Salen-Co (III)-X immobilized catalyst as well as preparation method and application thereof

Abstract

The invention relates to the technical field of catalyst materials, in particular to a Salen-Co (III)-X immobilized catalyst as well as a preparation method and application thereof, and the preparation method comprises the following steps: S1, preparing a Salen ligand; and S2, mixing a solvent, the Salen ligand obtained in the step S1 and a mesoporous molecular sieve, carrying out a reaction in a protective atmosphere, then adding a solution containing a Co compound, continuing the reaction, drying the reactant, and oxidizing the dried reactant to obtain the mesoporous molecular sieve packaged Salen-Co (III)-X catalyst, and S3, grafting a cocatalyst to the Salen-Co (III)-X catalyst packaged by the mesoporous molecular sieve obtained in S2 through a silanol bond. According to the invention, a mesoporous molecular sieve is adopted to package a Salen metal catalyst, and a silanol bond is utilized to graft a cocatalyst, so that the immobilized bifunctional catalyst is synthesized. The immobilized bifunctional catalyst is high in activity, convenient to separate from a product and easy to form, the formed catalyst is convenient to use in a continuous flow reactor, and the operation simplicity and economic benefits of the process are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of catalyst materials, and in particular to a Salen-Co(III)-X solid-supported catalyst and a preparation method and application thereof. Background Art

[0002] Polypropylene carbonate is CO 2 With propylene oxide (PO) or CO 2 A class of high molecular compounds polymerized by PO, acid anhydride, etc. under the action of catalysts. The polymer is a non-toxic, odorless, transparent or white solid with excellent barrier properties. It has good biocompatibility and is completely degradable. It can replace traditional petroleum-based non-degradable plastics and solve the environmental pollution caused by "white garbage".

[0003] Since 1969, Japanese scientist Inoue discovered CO 2 Since the copolymerization with PO to synthesize PPC, heterogeneous catalysts such as diethylzinc and zinc carboxylates have been widely studied. Due to the poor reaction activity and large dosage of heterogeneous catalysts, they have been replaced by homogeneous catalysts; among homogeneous catalysts, metal porphyrins, β-diimine zinc, and Salen metal complexes have been widely studied. Among them, Salen metal catalysts are favored by researchers because of their high reaction activity, stereoselectivity, inhibition of the formation of side reaction cyclic carbonates, and high carbonate chain content. Among Salen metal catalysts, Salen-Co(III)-X catalysts are highly valued by researchers due to the unique electronic structure and magnetizable properties of Co.

[0004] However, the current homogeneous catalyst Salen-Co(III)-X catalyzes PO, CO 2 In the process of synthesizing polypropylene carbonate (PPC) by terpolymerization of polypropylene carbonate with polyol, anhydride or glycidyl ether, there is a dilemma that the catalyst and the product are difficult to separate, and it can only be used in an intermittent reactor but not a continuous flow reactor. Summary of the invention

[0005] In order to solve the defects in the prior art, the present invention provides a Salen-Co(III)-X solid-supported catalyst and a preparation method and application thereof. The present invention uses a mesoporous molecular sieve to encapsulate a Salen metal catalyst and uses a silanol bond to graft a co-catalyst to synthesize a solid-supported bifunctional catalyst. The solid-supported bifunctional catalyst is convenient for separating the catalyst from the product and is easy to shape. The formed catalyst is convenient for use in a continuous flow reactor, thereby improving the simplicity and economic benefits of the process operation.

[0006] To achieve the above object, the present invention adopts the following technical solutions: In a first aspect, the present invention provides a method for preparing a Salen-Co(III)-X immobilized catalyst, comprising the following steps: S1. Preparation of Salen ligand; S2, firstly mixing the solvent, the Salen ligand obtained in S1 and the mesoporous molecular sieve, reacting under a protective atmosphere, then adding a solution containing a Co compound to continue the reaction, drying and then oxidizing the reactants to obtain a mesoporous molecular sieve encapsulated Salen-Co(III)-X catalyst; S3, grafting the co-catalyst onto the mesoporous molecular sieve encapsulated Salen-Co(III)-X catalyst obtained in S2 via silanol bonds.

