Catalyst for co-production of dimethyl oxalate and dimethyl carbonate and preparation method thereof

Abstract

The invention relates to the technical field of preparation of chemical catalysts, in particular to a catalyst for co-production of dimethyl oxalate and dimethyl carbonate from carbon monoxide and methyl nitrite and a preparation method of the catalyst. The catalyst comprises a carrier, an active component and an auxiliary agent, wherein the carrier is nano ore crystal, the active component is precious metal palladium, the mass fraction of the active component in the carrier is 0.02%-0.05%, the auxiliary agent is alkali metal, and the mass fraction of the auxiliary agent in the carrier is 0.1%-2.0%; pd in the catalyst can be combined with the alkali metal additive and is uniformly distributed on the surface of the carrier. The co-production catalyst is suitable for the reaction of synthesizing dimethyl oxalate and dimethyl carbonate from gas-phase carbon monoxide and methyl nitrite, and has the advantages of high target product selectivity, high raw material conversion rate, low cost, long service life and the like.

Description

Technical Field

[0001] This application relates to the field of chemical catalyst preparation technology, and in particular to a catalyst and preparation method for the co-production of dimethyl oxalate and dimethyl carbonate from carbon monoxide and methyl nitrite. Background Technology

[0002] Dimethyl oxalate and dimethyl carbonate are both common and essential chemical raw materials. Dimethyl oxalate can be used as an intermediate in the synthesis of certain pharmaceuticals and fine chemicals, in the production of dyes, emulsifiers, or mineral flotation agents, and as a plasticizer to improve the flexibility and processing properties of plastics, among other applications. Dimethyl carbonate is a "green" solvent due to its excellent solubility, low toxicity, high evaporation temperature, and fast evaporation rate, and is commonly used in the production of paints, coatings, pesticides, and engineering plastics. Furthermore, dimethyl carbonate can be used as a gasoline additive to increase the octane rating of gasoline and reduce harmful emissions from automobile exhaust. In addition, dimethyl carbonate can be used in the electrolyte of lithium-ion batteries, demonstrating broad application prospects in both industry and daily life.

[0003] In industrial production, both dimethyl oxalate and dimethyl carbonate can be prepared from coal-based syngas under certain catalytic conditions. Patent CN 114887648 B discloses a "Preparation Method of a Catalyst for the Co-production of Dimethyl Oxalate from the Carbonylation of Methyl Nitrite," but the noble metal catalyst in this invention has a high mass fraction of precious metals, resulting in high cost and hindering mass industrial production. Patent CN 110227451 A discloses a "Catalyst for the Co-production of Dimethyl Oxalate and Dimethyl Carbonate," but the catalyst in this invention uses a complex support, requires high-temperature treatment above 400℃, has high energy consumption, and also has high production costs.

[0004] To address the above issues, this invention discloses a highly active, stable, and low-cost catalyst for the co-production of dimethyl oxalate and dimethyl carbonate. This catalyst support has a small pore size, a large specific surface area, and a particle size suitable for industrial applications. It can improve the utilization rate of the active metal palladium and the auxiliary metal, ultimately increasing the conversion rate of the raw materials and the selectivity of the target product. It achieves a wide range of product space-time yield distributions, which is conducive to the future industrialization of the co-production technology of dimethyl oxalate and dimethyl carbonate. Summary of the Invention

[0005] The purpose of this invention is to provide a low-cost, easily industrialized catalyst for the co-production of dimethyl oxalate and dimethyl carbonate, and a method for its preparation.

[0006] The catalyst for the co-production of dimethyl oxalate and dimethyl carbonate provided by this invention uses nano-mineral crystals as a support and does not require...

[0007] High-temperature roasting results in a precious metal mass fraction of 0.02-0.05%, offering advantages such as low cost, energy efficiency, environmental friendliness, and ease of industrialization.

[0008] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0009] A catalyst for the co-production of dimethyl oxalate and dimethyl carbonate, characterized in that the catalyst comprises a support, an active component, and an auxiliary agent; the support is a nano-mineral crystal; the active component is the noble metal palladium, with a mass fraction of 0.02%-0.05% in the support; and the auxiliary agent is an alkali metal or alkaline earth metal element, with a mass fraction of 0.1%-2.0% in the support.

