄₀ ] But are not limited to, metals selected from the group consisting of combinations thereof, and the like.

In one embodiment of the invention, the polyoxometallate may be present in solution in the form of an anion represented as [X _x M ¹ _m M ² _{n y y} ] ^{e -} , but may not be limited thereto.

In one embodiment of the invention, the polyoxometallate is selected from the group consisting of H ₃ [PW ₁₂ O ₄₀ ], H ₅ [PW ₁₁ CoO ₃₉ ], H ₅ [PW ₁₁ ZnO ₃₉ ], or H ₃ [PW ₁₁ FeO ₄₀ ] Or in the form of anions such as PW ₁₂ O ₄₀ ^-3 , PW ₁₁ CoO ₃₉ ^-5 , PW ₁₁ ZnO ₃₉ ^-5, or PW ₁₁ FeO ₄₀ ^-5 , but may not be limited thereto.

In one embodiment of the present invention, when A in Formula 1 is absent, specifically, when a in Formula 1 is 0, the polyoxometallate is H _e [X _x M ¹ _m M ² _n O _y] may be, but may be represented as ^e-, not limited to this.

In one embodiment of the present invention, the mixture obtained by mixing the polyoxometallate-containing solution is heated and then centrifuged to precipitate ZnO nanoparticles, TiO ₂ nanoparticles, or Al ₂ O ₃ nanoparticles, The step of collecting the polyoxometallate present on the surface of the nanoparticles may further include but may not be limited thereto.

In one embodiment of the present invention, the step of washing ZnO nanoparticles, TiO ₂ nanoparticles, or Al ₂ O ₃ nanoparticles and polyoxometallate present on the surfaces of the nanoparticles collected through the centrifugation is added But may not be limited thereto. For example, the washing may be performed by water, an alcohol, an organic solvent or the like. Specifically, the washing may be performed using distilled water or ethanol, but the present invention is not limited thereto.

A third aspect of the invention is directed to a method of making a ZnO nanoparticle, TiO ₂ nanoparticle, or Al ₂ O ₃ A cyclic carbonate having 2 to 5 carbon atoms by the cyclization addition reaction of an alkylene oxide having 2 to 5 carbon atoms with CO ₂ in the presence of a nanoparticle and a catalyst containing polyoxometallate present on the surface of the nanoparticle Which comprises reacting a cyclic carbonate of formula Although the description of the method of manufacturing the cyclic carbonate according to the third aspect of the present application is omitted from the description of the parts overlapping with the first aspect of the present application, The same applies to the third aspect.

In one embodiment of the present invention, the amount of the catalyst for preparing the cyclic carbonates may be added in an amount of about 0.5 to about 10 wt% (wt%) based on the alkylene oxide, but may not be limited thereto. For example, the amount of catalyst for preparing the cyclic carbonates may range from about 0.5 to about 10, from about 0.5 to about 8, from about 0.5 to about 6, from about 0.5 to about 4, or from about 0.5 to about 10, (Wt%), based on the total weight of the composition.

In one embodiment of the present invention, as the amount of the catalyst increases, the reaction rate of generation of the cyclic carbonates may increase, but the present invention is not limited thereto.

In one embodiment of the present invention, the cyclization addition reaction may be performed in a temperature range of about 100 캜 or higher, but may not be limited thereto. For example, the cyclization addition reaction may be carried out at a temperature of about 100 占 폚 or higher, about 100 占 폚 to about 500 占 폚, about 100 占 폚 to about 400 占 폚, about 100 占 폚 to about 300 占 폚, About 300 ° C to about 500 ° C, about 200 ° C to about 400 ° C, about 200 ° C to about 300 ° C, about 300 ° C to about 500 ° C, about 300 ° C to about 400 ° C, 180 < 0 > C, or from about 120 < 0 > C to about 180 < 0 > C.

In one embodiment of the present invention, the cyclization addition reaction may be performed in a pressure range greater than atmospheric pressure, i.e., atmospheric pressure (about 0.1013 MPa), but may not be limited thereto. For example, the pressure range of the cyclization addition reaction can be freely adjusted if it is within the pressure range in which the reactor in which the reaction takes place can be freely controlled. The range can be atmospheric pressure (about 0.1013 MPa) To more than 5 MPa, from more than normal pressure to about 4 MPa, or from atmospheric pressure to about 3 MPa.

