Supported catalyst as well as preparation method and application thereof

Abstract

The invention relates to a supported catalyst as well as a preparation method and application thereof, and belongs to the technical field of catalysts. The supported catalyst provided by the invention comprises g-C3N4 and active components supported on the g-C3N4, wherein the active components comprise yttrium trifluoroacetate and diethyl zinc. The N site on the g-C3N4 is utilized to generate strong interaction with yttrium trifluoroacetate and zinc diethyl, so that the dosage of active ingredients is greatly reduced, the safety can be remarkably improved, and the cost of the catalyst can be reduced. By loading the active components on the g-C3N4 carrier, the problem that a homogeneous catalyst is difficult to separate in a reaction system can be avoided, so that residues of the catalyst in the reaction system are reduced to a great extent, the operation process of post-reaction treatment is simplified, and the preparation method has great significance in improving the quality of a polycarbonate product.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology, specifically relating to a supported catalyst, its preparation method, and its application. Background Technology

[0002] As a major greenhouse gas in modern industry, carbon dioxide is urgently needed for resource utilization in the context of achieving carbon neutrality. The preparation of biodegradable polycarbonate by copolymerizing carbon dioxide with epoxy compounds is currently a hot research topic in scientific and industrial fields.

[0003] Currently, the main catalysts used in the ternary copolymerization reaction of carbon dioxide are zinc dicarboxylate catalysts, bimetallic cyanide catalysts, and rare earth ternary catalysts. Among them, rare earth ternary catalysts are simple to prepare and easy to control, allowing for good control over the molecular weight and high ester segment content of polycarbonate. However, the structure of rare earth catalysts is generally trifluoroacetate-diethylzinc-polyol, and they often exist in a homogeneous form in the reaction system, which makes it difficult to separate the reaction products.

[0004] Therefore, it is of great significance to prepare a catalyst that can improve production efficiency and simplify the process. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems existing in the prior art and to provide a supported catalyst, its preparation method, and its application.

[0006] This invention is achieved through the following technical solution: In a first aspect, the present invention provides a supported catalyst comprising g-C3N4 and an active component supported on the g-C3N4, wherein the active component comprises yttrium trifluoroacetate and diethylzinc.

[0007] The supported catalyst of this invention uses graphitic carbon nitride (g-C3N4) as a support, which contains abundant N sites. The strong interaction between the N sites on g-C3N4 and yttrium trifluoroacetate and diethylzinc significantly reduces the amount of active ingredients required, thereby significantly improving safety and reducing catalyst cost. Furthermore, supporting the active ingredients diethylzinc-yttrium trifluoroacetate on the g-C3N4 support avoids the problem of difficult separation of homogeneous catalysts in the reaction system, thus greatly reducing catalyst residue in the reaction system, simplifying the post-reaction processing procedures, and is of great significance for improving the quality of polycarbonate products.

[0008] Preferably, the molar ratio of diethylzinc, yttrium trifluoroacetate and g-C3N4 is (0.02-0.1):1:(10~200).

[0009] Furthermore, the molar ratio of diethylzinc, yttrium trifluoroacetate, and g-C3N4 is (0.02-0.1):1:(20-40).

[0010] Secondly, the present invention provides a method for preparing the supported catalyst, comprising the following steps: in an inert atmosphere, diethylzinc, yttrium trifluoroacetate, and g-C3N4 are stirred and reacted in an organic solvent, and then concentrated to obtain the supported catalyst.

[0011] Preferably, the inert atmosphere includes nitrogen.

[0012] Preferably, the organic solvent comprises tetrahydrofuran.

[0013] Preferably, the molar ratio of diethylzinc, yttrium trifluoroacetate and g-C3N4 is 20:1:(10~200).

[0014] Preferably, the volume ratio of the diethylzinc to the organic solvent is 1:(10-30).

[0015] Preferably, the stirring reaction is carried out at a temperature of 40℃-80℃ for 1h-3h and at a speed of 100rpm-300rpm.

[0016] Preferably, the preparation method of g-C3N4 includes the following steps: calcining the precursor at 400℃-600℃ for 1h-3h to obtain g-C3N4; the precursor includes at least one of urea, dicyandiamide, and melamine.

[0017] More preferably, the precursor is at least one of dicyandiamide and melamine.

[0018] Thirdly, the present invention provides the application of the supported catalyst or the supported catalyst prepared by the method of preparing the supported catalyst in the preparation of polycarbonate.