[0010] The palladium in the catalyst and the auxiliary metal elements are uniformly distributed in the nano-mineral crystal carrier.

[0011] The preparation method of the co-production catalyst supported on the noble metal palladium mainly utilizes a vacuum impregnation method to support the active metal and auxiliary metal elements, including the following steps:

[0012] 1) Dissolve the noble metal precursor in one or more of the following: water, organic acid, inorganic acid, and organic solvent, and stir until homogeneous to obtain a palladium source solution with a palladium ion concentration of 5-50 mg / mL.

[0013] 2) Immerse the nano-mineral crystal carrier in one or more mixed solvents such as pure water, methanol, ethanol, acetone, and acetonitrile for 1-24 hours, then filter, wash, and air dry to obtain purified nano-mineral crystals.

[0014] 3) Place the purified nano-mineral crystals into a vacuum drying oven and maintain the conditions of vacuum degree 3-100 par and temperature 80-200℃ for 1-24 hours;

[0015] 4) Prepare a solution of alkali metal salt or alkaline earth metal salt with a concentration of 10-200 mg / mL, and load it onto the nano-mineral crystal carrier treated in step 3) under vacuum conditions, with a mass fraction of 0.1%-2.0%; then let it stand for 1-8 h and dry it at 80-200℃ for 1-24 h, take out the nano-mineral crystal loaded with the auxiliary metal, and calcine it in an inert gas atmosphere at 150-300℃ for 1-12 h;

[0016] 5) Load the noble metal precursor solution prepared in step 1) onto the nano-mineral crystal carrier loaded with additives after step 4) under vacuum conditions, with a mass fraction of 0.02%-0.05%; let stand for 1-8 h, and then dry for 1-24 h at a temperature of 80-200℃ and a vacuum of 3-100 par to obtain nano-mineral crystals loaded with noble metals and additive metals;

[0017] 6) The nano-mineral crystals loaded with noble metals and additives obtained in step 5) are placed in a flowing hydrogen / helium mixture for reduction treatment. The volume ratio of hydrogen to helium is in the range of 1:1 to 9. The temperature is increased from room temperature to 80-300℃ at a heating rate of 0.5-5.0℃ / min and held for 1-12 h. After cooling to room temperature, the nano-mineral crystal catalyst is obtained.

[0018] As a preferred embodiment, the noble metal precursor in step 1) is one of palladium dichloride, palladium acetate, palladium nitrate, sodium tetrachloropalladium, dichlorotetraamminepalladium, potassium chloropalladium, or palladium acetylacetonate.

[0019] The carrier nanocrystals mentioned in step 2) are a natural mineral composed of a mixture of sepiolite, attapulgite, diatomite, and other materials. They have a particle size of 3-5 mm, pore sizes generally ranging from 0.3-10.0 nm, and a specific surface area of ​​800-1200 m². 2 Between / g.

[0020] As a preferred option, the vacuum level in step 3) is 10-80 par, and it is maintained for 2-12 h.

[0021] As a preferred option, the vacuum level in step 4) is 3-100 par.

[0022] As a preferred embodiment, the alkali metal salt in step 4) includes one or more of sodium carbonate, sodium chloride, sodium nitrate, potassium chloride, potassium carbonate, sodium sulfate, potassium sulfate, and potassium nitrate, and the alkaline earth metal salt includes one or more of magnesium chloride, magnesium nitrate, magnesium sulfate, calcium chloride, and calcium nitrate.

[0023] As a preferred option, the inert gas in step 4) includes one or a combination of nitrogen, argon, and helium.

[0024] As a preferred embodiment, in step 5), the mass fraction of palladium loaded on the carrier is 0.02%-0.05%, and the mass fraction of the loading auxiliary metal is 0.1%-2.0%.

[0025] As a preferred option, the vacuum conditions in step 5) are a vacuum degree of 20-100 par, and after loading the noble metal palladium, it is left to stand for 2-6 hours.

[0026] The nano-mineral crystal noble metal catalyst described in this invention is applied to the reaction of preparing dimethyl oxalate and dimethyl carbonate from syngas.

