Co-production of alloy catalyst from dimethyl oxalate and dimethyl carbonate and its preparation method

Abstract

This application discloses an alloy catalyst for the co-production of dimethyl oxalate and dimethyl carbonate, and its preparation method. The catalyst comprises a support formed by mixing γ-Al₂O₃ and molecular sieves, an active component, and an auxiliary agent. Based on the support, the active component is a Pd source with a mass fraction of 0.05%–0.2%; the auxiliary agent is a rare earth metal with a mass fraction of 0.5%–1%. The Pd in ​​the catalyst is a single atom dispersed in the rare earth metal, forming an alloy with it. The alloy single-atom catalyst of this application has a uniformly distributed and low-content Pd active component, suitable for the synthesis of dimethyl oxalate and dimethyl carbonate from gaseous carbon monoxide and methyl nitrite. It has advantages such as high feed conversion rate, good target product selectivity, highly flexible and adjustable product selectivity for dimethyl oxalate and dimethyl carbonate, and long lifetime, and is suitable for industrial production applications.

Description

Technical Field

[0001] This application relates to the field of catalyst preparation technology, and in particular to an alloy catalyst for the co-production of dimethyl oxalate and dimethyl carbonate and its preparation method. Background Technology

[0002] Dimethyl oxalate is an important organic chemical raw material and an intermediate product in the syngas-to-ethylene glycol route. The synthesis of dimethyl oxalate using carbon monoxide catalytic coupling is an environmentally friendly and atom-economically efficient process. In this process, oxalate esters are the main product, with a selectivity exceeding 90%, and byproducts primarily include dimethyl carbonate and methyl formate (MF). Recently, with the booming development of the lithium-ion battery industry, the demand and market price of dimethyl carbonate have remained high. Therefore, improving the profitability of syngas-to-ethylene glycol plants by adjusting the catalyst composition and process conditions to modify the distribution of syngas products and enhance the selectivity of dimethyl carbonate is both foreseeable and theoretically feasible. Furthermore, the implementation of a co-production system would help alleviate the current situation of persistently low ethylene glycol prices, continuous plant shutdowns, and severe losses for enterprises.

[0003] The research technology of DMC or DMO catalysts is relatively mature. However, whether synthesizing single DMO or DMC, there will always be a small amount of another byproduct. The specific reasons are: (1) Cl ions and Cu ions in the system are conducive to the generation of DMC; (2) Lewis acidic environment is conducive to the generation of DMC, while Lewis alkaline environment is conducive to the generation of DMO; (3) Isolated Pd is conducive to the generation of DMC, while aggregated Pd is conducive to the generation of DMO; (4) (111) crystal plane is conducive to the generation of DMO.

[0004] The aforementioned systems all target either DMC or DMO as the product, with the other existing as an unavoidable impurity. Current research on DMO and DMC co-production systems proposes using separate reactors for DMO and DMC synthesis, resulting in relatively complex equipment and processes that are not conducive to industrial implementation. Other related technologies aim to address the issues of dimethyl oxalate coking and dimethyl carbonate hydrolysis acidification, thereby reducing energy consumption and extending equipment lifespan, with a focus on process and flow design. While some schemes offer new ideas and methods for preparing high-performance catalysts, overall, even with a methyl nitrite conversion >80% and a total selectivity of DMO and DMC >99%, the relative selectivity of the two products remains not highly flexible and adjustable. Summary of the Invention

[0005] This application aims to at least partially solve one of the technical problems in the related technologies by proposing an alloy single-atom catalyst for the co-production of dimethyl oxalate and dimethyl carbonate from coal-based syngas via methyl nitrite and its preparation method. The alloy single-atom catalyst has a uniform distribution and low content of the active component Pd, which is suitable for the reaction of gaseous carbon monoxide and methyl nitrite to synthesize dimethyl oxalate and dimethyl carbonate. It has the advantages of high raw material conversion rate, good target product selectivity, highly flexible and adjustable product selectivity of dimethyl oxalate and dimethyl carbonate, and long lifespan, and can be adapted to industrial production applications.

[0006] To achieve the above objectives, a single-atom catalyst for the co-production of dimethyl oxalate and dimethyl carbonate is provided according to the first aspect of this application. The catalyst comprises a support formed by mixing γ-Al₂O₃ and a molecular sieve, an active component, and an auxiliary agent. Based on the support, the active component is a Pd source with a mass fraction of 0.05%-0.2%; the auxiliary agent is a rare earth metal with a mass fraction of 0.5%-1%; the Pd in ​​the catalyst is a single atom dispersed in the rare earth metal, and the Pd forms an alloy with the rare earth metal.

