A bimetallic complex catalyst and its preparation method and application

Abstract

The present application provides a bimetallic catalyst having a non-toxic metal center and excellent catalytic activity and stability. The carbon dioxide-based polycarbonate prepared by the catalyst has a high molecular weight, a narrow molecular weight distribution, and a high degree of alternating copolymerization of carbon dioxide and alkylene oxide, and has good industrial application prospects.

Description

Technical Field

[0001] The present invention relates to the technical field of metal organic complex homogeneous catalysts, C08G64 / 34, and in particular to a bimetallic complex catalyst and a preparation method and application thereof. Background Art

[0002] With the intensification of global warming, carbon dioxide capture and utilization technologies have become one of the most sought-after high-tech areas. Among these, biodegradable polycarbonates, formed by the alternating copolymerization of carbon dioxide with epoxy compounds, have garnered significant attention. Polypropylene carbonate (PPC), in particular, has been a fully biodegradable plastic and is expected to replace traditional plastics in a wide range of applications, including food packaging, disposable medical materials, and agricultural film.

[0003] At present, in addition to the initial ZnEt2-polyprotic compound catalytic system, the catalysts for the copolymerization of carbon dioxide and epoxy compounds mainly include heterogeneous catalytic systems (such as zinc carboxylates, double metal cyanide, rare earth ternary catalysts, etc.) and homogeneous catalytic systems (such as zinc phenolates, diimine zinc complexes, metal porphyrins, metal Salen complexes, etc.), among which the metal Salen complexes have relatively high catalytic activity, but the technologies currently used are basically heavy metal ions with relatively high toxicity, such as cobalt, zinc, chromium, etc., and the residues of these catalysts will greatly limit the application of polycarbonate, especially in the fields of medical materials and agricultural materials. Therefore, the development of catalysts with non-toxic metals as active centers will significantly expand the application range of polycarbonate; however, the catalysts prepared by these non-toxic metals are not as good as heavy metal elements in catalytic activity and polymerization degree for carbon dioxide and epoxy compounds, and the yield of polycarbonate is also low, which are all problems that need to be solved urgently.

[0004] Chinese patent CN100384909B discloses a polycarbonate material with an alternating structure. The technology discloses the use of a toothed Schiff base metal complex (R1)(R2) SalenMX catalyst. Although the unit content of the carbonate prepared by the catalyst can reach over 99%, the molecular weight distribution of the polycarbonate is greater than 1.24, leaving significant room for improvement. Chinese patent CN101328264B and the Darensbourg team (J.Am.Chem.Soc.2008,130,6523-6533) both report salen catalysts for the copolymerization of epoxy substances and carbon dioxide. Although these catalysts have high catalytic activity and the molecular weight of the polycarbonate prepared is large, the metal catalytic active centers of the catalysts are Cr(III) or Co(III), which are harmful to the environment and human body. The iron-based catalysts currently disclosed have significant disadvantages in catalytic performance compared to the above-mentioned toxic metal catalytic systems. For example, corrole iron complexes (J Am Chem Soc. 2013; 135: 8456–9), but the carbonate content in the PPC produced by them is less than 30%. Other examples include aminotriphenol iron complexes (Green Chem. 2013; 15: 3083–90) and aminobis(phenol) iron (III) complexes (ChemSusChem. 2015; 8: 1034–42), but these can only catalyze the copolymerization reaction of carbon dioxide and cyclohexane oxide.

[0005] Therefore, it is of practical significance to develop a non-toxic, environmentally friendly, stable and highly active catalyst to improve the degree and continuity of copolymerization of carbon dioxide and epoxy compounds, increase the yield of polycarbonate and reduce its molecular weight distribution. Summary of the Invention

[0006] In order to solve the above technical problems, the present invention first provides a bimetallic complex catalyst; the catalyst has the following structure:

[0007]

[0008] Wherein, Q and M are both metal elements, X is a ligand, and R1, R2 and R3 are any one or a combination of H, substituted or unsubstituted alkyl, substituted or unsubstituted alkoxy, polar group, halogen, and cyclic hydrocarbon group.

