Bifunctional catalyst for synthesizing carbonic ester as well as preparation method and application of bifunctional catalyst

Abstract

The invention discloses a bifunctional catalyst for synthesizing carbonic ester as well as a preparation method and application of the bifunctional catalyst, and the catalyst comprises the following components: (1) VIII B group metal active components; (2) a group IIIB metal auxiliary agent; and (3) modifying the carrier. Wherein the VIII B group metal active component comprises a compound of one or more metal elements of Fe, Co, Ni, Ru, Rh, Pd and Pt; the metal additive comprises a compound of one or more metal elements of Sc, Y, La, Ce and Nd. The catalyst prepared by the method has good catalytic activity and product selectivity, and has good stability in a long-period operation process. While catalyzing the main reaction to generate carbonic ester, the catalyst prepared by the invention can be used for efficiently decarbonylating and converting halogenated ester into halogenated alkane, so that the problem of corrosion of halogenated ester to equipment is solved.

Description

Technical Field

[0001] The present invention relates to the field of preparing carbonates by reacting nitrites and carbon monoxide in the presence of a catalyst, and specifically to a bifunctional catalyst for synthesizing carbonates, a preparation method and an application thereof. On the one hand, the catalyst can catalyze the main reaction to prepare carbonates; on the other hand, it can also catalyze the decarbonylation reaction of a stabilizer halide intermediate product halogenated ester to generate halogenated alkanes. Background Art

[0002] Methods for preparing carbonates include methanol carbonylation, phosgene, transesterification and carbon dioxide methods. The methanol carbonylation method includes gas phase and liquid phase methods. Among them, the phosgene method has the problem of high raw material toxicity, the transesterification method and the carbon dioxide method have the problems of high raw material cost and low reaction efficiency. The gas phase carbonylation method has many advantages due to its low raw material cost and mild reaction, and has attracted much attention from experts and scholars at home and abroad. The gas phase carbonylation method involves the process of preparing carbonates by reacting nitrite and carbon monoxide. The reaction process is a gas-solid reaction, and the catalyst used faces the problems of low activity and poor stability. Therefore, in recent years, experts and scholars at home and abroad have been committed to developing highly active and long-life catalysts to maximize the advantages of this process.

[0003] Patent CN111420675B discloses a catalyst with a carrier modified by a VIB group element, a palladium active component and a transition metal additive. During the reaction, 50-300 ppm of hydrogen chloride needs to be supplemented. The catalyst can show good stability after continuous operation for more than 500 hours. Patent CN111760580A discloses a Pd-Cu-Ce / lithium aluminum catalyst system. During the reaction, 50-500 ppm of hydrogen chloride needs to be supplemented. The stability is good during 1000 hours of continuous operation.

[0004] Halides can improve the stability of catalysts as stabilizers, but as the main reaction proceeds, halides will react to generate halogenated esters. Due to their strong corrosiveness, halogenated esters will cause serious corrosion to the system after long-term operation, which will cause property losses and pose major safety hazards. Efficient decarbonization and conversion into halogenated alkanes is the key to solving the above corrosion problem. In recent years, there have been many studies on carbonylation catalysts. How to solve the corrosion problem caused by stabilizers while ensuring the stability of the catalyst is a key technical difficulty that needs to be solved in this field. Summary of the invention

[0005] To solve the above problems, an object of the present invention is to provide a catalyst and a preparation method for the carbonylation reaction of nitrite and carbon monoxide to prepare carbonate. The catalyst of the present invention has good catalytic activity and product selectivity under the action of a halide stabilizer and has good stability during long-term operation. While efficiently catalyzing the main reaction to generate carbonate, the catalyst of the present invention can also efficiently decarbonylate the haloester generated by the stabilizer into haloalkane, solving the corrosion problem of the equipment caused by the haloester.

[0006] Another object of the present invention is to provide a method for preparing carbonate by catalytic carbonylation reaction of nitrite and carbon monoxide using the catalyst. The catalyst has excellent catalytic activity and stability when applied to the carbonylation reaction.

[0007] To achieve the above object, the present invention adopts the following solutions.

