A bimetallic schiff base complex, a preparation method thereof and application thereof in catalyzing synthesis of cyclic carbonate

Abstract

The application provides a double metal Schiff base complex, a preparation method thereof and application of the double metal Schiff base complex in catalyzing synthesis of cyclic carbonate. A tetraamine benzene compound containing a substituent group and a salicylaldehyde compound containing a substituent group are dissolved in an organic solvent A, a metal source MZ is added, an organic acid B is added as a catalyst, and the reaction is heated to reflux to obtain the double metal Schiff base complex. The double metal Schiff base complex prepared by the application can weaken the problem of self-polymerization of an active center to a certain extent by adjusting the overall electron cloud density through an X group. The double metal Schiff base complex is used as a catalyst for preparing a cyclic carbonate by reacting carbon dioxide with an epoxide compound, and the catalyst has high activity, good selectivity and is easy to separate from the product; the reaction condition is mild and the process is simple. Moreover, the application can realize one-step production, is simple to prepare and can realize large-scale production.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of cyclic carbonate synthesis, and relates to a double-metal Schiff base complex, a preparation method thereof and application of the double-metal Schiff base complex in catalyzing cyclic carbonate synthesis. BACKGROUND

[0002] Carbon dioxide (CO2) is the main greenhouse gas causing global warming, and the global annual emission amount has reached tens of billions of tons. Recycling, fixing and resource utilization of CO2 have become a problem that the world pays close attention to. From the perspective of resource utilization, CO2 is the most abundant and cheapest carbon resource in the world. Therefore, developing green utilization technology of CO2, developing green and high-fine chemical industry chain, and improving the added value of products have important economic and environmental significance.

[0003] Cyclic carbonate is an important organic synthesis intermediate, has great application value in electrolyte and drug synthesis, and can be synthesized by using greenhouse gas carbon dioxide as a main raw material, so cyclic carbonate is an important chemical product for high-value recycling of carbon dioxide.

[0004] There are five kinds of production processes for ethylene carbonate at present, which are phosgene synthesis method, ester exchange method, halogenated alcohol method, urea alcoholysis method and EO and CO2 ring addition method. The EO and CO2 ring addition method for preparing ethylene carbonate is the most common ethylene carbonate production process at home and abroad, and is a representative example of comprehensive utilization of CO2. The method has the characteristics of wide raw material sources and no by-product generation, and the atomic utilization efficiency can reach 100%. The technology conforms to the new concept of modern chemical industry of low carbon environmental protection, energy saving and emission reduction, realizes the green and effective utilization of greenhouse gas CO2, and develops new characteristic chemical products through a low-cost route, which has very significant economic and social benefits.

[0005] The key to successfully synthesizing EC by one-step method with CO2 and EO as raw materials lies in the activation of CO2 and EO by the catalyst, so the research on the process mainly focuses on developing a suitable catalytic system. The current industrialized EC catalysts (tetraethylammonium bromide, polyethylene glycol-potassium iodide complex and metal complex) generally face core problems such as harsh reaction conditions, poor catalyst activity, high catalyst cost and difficult product separation, and a low-cost, high-efficiency and stable catalyst needs to be developed.

[0006] Metal complex catalysts have controllability, and the structure of ligand, the type and quantity of central metal can be controlled according to different reaction systems, so they have been widely studied by current researchers, are the most widely used CO2 and epoxide ring addition catalysts so far, and can be used alone or in cooperation with a co-catalyst containing a nucleophilic group.

[0007] Although the metal complex catalyst has good catalytic activity in the reaction of catalyzing the cycloaddition of CO2 and alkylene oxide to synthesize cyclic carbonate, it still faces many risks and challenges. The common single metal Schiff base complex is prone to self-polymerization to form oxygen-bridged dimers at the Lewis acid metal center during the reaction, causing deactivation of the active center and affecting the reaction efficiency.

[0008] The double metal Schiff base complex can provide two active centers, can produce a synergistic catalytic effect, and is difficult to self-polymerize to form oxygen-bridged dimers, so that the proportion of deactivation of the active center can be reduced to some extent. The current research on the double metal Schiff base complex, such as the patent with the publication number CN 103102480 A published on May 15, 2013, discloses a double metal catalyst for synthesizing stereoregular polycarbonate, but the synthesis steps are complex and cumbersome, which is not conducive to large-scale industrial production, and the problem of self-polymerization of the active center is not well solved, and a new double metal Schiff base complex that can realize large-scale industrial production is urgently needed.

[0009] Therefore, it is provided that a double metal Schiff base complex with high catalytic activity and capable of realizing large-scale industrial production. SUMMARY

[0010] The purpose of the present application is to provide a double metal Schiff base complex and a preparation method thereof. The four amine benzene compounds connected by X groups are used to connect the double metal centers to form the double metal Schiff base complex. The presence of the X group can affect the electron cloud density of the complex as a whole by donating electrons, and then affect the Lewis acidity of the active center, thereby reducing the problem of self-polymerization of the active center. At the same time, the one-step synthesis process can overcome the problem of complex synthesis process of the double metal Schiff base complex, which is helpful to realize large-scale industrial production.