[0007] In some embodiments, the rare earth metal is one of lanthanum, cerium, yttrium, and scandium.

[0008] In some embodiments, the molecules are screened from one of ZSM-35, ReY, 13X, SBA-15, SAPO-11, or MCM-48; and their mass fraction is 15-50% based on the carrier.

[0009] In some embodiments, the diameter of the carrier is 3-5 mm.

[0010] In some embodiments, the Pd source is tetraaminopalladium nitrate, and the Pd content is ≤0.2%.

[0011] According to a second aspect of this application, a method for preparing a single-atom catalyst for the co-production of dimethyl oxalate and dimethyl carbonate is disclosed. The method for preparing the catalyst as described in any of the above embodiments includes the following steps:

[0012] Prepare a rare earth metal salt solution with a concentration of 5-10 mg / mL, load the carrier into the rare earth metal salt solution, let it stand for 2-4 hours and then dry it, and then calcine it at 150-400℃ in an inert gas atmosphere for 4-16 hours.

[0013] Prepare an aqueous solution of palladium source with a palladium ion concentration of 0.5-2 mg / mL, then load the carrier with the auxiliary agent onto palladium, let it stand for 2-4 hours, dry it, and then calcine it at 150-400℃ in an inert gas atmosphere for 4-16 hours to obtain the first sample;

[0014] The first sample was reduced at 100-150°C in a first mixed gas of hydrogen and nitrogen for 2-6 hours to obtain the second sample.

[0015] The catalyst is obtained by reducing the second sample at 150-200°C in a second mixed gas of carbon monoxide and nitrogen for 2-6 hours.

[0016] In some embodiments, the drying method is to dry at 70-110°C for 2-4 hours.

[0017] In some embodiments, the hydrogen volume fraction in the first mixture is 5-10 vol%, with the remainder being nitrogen.

[0018] In some embodiments, the second mixture contains 10-40% carbon monoxide by volume, with the remainder being nitrogen.

[0019] According to the third aspect of this application, the catalyst described in any of the above embodiments is used in the co-production of dimethyl oxalate and dimethyl carbonate from coal-based syngas via methyl nitrite, and its stability is not less than 1200 h.

[0020] This application employs a mixed support of γ-Al₂O₃ and a novel molecular sieve. The tetraaminopalladium nitrate complex preferentially exchanges ions with metal ions after entering the pores of the support, and is simultaneously coordinated and anchored by oxygen atoms in the support framework. High-temperature calcination allows Pd to exist in single-atom form, maintaining good catalytic performance even with low loading. Furthermore, the use of different rare earth metals as promoters significantly enhances the catalyst's activity and stability. Simultaneously, the reduction of Pd and rare earth metals disperses Pd within the rare earth metals, resulting in an alloy-like structure. Finally, the application employs multiple reducing atmospheres for multi-step reduction of the catalyst, ensuring that the single-atom Pd is in its optimal catalytic state. In the application of this catalyst in the carbonylation of methyl nitrite to dimethyl oxalate and dimethyl carbonate, it maintains high levels of feed conversion (≥80%) and target product selectivity (≥99%), while allowing for flexible control of the relative selectivity of DMO and DMC (1:9-9:1) within a wider range.

[0021] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0022] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:

[0023] Figure 1This is a flowchart of a catalyst method proposed in an embodiment of this application. Detailed Implementation

[0024] The embodiments of this application are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application. Rather, the embodiments of this application include all variations, modifications, and equivalents falling within the spirit and scope of the appended claims.

[0025] To achieve the above objectives, according to the first aspect of this application, a single-atom catalyst for the co-production of dimethyl oxalate and dimethyl carbonate is proposed. The catalyst comprises a support with a diameter of 3-5 mm formed by mixing γ-Al2O3 and molecular sieve, an active component, and an auxiliary agent. The active component, based on the support, is a Pd source with a mass fraction of 0.05%-0.2%. The auxiliary agent is a rare earth metal with a mass fraction of 0.5%-1%. The Pd in ​​the catalyst is a single atom dispersed in the rare earth metal, and the Pd forms an alloy with the rare earth metal.

