A multilayer catalyst for producing carbonates, a preparation method and applications thereof

Abstract

This invention provides a multilayer catalyst for the production of carbonates, comprising at least three catalyst layers arranged sequentially within a reaction tube. The invention further relates to its use in catalyzing the reaction of nitrite and carbon monoxide to produce carbonates in the presence of this catalyst. The catalyst exhibits high catalytic activity and product selectivity, and demonstrates good stability during long-term operation testing. Simultaneously with catalyzing the main reaction to produce carbonates, the catalyst prepared by this invention can convert highly corrosive halides in the reactants into non-corrosive halides, thus solving the equipment corrosion problem during operation.

Description

Technical Field

[0001] This invention relates to a multilayer catalyst for the preparation of carbonates, and more particularly to the use of the catalyst in the catalytic reaction of nitrites and carbon monoxide to produce carbonates. Background Technology

[0002] Carbonates, as an important class of organic compounds, are widely used in solvents, polymer materials, and lithium-ion battery electrolytes. Currently, their industrial preparation methods mainly include methanol gas-phase carbonylation, phosgene method, transesterification method, and carbon dioxide method. Among these, the phosgene method is limited due to the high toxicity of the raw materials and high safety risks; the transesterification method and the carbon dioxide method face bottlenecks such as high raw material costs and low reaction efficiency. In contrast, the methanol gas-phase carbonylation method has attracted widespread attention from researchers both domestically and internationally due to its advantages such as wide availability of raw materials, mild reaction conditions, and environmental friendliness.

[0003] Gas-phase carbonylation typically uses nitrite esters and carbon monoxide as raw materials, reacting them in the presence of a catalyst to produce carbonates. This process is a gas-solid phase reaction, and its core lies in the design and development of the catalyst. However, existing catalysts generally suffer from low activity and insufficient stability, limiting the large-scale application of this process. Therefore, developing catalysts with both high activity and long lifespan has become a research hotspot in this field in recent years.

[0004] In catalyst development, several patents have proposed improved solutions. For example, patent CN111420675B reports a catalyst system using a support modified with Group VIB elements, supporting palladium as the active component, and introducing transition metals as promoters. This catalyst requires the addition of 50–300 ppm of hydrogen chloride during the reaction process and maintains good stability even after continuous operation for more than 500 hours. Another patent, CN111760580A, proposes a Pd-Cu-Ce / lithium-aluminum composite catalyst, which also requires the addition of 50–500 ppm of hydrogen chloride and exhibits excellent stability in continuous reactions up to 1000 hours.

[0005] The above studies demonstrate that introducing halides (such as hydrogen chloride) as stabilizers can effectively improve the structural stability and lifespan of catalysts during the reaction process. However, this strategy also brings new technical challenges: while the main reaction proceeds, side reactions may occur in the system to generate haloesters, and incomplete halide reactions can leave residues in the system. These compounds are highly corrosive and can easily cause severe corrosion to reaction equipment under long-term operation, increasing maintenance costs and posing significant safety hazards. Therefore, converting highly corrosive halides into non-corrosive halides has become a key step in mitigating system corrosion problems.

[0006] Currently, significant progress has been made in the research of catalysts for the methanol carbonylation process to prepare carbonates, particularly in the areas of active component design, support modification, and auxiliary agent regulation, where rich experience has been accumulated. However, effectively addressing equipment corrosion caused by halide stabilizers while maintaining high catalyst activity, high selectivity, and long-term stability remains a key challenge hindering the further development of this technology. Summary of the Invention

[0007] To address the aforementioned technical challenges, this invention aims to provide a catalyst and its preparation method for the carbonylation reaction of nitrite esters with carbon monoxide. This catalyst exhibits excellent catalytic activity and product selectivity in a reaction system with a halide stabilizer, and also maintains structural stability and reliable performance over long-term operation.

[0008] The significant advantage of this invention is that, while the catalyst efficiently catalyzes the main reaction to generate the target carbonate, it can also convert highly corrosive halides in the reaction feedstock into non-corrosive halides. This unique function fundamentally alleviates the corrosion problem of the reaction equipment in the process, effectively extends the service life of the equipment, and improves the safety and economy of the process.

