Use of phosphazene compounds as catalysts in the reaction of epoxides with carbon dioxide to form cyclic carbonates

Abstract

This invention relates to the application of phosphazene compounds as catalysts in the reaction of epoxides with carbon dioxide to generate cyclic carbonates, as well as methods for preparing cyclic carbonates and methods for preparing cyclic carbonate-terminated polymers. The phosphazene compounds have the structure shown in formula (1) or (2). This invention mainly solves the problems of insufficient catalyst activity and low yield of target products in the prior art using cyclic carbonate processes. At the same time, it can prepare cyclic carbonate-terminated polyethers in a one-pot process.

Description

Technical Field

[0001] This invention relates to the field of cyclic carbonates, and more specifically, to the application of a phosphazene compound as a catalyst in the reaction of an epoxide with carbon dioxide to produce cyclic carbonates, as well as methods for preparing cyclic carbonates and methods for preparing cyclic carbonate-terminated polyethers. Background Technology

[0002] Cyclic carbonates are widely used in product manufacturing, including solvents, paint removers, lithium batteries, biodegradable packaging, and pharmaceutical synthesis. Catalysts include metal complexes, metalloporphyrins, ionic liquids, organometallic frameworks (MOFs), quaternary onium salts, and inorganic catalysts.

[0003] Quaternary onium salt catalysts, such as quaternary ammonium salts and quaternary phosphorus salts, are commonly used as catalysts (primarily providing halogens) to open the rings of alkyl epoxides, making them also a class of simple and efficient catalysts for the catalytic formation of cyclic carbonates. The reaction of ethylene oxide and CO2 to ethylene carbonate via tetraethylammonium bromide (TEAB) and tetrabutylphosphine iodide (TBPI) has been commercialized. Summary of the Invention

[0004] The technical problem to be solved by the present invention is that the existing technology of using cyclic carbonate processes has problems such as insufficient catalyst activity and low yield of target product. At the same time, it can also prepare cyclic carbonate-terminated polymers such as cyclic carbonate-terminated polyethers in a one-pot process.

[0005] To address the aforementioned technical problems, one objective of this invention is to provide the application of phosphazene compounds as catalysts in the reaction of epoxides with carbon dioxide to form cyclic carbonates.

[0006] The phosphazene compound has the structure shown in formula (1) or (2):

[0007]

[0008] Among them, Ra, Rb, Rc, and Rd are each independently...

[0009] R1, R2, R3, and R4 are each independently an alkyl group having 1 to 10 carbon atoms, an unsubstituted or substituent phenyl group having 6 to 10 carbon atoms, or an unsubstituted or substituent phenylalkyl group having 6 to 10 carbon atoms; wherein in formula (1), R1 and R2 can bond with each other to form a ring structure, and in formula (2), R1, R2, R3, and R4 can bond with each other to form a ring structure;

[0010] n is an integer from 1 to 8, representing the number of phosphorus cations in the phosphazene compound; Z n- It is an n-valent anion.

[0011] In the phosphazene compound shown in formula (2),

[0012] Ra, Rb, Rc, and Rd can all be simultaneously... or simultaneously They can also be respectively

[0013] According to a preferred embodiment of the present invention:

[0014] R1, R2, R3, and R4 are each independently an alkyl group having 1 to 8 carbon atoms, an unsubstituted or substituent phenyl group having 6 to 8 carbon atoms, or an unsubstituted or substituent phenylalkyl group having 6 to 8 carbon atoms.

[0015] n is an integer from 1 to 3;

[0016] Z n- The ions are chloride ions, chlorate ions, phosphate ions, hydrogen phosphate ions, methyloxo ions, and ethyloxo ions.

[0017] The epoxy compound may be selected from at least one of ethylene oxide, propylene oxide, 1,2-epoxybutane, phenylene oxide, and cyclohexene oxide.

[0018] The second objective of this invention is to provide a method for preparing cyclic carbonates, comprising reacting an epoxy compound with carbon dioxide under the catalysis of a phosphazene compound having the structure shown in formula (1) or (2) to obtain cyclic carbonates.

