Cu-supported Y molecular sieve catalysts, their preparation methods and applications; methods for preparing dimethyl carbonate using carbon dioxide.

Abstract

This invention provides a Cu-supported Y molecular sieve catalyst, its preparation method and application, and a method for preparing dimethyl carbonate using carbon dioxide. The method for preparing dimethyl carbonate using carbon dioxide includes: reacting carbon dioxide and dimethyl ether in the presence of a copper-containing catalyst to produce dimethyl carbonate; the copper-containing catalyst includes a Y molecular sieve and copper supported on the Y molecular sieve. This invention uses a copper-supported Y molecular sieve to catalyze the reaction of dimethyl ether with carbon dioxide. The reaction conditions are mild, the reaction product contains only dimethyl carbonate, with no byproducts generated, achieving 100% atom economy. It utilizes the greenhouse gas CO2, reducing environmental pollution. Furthermore, since no water byproduct is generated in the reaction, the adverse effects of water on catalyst activity and dimethyl carbonate selectivity are effectively avoided, significantly improving the yield of dimethyl carbonate. The operation is simple, the process conditions are mild, reducing costs and improving industrial production efficiency.

Description

Technical Field

[0001] This invention belongs to the field of dimethyl carbonate synthesis technology, specifically relating to a Cu-supported Y molecular sieve catalyst, its preparation method and application, and a method for preparing dimethyl carbonate using carbon dioxide. Background Technology

[0002] Dimethyl carbonate (DMC) is a low-toxicity, environmentally friendly, and widely used chemical raw material. It is also an important intermediate in organic synthesis, with the structural formula CH3O-CO-OCH3. Its molecular structure contains various functional groups, such as -CH3, -OCH3, -CO-, and -CO-OCH3, making it widely applicable in organic synthesis reactions such as carbonylation, methylation, methoxylation, and carbonyl methylation. At room temperature, DMC is a colorless, transparent, slightly irritating, and sparingly soluble flammable liquid, but it is miscible with most organic solvents, including alcohols, ethers, and ketones, as well as acids and bases. In production, it is characterized by safety, convenience, low pollution, and ease of transportation.

[0003] The synthesis of dimethyl carbonate (DMC) includes many technical routes such as the phosgene method, transesterification method, oxidative carbonylation method, urea method, dimethyl oxalate decarbonylation method, and direct methanol-carbon dioxide method. Current research mainly focuses on the direct synthesis of DMC from methanol and carbon dioxide. The direct methanol-carbon dioxide method, using CO2 as a raw material, is a green and sustainable route for synthesizing DMC, not only utilizing CO2 resources but also achieving carbon emission reduction. CN113620806A discloses a method for preparing DMC by reacting methanol and carbon dioxide under a catalyst; wherein the catalyst contains SnO2 and at least one of CeO2 and ZrO2. However, this method generates water during the reaction, which decomposes DMC and reduces the activity of the catalyst. Furthermore, the tin dioxide, cerium dioxide, and zirconium dioxide used are expensive, hindering the large-scale application of the catalyst.

[0004] Compared to the direct method using methanol and carbon dioxide, the direct synthesis of DMC from dimethyl ether and carbon dioxide is an atom-economical reaction, offering dual economic and environmental advantages in today's increasingly "green chemical" environment. However, this reaction is thermodynamically non-spontaneous; therefore, current research needs to develop a suitable method to make this technical route feasible. Chinese patent CN102964254B discloses a process for synthesizing dimethyl carbonate from dimethyl ether and carbon dioxide, using MgO-ZnO-composite rare earth oxides as a catalyst. However, the method disclosed in this patent requires supercritical CO2 as a raw material, resulting in high reaction pressure, demanding equipment requirements, and operational difficulties. Summary of the Invention

[0005] Based on the above analysis, the present invention aims to provide a Cu-supported Y molecular sieve catalyst, its preparation method and application, and a method for preparing dimethyl carbonate using carbon dioxide, in order to solve the technical problem of harsh reaction conditions in the prior art for the synthesis of dimethyl carbonate from dimethyl ether and carbon dioxide.