[0011] The present application also provides the application of the double metal Schiff base complex in the synthesis of cyclic carbonate. The double metal Schiff base complex provided by the present application can efficiently catalyze the synthesis of cyclic carbonate from carbon dioxide and an epoxide under mild conditions. The binary catalytic system mainly consists of a new double metal Schiff base complex catalyst and a cocatalyst. The new double metal Schiff base complex catalyst can reduce the problem of self-polymerization of the active center to some extent, and the one-step synthesis process is helpful to realize large-scale industrial production.

[0012] The specific technical solutions of the present application are as follows:

[0013] A double metal Schiff base complex has the following structure:

[0014]

[0015] M1 and M2 are selected from one of Al 3+ , Zn 2+ , Fe 3+ , Co 3+ , Mn 3+ , Ni 3+ , Mg 2+ , Cr 3+ and Ca 2+ , M1 and M2 are the same or different; preferably Zn 2+ ;

[0016] Z1 and Z2 are selected from one of F - , Cl - , Br - , I - , NO3 - or CH3COO - , Z1 and Z2 are the same or different;

[0017] R1, R2, R3, R4, R5, R6, R7 and R8 are selected from H, CH3, CH2CH3, CH(CH3)2, C(CH3)3, F, Cl, Br, I, NO2, OCH3 or OCH2CH3; R1, R2, R3, R4, R5, R6, R7 and R8 are the same or different;

[0018] X is one of O, N, CH2, CH2CH2, CH2CH2CH2 or Ph.

[0019] The application provides a preparation method of a double metal Schiff base complex, specifically comprising the following steps:

[0020] A tetramine benzene compound containing a substituent group and a salicylaldehyde compound containing a substituent group are dissolved in an organic solvent A, a metal source MZ is added, an organic acid B is added as a catalyst, and the reaction is heated and refluxed, after the reaction is completed and cooled to room temperature, the organic solvent A is removed by vacuum distillation, and dried.

[0021] The heating and refluxing reaction refers to heating and refluxing and stirring reaction at 20-100℃ for 1-24h.

[0022] The organic solvent A can be one of methanol, ethanol, acetonitrile, toluene, dichloromethane, acetone, dimethylformamide, cyclohexane, butanone or diethyl ether.

[0023] The metal source MZ, the cation M can be: Al 3+ , Zn 2+ , Fe 3+ , Co 3+ , Mn 3+ , Ni 3+ , Mg 2+ , Cr3+ and Ca 2+ Metal source anion Z is mainly one or both of F - , Cl - , Br - , I - , NO3 - or CH3COO - In the preparation, the metal source MZ used in the same reaction can be one or both.

[0024] The organic acid B can be one of formic acid, acetic acid, propionic acid, butyric acid, oxalic acid, succinic acid, maleic acid, tartaric acid, benzoic acid or oxalic acid.

[0025] The molar ratio of the substituted tetramine benzene compound, the substituted salicylaldehyde compound and the metal source MZ is 1:4:2, and the molar ratio of the organic acid B and the substituted tetramine benzene compound is 1:50-1:10000.

[0026] The amount of the substituted tetramine benzene compound and the solvent is 0.05-0.5 mol / L;

[0027] The substituted tetramine benzene compound has the following structural formula:

[0028]

[0029] In the structural formula, X is one of O, N, CH2, CH2CH2, CH2CH2CH2 or Ph.

[0030] The substituted salicylaldehyde compound has the following structural formula:

[0031]

[0032] In the structural formula, R1 and R2 are selected from H, CH3, CH2CH3, CH(CH3)2, C(CH3)3, F, Cl, Br, I, NO2, OCH3 or OCH2CH3; R1 and R2 are the same or different.

[0033] In the preparation, the substituted salicylaldehyde compound used in the same reaction can be one or a mixture of multiple.

[0034] Further, the dried product is recrystallized in a hot organic solvent A to obtain an analytically pure Schiff base bimetallic complex.

[0035] The synthesis process of the Schiff base bimetallic complex is mainly as follows:

[0036]

[0037] The application provides application of a double-metal Schiff base complex in catalysis of synthesis of cyclic carbonates, and the double-metal Schiff base complex is used as a catalyst for catalyzing a reaction of carbon dioxide and an epoxide compound to prepare a cyclic carbonate.

[0038] The specific application method is as follows:

[0039] The double-metal Schiff base complex and the cocatalyst are mixed in a reaction kettle, CO2 is used to replace air in the reaction kettle, the epoxide compound is added, CO2 is filled to 1.0-5.0 MPa, and the reaction is carried out under the condition of stirring and temperature rising; the stirring is stopped, the temperature is cooled to room temperature, unreacted CO2 is discharged, and the kettle liquid is separated by distillation under reduced pressure to obtain the product cyclic carbonate.

