Method for synthesizing acrylic acid from CO2 and ethylene

Abstract

The invention relates to a method for synthesizing acrylic acid from CO2 and ethylene, which comprises the following steps: firstly, adding a catalyst and a solvent into a reactor, then introducing carbon dioxide and ethylene for reaction, and finally synthesizing acrylic acid, wherein 1.1. 3. 3-tetramethyl-2-alkyl guanidine salt of which the anion is I <-> is adopted as the catalyst, and tetrahydrofuran and acetonitrile are adopted as the solvent. According to the method, CO2 and ethylene are used as raw materials, acrylic acid is synthesized in the presence of the specific catalyst and solvent, and the method has the advantages of high product selectivity and yield, mild preparation conditions and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of acrylic acid synthesis, and particularly relates to a method for synthesizing acrylic acid from CO2 and ethylene. Background Art

[0002] With the increasing dependence on petrochemical resources in modern society, the continuously increasing CO2 emission problem has become not only an environmental issue, but also risen to the level of international relations and is related to the survival and development of mankind. The greenhouse effect caused by the sharp increase in CO2 will seriously threaten the survival of mankind. The global energy shortage and the increasingly serious environmental problems caused by CO2 force people to find ways to solve these problems, and thus are committed to the treatment and utilization of CO2. The most direct method for CO2 treatment is how to consume more CO2 and achieve the recycling of CO2 to fundamentally solve the CO2 problem. The chemical utilization of CO2 is one of the important means to achieve the recycling of CO2. Especially in large-scale chemical production, the extensive use of CO2 plays a crucial role in its emission reduction.

[0003] Acrylic acid (ester) is an important organic synthesis intermediate and monomer for synthesizing polymers, and it has a wide range of uses in industries such as coatings, medicine, leather, papermaking, adhesives, etc. The main production methods of acrylic acid (ester) are: acrylonitrile hydrolysis method, propylene oxidation method, ketene method, among which the propylene oxidation method accounts for a relatively large proportion of its total production capacity. The method of synthesizing acrylic acid or acrylic ester from ethylene and CO2 obviously has more economic advantages and the advantages of green chemistry. At present, this route is atom-economic and the reaction conditions are very mild. At the same time, this method also provides an economical and effective way for the efficient utilization of the greenhouse gas CO2 resources.

[0004] CN101745428A discloses a catalyst for catalytic conversion of carbon dioxide into methacrylic acid and its application. An oxidation cerium-supported polyoxometalate catalyst is used, and carbon dioxide and propylene are used as raw materials to catalytically synthesize methacrylic acid directly. The oxidation cerium-supported polyoxometalate catalyst is composed of polyoxometalate and oxidation cerium. The catalyst used has high activity, high selectivity for the target product and stable catalytic performance. However, the application temperature of this catalyst is too high, increasing the synthesis energy consumption.

[0005] CN105622383A discloses a method for synthesizing acrylic acid. Using CO2 and ethylene as raw materials, tetrahydrofuran and ionic liquid as solvents, and metal Ni complex as a catalyst to directly synthesize acrylic acid. The product selectivity of this method needs to be improved, and the metal Ni complex catalyst used needs to be prepared under anhydrous and anaerobic conditions, and the solvent tetrahydrofuran also needs to be dehydrated and deoxygenated, and the preparation conditions are relatively harsh. Summary of the Invention

[0006] In view of the deficiencies of the prior art, the present invention provides a method for synthesizing acrylic acid from CO2 and ethylene. The present invention uses CO2 and ethylene as raw materials and synthesizes acrylic acid in the presence of a specific catalyst and solvent, with advantages such as high product selectivity and yield, and mild preparation conditions.

[0007] The method for synthesizing acrylic acid from CO2 and ethylene provided by the present invention includes the following steps: First, add a catalyst and a solvent into a reactor, then introduce carbon dioxide and ethylene to react, and finally synthesize acrylic acid; wherein the catalyst uses 1,1,3,3-tetramethyl-2-alkylguanidine salt with an anion of I - , and the solvent uses tetrahydrofuran and acetonitrile.