[0006] The objective of this invention is mainly achieved through the following technical solutions.

[0007] In a first aspect, the present invention provides a method for preparing a Cu-supported Y molecular sieve catalyst, comprising: obtaining a mixture comprising a first silicon source, a first aluminum source, an alkali source and water, aging it to obtain a directing agent; then mixing the directing agent, a second silicon source, a second aluminum source and water to obtain a synthetic gel; crystallizing the synthetic gel, then adding a copper precursor solution, stirring, filtering, drying and calcining to obtain the catalyst.

[0008] The Cu-supported Y molecular sieve catalyst prepared by the method provided by this invention exhibits a more pronounced synergistic effect between the metal atoms and the active centers of the molecular sieve. When used in the reaction of carbon dioxide and dimethyl ether to prepare dimethyl carbonate, it can further improve the yield of dimethyl carbonate. Furthermore, the preparation method is simple, low-cost, and conducive to industrial application.

[0009] According to some embodiments of the present invention, the first silicon source comprises water glass and / or sodium silicate.

[0010] In this invention, the first aluminum source is preferably a highly active aluminum source. According to some embodiments of the invention, the first aluminum source comprises sodium aluminate.

[0011] According to some embodiments of the present invention, the alkali source includes at least one of sodium hydroxide and potassium hydroxide.

[0012] According to some embodiments of the present invention, the second silicon source comprises water glass and / or sodium silicate.

[0013] According to some embodiments of the present invention, the second aluminum source includes at least one of sodium aluminate, aluminum sulfate, and aluminum nitrate.

[0014] According to some embodiments of the present invention, the molar composition of the components contained in the synthetic gel is SiO2:Al2O3:OH. - : H2O=1: (5~12): (3~8): (100~200).

[0015] In this invention, the SiO2 contained in the synthetic gel is provided by a first silicon source and a second silicon source, the Al2O3 is provided by a first aluminum source and a second aluminum source, and the OH... - OH in the alkali source representing the preparation of synthetic gel -The molar amount.

[0016] According to some embodiments of the present invention, the aging conditions include: an aging temperature of 15–40°C and an aging time of 3–24 h, preferably 3–10 h.

[0017] According to some embodiments of the present invention, the conditions for the crystallization treatment include: a crystallization temperature of 90–100°C and a crystallization time of 20–48 h.

[0018] According to some embodiments of the present invention, the calcination conditions include: a calcination temperature of 200–300°C and a calcination time of 1–4 hours.

[0019] According to some embodiments of the present invention, the concentration of the copper precursor solution is 0.002 to 0.2 mol / L, preferably 0.02 to 0.2 mol / L.

[0020] In this invention, the copper loading in the Cu-supported Y molecular sieve catalyst can be controlled by adjusting the concentration of the copper precursor solution.

[0021] According to some embodiments of the present invention, the stirring time is 1 to 8 hours, for example, it can be 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, etc.

[0022] According to some embodiments of the present invention, the steps of adding copper precursor solution, stirring, and filtering are repeated 2 to 4 times.

[0023] In this invention, the alkalinity of the system can be continuously reduced through repeated processes, bringing the system closer to neutral, thereby promoting the full binding of copper ions with the active centers of the molecular sieve.

[0024] Secondly, the present invention provides a Cu-supported Y molecular sieve catalyst, which is prepared by the preparation method described in the first aspect.

[0025] According to some embodiments of the present invention, the copper loading in the catalyst is 0.1 wt% to 10 wt%, preferably 1 wt% to 10 wt%.

[0026] Thirdly, the present invention provides the application of the Cu-supported Y molecular sieve catalyst described in the second aspect in the preparation of dimethyl carbonate by the reaction of carbon dioxide and dimethyl ether.

[0027] Fourthly, the present invention provides a method for preparing dimethyl carbonate using carbon dioxide, comprising: reacting carbon dioxide and dimethyl ether in the presence of a copper catalyst to generate dimethyl carbonate;

[0028] The copper-containing catalyst comprises a Y molecular sieve and copper supported on the Y molecular sieve.