[0019] Preferably, the polycarbonate is prepared by copolymerizing carbon dioxide and an epoxy compound.

[0020] The supported catalyst of this invention has good catalytic activity for the synthesis of polycarbonate, and at the same time, it can maintain a high molecular weight of polycarbonate while having a high content of ester segments.

[0021] Fourthly, the present invention provides a method for preparing polycarbonate, comprising the following steps: mixing the supported catalyst, cyclohexane oxide, and ethylene oxide in a solvent under an inert atmosphere, then introducing carbon dioxide and stirring to react, thereby obtaining the polycarbonate.

[0022] Preferably, the inert atmosphere includes nitrogen.

[0023] Preferably, the stirring reaction is carried out at a pressure of 4 MPa - 5 MPa, a temperature of 70℃ - 80℃, and a time of 5h - 10h.

[0024] Preferably, the solvent comprises tetrahydrofuran.

[0025] Preferably, the volume ratio of the cyclohexane oxide to the solvent is 1:(1-10).

[0026] Preferably, the molar ratio of cyclohexane oxide, ethylene oxide and diethylzinc in the supported catalyst is (10-500):(10-100):0.01; further, the molar ratio of cyclohexane oxide, ethylene oxide and diethylzinc in the supported catalyst is (150-200):(80-100):0.01.

[0027] The polycarbonate prepared by the method of this invention has a weight-average molecular weight of over 100,000 and an ester segment content of over 90%. The polycarbonate product can be widely used in food packaging and other fields.

[0028] Fifthly, the present invention provides the application of polycarbonate prepared by the method of the present invention in the field of food packaging.

[0029] The present invention has the following beneficial effects: This invention utilizes the strong interaction between the N sites on g-C3N4 and yttrium trifluoroacetate and diethylzinc, significantly reducing the amount of active ingredients required, thereby greatly improving safety and lowering catalyst costs. Furthermore, by loading the active ingredients onto the g-C3N4 support, the problem of difficult separation of homogeneous catalysts in the reaction system is avoided, thus greatly reducing catalyst residue in the reaction system and simplifying post-reaction processing procedures. This is of great significance for improving the quality of polycarbonate products. Detailed Implementation

[0030] To better illustrate the objectives, technical solutions, and advantages of this invention, the invention will be further described below with reference to specific embodiments. Those skilled in the art should understand that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0031] Unless otherwise specified, the experimental methods used in the examples are conventional methods; the materials and reagents used are commercially available unless otherwise specified.

[0032] Example 1 A method for preparing the supported catalyst includes the following steps: (1) Take 5 grams of dicyandiamide and place it in a muffle furnace. Heat the temperature to 500℃ at 2℃ / min and keep it at that temperature for 2 hours to obtain g-C3N4; (2) Under a nitrogen atmosphere, 0.5 mmol of yttrium trifluoroacetate, 0.01 mmol of diethylzinc, 10 mmol of g-C3N4 obtained in step (1) and 30 mL of tetrahydrofuran were added to a reaction vessel with a magnetic stirrer. The mixture was stirred at 300 rpm for 2 hours at 75 °C and then concentrated by distillation to obtain the supported catalyst.

[0033] The supported catalyst of this embodiment is used in the preparation of polycarbonate. The method for preparing polycarbonate includes the following steps: Under a nitrogen atmosphere, the above-prepared supported catalyst, 20 mL of cyclohexane oxide, 4 mL of ethylene oxide, and 20 mL of tetrahydrofuran were added to a high-pressure reactor. Carbon dioxide was introduced to 4 MPa, and the mixture was stirred at 80°C for 8 hours. The catalyst powder was filtered and recovered. Then, 200 mL of methanol was added to the filtrate to precipitate the polymer. The polymer was then dried in a vacuum drying oven at 60°C for 12 hours to obtain a white solid, which is the polycarbonate.

[0034] Example 2 A method for preparing the supported catalyst includes the following steps: (1) Take 5 grams of melamine and place it in a muffle furnace. Heat the temperature to 500°C at 2°C / min and keep it constant for 2 hours to obtain g-C3N4; (2) Under a nitrogen atmosphere, 0.5 mmol of yttrium trifluoroacetate, 0.01 mmol of diethylzinc, 10 mmol of g-C3N4 obtained in step (1) and 30 mL of tetrahydrofuran were added to a reaction vessel with a magnetic stirrer. The mixture was stirred at 300 rpm for 2 hours at 75 °C and then concentrated by distillation to obtain the supported catalyst.