[0019] The epoxy compound is selected from compounds such as ethylene oxide, propylene oxide, 1,2-epoxybutane, phenylene oxide, and cyclohexene oxide. Two or more of these compounds can be used in combination. When using a mixture of them, several epoxides can be used simultaneously, sequentially, or in a repeated sequence. Ethylene oxide and propylene oxide are preferred.

[0020] The amount of phosphazene compound represented by general formula (1) or (2) is not particularly limited, but the range of amounts is generally relative to the amount of phosphazene compound per mole of epoxy compound, where the amount of phosphazene compound is 1 × 10⁻⁶. -10 ~1×10 -1 moles, preferably 1×10 -7 ~1×10 -1 Between moles, specifically 1 × 10 -7 mole, 1×10 -6 mole, 1×10 -5 mole, 1×10 -4 mole, 1×10 -3 mole, 1×10 -2 mole, 1×10-1 Moore, etc.

[0021] The polymerization reaction steps in the method for preparing the cyclic carbonate of the present invention are not particularly limited. Generally, a method is used in which an epoxy compound is added to the reactor in a one-time, intermittent or continuous manner, in which the phosphazene compound represented by general formula (1) or (2) is added together with a solvent (when used).

[0022] In the method for preparing the cyclic carbonate of the present invention, the reaction temperature is between 10 and 180°C, preferably between 30 and 150°C, and more preferably between 60 and 130°C.

[0023] In the method for preparing the cyclic carbonate of the present invention, the reaction pressure is not higher than 3.0 MPa, preferably between 0.01 and 1.5 MPa, more preferably between 0.1 and 1.0 MPa, and specifically can be 0.1 MPa, 1 MPa, 1.5 MPa, 2 MPa, etc.

[0024] In the method for preparing cyclic carbonates of the present invention, the reaction time varies depending on the type and amount of the substance used, the polymerization temperature and pressure, and is preferably 0.1 to 50 hours, more preferably in the range of 0.5 to 30 hours.

[0025] In the method for preparing cyclic carbonates of the present invention, two or more epoxide compounds can be used in combination, simultaneously, or added sequentially and repeatedly.

[0026] In the method for preparing the cyclic carbonate of the present invention, a solvent may be used if necessary. The solvents used include, for example, aliphatic hydrocarbons such as pentane, hexane, heptane, cyclohexane, etc.; aromatic hydrocarbons such as benzene, toluene, etc.; ethers such as diethyl ether, tetrahydrofuran, anisole, etc.; and aprotic solvents such as dimethyl sulfoxide, N,N-dimethylformamide, etc. In addition to these, any solvent can be used, as long as it does not inhibit the polymerization reaction of the method of the present invention.

[0027] In the method for preparing cyclic carbonates of the present invention, the polymerization reaction can also be carried out in the presence of an inert gas such as nitrogen or argon, depending on the need.

[0028] The third objective of this invention is to provide a method for preparing cyclic carbonate-terminated polyethers, comprising the following steps:

[0029] 1) The initiator is reacted with the epoxy compound under the catalysis of a phosphazene compound having the structure shown in formula (1) or (2);

[0030] 2) After the reaction in step 1) is complete, an epoxy compound containing halogenated atoms is added to continue the reaction. Then carbon dioxide is introduced to carry out the reaction, and finally the cyclic carbonate-terminated polyether is obtained.

[0031] The epoxy compound is selected from compounds such as ethylene oxide, propylene oxide, 1,2-epoxybutane, and phenylene oxide.

[0032] The initiator has active hydrogen, preferably an active hydrogen compound containing a hydroxyl group or an active hydrogen compound containing an amino group.

[0033] The active hydrogen compound containing hydroxyl groups is preferably at least one of the following: alcohols having 1 to 20 carbon atoms, polyhydroxy alcohols having 2 to 20 carbon atoms and having 2 to 8 hydroxyl groups, and polyether polyols having 2 to 8 end groups and having 1 to 8 hydroxyl groups on the end groups.

[0034] The active hydrogen compound containing an amine group is preferably a polyamine with 2 to 20 carbon atoms and 2 to 3 primary or secondary amine groups, or a cyclic polyamine with 4 to 10 carbon atoms and 2 to 3 secondary amine groups.