[0029] The method for preparing dimethyl carbonate provided by this invention uses gaseous dimethyl ether and gaseous carbon dioxide as reaction raw materials and copper-loaded Y molecular sieve as catalyst. The reaction conditions are mild and can be carried out at lower temperatures and pressures. Moreover, the reaction product contains only dimethyl carbonate, with no by-products generated and no water by-product produced. This effectively avoids the adverse effects of water on catalyst activity and dimethyl carbonate selectivity.

[0030] The copper-containing catalyst in this invention can be prepared by loading Cu onto Y molecular sieves using various common loading methods, such as impregnation.

[0031] According to some embodiments of the present invention, the copper-containing catalyst is the Cu-supported Y molecular sieve catalyst described in the second aspect.

[0032] According to some embodiments of the present invention, the copper loading in the copper-containing catalyst is 0.1 wt% to 10 wt%, preferably 1 wt% to 10 wt%.

[0033] In this invention, compared with copper-supported Y molecular sieve catalysts prepared by other common loading methods such as impregnation, the Cu-supported Y molecular sieve catalyst provided by this invention has a more significant synergistic effect between the metal atoms and the active centers of the molecular sieve, which can further improve the yield of dimethyl carbonate.

[0034] According to some embodiments of the present invention, the reaction is carried out in a fixed-bed reactor.

[0035] The method for preparing dimethyl carbonate using carbon dioxide provided in this invention can use a fixed-bed reactor, enabling continuous production, and the catalyst and reaction products can be easily separated.

[0036] According to some embodiments of the present invention, the reaction conditions include: a reaction temperature of 50–100°C, preferably 50–80°C; a reaction pressure of 0.1–1 MPa; and a mass hourly space velocity of 0.5–5 h⁻¹. -1 .

[0037] The method for preparing dimethyl carbonate using dimethyl ether and carbon dioxide provided by this invention can be carried out at a temperature of 50-100°C and a pressure of 0.1-1 MPa, without the need for supercritical CO2 as a raw material. The reaction conditions are significantly milder than existing methods for preparing dimethyl carbonate using dimethyl ether and carbon dioxide, making it more suitable for industrial production.

[0038] According to some embodiments of the present invention, the molar ratio of carbon dioxide to dimethyl ether is (10-20):1.

[0039] Compared with the prior art, the present invention can achieve at least the following beneficial effects:

[0040] (1) This invention uses copper-loaded Y molecular sieve to catalyze the reaction of dimethyl ether with carbon dioxide. The reaction conditions are mild, the reaction product contains only dimethyl carbonate, and no by-products are generated. The atom economy is 100%, which utilizes the greenhouse gas CO2, reduces environmental pollution, and provides a green chemical pathway for carbon dioxide utilization. Furthermore, since no by-product water is generated in the reaction, the adverse effects of water on the catalyst activity and dimethyl carbonate selectivity are effectively avoided, which can significantly improve the yield of dimethyl carbonate.

[0041] (2) The method for preparing dimethyl carbonate using carbon dioxide provided by the present invention is simple to operate and has mild process conditions. It can reduce industrial costs and improve industrial production efficiency in many ways and is suitable for industrial production.

[0042] (3) The Cu-supported Y molecular sieve catalyst prepared by the present invention has a more obvious synergistic effect between metal atoms and molecular sieve active centers. When used in the reaction of carbon dioxide and dimethyl ether to prepare dimethyl carbonate, it can further improve the yield of dimethyl carbonate. Moreover, the preparation method is simple, low in cost and conducive to industrial promotion. Detailed Implementation

[0043] To make the technical problem to be solved, the technical solution, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely for illustrating this patent and do not limit the scope of protection of this invention in any way.