[0035] The supported catalyst of this embodiment is used in the preparation of polycarbonate. The method for preparing polycarbonate includes the following steps: Under a nitrogen atmosphere, the above-prepared supported catalyst, 20 mL of cyclohexane oxide, 4 mL of ethylene oxide, and 20 mL of tetrahydrofuran were added to a high-pressure reactor. Carbon dioxide was introduced to 4 MPa, and the mixture was stirred at 80°C for 8 hours. The catalyst powder was filtered and recovered. Then, 200 mL of methanol was added to the filtrate to precipitate the polymer. The polymer was then dried in a vacuum drying oven at 60°C for 12 hours to obtain a white solid, which is the polycarbonate.

[0036] Example 3 A method for preparing the supported catalyst includes the following steps: (1) Take 20 grams of urea and place it in a muffle furnace. Heat the temperature to 500°C at 2°C / min and keep it constant for 2 hours to obtain g-C3N4; (2) Under a nitrogen atmosphere, 0.5 mmol of yttrium trifluoroacetate, 0.01 mmol of diethylzinc, 10 mmol of g-C3N4 obtained in step (1) and 30 mL of tetrahydrofuran were added to a reaction vessel with a magnetic stirrer. The mixture was stirred at 300 rpm for 2 hours at 75 °C and then concentrated by distillation to obtain the supported catalyst.

[0037] The supported catalyst of this embodiment is used in the preparation of polycarbonate. The method for preparing polycarbonate includes the following steps: Under a nitrogen atmosphere, the above-prepared supported catalyst, 20 mL of cyclohexane oxide, 4 mL of ethylene oxide, and 20 mL of tetrahydrofuran were added to a high-pressure reactor. Carbon dioxide was introduced to 4 MPa, and the mixture was stirred at 80°C for 8 hours. The catalyst powder was filtered and recovered. Then, 200 mL of methanol was added to the filtrate to precipitate the polymer. The polymer was then dried in a vacuum drying oven at 60°C for 12 hours to obtain a white solid, which is the polycarbonate.

[0038] Example 4 A method for preparing the supported catalyst includes the following steps: (1) Take 5 grams of dicyandiamide and place it in a muffle furnace. Heat the temperature to 500℃ at 2℃ / min and keep it at that temperature for 2 hours to obtain g-C3N4; (2) Under a nitrogen atmosphere, 0.3 mmol of yttrium trifluoroacetate, 0.03 mmol of diethylzinc, 10 mmol of g-C3N4 obtained in step (1) and 30 mL of tetrahydrofuran were added to a reaction vessel with a magnetic stirrer. The mixture was stirred at 300 rpm for 2 hours at 75 °C and then concentrated by distillation to obtain the supported catalyst.

[0039] The supported catalyst of this embodiment is used in the preparation of polycarbonate. The method for preparing polycarbonate includes the following steps: Under a nitrogen atmosphere, the above-prepared supported catalyst, 20 mL of cyclohexane oxide, 4 mL of ethylene oxide, and 20 mL of tetrahydrofuran were added to a high-pressure reactor. Carbon dioxide was introduced to 4 MPa, and the mixture was stirred at 80°C for 8 hours. The catalyst powder was filtered and recovered. Then, 200 mL of methanol was added to the filtrate to precipitate the polymer. The polymer was then dried in a vacuum drying oven at 60°C for 12 hours to obtain a white solid, which is the polycarbonate.

[0040] Example 5 A method for preparing the supported catalyst includes the following steps: (1) Take 5 grams of dicyandiamide and place it in a muffle furnace. Heat the temperature to 500℃ at 2℃ / min and keep it at that temperature for 2 hours to obtain g-C3N4; (2) Under a nitrogen atmosphere, 0.5 mmol of yttrium trifluoroacetate, 0.01 mmol of diethylzinc, 10 mmol of g-C3N4 obtained in step (1) and 30 mL of tetrahydrofuran were added to a reaction vessel with a magnetic stirrer. The mixture was stirred at 300 rpm for 2 hours at 75 °C and then concentrated by distillation to obtain the supported catalyst.