[0035] The number average molecular weight of the polyether polyol is preferably 200 to 30,000.

[0036] The epoxy compound containing halogenated atoms is epichlorohydrin.

[0037] In the preparation method of the cyclic carbonate-terminated polyether of the present invention, in step (1),

[0038] The phosphazene compound is 1 to 10 wt‰ of cyclic carbonate-terminated polyether, preferably 1 to 6 wt‰.

[0039] The reaction pressure is less than 0.4 MPa, and the reaction temperature is 70–100 °C.

[0040] In the preparation method of the cyclic carbonate-terminated polyether of the present invention, in step (2),

[0041] The reaction temperature is between 10 and 180°C, preferably between 30 and 150°C, and more preferably between 60 and 130°C. The reaction pressure is not higher than 3.0 MPa, preferably between 0.01 and 1.5 MPa, and more preferably between 0.1 and 1.0 MPa. The reaction time varies depending on the type and amount of the substance used, the polymerization temperature, and the pressure, and is preferably between 0.1 and 50 hours, and more preferably between 0.5 and 30 hours.

[0042] In the method for preparing the cyclic carbonate-terminated polyether of the present invention, a solvent may be used if necessary. The solvents used include, for example, aliphatic hydrocarbons such as pentane, hexane, heptane, cyclohexane, etc.; aromatic hydrocarbons such as benzene, toluene, etc.; ethers such as diethyl ether, tetrahydrofuran, anisole, etc.; and aprotic solvents such as dimethyl sulfoxide, N,N-dimethylformamide, etc. In addition to these, any solvent can be used, as long as it does not inhibit the polymerization reaction of the method of the present invention.

[0043] In the preparation method of the cyclic carbonate-terminated polyether of the present invention, the polymerization reaction can also be carried out in the presence of an inert gas such as nitrogen or argon, depending on the need.

[0044] The phosphazene compound catalyst described in this invention can not only catalyze the polymerization of propylene oxide, but also catalyze the formation of cyclic carbonates from carbon dioxide and epoxy compounds, and can be used for one-pot preparation of polymers with cyclic carbonate end groups.

[0045] Polyethers with cyclic carbonate end groups can be used to react with amines to synthesize non-isocyanate polyurethanes, avoiding the use of highly toxic isocyanates and offering certain performance advantages. Cyclic carbonate end-group polyethers are typically synthesized by ring-opening polymerization catalyzed by catalysts such as KOH and NaOH, followed by epichlorohydrin end-group capping, and then the addition of a catalyst for synthesizing cyclic carbonates, such as tetraethylammonium bromide. The method of this invention uses only one catalyst, achieving a one-pot synthesis of cyclic carbonate end-group polyethers, simplifying existing processes and possessing certain industrial application value.

[0046] The present invention will now be described in more detail through embodiments, but the present invention should not be limited to the following embodiments. Attached Figure Description

[0047] Figure 1 The image shows the 1H NMR spectrum of the product from Example 5.

[0048] Figure 2 The hydrogen NMR spectrum of product 9 was obtained. Detailed Implementation

[0049] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0050] Unless otherwise specified, the raw materials used in the examples and comparative examples are all disclosed in the prior art, such as those that can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0051] This application uses the phosphazene compound shown in formula (1) or (2):

[0052]

[0053]

[0054] Among them, Ra, Rb, Rc, and Rd are each independently...

[0055] In the above general formulas (1) and (2), R1, R2, R3 and R4 are each independently an alkyl group with 1 to 10 carbon atoms, an unsubstituted or substituent phenyl group with 6 to 10 carbon atoms, or an unsubstituted or substituent phenylalkyl group with 6 to 10 carbon atoms;

[0056] n is an integer from 1 to 8, representing the number of phosphorus cations in the phosphazene compound.

[0057] Z n- Representing n-valent anions, these can be monovalent or polyvalent anions such as chloride ions, chlorate ions, phosphate ions, hydrogen phosphate ions, methyloxo ions, and ethyloxo ions.

[0058] These phosphazene compounds represented by general formulas (1) and (2) can be synthesized by the method described in Zeitschriftfuer Naturforschung, B: Chemical Sciences, Vol. 59, p. 499 (2004) or a similar method.