[0026] In this embodiment, the rare earth metal is one of lanthanum, cerium, yttrium, and scandium; the molecule is screened from one of ZSM-35, ReY, 13X type, SBA-15, SAPO-11, or MCM-48; the mass fraction of the carrier is 15-50%; the Pd source is palladium tetraaminonitrate, and the Pd content is ≤0.2%.

[0027] According to a second aspect of this application, a method for preparing an alloy single-atom catalyst for the co-production of dimethyl oxalate and dimethyl carbonate is provided, as follows: Figure 1 The preparation of the catalyst as described in any of the above embodiments includes the following steps:

[0028] S1: Prepare a rare earth metal salt solution with a concentration of 5-10 mg / mL, load the carrier into the rare earth metal salt solution, let it stand for 2-4 hours and then dry it, and then calcine it at 150-400℃ in an inert gas atmosphere for 4-16 hours.

[0029] S2: Prepare an aqueous solution of palladium source with a palladium ion concentration of 0.5-2 mg / mL, then load the carrier with the auxiliary agent onto palladium, let it stand for 2-4 h and then dry it, and then calcine it at 150-400℃ in an inert gas atmosphere for 4-16 h to obtain the first sample;

[0030] S3: Reduce the first sample at 100-150℃ in a first mixed gas of hydrogen and nitrogen for 2-6 hours to obtain the second sample;

[0031] S4: The second sample is reduced at 150-200℃ in a second mixed gas of carbon monoxide and nitrogen for 2-6 hours to obtain the catalyst.

[0032] In S1, a rare earth metal salt solution with a concentration of 5-10 mg / mL is prepared. The rare earth metal salt solution is loaded onto a support formed by mixing γ-Al2O3 and molecular sieve, allowed to stand for 2-4 hours, dried at 70-110℃ for 2-4 hours, and calcined at 150-400℃ under an inert gas atmosphere for 4-16 hours.

[0033] Prepare an aqueous solution of palladium tetraaminonitrate with a palladium ion concentration of 0.5-2 mg / mL in S2. Then, load palladium tetraaminonitrate onto the support already loaded with additives in S1, let it stand for 2-4 hours, dry it under vacuum at 70-110℃ for 2-4 hours, and calcine it under an inert gas atmosphere at 150-400℃ for 4-16 hours to obtain the first sample.

[0034] In step S3, the first sample obtained in step S2 is reduced at 100-150℃ in a first mixed gas of hydrogen and nitrogen for 2-6 hours to obtain the second sample; wherein the volume fraction of hydrogen in the first mixed gas is 5-10v%, and the remainder is nitrogen.

[0035] In step S4, the second sample obtained in step S3 is reduced at 150-200℃ in a second mixed gas of carbon monoxide and nitrogen for 2-6 hours to obtain the catalyst; wherein the volume fraction of carbon monoxide in the second mixed gas is 10-40 v%, and the remainder is nitrogen. The two reduction steps in S3 and S4 are carried out in the same tube furnace, and nitrogen is introduced for protection during gas switching and heating.

[0036] The catalyst obtained in the embodiments of this application has a uniform distribution of active components, low loading, and is well applicable to the reaction of gaseous carbon monoxide and nitrite to synthesize dimethyl oxalate and dimethyl carbonate. It exhibits advantages such as high raw material conversion rate, good catalytic activity, and long lifespan, and has the prospect of being better adapted to industrial production processes.

[0037] According to the third aspect of this application, the catalyst in any of the above embodiments is proposed for use in the co-production of dimethyl oxalate and dimethyl carbonate from coal-based syngas via methyl nitrite, and its stability is not less than 1200 h.

[0038] In the reaction of carbonylation of methyl nitrite to co-produce dimethyl oxalate and dimethyl carbonate, this alloy single-atom catalyst can simultaneously ensure that the conversion rate of methyl nitrite is greater than 80%, the product ratio of dimethyl oxalate / dimethyl carbonate is 1:9-9:1, the total selectivity of both is greater than 99%, and the activity remains basically unchanged after 1200 hours of continuous operation.

[0039] Example 1

[0040] (1) Prepare a cerium nitrate solution with a concentration of 5 mg / mL. Load cerium nitrate onto a mixed support of 30% ZSM-35 molecular sieve and 70% γ-Al2O3, let stand for 3 hours, then dry at 90°C for 3 hours, and calcine at 250°C under an inert gas atmosphere for 8 hours.