[0044] Unless otherwise defined, the technical terms used in the following embodiments have the same meaning as commonly understood by those skilled in the art. Unless otherwise specified, the reagents used in the following embodiments are conventional biochemical reagents; the raw materials, instruments, and equipment used in the following embodiments can all be obtained commercially or by existing methods; unless otherwise specified, the reagent dosages are those used in routine experimental operations; unless otherwise specified, the experimental methods are conventional methods.

[0045] In the various embodiments and comparative examples of this invention, the copper loading was tested using ICP (Inductively Coupled Plasma Emission Spectrometry).

[0046] Example 1

[0047] (1) Catalyst preparation: Water glass, sodium aluminate, sodium hydroxide, and deionized water were mixed and stirred evenly, and then aged at room temperature for 4 hours to prepare a directing agent. Sodium silicate, aluminum sulfate, and sodium aluminate solutions were then added to this directing agent and mixed evenly to obtain a synthetic gel with a chemical composition of n(SiO2):n(Al2O3):n(Na2O):n(H2O)=1:10:5:150. This gel was transferred to a crystallization kettle for crystallization. After crystallization at 100℃ for 24 hours, the product was completely poured out. 0.1mol / L copper nitrate solution was added to the crystallized product, stirred for 2 hours, and then filtered. This process was repeated 3 times. The product was then dried in a 100℃ oven and calcined at 250℃ for 3 hours to obtain a Y molecular sieve catalyst with a copper loading of 5wt%, denoted as 5%Cu / Y.

[0048] (2) Preparation of dimethyl carbonate: 1 g of the above catalyst was loaded into a fixed-bed reactor. The catalyst was first activated with hydrogen gas, and then fed into the reactor. The feed composition was carbon dioxide to dimethyl ether in a molar ratio of 10:1. The reaction temperature was 52℃, the reaction pressure was 0.11 MPa, and the weight hourly space velocity (WHSV) was 2 h⁻¹. -1 The reaction evaluation results are listed in Table 1.

[0049] Example 2

[0050] (1) Catalyst preparation: Water glass, sodium aluminate, sodium hydroxide, and deionized water were mixed and stirred evenly, and then aged at room temperature for 4 hours to prepare a directing agent. Sodium silicate and aluminum sulfate solutions were then added to this directing agent and mixed evenly to obtain a synthetic gel with a chemical composition of n(SiO2):n(Al2O3):n(Na2O):n(H2O)=1:8:5:150. This gel was transferred to a crystallization kettle for crystallization. After crystallization at 100℃ for 24 hours, the product was completely poured out. 0.15mol / L copper nitrate solution was added to the crystallized product, stirred for 2 hours, and then filtered. This process was repeated 3 times. The product was then dried in a 100℃ oven and calcined at 200℃ for 4 hours to obtain a Y molecular sieve catalyst with a copper loading of 7.5wt%, denoted as 7.5%Cu / Y.

[0051] (2) Preparation of dimethyl carbonate: 1 g of the above catalyst was loaded into a fixed-bed reactor. The catalyst was first activated with hydrogen gas, and then fed into the reactor. The feed composition was carbon dioxide to dimethyl ether in a molar ratio of 20:1. The reaction temperature was 60℃, the reaction pressure was 0.2 MPa, and the weight hourly space velocity (WHSV) was 1 h⁻¹. -1 The reaction evaluation results are listed in Table 1.

[0052] Example 3

[0053] (1) Catalyst preparation: Water glass, sodium aluminate, sodium hydroxide, and deionized water were mixed and stirred evenly, and then aged at room temperature for 4 hours to prepare a directing agent. Sodium silicate, aluminum sulfate, and sodium aluminate solutions were then added to this directing agent and mixed evenly to obtain a synthetic gel with a chemical composition of n(SiO2):n(Al2O3):n(Na2O):n(H2O)=1:10:5:150. This gel was transferred to a crystallization vessel for crystallization at 100℃ for 24 hours, and the product was completely poured off. The crystallized product was filtered and washed three times with deionized water, dried in a 100℃ oven, and calcined at 250℃ for 3 hours to obtain NaY molecular sieve. The NaY molecular sieve was placed in a 0.1mol / L copper nitrate solution, stirred at room temperature for 3 hours, filtered, washed, dried in a 100℃ oven, and calcined at 250℃ for 3 hours to obtain a Y molecular sieve catalyst with a copper loading of 5wt%, denoted as 5%Cu / Y-JZ.

