A process for preparing methacrylic acid from carbon dioxide and propylene
By modifying the SBA-15 solid-carrying imidazole ionic liquid catalyst in C3N4, the problem of limited application of catalyst carbon deposits and ionic liquids is solved, and efficient C3H6 and CO2 reactions are achieved, which improves the selectivity and conversion of methacrylic acid. Suitable for industrial applications.
Patent Information
- Application Number
- CN202211448161.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-11-18
- Publication Date
- 2024-12-31
- Estimated Expiration
- 2042-11-18
AI Technical Summary
In the prior art, the catalyst that directly reacts C3H6 and CO2 to generate methacrylic acid has severe carbon deposits during the reaction process, and the deactivation rate is fast, and the industrial application of ionic liquids is limited by the problems of high cost, high viscosity and difficulty in separation and recycling.
Using C3N4 modified SBA-15 solid-carrying imidazole ionic liquid catalyst, the imidazole ionic liquid is supported by modifying the SBA-15 molecular sieve support to improve the catalytic activity and realize the direct formation of methacrylic acid of C3H6 and CO2.
The activity of the catalyst and the selectivity of methacrylic acid are improved. The conversion rate of propylene can reach 9 to 13%, and the selectivity of methacrylic acid can reach 93 to 99%, and the carbon deposit problem is reduced. It is suitable for industrial applications.
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Abstract
Description
Technical Field
[0001] The invention relates to the field of carbon dioxide resource recovery and energy and environmental catalysis technology, and in particular to a process for preparing methacrylic acid from carbon dioxide and propylene. Background Art
[0002] The direct reaction of C3H6 and CO2 to produce methacrylic acid is an atom-economical reaction that can not only produce valuable chemical products, but also has great significance for reducing the greenhouse effect. In industry, methacrylic acid is widely used in methyl methacrylate, coatings, synthetic rubber, adhesives, fabric treatment agents, resins, polymer material additives and functional polymer materials, etc., and is an important part of my country's real economy. The preparation methods of methacrylic acid include ACH method, isobutylene (alcohol) oxidation method and ethylene carbonylation method. However, these preparation processes are usually divided into two or more steps, which undoubtedly increases the cost of the process. In the production process of ACH method, a large amount of waste acid and wastewater will be generated, which will cause serious environmental pollution.
[0003] Some domestic research groups have conducted some research on the topic of direct reaction of C3H6 and CO2 to produce methacrylic acid. For example, Zhong Shunhe et al. from Tianjin University used Cu and Ni modified heteropoly acid catalysts to directly produce methacrylic acid from C3H6 and CO2 in a one-step process. Under the conditions of 250-300°C, the selectivity of methacrylic acid was 92-98%, and the conversion rate of propylene was 3-5% (Journal of Catalysis, 2003, 24(9):705-710). Heteropoly acid catalysts have the advantages of low corrosiveness and easy separation from reactants and products. However, such catalysts have serious carbon deposition during the reaction process and a very fast deactivation rate, which greatly limits their industrial application.
[0004] Ionic liquids have been widely studied because of their unique properties and can achieve efficient conversion of CO2 into high value-added chemicals under low temperature conditions. Functionalized ionic liquids with specific functional groups can be used as solvents, CO2 adsorbents, and catalysts or co-catalysts to achieve efficient catalysis of CO2 under metal-free conditions. Although ionic liquids have many excellent properties and are widely used, they still have certain defects that limit their industrial application. For example, the synthesis cost of ionic liquids is high and they are difficult to use in industrial production; ionic liquids have high viscosity, which is not conducive to mass transfer and diffusion in catalytic reactions; ionic liquids have non-volatile properties and are difficult to separate and recover when the product is a non-volatile solvent, so it is particularly important to select a high-performance carrier and perform efficient immobilization. Summary of the invention
[0005] The purpose of the present invention is to improve the deficiencies of the prior art and provide a process for preparing methacrylic acid from carbon dioxide and propylene.
