A process for the preparation of propylene carbonate

Abstract

The application discloses a preparation method of propylene carbonate, and belongs to the technical field of fine chemical industry and heterogeneous catalysis, namely, taking propylene oxide and carbon dioxide as raw materials, and realizing synthesis of propylene carbonate under the action of an amino metal organic framework material loaded nano Ag catalyst under mild conditions; under the conditions that the reaction temperature is 60-100 DEG C, the reaction pressure is 1-3 MPa, the stirring speed is 400-800 r / min, and the reaction time is 90-180 min, the selectivity of propylene carbonate is all greater than 99%, and the yield can be up to 98.7%. The catalyst preparation method is simple, the price is low, CO2 can be converted into the high-value-added chemical propylene carbonate under relatively mild conditions, and the catalyst has a good industrial application prospect.

Description

Technical Field

[0001] This invention belongs to the fields of fine chemical technology and heterogeneous catalysis technology, and relates to a method for preparing propylene carbonate. Background Technology

[0002] Propylene carbonate (PC) is an important cyclic organic carbonate product in the new energy field. It can be synthesized using greenhouse gas CO2 as a main raw material, making it a crucial chemical product for the high-value recycling of CO2. Propylene carbonate is characterized by low toxicity, high boiling point, and good stability, and is widely used in key areas such as specialty environmentally friendly solvents and biodegradable materials. These include lithium-ion battery electrolytes, polar solvents, biodegradable polymer monomers, pharmaceutical and fine chemical intermediates, and ingredients in cosmetics and personal care products. It can also be used to co-produce dimethyl carbonate and propylene glycol, making it a very important industrial product.

[0003] Currently, the main reported methods for PC synthesis include the following: phosgene method, urea alcoholysis method, CO2-propylene oxide (PO) carboxylation method, CO2-propylene glycol method, CO2-chloropropanol method, and direct synthesis of propylene with CO2. The phosgene method was the earliest industrially commercialized method for PC production, primarily using 1,2-propanediol and phosgene (COCl2) as raw materials for chemical reaction. However, phosgene is a highly toxic chemical with significant environmental hazards. Furthermore, this method produces large amounts of hydrogen chloride as a byproduct, causing severe equipment corrosion; therefore, this synthesis method has been phased out. The urea alcoholysis method is another industrialized PC synthesis method. This method uses expensive propylene glycol as a raw material, and its low-temperature synthesis is thermodynamically limited, while high-temperature synthesis suffers from high energy consumption, thus limiting its widespread application. There are also some reports on the synthesis of propylene carbonate using the CO2-propylene glycol method, the CO2-chloropropanol method, and the direct synthesis of propylene with CO2, but these are still in the laboratory research stage. Currently, the CO2-PO carboxylation synthesis of propylene carbonate is the most widely used PC synthesis method in industrial applications.

[0004] Homogeneous metal complex catalysts are the most widely studied and applied CO2-PO carboxylation catalysts to date. However, the complex structure and high preparation cost of metal complexes severely limit their large-scale application. Ionic liquid catalysts are also widely used in the CO2-PO carboxylation reaction. Chinese patent CN 111978285 A discloses a method for preparing propylene carbonate (or propylene carbonate) using an amino-functionalized composite ionic liquid. At 3 MPa, 130℃, and 2 h, the yield of propylene carbonate reaches over 99%. However, this method requires a high temperature setting and stringent reaction conditions. Chinese patent CN 104650026 B discloses a method for preparing propylene carbonate. This method uses a carboxyl-terminated polyether ionic liquid catalyst to achieve the carbonylation reaction of carbon dioxide and propylene oxide, with propylene oxide conversion rates exceeding 98%. However, this method suffers from a high catalyst viscosity, making uniform stirring during the catalytic process impossible. In this case, an additional amount of propylene carbonate of the same mass as the catalyst needs to be added as a solvent for dilution to ensure efficient reaction. Therefore, although homogeneous catalysts are widely used in industrial production due to their good catalytic effect, they also face challenges such as complex synthesis process, high cost, and difficulty in separation after use. Moreover, most homogeneous catalysts can only be used in batch reactors and require the assistance of various solvents or additives.

[0005] Currently, numerous studies have demonstrated that heterogeneous catalysts can effectively catalyze the carboxylation of CO2-PO to synthesize PC, offering significant advantages such as simple synthesis processes, low cost, easy separation, good thermal stability, and reusability. Therefore, developing efficient heterogeneous catalysts to replace homogeneous catalysts has become an important trend in the field of catalysis. Several heterogeneous catalytic systems have been reported, including homogeneous supported catalysts, metal oxide catalysts, and MOF catalysts. However, these systems still suffer from problems such as complex catalyst preparation processes, typically requiring high temperature and pressure, high energy consumption, and long reaction times. Therefore, finding a green, efficient, mild, and convenient method for the synthesis of propylene carbonate holds significant promise for industrial applications. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides a simple, low-cost, green, and highly efficient method for preparing a heterogeneous catalyst, and applies it under mild conditions to the carboxylation reaction of propylene oxide with CO2. The catalyst of this invention avoids the use of expensive materials, is easy to prepare, exhibits high catalytic activity, and achieves conversion and selectivity both exceeding 95%, demonstrating promising prospects for industrial application.