[0027] Besides the influence of the supported additives and active metals, the reduction process of the nanocrystalline noble metal catalyst is the key step determining the yield and relative distribution ratio of the products dimethyl oxalate and dimethyl carbonate. Since the supported additives and active metal elements are both divalent or higher, after reduction with a hydrogen / helium mixture, the high-valence metal elements are converted to low-valence states. According to research results, divalent palladium is favorable for the synthesis of dimethyl carbonate, while zero-valence palladium is favorable for the synthesis of dimethyl oxalate. Therefore, controlling the valence state of the noble metal has a direct impact on the co-production of dimethyl oxalate and dimethyl carbonate. The nanocrystalline palladium metal catalyst prepared in this invention exhibits excellent catalytic performance in the co-production of dimethyl oxalate and dimethyl carbonate from carbon monoxide and methyl nitrite, with a CO conversion rate greater than 85%, a total selectivity for dimethyl carbonate and dimethyl oxalate greater than 98%, and can operate stably for more than 1000 h.

[0028] The nano-mineral crystal catalyst of this invention uses nano-mineral crystals as a carrier. These nano-mineral crystals are non-metallic natural minerals formed from substances such as sepiolite, attapulgite, and diatomaceous earth. They are typical porous mineral adsorbent materials with high porosity and pore sizes of only 0.3-10.0 nm, and a specific surface area as high as 800-1200 m². 2 / g is an excellent catalyst support material. Vacuum impregnation with ethanol and water effectively removes impurities such as air and fine particulate matter adsorbed on the surface and within the pores of the nano-mineral crystals. Then, additive elements and active metal elements are loaded, resulting in a better impregnation effect in the precursor solution, thereby improving the effective utilization rate of the additive and active metal elements. In the catalyst preparation process, the nano-mineral crystals do not require high-temperature calcination or alkaline treatment, making it more energy-efficient, environmentally friendly, and lower in cost, suitable for industrial production.

[0029] Compared with the prior art, the catalyst for the co-production of dimethyl oxalate and dimethyl carbonate of the present invention has the following significant features:

[0030] (1) The active component palladium content of the nano-mineral crystal noble metal catalyst in this invention is relatively low, only 0.02-0.05% (mass). Compared with the palladium loading of 0.1~2.5% in CN 114887648B, the cost of the catalyst can be greatly reduced and the economic benefits of the production process of dimethyl oxalate and dimethyl carbonate can be improved.

[0031] (2) The catalyst for the co-production of dimethyl oxalate and dimethyl carbonate of the present invention is a nano-mineral crystal catalyst supported with noble metals. It has the characteristics of high activity, high stability, low cost, high conversion rate and high selectivity. It is also a chlorine-free catalyst, which is especially suitable for the reaction of carbon monoxide and methyl nitrite to co-produce dimethyl oxalate and dimethyl carbonate. Attached Figure Description

[0032] Figure 1 Transmission electron microscope image of the catalyst prepared in Example 1.

[0033] Figure 2 Scanning electron microscope image of the catalyst prepared in Example 1 and EDS spectrum of Pd.

[0034] Figure 3 Scanning electron microscope image of the catalyst prepared in Example 2.

[0035] Figure 4 Chromatogram of exhaust gas in Example 5.

[0036] Figure 5 Chromatogram of the sample after methanol dissolution in Example 5. Detailed Implementation

[0037] To facilitate understanding of the present invention, the following embodiments are provided. These embodiments are merely illustrative and should not be considered as specific limitations of the invention. Because the present invention can also be described and explained through other solutions that do not depart from its technical features, all modifications within the scope of the present invention or its equivalents should fall within the protection scope of the present invention.

[0038] The present invention will be further illustrated below with reference to embodiments, comparative examples, and application examples.

[0039] Example 1

[0040] (1) Select nano mineral crystals as carriers, soak the nano mineral crystals in methanol aqueous solution for 12 h, then filter, wash with pure water, and air dry to obtain purified nano mineral crystals;

[0041] (2) Place the purified nano-mineral crystals into a vacuum drying oven and keep them at 120°C for 12 hours under a vacuum of 30 par.

[0042] (3) Prepare a sodium carbonate solution with a concentration of 10.0 mg / mL and load it onto the nano-mineral carrier in step 2) under vacuum conditions of 10 par. The mass fraction of sodium is 0.1%. After standing for 4 h, dry at 80℃ for 4 h. Then take out the nano-mineral carrier loaded with sodium additive and calcine it at 150℃ in an inert gas atmosphere for 6 h.