[0009] Another objective of this invention is to provide a method for preparing carbonates by catalyzing the carbonylation reaction of nitrite esters with carbon monoxide using a catalyst. During this catalytic reaction, the catalyst exhibits high reactivity and long-term stability, enabling efficient and continuous synthesis of carbonates while addressing corrosion risks, thus providing a feasible technical path for the green and safe industrial production of carbonates.

[0010] To achieve the above objectives, the present invention adopts the following solution:

[0011] A multilayer catalyst for the carbonylation reaction of nitrite with carbon monoxide to produce carbonate, comprising at least three catalyst layers, wherein each catalyst layer comprises a Group VIII active metal compound, a Group IB active metal compound, a support, and alkali metal and lanthanide metal promoters;

[0012] The composition of each catalyst layer is as follows (the content of each component in each catalyst layer is based on the total mass of Group VIII active metal compounds, Group IB active metal compounds, alkali metal promoters, and lanthanide metal promoters in each layer):

[0013] a) A-layer catalyst: The contents of group VIII active metal compound and group IB active metal compound are preferably 0.1-3 wt% and 0.1-3 wt%, respectively; the contents of alkali metal promoter are preferably 2-3 wt%; the contents of lanthanide metal promoter are preferably 0.1-1 wt%; and the remainder is a support.

[0014] b) B-layer catalyst: The contents of group VIII active metal compound and group IB active metal compound are preferably 0.1-3 wt% and 0.1-3 wt%, respectively; the contents of alkali metal promoter are preferably 1-2 wt%; the contents of lanthanide metal promoter are preferably 1-2 wt%; and the remainder is a support.

[0015] c) C-layer catalyst: The contents of group VIII active metal compound and group IB active metal compound are preferably 0.1-3 wt% and 0.1-3 wt%, respectively; the contents of alkali metal promoter are preferably 0.1-1 wt%; the contents of lanthanide metal promoter are preferably 2-3 wt%; and the remainder is a support.

[0016] In this invention, the group VIII active metal is preferably one or more of Pd, Pt, and Rh; the group IB active metal is preferably one or more of Cu, Ag, and Au; the alkali metal is preferably one or more of Na, K, and Cs; and the lanthanide metal is preferably one or more of La, Ce, and Pr.

[0017] In this invention, the group VIII active metal compounds and group IB active metal compounds are selected from the salts corresponding to the respective metals, including one or more of carbonates, nitrates, halides, sulfates, phosphates and metal complexes, preferably halides.

[0018] In this invention, the alkali metal auxiliaries and lanthanide metal auxiliaries are derived from the salts corresponding to the respective metals, including one or more of carbonates, nitrates, halides, sulfates, phosphates and metal complexes, preferably halides.

[0019] In this invention, the carrier is derived from one or more of silicon dioxide, alumina, activated carbon, diamond, spinel, and molecular sieve, with spinel being preferred; the shape of the formed carrier is not limited, but spherical or strip-shaped is preferred.

[0020] In this invention, the catalyst layers in the reactor meet the following filling height requirements:

[0021] a) The preferred catalyst filling height for layer A is 10-20% of the total catalyst filling height;

[0022] b) The preferred catalyst packing height for layer B is 60-80% of the total catalyst packing height;

[0023] c) The preferred catalyst packing height for layer C is 10-20% of the total catalyst packing height.

[0024] The present invention also relates to a method for preparing the multilayer catalyst.

[0025] In this invention, the preparation processes of each catalyst layer are similar, and the loading amount is controlled by adjusting the amount of the corresponding metal precursor added.

[0026] In one specific preparation method, Group VIII active metal compounds and Group IB active metal compounds are impregnated simultaneously, as are alkali metal additives and lanthanide metal additives. The two parts are impregnated in a stepwise manner, with priority given to impregnating the alkali metal additives and lanthanide metal additives. The preferred impregnation method is equal-volume impregnation. Specifically: first, the carrier is impregnated in a solution containing alkali metal additives and lanthanide metal additives. After impregnation, it is preferably dynamically dried at 80-100℃ for 2-10 hours, followed by calcination at 200-300℃ for 2-10 hours. Then, it is impregnated in a solution containing Group VIII and Group IB active metal compounds. After impregnation, it is preferably dynamically dried at 80-100℃ for 2-10 hours, followed by calcination at 100-200℃ for 2-10 hours.