[0006] The technical solution of the present invention is: a process for preparing methacrylic acid from carbon dioxide and propylene, characterized in that: a C3N4-modified SBA-15 imidazole ionic liquid catalyst is used, and the imidazole ionic liquid has a solid loading of 10-40% by mass, and the catalyst can directly generate methacrylic acid from C3H6 and CO2. The specific steps are as follows:
[0007] A) Preparation of C3N4-modified SBA-15 imidazole ionic liquid catalyst:
[0008] (1) dissolving melamine, adding SBA-15 molecular sieve solid to the solution, heating, stirring, drying, and calcining to obtain C3N4-modified SBA-15 molecular sieve solid;
[0009] (2) mixing N-methylimidazole and an acidic substance, dissolving and stirring, condensing and refluxing under nitrogen protection, and filtering and drying after the reaction to obtain an ionic liquid [Hmim]X;
[0010] (3) dissolving the ionic liquid obtained in step (2), then adding the C3N4-modified SBA-15 molecular sieve solid obtained in step (1), stirring, impregnating, and drying to obtain the C3N4-modified SBA-15 imidazole ionic liquid catalyst recorded as Nwt% C3N4-SBA-15-[Hmim]X;
[0011] B) Carbon dioxide and propylene to produce methacrylic acid
[0012] A fixed bed reactor is used, a certain amount of catalyst is loaded into a reaction tube, propylene and carbon dioxide are introduced, and the temperature, pressure, and flow rates of propylene and carbon dioxide in the reaction system are controlled by a back pressure valve and a mass flow meter to react and obtain methacrylic acid.
[0013] Preferably, the mass ratio of melamine to SBA-15 molecular sieve in step A(1) is 1:(1-4); the heating and stirring temperature is 50-80°C, and the stirring time is 2-5h; the drying time is 12-16h, and the drying temperature is 80-120°C; the roasting time is 3-5h, and the roasting temperature is 450-600°C.
[0014] Preferably, the acidic substance in step A(2) is glacial acetic acid, sulfuric acid, phosphoric acid, n-butyric acid, trifluoroacetic acid, or trifluorosulfuric acid.
[0015] Preferably, the molar ratio of the acidic substance to N-methylimidazole in step A(2) is 1:(1-3); the condensation reflux time is 24-36 hours; the drying time is 12-24 hours, and the drying temperature is 60-100°C.
[0016] Preferably, the mass ratio of the C3N4-modified SBA-15 molecular sieve solid and the ionic liquid in step A (3) is (1.5-9); 1; the mass loading of the ionic liquid is 10-40%; the impregnation time is 20-36h; N in the above Nwt% C3N4-SBA-15-[Hmim]X is 10-40%, X is SO4, C4H7O2, OTf, CF3COO, H2PO4 or CH3COO; the drying temperature is 60-100°C; and the drying time is 12-24h.
[0017] Preferably, the reaction pressure in step B is 0.8-1 MPa; the reaction temperature is 250-320°C; the molar ratio of CO2 and C3H6 introduced is (10-1):1; the space velocity is 1500-3600h -1 .
[0018] SBA-15 is a porous silicon oxide material with a mesoporous structure, which is suitable for being a catalyst carrier, but the acidity of mesoporous silicon-based materials is generally very low, and SBA-15 has a relatively low concentration of acid center activity on its surface. As a new material, carbon nitride has a small specific surface area and can be well loaded on a porous material to make its surface full of amino groups. The modified SBA-15 carrier can better imidazole ionic liquids through amino groups. Therefore, a C3N4 modified SBA-15 imidazole ionic liquid catalyst prepared by the present invention can not only improve catalytic activity, but also has a higher selectivity for methacrylic acid.