[0009] Furthermore, the Q is selected from any one of Al, Ti, Fe, Mo, Sn, and Ga; the M is selected from any one of alkali metals or alkaline earth metal elements; and the X includes but is not limited to CH3COO - CF3COO - 、CH(CH3)2COO - 、C(CH3)3COO- 、Cl - 、F - Br - , I - 、BF4 - 、BF6 - 、SO3H - At least one of .

[0010] In the present application, a catalyst is used to initiate the alternating copolymerization of carbon dioxide and alkylene oxide. In this catalyst, a bimetallic catalyst is used as a catalytic active site, and a crown ether-like structure is used to bridge the bimetallic catalyst. The electronic conjugation between the metal center and the crown ether-like ring structure can significantly enhance the stability of the active metal, converting the intermolecular reaction into an intramolecular catalytic reaction, thereby improving the catalytic efficiency. In the structure of the catalyst, the metal Q is selected from any one of Al, Ti, Fe, Mo, Sn, and Ga, and none of the above metals has toxic effects and has no adverse effects on the product of polycarbonate. M is selected from any one of alkali metal elements, magnesium, calcium, and strontium. The nucleophilicity of the Q-propylene carbonate intermediate and the oxyphilicity of M to the coordination of epoxy compounds are utilized to promote the continuous alternating reaction of alkylene oxide and carbon dioxide, improve the selectivity of the reaction, and narrow the molecular weight distribution of the polycarbonate. By selecting a suitable organic ligand X to produce a coordination effect or covalent bond with the metal M, the coordination activation ability of the metal M is regulated to induce the ring opening of the alkylene oxide, thereby further promoting the catalytic activity of the catalyst.

[0011] Furthermore, Q is selected from any one of Al, Ti, Fe, and Mo.

[0012] Furthermore, the M is selected from any one of Li, Na, K, Rb, Cs, Mg, Ca, and Cs.

[0013] Preferably, M is an alkali metal element, selected from any one of Li, Na, K, Rb, and Cs.

[0014] More preferably, the M is selected from any one of Li, Na, and K.

[0015] In a preferred embodiment, Q is Fe or Ti, and M is Na or K. The applicant selected non-toxic metals as activation sites, but compared with heavy metal active sites, their catalytic activity is still not high. The applicant unexpectedly found that when Q is Fe or Ti, M is sodium or potassium, and X is CH3COO - or CF3COO -When the catalyst has the highest catalytic activity for the polymerization reaction, the applicant analyzes the possible reasons as follows: when the active center of the catalyst is Fe-Na, Fe-K, especially Ti-Na, Ti-K, the two metal elements at the Q and M positions maintain a suitable atomic distance in the cavity of the crown ether-like structure, resulting in a suitable catalyst structure. Because when the distance between QM is too large, the conjugated effect between it and the crown ether structure is weakened, and even no metal coordination is produced, resulting in a decrease in the stability of the catalyst. When the copolymerization of carbon dioxide and alkylene oxide is carried out, this catalyst is easily affected by a large amount of proton initiators, and the polymerization reaction rate decreases. When the radius of QM is too small, the structure of the crown ether-like structure no longer maintains an ideal coplanar position, which is detrimental to the π electron system of the catalyst. Only with a suitable QM distance can the ideal crown ether-like structure and conjugated system be maintained. In addition, CH3COO - or CF3COO - It can produce obvious activation effect on Fe and Ti, and it has a certain leaving ability. - or CF3COO - After the ring opening of alkylene oxide is initiated, the intermediate structure of catalyst-ring-opened alkylene oxide is generated, with the help of CH3COO - or CF3COO - The departure of CO and the entry of carbon dioxide enable the copolymerization reaction to proceed continuously, thereby improving the catalytic activity and the yield of polycarbonate.

[0016] Furthermore, the substituted or unsubstituted alkyl group is a substituted or unsubstituted C1-C10 alkyl group; preferably a substituted or unsubstituted C1-C6 alkyl group.

[0017] More preferably, the substituted C1-C6 alkyl group is a C1-C6 alkyl group substituted by halogen, hydroxyl, amino, sulfonate, aldehyde, cyano or carboxyl.