In one embodiment of the present invention, the catalyst may be, but not limited to, additionally containing dimethylaminopyridine (DMAP) as a cocatalyst. For example, because of the synergistic effect of the polyoxometallate with the nanoparticles, the catalyst exhibits higher activity compared to a catalyst that does not contain polyoxometallate in the presence of dimethylaminopyridine as a cocatalyst But may not be limited thereto. For example, the dimethylaminopyridine is a substance having Lewis basicity, and can act as a cocatalyst in the catalytic reaction through the polyoxometallate to produce the cyclic carbonates more effectively, but is not limited thereto .

In one embodiment of the present invention, the catalyst may exhibit a conversion rate of at least about 80% in the reaction for producing cyclic carbonates, but may not be limited thereto. For example, the conversion of the catalyst may be at least about 80%, at least about 85%, at least about 90%, at least about 95%, or at least about 97%.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the following examples are given to aid understanding of the present invention, and the present invention is not limited to the following examples.

[ Example ]

material

Zinc acetate dehydrate, phosphotungstic acid hydrate (H ₃ PW ₁₂ O ₄₀ .nH ₂ O), propylene oxide, and 4- (dimethylamino) pyridine were purchased from Sigma-Aldrich . Methanol was purchased from JT Baker. Dichloromethane was purchased from Junsei. All reagents were used as purchased without further purification. Ultrapure Millipore water (18.2 M) was used in the preparation of aqueous solutions. H _x [PW ₁₁ MO ₃₉ ] .nH ₂ O (M = Co, Fe, Zn) can be prepared by the method described in Tourne, CM, Tourne, GF, Malik, SA, and Weakley, TJR Triheteropolyanions containing copper ), or manganese (III) J. Inorg. Nucl. Chem. 1970, 32, 3875). 9.1 mmol of Na ₂ HPO ₄ , 100 mmol of Na ₂ WO ₄ and 12 mmol of nitrate of M (M = Co, Fe, Zn) were mixed in 200 mL of water and the pH was adjusted to 4.8.

Polyoxometallate - ZnO  The catalyst (POM- ZnO  Catalyst)

In a typical procedure, 0.25 g of Zn (CH ₃ COO) ₂ .2H ₂ O was added to 20 mL of 1.0 × 10 ³ mol / L POMs methanol solution under magnetic stirring. After several minutes, the mixture was transferred to a Teflon-lined stainless steel autoclave and heated in a forced convection air oven at 130 ° C for 6 hours and then cooled to room temperature naturally. The precipitate was collected by centrifugation, washed with distilled water and ethanol, and then dried at 60 DEG C for 6 hours.

Character analysis

A scanning electron microscope (SEM) image of the polyoxometallate-ZnO catalysts was obtained using a field-emission scanning electron microscope (FEI Magellan 400). Transmission electron microscopy (TEM) images were obtained on a Phillips Model Tecnai F20 transmission electron microscope at 200 kV after disposing droplets of the hydrosol on a carbon-coated copper grid (200 mesh). High-angle annular dark-field scanning TEM (TEM) and energy-dispersive X-ray spectroscopy (EDS) analyzes were performed on the FEI Tecnai G2 F30 Super-Twin transmission operating at 300 kV Electron microscope. The composition of the catalysts was determined by inductively coupled plasma-atomic emission spectroscopy (ICP-AES, OPTIMA 3300DV).

CO ₂  Conversion reaction process

The cyclization addition of CO ₂ to propylene oxide was carried out in a stainless steel-steel autoclave (internal volume 20 cm ³ ). A typical reaction was carried out as shown in Scheme 1 below. In the autoclave, CO ₂ was treated with propylene oxide (1 cm ³ ), DMF (1 cm ³ ), DMAP (0.17 mol%) and the polyoxometallate-ZnO catalyst (1.8 wt% Lt; / RTI > The autoclave was then heated to 160 DEG C and its pressure was adjusted to 3.5 MPa. After the reaction had proceeded at a pressure of 3.5 MPa for 6 hours, the autoclave was cooled and the reaction product was analyzed by NMR.

[Reaction Scheme 1]

The polyoxometallate-ZnO catalyst (POM-ZnO catalyst) is prepared by solvothermal treatment of a mixed solution of Zn (CH ₃ COO) ₂ .2H ₂ O, CH ₃ OH, and POMs at 160 ° C., . The authors of the present invention altered the four different substituted-POMs without any change in the reaction conditions. Or _{less, PW 12 O 40 (POM)} , PW 11 CoO 39 (Co-POM), PW 11 FeO 40 (Fe-POM) and PW ₁₁ ZnO ₃₉ to the ZnO catalyst prepared from the POMs (Zn-POM) each POM- ZnO catalyst, Co-POM-ZnO catalyst, Fe-POM-ZnO catalyst and Zn-POM-ZnO catalyst.