[0008] In the first aspect, the present invention provides a bifunctional catalyst for synthesizing carbonate, which comprises the following components:

[0009] (1) The active component of Group VIIIB metal;

[0010] (2) The metal promoter of Group IIIB;

[0011] (3) The modified carrier;

[0012] Among them, the active component of Group VIIIB metal in component (1) is selected from compounds containing one or more metal elements among Fe, Co, Ni, Ru, Rh, Pd and Pt.

[0013] The metal promoter of Group IIIB in component (2) is selected from compounds containing one or more metal elements among Sc, Y, La, Ce and Nd.

[0014] In the present invention, the forms of existence of the active component of Group VIIIB metal in step 1) and the metal promoter of Group IIIB in component (2) are related to the raw materials. For example, they exist in the form of corresponding metal salts, and the salts are selected from one or more of nitrates, halides and metal complexes, preferably nitrates and / or halides, more preferably halides.

[0015] The modified carrier in component (3) is a carrier containing a modifier, and the modifier is selected from one or more metal elements among Rb, Cs, Fr, Be, Sr, Ba and Ra, and the modifier exists in the form of an oxide.

[0016] In the present invention, the carrier in component (3) is selected from one or more of silica, alumina, activated carbon, diamond, spinel and molecular sieve.

[0017] In the present invention, based on the total mass of the catalyst, the Group VIIIB metal active component of component (1) is calculated as a compound and has a content of 0.1-10 wt%, such as 0.1, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 wt%, preferably 0.1-5 wt%; the Group IIIB metal promoter of component (2) is calculated as a compound and has a content of 0.1-10 wt%, such as 0.1, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 wt%, preferably 0.1-5 wt%; the balance is component (3) the modified carrier, totaling 100 wt%.

[0018] In the present invention, for the modified carrier of component (3), the modifier is calculated as a metal element and has a content of 0.1-10 wt%, such as 0.1, 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 wt%, preferably 0.1-5 wt%, based on the total mass of the modified carrier.

[0019] In the present invention, the modified carrier of component (3) is a carrier containing a modifier, and its modification method can adopt the conventional methods known in the art. There are no special requirements in the present invention. For example, in a specific example method a), the modifier can be blended with the conventional preparation raw materials of the carrier and prepared by integral molding; in another specific example method b), it can also be prepared by impregnating the carrier in a modifier solution; specifically, the examples are as follows:

[0020] The steps of method a) include: during the conventional carrier molding process, dissolving the salt containing the modifier in water, fully mixing it with the carrier raw material slurry according to the ratio and then molding, and calcining at a suitable temperature to obtain the carrier containing the modifier;

[0021] The steps of method b) include: dissolving the salt containing the modifier in water, mixing it with the unmodified carrier for equal-volume impregnation, and calcining at a suitable temperature to obtain the carrier containing the modifier.

[0022] The above methods a) and b) are both conventional modification methods in the art. The specific processes and operation parameters are not specifically limited in the present invention. Those skilled in the art can calculate and screen based on the prior art according to actual needs to achieve the loading of the modifier on the carrier and reach the required content. The conventional carrier molding process in method a) refers to the preparation process of the unmodified carrier disclosed in the prior art, and the modifier can be directly added to its preparation raw materials according to the content defined in the present invention; in method b), the modifier is dissolved in water according to the content defined in the present invention and then mixed with the unmodified carrier for equal-volume impregnation; preferably, in methods a) and b), by controlling the ratio of each raw material, a modified carrier with a modifier content of 0.1-10 wt% calculated as a metal element (based on the total mass of the modified carrier) is prepared;

[0023] Preferably, the calcination temperature in methods a) and b) is 500 - 1000 °C, such as 500, 600, 700, 800, 900, 1000 °C, preferably 600 - 800 °C; the calcination time is 1 - 10 h, such as 1, 3, 5, 7, 9, 10 h;

[0024] Preferably, the salt containing the modifier in methods a) and b) is selected from one or more of the nitrates, carbonates, and organometallic salts of the metal corresponding to the modifier, preferably one or more of the nitrates and carbonates of the metal, more preferably the nitrates of the metal.

[0025] In a second aspect, the present invention also provides a preparation method of the above bifunctional catalyst for synthesizing carbonates. This preparation method is only an exemplary illustration of the source mode of the polyisocyanate composition product with the above characteristics of the present invention, but does not constitute any limitation.