[0041] (2) Prepare an aqueous solution of palladium nitrate with a palladium ion concentration of 1 mg / mL, then load the carrier loaded with the auxiliary agent in step (1) onto palladium nitrate, let it stand for 3 hours, then dry it under vacuum at 90°C for 4 hours, and calcine it under an inert gas atmosphere at 200°C for 14 hours to obtain the first sample.

[0042] (3) The first sample was reduced at 120°C in a first mixed gas of 5% hydrogen and 95% nitrogen for 4 hours to obtain the second sample.

[0043] (4) The second sample was reduced in a second mixed gas of 15% carbon monoxide and 85% nitrogen at 180°C for 4 hours to obtain the alloy single-atom catalyst.

[0044] The resulting alloy single-atom catalyst was used in the synthesis of dimethyl oxalate and dimethyl carbonate from carbon monoxide and methyl nitrite, with a space velocity of 3000 h⁻¹. -1 The concentration of methyl nitrite was 15%, the concentration of carbon monoxide was 30%, the reaction temperature was 120℃, the conversion rate of methyl nitrite was 83%, the ratio of dimethyl oxalate to dimethyl carbonate was 90 / 10, and the total selectivity of both was 99.6%.

[0045] Example 2

[0046] (1) Prepare a lanthanum nitrate solution with a concentration of 10 mg / mL. Load lanthanum nitrate onto a mixed support of 20% ReY molecular sieve and 80% γ-Al2O3, let stand for 2 hours, then dry at 110℃ for 2 hours, and calcine at 200℃ under an inert gas atmosphere for 9 hours.

[0047] (2) Prepare an aqueous solution of palladium nitrate with a palladium ion concentration of 1.5 mg / mL, then load the carrier loaded with the auxiliary agent in step (1) onto palladium nitrate, let it stand for 4 hours, then dry it under vacuum at 70°C for 4 hours, and calcine it under an inert gas atmosphere at 400°C for 4 hours to obtain the first sample.

[0048] (3) The first sample was reduced for 5 hours in a first mixed gas of 10% hydrogen and 90% nitrogen at 110°C to obtain the second sample.

[0049] (4) The second sample was reduced in a second mixed gas of 30% carbon monoxide and 70% nitrogen at 200°C for 2 hours to obtain the alloy single-atom catalyst.

[0050] The resulting alloy single-atom catalyst was used in the synthesis of dimethyl oxalate and dimethyl carbonate from carbon monoxide and methyl nitrite, with a space velocity of 3000 h⁻¹. -1 The concentrations of methyl nitrite and carbon monoxide were 15%, the reaction temperature was 115℃, the conversion rate of methyl nitrite was 80%, the ratio of dimethyl oxalate to dimethyl carbonate was 10 / 90, and the overall selectivity was 99.1%.

[0051] Example 3

[0052] (1) Prepare a scandium acetate solution with a concentration of 5 mg / mL. Load scandium acetate onto a mixed support of 40% 13X molecular sieve and 60% γ-Al2O3, let stand for 2 hours, then dry at 100℃ for 2 hours, and calcine at 300℃ under an inert gas atmosphere for 7 hours.

[0053] (2) Prepare an aqueous solution of palladium nitrate with a palladium ion concentration of 1 mg / mL, then load the carrier loaded with the auxiliary agent in step (1) onto palladium nitrate, let it stand for 2 hours, then dry it under vacuum at 100°C for 2 hours, and calcine it under an inert gas atmosphere at 150°C for 16 hours to obtain the first sample.

[0054] (3) The first sample was reduced at 150°C in a first mixed gas of 10% hydrogen and 90% nitrogen for 2 hours to obtain the second sample.

[0055] (4) The second sample was reduced in a second mixed gas of 10% carbon monoxide and 90% nitrogen at 200°C for 2 hours to obtain the alloy single-atom catalyst.

[0056] The resulting alloy single-atom catalyst was used in the synthesis of dimethyl oxalate and dimethyl carbonate from carbon monoxide and methyl nitrite, with a space velocity of 3000 h⁻¹. -1 The concentration of methyl nitrite was 15%, the concentration of carbon monoxide was 25%, the reaction temperature was 110℃, the conversion rate of methyl nitrite was 81%, the ratio of dimethyl oxalate to dimethyl carbonate was 80 / 20, and the total selectivity of both was 99.5%.