[0019] Beneficial effects:
[0020] (1) The C3N4-modified SBA-15 molecular sieve used in the present invention supports an imidazole ionic liquid catalyst. The B acid provided by the imidazole ionic liquid can promote the activation of carbon dioxide into carboxylate radicals, thereby improving the selectivity of methacrylic acid. The imidazole ionic liquid can easily form a catalytically active film on the surface of the carrier, thereby making the supported imidazole ionic liquid catalyst have better catalytic activity.
[0021] (2) The catalyst of the present invention is used in the reaction of C3H6 and CO2 to generate methacrylic acid, and the conversion rate of propylene can reach 9-13%, wherein the selectivity of methacrylic acid can reach about 93-99%. DETAILED DESCRIPTION
[0022] The present invention is described in detail through the following specific examples. It should be understood that these specific examples are only used to illustrate and explain the present invention, and do not constitute any limitation to the scope of the present invention.
[0023] Example 1
[0024] Step 1. Dissolve 0.8 g of melamine in 30 mL of deionized water. When melamine is completely dissolved in deionized water, add 3.2 g of SBA-15 molecular sieve, stir vigorously for 5 h, and then evaporate the water under stirring at 50 ° C. The obtained solid is dried in an oven at 80 ° C for 16 h, and the obtained white powder is placed in a sealed porcelain boat and calcined at 450 ° C for 5 h to obtain C3N4-modified SBA-15 molecular sieve.
[0025] Step 2. Weigh 0.029 mol sulfuric acid, 0.029 mol N-methylimidazole and 40.0 ml acetonitrile, mix and add into a three-necked flask with stirring, set the reaction temperature to 70°C, condense and reflux for 36 hours under nitrogen protection. After the reaction is completed, filter out solid particles, rinse with ethyl acetate, 0.25 mol / L hydrochloric acid, deionized water and methanol respectively, put into an oven at 60°C and vacuum dry for 24 hours to obtain ionic liquid [Hmim]SO4.
[0026] Step 3. Take 4.5g of C3N4-modified SBA-15 molecular sieve and dissolve it in 100ml of ethanol, then add 0.5g of ionic liquid [Hmim]SO4, stir and soak for 20h, put it in an oven at 60℃ and vacuum dry for 24h, and the obtained substance is recorded as 10wt% C3N4-SBA-15-[Hmim]SO4.
[0027] Example 2
[0028] Step 1. Dissolve 0.8 g of melamine in 30 mL of deionized water. When melamine is completely dissolved in deionized water, add 0.8 g of SBA-15 molecular sieve, stir vigorously for 5 h, and then evaporate the water under stirring at 50 ° C. The obtained solid is dried in an oven at 120 ° C for 12 h, and the obtained white powder is placed in a sealed porcelain boat and calcined at 600 ° C for 3 h to obtain C3N4-modified SBA-15 molecular sieve.
[0029] Step 2. Weigh 0.029 mol of n-butyric acid, 0.087 mol g of N-methylimidazole and 40.0 ml of acetonitrile, add the mixture into a three-necked flask and stir, set the reaction temperature to 70°C, condense and reflux for 36 hours under nitrogen protection, after the reaction is completed, filter out the solid particles, rinse them with ethyl acetate, deionized water and methanol respectively, put them into an oven at 100°C and vacuum dry for 12 hours to obtain the ionic liquid [Hmim]C4H7O2.
[0030] Step 3. Take 4.5g of C3N4-modified SBA-15 molecular sieve and dissolve it in 100ml of ethanol, then add 3g of ionic liquid [Hmim]C4H7O2, stir and soak for 36h, put it in an oven at 100℃ and vacuum dry for 12h, and the obtained substance is recorded as 40wt% C3N4-SBA-15-[Hmim]C4H7O2.
[0031] Example 3
[0032] Step 1. Dissolve 0.8 g of melamine in 30 mL of deionized water. When melamine is completely dissolved in deionized water, add 2 g of SBA-15 molecular sieve, stir vigorously for 2 h, and then evaporate the water while stirring at 80 ° C. The obtained solid is dried in an oven at 80 ° C for 12 h, and the obtained white powder is placed in a sealed porcelain boat and calcined at 550 ° C for 3 h to obtain C3N4-modified SBA-15 molecular sieve.