[0026] Exemplarily, the present invention provides a preparation method of the above bifunctional catalyst for synthesizing carbonates, comprising the following steps:

[0027] 1) Dissolve the precursor of the Group VIII metal in component (1) and the precursor of the Group IIIB metal in component (2) in an aqueous solvent to obtain an impregnation solution;

[0028] 2) Mix the impregnation solution obtained in step 1) with a modified support for impregnation. After impregnation, the support is dried and calcined to obtain a bifunctional catalyst for synthesizing carbonates.

[0029] In the present invention, the precursor of the Group VIII metal in component (1) and the precursor of the Group IIIB metal in component (2) in step 1) are selected from salts of the corresponding metals. Among them, the salts are selected from one or more of nitrates, halides, and metal complexes, preferably nitrates and / or halides, more preferably halides.

[0030] In the present invention, the aqueous solvent in step 1) is selected from at least one of water, hydrochloric acid, aqueous sodium hydroxide solution, and aqueous ammonia solution;

[0031] Preferably, for the aqueous solvent, the water content is 10 - 100 wt%, such as 10, 30, 50, 70, 90, 100 wt%;

[0032] Specifically, the present invention does not require whether to select water, hydrochloric acid, sodium hydroxide, or aqueous ammonia solution, nor is there any special requirement for the dissolution temperature and dissolution time, as long as the dissolution purpose is achieved and a homogeneous phase is formed;

[0033] Impregnating solution preparation: Dissolve the precursors of Group VIII metals described in component (1), the salts corresponding to the metal active component and the metal promoter in an aqueous solution of water, hydrochloric acid, sodium hydroxide or ammonia; there is no specific requirement for whether the solution is an aqueous solution of water, hydrochloric acid, sodium hydroxide or ammonia.

[0034] In the present invention, for the impregnating solution in step 1), based on its total mass being 100%, it contains the precursor of Group VIII metals described in component (1) = the content is 0.1 - 8.0 wt%, such as 0.1, 0.5, 1, 2, 3, 4, 5, 6, 7, 8 wt%, and the content of the precursor of Group IIIB metals described in component (2) is 0.1 - 8.0 wt%, such as 0.1, 0.5, 1, 2, 3, 4, 5, 6, 7, 8 wt%.

[0035] In the present invention, for the impregnation in step 2), there are no special requirements for the impregnation temperature, time and method, as long as the active component is uniformly loaded on the carrier;

[0036] Preferably, the impregnating solution is mixed with the modified carrier for impregnation, and the mass ratio of the impregnating solution to the modified carrier is 0.5 - 1:1; more preferably, in step 2), the impregnating solution and the modified carrier are mixed according to the equal - volume impregnation ratio;

[0037] Preferably, for the impregnation, the temperature is 0 - 50 °C, such as 0, 10, 20, 30, 40, 50 °C, and the time is 0.5 - 10 h, such as 0.5, 2, 4, 6, 8, 10 h.

[0038] In the present invention, for the drying and calcination of the carrier after impregnation in step 2), it is a conventional operation method in the field, and there are no special requirements in the present invention. For example, the drying temperature is preferably 100 - 150 °C, such as 100, 110, 120, 130, 140, 150 °C, the drying time is not required, and the water content is controlled to be less than 20 wt%, such as 19, 17, 15, 10, 5, 1 wt% etc., preferably less than 10 wt% before calcination; the calcination temperature is preferably 150 - 300 °C, such as 150, 180, 210, 240, 270, 300 °C, and the calcination time is preferably 1 - 10 h, such as 1, 3, 5, 7, 9, 10 h.

[0039] The catalyst prepared by the above - mentioned method according to the present invention, under the action of a stabilizer, has good catalytic activity and product selectivity, and good stability during long - term operation. While catalyzing the main reaction to produce carbonate, it can also efficiently decarbonylate the halogenated ester to convert it into a halogenated alkane, solving the corrosion problem of the equipment caused by the halogenated ester.

[0040] In the third aspect, the present invention also provides the application of the above - mentioned catalyst in the field of synthesizing carbonate, reacting nitrite and carbon monoxide in the presence of the catalyst to prepare carbonate.

[0041] Exemplarily, a method for preparing a carbonate, the steps comprising:

[0042] In the presence of the bifunctional catalyst for synthesizing a carbonate, using nitrite and carbon monoxide as raw materials and a halide as a stabilizer, reacting to prepare a carbonate.