[0057] Example 4

[0058] (1) Prepare a yttrium nitrate solution with a concentration of 5 mg / mL. Load yttrium nitrate onto a mixed support of 15% SAPO-11 molecular sieve and 85% γ-Al2O3, let stand for 2 hours, then dry at 100℃ for 3 hours, and calcine at 350℃ under an inert gas atmosphere for 5 hours.

[0059] (2) Prepare an aqueous solution of palladium nitrate with a palladium ion concentration of 1.5 mg / mL, then load the carrier loaded with the auxiliary agent in step (1) onto palladium nitrate, let it stand for 2 hours, then dry it under vacuum at 85°C for 2 hours, and calcine it under an inert gas atmosphere at 350°C for 5 hours to obtain the first sample.

[0060] (3) The first sample was reduced at 115°C in a first mixed gas of 5% hydrogen and 95% nitrogen for 5 hours to obtain the second sample.

[0061] (4) The second sample was reduced at 170°C in a second mixed gas of 15% carbon monoxide and 85% nitrogen for 3 hours to obtain the alloy single-atom catalyst.

[0062] The resulting alloy single-atom catalyst was used in the synthesis of dimethyl oxalate and dimethyl carbonate from carbon monoxide and methyl nitrite, with a space velocity of 3000 h⁻¹. -1 The concentration of methyl nitrite was 15%, the concentration of carbon monoxide was 30%, the reaction temperature was 105℃, the conversion rate of methyl nitrite was 85%, the ratio of dimethyl oxalate to dimethyl carbonate was 75 / 25, and the overall selectivity of both was 99.8%.

[0063] Example 5

[0064] (1) Prepare a cerium chloride solution with a concentration of 10 mg / mL. Load cerium chloride onto a mixed support of 45% MCM-48 molecular sieve and 55% γ-Al2O3, let it stand for 3 hours, then dry it at 100℃ for 3 hours, and calcine it at 300℃ under an inert gas atmosphere for 8 hours.

[0065] (2) Prepare an aqueous solution of palladium nitrate with a palladium ion concentration of 0.5 mg / mL, then load the carrier loaded with the auxiliary agent in step (1) onto palladium nitrate, let it stand for 4 hours, then dry it under vacuum at 110°C for 2 hours, and calcine it under an inert gas atmosphere at 200°C for 12 hours to obtain the first sample.

[0066] (3) The first sample was reduced at 125°C in a first mixed gas of 10% hydrogen and 90% nitrogen for 4 hours to obtain the second sample.

[0067] (4) The second sample was reduced in a second mixed gas of 190°C, 25% carbon monoxide and 75% nitrogen for 3 hours to obtain the alloy single-atom catalyst.

[0068] The resulting alloy single-atom catalyst was used in the synthesis of dimethyl oxalate and dimethyl carbonate from carbon monoxide and methyl nitrite, with a space velocity of 3000 h⁻¹. -1The concentrations of methyl nitrite and carbon monoxide were 15%, the reaction temperature was 100℃, the conversion rate of methyl nitrite was 86%, the ratio of dimethyl oxalate to dimethyl carbonate was 50 / 50, and the overall selectivity was 99.3%.

[0069] Example 6

[0070] (1) Prepare a scandium nitrate solution with a concentration of 7.5 mg / mL. Load scandium nitrate onto a mixed support of 30% SBA-15 molecular sieve and 70% γ-Al2O3, let stand for 2 hours, then dry at 95°C for 2 hours, and calcine at 220°C under an inert gas atmosphere for 9 hours.

[0071] (2) Prepare an aqueous solution of palladium nitrate with a palladium ion concentration of 0.75 mg / mL, then load the carrier loaded with the auxiliary agent in step (1) onto palladium nitrate, let it stand for 2.5 hours, then dry it under vacuum at 80°C for 3.5 hours, and calcine it under an inert gas atmosphere at 300°C for 6 hours to obtain the first sample.

[0072] (3) The first sample was reduced in a first mixed gas of 10% hydrogen and 90% nitrogen at 100°C for 6 hours to obtain the second sample.

[0073] (4) The second sample was reduced in a second mixed gas of 15% carbon monoxide and 85% nitrogen at 200°C for 2 hours to obtain the alloy single-atom catalyst.