[0040] The molar ratio of the total molar amount of the double-metal Schiff base complex and the cocatalyst to the molar amount of the epoxide compound is 1:500-1:500000, and the molar ratio of the double-metal Schiff base complex to the cocatalyst is 1:1-1:100, wherein the double-metal Schiff base complex is used as a main catalyst.

[0041] The cocatalyst is one or more of tetramethylammonium chloride, tetramethylammonium bromide, tetramethylammonium iodide, tetraethylammonium chloride, tetraethylammonium bromide, tetraethylammonium iodide, tetrabutylammonium chloride, tetrabutylammonium bromide, tetrabutylammonium iodide or tetrabutylammonium fluoride.

[0042] The temperature rising reaction is a reaction at 120-150 DEG C for 1-8 h.

[0043] The epoxide compound is ethylene oxide or propylene oxide.

[0044] When the epoxide compound is ethylene oxide, the corresponding product is ethylene carbonate.

[0045] When the epoxide compound is propylene oxide, the corresponding product is propylene carbonate.

[0046] The double-metal Schiff base complex is composed of the double-metal center connected by the tetraamine benzene compound connected by the X group, the electron cloud density of the whole complex can be influenced by the electron loss of the X group, and then the Lewis acidity of the active center is influenced, the problem of self-polymerization of the active center is weakened, the problem of complex synthesis process of the double-metal Schiff base complex is overcome by the one-step synthesis process, and large-scale industrial production is facilitated.

[0047] Compared with the prior art, the bimetallic Schiff base complex prepared by the application can weaken the problem of active center self-polymerization to a certain extent by adjusting the overall electron cloud density through the X group. The bimetallic Schiff base complex is used as a catalyst for the reaction of carbon dioxide and an epoxide compound to prepare a cyclic carbonate, and the catalyst has high activity, good selectivity, and is easy to separate from the product; the reaction condition is mild and the process is simple. Moreover, the application can realize one-step production, preparation is simple, and large-scale production can be realized. BRIEF DESCRIPTION OF DRAWINGS

[0048] Figure 1 The 1H NMR spectrum of Example 1. DETAILED DESCRIPTION

[0049] To make the purpose, technical scheme and advantages of the embodiments of the application clearer, the technical scheme of the embodiments of the application will be described clearly and completely below in combination with the embodiments of the application. Obviously, the described embodiments are part of the embodiments of the application, rather than all the embodiments of the application. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the application.

[0050] In the following examples, the test materials and reagents used, etc., can be obtained from commercial channels if not specifically stated.

[0051] If the specific technology or condition is not specified in the examples, the technology or condition described in the literature in the art or according to the product manual can be used.

[0052] Example 1

[0053] A bimetallic Schiff base complex, the structural formula of which is R1-R8 = H, X = Ph, M1 and M2 = Zn, and Z1 and Z2 = CH3COO - The structural formula is as follows:

[0054]

[0055] The preparation method is as follows: [1,1':4',1"-terphenyl]-3,3",5,5"-tetramine (0.1 mol) and salicylaldehyde (0.4 mol) are dissolved in 1L of methanol, then zinc acetate (0.2 mol) is added, a small amount of formic acid (0.001 mol) is added as a catalyst, and the reaction is stirred at 80℃ under reflux for 12h. After the reaction temperature is cooled to room temperature, the methanol is removed by distillation under reduced pressure, and dried to obtain the Schiff base bimetallic complex. The Schiff base bimetallic complex is recrystallized in hot acetonitrile to obtain an analytically pure Schiff base bimetallic complex.

[0056] The application of a double metal Schiff base complex in catalyzing the synthesis of cyclic carbonate is as follows: a Schiff base double metal complex catalyst (0.001 mol) and tetrabutylammonium bromide (0.002 mol) are added into a 1L autoclave with mechanical stirring and temperature control heating device, CO2 is used to replace the air in the reactor three times, 400g of ethylene oxide is added, CO2 is filled to 1.0 MPa, stirring is performed to raise the temperature to 120 DEG C, after 1h of reaction, stirring is stopped, the temperature is cooled to room temperature, the unreacted CO2 is released, the reactor liquid is separated by vacuum distillation to obtain the product, i.e., ethylene carbonate, the yield is 84.2%. GC-MS (HP6890 / 5973) is used for qualitative analysis, and quantitative analysis is completed by GC (GC-112A). The conversion rate of raw material ethylene oxide and the selectivity of product ethylene carbonate are 85% and 99.1% respectively.

[0057] Example 2 (as a comparison)

[0058] A double metal Schiff base complex, the structural formula of which is as follows: R1-R8 = H, M1 and M2 = Zn, Z1 and Z2 = CH3COO - , the structural formula of which is as follows:

[0059]

[0060] The preparation method of the above double metal Schiff base complex is as follows: 3,3',4,4'-diphenyltetramine (0.1 mol) and salicylaldehyde (0.4 mol) are dissolved in 1L of methanol, then zinc acetate (0.2 mol) is added, a small amount of formic acid (0.001 mol) is added as a catalyst, and stirring is performed under heating reflux at 80 DEG C for 12h. After the reaction temperature is cooled to room temperature, methanol is removed by vacuum distillation, and the Schiff base double metal complex is dried and recrystallized in hot acetonitrile to obtain an analytically pure Schiff base double metal complex.

