CuGa-S-1 catalyst for catalyzing hydrogenation of carbon dioxide to prepare dimethyl ether as well as preparation method and application of CuGa-S-1 catalyst

Abstract

The invention discloses a CuGa-S-1 catalyst for catalyzing hydrogenation of carbon dioxide to prepare dimethyl ether, an S-1 molecular sieve is used as a carrier, Cu and Ga are used as active components and are uniformly dispersed on the S-1 molecular sieve, the molar ratio of Ga to Cu is 1.0-3.0, the mass fraction of Cu is 2-10%, and the mass fraction of Ga is 2-20%. The invention also discloses a preparation method and application of the CuGa-S-1 catalyst for catalyzing hydrogenation of carbon dioxide to prepare dimethyl ether. The preparation method disclosed by the invention is simple and easy to operate, large-scale industrial production is easy to carry out, and high dimethyl ether selectivity is shown in a reaction for preparing dimethyl ether through carbon dioxide hydrogenation.

Description

Technical Field

[0001] This invention belongs to the field of dimethyl ether preparation technology, specifically relating to a CuGa-S-1 catalyst for the catalytic hydrogenation of carbon dioxide to dimethyl ether, its preparation method, and its application. Background Technology

[0002] The process of converting carbon dioxide into dimethyl ether (DME) through the reaction of H2 and CO2 generated from renewable energy sources is of great significance for achieving carbon recycling and reducing greenhouse gas emissions. In the research field of DME production via carbon dioxide hydrogenation, current research mainly focuses on bifunctional catalysts combining methanol synthesis catalysts (copper-based catalysts, such as Cu-Zn catalysts) and methanol dehydration catalysts (solid acid catalysts, such as HZSM-5 zeolite). Examples of such technologies are described in Chinese invention patent applications CN104437603A and CN118162194A.

[0003] However, current composite bifunctional catalysts used in the hydrogenation of carbon dioxide to produce dimethyl ether have significant drawbacks: their preparation often involves the physical mixing of two independent components, resulting in a large distance between the bifunctional sites. This structural defect hinders the effective diffusion of the methanol intermediate, leading to the formation of numerous byproducts such as CO, methanol, and hydrocarbons. The emergence of these byproducts not only reduces the selectivity of the target product, dimethyl ether, but also increases the production cost of subsequent separation and purification stages. Therefore, achieving directional coupling of bifunctional sites through chemical bonding, optimizing mass transfer pathways and the synergistic effect between bifunctional sites, and overcoming the inherent limitations of physical mixing may be an effective means to improve the selectivity of dimethyl ether.

[0004] The technical solution disclosed in Chinese invention patent application CN119034737A is to uniformly disperse copper in acidic Si using an evaporation-induced self-assembly method. x Al 1-x On a support, a bifunctional catalyst with synergistic effects is constructed. This design not only optimizes the activity of methanol production via carbon dioxide hydrogenation but also promotes the in-situ condensation of methanol to dimethyl ether through acidic sites, thereby improving the selectivity and yield of dimethyl ether. However, the evaporation-induced self-assembly method is lengthy and cumbersome. The technical solution disclosed in Chinese invention patent application CN115990472A is the preparation of ZnAl via co-precipitation. a M b O e (M is at least one of Zr, Cr, Ce, Mn, Ga) The catalyst is used for the hydrogenation of carbon dioxide to methanol and the production of dimethyl ether, but the dimethyl ether selectivity of this catalyst is low.

[0005] Therefore, it is of great significance to develop a composite bifunctional catalyst that can efficiently catalyze the hydrogenation of carbon dioxide to dimethyl ether through chemical bonding, and whose preparation method is simple and easy to industrialize. Summary of the Invention

[0006] In view of the shortcomings of the prior art described above, the first objective of this invention is to provide a CuGa-S-1 catalyst for the catalytic hydrogenation of carbon dioxide to prepare dimethyl ether. By chemically bonding Cu and Ga elements are uniformly dispersed on S-1 molecular sieves, the interaction between Cu and Ga species is regulated, the synergistic effect between bifunctional sites is enhanced, and the technical problem of low selectivity of dimethyl ether products in existing composite bifunctional catalysts is solved.

[0007] A second objective of this invention is to provide a method for preparing the CuGa-S-1 catalyst for the catalytic hydrogenation of carbon dioxide to dimethyl ether.

[0008] A third objective of this invention is to provide the application of the CuGa-S-1 catalyst for the catalytic hydrogenation of carbon dioxide to dimethyl ether.