[0008] In the catalyst of the present invention, the alkyl in the alkylguanidine salt is one or two of cyclopentyl, cyclohexyl, etc.

[0009] The anion used in the present invention is 1,1,3,3-tetramethyl-2-alkylguanidine salt with an anion of I - , and the preferred preparation method is as follows:

[0010] (1) Dissolve tetramethylurea in solvent A, add phosphorus oxychloride under nitrogen protection to react, then add alkylamine to react, and then add water to continue the reaction. After the reaction, let it stand for layering. Take the lower layer liquid and add NaOH. After layering, take the upper layer liquid, dry it and then distill it to obtain a distillate;

[0011] (2) Dissolve the distillate in solvent B, add a mixed solution of iodomethane and solvent C under an ice-water bath and nitrogen protection. After the system reaches room temperature, continue the reaction. After the reaction, distill it under normal pressure. After washing the residual liquid, obtain 1,1,3,3-tetramethyl-2-alkylguanidine salt with an anion of I - .

[0012] In the above catalyst preparation method, in step (1), solvent A is at least one of acetonitrile, benzene, toluene, tetrahydrofuran, etc., and toluene is preferred. The volume ratio of solvent A to tetramethylurea is 5-20:1, and preferably 8-16:1.

[0013] In the above catalyst preparation method, in step (1), the molar ratio of tetramethylurea to phosphorus oxychloride is 0.5:1-1:5, and preferably 0.5:1-1:3. The reaction time for adding phosphorus oxychloride is 2-15 h, and preferably 4-14 h.

[0014] In the above catalyst preparation method, in step (1), the alkyl in the alkylamine is a cycloalkyl group, and at least one of cyclopentylamine, cyclohexylamine, etc. is preferred. The molar ratio of alkylamine to tetramethylurea is 1:0.5-1:3, and preferably 1:0.7-1:2. After adding the alkylamine, the reaction time is 20-80 h, and preferably 25-60 h.

[0015] In the above catalyst preparation method, in step (1), the volume ratio of water to solvent A is 2.5:1 to 0.7:1, preferably 2:1 to 1:1; after addition, the reaction is carried out for 2 to 15 h, preferably 4 to 12 h.

[0016] In the above catalyst preparation method, in step (1), the standing and layering time is 5 to 60 min, preferably 10 to 40 min.

[0017] In the above catalyst preparation method, in step (1), the molar ratio of NaOH to phosphorus oxychloride is 10:1 to 3:1, preferably the molar ratio is 8:1 to 4:1.

[0018] In the above catalyst preparation method, after layering in step (1), the upper layer liquid is under the condition of 30 - 32 mmHg, and the distillate at 128 - 132 °C is taken.

[0019] In the above catalyst preparation method, in step (2), solvent B is at least one of acetonitrile, benzene, toluene, tetrahydrofuran, etc., preferably acetonitrile. The volume ratio of solvent B to the distillate is 30:1 to 10:1, preferably 20:1 to 15:1.

[0020] In the above catalyst preparation method, in step (2), solvent C is at least one of acetonitrile, benzene, toluene, tetrahydrofuran, etc., preferably benzene.

[0021] In the above catalyst preparation method, the volume ratio of methyl iodide to solvent C is 1:5 to 1:20, preferably 1:10 to 1:17. The volume ratio of solvent B to the mixture of methyl iodide and solvent C is 1 to 5:1, preferably 1.5 to 4:1. When adding the mixture of methyl iodide and solvent C, the flow rate is controlled at 0.5 to 10 mL / min, preferably 1 to 7 mL / min.

[0022] In the above catalyst preparation method, in step (2), after the system returns to room temperature, the reaction continues for 24 - 36 h. After the reaction, atmospheric distillation is carried out at 50 - 150 °C. The residual liquid is washed with ethyl acetate, washed 3 - 5 times, and ethyl acetate is removed by vacuum filtration after washing.