[0007] The technical solution of the present invention:

[0008] A method for preparing propylene carbonate, comprising the following steps:

[0009] Using propylene oxide as a raw material, an amino-metal-organic framework (MOF) supported nano-Ag catalyst as the main catalyst and tetrabutylammonium bromide as the co-catalyst was used to synthesize propylene carbonate with high selectivity in a high-pressure autoclave reactor under the following conditions: reaction temperature 60–100℃, reaction pressure 1–3 MPa, stirring speed 400–800 r / min, and reaction time 90–180 min. The chemical formula of the amino-metal-organic framework supported nano-Ag catalyst is Ag / xPEI@UIO-66-NH2, where x is the mass ratio of introduced polyethyleneimine (PEI) to the MOF material (x = 0.3–0.7), and the loading of Ag is 3–15 wt.%.

[0010] The mass ratio of the aminated metal-organic framework material-supported nano-Ag catalyst to propylene oxide is 1:(48.5-147), and the mass ratio of the aminated metal-organic framework material-supported nano-Ag catalyst to the co-catalyst tetrabutylammonium bromide is 1:(0.065-0.02).

[0011] The aminated metal-organic framework material-supported nano-Ag catalyst was prepared by solvothermal synthesis, post-modification synthesis, and in-situ impregnation and reduction with AgNO3, as follows:

[0012] (1) The aminated metal-organic framework material PEI@UIO-66-NH2 was prepared and synthesized by the method reported in the reference (Separation and Purification Technology 292 (2022) 121470).

[0013] (2) Dissolve 1 part silver nitrate in 19 parts methanol, then add 12 parts aminated metal-organic framework material, react for 3 h, centrifuge and dry, then dissolve the dried solid in deionized water, add excess reducing agent and stir for 3-4 h, then wash, centrifuge and dry to obtain the aminated metal-organic framework material supported nano-Ag catalyst.

[0014] The beneficial effects of this invention are: the reaction conditions of this invention are mild, the operation is simple, the catalyst has high catalytic activity, it avoids the energy consumption and dangers caused by traditional high temperature and high pressure, the catalyst is easy to separate and recover, it conforms to the atom economy concept, and provides a new idea for low-cost industrial synthesis of propylene carbonate. Attached Figure Description

[0015] Figure 1 This is a graph showing the reactivity of propylene oxide with CO2 under different reaction pressures. Detailed Implementation

[0016] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and technical solutions.

[0017] Example 1: Preparation of Ag / PEI@UIO-66-NH2

[0018] 0.6438 g of zirconium chloride powder and 0.5108 g of 2-aminoterephthalic acid were weighed and dissolved and dispersed in 50 mL of DMF solution. The mixture was stirred for 2 h until the solid was completely dissolved. The solution was then transferred to a hydrothermal reactor and reacted at 130 °C for 24 h. After the reaction was completed, the hydrothermal reactor was cooled to room temperature, and a yellow solid was obtained by centrifugation. The solid was then washed several times with DMF and anhydrous ethanol and dried in a conventional oven for 12 h to obtain solid UIO-66-NH2.

[0019] Weigh 0.5711 g UIO-66-NH2 and dissolve and disperse it in 25 mL of 5% glutaraldehyde in anhydrous ethanol solution. React at 100 °C for 10 h, then wash and dry with anhydrous ethanol to obtain UIO-66-GD.

[0020] Weigh 0.2g of polyethyleneimine and dissolve and disperse it in 20mL of ethanol. Add 0.2g of UIO-66-GD while stirring. React at 50℃ for 12h. Then wash and dry with anhydrous ethanol to obtain PEI@UIO-66-NH2.

[0021] Weigh 0.0167 g of silver nitrate and dissolve and disperse it in 10 mL of methanol solution. Add 0.2 g of PEI@UIO-66-NH2 to the above solution, stir at room temperature for 3 h, centrifuge, and dry in vacuum at 40 °C for 3 h. Then dissolve and disperse the dried solid in 10 mL of water. Dissolve 2 times the amount of AgNO3 in 2 mL of deionized water and add it dropwise to the above solution. Stir at room temperature for 3 h to obtain the Ag / PEI@UIO-66-NH2 catalyst.

[0022] Examples 2-3

[0023] The conditions were the same as in Example 1, except that the amount of polyethyleneimine added each time was changed from 0.2g to 0.06g and 0.14g, respectively, to obtain Ag / 0.3PEI@UIO-66-NH2 and Ag / 0.7PEI@UIO-66-NH2.

[0024] Examples 4-6

[0025] The conditions were the same as in Example 1, except that the amount of silver nitrate added each time was changed from 0.0167g to 0.0100g, 0.0353g, and 0.0560g, respectively, to obtain 3wt.%Ag / PEI@UIO-66-NH2, 10wt.%Ag / PEI@UIO-66-NH2, and 15wt.%Ag / PEI@UIO-66-NH2.