[0009] To achieve the above-mentioned objectives, the present invention is implemented through the following technical solution: a CuGa-S-1 catalyst for the catalytic hydrogenation of carbon dioxide to prepare dimethyl ether, wherein S-1 molecular sieve is used as a support, and Cu and Ga are the active components uniformly dispersed in the S-1 molecular sieve, wherein the molar ratio of Ga / Cu is 1.0 to 3.0, the mass fraction of Cu is 2 to 10%, and the mass fraction of Ga is 2 to 20%.

[0010] This invention provides a method for preparing a CuGa-S-1 catalyst for the catalytic hydrogenation of carbon dioxide to dimethyl ether, comprising the following steps: (1) Dissolve Cu salt and Ga salt in water to prepare a solution, stir thoroughly, add S-1 molecular sieve, stir thoroughly again, age, and dry; (2) Add amino acids to the product of (1), mix thoroughly and perform physical grinding, and then calcine and reduce to obtain CuGa-S-1 catalyst.

[0011] In step (1), the Cu salt is at least one of copper acetate, copper nitrate, and copper sulfate; the Ga salt is at least one of gallium acetate, gallium nitrate, and gallium sulfate.

[0012] In step (1), the stirring speed is 100-800 r / min and the stirring time is 1-4 h; preferably, the stirring speed is 800 r / min and the stirring time is 2 h.

[0013] In step (1), the aging time is 6 to 24 hours, preferably 24 hours; the drying temperature is 80 to 140°C, and the drying time is 8 to 16 hours.

[0014] In step (1), the amino acid is one or a combination of two or more of proline, histidine, glycine, alanine, and tryptophan.

[0015] In step (2), the amino acid / (Cu+Ga) molar ratio is 1 to 3, preferably 2.

[0016] In step (2), the grinding time is 10-60 min; the calcination temperature is 400-600℃ and the calcination time is 2-10 h; the reduction conditions are 10-50 vol% H2 / Ar mixed gas, gas flow rate is 30-60 mL / min, reduction temperature is 300-400℃ and reduction time is 2-6 h.

[0017] This invention also provides the application of the above-mentioned CuGa-S-1 catalyst in the preparation of dimethyl ether by hydrogenation of carbon dioxide.

[0018] The CuGa-S-1 catalyst was used for the CO2 hydrogenation to prepare dimethyl ether under the following conditions: reaction pressure 2–5 MPa, reaction temperature 200–300 °C, and reaction space velocity 6000–24000 mL / (g). cat The feed gas volume ratio V(H2) / V(CO2) is 2-4. Preferably, the reaction pressure is 4 MPa, the reaction temperature is 220℃, and the reaction space velocity is 24000 mL / (g·h). cat ·h), the volume ratio of raw gas V(H2) / V(CO2) is 4.

[0019] The preparation method of this invention mainly uses impregnation and solid-phase grinding to uniformly disperse metal Cu and Ga on S-1 molecular sieves through chemical bonding by the coordination of amino acids. By adjusting the Ga / Cu ratio, the interaction between Cu species and Ga species is regulated, and the synergistic effect between bifunctional sites is enhanced, effectively solving the technical problem of low selectivity of dimethyl ether products in existing composite bifunctional catalysts.

[0020] Compared with the prior art, the present invention has the following advantages: 1. A CuGa-S-1 catalyst was prepared using an amino acid-assisted method. Cu and Ga species were uniformly dispersed on the S-1 molecular sieve through chemical bonding. By changing the Ga / Cu ratio, the interaction between Cu and Ga species was regulated, thereby enhancing the synergistic effect between the bifunctional sites. 2. Its application in the production of dimethyl ether via CO2 hydrogenation can significantly improve the selectivity of dimethyl ether; 3. The preparation process using impregnation and solid-phase grinding is simple and reliable, suitable for large-scale preparation, and easy to industrialize. Attached Figure Description

[0021] Figure 1 The XRD patterns of the samples obtained in Examples 1 to 4 of this invention;

[0022] Figure 2 The XRD patterns are of the samples prepared in Comparative Examples 1 to 3 of this invention.

[0023] Figure 3 SEM image of the sample obtained in Example 1 of the present invention;

[0024] Figure 4 The TEM image is of the sample prepared in Example 1 of the present invention. Detailed Implementation

[0025] To further understand the present invention, it is described below with reference to specific embodiments and accompanying drawings. These descriptions are merely illustrative of the features and advantages of the invention and are not intended to limit the scope of the claims. Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods. Unless otherwise specified, the materials and reagents used in the following embodiments are commercially available.