[0007] In some embodiments of the present invention, the preparation process of the Salen ligand is: firstly, a solvent and a diamine are mixed, dissolved under a protective atmosphere, and then a salicylaldehyde solution is added and reacted under a protective atmosphere to obtain the Salen ligand.

[0008] Preferably, the diamine is selected from any one of ethylenediamine, cyclohexylenediamine and o-phenylenediamine.

[0009] Preferably, the salicylaldehyde is selected from any one of salicylaldehyde and 3-tert-butyl salicylaldehyde.

[0010] Preferably, the molar ratio of the diamine to salicylaldehyde is 1:2.

[0011] Preferably, the mesoporous molecular sieve is selected from any one of MCM-22 and MCM-41.

[0012] Preferably, the Co compound is selected from any one of anhydrous cobalt acetate and anhydrous cobalt nitrate.

[0013] Preferably, in S2, the mass ratio of the amount of the Salen ligand obtained in S1 to the mesoporous molecular sieve is 1-10 mmol / g.

[0014] Preferably, in S2, the molar ratio of the Salen ligand obtained in S1 to the Co compound is 1:(1-2).

[0015] Preferably, in S2, the temperature for the mixed reaction of the solvent, the Salen ligand obtained in S1 and the mesoporous molecular sieve is 80° C. and the time is 16 h.

[0016] Preferably, in S2, the solution containing the Co compound is added within 10 min and the reaction is continued, and the reaction time is 16 h.

[0017] Preferably, the oxidation step in S2 is specifically as follows: after drying the reactant, adding dichloromethane and an ethanol solution of LiCl, introducing oxygen, stirring and reacting at room temperature in the dark, and separating and drying the solid after the reaction is completed.

[0018] Preferably, the silanol bond in S3 is from any one of γ-chloropropyltrimethoxysilane, 11-chloroundecyltrimethoxysilane, 4-bromobutyltrimethoxysilane, 6-bromohexyltrimethoxysilane and 11-bromoundecyltrimethoxysilane.

[0019] Preferably, the co-catalyst is a tertiary amine satisfying the general formula [CH 3 (CH 2 )n] 3 N, n=1 to 6. More preferably, n=1, which is triethylamine.

[0020] Preferably, S3 is specifically: mixing the mesoporous molecular sieve encapsulated Salen-Co(III)-X catalyst obtained in S2 with the silanol bond raw material, adding a solvent for reaction, adding a co-catalyst after the reaction is completed, continuing the reaction, and drying the obtained reactant.

[0021] Preferably, the molar ratio of Co and silanol bond raw material in the mesoporous molecule encapsulated Salen-Co(III)-X catalyst obtained in S2 is (1-2):1.

[0022] Preferably, the molar ratio of the co-catalyst to the silanol bond raw material is (1-1.5):1.

[0023] In a second aspect, the present invention provides a Salen-Co(III)-X solid-supported catalyst prepared by the above method.

[0024] In a third aspect, the present invention provides use of the Salen-Co(III)-X supported catalyst in the preparation of polypropylene carbonate.

[0025] The beneficial effects of the present invention are: The present invention first uses a mesoporous molecular sieve to encapsulate a Salen metal catalyst, and then uses a silanol bond to graft a co-catalyst to synthesize a solid-supported bifunctional catalyst. The solid-supported bifunctional catalyst has high catalytic activity, is easy to separate the catalyst from the product, and is easy to shape. The formed catalyst is convenient to use in a continuous flow reactor, thereby improving the simplicity and economic benefits of the process operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Salen-Co(III)-NO encapsulated in MCM-22 of Example 4 3 Surface morphology of the catalyst.

[0027] Figure 2 The MCM-22 encapsulated Salen-Co(III)-NO in Example 4 3 Surface morphology of the catalyst after grafting the co-catalyst. DETAILED DESCRIPTION

[0028] In order to enable those skilled in the art to better understand the technical solution of the invention, the present invention is further described in detail below in conjunction with specific implementation methods.