[0074] The resulting alloy single-atom catalyst was used in the synthesis of dimethyl oxalate and dimethyl carbonate from carbon monoxide and methyl nitrite, with a space velocity of 3000 h⁻¹. -1 The concentration of methyl nitrite was 15%, the concentration of carbon monoxide was 20%, the reaction temperature was 120℃, the conversion rate of methyl nitrite was 82%, the ratio of dimethyl oxalate to dimethyl carbonate was 60 / 40, and the total selectivity of both was 99.2%.

[0075] Comparative Example 1

[0076] (1) Prepare a cerium nitrate solution with a concentration of 5 mg / mL. Load cerium nitrate onto a mixed support of 30% ZSM-35 molecular sieve and 70% γ-Al2O3, let stand for 3 hours, then dry at 90°C for 3 hours, and calcine at 270°C under an inert gas atmosphere for 8 hours.

[0077] (2) Prepare an aqueous solution of palladium nitrate with a palladium ion concentration of 0.25 mg / mL, then load the carrier loaded with the auxiliary agent in step (1) onto palladium nitrate, let it stand for 3 hours, then dry it under vacuum at 90°C for 4 hours, and calcine it under an inert gas atmosphere at 180°C for 13 hours to obtain the first sample.

[0078] (3) The first sample was reduced at 120°C in a first mixed gas of 5% hydrogen and 95% nitrogen for 4 hours to obtain the second sample.

[0079] (4) The second sample was reduced in a second mixed gas of 15% carbon monoxide and 85% nitrogen at 180°C for 4 hours to obtain the alloy single-atom catalyst.

[0080] The resulting alloy single-atom catalyst was used in the synthesis of dimethyl oxalate and dimethyl carbonate from carbon monoxide and methyl nitrite, with a space velocity of 3000 h⁻¹. -1 The concentration of methyl nitrite was 15%, the concentration of carbon monoxide was 30%, the reaction temperature was 120℃, the conversion rate of methyl nitrite was 60%, the ratio of dimethyl oxalate to dimethyl carbonate was 80 / 20, and the total selectivity of the two was 82.5%.

[0081] Comparative Example 2

[0082] (1) Prepare a lanthanum nitrate solution with a concentration of 2 mg / mL, load lanthanum nitrate onto a mixed support of 20% ReY molecular sieve and 80% γ-Al2O3, let stand for 2 hours, then dry at 110℃ for 2 hours, and calcine at 200℃ under an inert gas atmosphere for 9 hours.

[0083] (2) Prepare an aqueous solution of palladium nitrate with a palladium ion concentration of 1.5 mg / mL, then load the carrier loaded with the auxiliary agent in step (1) onto palladium nitrate, let it stand for 4 hours, then dry it under vacuum at 70°C for 4 hours, and calcine it under an inert gas atmosphere at 400°C for 4 hours to obtain the first sample.

[0084] (3) The first sample was reduced at 200°C in a first mixed gas of 40% carbon monoxide and 60% nitrogen for 2 hours to obtain the alloy single-atom catalyst.

[0085] The resulting alloy single-atom catalyst was used in the synthesis of dimethyl oxalate and dimethyl carbonate from carbon monoxide and methyl nitrite, with a space velocity of 3000 h⁻¹. -1 The concentrations of methyl nitrite and carbon monoxide were 15%, the reaction temperature was 115℃, the conversion rate of methyl nitrite was 42%, the ratio of dimethyl oxalate to dimethyl carbonate was 30 / 70, and the total selectivity was 68.5%.

[0086] Comparative Example 3

[0087] (1) Prepare an aqueous solution of palladium tetraaminonitrate with a palladium ion concentration of 1 mg / mL, then load palladium tetraaminonitrate onto a mixed support of 40% 13X molecular sieve and 60% γ-Al2O3, let stand for 2 hours, then dry under vacuum at 100℃ for 2 hours, and calcine at 300℃ under an inert gas atmosphere for 7 hours to obtain the first sample.

[0088] (2) The first sample was reduced at 150°C in a first mixed gas of 10% hydrogen and 90% nitrogen for 2 hours to obtain the second sample.

[0089] (3) The second sample was reduced in a second mixed gas of 10% carbon monoxide and 90% nitrogen at 200°C for 2 hours to obtain the catalyst.