[0043] In the present invention, the nitrite is at least one of nitrites containing C1-C4 alkyl groups, preferably at least one of nitrites containing C1-C2 alkyl groups;

[0044] Preferably, the nitrite is selected from at least one of methyl nitrite and ethyl nitrite.

[0045] In the present invention, the molar ratio of the nitrite to carbon monoxide is 10:1 - 1:10, such as 10:1, 7:1, 4:1, 1:1, 1:4, 1:7, 1:10, preferably 2:1 - 1:2.

[0046] In the present invention, the halide is selected from at least one of hydrogen halides and haloalkanes, preferably at least one of chlorides, fluorides, and bromides;

[0047] Preferably, the molar ratio of the halide to the carbon monoxide feed is 1 / 10 - 1 / 10000, such as 1 / 10, 1 / 100, 1 / 500, 1 / 1000, 1 / 3000, 1 / 5000, 1 / 8000, 1 / 10000, preferably 1 / 100 - 1 / 5000.

[0048] In the present invention, when the nitrite and carbon monoxide are fed, their volume concentrations in the reactor are both controlled at 1 - 30%, such as 1, 5, 10, 15, 20, 25, 30%, preferably 10 - 25%, and the rest is balanced with inert components;

[0049] The inert components include but are not limited to nitrogen, carbon dioxide, etc.

[0050] In the present invention, for the reaction, the temperature is 30 - 250°C, such as 30, 50, 100, 150, 200, 250°C, preferably 80 - 180°C; the reaction pressure is 0 - 2 MPa, such as 0, 0.5, 1, 1.5, 2 MPa, preferably 0.5 - 1 MPa;

[0051] Preferably, for the reaction, the space velocity is controlled at 500 - 8000 h -1 , such as 500, 1000, 2000, 3000, 4000, 5000, 6000, 7000, 8000 h -1 , preferably 1000 - 5000 h -1 ;

[0052] In the present invention, the reaction is carried out in a fixed bed or a fluidized bed, preferably a fixed bed.

[0053] In the method of the present invention, the selectivity of the carbonate reaches 97.5%, and the conversion rate of the haloester reaches 99.9%.

[0054] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0055] According to the catalyst of the present invention, under the action of a stabilizer, it has good catalytic activity and product selectivity, and good stability during long-term operation. While catalyzing the main reaction to produce carbonate, the catalyst prepared in the present invention can efficiently decarbonylate the haloester to convert it into a haloalkane, solving the corrosion problem of the equipment caused by the haloester.

[0056] Specific implementation method

[0057] The following examples further illustrate the preferred specific implementation schemes within the scope of the present invention. These examples are merely illustrative and do not limit the scope of the present invention. The purpose of the following examples is to further introduce and display the specific implementation schemes within the scope of the present invention. Therefore, the examples should be understood as only used to more specifically display the present invention, and do not limit the content of the present invention in any way.

[0058] In each example and comparative example of the present invention, the sources of the main raw materials are as follows. Without special instructions, other raw materials and reagents are obtained through commercially available channels:

[0059] RbNO3: Aladdin, R103758;

[0060] NiCl2: Aladdin, N433839;

[0061] LaCl3: Aladdin, L189069;

[0062] CsNO3: Aladdin, C434119;

[0063] PdCl2: Aladdin, P579112;

[0064] ScCl3: Aladdin, S137956;

[0065] BaNO3: Aladdin, B118663;

[0066] PtCl2: Aladdin, P431115;

[0067] CeCl3: Aladdin, C196218;

[0068] NaCl: Aladdin, S433743;

[0069] CuCl2: Aladdin, C106775;

[0070] KNO3: Aladdin, P111645;

[0071] Al2O3: Aladdin, A399398;

[0072] SiO2: Aladdin, S118568;

[0073] Activated carbon: Aladdin, C112240.

[0074] The test parameters and corresponding test methods in each example and comparative example of the present invention are as follows:

[0075] The metal content of the catalyst was quantitatively analyzed by inductively coupled plasma optical emission spectrometer (ICP-OES).

[0076] The reaction solution and the composition of the outlet gas phase were analyzed by gas chromatography GC-2014. The space-time yield of the catalyst, i.e., the STY value, was calculated by formula (1) to compare the activity of the catalyst; the selectivity of each product was calculated by formula (2); the conversion rate of the haloester was calculated by formula (3).