1 shows the X-ray diffraction patterns of the obtained powders (POM-ZnO (a), Co-POM-ZnO (b), Fe-POM-ZnO (c), and Zn- . All the diffraction peaks in the obtained spectrum agree well with the diffraction peaks of ZnO (space group: P63mc; JCPDS card no. 36-1451), indicating that the powder obtained is monocrystalline and has wurtzite hexagonal structures ). No characteristic peaks of other impurities were detected.

2 shows SEM and TEM images of the POM-ZnO catalyst (a), the Co-POM-ZnO catalyst (b), the Fe-POM-ZnO catalyst (c), and the Zn-POM-ZnO (d) catalyst. The obtained ZnO catalyst with an aggregate is formed of nano-sized crystals.

Figure 3 shows the results of a high-angle annular-field-scanning TEM (HAADF) analysis of Zn and W [(a) and (d)], Zn, Co and W (b), Zn, Fe and W -STEM) image and corresponding point energy-dispersive X-ray spectroscopy (EDS) data. The relative compositions of Zn and W in the POM-ZnO catalyst, Co-POM-ZnO catalyst, Fe-POM-ZnO catalyst and Zn-POM-ZnO catalyst were 87.9: 12.1, 90.3: 9.7, 93.1 : 6.9, and 93: 7, respectively.

A comparison of the FT-IR spectra of the POM-ZnO catalyst with the spectra of pristine POMs further indicated that the POMs were present on the catalyst surface while maintaining their Keggin structure after the reaction (FIG. 4). 4, the four vibration peaks located at 1100 cm ^-1 to 800 cm ^-1 are the tetrahedral PO bond, the terminal W = O bond, and the two types of bridging WOW bond stretching of the cluster It originated from stretching vibration.

The improved catalytic activities were due to the control of the interaction between the ZnO surface and the reaction enabled by the ligands. In this regard, catalytic activity and recyclability of the POM-Zn catalyst for the preparation of the cyclic carbonate from epoxide and CO ₂ have been investigated. The results were compared with commercial ZnO catalysts to study the effect of the POMs on the catalytic performance of ZnO catalysts for chemical reactions. The cyclic carbonate yield for the coupling reaction between CO ₂ and propylene using 1.8 wt% catalyst at 160 ° C for 2 hours was obtained by measuring the amount of product relative to the amount of propyl carbonate (FIG. 5).

As shown in Table 1 below, the commercial ZnO catalyst switched only 3%, while the 99, 99, 97, and 97% conversion of the product was POM-ZnO catalyst, Co-POM-ZnO catalyst, Fe-POM -ZnO catalyst and a Zn-POM-ZnO catalyst. This result can be attributed to the improved surface Lewis acidity afforded by the POMs, which is due to the activation of the epoxide by the Lewis acid, the opening of the epoxide ring, the insertion of carbon dioxide, Thereby promoting the closure of the cyclic carbonate.

^a reaction conditions: propylene oxide (1 cm ³ ), CH ₂ Cl ₂ (1 cm ³ ), DMAP (0.17 mol%), catalyst (1.8 wt%), reaction time 2 hours. ^b Based on ¹ H NMR analysis of reaction mixture aliquot.

To confirm the circulation of the POM-ZnO catalyst, the circulated catalyst was applied for successive second and third catalytic reaction runs after the addition of fresh reagents containing DMAP. Interestingly, the conversion is still maintained after the third catalytic reaction run (Table 2). This indicates that the POM-ZnO catalyst can be circulated without significant loss in their activity. In the catalyzed reaction, leaching of the catalyst is a major cause of the degradation of the efficiency of the catalyst.

Reaction conditions of the catalyst: propylene oxide (1 cm ³ ), CH ₂ Cl ₂ (1 cm ³ ), DMAP (0.17 mol%), catalyst (1.8 wt%). Based on ¹ H NMR analysis of reaction mixture aliquot. The values in Table 2 represent the net exchange rate (%).

In summary, various m-POM-ZnO catalysts have been prepared herein through an easy one-pot solvent heating method. It has been found that POM-ZnO catalysts exhibit excellent catalytic activity and reusability, as evaluated as catalysts for the production of cyclic carbonates from epoxides and CO ₂ .

It will be understood by those of ordinary skill in the art that the foregoing description of the embodiments is for illustrative purposes and that those skilled in the art can easily modify the invention without departing from the spirit or essential characteristics thereof. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. For example, each component described as a single entity may be distributed and implemented, and components described as being distributed may also be implemented in a combined form.