[0027] The present invention also provides the application of the above-described catalyst in the production of carbonates.

[0028] The method for producing carbonates by carbonylation reaction of nitrite and carbon monoxide involves loading each catalyst layer into the reactor in the order of A→B→C according to the flow direction of the feed gas (i.e., the feed gas first contacts layer A). Under the presence of this catalyst, nitrite and carbon monoxide are used as feedstocks, and halides are used as stabilizers to prepare carbonates.

[0029] The nitrite is at least one of nitrites containing C1-C4 alkyl groups, preferably at least one of nitrites containing C1-C2 alkyl groups;

[0030] Preferably, the nitrite is selected from at least one of methyl nitrite and ethyl nitrite.

[0031] The molar ratio of nitrite to carbon monoxide is 10:1 to 1:10, preferably 2:1 to 1:2.

[0032] The halide is selected from at least one of hydrogen halides and haloalkanes, preferably at least one of chlorides, fluorides, and bromides, and more preferably hydrogen chloride.

[0033] The molar ratio of the halide to carbon monoxide in the feed is 1 / 10 to 1 / 10000, preferably 1 / 100 to 1 / 5000.

[0034] In this invention, when the nitrite and carbon monoxide are fed into the reactor, their volume concentrations (as a percentage of the total volume of methyl nitrite, CO, inert components, and hydrogen chloride) are controlled at 1-30%, preferably 10-25%, with the remainder balanced by inert components. The inert components are selected from nitrogen and carbon dioxide.

[0035] The reaction temperature is 30-250℃, preferably 80-180℃. The reaction pressure is 0-2MPa, preferably 0.5-1MPa. The volume hourly space velocity (VHSV) of the reaction (total for all components) is controlled at 500-8000 h⁻¹. -1 Preferred range: 1000-5000h -1 .

[0036] The reaction is carried out in a fixed bed or a fluidized bed, preferably a fixed bed.

[0037] The beneficial effects of this invention are as follows:

[0038] This invention provides a multilayer catalyst that, while efficiently catalyzing the main reaction to generate the target carbonate, can convert highly corrosive halides in the reaction feedstock into non-corrosive halides. This unique function fundamentally alleviates the corrosion problem of the reaction equipment in the process, effectively extends the service life of the equipment, and improves the safety and economy of the process.

[0039] In this catalytic reaction, the catalyst exhibits high reactivity and long-term stability, enabling efficient and continuous synthesis of carbonates while addressing corrosion risks, thus providing a feasible technical path for the green and safe industrial production of carbonates. Detailed Implementation

[0040] The following embodiments further illustrate preferred specific embodiments within the scope of the present invention. These embodiments are merely illustrative and not intended to limit the scope of the present invention. The purpose of the following embodiments is to further introduce and demonstrate specific embodiments within the scope of the present invention. Therefore, the embodiments should be understood as being used only to illustrate the present invention in more detail and not to limit the content of the present invention in any way.

[0041] Main raw material sources

[0042] Unless otherwise specified, all ingredients are derived from Aladdin.

[0043] Main testing methods

[0044] This invention uses inductively coupled plasma optical emission spectrometry (ICP-OES) to quantitatively analyze the content of each component in the catalyst.

[0045] This invention analyzes the composition of the reaction solution using gas chromatography-2014, calculates the reaction performance (STY value) using equation (1), and calculates the selectivity of the target product using equation (2). Catalyst stability is determined by the trend of performance changes over a certain period of time.

[0046] This invention detects the residual amounts of hydrogen chloride and methyl chloroformate in the reaction products to assess the catalyst's ability to convert corrosive chlorides.

[0047] (1)STY(g·L -1 ·h -1 ) = Amount of main product formed (g) / Catalyst volume (L) / Time (h);

[0048] (2) Selectivity% = Amount of reactants consumed to generate the target product (mol) / Amount of reactants involved in the reaction (mol) * 100.