[0061] The application of a double metal Schiff base complex in catalyzing the synthesis of cyclic carbonate is as follows: a Schiff base double metal complex catalyst (0.001 mol) and tetrabutylammonium bromide (0.002 mol) are added into a 1L autoclave with mechanical stirring and temperature control heating device, CO2 is used to replace the air in the reactor three times, 400g of ethylene oxide is added, CO2 is filled to 1.0 MPa, stirring is performed to raise the temperature to 120 DEG C, after 1h of reaction, stirring is stopped, the temperature is cooled to room temperature, the unreacted CO2 is released, the reactor liquid is separated by vacuum distillation to obtain the product, i.e., ethylene carbonate, the yield is 84.2%. GC-MS (HP6890 / 5973) is used for qualitative analysis, and quantitative analysis is completed by GC (GC-112A). The conversion rate of raw material ethylene oxide and the selectivity of product ethylene carbonate are 85% and 99.1% respectively.

[0062] Comparing Example 2 with Example 1, it can be seen that the effect of the main catalyst of Example 1 is better than that of the main catalyst prepared in Example 2, because the introduction of X group in the main catalyst of Example 1 helps to inhibit the self-polymerization of the active center of the catalyst, thereby helping to improve the activity of the catalyst.

[0063] Example 3

[0064] A double metal Schiff base complex, the structural formula of which is R1-R8 = C(CH3)3, X = Ph, M1 and M2 = Zn, Z1 and Z2 = CH3COO - , the structural formula of which is:

[0065]

[0066] The preparation method of the above double metal Schiff base complex is as follows: [1,1':4',1"-terphenyl]-3,3",5,5"-tetramine (0.1 mol) and 3,5-di-tert-butyl salicylaldehyde (0.4 mol) are dissolved in 1 L of methanol, then zinc acetate (0.2 mol) is added, a small amount of formic acid (0.001 mol) is added as a catalyst, and the reaction is stirred under reflux at 80°C for 12 h. After the reaction temperature is cooled to room temperature, the methanol is removed by distillation under reduced pressure, and the Schiff base double metal complex is obtained after drying. The Schiff base double metal complex is recrystallized in hot acetonitrile to obtain an analytically pure Schiff base double metal complex.

[0067] The application of a double metal Schiff base complex in the synthesis of cyclic carbonates, the specific application method being as follows: the Schiff base double metal complex catalyst (0.001 mol) and tetrabutylammonium bromide (0.002 mol) are added to a 1 L autoclave with mechanical stirring and temperature control heating device, the air in the reaction kettle is replaced with CO2 three times, 400 g of ethylene oxide is added, CO2 is filled to 1.0 MPa, the temperature is raised to 120°C under stirring, and after 1 h of reaction, the stirring is stopped, the temperature is cooled to room temperature, the unreacted CO2 is vented, and the kettle liquid is separated by distillation under reduced pressure to obtain the product, i.e. ethylene carbonate, with a yield of 94.4%. Qualitative analysis is performed by GC-MS (HP6890 / 5973), and quantitative analysis is completed by GC (GC-112A). The conversion rate of raw material ethylene oxide and the selectivity of product ethylene carbonate are 95% and 99.4%, respectively.

[0068] Example 4

[0069] A double metal Schiff base complex, the structural formula of which is R1-R8 = Br, X = Ph, M1 and M2 = Zn, Z1 and Z2 = CH3COO - , the structural formula of which is:

[0070]

[0071] The specific preparation method is: [1,1':4',1"-terphenyl]-3,3",5,5"-tetramine (0.1 mol) and 3,5-dibromo salicylaldehyde (0.4 mol) are dissolved in 1L of ethanol, then zinc acetate (0.2 mol) is added, a small amount of formic acid (0.001 mol) is added as a catalyst, and the reaction is stirred at 80°C under reflux for 12h. After cooling to room temperature at the reaction temperature, the ethanol is removed by distillation under reduced pressure, dried, and the Schiff base bimetallic complex is obtained. Recrystallize it in hot acetonitrile to obtain analytically pure Schiff base bimetallic complex.

[0072] The application of a bimetallic Schiff base complex in the synthesis of cyclic carbonates, the specific application method is: the Schiff base bimetallic complex catalyst (0.001 mol) and tetrabutylammonium bromide (0.002 mol) are added to a 1L autoclave with mechanical stirring and temperature control heating device, the air in the reactor is replaced with CO2 three times, 400g of ethylene oxide is added, CO2 is filled to 1.0MPa, the temperature is raised to 120°C under stirring, and the reaction is stopped after 1h. After cooling to room temperature, the unreacted CO2 is released, and the reactor liquid is separated by distillation under reduced pressure to obtain the product, i.e. ethylene carbonate, with a yield of 95.5%. Qualitative analysis is performed by GC-MS (HP6890 / 5973), and quantitative analysis is completed by GC (GC-112A). The conversion rate of raw material ethylene oxide and the selectivity of product ethylene carbonate are 96% and 99.5%, respectively.