[0018] Furthermore, the substituted or unsubstituted C1-C6 alkyl group includes but is not limited to any one or a combination of methyl, ethyl, propyl, butyl, isopropyl, n-pentyl, isobutyl, tert-butyl, n-hexyl, chloromethyl, dichloromethyl, chloroethyl, dichloroethyl, hydroxymethyl, hydroxypropyl, hydroxyisopropyl, carboxymethyl, carboxyethyl, aminomethyl, aminoethyl, aminopropyl, aminopentyl, cyanomethyl, cyanoethyl, cyanopentyl, and cyanobutyl.

[0019] Furthermore, the substituted or unsubstituted alkoxy group is selected from any one or a combination of oxymethyl, oxyethyl, oxypropyl, oxybutyl, oxypentyl, oxyhexyl, chlorine-substituted methoxy, bromine-substituted methoxy, chlorine-substituted ethoxy, and bromine-substituted ethoxy.

[0020] Furthermore, the polar group includes but is not limited to any one or a combination of carboxyl, hydroxyl, amino, cyano, sulfonic acid, and epoxy groups.

[0021] Furthermore, the cyclic hydrocarbon group includes but is not limited to any one of a benzene ring, a cyclohexyl group, a cyclopentyl group, a cyclopropyl group, and a cyclobutyl group.

[0022] In one embodiment, R1, R2 and R3 are selected from any one or a combination of H, substituted or unsubstituted C1-C6 alkyl, substituted or unsubstituted C1-C6 alkoxy, and halogen.

[0023] The present application unexpectedly discovered that when R1 and R2 in the structure of the specified catalyst are H and R3 is -Br, the polycarbonate catalyzed by the catalyst has a narrower molecular weight distribution. The reason for this is analyzed as follows: -Br ​​acts as an electron-withdrawing group here, which can effectively change the electron cloud distribution density of the conjugated system, thereby achieving the regulation of the departure rate of the -X group in the catalytic reaction intermediate, and the radius of -Br itself gives the catalyst a more suitable steric hindrance, effectively hindering the homopolymerization reaction of alkylene oxide, allowing more alkylene oxide to copolymerize with carbon dioxide, and reducing the molecular weight distribution of the polycarbonate.

[0024] Furthermore, the preparation method of the catalyst comprises the following steps:

[0025] (1) Synthesis of organic ligand: A dimethyl sulfoxide (DMSO) solution containing 2,3-dihydroxybenzaldehyde substituted with R1, R2, and R3 is added dropwise to dimethyl sulfoxide containing an alkaline substance, and triethylene glycol bis(p-toluenesulfonate) is added after stirring, and the mixture is stirred under N2; water and chloroform are added to wash the mixture, and the organic layer is removed, and the aqueous layer is acidified to a pH of 1-2 with HCl, and the product is extracted with chloroform. The organic layer is separated, washed with HCl, and dried with magnesium sulfate, and the solvent is removed to obtain the organic ligand;

[0026] (2) Synthesis of bimetallic catalysts:

[0027] Under N2, [M(OAc)] is added to a solvent containing an organic ligand, mixed and stirred for a certain period of time, and the solvent is removed to obtain a monometallic catalyst;

[0028] Then, perform either step (a) or step (b):

[0029] Step (a): dispersing the substance formed by QX in a solvent, then pouring it into a solvent containing a monometallic catalyst, mixing and stirring under a protective atmosphere, then adding ethylenediamine dropwise thereto and reflux reacting for 2-5 hours, then exposing it to air and stirring overnight, then adding acetic acid and stirring for 36-48 hours, removing the solvent, and filtering the product to obtain the bimetallic catalyst;

[0030] Step (b): dissolving a monometallic catalyst and an alkaline substance in a solvent at low temperature, mixing and reacting for 3-5 hours, adding a certain amount of a halide salt of Q to continue the reaction, filtering, and removing the solvent to obtain a halogen-containing bimetallic catalyst; dissolving the halogen-containing bimetallic catalyst and the metal salt of X in a mixed solution of dichloromethane and acetone, reacting at room temperature in the dark for 10-18 hours, removing the solvent, re-dissolving with dichloromethane, filtering, and then removing the solvent to obtain the bimetallic catalyst.

[0031] Furthermore, the alkaline substance includes but is not limited to NaH or KH.