[0026] Synthesis of S-1 molecular sieve

[0027] The synthesis steps of S-1 molecular sieve are as follows: 83.332 g of tetraethyl orthosilicate, 113.89 g of tetrapropylammonium hydroxide (added as a 25 wt% aqueous solution), and 166.5825 g of deionized water were added to a container (beaker) and stirred at 600 r / min for 12 h to form a synthetic gel. The gel was transferred to a stainless steel reactor lined with polytetrafluoroethylene and crystallized in an oven at 170 °C for 72 h. The crystallized product was washed with water, centrifuged at 9000 r / min for 10 min, and dried in an oven at 120 °C for 12 h. Subsequently, the powder was calcined in a muffle furnace at 550 °C for 8 h to obtain S-1 molecular sieve.

[0028] Example 1

[0029] A method for preparing a CuGa-S-1 catalyst for the catalytic hydrogenation of carbon dioxide to dimethyl ether, comprising the following steps: (1) Add 3.1702g of copper acetate and 4.463g of gallium nitrate to 200g of deionized water and mix. Stir at 200r / min for 1h to obtain a mixed solution of copper salt and gallium salt. Add 20g of S-1 molecular sieve and stir at 800r / min for 4h. After stirring, place it in a dark environment and age for 12h. Then dry it in an oven at 140℃ for 12h. (2) Add 12.7787 g of histidine to the product of step (1) and perform physical grinding for 60 min; then place the powder in a muffle furnace and calcine at 550 °C for 4 h to obtain CuGa-S-1 catalyst, wherein the Ga / Cu molar ratio is 1.0, the Cu mass fraction is 5.0%, and the Ga mass fraction is 5.5%.

[0030] The SEM image of the CuGa-S-1 catalyst is shown below. Figure 3 As shown.

[0031] Example 2

[0032] A method for preparing a CuGa-S-1 catalyst for the catalytic hydrogenation of carbon dioxide to dimethyl ether, comprising the following steps: (1) Add 1.6287g of copper sulfate and 1.6139g of gallium acetate to 200g of deionized water and mix. Stir at 500r / min for 3h to obtain a mixed solution of copper salt and gallium salt. Add 20g of S-1 molecular sieve and stir at 300r / min for 4h. After stirring, place it in a dark environment and age for 10h. Then dry it in an oven at 140℃ for 12h. (2) Add 3.487g of alanine to the product of step (1) and perform physical grinding for 30min; then place the powder in a muffle furnace and calcine at 450℃ for 10h to obtain CuGa-S-1 catalyst, wherein the Ga / Cu molar ratio is 1.0, the mass fraction of Cu is 2.0%, and the mass fraction of Ga is 2.2%.

[0033] Example 3

[0034] A method for preparing a CuGa-S-1 catalyst for the catalytic hydrogenation of carbon dioxide to dimethyl ether, comprising the following steps: (1) Add 3.7248g of copper nitrate and 25.4782g of gallium sulfate to 200g of deionized water and mix. Stir at 600r / min for 2h to obtain a mixed solution of copper salt and gallium salt. Add 20g of S-1 molecular sieve and stir at 200r / min for 1h. After stirring, place it in a dark environment and age for 18h. Then dry it in an oven at 120℃ for 12h. (2) 18.2918 g of proline was added to the product of step (1) and physically ground for 60 min. Then the powder was placed in a muffle furnace and calcined at 600 °C for 8 h to obtain CuGa-S-1 catalyst, wherein the molar ratio of Ga / Cu was 3.0, the mass fraction of Cu was 5.0%, and the mass fraction of Ga was 16.3%.

[0035] Example 4

[0036] A method for preparing a CuGa-S-1 catalyst for the catalytic hydrogenation of carbon dioxide to dimethyl ether, comprising the following steps: (1) Add 9.8621g of copper sulfate and 16.7381g of gallium nitrate to 200g of deionized water and mix. Stir at 800r / min for 4h to obtain a mixed solution of copper salt and gallium salt. Add 20g of S-1 molecular sieve and stir at 800r / min for 2h. After stirring, place it in a dark environment and age for 24h. Then dry it in an oven at 140℃ for 12h. (2) 11.8066 g glycine was added to the product of step (1) and physically ground for 60 min; then the powder was placed in a muffle furnace and calcined at 500 °C for 4 h to obtain CuGa-S-1 catalyst; wherein the molar ratio of Ga / Cu was 1.7, the mass fraction of Cu was 9.3%, and the mass fraction of Ga was 16.8%.