[0073] Example 5

[0074] A bimetallic Schiff base complex, the structural formula of which is: R1-R8 = Cl, X = Ph, M1 and M2 = Zn, Z1 and Z2 = CH3COO - , the structural formula of which is:

[0075]

[0076] The specific preparation method is: [1,1':4',1"-terphenyl]-3,3",5,5"-tetramine (0.1 mol) and 3,5-dibromo salicylaldehyde (0.4 mol) are dissolved in 1L of ethanol, then zinc acetate (0.2 mol) is added, a small amount of formic acid (0.001 mol) is added as a catalyst, and the reaction is stirred at 80°C under reflux for 12h. After cooling to room temperature at the reaction temperature, the ethanol is removed by distillation under reduced pressure, dried, and the Schiff base bimetallic complex is obtained. Recrystallize it in hot acetonitrile to obtain analytically pure Schiff base bimetallic complex.

[0077] The application relates to an application of a bimetallic Schiff base complex in catalyzing synthesis of cyclic carbonate, and a specific application method is as follows: a Schiff base bimetallic complex catalyst (0.001 mol) and tetrabutylammonium bromide (0.002 mol) are added into a 1L autoclave with mechanical stirring and temperature control heating devices, CO2 is used to replace air in the autoclave for three times, 400g of ethylene oxide is added, CO2 is filled to 1.0MPa, stirring is carried out to heat to 120 DEG C, after 1h of reaction, the stirring is stopped, cooling is carried out to room temperature, unreacted CO2 is discharged, the autoclave liquid is separated by vacuum distillation to obtain a product, namely, ethylene carbonate, and the yield of the product is 95.2%. Qualitative analysis is carried out by using GC-MS (HP6890 / 5973), and quantitative analysis is completed by using GC (GC-112A). The conversion rate of the raw material ethylene oxide and the selectivity of the product ethylene carbonate are 95.7% and 99.4% respectively.

[0078] Example 6

[0079] A bimetallic Schiff base complex, in the structural formula of which, R1, R3, R5 and R7 are H, R2, R4, R6 and R8 are Br, X=Ph, M1 and M2=Zn, and Z1 and Z2=CH3COO - , the structural formula is as follows:

[0080]

[0081] The specific preparation method is as follows: [1,1':4',1''-terphenyl]-3,3'',5,5''-tetramine (0.1 mol) and 3-bromosalicylaldehyde (0.4 mol) are dissolved in 1L of methanol, then zinc acetate (0.2 mol) is added, a small amount of formic acid (0.001 mol) is added as a catalyst, and the stirring reaction is carried out under heating reflux at 80 DEG C for 12h; after the reaction temperature is cooled to room temperature, methanol is removed by vacuum distillation, and drying is carried out to obtain a Schiff base bimetallic complex, which is recrystallized in hot acetonitrile to obtain an analytically pure Schiff base bimetallic complex.

[0082] The application of a double metal Schiff base complex in catalyzing the synthesis of cyclic carbonate is as follows: a Schiff base double metal complex catalyst (0.001 mol) and tetrabutylammonium bromide (0.002 mol) are added into a 1L autoclave with mechanical stirring and temperature control heating device, CO2 is used to replace the air in the reactor three times, 400g of ethylene oxide is added, CO2 is filled to 1.0 MPa, stirring is performed to heat to 120°C, after 1h of reaction, stirring is stopped, cooling is performed to room temperature, the unreacted CO2 is released, the reactor liquid is separated by vacuum distillation to obtain the product, i.e., ethylene carbonate, the yield is 87.3%. Qualitative analysis is performed by GC-MS (HP6890 / 5973), and quantitative analysis is completed by GC (GC-112A). The conversion rate of the raw material ethylene oxide and the selectivity of the product ethylene carbonate are 88.1% and 99.2% respectively.

[0083] Example 7

[0084] A double metal Schiff base complex, the structural formula of which is R1-R8 = I, X = Ph, M1 and M2 = Zn, Z1 and Z2 = CH3COO - , the structural formula of which is:

[0085]

[0086] The specific preparation method is as follows: [1,1':4',1''-terphenyl]-3,3'',5,5''-tetramine (0.1 mol) and 3,5-diiodosalicylaldehyde (0.4 mol) are dissolved in 1L of methanol, then zinc acetate (0.2 mol) is added, a small amount of formic acid (0.001 mol) is added as a catalyst, and stirring is performed under heating reflux at 80°C for 12h, after the reaction temperature is cooled to room temperature, methanol is removed by vacuum distillation, and drying is performed to obtain a Schiff base double metal complex, which is recrystallized in hot acetonitrile to obtain an analytically pure Schiff base double metal complex.