[0032] Furthermore, in the step (1), the molar ratio of 2,3-dihydroxybenzaldehyde substituted by R1, R2 and R3 to triethylene glycol bis(p-toluenesulfonate) is (2-3):1.

[0033] Furthermore, in step (2), the solvent includes but is not limited to at least one of acetonitrile, tetrahydrofuran (THF), acetone, dimethyl sulfoxide, and dichloromethane.

[0034] Furthermore, in step (2), the molar ratio of the organic ligand to [M(OAc)] is (0.8-1.5):1, preferably 1:1.

[0035] Furthermore, in the step (2), the molar ratio of the substance formed by QX to the single metal catalyst is (1-2):1.

[0036] Furthermore, in step (2), the molar ratio of the single metal catalyst, the halide salt of Q and the metal salt of X is 1:(1-2):(1-3).

[0037] Furthermore, the present application also provides the use of the catalyst in the copolymerization reaction of carbon dioxide and alkylene oxide.

[0038] Furthermore, the copolymerization reaction of carbon dioxide and alkylene oxide is as follows: the catalyst and alkylene oxide are mixed, stirred, heated to a specified temperature, and then pressurized with carbon dioxide to 0.5-4 MPa, reacted for 8-10 hours, and then the solid product is extracted, washed, and dried.

[0039] The carbon dioxide and alkylene oxide in the system rely on the catalysis of the catalyst for polymerization reaction. However, when the pressure in the reaction system is too low, the reaction proceeds slowly, and the carbon dioxide content is relatively small, and the possibility of alkylene oxide forming homopolymers after ring opening increases. When the pressure or temperature is too high, although the polymerization reaction rate is significantly improved, the degree of disorder of the molecules in the system is relatively large, which will also affect the polymerization reaction.

[0040] Furthermore, the alkylene oxide includes but is not limited to at least one of cyclohexene oxide and propylene oxide.

[0041] Furthermore, the mass ratio of the catalyst to the alkylene oxide is 1:300-1200, preferably 1:500-1000.

[0042] Furthermore, the temperature is 25-70°C, preferably 30-60°C.

[0043] Beneficial effects

[0044] 1. Compared with cobalt, chromium, and zinc complex catalysts, the bimetallic catalyst of the present invention is essentially non-toxic and has comparable catalytic activity. The prepared carbon dioxide-based polycarbonate has a high molecular weight, a narrow molecular weight distribution, and a high degree of alternating copolymerization of carbon dioxide and alkylene oxide (the alternation degree reaches 98%).

[0045] 2. This application further optimizes the structure and active center of the catalyst. Compared with traditional homogeneous catalysts, it has excellent catalytic activity without the need to add additional co-catalysts;

[0046] 3. The catalyst of the present application is stable in air, overcoming the defects of current homogeneous catalysts that are easily deteriorated and deactivated and difficult to preserve, and has good industrial application prospects. DETAILED DESCRIPTION

[0047] Example

[0048] Example 1

[0049] This embodiment provides a bimetallic complex catalyst having the following structure:

[0050]

[0051] Wherein M is Na, X is CH3COO - , said R1 and R2 are H, and said R3 is -Br;

[0052] The preparation method of the catalyst comprises the following steps:

[0053] (1) Synthesis of organic ligand: 30 mL of DMSO solution containing 45 mmol of 6-bromo-2,3-dihydroxybenzaldehyde was added dropwise to 10 mL of DMSO (containing 80 mmol of NaH) suspension, and the mixture was stirred at room temperature for 3 h. 25 mmol of triethylene glycol bis(p-toluenesulfonate) was then added, and the mixture was stirred under N2 for 48 h. 400 mL of water was added, and the mixture was washed with 20 mL of chloroform. After removing the organic layer, the aqueous layer was acidified to pH 1 with 6 mol / L HCl, and the product was extracted with chloroform. The organic layer was separated, washed with 1 mol / L HCl, and dried over magnesium sulfate to obtain the organic ligand.

[0054] (2) Synthesis of bimetallic catalysts:

[0055] Under N2, 1.2 mmol of sodium acetate was added to 15 mL of acetonitrile solution containing 1.2 mmol of organic ligand. The mixture was stirred at 25°C for 35 min, and the solvent was removed to obtain a monometallic catalyst.