[0049] Example 1

[0050] Catalyst preparation:

[0051] Layer A-1: ​​The catalyst was prepared with PdCl2, CuCl2, KCl, and LaCl3 loadings of 2wt%, 2wt%, 2.5wt%, and 0.5wt%, respectively, and the spinel support content was 93wt%. The support had a water absorption rate of 60%.

[0052] Weigh out 93g of spinel support, 2.5g of KCl, 0.5g of LaCl3, 2g of CuCl2, and 2g of PdCl2 respectively, and prepare a 5wt% HCl aqueous solution.

[0053] 2.5g KCl and 0.5g LaCl3 were dissolved in 52.8g 5wt% HCl solution at room temperature, and then mixed with 93g spinel support by impregnation in an equal volume manner. The mixture was dynamically dried at 90℃ for 5h and calcined at 250℃ for 5h.

[0054] 2g CuCl2 and 2g PdCl2 were dissolved in 51.8g 5wt% HCl solution at room temperature, and mixed with a K / La supported support by an equal volume impregnation method. The mixture was dynamically dried at 90℃ for 5h and calcined at 150℃ for 5h to obtain the A-1 catalyst.

[0055] Layer B-1: The catalyst was prepared with PdCl2, CuCl2, KCl, and LaCl3 loadings of 2wt%, 2wt%, 1.5wt%, and 1.5wt%, respectively, and the spinel support content was 93wt%. The support had a water absorption rate of 60%.

[0056] Weigh out 93g of spinel support, 1.5g of KCl, 1.5g of LaCl3, 2g of CuCl2, and 2g of PdCl2 respectively, and prepare a 5wt% HCl aqueous solution.

[0057] 1.5g KCl and 1.5g LaCl3 were dissolved in 52.8g 5wt% HCl solution at room temperature, and then mixed with 93g spinel support by impregnation in an equal volume manner. The mixture was dynamically dried at 80℃ for 5h and calcined at 200℃ for 5h.

[0058] 2g CuCl2 and 2g PdCl2 were dissolved in 51.8g 5wt% HCl solution at room temperature, and mixed with a K / La supported support by an equal volume impregnation method. The mixture was dynamically dried at 80℃ for 5h and calcined at 100℃ for 5h to obtain the B-1 catalyst.

[0059] C-1 layer: The catalyst was prepared with PdCl2, CuCl2, KCl, and LaCl3 at mass loadings of 2wt%, 2wt%, 0.5wt%, and 2.5wt%, respectively, and the spinel support content was 93wt%. The support had a water absorption rate of 60%.

[0060] Weigh out 93g of spinel support, 0.5g of KCl, 2.5g of LaCl3, 2g of CuCl2, and 2g of PdCl2 respectively, and prepare a 5wt% HCl aqueous solution.

[0061] 0.5g KCl and 2.5g LaCl3 were dissolved in 52.8g 5wt% HCl solution at room temperature, and then mixed with 93g spinel support by impregnation in an equal volume manner. The mixture was dynamically dried at 100℃ for 5h and calcined at 300℃ for 5h.

[0062] 2g CuCl2 and 2g PdCl2 were dissolved in 51.8g 5wt% HCl solution at room temperature, and mixed with a K / La supported support by an equal volume impregnation method. The mixture was dynamically dried at 100℃ for 5h and calcined at 200℃ for 5h to obtain the C-1 catalyst.

[0063] Catalyst activity evaluation

[0064] The catalysts prepared above were measured and loaded according to the A / B / C layer catalyst loading height (percentage) shown in Table 1 for Examples 1-3 and Comparative Examples 1-3. The volume concentrations of methyl nitrite and CO in the feed were controlled at 12% (the remainder was balanced with nitrogen), the molar ratio of hydrogen chloride to carbon monoxide in the feed was 1 / 3000, the reaction temperature was 130℃, the reaction pressure was 0.8MPa, and the volume hourly space velocity was 3000h. -1 After 1000 hours of reaction, samples were taken to analyze the catalyst activity and selectivity. The catalyst STY, dimethyl carbonate selectivity, residual hydrogen chloride, and residual methyl chloroformate were calculated. The results are shown in Table 1 below.