[0087] The application of a double metal Schiff base complex in catalyzing the synthesis of cyclic carbonate is as follows: a Schiff base double metal complex catalyst (0.001 mol) and tetrabutylammonium bromide (0.002 mol) are added into a 1L autoclave with mechanical stirring and temperature control heating device, CO2 is used to replace the air in the reactor three times, 400g of ethylene oxide is added, CO2 is filled to 1.0 MPa, stirring is performed to heat to 120°C, after 1h of reaction, stirring is stopped, cooling is performed to room temperature, the unreacted CO2 is released, the reactor liquid is separated by vacuum distillation to obtain the product, i.e., ethylene carbonate, the yield is 87.3%. Qualitative analysis is performed by GC-MS (HP6890 / 5973), and quantitative analysis is completed by GC (GC-112A). The conversion rate of the raw material ethylene oxide and the selectivity of the product ethylene carbonate are 88.1% and 99.2% respectively.

[0088] Example 8

[0089] A double metal Schiff base complex, the structural formula of which is R1-R8 = F, X = Ph, M1 and M2 = Zn, Z1 and Z2 = CH3COO - , the structural formula of which is

[0090]

[0091] The specific preparation method is as follows: [1,1':4',1"-terphenyl]-3,3",5,5"-tetramine (0.1 mol) and 3,5-difluorosalicylaldehyde (0.4 mol) are dissolved in 1 L of methanol, then zinc acetate (0.2 mol) is added, a small amount of formic acid (0.001 mol) is added as a catalyst, and the reaction is stirred under reflux at 80°C for 12 h. After the reaction temperature is cooled to room temperature, the methanol is removed by distillation under reduced pressure, and the Schiff base double metal complex is obtained after drying. The Schiff base double metal complex is recrystallized in hot acetonitrile to obtain an analytically pure Schiff base double metal complex.

[0092] The application of a double metal Schiff base complex in the synthesis of cyclic carbonates, the specific application method being as follows: a Schiff base double metal complex catalyst (0.001 mol) and tetrabutylammonium bromide (0.002 mol) are added to a 1 L autoclave with mechanical stirring and temperature control heating device, CO2 is used to replace the air in the reaction kettle three times, 400 g of ethylene oxide is added, CO2 is filled to 1.0 MPa, the temperature is raised to 120°C under stirring, and after 1 h of reaction, the stirring is stopped, the temperature is cooled to room temperature, the unreacted CO2 is vented, and the kettle liquid is separated by distillation under reduced pressure to obtain the product, i.e., ethylene carbonate, with a yield of 93.5%. Qualitative analysis is performed by GC-MS (HP6890 / 5973), and quantitative analysis is completed by GC (GC-112A). The conversion rate of the raw material ethylene oxide and the selectivity of the product ethylene carbonate are 94.2% and 99.3%, respectively.

[0093] Example 9

[0094] A double metal Schiff base complex, the structural formula of which is R1, R3, R5 and R7 are H, R2, R4, R6 and R8 are CH3, X = Ph, M1 and M2 = Zn, Z1 and Z2 = CH3COO - , the structural formula of which is

[0095]

[0096] The specific preparation method is as follows: [1,1':4',1"-terphenyl]-3,3",5,5"-tetramine (0.1 mol) and 3-methyl salicylaldehyde (0.4 mol) are dissolved in 1 L of methanol, then zinc acetate (0.2 mol) is added, a small amount of formic acid (0.001 mol) is added as a catalyst, and the reaction is stirred at 80°C under reflux for 12 h. After cooling to room temperature at the reaction temperature, the methanol is removed by distillation under reduced pressure, dried, and the Schiff base bimetallic complex is obtained. The Schiff base bimetallic complex is recrystallized in hot acetonitrile to obtain an analytically pure Schiff base bimetallic complex.

[0097] The application of a bimetallic Schiff base complex in the synthesis of cyclic carbonates is as follows: a Schiff base bimetallic complex catalyst (0.001 mol) and tetrabutylammonium bromide (0.002 mol) are added to a 1 L autoclave with mechanical stirring and temperature control heating device, the air in the reactor is replaced with CO2 three times, 400 g of ethylene oxide is added, CO2 is filled to 1.0 MPa, the temperature is raised to 120°C under stirring, and the reaction is stopped after 1 h. After cooling to room temperature, the unreacted CO2 is released, and the reactor liquid is separated by distillation under reduced pressure to obtain the product, i.e., ethylene carbonate, with a yield of 89.1%. Qualitative analysis is performed by GC-MS (HP6890 / 5973), and quantitative analysis is completed by GC (GC-112A). The conversion rate of raw material ethylene oxide and the selectivity of product ethylene carbonate are 90% and 99%, respectively.