[0043] (4) Prepare a palladium acetate solution with a palladium ion concentration of 5.0 mg / ml. Load the nano mineral crystal support loaded with additives in step (3) with palladium acetate under vacuum of 20 par, so that the theoretical mass content of palladium in the nano mineral crystal support is 0.02%. Then let it stand for 4 h and dry it at 200℃ for 12 h to obtain nano mineral crystals loaded with noble metal precursors and additives.

[0044] (5) The supported additive and palladium nanocrystals obtained in step (4) are placed in a flowing 10% hydrogen / 90% helium mixture and reduced at 150°C for 8 h. After cooling to room temperature, they are removed to obtain the palladium-based nanocrystal catalyst. The morphology and particle size of the catalyst are as follows: Figure 1 , 2 As shown.

[0045] Example 2

[0046] (1) Select nano-mineral crystals as carriers, soak the nano-mineral crystals in an ethanol aqueous solution for 6 h, then filter, wash with pure water, and air dry to obtain purified nano-mineral crystals.

[0047] (2) Place the purified nano-mineral crystals into a vacuum drying oven and keep them at 120°C for 12 hours under a vacuum of 50 par.

[0048] (3) Prepare a potassium nitrate solution with a concentration of 100.0 mg / mL, and load it onto the nanoparticles from step (2) under vacuum conditions of 30 ppm.

[0049] The potassium mass fraction on the mineral crystal carrier is 0.5%; after standing for 3 h, it is dried at 150℃ for 24 h, and then the nano-mineral crystal loaded with potassium additive is taken out and calcined at 200℃ in an inert gas atmosphere for 3 h.

[0050] (4) Prepare a sodium tetrachloropalladium solution with a palladium ion concentration of 20.0 mg / ml. Load the nano-mineral crystal support loaded with additives in step (3) with palladium tetrachlorodium under vacuum of 40 par, so that the theoretical mass content of palladium in the nano-mineral crystal support is 0.04%. Then let it stand for 4 h and dry it at 150℃ for 12 h to obtain nano-mineral crystals loaded with noble metal precursors and additives.

[0051] (5) The supported additive and palladium nanocrystals obtained in step (4) are placed in a flowing 5% hydrogen / 95% helium mixture and reduced at 200°C for 4 h. After cooling to room temperature, they are removed to obtain the palladium-based nanocrystal catalyst. The surface morphology of the catalyst is as follows: Figure 3 As shown.

[0052] Example 3

[0053] (1) Select nano-mineral crystals as carriers, soak the nano-mineral crystals in an ethanol aqueous solution for 6 h, then filter, wash with pure water, and air dry to obtain purified nano-mineral crystals.

[0054] (2) Place the purified nano-mineral crystals into a vacuum drying oven and keep them at 80 par and 100°C for 5 h.

[0055] (3) Prepare a sodium carbonate solution with a concentration of 10.0 mg / mL and load it onto the nano-mineral carrier in step 2) under vacuum conditions of 10 par. The mass fraction of sodium is 1.5%. After standing for 4 h, dry at 120℃ for 4 h. Then take out the nano-mineral carrier loaded with sodium additive and calcine it at 300℃ in an inert gas atmosphere for 6 h.

[0056] (4) Prepare a sodium tetrachloropalladium solution with a palladium ion concentration of 50.0 mg / ml. Load the nano-mineral crystal support loaded with additives in step (3) with palladium tetrachlorodium under vacuum of 40 par, so that the theoretical mass content of palladium in the nano-mineral crystal support is 0.05%. Then let it stand for 4 h and dry it at 150℃ for 12 h to obtain nano-mineral crystals loaded with noble metal precursors and additives.

[0057] (5) The loaded additive and palladium nanocrystals obtained in step 4) are placed in a flowing 5% hydrogen / 95% helium mixture and reduced at 190°C for 6 hours. After cooling to room temperature, they are taken out to obtain the palladium-based nanocrystal catalyst.