The scope of the present invention is defined by the appended claims rather than the detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included within the scope of the present invention.

Claims (14)

ZnO nanoparticles, TiO ₂ nanoparticles, or Al ₂ O ₃ nanoparticles and a polyoxometallate present on the surface of the nanoparticles.
The method according to claim 1,
Wherein the polyoxometalate is represented by the following Formula 1:
[Chemical Formula 1]
H _(e-az) A _a ^{z +} [X _x M ¹ _m M ² _n O _y ] ^e- ;
In Formula 1,
H is hydrogen;
A is an alkali metal element selected from Group 1 of the periodic table;
X is an element selected from group 14 or group 15 of the periodic table;
M ¹ is an element selected from the group consisting of molybdenum, vanadium, tungsten, niobium, tantalum, and combinations thereof;
M ² is an element selected from the group consisting of cobalt, iron, zinc, titanium, zirconium, palladium, and combinations thereof;
O is oxygen;
a is the number of elements A; z is the charge of the element A; e is the charge of the polyoxometallate anion;
x is 1 to 5; m is from 5 to 20; n is from 0 to 10; y is from 18 to 62; and a is 0 to 6.
The method according to claim 1,
Wherein the polyoxometallate is selected from the group consisting of H ₃ [PW ₁₂ O ₄₀ ], H ₅ [PW ₁₁ CoO ₃₉ ], H ₅ [PW ₁₁ ZnO ₃₉ ], H ₃ [PW ₁₁ FeO ₄₀ ] ≪ / RTI >
The method according to claim 1,
Wherein the catalyst is used in a reaction for producing cyclic carbonates by the cyclization addition reaction of an alkylene oxide having 2 to 5 carbon atoms and CO ₂ .
The method according to claim 1,
And further comprising dimethylaminopyridine (DMAP) as a cocatalyst.
The method according to claim 1,
Wherein the catalyst is reusable.
The method according to claim 1,
Wherein the ZnO nanoparticles are monocrystalline.
ZnO nanoparticles, TiO ₂ nanoparticles, or Al ₂ O ₃ A mixture of a solution containing a precursor for producing nanoparticles and a solution containing a polyoxometallate is heated by a solvent thermal reaction to form a ZnO nanoparticle, TiO ₂ nanoparticle, or Al ₂ O ₃ 8. A process for producing a catalyst according to any one of claims 1 to 7, comprising obtaining a catalyst comprising nanoparticles and a polyoxometallate present on the surface of the nanoparticles.
9. The method of claim 8,
Wherein the polyoxometallate is represented by the following formula (1): < EMI ID =
[Chemical Formula 1]
H _(e-az) A _a ^{z +} [X _x M ¹ _m M ² _n O _y ] ^e- ;
In Formula 1,
H is hydrogen;
A is an alkali metal element selected from Group 1 of the periodic table;
X is an element selected from group 14 or group 15 of the periodic table;
M ¹ is an element selected from the group consisting of molybdenum, vanadium, tungsten, niobium, tantalum, and combinations thereof;
M ² is an element selected from the group consisting of cobalt, iron, zinc, titanium, zirconium, palladium, and combinations thereof;
O is oxygen;
a is the number of elements A; z is the charge of the element A; e is the charge of the polyoxometallate anion;
x is 1 to 5; m is from 5 to 20; n is from 0 to 10; y is from 18 to 62; and a is 0 to 6.
9. The method of claim 8,
Wherein the step of heating the mixture is carried out in a temperature range of 100 DEG C or higher.
9. The method of claim 8,
The polyoxometallate is a group consisting of H ₃ [PW ₁₂ O ₄₀ ], H ₅ [PW ₁₁ CoO ₃₉ ], H ₅ [PW ₁₁ ZnO ₃₉ ], H ₃ [PW ₁₁ FeO ₄₀ ] ≪ / RTI > and a metal selected from the group consisting of:
A nanoparticle comprising a ZnO nanoparticle, a TiO ₂ nanoparticle, or an Al ₂ O ₃ nanoparticle according to any one of claims 1 to 7 A cyclic carbonate having 2 to 5 carbon atoms by the cyclization addition reaction of an alkylene oxide having 2 to 5 carbon atoms with CO ₂ in the presence of a nanoparticle and a catalyst containing polyoxometallate present on the surface of the nanoparticle Or a mixture thereof.
13. The method of claim 12,
Wherein the cyclization addition reaction is carried out in a temperature range of 100 占 폚 or more.
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