[0098] Example 10

[0099] A bimetallic Schiff base complex, the structural formula of which is as follows: R1, R3, R5 and R7 are H, R2, R4, R6 and R8 are NO2, X = Ph, M1 and M2 = Zn, and Z1 and Z2 = CH3COO - , the structural formula of which is as follows:

[0100]

[0101] The specific preparation method is as follows: [1,1':4',1"-terphenyl]-3,3",5,5"-tetramine (0.1 mol) and 3-methyl salicylaldehyde (0.4 mol) are dissolved in 1 L of methanol, then zinc acetate (0.2 mol) is added, a small amount of formic acid (0.001 mol) is added as a catalyst, and the reaction is stirred at 80°C under reflux for 12 h. After cooling to room temperature at the reaction temperature, the methanol is removed by distillation under reduced pressure, dried, and the Schiff base bimetallic complex is obtained. The Schiff base bimetallic complex is recrystallized in hot acetonitrile to obtain an analytically pure Schiff base bimetallic complex.

[0102] The application of a double metal Schiff base complex in catalyzing the synthesis of cyclic carbonate is as follows: a Schiff base double metal complex catalyst (0.001 mol) and tetrabutylammonium bromide (0.002 mol) are added into a 1L autoclave with mechanical stirring and temperature control heating device, CO2 is used to replace the air in the reactor three times, 400g of ethylene oxide is added, CO2 is filled to 1.0 MPa, stirring is performed to heat to 120°C, after 1h of reaction, stirring is stopped, cooling is performed to room temperature, the unreacted CO2 is released, the reactor liquid is separated by vacuum distillation to obtain the product, i.e., ethylene carbonate, the yield is 66.6%. GC-MS (HP6890 / 5973) is used for qualitative analysis, and quantitative analysis is completed by GC (GC-112A). The conversion rate of raw material ethylene oxide and the selectivity of product ethylene carbonate are 70% and 95.2% respectively.

[0103] Example 11

[0104] A double metal Schiff base complex, in the structural formula of which, R1-R8 are H, X = Ph, M1 and M2 = Al, Z1 and Z2 = Cl - , the structural formula is as follows:

[0105]

[0106] A preparation method thereof is as follows: [1,1':4',1''-terphenyl]-3,3'',5,5''-tetramine (0.1 mol) and salicylaldehyde (0.4 mol) are dissolved in 1L of methanol, then diethyl aluminum chloride (0.2 mol) is added, a small amount of formic acid (0.001 mol) is added as a catalyst, heating reflux stirring is performed at 80°C for 12h, after the reaction temperature is cooled to room temperature, methanol is removed by vacuum distillation, drying is performed, a Schiff base double metal complex is obtained, and the Schiff base double metal complex is recrystallized in hot acetonitrile to obtain an analytically pure Schiff base double metal complex.

[0107] The application of a double metal Schiff base complex in catalyzing the synthesis of cyclic carbonate is as follows: a Schiff base double metal complex catalyst (0.001 mol) and tetrabutylammonium bromide (0.002 mol) are added into a 1L autoclave with mechanical stirring and temperature control heating device, CO2 is used to replace the air in the reactor three times, 400g of ethylene oxide is added, CO2 is filled to 1.0 MPa, stirring is performed to heat to 120°C, after 1h of reaction, stirring is stopped, cooling is performed to room temperature, the unreacted CO2 is released, the reactor liquid is separated by vacuum distillation to obtain the product, i.e., ethylene carbonate, the yield is 66.6%. GC-MS (HP6890 / 5973) is used for qualitative analysis, and quantitative analysis is completed by GC (GC-112A). The conversion rate of raw material ethylene oxide and the selectivity of product ethylene carbonate are 70% and 95.2% respectively.

[0108] Example 12

[0109] A double metal Schiff base complex, the structural formula of which is: R1-R8 are H, X = Ph, M1 and M2 = Fe, Z1 and Z2 = Cl - , the structural formula of which is:

[0110]

[0111] A method for preparing the same, specifically: [1,1':4',1"-terphenyl]-3,3",5,5"-tetramine (0.1 mol) and salicylaldehyde (0.4 mol) are dissolved in 1 L of methanol, then ferric chloride (0.2 mol) is added, a small amount of formic acid (0.001 mol) is added as a catalyst, and the reaction is stirred at 80°C under reflux for 12 h. After the reaction temperature is cooled to room temperature, the methanol is removed by distillation under reduced pressure, and the Schiff base double metal complex is obtained after drying. The Schiff base double metal complex is recrystallized in hot acetonitrile to obtain an analytically pure Schiff base double metal complex.