[0056] 0.6 mmol of ferrous acetate was dispersed in 15 mL of acetonitrile, recorded as solution A; 0.4 mmol of a monometallic catalyst was dissolved in 15 mL of acetonitrile, recorded as solution B; then, solution A and solution B were mixed, stirred at 25°C in a N2 atmosphere for 30 minutes, and then 0.8 mmol of ethylenediamine was added dropwise thereto and refluxed for 4 hours. After that, the mixture was exposed to air and stirred at room temperature overnight, and then 2.2 mmol of acetic acid was added and stirred for 48 hours. After removing the solvent in vacuo, the solid product was dissolved in acetone, filtered using diatomaceous earth, and then the acetone was removed to obtain a bimetallic catalyst.

[0057] This embodiment also provides the use of the bimetallic catalyst in the copolymerization reaction of carbon dioxide and alkylene oxide;

[0058] The carbon dioxide and alkylene oxide copolymerization reaction is as follows: an autoclave is pre-dried in vacuum at 80°C for 24 hours. After cooling to room temperature, the catalyst of Example 1 and cyclohexane oxide are added in a mass ratio of 1:1000 and stirred for 30 minutes. The autoclave is then heated to 60°C, CO2 is introduced, and the pressure is increased to 2 MPa, and the reaction is continued for 10 hours. The carbon dioxide in the autoclave is released, the solid is extracted with dichloromethane, and the precipitate is washed with methanol containing 5 wt% dilute hydrochloric acid (repeated three times). The resulting solid is vacuum dried at 120°C for 24 hours to obtain the white target product.

[0059] Example 2

[0060] This embodiment provides a bimetallic complex catalyst having the following structure:

[0061]

[0062] Wherein M is Na, X is CH3COO - , said R1 and R2 are H, and said R3 is -Br;

[0063] The preparation method of the catalyst comprises the following steps:

[0064] (1) Synthesis of organic ligand: 30 mL of DMSO solution containing 45 mmol of 6-bromo-2,3-dihydroxybenzaldehyde was added dropwise to 10 mL of DMSO (containing 80 mmol of NaH) suspension, and the mixture was stirred at room temperature for 3 h. 25 mmol of triethylene glycol bis(p-toluenesulfonate) was then added, and the mixture was stirred under N2 for 48 h. 400 mL of water was added, and the mixture was washed with 20 mL of chloroform. After removing the organic layer, the aqueous layer was acidified to pH 1 with 6 mol / L HCl, and the product was extracted with chloroform. The organic layer was separated, washed with 1 mol / L HCl, and dried over magnesium sulfate to obtain the organic ligand.

[0065] (2) Synthesis of bimetallic catalysts:

[0066] Under N2, 1.2 mmol of sodium acetate was added to 15 mL of tetrahydrofuran solution containing 1.2 mmol of organic ligand. The mixture was stirred at 25°C for 35 min, and the solvent was removed to obtain a monometallic catalyst.

[0067] Dissolve 1 mmol of the monometallic catalyst in 20 mL of purified THF, cool to 0°C, add 4 equivalents of NaH (60% dispersion in mineral oil), gradually warm to room temperature, and continue the reaction for 4 hours. Remove excess NaH by filtration, cool the filtrate to 0°C, and slowly add 1 equivalent of TiCl₃·(THF)₃. The system is gradually warmed to room temperature and the reaction is continued for 12 hours. Filter off the generated NaCl, and remove the solvent from the filtrate under vacuum to obtain the chlorine-containing bimetallic catalyst (X = Cl). This chlorine-containing bimetallic catalyst is dissolved in a purified dichloromethane / acetone (1:1 volume ratio) mixed solvent, add 2 equivalents of AgOAc, and react at room temperature in the dark for 12 hours. Remove the mixed solvent under reduced pressure, redissolve in purified dichloromethane, and filter to remove the generated AgCl and unreacted AgOAc. Remove the solvent under reduced pressure to obtain the target bimetallic catalyst (X = OAc).

[0068] This embodiment also provides the use of the bimetallic catalyst in the copolymerization reaction of carbon dioxide and alkylene oxide: consistent with Example 1.