[0058] Example 4

[0059] (1) Select nano mineral crystals as carriers, soak the nano mineral crystals in acetonitrile solution for 8 h, then filter, wash with pure water, and air dry to obtain purified nano mineral crystals;

[0060] (2) Place the purified nano-mineral crystals into a vacuum drying oven and keep them at 80 par and 100°C for 5 h.

[0061] (3) Prepare a magnesium chloride solution with a concentration of 50.0 mg / mL, load it onto a vacuum-dried nano-mineral carrier with a magnesium mass fraction of 1.0%; let it stand for 2 h and then dry it at 180℃ for 8 h. Then take out the nano-mineral carrier loaded with magnesium additive and calcine it at 200℃ in an inert gas atmosphere for 2 h.

[0062] (4) Prepare a palladium dichloride solution with a palladium ion concentration of 35.0 mg / ml. Load the nanocrystalline mineral support with the additives loaded in step (3) with palladium dichloride under vacuum conditions of 30 ppm, so that the theoretical mass content of palladium in the nanocrystalline mineral support is _____.

[0063] 0.03%, then let stand for 4 h, and dry at 200℃ for 12 h to obtain nano-mineral crystals loaded with noble metal precursors and additives;

[0064] (5) The loaded additive and palladium nanocrystals obtained in step (4) are placed in a flowing 25% hydrogen / 75% helium mixture and reduced at 220°C for 5 h. After cooling to room temperature, they are taken out to obtain the palladium-based nanocrystal catalyst.

[0065] Example 5

[0066] (1) Select nano-mineral crystals as carriers, soak the nano-mineral crystals in acetone solution for 10 h, then filter, wash with pure water, and air dry to obtain purified nano-mineral crystals.

[0067] (2) Place the purified nano-mineral crystals into a vacuum drying oven and keep them at a vacuum of 50 par and 80°C for 8 hours.

[0068] (3) Prepare a calcium nitrate solution with a concentration of 200.0 mg / mL and load it onto the nano-mineral carrier of step (2) under vacuum conditions of 40 par. The mass fraction of calcium is 2.0%. After standing for 2 h, dry at 200℃ for 15 h. Then take out the nano-mineral carrier loaded with calcium additive and calcine it at 260℃ in an inert gas atmosphere for 4 h.

[0069] (4) Prepare a palladium nitrate solution with a palladium ion concentration of 40.0 mg / ml. Load the nano-mineral crystal support loaded with additives in step (3) with palladium nitrate under vacuum of 50 par, so that the theoretical mass content of palladium in the nano-mineral crystal support is 0.045%. Then let it stand for 4 h and dry it at 180℃ for 10 h to obtain nano-mineral crystals loaded with noble metal precursors and additives.

[0070] (5) The loaded additive and palladium nanocrystals obtained in step (4) are placed in a flowing 20% ​​hydrogen / 80% helium mixture and reduced at 180°C for 8 h. After cooling to room temperature, they are taken out to obtain the palladium-based nanocrystal catalyst.

[0071] Comparative Example 1

[0072] (1) Select commercially purchased ZSM molecular sieves as carriers with a particle size of 3-5 mm, soak them in ethanol solution, and then filter, wash, air dry, and vacuum dry to obtain purified ZSM molecular sieve carriers.

[0073] (2) Prepare a sodium chloride solution with a concentration of 20.0 mg / ml, load it onto the purified ZSM carrier under vacuum of 20 ppm, with a sodium mass fraction of 1.0%; then dry at 150 ℃ for 12 h and calcine at 200 ℃ for 4 h;

[0074] (3) Prepare a palladium chloride solution with a palladium ion concentration of 30.0 mg / ml and load it onto the ZSM support after step (2) under vacuum of 30 ppm, so that the theoretical mass content of palladium in the ZSM support is 2%, and obtain a ZSM catalyst loaded with palladium precursor and sodium auxiliary agent.

[0075] (4) The catalyst obtained in step (3) is placed in a flowing mixture of 15% hydrogen / 85% helium and reduced at 200°C for 8 h. After cooling to room temperature, it is taken out to obtain the palladium-based ZSM catalyst.

[0076] Comparative Example 2

[0077] (1) Select commercially available NaY molecular sieve as the carrier, and follow the same steps as in Comparative Example 1 (1).