[0033] Step 2. Weigh 0.029 mol trifluorosulfonic acid, 0.029 mol N-methylimidazole and 40.0 ml acetonitrile, add the mixture into a three-necked flask and stir, set the reaction temperature to 70°C, condense and reflux for 36 hours under nitrogen protection, and after the reaction, filter out solid particles, rinse with ethyl acetate, 0.25 mol / L hydrochloric acid, deionized water and methanol respectively, put into an oven at 60°C and vacuum dry for 24 hours to obtain the ionic liquid [Hmim]OTf.
[0034] Step 3. Take 4.5g of C3N4-modified SBA-15 molecular sieve and dissolve it in 100ml of ethanol, then add 0.5g of ionic liquid [Hmim]OTf, stir and soak for 20h, put it in an oven at 60℃ and vacuum dry for 24h, and the obtained substance is recorded as 10wt% C3N4-SBA-15-[Hmim]OTf.
[0035] Example 4
[0036] Step 1. Dissolve 0.8 g of melamine in 30 mL of deionized water. When melamine is completely dissolved in deionized water, add 2 g of SBA-15 molecular sieve, stir vigorously for 3 h, then evaporate the water while stirring at 70 ° C, dry the obtained solid in an oven at 80 ° C for 12 h, put the obtained white powder into a sealed porcelain boat, and calcine at 550 ° C for 3 h to obtain C3N4 modified SBA-15 molecular sieve.
[0037] Step 2. Weigh 0.029 mol trifluoroacetic acid, 0.029 mol N-methylimidazole and 40.0 ml acetonitrile, add the mixture into a three-necked flask and stir. Set the reaction temperature to 70°C. Condensate and reflux for 32 hours under nitrogen protection. After the reaction is completed, filter out the solid particles, rinse them with ethyl acetate, deionized water and methanol respectively, put them into an oven at 65°C and vacuum dry for 18 hours to obtain the ionic liquid [Hmim]CF3COO.
[0038] Step 3. Take 4.5g of C3N4-modified SBA-15 molecular sieve and dissolve it in 100ml of ethanol, then add 1.125g of ionic liquid [Hmim]CF3COO, stir and soak for 24h, put it in an oven at 65℃ and vacuum dry for 18h, and the obtained substance is recorded as 20wt% C3N4-SBA-15-[Hmim]CF3COO.
[0039] Example 5
[0040] Step 1. Dissolve 0.8 g of melamine in 30 mL of deionized water. When melamine is completely dissolved in deionized water, add 2 g of SBA-15 molecular sieve, stir vigorously for 2 h, and then evaporate the water while stirring at 80 ° C. The obtained solid is dried in an oven at 80 ° C for 12 h, and the obtained white powder is placed in a sealed porcelain boat and calcined at 550 ° C for 3 h to obtain C3N4-modified SBA-15 molecular sieve.
[0041] Step 2. Weigh 0.029 mol phosphoric acid, 0.029 mol N-methylimidazole and 40.0 ml acetonitrile, mix and add into a three-necked flask, set the reaction temperature to 70°C, condense and reflux for 32 hours under nitrogen protection. After the reaction is completed, filter out solid particles, rinse with ethyl acetate, 0.25 mol / L hydrochloric acid, deionized water and methanol respectively, put into an oven at 65°C and vacuum dry for 18 hours to obtain ionic liquid [Hmim]H2PO4.
[0042] Step 3. Take 4.5g of C3N4-modified SBA-15 molecular sieve and dissolve it in 100ml of ethanol, then add 0.5g of ionic liquid [Hmim]H2PO4, stir and soak for 24h, put it in an oven at 65℃ and vacuum dry for 18h, and the obtained substance is recorded as 10wt% C3N4-SBA-15-[Hmim]H2PO4.