[0069] Example 3

[0070] This embodiment provides a bimetallic complex catalyst having the following structure:

[0071]

[0072] Wherein M is K, X is CF3COO - , R1 and R2 are H, and R3 is -Br;

[0073] The preparation method of the catalyst comprises the following steps:

[0074] (1) Synthesis of organic ligand: 30 mL of DMSO solution containing 50 mmol of 6-bromo-2,3-dihydroxybenzaldehyde was added dropwise to 10 mL of DMSO (containing 100 mmol of NaH) suspension, and the mixture was stirred at room temperature for 3 h. 30 mmol of triethylene glycol bis(p-toluenesulfonate) was then added, and the mixture was stirred under N2 for 48 h. 400 mL of water was added, and the mixture was washed with 20 mL of chloroform. After removing the organic layer, the aqueous layer was acidified to pH 1 with 6 mol / L HCl, and the product was extracted with chloroform. The organic layer was separated, washed with 1 mol / L HCl, and dried over magnesium sulfate to obtain the organic ligand.

[0075] (2) Synthesis of bimetallic catalysts:

[0076] Under N2, 1.5 mmol of potassium acetate was added to 15 mL of acetonitrile solution containing 1 mmol of organic ligand. The mixture was stirred at 25°C for 30 min, and the solvent was removed to obtain a monometallic catalyst.

[0077] 0.7 mmol of ferrous acetate was dispersed in 15 mL of acetonitrile, recorded as solution A; 0.5 mmol of a monometallic catalyst was dissolved in 15 mL of acetonitrile, recorded as solution B; then, solution A and solution B were mixed, stirred at 25°C in a N2 atmosphere for 30 minutes, 0.6 mmol of ethylenediamine was added dropwise thereto, and the mixture was refluxed for 5 hours, then exposed to air and stirred at room temperature overnight, and then 2.5 mmol of acetic acid was added and stirred for 48 hours; after removing the solvent in vacuo, the solid product was dissolved in acetone, filtered using diatomaceous earth, and the acetone was removed to obtain a bimetallic catalyst.

[0078] This embodiment also provides the use of the bimetallic catalyst in the copolymerization reaction of carbon dioxide and alkylene oxide;

[0079] The carbon dioxide and alkylene oxide copolymerization reaction is as follows: the autoclave is pre-dried in vacuum at 80°C for 24 hours. After cooling to room temperature, the catalyst of Example 1 and cyclohexane oxide are added in a mass ratio of 1:1200 and stirred for 30 minutes. The autoclave is then heated to 40°C, CO2 is introduced, and the pressure is increased to 4 MPa, and the reaction is continued for 10 hours. The carbon dioxide in the autoclave is released, the solid is extracted with dichloromethane, and the precipitate is washed with methanol containing 5 wt% dilute hydrochloric acid (repeated three times). The resulting solid is vacuum dried at 120°C for 24 hours to obtain the white target product.

[0080] Example 4

[0081] This embodiment provides a bimetallic complex catalyst having the following structure:

[0082]

[0083] Wherein M is Na, X is CH3COO - , R1, R2, and R3 are -H;

[0084] The preparation method of the catalyst comprises the following steps:

[0085] (1) Synthesis of organic ligand: 30 mL of DMSO solution containing 45 mmol of 2,3-dihydroxybenzaldehyde was added dropwise to 10 mL of DMSO (containing 80 mmol of NaH) suspension, and the mixture was stirred at room temperature for 3 h. 25 mmol of triethylene glycol bis(p-toluenesulfonate) was then added, and the mixture was stirred under N2 for 48 h. 400 mL of water was added, and the mixture was washed with 20 mL of chloroform. After removing the organic layer, the aqueous layer was acidified to pH 1 with 6 mol / L HCl, and the product was extracted with chloroform. The organic layer was separated, washed with 1 mol / L HCl, and dried to obtain the organic ligand.

[0086] (2) Synthesis of bimetallic catalysts:

[0087] Under N2, 1.2 mmol of sodium acetate was added to 15 mL of acetone solution containing 1.2 mmol of organic ligand. The mixture was stirred at 25°C for 40 min, and the solvent was removed to obtain a monometallic catalyst.