[0059] According to a preferred embodiment of the present invention, the method for preparing the cyclic carbonate includes: adding a phosphazene compound and an epoxy compound of formula (1) or (2) into a reaction vessel, introducing carbon dioxide, reacting, and distilling the product under reduced pressure to obtain the cyclic carbonate.

[0060] According to a preferred embodiment of the present invention, the method for preparing the cyclic carbonate-terminated polyester includes: adding a phosphazene compound of formula (1) or (2) and a polyether polyol to a reaction vessel, replacing the vessel with a protective gas atmosphere, drying the vessel, introducing an epoxy compound, and reacting the reaction vessel; after the reaction is completed, adding an epoxy compound containing halogenated atoms to continue the reaction, introducing carbon dioxide, reacting the reaction vessel, removing the carbon dioxide, removing small molecule substances, and finally obtaining the cyclic carbonate-terminated polyester.

[0061]

Preparation Example 1

[0062] Under a nitrogen atmosphere and at -20°C, phosphorus oxychloride is slowly added dropwise to a dichloromethane solution containing tetramethylguanidine. After heating and refluxing for 6 hours, the precipitate is filtered off, and the filtrate is evaporated to dryness to obtain catalyst a, tri(tetramethylguanidine)phosphorus oxide, as shown in general formula (1).

[0063]

[0064]

Preparation Example 2

[0065] Under a nitrogen atmosphere and at -20°C, 6 moles of imino-tris(dimethylamino)phosphine were slowly added dropwise to a toluene solution containing 1 mole of phosphorus pentachloride, followed by the slow addition of 2 moles of tetramethylguanidine. The mixture was then heated under reflux for 6 hours, the precipitate was filtered off, and the filtrate was evaporated to dryness to obtain phosphazene salt b as shown in general formula (2). Phosphazene salt b was reacted with an equimolar amount of potassium methoxide to obtain phosphazene salt c.

[0066]

[0067]

Preparation Example 3

[0068] Under a nitrogen atmosphere and at -20°C, 8 moles of tetramethylguanidine were slowly added dropwise to a toluene solution containing 1 mole of phosphorus pentachloride. The mixture was then heated under reflux for 6 hours, the precipitate was filtered off, and the filtrate was evaporated to dryness to obtain phosphazene salt d as shown in general formula (2). Phosphazene salt d was reacted with an equimolar amount of potassium methoxide to obtain phosphazene salt e.

[0069]

[0070]

Preparation Example 4

[0071] Under a nitrogen atmosphere and at -20°C, 8 moles of imino-tris(dimethylamino)phosphine were slowly added dropwise to a toluene solution containing 1 mole of phosphorus pentachloride. The solution was then heated under reflux for 6 hours, the precipitate was filtered off, and the filtrate was evaporated to dryness to obtain phosphazene salt f as shown in general formula (2). Phosphazene salt f was reacted with an equimolar amount of potassium methoxide to obtain phosphazene salt g.

[0072]

[0073] Examples 1-8

[0074] This embodiment illustrates the method for preparing cyclic carbonates from the phosphazene compounds of the present invention, including the following steps:

[0075] (1) Add the catalyst in the amounts shown in Preparation Examples 1 to 4 in Table 1 to a 500 mL stainless steel autoclave.

[0076] (2) Pass the epoxy compound 5M shown in Examples 1 to 8 of Table 1 into a stainless steel autoclave;

[0077] (3) Seal the reactor, purge with carbon dioxide, and maintain the system pressure at approximately 1.0 MPa;

[0078] (4) Heat the reaction gas and slowly raise the temperature using a temperature controller until the final temperature is controlled at 110℃.

[0079] (5) Then control the carbon dioxide pressure at 2.0 MPa;

[0080] (6) After reacting for 10 hours, the mixture was cooled to room temperature, the reactor was removed, and the resulting liquid was distilled under reduced pressure to obtain the product cyclic carbonate.