[0029] Example 1 This embodiment provides a method for preparing a Salen-Co(III)-X immobilized catalyst, comprising the following steps: (1) Preparation of Salen ligand In a 500 mL three-necked round-bottom flask equipped with a condenser, add 200 mL of anhydrous ethanol and then 0.02 mol of ethylenediamine; transfer 100 mL of anhydrous ethanol solution containing 0.04 mol of 3-tert-butyl salicylaldehyde to a constant pressure dropping funnel and place it on the other neck of the round-bottom flask. Pass N 2 After replacing the air in the round-bottom flask, 2 Under the protection of N, the mixture was heated under magnetic stirring and refluxed until the ethylenediamine was completely dissolved. The constant pressure dropping funnel was opened and the ethanol solution of 3-tert-butyl salicylaldehyde was added dropwise within 10 minutes. 2 The mixture was heated to reflux for 12 hours under magnetic stirring under protection. After the reaction was completed, the heating was stopped, the stirring was continued, and the mixture was cooled to room temperature. The reaction solution was transferred to a large beaker, allowed to stand, filtered, and washed with anhydrous ethanol for 3 times. The mixture was vacuum dried at 60°C to constant weight to synthesize the Salen ligand for later use.

[0030] (2) MCM-22 encapsulated Salen-Co(III)-X catalyst In a 500 mL three-necked round-bottom flask, 300 mL of tert-butyl alcohol was added, followed by 0.01 mol of Salen ligand and 5 g of MCM-22 solid powder (the mass ratio of Salen ligand to MCM-22 was 2 mmol / g); 0.02 mol of anhydrous cobalt acetate was dissolved in 100 mL of tert-butyl alcohol, transferred to a constant pressure dropping funnel, and installed on the three-necked flask. N 2 After replacing the air in the round-bottom flask, 2Under protection, magnetic stirring was carried out, and the reaction was heated under reflux at 80 °C for 16 hours; then the constant pressure dropping funnel was opened, and the anhydrous cobalt acetate solution was added dropwise, and the dropping was completed within 10 minutes, and the reflux reaction was carried out for 16 hours. After encapsulation, the heating was stopped, cooled to room temperature, filtered by suction, and the obtained solid was transferred to a Soxhlet extractor and extracted with tert-butanol, acetonitrile, and petroleum ether for 12 hours respectively to remove the unreacted Salen ligand and anhydrous cobalt acetate. After extraction, the obtained solid was dried in a vacuum oven at 100 °C for 6 hours.

[0031] The above solid was transferred to a 500 mL round-bottomed flask containing 200 mL of dichloromethane, and an ethanol solution of 0.01 mol LiCl was added. Oxygen was introduced, and magnetic stirring was carried out in the dark at room temperature for 8 hours. After the reaction was completed, the solid was separated, and the residual solvent in the solid was removed by distillation under reduced pressure. Under the condition of 60 °C, it was dried in vacuo to constant weight to obtain the MCM-22 encapsulated Salen-Co(III)-OAC catalyst.

[0032] (3)Grafting of cocatalyst on MCM-22 The MCM-22 encapsulated Salen-Co(III)-OAC catalyst was mixed with γ-chloropropyltrimethoxysilane (the molar ratio of Co to γ-chloropropyltrimethoxysilane in the catalyst was 2:1), using dioxane as the solvent, and stirred at 40 °C for 24 hours. After the reaction was completed, a slight excess of triethylamine was added (the molar ratio of triethylamine to γ-chloropropyltrimethoxysilane was 1.1:1), and the reaction was continued at 80 °C for 12 hours. The solid was separated, and the solvent was removed by freeze-drying the solid to obtain the required supported catalyst, denoted as MCM-22@Salen(ethyl)-Co(III)-OAC.

[0033] Example 2 The preparation method was the same as that of Example 1, except that in the preparation process of the (1) Salen ligand, ethylenediamine was replaced by cyclohexanediamine.

[0034] The obtained supported catalyst was denoted as MCM-22@Salen(cyclo)-Co(III)-OAC.