[0023] In the synthesis method of the present invention, the addition amount of the catalyst is 5% - 7.5% of the total mass of the reaction system. The solvent uses a solvent mixed with tetrahydrofuran and acetonitrile, wherein the volume ratio of acetonitrile to tetrahydrofuran is 1 - 9:1, preferably 5 - 9:1. The ratio of the solvent to the catalyst is 100 - 200 mL:2 - 4.5 g.

[0024] In the synthesis method of the present invention, the molar ratio of ethylene to carbon dioxide is 1:1 to 1:10, preferably 1:3 to 1:8. The temperature of the synthesis reaction is 50 - 120 °C, preferably 70 - 100 °C; the reaction pressure is 0.5 - 6.0 MPa, preferably 1.0 - 5.5 MPa.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] (1) Using 1,1,3,3-tetramethyl-2-alkylguanidine salt with anions of I - as a catalyst can significantly improve the selectivity of the product while ensuring the yield of acrylic acid synthesized from ethylene and CO2 as raw materials.

[0027] (2) In the presence of the catalyst of the present invention, a mixed solvent of acetonitrile and tetrahydrofuran is used simultaneously, further improving the selectivity of acrylic acid in the product.

[0028] (3) The preparation conditions of the catalyst used in the present invention are mild and the performance is stable. Detailed implementation manners

[0029] The technical solution and its effects of the present invention will be further described in detail below in conjunction with specific embodiments. The embodiments are implemented on the premise of the technical solution of the present invention, and detailed implementation manners and specific operation processes are given, but the protection scope of the present invention is not limited to the following embodiments.

[0030] In the following embodiments, the experimental methods, unless otherwise specified, are all conventional methods in the art. The experimental materials used in the following embodiments, unless otherwise specified, are all purchased from conventional biochemical reagent stores. In the present invention, the percentage content is the weight percentage content.

[0031] In the present invention, acrylic acid is analyzed by an Agilent GC-7820A gas chromatograph. The chromatographic column is a 30m×530μm×1μm capillary column. Programmed temperature rise is adopted, and it is kept at a constant temperature of 230°C for 10 minutes. The detector temperature is 250°C; the normalization method is used for quantitative analysis.

[0032] Example 1

[0033] Preparation of catalyst: (1) First, take tetramethylurea and dissolve it in toluene. The volume ratio of toluene to tetramethylurea is 9:1. Under nitrogen protection, add phosphorus oxychloride. The molar ratio of tetramethylurea to phosphorus oxychloride is 1:2. After reacting at room temperature for 8 h, add cyclohexylamine. The molar ratio of cyclohexylamine to tetramethylurea is 1:0.8. After reacting at room temperature for 25 h, add distilled water. The volume ratio of distilled water to toluene is 2:1. Continue to react for 8 h and then let it stand for liquid separation for 30 min. Take the lower layer liquid and add NaOH. The molar ratio of NaOH to phosphorus oxychloride is 5:1. After liquid separation, take the upper layer liquid, dry it and then distill it. Under the condition of 32 mmHg, collect the distillate at 128 - 132 °C; (2) Dissolve the distillate in acetonitrile. The volume ratio of the distillate to acetonitrile is 1:16. Under ice - water bath cooling and nitrogen protection, add a mixed solution of methyl iodide and benzene. The volume ratio of methyl iodide to benzene is 1:12. The volume ratio of acetonitrile to the mixed solution of methyl iodide and benzene is 2:1. Control the flow rate at 5 mL / min. After the system returns to room temperature, continue to stir and react for 24 h. After the reaction, distill it under normal pressure to evaporate the solvent. Wash the residual liquid three times with ethyl acetate. After washing, filter it under reduced pressure to remove ethyl acetate, and obtain 1,1,3,3 - tetramethyl - 2 - cyclohexylguanidine salt with an anion of I - .