[0088] 0.6 mmol of ferrous acetate was dissolved in 15 mL of methanol solution, recorded as solution A; 0.4 mmol of a monometallic catalyst was also dissolved in 15 mL of methanol solution, recorded as solution B; then, solution A and solution B were mixed, stirred at 25°C for 30 minutes, 0.8 mmol of ethylenediamine was added dropwise thereto, refluxed for 4 hours, stirred at room temperature overnight, and then 2.2 mmol of acetic acid was added and stirred for 48 hours; after removing the solvent in vacuo, the solid product was dissolved in acetone, filtered using diatomaceous earth, and the acetone was removed to obtain a bimetallic catalyst.

[0089] This embodiment also provides the use of the bimetallic catalyst in the copolymerization reaction of carbon dioxide and alkylene oxide: consistent with Example 1.

[0090] Example 5

[0091] This embodiment provides a bimetallic complex catalyst having the following structure:

[0092]

[0093] Wherein M is Li, X is CH3COO - , R1 and R2 are -H, and R3 is -Br;

[0094] The preparation method of the catalyst comprises the following steps:

[0095] (1) Synthesis of organic ligand: 30 mL of DMSO solution containing 45 mmol of 6-bromo-2,3-dihydroxybenzaldehyde was added dropwise to 10 mL of DMSO (containing 80 mmol of NaH) suspension, and the mixture was stirred at room temperature for 3 h. 25 mmol of triethylene glycol bis(p-toluenesulfonate) was then added, and the mixture was stirred under N2 for 48 h. 400 mL of water was added, and the mixture was washed with 20 mL of chloroform. After removing the organic layer, the aqueous layer was acidified to pH 1 with 6 mol / L HCl, and the product was extracted with chloroform. The organic layer was separated, washed with 1 mol / L HCl, and dried over magnesium sulfate to obtain the organic ligand.

[0096] (2) Synthesis of bimetallic catalysts:

[0097] Under N2, 1.0 mmol of lithium acetate was added to 15 mL of acetone solution containing 1 mmol of organic ligand. The mixture was stirred at 25°C for 30 min, and the solvent was removed to obtain a monometallic catalyst.

[0098] 0.9 mmol of ferrous acetate was dispersed in 15 mL of acetonitrile, recorded as solution A; 1.5 mmol of a monometallic catalyst was dissolved in 15 mL of acetonitrile, recorded as solution B; then, solution A and solution B were mixed, stirred at 25°C in a N2 atmosphere for 30 minutes, 0.8 mmol of ethylenediamine was added dropwise thereto, and the mixture was refluxed for 4 hours, then exposed to air and stirred at room temperature overnight, and then 2.2 mmol of acetic acid was added and stirred for 48 hours; after removing the solvent in vacuo, the solid product was dissolved in acetone, filtered using diatomaceous earth, and then the acetone was removed to obtain a bimetallic catalyst.

[0099] This embodiment provides an application of a bimetallic catalyst in the copolymerization reaction of carbon dioxide and alkylene oxide: consistent with Example 1.

[0100] Example 6

[0101] This embodiment provides an application of a bimetallic catalyst in the copolymerization reaction of carbon dioxide and alkylene oxide;

[0102] The copolymerization reaction of carbon dioxide and alkylene oxide is as follows: an autoclave is pre-dried in vacuum at 80°C for 24 hours. After cooling to room temperature, the catalyst of Example 1 and propylene oxide are added in a mass ratio of 1:1000 and stirred for 30 minutes. The autoclave is then heated to 25°C, CO2 is introduced, and the pressure is increased to 4 MPa, and the reaction is continued for 10 hours. The carbon dioxide in the autoclave is released, the solid is extracted with dichloromethane, and the precipitate is washed with methanol containing 5 wt% dilute hydrochloric acid (repeated three times). The resulting solid is vacuum dried at 120°C for 24 hours to obtain the white target product.

[0103] Comparative Example 1

[0104] The same as Example 1, except that the catalyst has the following structure:

[0105]

[0106] wherein M is Na, X is Cl, R1 and R2 are H, and R3 is -Br;

[0107] In the synthesis of the bimetallic catalyst: ferrous acetate is replaced by ferrous chloride.