[0054] (2) The method for preparing dimethyl carbonate is the same as in Example 1. The reaction evaluation results are listed in Table 1.

[0055] Example 4

[0056] (1) Preparation of catalyst: Water glass, sodium aluminate, sodium hydroxide and deionized water were mixed and stirred evenly, and then aged at room temperature for 4 hours to prepare a directing agent; then sodium aluminate was dissolved in water, and a certain amount of copper nitrate solid was added. After stirring for half an hour, sodium hydroxide solid was added. After stirring for half an hour, the above directing agent was added. Finally, sodium silicate and aluminum sulfate were added to the above system to obtain a synthetic gel with a chemical composition of n(SiO2):n(Al2O3):n(Na2O):n(H2O)=1:10:5:150. The gel was crystallized at 100℃ for 48 hours. The crystallized product was filtered and washed three times with deionized water and then dried in an oven at 100℃ to obtain a Y catalyst with a copper loading of 5wt% prepared by the "one-pot method", denoted as 5%Cu / Y-YG.

[0057] (2) The method for preparing dimethyl carbonate is the same as in Example 1. The reaction evaluation results are listed in Table 1.

[0058] Comparative Example 1

[0059] (1) Catalyst preparation: Water glass, sodium aluminate, sodium hydroxide, and deionized water were mixed and stirred evenly, and then aged at room temperature for 4 hours to prepare a directing agent. Sodium silicate, aluminum sulfate, and sodium aluminate solutions were then added to this directing agent and mixed evenly to obtain a synthetic gel with a chemical composition of n(SiO2):n(Al2O3):n(Na2O):n(H2O)=1:10:5:150. This gel was transferred to a crystallization reactor for crystallization at 100℃ for 24 hours, and the product was completely poured out. The crystallized product was filtered and washed three times with deionized water, dried in a 100℃ oven, and calcined at 250℃ for 3 hours to obtain the Y molecular sieve catalyst, denoted as NaY.

[0060] (2) The method for preparing dimethyl carbonate is the same as in Example 1. The reaction evaluation results are listed in Table 1.

[0061] Comparative Example 2

[0062] (1) The method for preparing the catalyst is the same as in Example 1, except that the 0.1 mol / L copper nitrate solution is replaced with a 0.1 mol / L zinc nitrate solution. A Y molecular sieve catalyst with a zinc loading of 5% is obtained, denoted as 5wt%Zn / Y.

[0063] (2) The method for preparing dimethyl carbonate is the same as in Example 1. The reaction evaluation results are listed in Table 1.

[0064] Comparative Example 3

[0065] (1) Preparation of catalyst:

[0066] An appropriate amount of Al2O3 powder (800-1000 mesh) was mixed with 0.1 mol / L copper nitrate solution, stirred for 2 h, filtered, and repeated 3 times. The mixture was then dried in an oven at 100 °C and calcined at 250 °C for 3 h to obtain an alumina catalyst with a copper loading of 5 wt%, denoted as 5% Cu / Al2O3.

[0067] (2) The method for preparing dimethyl carbonate is the same as in Example 1. The reaction evaluation results are listed in Table 1.

[0068] Comparative Example 4

[0069] (1) Preparation of catalyst:

[0070] An appropriate amount of ZSM-5 molecular sieve (SiO2 / Al2O3=160) was mixed with 0.1mol / L copper nitrate solution, stirred for 2h, filtered, and repeated 3 times. The mixture was then dried in an oven at 100℃ and calcined at 250℃ for 3h to obtain a ZSM-5 molecular sieve catalyst with a copper loading of 5wt%, denoted as 5%Cu / ZSM-5 molecular sieve.

[0071] (2) The method for preparing dimethyl carbonate is the same as in Example 1. The reaction evaluation results are listed in Table 1.