[0065] Table 1 Activity Data

[0066]

[0067]

[0068] Example 4

[0069] Catalyst preparation:

[0070] Layer A-2: The catalyst was prepared with Pt(NO3)2, CuSO4, Na2CO3, and Ce(NO3)3 at mass loadings of 3wt%, 3wt%, 2wt%, and 0.1wt%, respectively, and the activated carbon support content was 91.9wt%. The water absorption rate of the support was 80%.

[0071] Weigh out 91.9g of activated carbon carrier, 3g of Pt(NO3)2, 3g of CuSO4, 2g of Na2CO3, and 0.1g of Ce(NO3)3 respectively, and prepare a 5wt% HCl aqueous solution.

[0072] 2g Na2CO3 and 0.1g Ce(NO3)3 were dissolved in 71.42g 5wt% HCl solution at room temperature, and then mixed with 91.9g activated carbon carrier by impregnation in an equal volume manner. The mixture was dynamically dried at 90℃ for 5h and calcined at 250℃ for 5h.

[0073] 3g Pt(NO3)2 and 3g CuSO4 were dissolved in 67.52g 5wt% HCl solution at room temperature, and mixed with a Na / Ce-supported carrier by an equal volume impregnation method. The mixture was dynamically dried at 90℃ for 5h and calcined at 150℃ for 5h to obtain the A-2 catalyst.

[0074] B-2 layer: The catalyst was prepared in the same manner as A-2 layer, with mass loadings of Pt(NO3)2, CuSO4, Na2CO3 and Ce(NO3)3 of 3wt%, 3wt%, 1wt%, and 1wt%, respectively.

[0075] C-2 layer: The catalyst was prepared in the same manner as A-2 layer, with mass loadings of Pt(NO3)2, CuSO4, Na2CO3 and Ce(NO3)3 of 3wt%, 3wt%, 0.1wt%, and 2wt%, respectively.

[0076] Catalyst activity evaluation:

[0077] The catalysts prepared above were measured and loaded according to the catalyst loading ratio of A / B / C layers as shown in Table 2 below. The evaluation conditions were the same as in Example 1, and the results are shown in Table 2 below.

[0078] Example 5

[0079] Catalyst preparation:

[0080] Layer A-3: The catalyst was prepared by loading Pt(NO3)2, CuSO4, Na2CO3, and Ce(NO3)3 with mass loadings of 0.1wt%, 0.1wt%, 3wt%, and 1wt%, respectively, with a silica support content of 95.8wt%. The support had a water absorption rate of 65%.

[0081] Weigh out 95.8g of silica support, 0.1g of Pt(NO3)2, 0.1g of CuSO4, 3g of Na2CO3, and 1g of Ce(NO3)3 respectively, and prepare a 5wt% HCl aqueous solution.

[0082] 3g Na2CO3 and 1g Ce(NO3)3 were dissolved in 58.27g 5wt% HCl solution at room temperature, and then mixed with 95.8g silica support by impregnation in equal volume. The mixture was dynamically dried at 90℃ for 5h and calcined at 250℃ for 5h.

[0083] 0.1 g Pt(NO3)2 and 0.1 g CuSO4 were dissolved in 62.07 g 5 wt% HCl solution at room temperature, and mixed with a Na / Ce-supported carrier by an equal volume impregnation method. The mixture was dynamically dried at 90 °C for 5 h and calcined at 150 °C for 5 h to obtain the A-3 catalyst.

[0084] Layer B-3: The catalyst was prepared by loading Pt(NO3)2, CuSO4, Na2CO3, and Ce(NO3)3 with mass loadings of 0.1wt%, 0.1wt%, 2wt%, and 2wt%, respectively, with a silica support content of 95.8wt%. The support had a water absorption rate of 65%, and the catalyst preparation process was the same as that of Layer A-3.