[0108] Comparative Example 2

[0109] The same as Example 1, except that the catalyst has the following structure:

[0110]

[0111] Wherein M is Cs, X is CH3COO - , said R1 and R2 are H, and said R3 is -Br;

[0112] In the synthesis of the bimetallic catalyst: lithium acetate is replaced by cesium acetate.

[0113] Comparative Example 3

[0114] The process is basically the same as Example 1, except that the 6-bromo-2,3-dihydroxybenzaldehyde is replaced by 3,5-dichloro-2-hydroxybenzaldehyde.

[0115] Comparative Example 4

[0116] The method is basically the same as Example 1, except that in step (2), the amount of ferrous acetate is 16.0 mmol and the amount of the monometallic catalyst is 0.4 mmol.

[0117] Comparative Example 5

[0118] The process is basically the same as Example 5, except that CO2 is introduced and pressurized to 5 MPa.

[0119] The triethylene glycol bis(p-toluenesulfonate) was purchased from Suzhou Jonathan New Materials Technology Co., Ltd. with a purity of ≥98%; 6-bromo-2,3-dihydroxybenzaldehyde and 3,5-dichloro-2-hydroxybenzaldehyde were purchased from Shanghai Haohong Biotechnology Co., Ltd.; 2,3-dihydroxybenzaldehyde was purchased from Shanghai MacLean Biochemical Technology Co., Ltd.; the cyclohexene oxide and cyclopropane oxide were both purchased from MacLean Reagent; the solvents used in the synthesis steps in the examples were all dehydrated with 3A molecular sieves.

[0120] Performance testing method:

[0121] The catalysts in each example were analyzed and compared in terms of catalytic efficiency (TOF), carbonate unit content, molecular weight (Mn), and molecular weight distribution (PDI) of the prepared polycarbonate. The test results are shown in Table 1.

[0122] Table 1

[0123]

[0124]

Claims

1. A bimetallic complex catalyst, characterized in that: The catalyst has the following structure: The Q is Fe, the M is sodium or potassium, and the X is CH3COO - or CF3COO - ; R1 and R2 are H, and R3 is -Br.

2. A method for preparing the catalyst according to claim 1, characterized in that: The following steps are involved: (1) Synthesis of organic ligand: A dimethyl sulfoxide solution containing 2,3-dihydroxybenzaldehyde substituted with R1, R2, and R3 is added dropwise to dimethyl sulfoxide containing an alkaline substance, and triethylene glycol bis(p-toluenesulfonate) is added after stirring, and the mixture is stirred and mixed under N2; water and chloroform are added to wash the mixture, and the organic layer is removed, and the aqueous layer is acidified to a pH of 1-2 with HCl, and the product is extracted with chloroform. The organic layer is separated, washed with HCl, and dried with magnesium sulfate, and the solvent is removed to obtain the organic ligand; (2) Synthesis of bimetallic catalysts: Under N2, [M(OAc)] is added to a solvent containing an organic ligand, mixed and stirred for a certain period of time, and the solvent is removed to obtain a monometallic catalyst; Then proceed to step (a): Step (a): The substance formed by QX is dispersed in a solvent, which is then poured into a solvent containing a monometallic catalyst. The mixture is mixed and stirred in a protective atmosphere, and ethylenediamine is added dropwise thereto for reflux reaction for 2-5 hours. The mixture is then exposed to air and stirred overnight. Acetic acid is then added and stirred for 36-48 hours. The solvent is removed and the product is filtered to obtain the bimetallic catalyst.

3. Use of the catalyst according to claim 1 in the copolymerization reaction of carbon dioxide and alkylene oxide, characterized in that: The copolymerization reaction is as follows: the catalyst and the alkylene oxide are mixed, stirred and heated to a specified temperature, and then pressurized to 0.5-4 MPa with carbon dioxide and reacted for 8-10 hours; then the solid product is extracted, washed and dried; The alkylene oxide is cyclohexene oxide or propylene oxide.

4. Use of the catalyst according to claim 3 in the copolymerization reaction of carbon dioxide and alkylene oxide, characterized in that The temperature is 25-70°C.

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