[0043] Example 6
[0044] Step 1. Dissolve 0.8 g of melamine in 30 mL of deionized water. When melamine is completely dissolved in deionized water, add 2 g of SBA-15 molecular sieve, stir vigorously for 2 h, and then evaporate the water while stirring at 80 ° C. The obtained solid is dried in an oven at 80 ° C for 12 h, and the obtained white powder is placed in a sealed porcelain boat and calcined at 550 ° C for 3 h to obtain C3N4-modified SBA-15 molecular sieve.
[0045] Step 2. Weigh 0.029 mol glacial acetic acid, 0.029 mol g N-methylimidazole and 40.0 ml acetonitrile, mix and add into a three-necked flask, set the reaction temperature to 70 ° C, condense and reflux for 32 hours under nitrogen protection. After the reaction is completed, filter out solid particles, rinse with ethyl acetate, 0.25 mol / L hydrochloric acid, deionized water and methanol respectively, put into an oven at 65 ° C and vacuum dry for 18 hours to obtain ionic liquid [Hmim] CH3COO.
[0046] Step 3. Take 4.5g of C3N4-modified SBA-15 molecular sieve and dissolve it in 100ml of ethanol, then add 0.5g of ionic liquid [Hmim]CH3COO, stir and soak for 24h, put it in an oven at 65℃ and vacuum dry for 18h, and the obtained substance is recorded as 10wt% C3N4-SBA-15-[Hmim]CH3COO.
[0047] Application Example 1
[0048] The present invention prepares a C3N4 modified SBA-15 imidazole ionic liquid catalyst to catalyze C3H6 and CO2 to directly prepare methacrylic acid. A fixed bed reactor is used to load 1.6 g of 10 wt% C3N4-SBA-15-[Hmim]SO4 catalyst (prepared in Example 1) into a reaction tube with an inner diameter of 12 mm and a length of 60 cm. The reaction is carried out at 250° C., 0.8 MPa, and a space velocity of 3600 h -1 , CO2 and C3H6 molar ratio = 10:1, the results are shown in Table 1.
[0049] Application Example 2
[0050] The present invention prepares a C3N4 modified SBA-15 imidazole ionic liquid catalyst to catalyze C3H6 and CO2 to directly prepare methacrylic acid. Using a fixed bed reactor, 2.5 g of 40 wt% C3N4-SBA-15-[Hmim]C4H7O2 catalyst (prepared in Example 2) is loaded into a reaction tube with an inner diameter of 12 mm and a length of 60 cm, and heated at 260°C, 0.9 MPa, and a space velocity of 1500 h -1 , CO2 and C3H6 molar ratio = 2:1, the results are shown in Table 1.
[0051] Application Example 3
[0052] The present invention prepares a C3N4 modified SBA-15 imidazole ionic liquid catalyst to catalyze C3H6 and CO2 to directly prepare methacrylic acid. A fixed bed reactor is used to load 2g of 10wt% C3N4-SBA-15-[Hmim]OTf catalyst (prepared in Example 3) into a reaction tube with an inner diameter of 12mm and a length of 60cm. The reaction is carried out at 320°C, 1MPa, and a space velocity of 3600h / min. -1, the molar ratio of CO2 and C3H6 = 5:1, the results are shown in Table 1.
[0053] Application Example 4
[0054] The present invention prepares a C3N4 modified SBA-15 imidazole ionic liquid catalyst to catalyze C3H6 and CO2 to directly prepare methacrylic acid. A fixed bed reactor is used to load 1.6 g of 20 wt% C3N4-SBA-15-[Hmim]CF3COO catalyst (prepared in Example 4) into a reaction tube with an inner diameter of 12 mm and a length of 60 cm. The reaction is carried out at 280° C., 0.8 MPa, and a space velocity of 2600 h -1 , the molar ratio of CO2 and C3H6 = 2:1, the results are shown in Table 1.