[0037] Comparative Example 1

[0038] A method for preparing a Cu-S-1 catalyst for the catalytic hydrogenation of carbon dioxide to dimethyl ether, comprising the following steps: (1) Add 4.217g of copper nitrate to 200g of deionized water and stir thoroughly at 500r / min for 3h to obtain copper salt solution. Add 20g of S-1 molecular sieve and continue stirring at 300r / min for 3h. After stirring, place it in a dark environment and age for 6h. Then dry it in an oven at 140℃ for 12h. (2) Add 14.89 g of histidine to the product of step (1) and perform physical grinding for 60 min; then place the powder in a muffle furnace and calcine at 400 °C for 6 h to finally obtain Cu-S-1 catalyst, wherein the mass fraction of Cu is 5.3%.

[0039] Comparative Example 2

[0040] A method for preparing a CuGa-SiO2 catalyst for the catalytic hydrogenation of carbon dioxide to dimethyl ether, comprising the following steps: (1) Add 3.1703g of copper acetate and 7.4627g of gallium sulfate to 200g of deionized water and mix. Stir thoroughly at 500r / min for 3h. Add 20g of SiO2 and continue stirring for 3h. After stirring, place it in a dark environment and age for 24h. Then dry it in an oven at 140℃ for 12h. (2) Add 9.4823 g of histidine to the product of step (1) and perform physical grinding for 60 min; then place the powder in a muffle furnace and calcine at 500 °C for 6 h to finally obtain CuGa-SiO2 catalyst, wherein the Ga / Cu molar ratio is 1.0, the mass fraction of Cu is 5.0%, and the mass fraction of Ga is 5.5%.

[0041] Comparative Example 3

[0042] A method for preparing a CuGa-Na-ZSM-5 catalyst for the catalytic hydrogenation of carbon dioxide to dimethyl ether, comprising the following steps: (1) Add 3.7237g copper nitrate and 4.3079g gallium acetate to 200g deionized water and mix. Stir thoroughly at 500r / min for 3h. Add 20g Na-ZSM-5 and continue stirring for 3h. After stirring, place it in a dark environment and age for 24h. Then dry it in an oven at 140℃ for 12h. (2) 7.1287 g of tryptophan was added to the product of step (1) and physically ground for 60 min; then the powder was placed in a muffle furnace and calcined at 500 °C for 6 h to finally obtain CuGa-Na-ZSM-5 catalyst, wherein the molar ratio of Ga / Cu was 1.0, the mass fraction of Cu was 5.0%, and the mass fraction of Ga was 5.5%.

[0043] Compare the XRD patterns of the catalyst samples prepared in Examples 1-4 and Comparative Examples 1-3, as follows: Figure 1 and Figure 2 As shown, except for the CuGa-S-1 catalyst (Cu loading close to 10%) prepared in Example 4 and the CuGa-SiO2 catalyst prepared in Comparative Example 2, the other catalyst samples did not show obvious CuO characteristic peaks. This indicates that Cu and Ga are uniformly dispersed on the S-1 molecular sieve support and Na-ZSM-5. SEM and TEM images of the catalyst sample prepared in Example 1 are shown below. Figure 3 and Figure 4 As shown, the S-1 molecular sieve support has a uniform size of about 300 nm, and Cu and Ga are uniformly dispersed on the S-1 molecular sieve support.

[0044] Catalyst evaluation

[0045] The catalyst samples were ground, compressed, crushed, and sieved to obtain catalyst particles of 40–60 mesh. The corresponding catalyst particle samples were then loaded into a fixed-bed reactor and activated by introducing reducing gas. After activation, the temperature was lowered to the reaction temperature, the reducing gas was switched to a reaction mixture, and then the pressure was increased to the reaction pressure for the reaction. The reducing gas was a 10–50 vol% H₂ / Ar mixture with a flow rate of 30–60 mL / min, a reduction temperature of 300–400 °C, and a reduction time of 2–6 h. The reaction mixture was an H / CO mixture with a V(H₂) / V(CO₂) ratio of 2–4 and a space velocity of 6000–24000 mL / (g⁻¹). cat ·h), the reaction pressure is 2 to 5 MPa.