[0041] The supported catalyst of this embodiment is used in the preparation of polycarbonate. The method for preparing polycarbonate includes the following steps: Under a nitrogen atmosphere, the above-prepared supported catalyst, 15 mL of cyclohexane oxide, 5 mL of ethylene oxide, and 20 mL of tetrahydrofuran were added to a high-pressure reactor. Carbon dioxide was introduced to 4 MPa, and the mixture was stirred at 80°C for 8 hours. The catalyst powder was filtered and recovered. Then, 200 mL of methanol was added to the filtrate to precipitate the polymer. The polymer was then dried in a vacuum drying oven at 60°C for 12 hours to obtain a white solid, which is the polycarbonate.

[0042] Comparative Example 1 A homogeneous catalyst is composed of 0.5 mmol of yttrium trifluoroacetate and 0.01 mmol of diethylzinc.

[0043] The homogeneous catalyst of this comparative example is used in the preparation of polycarbonate, and the method for preparing the polycarbonate includes the following steps: Under a nitrogen atmosphere, the above homogeneous catalyst, 20 mL of cyclohexane oxide, 4 mL of ethylene oxide, and 20 mL of tetrahydrofuran were added to a high-pressure reactor. Carbon dioxide was introduced to 4 MPa, and the reaction was stirred at 80 °C for 8 hours. Subsequently, the residual catalyst in the reaction system was removed by washing with hydrochloric acid. Then, 200 mL of methanol was added to the filtrate to precipitate the polymer, which was then dried in a vacuum drying oven at 60 °C for 12 hours to obtain a white solid, which is the polycarbonate.

[0044] The test results are shown in Table 1.

[0045] Table 1. Characterization results of polycarbonates prepared in the examples and comparative examples. As can be seen from Table 1, the polycarbonate prepared by the supported catalyst of the present invention has a high weight-average molecular weight and a high content of ester segments, and can significantly reduce the residual amount of metal ions in the system, thereby significantly improving the quality of polycarbonate.

[0046] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A supported catalyst, characterized in that, The supported catalyst comprises g-C3N4 and active components supported on the g-C3N4, wherein the active components include yttrium trifluoroacetate and diethylzinc.

2. The supported catalyst according to claim 1, characterized in that, The molar ratio of diethylzinc, yttrium trifluoroacetate and g-C3N4 is (0.02-0.1):1:(10~200).

3. A method for preparing the supported catalyst according to claim 1 or 2, characterized in that, Includes the following steps: In an inert atmosphere, diethylzinc, yttrium trifluoroacetate, and g-C3N4 are stirred and reacted in an organic solvent, and then concentrated to obtain the supported catalyst.

4. The method for preparing the supported catalyst according to claim 3, characterized in that, The preparation method of the g-C3N4 includes the following steps: calcining the precursor at 400℃-600℃ for 1h-3h to obtain the g-C3N4; the precursor includes at least one of urea, dicyandiamide, and melamine.

5. The method for preparing the supported catalyst according to claim 3, characterized in that, The inert atmosphere includes nitrogen; and / or the organic solvent includes tetrahydrofuran; and / or the molar ratio of diethylzinc, yttrium trifluoroacetate, and g-C3N4 is 20:1:(10~30); and / or the volume ratio of diethylzinc to the organic solvent is 1:(10-30); and / or the stirring reaction is carried out at a temperature of 40℃-80℃ for 1h-3h and a rotation speed of 100rpm-300rpm.

6. The application of the supported catalyst according to claim 1 or 2, or the supported catalyst prepared by any one of claims 3-5, in the preparation of polycarbonate.

7. A method for preparing polycarbonate, characterized in that, Includes the following steps: Under an inert atmosphere, the supported catalyst as described in claim 1 or 2, or the supported catalyst prepared by any one of claims 3-5, cyclohexane oxide, and ethylene oxide are mixed in a solvent, and then carbon dioxide is introduced and the mixture is stirred to react, thereby obtaining the polycarbonate.

8. The method for preparing polycarbonate according to claim 7, characterized in that, The molar ratio of cyclohexane oxide, ethylene oxide and diethylzinc in the supported catalyst is (10-500):(10-100):0.

01.

9. The method for preparing polycarbonate according to claim 7, characterized in that, The inert atmosphere includes nitrogen; and / or the stirring reaction is carried out at a pressure of 4 MPa-5 MPa, a temperature of 70℃-80℃, and a time of 5h-10h; and / or the solvent includes tetrahydrofuran; and / or the volume ratio of cyclohexane oxide to solvent is 1:(1-10).

10. The application of polycarbonate prepared by the method of any one of claims 7-9 in the field of food packaging.

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