[0055] Application Example 5
[0056] The present invention prepares a C3N4 modified SBA-15 imidazole ionic liquid catalyst to catalyze C3H6 and CO2 to directly prepare methacrylic acid. A fixed bed reactor is used to load 1.6 g of 10 wt% C3N4-SBA-15-[Hmim]H2PO4 catalyst (prepared in Example 5) into a reaction tube with an inner diameter of 12 mm and a length of 60 cm. The reaction is carried out at 280° C., 0.8 MPa, and a space velocity of 2400 h -1 , the molar ratio of CO2 and C3H6 = 2:1, the results are shown in Table 1.
[0057] Application Example 6
[0058] The present invention prepares a C3N4 modified SBA-15 imidazole ionic liquid catalyst to catalyze C3H6 and CO2 to directly prepare methacrylic acid. Using a fixed bed reactor, 2g of 10wt% C3N4-SBA-15-[Hmim]CH3COO. catalyst (prepared in Example 6) is loaded into a reaction tube with an inner diameter of 12mm and a length of 60cm, and heated at 280°C and 0.8MPa with a space velocity of 2400h -1 , the molar ratio of CO2 and C3H6 = 3:1. The results are shown in Table 1.
[0059] Table 1 Results of the reaction of carbon dioxide and propylene to methacrylic acid using different catalysts
[0060]
Claims
1. A process for preparing methacrylic acid from carbon dioxide and propylene, the specific steps of which are as follows: A) Preparation of C3N4-modified SBA-15 imidazole ionic liquid catalyst: (1) dissolving melamine, adding SBA-15 molecular sieve solid to the solution, heating, stirring, drying, and calcining to obtain C3N4-modified SBA-15 molecular sieve solid; (2) mixing N-methylimidazole and an acidic substance, dissolving and stirring, condensing and refluxing under nitrogen protection, filtering and drying after the reaction to obtain an ionic liquid; wherein the acidic substance is glacial acetic acid, sulfuric acid, phosphoric acid, n-butyric acid, trifluoroacetic acid or trifluorosulfuric acid; (3) dissolving the ionic liquid obtained in step (2), then adding the C3N4-modified SBA-15 molecular sieve solid obtained in step (1), stirring, impregnating, and drying to obtain the C3N4-modified SBA-15 imidazole ionic liquid catalyst; B) Carbon dioxide and propylene to produce methacrylic acid A fixed bed reactor is used, a certain amount of catalyst is loaded into a reaction tube, propylene and carbon dioxide are introduced, the temperature, pressure, and flow rates of propylene and carbon dioxide in the reaction system are controlled, and methacrylic acid is obtained by reaction.
2. The process according to claim 1, characterized in that: The mass ratio of melamine to SBA-15 molecular sieve in step A(1) is 1:(1-4); the heating and stirring temperature is 50-80°C and the stirring time is 2-5h; the drying time is 12-16h and the drying temperature is 80-120°C; the roasting time is 3-5h and the roasting temperature is 450-600°C.
3. The process according to claim 1, characterized in that: The molar ratio of the acidic substance to N-methylimidazole in step A(2) is 1:(1-3); the condensation reflux time is 24-36 hours; the drying time is 12-24 hours, and the drying temperature is 60-100°C.
4. The process according to claim 1, characterized in that: The mass ratio of the C3N4-modified SBA-15 molecular sieve solid to the ionic liquid in step A(3) is (1.5-9); 1; the impregnation time is 20-36 hours; the drying temperature is 60-100°C; and the drying time is 12-24 hours.
5. The process according to claim 1, characterized in that: In step B, the reaction pressure is 0.8-1 MPa; the reaction temperature is 250-320°C; the molar ratio of CO2 and C3H6 introduced is (10-1):1; the space velocity is 1500-3600 h -1 .