[0078] (2) Same as step (2) in Comparative Example 1;

[0079] (3) Same as step (3) in Comparative Example 1;

[0080] (4) Same as step (4) in Comparative Example 1.

[0081] Comparative Example 3

[0082] (1) Commercially purchased α-Al2O3 was selected as the carrier, and the remaining steps were the same as step (1) in Comparative Example 1.

[0083] (2) Same as step (2) in Comparative Example 1;

[0084] (3) Same as step (3) in Comparative Example 1;

[0085] (4) Same as step (4) in Comparative Example 1.

[0086] Application examples

[0087] The nanocrystalline mineral catalysts prepared in Examples 1-5 and Comparative Examples 1-3 were used in the synthesis of dimethyl oxalate and dimethyl carbonate from carbon monoxide and methyl nitrite. Catalyst activity was evaluated in a continuous-flow fixed-bed reactor (tubular reactor, 50.0 cm long, 10.0 mm inner diameter, 0.3 g catalyst charge), at a reaction temperature of 120°C. The feed gas composition consisted of carbon monoxide, methyl nitrite, and nitrogen in a flow ratio of 2:3:15. The products were directly analyzed using online chromatography. The conversion rates of carbon monoxide and methyl nitrite, the main products dimethyl oxalate and dimethyl carbonate, and the byproduct methyl formate were calculated based on the selectivity of carbon monoxide.

[0088] Dimethyl oxalate (DMO), dimethyl carbonate (DMC), methyl formate (MF), methyl nitrite (MN), and methyl acetal (DMM) are all used in this study. Table 1 shows that the CO conversion rate and total selectivity of the nano-mineral supported palladium and additive catalysts prepared in Examples 1-5 are higher than those of the catalysts supported on palladium and additives in Comparative Examples 1-3. This indicates that the palladium-supported nano-mineral catalyst prepared in this application has relatively high main product selectivity and feed conversion rate in the reaction of carbon monoxide and methyl nitrite to co-produce dimethyl oxalate and dimethyl carbonate, meaning that the catalyst prepared in this application has high activity. In Example 5, the tail gas and the sampled product were dissolved in methanol and analyzed by gas chromatography. The chromatogram results are shown below. Figure 4 , 5 As shown in Tables 2 and 3, the specific test results are as follows: DMO and DMC are the main products in the overall product, and the total selectivity of the two is higher than 97%.

[0089] Table 1 Catalytic performance of catalysts in Examples 1-5 and Comparative Examples 1-3

[0090] catalyst CO conversion rate % DMO / CO selectivity % DMC / CO selectivity % MF / MN selectivity % DMM / MN selectivity % Example 1 78.5 82.3 11.5 3.0 3.2 Example 2 71.2 50.4 45.8 2.6 1.2 Example 3 88.2 59.5 37.8 1.5 1.2 Example 4 86.1 65.2 26.4 6.1 2.3 Example 5 83.3 75.8 18.1 5.1 1.0 Comparative Example 1 48.9 48.0 24.7 22.2 5.1 Comparative Example 2 56.7 45.5 30.6 15.9 8.0 Comparative Example 3 45.3 50.9 20.5 21.9 7.7

[0091] Table 2. Results of tail gas chromatography detection in Example 5

[0092] name Retention time (min) Peak area Normalized content (%) Methyl nitrite 4.298 28098.884 11.73 Methyl acetal 5.449 243.610 0.02 Methyl formate 5.684 1182.125 0.24 carbon dioxide 6.056 368.751 0.13 methanol 7.443 5063. 955 1.19 dimethyl carbonate 8.917 3397.704 0.62 Nitrogen 10.409 182128.575 73.85 Nitric oxide 11.601 12926.809 7.18 carbon monoxide 12.111 11463.992 4.92 dimethyl oxalate 14.868 556.826 0.12 sum 100.00

[0093] Table 3. Chromatographic detection results of the sample after methanol dissolution in Example 5

[0094] Peak Name Retention time (min) Peak area Relative sample amount (%) methanol 2.568 464.3332 89.59 Methyl formate 2.683 0.0855 0.03 dimethyl carbonate 5.362 0.4085 0.16 dimethyl oxalate 9.938 30.2423 10.22 sum 100.00

[0095] Stability evaluation of the catalysts revealed that the catalysts prepared in Examples 1-5 could generally operate stably for over 1000 hours, with relatively stable CO conversion, DMO, and DMC selectivity. Notably, the overall selectivity for DMO and DMC in these examples reached a maximum of 97.3%, and the distribution ratio of DMO and DMC could be adjusted as needed. Therefore, the nanocrystalline mineral-supported noble metal catalyst prepared in this application exhibits high activity and stability.