[0034] Synthesis of acrylic acid: Add 3.6 g of the catalyst prepared above and 120 mL of solvent to the autoclave. The volume ratio of acetonitrile to tetrahydrofuran in the solvent is 8:1; then introduce the raw material gases carbon dioxide and ethylene. The molar ratio of carbon dioxide to ethylene is 1.7. The amount of the catalyst accounts for 5% of the total amount of the reaction system. The reaction temperature is 70 °C, the reaction pressure is 5.0 MPa. After reacting for 7 h, the yield of acrylic acid is 10.15% and the selectivity of acrylic acid is 92.3%.

[0035] Example 2

[0036] Preparation of catalyst: (1) First, take tetramethylurea and dissolve it in toluene. The volume ratio of toluene to tetramethylurea is 9:1. Under nitrogen protection, add phosphorus oxychloride. The molar ratio of tetramethylurea to phosphorus oxychloride is 1:2. After reacting at room temperature for 8 h, add cyclohexylamine. The molar ratio of cyclohexylamine to tetramethylurea is 1:0.8. After reacting at room temperature for 25 h, add distilled water. The volume ratio of distilled water to toluene is 2:1. Continue to react for 4 h and then let it stand for liquid separation for 40 min. Take the lower layer liquid and add NaOH. The molar ratio of NaOH to phosphorus oxychloride is 4:1. After liquid separation, take the upper layer liquid, dry it and then distill it. Under the condition of 32 mmHg, take the distillate at 128 - 132 °C; (2) Take the distillate and dissolve it in acetonitrile. The volume ratio of the distillate to acetonitrile is 1:20. Under ice - water bath cooling and nitrogen protection, add a mixed solution of methyl iodide and acetonitrile. The volume ratio of methyl iodide to acetonitrile in it is 1:5, and the volume ratio of acetonitrile to the mixed solution of methyl iodide and acetonitrile is 4:1. Control the flow rate at 7 mL / min. After the system returns to room temperature, continue to stir and react for 36 h. After the reaction, distill it under normal pressure and distill out the solvent at 100 °C. Wash the residual liquid three times with ethyl acetate. After washing, filter it under reduced pressure to remove ethyl acetate, and obtain 1,1,3,3 - tetramethyl - 2 - cyclohexylguanidine salt with an anion of I - -.

[0037] Synthesis of acrylic acid: Add 3.8 g of catalyst and 100 mL of solvent into an autoclave. The volume ratio of acetonitrile to tetrahydrofuran in the solvent is 5.6:1; then introduce the raw material gases carbon dioxide and ethylene. The molar ratio of carbon dioxide to ethylene is 1.8, and the amount of the catalyst accounts for 5.5% of the total amount of the reaction system. The reaction temperature is 90 °C, the reaction pressure is 2.5 MPa. After reacting for 8 h, the yield of acrylic acid is 9.28% and the selectivity of acrylic acid is 93.1%.

[0038] Example 3

[0039] Preparation of catalyst: (1) First, take tetramethylurea and dissolve it in toluene. The volume ratio of toluene to tetramethylurea is 16:1. Under nitrogen protection, add phosphorus oxychloride. The molar ratio of tetramethylurea to phosphorus oxychloride is 1:3. After reacting at room temperature for 4 h, add cyclopentylamine. The molar ratio of cyclopentylamine to tetramethylurea is 1:3. After reacting at room temperature for 25 h, add distilled water. The volume ratio of distilled water to toluene is 2:1. Continue to react for 12 h and then let it stand for liquid separation for 10 min. Take the lower layer liquid and add NaOH. The molar ratio of NaOH to phosphorus oxychloride is 8:1. After liquid separation, take the upper layer liquid, dry it and then distill it. Under the condition of 32 mmHg, take the distillate at 128 - 132 °C; (2) Take the distillate and dissolve it in acetonitrile. The volume ratio of the distillate to acetonitrile is 1:15. Under ice - water bath cooling and nitrogen protection, add a mixed solution of iodomethane and acetonitrile. The volume ratio of iodomethane to acetonitrile is 1:5, and the volume ratio of acetonitrile to the mixed solution of iodomethane and acetonitrile is 2:1. Control the flow rate at 1 mL / min. After the system returns to room temperature, continue to stir and react for 24 h. After the reaction, distill it at normal pressure and distill out the solvent at 50 °C. Wash the residual liquid three times with ethyl acetate. After washing, filter it under reduced pressure to remove ethyl acetate, and obtain a 1,1,3,3 - tetramethyl - 2 - cyclopentylguanidine salt catalyst with an anion of I - -.