[0072] Table 1

[0073]

[0074]

[0075] Wherein: Dimethyl ether conversion rate (%) = (mass of dimethyl ether in raw material per unit time - mass of dimethyl ether in product per unit time) / mass of dimethyl ether in raw material per unit time × 100%;

[0076] Dimethyl carbonate selectivity (%) = mass of dimethyl carbonate in product per unit time / (mass of dimethyl ether in feed per unit time - mass of dimethyl ether in product per unit time) × 100%.

[0077] The results in Table 1 show that under the conditions of using the NaY catalyst, carbon dioxide is difficult to activate, resulting in almost no reaction between carbon dioxide and dimethyl ether. However, using the copper-supported Y-type catalyst can promote the activation of carbon dioxide, allowing dimethyl ether and carbon dioxide to react under mild conditions to form dimethyl carbonate.

[0078] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A method for preparing a Cu-loaded Y molecular sieve catalyst, characterized in that, The preparation method includes: obtaining a mixture comprising a first silicon source, a first aluminum source, an alkali source and water, aging it to obtain a directing agent; then mixing the directing agent, a second silicon source, a second aluminum source and water to obtain a synthetic gel; crystallizing the synthetic gel, adding a copper precursor solution, stirring, filtering, drying and calcining to obtain the catalyst.

2. The production method according to claim 1, characterized by, The first silicon source includes water glass and / or sodium silicate; And / or, the first aluminum source includes sodium aluminate; And / or, the alkali source includes at least one of sodium hydroxide and potassium hydroxide. And / or, the second silicon source comprises water glass and / or sodium silicate; And / or, the second aluminum source includes at least one of sodium aluminate, aluminum sulfate, and aluminum nitrate; and / or the molar composition of the components contained in the synthetic gel is SiO2:Al2O3:OH - : H2O = 1 : (5-12) : (3-8) : (100-200).

3. The production method according to claim 1 or 2, characterized by, The aging conditions include: an aging temperature of 15–40°C and an aging time of 3–24 hours; And / or, the conditions for the crystallization treatment include: a crystallization temperature of 90–100°C and a crystallization time of 20–48 h; And / or, the calcination conditions include: a calcination temperature of 200–300°C and a calcination time of 1–4 hours.

4. The production method according to any one of claims 1 to 3, characterized by, The concentration of the copper precursor solution is 0.002–0.2 mol / L, preferably 0.02–0.2 mol / L; And / or, the stirring time is 1 to 8 hours; And / or, the steps of adding copper precursor solution, stirring, and filtering are repeated 2 to 4 times.

5. A Cu-supported Y molecular sieve catalyst, prepared by the preparation method according to any one of claims 1-4; Preferably, the copper loading in the catalyst is 0.1 wt% to 10 wt%, more preferably 1 wt% to 10 wt%.

6. The application of the Cu-supported Y molecular sieve catalyst according to claim 5 in the preparation of dimethyl carbonate by the reaction of carbon dioxide and dimethyl ether.

7. A method for producing dimethyl carbonate using carbon dioxide, characterized by, This includes: the reaction of carbon dioxide and dimethyl ether to produce dimethyl carbonate in the presence of a copper catalyst; The copper-containing catalyst comprises a Y molecular sieve and copper supported on the Y molecular sieve; Preferably, the copper-containing catalyst is the Cu-supported Y molecular sieve catalyst as described in claim 5.

8. The method of claim 7, wherein, The copper loading in the copper-containing catalyst is 0.1 wt% to 10 wt%, preferably 1 wt% to 10 wt%.

9. The method according to claim 7 or 8, characterized in that, The reaction is carried out in a fixed-bed reactor.

10. The method according to any one of claims 7-9, characterized in that, The reaction conditions include: reaction temperature 50-100°C, preferably 50-80°C; reaction pressure 0.1-1 MPa; mass space velocity 0.5-5 h -1 ; And / or, the molar ratio of carbon dioxide to dimethyl ether is (10-20):1.

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