[0090] The resulting alloy single-atom catalyst was used in the synthesis of dimethyl oxalate and dimethyl carbonate from carbon monoxide and methyl nitrite, with a space velocity of 3000 h⁻¹. -1 The concentrations of methyl nitrite and carbon monoxide were 15%, the reaction temperature was 110℃, the conversion rate of methyl nitrite was 55%, the ratio of dimethyl oxalate to dimethyl carbonate was 45 / 55, and the total selectivity of both was 60.3%.

[0091] Comparative Example 4

[0092] (1) Prepare a cerium nitrate solution with a concentration of 5 mg / mL, load cerium nitrate onto the γ-Al2O3 support, let stand for 3 hours, then dry at 90°C for 3 hours, and calcine at 280°C in air atmosphere for 8 hours.

[0093] (2) Prepare an aqueous solution of palladium nitrate with a palladium ion concentration of 1 mg / mL, then load the carrier loaded with the auxiliary agent in step (1) onto palladium nitrate, let it stand for 3 hours, then dry it under vacuum at 90°C for 4 hours, and calcine it under air atmosphere at 320°C for 7 hours to obtain the first sample.

[0094] (3) The first sample was reduced at 120°C in a first mixed gas of 5% hydrogen and 95% nitrogen for 4 hours to obtain the second sample.

[0095] (4) The second sample was reduced in a second mixed gas of 15% carbon monoxide and 85% nitrogen at 180°C for 4 hours to obtain the alloy single-atom catalyst.

[0096] The resulting alloy single-atom catalyst was used in the synthesis of dimethyl oxalate and dimethyl carbonate from carbon monoxide and methyl nitrite, with a space velocity of 3000 h⁻¹. -1 The concentration of methyl nitrite was 15%, the concentration of carbon monoxide was 30%, the reaction temperature was 120℃, the conversion rate of methyl nitrite was 59%, the ratio of dimethyl oxalate to dimethyl carbonate was 83 / 17, and the total selectivity of the two was 63.8%.

[0097] The data from the above examples and comparative examples are shown in Table 1 below:

[0098]

[0099] The preferred embodiments disclosed above are merely illustrative of this application. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. These embodiments have been selected and specifically described in this specification to better explain the principles and practical applications of this application, thereby enabling those skilled in the art to better understand and utilize this application. This application is limited only by the claims and their full scope and equivalents.

[0100] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0101] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. The application of an alloy single-atom catalyst in the synthesis of dimethyl oxalate and dimethyl carbonate from gaseous carbon monoxide and methyl nitrite, characterized in that, The catalyst comprises a support formed by mixing γ-Al₂O₃ and a molecular sieve, an active component, and an auxiliary agent; wherein, based on the support, the active component is Pd, with a mass fraction of 0.05%-0.2%; the auxiliary agent is a rare earth metal, with a mass fraction of 0.5%-1%; the Pd in ​​the catalyst is a single atom dispersed in the rare earth metal, and Pd forms an alloy with the rare earth metal; the rare earth metal is one of lanthanum, cerium, yttrium, and scandium; the molecular sieve is selected from one of ZSM-35, ReY, 13X, SBA-15, SAPO-11, or MCM-48, and based on the support, the mass fraction of the molecular sieve is 15-50%. The method for preparing the catalyst includes the following steps: Prepare a rare earth metal salt solution with a concentration of 5-10 mg / mL. After the carrier is allowed to stand in the rare earth metal salt solution for 2-4 hours, it is dried and then calcined at 150-400℃ in an inert gas atmosphere for 4-16 hours. Prepare an aqueous solution of palladium source with a palladium ion concentration of 0.5-2 mg / mL, load the carrier with the completed auxiliary agent onto palladium, let it stand for 2-4 hours and then dry it, and then calcine it at 150-400℃ in an inert gas atmosphere for 4-16 hours to obtain the first sample; The first sample was reduced at 100-150°C in a first mixed gas of hydrogen and nitrogen for 2-6 hours to obtain the second sample. The second sample was reduced at 150-200°C in a second mixed gas of carbon monoxide and nitrogen for 2-6 hours to obtain the catalyst.

2. The application according to claim 1, characterized in that, The first mixture contains 5-10% hydrogen by volume, with the remainder being nitrogen.

3. The application according to claim 1, characterized in that, The second mixture contains 10-40% carbon monoxide by volume, with the remainder being nitrogen.

4. The application according to claim 1, characterized in that, The diameter of the carrier is 3-5 mm.

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