[0035] Example 3 The preparation method was the same as that of Example 1, except that in the preparation process of the (1) Salen ligand, ethylenediamine was replaced by o-phenylenediamine.

[0036] The obtained supported catalyst was denoted as MCM-22@Salen(phenyl)-Co(III)-OAC.

[0037] Example 4 The preparation method is the same as that of Example 1, except that, in the process of (2) encapsulating the Salen-Co(III)-X catalyst in MCM-22, anhydrous cobalt acetate is replaced by anhydrous cobalt nitrate.

[0038] The obtained immobilized catalyst was named MCM-22@Salen(II)-Co(III)-NO 3 .

[0039] Example 5 The preparation method is the same as that of Example 2, except that, in the process of (2) encapsulating the Salen-Co(III)-X catalyst in MCM-22, anhydrous cobalt acetate is replaced by anhydrous cobalt nitrate.

[0040] The obtained immobilized catalyst was named MCM-22@Salen(cyclo)-Co(III)-NO 3 .

[0041] Example 6 The preparation method is the same as that of Example 3, except that, in the process of (2) encapsulating the Salen-Co(III)-X catalyst in MCM-22, anhydrous cobalt acetate is replaced by anhydrous cobalt nitrate.

[0042] The obtained immobilized catalyst was named MCM-22@Salen(benzene)-Co(III)-NO 3 .

[0043] Example 7 The preparation method is the same as that of Example 1, except that in step (2), the mass ratio of the amount of the Salen ligand to MCM-22 is 1 mmol / g, and the mass ratio of anhydrous cobalt acetate to the Salen ligand is 1:1.

[0044] Example 8 The preparation method is the same as that of Example 1, except that in step (2), the mass ratio of the amount of the Salen ligand to MCM-22 is 10 mmol / g, and the mass ratio of anhydrous cobalt acetate to the Salen ligand is 1:1.

[0045] Example 9 The preparation method is the same as that of Example 1, except that in step (3), the molar ratio of Co to γ-chloropropyltrimethoxysilane in the catalyst is 1:1, and the molar ratio of triethylamine to γ-chloropropyltrimethoxysilane is 1:1.

[0046] Example 10 The preparation method is the same as that of Example 1, except that in step (3), the molar ratio of Co to γ-chloropropyltrimethoxysilane in the catalyst is 1:1, and the molar ratio of triethylamine to γ-chloropropyltrimethoxysilane is 1.5:1.

[0047] Comparative Example 1 The preparation method is the same as in Example 1, except that: In step (2), 5 g of MCM-22 solid powder is not added, and the amount of anhydrous cobalt acetate used is 0.01 mol; There is no step (3) of grafting the co-catalyst onto MCM-22.

[0048] The obtained catalyst was named Salen(II)-Co(III)-OAC.

[0049] Comparative Example 2 The preparation method is the same as in Example 2, except that: In step (2), 5 g of MCM-22 solid powder is not added, and the amount of anhydrous cobalt acetate used is 0.01 mol; There is no step (3) of grafting the co-catalyst onto MCM-22.

[0050] The obtained catalyst was named Salen(cyclo)-Co(III)-OAC.

[0051] Comparative Example 3 The preparation method is the same as that of Example 3, except that: In step (2), 5 g of MCM-22 solid powder is not added, and the amount of anhydrous cobalt acetate used is 0.01 mol; There is no step (3) of grafting the co-catalyst onto MCM-22.

[0052] The obtained catalyst was recorded as Salen(benzene)-Co(III)-OAC.

[0053] Comparative Example 4 The preparation method is the same as that of Example 4, except that: In step (2), 5 g of MCM-22 solid powder is not added, and the amount of anhydrous cobalt nitrate used is 0.01 mol; There is no step (3) of grafting the co-catalyst onto MCM-22.

[0054] The obtained catalyst was named Salen(II)-Co(III)-NO 3 .