[0096] Based on the results of the above examples and comparative examples, the following conclusions can be drawn: The nano-mineral crystal supported noble metal catalyst prepared by the present invention is a highly active, highly stable, low-cost, high-conversion, and highly selective catalyst that is also chlorine-free. It is particularly suitable for the reaction of gaseous carbon monoxide and methyl nitrite co-producing dimethyl oxalate and dimethyl carbonate.

Claims

1. A catalyst for the co-production of dimethyl oxalate and dimethyl carbonate, characterized in that, The catalyst comprises a support, an active component, and an additive; the support is a nano-mineral crystal, the active component is the noble metal palladium, and its mass fraction in the support is 0.02%-0.05%; the additive is an alkali metal or alkaline earth metal element, and its mass fraction in the support is 0.1%-2.0%.

2. The method for preparing the catalyst according to claim 1, characterized in that, Specifically, the following steps are included: 1) Dissolve the noble metal precursor in one or more of the following: water, organic acid, inorganic acid, and organic solvent, and stir until homogeneous to obtain a palladium source solution with a palladium ion concentration of 5-50 mg / mL. 2) Immerse the nano-mineral crystal carrier in one or more mixed solvents such as pure water, methanol, ethanol, acetone, and acetonitrile for 1-24 hours, then filter, wash, and air dry to obtain purified nano-mineral crystals. 3) Place the purified nano-mineral crystals into a vacuum drying oven and maintain the conditions of vacuum degree 3-100 par and temperature 80-200℃ for 1-24 hours; 4) Prepare a solution of alkali metal salt or alkaline earth metal salt with a concentration of 10-200 mg / mL, and load it onto the nano-mineral crystal carrier treated in step 3) under vacuum conditions, with a mass fraction of 0.1%-2.0%; then let it stand for 1-8 h and dry it at 80-200℃ for 1-24 h, take out the nano-mineral crystal loaded with the auxiliary metal, and calcine it in an inert gas atmosphere at 150-300℃ for 1-12 h; 5) Load the noble metal precursor solution prepared in step 1) onto the nano-mineral crystal carrier loaded with additives after step 4) under vacuum conditions, with a mass fraction of 0.02%-0.05%; let stand for 1-8 h, and then dry for 1-24 h at a temperature of 80-200℃ and a vacuum of 3-100 par to obtain nano-mineral crystals loaded with noble metals and additive metals; 6) The nano-mineral crystals loaded with noble metals and additives obtained in step 5) are placed in a flowing hydrogen / helium mixture for reduction treatment. The volume ratio of hydrogen to helium is in the range of 1:1 to 9. The temperature is increased from room temperature to 80-300℃ at a heating rate of 0.5-5.0℃ / min and held for 1-12 h. After cooling to room temperature, the nano-mineral crystal catalyst is obtained.

3. The preparation method according to claim 2, characterized in that, The noble metal precursor in step 1) is one of palladium dichloride, palladium acetate, palladium nitrate, sodium tetrachloropalladium, dichlorotetraamminepalladium, potassium chloropalladium, or palladium acetylacetonate.

4. The preparation method according to claim 2, characterized in that, The vacuum level in step 3) is 10-80 par, and it is maintained for 2-12 hours. The vacuum level in step 4) is 3-100 par.

5. The preparation method according to claim 2, characterized in that, The alkali metal salts in step 4) include one or more of sodium carbonate, sodium chloride, sodium nitrate, potassium chloride, potassium carbonate, sodium sulfate, potassium sulfate, and potassium nitrate, and the alkaline earth metal salts include one or more of magnesium chloride, magnesium nitrate, magnesium sulfate, calcium chloride, and calcium nitrate.

6. The preparation method according to claim 2, characterized in that, The vacuum conditions in step 5) are a vacuum degree of 20-100 par, and after loading palladium, the system is left to stand for 2-6 hours.

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