[0040] Synthesis of acrylic acid: Add 3.5 g of catalyst and 110 mL of solvent to the autoclave. The volume ratio of acetonitrile to tetrahydrofuran in the solvent is 7.6:1; then introduce the raw material gases carbon dioxide and ethylene. The molar ratio of carbon dioxide to ethylene is 2.6, and the amount of the catalyst accounts for 5.5% of the total amount of the reaction system. The reaction temperature is 70 °C, the reaction pressure is 3.2 MPa. After reacting for 9 h, the yield of acrylic acid is 9.96%, and the selectivity of acrylic acid is 92.7%.

[0041] Example 4

[0042] Same as Example 1, except that: the volume ratio of acetonitrile to tetrahydrofuran in the mixed solvent is 4:1. After the reaction, through detection, the yield of acrylic acid is 9.89%, and the selectivity of acrylic acid is 87.4%.

[0043] Example 5

[0044] Same as Example 1, except that: the volume ratio of acetonitrile to tetrahydrofuran in the mixed solvent is 1:1. After the reaction, through detection, the yield of acrylic acid is 9.64%, and the selectivity of acrylic acid is 86.9%.

[0045] Example 6

[0046] Same as Example 1, except that: the catalyst used is a mixture of the catalysts prepared in Example 1 and Example 3, and the mass ratio of the two is 1:1. After the reaction is completed, through detection, the yield of acrylic acid is 10.57%, and the selectivity of acrylic acid is 94.1%.

[0047] Comparative Example 1

[0048] Same as Example 1, except that: only acetonitrile was used as the solvent. After the reaction was completed and detected, the yield of acrylic acid was 5.79%, and the selectivity of acrylic acid was 80.3%.

[0049] Comparative Example 2

[0050] Same as Example 1, except that: only tetrahydrofuran was used as the solvent. After the reaction was completed and detected, the yield of acrylic acid was 6.05%, and the selectivity of acrylic acid was 77.9%.

[0051] Comparative Example 3

[0052] Same as Example 1, except that: heptylamine was used as the alkylamine in the catalyst preparation to obtain the catalyst. After the reaction was completed and detected, the yield of acrylic acid was 2.03%, and the selectivity of acrylic acid was 60.8%.

[0053] Comparative Example 4

[0054] Same as Example 1, except that: butylamine was used as the alkylamine in the catalyst preparation. After the reaction was completed and detected, the yield of acrylic acid was 5.58%, and the selectivity of acrylic acid was 65.4%.

[0055] Comparative Example 5

[0056] Same as Example 1, except that: the catalyst and method described in Example 1 of CN105622383A were used to synthesize acrylic acid. The yield of acrylic acid was 1.08%, and the selectivity of acrylic acid was 72.1%.

Claims

1. A method for synthesizing acrylic acid from CO2 and ethylene, characterized in that It includes the following steps: First, add a catalyst and a solvent into a reactor, then introduce carbon dioxide and ethylene to carry out a reaction, and finally synthesize acrylic acid; wherein the catalyst uses a 1.1.3.3-tetramethyl-2-alkylguanidine salt with an anion of I - , and the solvent uses tetrahydrofuran and acetonitrile.

2. The method according to claim 1, characterized in that: The alkyl group in the alkyl guanidine salt in the catalyst is one or two of cyclopentyl and cyclohexyl.