[0055] Comparative Example 5 The preparation method is the same as that of Example 5, except that: In step (2), 5 g of MCM-22 solid powder is not added, and the amount of anhydrous cobalt nitrate used is 0.01 mol; There is no step (3) of grafting the co-catalyst onto MCM-22.

[0056] The obtained catalyst is recorded as Salen(ring)-Co(III)-NO 3 .

[0057] Comparative Example 6 The preparation method is the same as that of Example 6, except that: In step (2), 5 g of MCM-22 solid powder is not added, and the amount of anhydrous cobalt nitrate used is 0.01 mol; There is no step (3) of grafting the co-catalyst onto MCM-22.

[0058] The obtained catalyst is recorded as Salen(benzene)-Co(III)-NO 3 .

[0059] Effect Example 1 Morphology Characterization of Catalyst Figure 1 The MCM-22 encapsulated Salen-Co(III)-NO obtained in step (2) of Example 4 3 Surface morphology of the catalyst. Figure 2 This is the surface morphology of the grafted catalyst obtained in step (3) of this embodiment. Figure 1 and Figure 2 It can be seen that there is no Salen-Co(III)-NO on the outer surface of the molecular sieve. 3 The presence of Salen-Co(III)-NO 3 It is effectively encapsulated in the pores of the MCM-22 molecular sieve. This encapsulation effect gives the catalyst a structural feature similar to "zeolite enzyme", which can effectively improve the activity and stability of the catalyst. The bifunctional catalyst after grafting the cocatalyst further improves the activity and stability of the catalyst due to the synergistic effect of the cocatalyst and the main catalyst. At the same time, the bifunctional catalyst grafted with the cocatalyst realizes the dual loading of the main catalyst and the cocatalyst (the main catalyst is encapsulated in the pores of the molecular sieve, and the cocatalyst is grafted on the outer surface of the catalyst), which further improves the simplicity and separation degree of the catalyst and the synthetic product, and improves the performance of the catalyst in the continuous flow reactor.

[0060] Effect Example 2 Catalyst Activity Detection (1) Catalytic CO 2 , PO, phthalic anhydride terpolymer Catalytic process: The catalyst prepared in the examples and comparative examples was mixed with pretreated PO and phthalic anhydride (n 催化剂 :n PO :n 邻苯二甲酸酐 =5000:1:1) was added into a 500 mL vacuum dried autoclave and heated with CO at room temperature. 2 Replace the air in the autoclave 2-3 times. Then, fill it with 3 MPa of CO 2 gas, set the reaction temperature to 25℃ and the reaction time to 40 h. After the reaction, cool to room temperature, release the pressure to normal pressure, open the autoclave, filter and separate the solid catalyst, dissolve the crude product with dichloromethane, remove the unreacted reactants and residual dichloromethane solvent by vacuum distillation, weigh and record. The catalytic performance of the catalyst is shown in Table 1.

[0061] Table 1

[0062] (2) Catalytic CO 2 , PO, maleic anhydride terpolymer The catalytic process and data analysis were the same as (1). The results are shown in Table 2.

[0063] Table 2

[0064] It can be seen from Table 1 and Table 2 that the present invention uses mesoporous molecular sieves to first encapsulate the Salen metal catalyst and then uses silanol bonds to graft the catalyst to obtain a solid catalyst, which greatly improves the propylene oxide conversion rate, modified polymer selectivity and conversion frequency TOF value.

[0065] Effect Example 3 Application of Catalyst in Polymerization Reaction (1) CO 2 , PO, phthalic anhydride as raw materials to prepare polypropylene carbonate Polymerization process: The catalyst prepared in the examples and comparative examples was mixed with pretreated PO and phthalic anhydride (n 催化剂 :n PO :n 邻苯二甲酸酐 =5000:1:1) was added into a 500 mL vacuum dried autoclave and heated with CO at room temperature. 2 Replace the air in the autoclave 2-3 times. Then, fill it with 3 MPa of CO 2gas, set the reaction temperature to 25℃ and the reaction time to 40 h. After the reaction is completed, cool to room temperature, release the pressure to normal pressure, open the autoclave, filter and separate the solid catalyst, dissolve the crude product with dichloromethane, remove the unreacted reactants and residual dichloromethane solvent by reduced pressure distillation, weigh and record. After the distillation is completed, dissolve the remaining polymer in tetrahydrofuran, slowly add 5% HCl anhydrous ethanol solution, let it stand, precipitate, and obtain a large amount of white polymer precipitate, filter, repeat 2~3 times, and vacuum dry the copolymer at 50℃ for 6 hours, weigh and record to obtain the target compound. The separated solid catalyst is continued to be used in the reaction and reused 6 times.