[0112] Application of a double metal Schiff base complex in catalyzing the synthesis of cyclic carbonates, specifically: Schiff base double metal complex catalyst (0.001 mol) and tetrabutylammonium bromide (0.002 mol) are added to a 1 L autoclave with mechanical stirring and temperature control heating device, the autoclave is replaced with CO2 three times, 400 g of ethylene oxide is added, CO2 is filled to 1.0 MPa, the temperature is raised to 120°C under stirring, the reaction is stopped after 1 h, the unreacted CO2 is released after cooling to room temperature, and the product is obtained by distillation under reduced pressure. The product is ethylene carbonate, the yield is 42.5%. Qualitative analysis is performed by GC-MS (HP6890 / 5973), and quantitative analysis is completed by GC (GC-112A). The conversion rate of raw material ethylene oxide and the selectivity of product ethylene carbonate are 50.1% and 85.3%, respectively.

[0113] The above examples are described to facilitate the understanding and use of the invention by those skilled in the art. Those skilled in the art can easily make various modifications to these examples, and apply the general principles described herein to other examples without having to undergo creative labor. Therefore, the present invention is not limited to the above examples, and improvements and modifications made by those skilled in the art without departing from the scope of the invention should be within the scope of protection of the present invention.

Claims

1. A bimetallic Schiff base complex, characterized in that, The structure of the bimetallic Schiff base complex is as follows: ； In the structural formula, M1 and M2 are selected from Al. 3+ Zn 2+ Fe 3+ One of them, M1 and M2 are the same; Z1 and Z2 are selected from F - Cl - ,Br - I - NO3 - or CH3COO - One of them, Z1 and Z2 are the same; R1, R2, R3, R4, R5, R6, R7, and R8 are selected from one of H, CH3, CH2CH3, CH(CH3)2, C(CH3)3, F, Cl, Br, I, NO2, OCH3, or OCH2CH3; R1, R3, R5, and R7 are the same; R2, R4, R6, and R8 are the same; R1 and R2 may be the same or different. X stands for Ph.

2. A method for preparing the bimetallic Schiff base complex according to claim 1, characterized in that, The preparation method is as follows: a tetraaminebenzene compound containing a substituted group and a salicylaldehyde compound containing a substituted group are dissolved in an organic solvent A, a metal source MZ is added, and an organic acid B is added as a catalyst. The mixture is heated under reflux and reacted. After the reaction is completed and cooled to room temperature, the organic solvent A is removed by vacuum distillation and the mixture is dried. The tetraaminebenzene compound containing substituted groups has the following structural formula: ， In the structural formula, X represents Ph; The salicylaldehyde compound containing substituted groups has the following structural formula: ； In the structural formula, R1 and R2 are selected from H, CH3, CH2CH3, CH(CH3)2, C(CH3)3, F, Cl, Br, I, NO2, OCH3 or OCH2CH3; R1 and R2 may be the same or different; The metal source MZ, and the cation M are selected from: Al 3+ Zn 2+ or Fe 3+ The metal source anion Z is selected from F. - Cl - ,Br - I - NO3 - or CH3COO - ; The organic acid B is selected from one of the following: formic acid, acetic acid, propionic acid, butyric acid, oxalic acid, succinic acid, maleic acid, tartaric acid, benzoic acid, or oxalic acid. The organic solvent A is selected from one of the following: methanol, ethanol, acetonitrile, toluene, dichloromethane, acetone, dimethylformamide, cyclohexane, butanone, or diethyl ether.

3. The preparation method according to claim 2, characterized in that, The heating and reflux reaction refers to a heating and reflux reaction with stirring at 20-100℃ for 1-24 hours.

4. The preparation method according to claim 2, characterized in that, The molar ratio of the tetraaminebenzene compound containing substituent groups, the salicylaldehyde compound containing substituent groups, and the metal source MZ is 1:4:2, and the molar ratio of the organic acid B and the tetraaminebenzene compound containing substituent groups is 1:50-1:10000.

5. The application of the bimetallic Schiff base complex of claim 1 in the catalytic synthesis of cyclic carbonates, characterized in that, The bimetallic Schiff base complex is used as a catalyst to catalyze the reaction of carbon dioxide with epoxides to prepare cyclic carbonates.

6. The application according to claim 5, characterized in that, The application method is as follows: A bimetallic Schiff base complex and a co-catalyst are mixed in a reactor. After replacing the air in the reactor with CO2, an epoxide is added, and CO2 is introduced to a pressure of 1.0-5.0 MPa. Under stirring, the temperature is increased to allow the reaction to proceed. Stirring is then stopped, and the mixture is cooled to room temperature. Unreacted CO2 is released, and the reactor liquid is separated by vacuum distillation to obtain the product, cyclic carbonate. The total molar ratio of the bimetallic Schiff base complex and co-catalyst to the epoxide is 1:500-1:500000, and the molar ratio of the bimetallic Schiff base complex to the co-catalyst is 1:1-1:

100. The bimetallic Schiff base complex serves as the main catalyst. The co-catalyst is selected from one or more of tetramethylammonium chloride, tetramethylammonium bromide, tetramethylammonium iodide, tetraethylammonium chloride, tetraethylammonium bromide, tetraethylammonium iodide, tetrabutylammonium chloride, tetrabutylammonium bromide, tetrabutylammonium iodide, or tetrabutylammonium fluoride.

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