[0085] C-3 layer: The catalyst was prepared by loading Pt(NO3)2, CuSO4, Na2CO3, and Ce(NO3)3 with mass loadings of 0.1wt%, 0.1wt%, 1wt%, and 3wt%, respectively, with a silica support content of 95.8wt%. The support had a water absorption rate of 65%, and the catalyst preparation process was the same as that of A-3.

[0086] Catalyst activity evaluation:

[0087] The catalysts prepared above were measured and loaded according to the catalyst loading ratio of A / B / C layers as shown in Table 2 below. The evaluation conditions were the same as in Example 1, and the results are shown in Table 2 below.

[0088] Comparative Example 4

[0089] Catalyst preparation:

[0090] Layer A-4: The catalyst was prepared with PdCl2, CuCl2, and KCl loadings of 2wt%, 2wt%, and 4wt%, respectively, and the spinel support content was 92wt%. The support had a water absorption rate of 60%.

[0091] Weigh out 92g of spinel support, 4g of KCl, 2g of CuCl2, and 2g of PdCl2 respectively, and prepare a 5wt% HCl aqueous solution.

[0092] 4g of KCl was dissolved in 51.2g of 5wt% HCl solution at room temperature, and then mixed with 92g of spinel carrier by impregnation in an equal volume manner. The mixture was dynamically dried at 90℃ for 5h and calcined at 250℃ for 5h.

[0093] 2g CuCl2 and 2g PdCl2 were dissolved in 51.2g 5wt% HCl solution at room temperature, and mixed with the K-supported carrier by equal volume impregnation. The mixture was dynamically dried at 90℃ for 5h and calcined at 150℃ for 5h to obtain the A-4 catalyst.

[0094] B-4 layer: The catalyst was prepared with PdCl2, CuCl2 and LaCl3 mass loadings of 2wt%, 2wt% and 3wt% respectively, spinel support content of 93wt% and support water absorption rate of 60%. The catalyst preparation process was the same as that of A-4.

[0095] C-4 layer: The catalyst was prepared with PdCl2, CuCl2, and LaCl3 loadings of 2wt%, 2wt%, and 4wt%, respectively, and the spinel support content was 92wt%. The support had a water absorption rate of 60%, and the catalyst preparation process was the same as that of A-4.

[0096] Catalyst activity evaluation

[0097] The catalysts prepared above were measured and loaded according to the catalyst loading ratio of A / B / C layers as shown in Table 2 below. The evaluation conditions were the same as in Example 1, and the results are shown in Table 2 below.

[0098] Table 2 Activity Data

[0099]

[0100]

[0101] Example 6

[0102] The catalyst was loaded according to the A / B / C layer loading ratio of 15 / 70 / 15 as in Example 1. The feed concentrations of methyl nitrite and CO were controlled at 25% and 12% respectively (the remainder was balanced with nitrogen), the molar ratio of hydrogen chloride to carbon monoxide was 1 / 6000, the reaction temperature was 200°C, the reaction pressure was 1.5 MPa, and the volume hourly space velocity was 1000 h⁻¹. -1 After 1000 hours of reaction, samples were taken to analyze the catalyst activity and selectivity. The catalyst STY, dimethyl carbonate selectivity, residual hydrogen chloride, and residual methyl chloroformate were calculated. The results are shown in Table 3 below.

[0103] Example 7

[0104] The catalyst was loaded according to the A / B / C layer loading ratio of 15 / 70 / 15 as in Example 1. The feed concentrations of methyl nitrite and CO were controlled at 12% and 5% respectively (the remainder was balanced with nitrogen), the molar ratio of hydrogen chloride to carbon monoxide was 1 / 200, the reaction temperature was 100°C, the reaction pressure was 0.2 MPa, and the volume hourly space velocity was 6000 h⁻¹. -1 After 1000 hours of reaction, samples were taken to analyze the catalyst activity and selectivity. The catalyst STY, dimethyl carbonate selectivity, residual hydrogen chloride, and residual methyl chloroformate were calculated. The results are shown in Table 3 below.

[0105] Table 3 Activity Data

[0106]

[0107] By comparing the catalyst activity, selectivity, and residual amount of highly corrosive halides in the above embodiments and comparative examples, it can be seen that the catalyst prepared by this patent has excellent catalytic activity, selectivity, and stability. At the same time, the catalyst can convert highly corrosive halides into non-corrosive halides during operation, thus solving the problem of equipment corrosion during operation.