[0066] Data analysis: The yield of polypropylene carbonate was the average data of 6 consecutive reuses of the catalyst, and the median was taken for the remaining data. The results are shown in Table 3.

[0067] Table 3

[0068] (2) CO 2 , PO, and maleic anhydride as raw materials for preparing polypropylene carbonate The aggregation process and data analysis are the same as (1). The results are shown in Table 4.

[0069] Table 4

[0070] It can be seen from Table 1 and Table 2 that under the same conditions, the present invention uses a mesoporous molecular sieve to first encapsulate the Salen metal catalyst, and then uses a silanol bond to graft the catalyst to obtain a solid-supported catalyst. When applied to the polymerization reaction of polypropylene carbonate, the yield of polypropylene carbonate can be improved, the glass transition temperature of the polymer can be increased, the carbonate chain content and the thermal decomposition temperature can be increased, and the separation degree between the catalyst and the polymer can also be improved. The recovery rate of the catalyst after solidification is greatly improved.

[0071] The above are only preferred embodiments of the present invention. It should be noted that the above preferred embodiments should not be regarded as limiting the present invention, and the protection scope of the present invention should be based on the scope defined by the claims. For ordinary technicians in this technical field, several improvements and modifications can be made without departing from the spirit and scope of the present invention, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a Salen-Co(III)-X immobilized catalyst, characterized in that: The following steps are involved: S1. Preparation of Salen ligand; S2, firstly mixing the solvent, the Salen ligand obtained in S1 and the mesoporous molecular sieve, reacting under a protective atmosphere, then adding a solution containing a Co compound to continue the reaction, drying and then oxidizing the reactants to obtain a mesoporous molecular sieve encapsulated Salen-Co(III)-X catalyst; S3, grafting the co-catalyst onto the mesoporous molecular sieve encapsulated Salen-Co(III)-X catalyst obtained in S2 via silanol bonds.

2. The preparation method according to claim 1, characterized in that In S2, the mass ratio of the amount of the Salen ligand obtained in S1 to the mesoporous molecular sieve is 1-10 mmol / g.

3. The preparation method according to claim 1, characterized in that: In S2, the molar ratio of the Salen ligand obtained in S1 to the Co compound is 1:(1~2).

4. The preparation method according to claim 1, characterized in that: The mesoporous molecules are selected from any one of MCM-22 and MCM-41.

5. The preparation method according to claim 1, characterized in that: The Co compound is selected from any one of anhydrous cobalt acetate and anhydrous cobalt nitrate.

6. The preparation method according to any one of claims 1 to 5, characterized in that: The oxidation step in S2 is specifically as follows: after the reactant is dried, dichloromethane and an ethanol solution of LiCl are added, oxygen is introduced, the reaction is stirred at room temperature in the dark, and after the reaction is completed, the solid is separated and dried.

7. The preparation method according to claim 1, characterized in that: The co-catalyst is a tertiary amine satisfying the general formula [CH3(CH2) n ]3N, n=1~6.

8. The preparation method according to claim 1 or 7, characterized in that: The S3 is specifically: mixing the Salen-Co(III)-X catalyst encapsulated in the mesoporous molecular sieve obtained in S2 with the silanol bond raw material, adding a solvent for reaction, adding a co-catalyst after the reaction is completed, continuing the reaction, and drying the obtained reactant.

9. A Salen-Co(III)-X supported catalyst prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the Salen-Co(III)-X supported catalyst according to claim 9 in the preparation of polypropylene carbonate.

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