[0081] The specific epoxy compounds and phosphazene compounds selected as catalysts, as well as the selectivity and yield of the reaction, are shown in Table 1 below:

[0082] Table 1

[0083]

[0084]

Example 9

[0085] 0.86 g of catalyst and 50 g of 700 molecular weight polyether polyol were added to a 500 mL stainless steel autoclave. After nitrogen purging, the mixture was dried under vacuum at 90 °C for 1 h. Then, 180 g of epichlorohydrin was introduced under 0.3 MPa. After the reaction reached negative pressure, 30 g of epichlorohydrin was added and reacted for 3 h. Excess epichlorohydrin was removed. Carbon dioxide was introduced until the pressure reached 2 MPa, and the reaction was carried out at 110 °C for 5 h. Afterward, the carbon dioxide was removed to remove small molecules, yielding a cyclic carbonate-terminated polyether. The cyclic carbonate end-capping rate was 95%.

[0086]

Example 10

[0087] 1.06 g of catalyst a and 50 g of 700 molecular weight polyether polyol were added to a 500 mL stainless steel autoclave. After nitrogen purging, the mixture was dried under vacuum at 90 °C for 1 h. Then, 180 g of epichlorohydrin was introduced under 0.3 MPa. After the reaction reached negative pressure, 30 g of epichlorohydrin was added and reacted for 3 h. Excess epichlorohydrin was removed. Carbon dioxide was introduced until the pressure reached 2 MPa, and the reaction was carried out at 110 °C for 5 h. Afterward, the carbon dioxide was removed to remove small molecules, yielding a cyclic carbonate-terminated polyether. The cyclic carbonate end-capping rate was 92%.

[0088] Comparative Example 1

[0089] 5 g of NaOH and 50 g of 700 molecular weight polyether polyol were added to a 500 mL stainless steel autoclave. After nitrogen purging, the mixture was vacuum dried at 110 °C for 1 h. Then, 180 g of epichlorohydrin was introduced under 0.3 MPa. After the reaction reached negative pressure, 30 g of epichlorohydrin was added and reacted for 3 h. Excess epichlorohydrin was removed. Phosphoric acid was added for neutralization, and magnesium aluminum silicate adsorbent was added for adsorption. The mixture was filtered to obtain epoxy-terminated polyether.

[0090] 200g of the obtained epoxy-terminated polyether was added to a reactor, along with 2g of tetraethylammonium bromide. Carbon dioxide was introduced, and the pressure was increased to 2MPa. The reaction was carried out at 110℃ for 5 hours. Afterward, the carbon dioxide was removed to eliminate small molecules, yielding cyclic carbonate-terminated polyether. The cyclic carbonate end-capping rate was 90%.

Claims

1. The application of phosphazene compounds as catalysts in the reaction of epoxides with carbon dioxide to form cyclic carbonates, wherein the phosphazene compounds have the structure shown in formula (1) or (2): （1）， （2）， in, Ra, Rb, Rc, and Rd are each independently... or ; R1, R2, R3, and R4 are each independently an alkyl group having 1 to 10 carbon atoms, an unsubstituted or substituent phenyl group having 6 to 10 carbon atoms, or an unsubstituted or substituent phenylalkyl group having 6 to 10 carbon atoms; n is an integer from 1 to 8, representing the number of phosphorus cations in the phosphazene compound; Z n- It is an n-valent anion.

2. The application according to claim 1, characterized in that: R1, R2, R3, and R4 are each independently an alkyl group with 1 to 8 carbon atoms, an unsubstituted or substituent phenyl group with 6 to 8 carbon atoms, or an unsubstituted or substituent phenylalkyl group with 6 to 8 carbon atoms; n is an integer from 1 to 3; Z n- The ions are chloride ions, chlorate ions, phosphate ions, hydrogen phosphate ions, methyloxo ions, and ethyloxo ions.

3. The application according to claim 1, characterized in that: The epoxy compound is selected from at least one of ethylene oxide, propylene oxide, 1,2-epoxybutane, phenylene oxide, and cyclohexene oxide.

4. A method for preparing a cyclic carbonate, comprising reacting an epoxy compound with carbon dioxide under the catalysis of a phosphazene compound having the structure shown in formula (1) or (2) to obtain a cyclic carbonate. （1）， （2）， in, Ra, Rb, Rc, and Rd are each independently... or ; R1, R2, R3, and R4 are each independently an alkyl group having 1 to 10 carbon atoms, an unsubstituted or substituent phenyl group having 6 to 10 carbon atoms, or an unsubstituted or substituent phenylalkyl group having 6 to 10 carbon atoms; n is an integer from 1 to 8, representing the number of phosphorus cations in the phosphazene compound; Z n- It is an n-valent anion.