[0026] Example 7 (Effect of Different Pressures)

[0027] The catalytic performance of the Ag / PEI@UIO-66-NH2 catalyst in Example 1 was studied in the carboxylation reaction of propylene oxide and CO2. The reaction was carried out in a high-temperature and high-pressure reactor.

[0028] The reaction conditions were as follows: 0.15 g catalyst (Ag / PEI@UIO-66-NH2), 14.52 g propylene oxide, 0.4621 g tetrabutylammonium bromide, reaction pressures of 1 MPa, 1.5 MPa, 2 MPa, 2.5 MPa, and 3 MPa, reaction temperature of 80 °C, and reaction time of 1.5 h. The products were analyzed by 1H NMR spectroscopy, and the reaction results are as follows:

[0029]

[0030] Example 8 (Effect of different temperatures)

[0031] The catalytic performance of the Ag / PEI@UIO-66-NH2 catalyst in Example 1 was studied in the carboxylation reaction of propylene oxide and CO2. The reaction was carried out in a high-temperature and high-pressure reactor.

[0032] The reaction conditions were: 0.15 g catalyst (Ag / PEI@UIO-66-NH2), 14.52 g propylene oxide, 0.4621 g tetrabutylammonium bromide, reaction pressure of 2.5 MPa, reaction temperatures of 60℃, 70℃, 80℃ and 90℃, and reaction time of 1.5 h. The products were analyzed by 1H NMR spectroscopy, and the reaction results are as follows:

[0033]

[0034]

[0035] Example 9 (Effect of different PEI introduction amounts)

[0036] The catalytic performance of the catalysts described in Examples 2 and 3 in the carboxylation reaction of propylene oxide and CO2 was studied. The reaction was carried out in a high-temperature and high-pressure reactor.

[0037] The reaction conditions were: 0.15 g catalyst, 14.52 g propylene oxide, 0.4621 g tetrabutylammonium bromide, reaction pressure 2.5 MPa, reaction temperature 80 °C, and reaction time 1.5 h. The product was analyzed by 1H NMR spectroscopy, and the reaction results are as follows:

[0038]

[0039] Example 10 (Effect of different metal loading amounts)

[0040] The catalytic performance of the catalysts described in Examples 1, 4, 5, and 6 in the carboxylation reaction of propylene oxide and CO2 was studied. The reaction was carried out in a high-temperature and high-pressure reactor.

[0041] The reaction conditions were: 0.15 g catalyst, 14.52 g propylene oxide, 0.4621 g tetrabutylammonium bromide, reaction pressure 2.5 MPa, reaction temperature 80 °C, and reaction time 1.5 h. The product was analyzed by 1H NMR spectroscopy, and the reaction results are as follows:

[0042]

[0043] Example 11 (Effect of different reaction times)

[0044] The catalytic performance of the catalyst described in Example 1 in the carboxylation reaction of propylene oxide and CO2 was studied. The reaction was carried out in a high-temperature and high-pressure reactor.

[0045] The reaction conditions were: 0.15 g catalyst, 14.52 g propylene oxide, 0.4621 g tetrabutylammonium bromide, reaction pressure of 2.5 MPa, and reaction temperature of 80 °C. The product was analyzed by 1H NMR spectroscopy, and the results are as follows:

[0046]

Claims

1. A method for preparing propylene carbonate, characterized in that, The steps are as follows: Using propylene oxide as a raw material, an amino-metal-organic framework supported nano-Ag catalyst as the main catalyst and tetrabutylammonium bromide as the co-catalyst were used to synthesize propylene carbonate with high selectivity in a high-pressure autoclave reactor under the following conditions: reaction temperature 60–100℃, reaction pressure 1–3MPa, stirring speed 400–800 r / min, and reaction time 90–180 min. The chemical formula of the amino-metal-organic framework supported nano-Ag catalyst is Ag / xPEI@UIO-66-NH2, where x is the mass ratio of introduced PEI to the metal-organic framework material.

2. The preparation method according to claim 1, characterized in that, In Ag / xPEI@UIO-66-NH2, x = 0.3 to 0.

7.

3. The preparation method according to claim 1, characterized in that, The loading of metallic Ag in the aminated metal-organic framework supported nano-Ag catalysts is 3–15 wt.%.

4. The preparation method according to claim 1, characterized in that, The mass ratio of the aminated metal-organic framework material-supported nano-Ag catalyst to propylene oxide is 1:(48.5-147), and the mass ratio of the aminated metal-organic framework material-supported nano-Ag catalyst to the co-catalyst tetrabutylammonium bromide is 1:(0.065-0.02).

5. The preparation method according to claim 1, characterized in that, The preparation steps of the aminated metal-organic framework material supported on nano-Ag catalyst are as follows: (1) Preparation of aminated metal-organic framework material PEI@UIO-66-NH2; (2) Dissolve 1 part silver nitrate in 19 parts methanol, then add 12 parts aminated metal-organic framework material, react for 3 h, centrifuge and dry, then dissolve the dried solid in deionized water, add excess reducing agent and stir for 3-4 h, then wash, centrifuge and dry to obtain the aminated metal-organic framework material supported nano-Ag catalyst.

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