[0077] (1) STY (g·L -1 ·h -1 ) = amount of main product generated g / catalyst volume L / time h;

[0078] (2) Selectivity % = amount of reactant consumed to produce the target product mol / amount of reactant participating in the reaction mol * 100.

[0079] (3) Haloester conversion rate % = amount of haloalkane at the outlet mol / total amount of haloester mol (calculated based on complete conversion of the halide to the haloester) * 100

[0080] Example 1

[0081] Preparation of modified support 1:

[0082] Dissolve 0.75 g of RbNO3 in 18 g of water to form a homogeneous solution. According to the equal-volume impregnation method, add 30 g of alumina to the above solution. After impregnation for 1 h, dry the moisture and calcine at 700 °C for 5 h to prepare modified support 1, where the content of the modifier Rb is 1.43 wt%, based on the total mass of the modified support.

[0083] Preparation of bifunctional catalyst 1 for synthesizing carbonate:

[0084] 1) Add 0.625 g of NiCl2 and 0.625 g of LaCl3 to 12.5 g of water to form a homogeneous impregnation solution.

[0085] 2) In the equal-volume impregnation method, 25 g of modified support 1 was added to the above impregnation solution. After impregnation for 1 h, it was dried at 120 °C for 5 h to control the water content below 5 wt%, and then calcined at 200 °C for 5 h to obtain catalyst 1, where the NiCl2 content was 2.5 wt% and the LaCl3 content was 2.5 wt%.

[0086] Example 2

[0087] Preparation of modified support 2:

[0088] 0.15 g of CsNO3 was dissolved in 21 g of water to form a homogeneous solution. In the equal-volume impregnation method, 30 g of silica was added to the above solution. After impregnation for 1 h, the water was dried, and then calcined at 600 °C for 2 h to obtain modified support 2, where the modifier Cs content was 0.34 wt% based on the total mass of the modified support.

[0089] Preparation of bifunctional catalyst 2 for synthesizing carbonate:

[0090] 1) 0.125 g of PdCl2 and 0.125 g of ScCl3 were added to 16.25 g of water to form a homogeneous impregnation solution.

[0091] 2) In the equal-volume impregnation method, 25 g of modified support 2 was added to the above impregnation solution. After impregnation for 1 h, it was dried at 100 °C for 2 h to control the water content below 10 wt%, and then calcined at 150 °C for 2 h to obtain catalyst 2, where the PdCl2 content was 0.5 wt% and the ScCl3 content was 0.5 wt%.

[0092] Example 3

[0093] Preparation of modified support 3:

[0094] 1.5 g of BaNO3 was dissolved in 27 g of water to form a homogeneous solution. In the equal-volume impregnation method, 30 g of activated carbon was added to the above solution. After impregnation for 1 h, the water was dried, and then calcined at 800 °C for 8 h to obtain modified support 3, where the modifier Ba content was 2.56 wt% based on the total mass of the modified support.

[0095] Preparation of bifunctional catalyst 3 for synthesizing carbonate:

[0096] 1) 1.25 g of PtCl2 and 1.25 g of CeCl3 were added to 20.75 g of water to form a homogeneous impregnation solution.

[0097] 2) In accordance with the equal-volume impregnation method, add 25 g of modified support 3 to the above impregnation solution. After impregnation for 1 h, dry it at 150 °C for 8 h to control the water content below 1 wt%, and then calcine it at 300 °C for 8 h to prepare catalyst 3, where the PtCl2 content is 5 wt% and the CeCl3 content is 5 wt%.

[0098] Comparative Example 1

[0099] Prepare modified support 4:

[0100] Calcine 30 g of alumina at 700 °C for 5 h to prepare support 4.

[0101] Preparation of catalyst 4:

[0102] Refer to the method of Example 1, with the difference that: replace it with an equal amount of support 4, and then prepare catalyst 4 according to the same method as in Example 1.

[0103] Comparative Example 2

[0104] Preparation of catalyst 5:

[0105] Refer to the method of Example 1, with the difference that: do not add LaCl3 to the impregnation solution, and then prepare catalyst 5 according to the same method as in Example 1.