[0046] Table 1 Reaction conditions and results

[0047] As shown in Table 1, the CuGa-S-1 catalysts prepared in Examples 1-4 effectively improve the selectivity for the hydrogenation of carbon dioxide to dimethyl ether. The results of Comparative Example 1 indicate that Ga species play a crucial role in the hydrogenation of carbon dioxide to dimethyl ether; the selectivity for dimethyl ether is 0 in the absence of Ga species. Furthermore, when the support is changed from S-1 molecular sieve to SiO2 or Na-ZSM-5, almost no dimethyl ether is formed in the carbon dioxide hydrogenation reaction. These results demonstrate that the CuGa-S-1 catalyst utilizes the coordination effect of amino acids to chemically bond metallic Cu and Ga species onto the S-1 molecular sieve through simple impregnation and mechanical grinding. By leveraging the synergistic effect between the two, it can effectively catalyze the hydrogenation of carbon dioxide to dimethyl ether.

[0048] It should be noted that those skilled in the art can make several simple modifications, substitutions, or changes to the above embodiments without departing from the concept of the present invention, or adjust some technical features through equivalent transformations. Any modifications, changes, and improvements made based on the technical essence of the present invention shall still fall within the protection scope of the present invention. The protection scope of the present invention shall be determined by the claims and shall cover all technical solutions that conform to the innovative essence of the present invention and their equivalent alternatives.

Claims

1. A CuGa-S-1 catalyst for the catalytic hydrogenation of carbon dioxide to dimethyl ether, characterized in that, Using S-1 molecular sieve as a carrier, Cu and Ga are active components dispersed within the S-1 molecular sieve, wherein the Ga / Cu molar ratio is 1.0 to 3.

0.

2. The CuGa-S-1 catalyst for the catalytic hydrogenation of carbon dioxide to dimethyl ether according to claim 1, characterized in that, The mass fraction of Cu is 2–10%, and the mass fraction of Ga is 2–20%.

3. The method for preparing a CuGa-S-1 catalyst for the catalytic hydrogenation of carbon dioxide to dimethyl ether according to claim 1 or 2, characterized in that, Includes the following steps: (1) Dissolve Cu salt and Ga salt in water to prepare a solution, stir, add S-1 molecular sieve, stir again, age, and dry; (2) Add amino acids to the product of (1) and mix, then perform physical grinding, followed by calcination and reduction.

4. The method for preparing a CuGa-S-1 catalyst for the catalytic hydrogenation of carbon dioxide to dimethyl ether according to claim 3, characterized in that, The Cu salt is at least one of copper acetate, copper nitrate, and copper sulfate; the Ga salt is at least one of gallium acetate, gallium nitrate, and gallium sulfate.

5. The method for preparing a CuGa-S-1 catalyst for the catalytic hydrogenation of carbon dioxide to dimethyl ether according to claim 3, characterized in that, The amino acid is one or a combination of two or more of proline, histidine, glycine, alanine, and tryptophan; the amino acid / (Cu+Ga) molar ratio is 1 to 3.

6. The method for preparing a CuGa-S-1 catalyst for the catalytic hydrogenation of carbon dioxide to dimethyl ether according to claim 3, characterized in that, In step (1), the stirring speed is 100-800 r / min, the stirring time is 1-4 h, the aging time is 6-24 h, the drying temperature is 80-140 ℃, and the drying time is 8-16 h.

7. The method for preparing a CuGa-S-1 catalyst for the catalytic hydrogenation of carbon dioxide to dimethyl ether according to claim 3, characterized in that, In step (2), the grinding time is 10-60 min; the calcination temperature is 400-600℃ and the calcination time is 2-10 h; the reduction conditions are 10-50 vol% H2 / Ar mixed gas, the gas flow rate is 30-60 mL / min, the reduction temperature is 300-400℃ and the reduction time is 2-6 h.

8. The CuGa-S-1 catalyst for the catalytic hydrogenation of carbon dioxide to dimethyl ether according to claim 2, characterized in that, Application in the preparation of dimethyl ether by hydrogenation of carbon dioxide.

9. The application of the CuGa-S-1 catalyst for the hydrogenation of carbon dioxide to dimethyl ether according to claim 8 in the hydrogenation of carbon dioxide to dimethyl ether, characterized in that, The reaction conditions are: reaction pressure 2–5 MPa, reaction temperature 200–300 °C, and reaction space velocity 6000–24000 mL / (g). cat The volume ratio of raw gas (H2) / CO2 is 2-4.

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