3. The method according to claim 1, characterized in that: The anion is I - The preparation method of 1,1,3,3-tetramethyl-2-alkylguanidine salt with the anion of I is as follows: (1) Dissolve tetramethylurea in solvent A, add phosphorus oxychloride under nitrogen protection to react, then add alkylamine to react, and then add water to continue the reaction. After the reaction, let it stand for stratification. Take the lower layer liquid and add NaOH. After stratification, take the upper layer liquid, dry it and then distill it to obtain the distillate; (2) Dissolve the distillate in solvent B, add the mixed solution of iodomethane and solvent C under ice-water bath and nitrogen protection. After the system reaches room temperature, continue the reaction. After the reaction, distill it under normal pressure. After the residue is washed, 1,1,3,3-tetramethyl-2-alkylguanidine salt with the anion of I - is obtained.

4. The method according to claim 3, characterized in that: In step (1), the solvent A is at least one of acetonitrile, benzene, toluene or tetrahydrofuran, preferably toluene; the volume ratio of the solvent A to tetramethylurea is 5-20:1, preferably 8-16:

1.

5. The method according to claim 3, characterized in that: In step (1), the molar ratio of tetramethylurea to phosphorus oxychloride is 0.5:1-1:5, preferably 0.5:1-1:3; the reaction time for adding phosphorus oxychloride is 2-15 h, preferably 4-14 h.

6. The method according to claim 3, characterized in that: In step (1), the alkyl group in the alkylamine is a cycloalkyl group, preferably at least one of cyclopentylamine and cyclohexylamine; the molar ratio of the alkylamine to tetramethylurea is 1:0.5-1:3, preferably 1:0.7-1:2; after adding the alkylamine, the reaction time is 20-80 h, preferably 25-60 h.

7. The method according to claim 3, characterized in that: In step (1), the volume ratio of water to the solvent A is 2.5:1-0.7:1, preferably 2:1-1:1; after adding, the reaction is carried out for 2-15 h, preferably 4-12 h.

8. The method according to claim 3, characterized in that: In step (1), the time for standing and separating layers is 5-60 min, preferably 10-40 min.

9. The method according to claim 3, characterized in that: In step (1), the molar ratio of NaOH to phosphorus oxychloride is 10:1-3:1, preferably 8:1-4:

1.

10. The method according to claim 3, characterized in that: After layering in step (1), the upper layer liquid is under the condition of 30-32 mmHg, and the distillate at 128-132 °C is taken.

11. The method according to claim 3, characterized in that: In step (2), the solvent B is at least one of acetonitrile, benzene, toluene or tetrahydrofuran, preferably acetonitrile; the volume ratio of the solvent B to the distillate is 30:1-10:1, preferably 20:1-15:

1.

12. The method according to claim 3, characterized in that: In step (2), the solvent C is at least one of acetonitrile, benzene, toluene or tetrahydrofuran, preferably benzene.

13. The method according to claim 3, characterized in that: The volume ratio of methyl iodide to the solvent C is 1:5-1:20, preferably 1:10-1:17; the volume ratio of the solvent B to the mixture of methyl iodide and the solvent C is 1-5:1, preferably 1.5-4:1; when adding the mixture of methyl iodide and the solvent C, the flow rate is controlled at 0.5-10 mL / min, preferably 1-7 mL / min.

14. The method according to claim 3, characterized in that: In step (2), after the system returns to room temperature, the reaction continues for 24-36 h; after the reaction, atmospheric distillation is carried out at 50-150 °C; the residual liquid is washed 3-5 times with ethyl acetate, and after washing, ethyl acetate is removed by vacuum filtration.

15. The method according to claim 1, characterized in that: The addition amount of the catalyst is 5%-7.5% of the total mass of the reaction system.

16. The method according to claim 1, characterized in that: The volume ratio of acetonitrile and tetrahydrofuran in the solvent is 1-9:1, preferably 5-9:

1.

17. The method according to claim 1, 15 or 16, characterized in that: The ratio of the solvent to the catalyst is 100-200 mL:2-4.5 g.

18. The method according to claim 1, characterized in that: The molar ratio of ethylene to carbon dioxide is 1:1-1:10, preferably 1:3-1:8; the temperature of the synthesis reaction is 50-120 °C, preferably 70-100 °C; the reaction pressure is 0.5-6.0 MPa, preferably 1.0-5.5 MPa.