[0106] Comparative Example 3

[0107] Preparation of catalyst 6: Refer to the method of Example 1, with the difference that: replace LaCl3 in the impregnation solution with an equal amount of NaCl, and then prepare catalyst 6 according to the same method as in Example 1.

[0108] Comparative Example 4

[0109] Preparation of catalyst 7: Refer to the method of Example 1, with the difference that: do not add NiCl2 to the impregnation solution, and then prepare catalyst 7 according to the same method as in Example 1.

[0110] Comparative Example 5

[0111] Preparation of catalyst 8: Refer to the method of Example 1, with the difference that: replace NiCl2 in the impregnation solution with an equal amount of CuCl2, and then prepare catalyst 8 according to the same method as in Example 1.

[0112] Comparative Example 6

[0113] Prepare modified support: Refer to the method of Example 1, with the difference that: replace RbNO3 with an equal amount of KNO3, and then prepare the support according to the same method as in Example 1.

[0114] Preparation of Catalyst 9: Refer to the method of Example 1, with the only difference being that the carrier of this comparative example is used, and then according to the same method as in Example 1, Catalyst 9 is prepared.

[0115] Example 4

[0116] Measure 20 ml of the catalysts prepared in the above examples and comparative examples respectively. In a fixed-bed reactor, control the feeding concentrations of methyl nitrite and CO to be 12% respectively (the rest is balanced with nitrogen), the molar ratio of hydrogen chloride to carbon monoxide in the feed is 1 / 3000, the reaction temperature is 130 °C, the reaction pressure is 0.8 MPa, and the space velocity is 3000 h -1 , After reacting for 1000 h, samples are taken to analyze the activity and selectivity of the catalyst, and the STY of the catalyst, the selectivity of dimethyl carbonate, and the conversion rate of methyl chloroformate are calculated. The results are shown in Table 1 below.

[0117] Table 1 Effect data of examples and comparative examples

[0118]

[0119] By comparing the catalytic activity, selectivity, and the conversion rate of haloester of the catalysts in the above examples and comparative examples, it can be obtained that the catalyst prepared by this patent has excellent catalytic activity, selectivity, and stability. At the same time, during the operation process, the catalyst can efficiently decarbonylate the haloester to convert it into haloalkane, solving the corrosion problem of the haloester to the equipment.

Claims

1. A bifunctional catalyst for synthesizing carbonate, characterized in that, It comprises the following components: (1) Group VIII B metal active component; (2) Group III B metal promoter; (3) Modified carrier; Among them, the Group VIII B metal active component in component (1) is selected from compounds containing one or more metal elements among Fe, Co, Ni, Ru, Rh, Pd, and Pt. The Group III B metal promoter in component (2) is selected from compounds containing one or more metal elements among Sc, Y, La, Ce, and Nd.

2. The bifunctional catalyst according to claim 1, wherein The modified carrier in component (3) is a carrier containing a modifier, and the modifier is selected from one or more metal elements among Rb, Cs, Fr, Be, Sr, Ba, and Ra, and the modifier exists in the form of an oxide; and / or The carrier in component (3) is selected from one or more of silica, alumina, activated carbon, diamond, spinel, and molecular sieve.

3. The bifunctional catalyst according to claim 1, wherein, Based on the total mass of the catalyst, the Group VIII B metal active component in component (1) is calculated as a compound, and the content is 0.1 - 10 wt%, preferably 0.1 - 5 wt%; the Group III B metal promoter in component (2) is calculated as a compound, and the content is 0.1 - 10 wt%, preferably 0.1 - 5 wt%; the balance is the modified carrier in component (3), totaling 100 wt%; and / or For the modified carrier in component (3), the modifier is calculated as a metal element, and the content is 0.1 - 10 wt%, preferably 0.1 - 5 wt%, based on the total mass of the modified carrier.

4. The bifunctional catalyst according to any one of claims 1 to 3, wherein The modified carrier in component (3) is a carrier containing a modifier, and its modification method is as follows: Method a) The steps include: during the conventional carrier forming process, dissolving the salt containing the modifier in water, fully mixing it with the carrier raw material slurry in proportion and then forming, and calcining at a suitable temperature to obtain the carrier containing the modifier; and / or Method b) The steps include: dissolving the salt containing the modifier in water, mixing it with the unmodified carrier for equal-volume impregnation, and calcining at a suitable temperature to obtain the carrier containing the modifier; Preferably, the calcination temperature in methods a) and b) is 500 - 1000 °C, preferably 600 - 800 °C; the calcination time is 1 - 10 h; Preferably, the salt containing the modifier in methods a) and b) is selected from one or more of nitrates, carbonates, and organometallic salts of the metal corresponding to the modifier, preferably one or more of metal nitrates and carbonates, more preferably metal nitrates.