5. The method for preparing the cyclic carbonate according to claim 4, characterized in that: The amount of the phosphazene compound used is 1 × 10⁻⁶ per mole of epoxy compound. -10 ~1×10 -1 Moore.

6. The method for preparing the cyclic carbonate according to claim 5, characterized in that: The amount of the phosphazene compound used is 1 × 10⁻⁶ per mole of epoxy compound. -7 ~1×10 -1 Moore.

7. The method for preparing the cyclic carbonate according to claim 4, characterized in that: The reaction temperature is 10~180℃, the reaction pressure is not higher than 3.0 MPa, and the reaction time is 0.1~50 hours.

8. The method for preparing the cyclic carbonate according to claim 7, characterized in that: The reaction temperature is 30~150℃, the reaction pressure is 0.01~1.5MPa, and the reaction time is 0.1~30 hours.

9. A method for preparing a cyclic carbonate-terminated polyether, comprising the following steps: 1) The initiator is reacted with the epoxy compound under the catalysis of a phosphazene compound having the structure shown in formula (1) or (2); 2) After the reaction in step 1) is complete, an epoxy compound containing halogenated atoms is added to continue the reaction, followed by the introduction of carbon dioxide to carry out the reaction, and finally the cyclic carbonate-terminated polyether is obtained. （1）， （2）， Among them, Ra, Rb, Rc, and Rd are each independently... or ; R1, R2, R3, and R4 are each independently an alkyl group having 1 to 10 carbon atoms, an unsubstituted or substituent phenyl group having 6 to 10 carbon atoms, or an unsubstituted or substituent phenylalkyl group having 6 to 10 carbon atoms; n is an integer from 1 to 8, representing the number of phosphorus cations in the phosphazene compound; Z n- It is an n-valent anion.

10. The method for preparing the cyclic carbonate-terminated polyether according to claim 9, characterized in that: The initiator has active hydrogen; The epoxy compound is at least one of ethylene oxide, propylene oxide, 1,2-epoxybutane, and styrene oxide. The epoxy compound containing halogenated atoms is epichlorohydrin.

11. The method for preparing the cyclic carbonate-terminated polyether according to claim 10, characterized in that: The initiator is an active hydrogen compound containing a hydroxyl group or an active hydrogen compound containing an amino group.

12. The method for preparing the cyclic carbonate-terminated polyether according to claim 11, characterized in that: The active hydrogen compound containing hydroxyl groups is selected from at least one of alcohols having 1 to 20 carbon atoms and polyether polyols having 2 to 8 end groups and 1 to 8 hydroxyl groups on the end groups; the active hydrogen compound containing amine groups is selected from polyamines having 2 to 20 carbon atoms and 2 to 3 primary or secondary amine groups.

13. The method for preparing the cyclic carbonate-terminated polyether according to claim 12, characterized in that: The active hydrogen compound containing hydroxyl groups is selected from polyhydroxy alcohols having 2 to 20 carbon atoms and 2 to 8 hydroxyl groups; the active hydrogen compound containing amine groups is selected from cyclic polyamines having 4 to 10 carbon atoms and 2 to 3 secondary amine groups.

14. The method for preparing the cyclic carbonate-terminated polyether according to claim 9, characterized in that... In step 1): The phosphazene compound is 1-10 wt‰ of cyclic carbonate-terminated polyether; The reaction pressure is less than 0.4 MPa, and the reaction temperature is 70~100℃. o C.

15. The method for preparing the cyclic carbonate-terminated polyether according to claim 9, characterized in that... In step 2): The reaction temperature is 10~180℃, the reaction pressure is not higher than 3.0 MPa, and the reaction time is 0.1~50 hours.

16. The method for preparing the cyclic carbonate-terminated polyether according to claim 15, characterized in that: The reaction temperature is 30~150℃, the reaction pressure is 0.01~1.5MPa, and the reaction time is 0.1~30 hours.

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