Claims

1. A multilayer catalyst for producing carbonates, comprising at least three catalyst layers, wherein the composition of each catalyst layer is as follows, wherein the content of each component in each catalyst layer is based on the total mass of Group VIII active metal compound, Group IB active metal compound, alkali metal promoter, and lanthanide metal promoter in each layer: a) Layer A catalyst: Group VIII active metal compound and Group IB active metal compound content are 0.1-3wt% and 0.1-3wt% respectively, alkali metal promoter content is 2-3wt%, lanthanide metal promoter content is 0.1-1wt%, and the remainder is support; b) B-layer catalyst: Group VIII active metal compound and Group IB active metal compound content are 0.1-3wt% and 0.1-3wt% respectively, alkali metal promoter content is 1-2wt%, lanthanide metal promoter content is 1-2wt%, and the rest is support; c) C-layer catalyst: Group VIII active metal compound and Group IB active metal compound content are 0.1-3wt% and 0.1-3wt%, respectively; alkali metal promoter content is 0.1-1wt%; lanthanide metal promoter content is 2-3wt%; and the remainder is support.

2. The multilayer catalyst according to claim 1, wherein, Group VIII active metals are selected from one or more of Pd, Pt, and Rh; Group IB active metals are selected from one or more of Cu, Ag, and Au; Alkali metals are selected from one or more of Na, K, and Cs; Lanthanide metals are selected from one or more of La, Ce, and Pr.

3. The multilayer catalyst according to claim 1 or 2, wherein, Group VIII active metal compounds and Group IB active metal compounds are selected from the salts corresponding to the respective metals, including one or more of carbonates, nitrates, halides, sulfates, phosphates and metal complexes, with halides being preferred; Alkali metal auxiliaries and lanthanide metal auxiliaries are selected from the salts corresponding to the respective metals, including one or more of carbonates, nitrates, halides, sulfates, phosphates and metal complexes, with halides being preferred.

4. The multilayer catalyst according to claim 1 or 2, wherein, The carrier is derived from one or more of silicon dioxide, alumina, activated carbon, diamond, spinel, and molecular sieves.

5. The multilayer catalyst according to any one of claims 1-4, wherein, The catalyst layers in the reactor meet the following filling height requirements: a) The catalyst filling height of layer A is 10-20% of the total catalyst filling height; b) The catalyst filling height of layer B is 60-80% of the total catalyst filling height; c) The catalyst packing height of layer C is 10-20% of the total catalyst packing height.

6. The application of the multilayer catalyst according to any one of claims 1-5 in the production of carbonates, characterized in that, Following the flow direction of the raw gas, each catalyst layer is sequentially loaded into the reactor in the order of A→B→C. Under the presence of this catalyst, carbonates are prepared by reacting nitrite and carbon monoxide as raw materials and halides as stabilizers.

7. The preparation method according to claim 6, characterized in that, The nitrite is at least one of nitrites containing C1-C4 alkyl groups, preferably at least one of methyl nitrite and ethyl nitrite.

8. The preparation method according to claim 6 or 7, characterized in that, The molar ratio of nitrite to carbon monoxide is 10:1 to 1:10, preferably 2:1 to 1:2; 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 carbon monoxide in the feed is 1 / 10 to 1 / 10000, more preferably 1 / 100 to 1 / 5000.

9. The preparation method according to claim 6, characterized in that, When the nitrite and carbon monoxide are fed into the reactor, their volume concentrations are controlled at 1-30%, preferably 10-25%, with the remainder balanced with inert components. The inert component is selected from nitrogen and carbon dioxide.

10. The preparation method according to any one of claims 6-9, characterized in that, The reaction is carried out at a temperature of 30-250℃, preferably 80-180℃, and at a pressure of 0-2MPa, preferably 0.5-1MPa. Volumetric hourly space velocity (VHSV) controlled at 500-8000 h -1 Preferred range: 1000-5000h -1 ; The reaction is carried out in a fixed bed or a fluidized bed.

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