5. A method for preparing a bifunctional catalyst for synthesizing a carbonate according to any one of claims 1-4, characterized in that, It includes the following steps: 1) Dissolving the precursor of the Group VIII B metal in component (1) and the precursor of the Group III B metal in component (2) in an aqueous solvent to obtain an impregnation solution; 2) Mixing the impregnation solution in step 1) with the modified carrier for impregnation, and after impregnation, drying and calcining the carrier to obtain a bifunctional catalyst for synthesizing carbonate.

6. The preparation method according to claim 5, characterized in that, The precursor of the Group VIII B metal in component (1) and the precursor of the Group III B metal in component (2) in step 1) are selected from salts of the corresponding metals, among which the salts are selected from one or more of nitrates, halides, and metal complexes, preferably nitrates and / or halides, more preferably halides; and / or The aqueous solvent in step 1) is selected from at least one of water, hydrochloric acid, sodium hydroxide aqueous solution, and ammonia aqueous solution; Preferably, the aqueous solvent has a water content of 10-100 wt%; and / or In the impregnation solution of step 1), based on its total mass being 100%, the content of the precursor of the Group VIII B metal in component (1) is 0.1-8.0 wt%, and the content of the precursor of the Group III B metal in component (2) is 0.1-8.0 wt%; and / or In step 2), the mass ratio of the impregnation solution to the modified support is 0.5-1:1; preferably, in step 2), the impregnation solution and the modified support are mixed according to the equal-volume impregnation ratio; Preferably, for the impregnation, the temperature is 0-50 °C and the time is 0.5-10 h; and / or In step 2), the drying temperature is 100-150 °C, and the water content is controlled to be less than 20 wt%, preferably less than 10 wt%; the calcination temperature is 150-300 °C, and the calcination time is 1-10 h.

7. Use of the bifunctional catalyst for synthesizing a carbonate according to any one of claims 1-4 or the bifunctional catalyst for synthesizing a carbonate prepared by the method according to claim 5 or 6 in the field of synthesizing a carbonate, characterized in that, React nitrite and carbon monoxide in the presence of a catalyst to prepare a carbonate.

8. A method for preparing a carbonate, characterized in that the steps It includes: In the presence of the bifunctional catalyst for synthesizing carbonate according to any one of claims 1-4 or the bifunctional catalyst for synthesizing carbonate prepared by the method according to claim 5 or 6, using nitrite and carbon monoxide as raw materials and a halide as a stabilizer, react to prepare a carbonate.

9. The preparation method according to claim 8, characterized in that, The nitrite is at least one of nitrites containing C1-C4 alkyl groups, preferably at least one of nitrites containing C1-C2 alkyl groups; Preferably, the nitrite is selected from at least one of methyl nitrite and ethyl nitrite; and / or The molar ratio of the nitrite to carbon monoxide is 10:1-1:10, preferably 2:1-1:2; and / or The halide is selected from at least one of hydrogen halides and haloalkanes, preferably at least one of chlorides, fluorides, and bromides; Preferably, the molar ratio of the halide to the carbon monoxide feed is 1 / 10-1 / 10000, preferably 1 / 100-1 / 5000.

10. The preparation method according to claim 8, characterized in that, When the nitrite and carbon monoxide are fed, their volume concentrations in the reactor are both controlled at 1-30%, preferably 10-25%, and the rest is balanced with an inert component; The inert component is selected from nitrogen and carbon dioxide; and / or For the reaction, the temperature is 30-250 °C, preferably 80-180 °C; the reaction pressure is 0-2 MPa, preferably 0.5-1 MPa; Preferably, the space velocity of the reaction is controlled to be 500 - 8000 h -1 , preferably 1000 - 5000 h -1 ; and / or The reaction is carried out in a fixed bed or a fluidized bed, preferably a fixed bed.

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