TEMPO immobilized catalyst as well as preparation method and application thereof

Abstract

The invention discloses a TEMPO immobilized catalyst, a preparation method thereof and application of the TEMPO immobilized catalyst in benzoin oxidation reaction. Aiming at the problems that TEMPO is difficult to recover, TEMPO is easy to lose or a catalytic base material structure is unstable in an existing immobilization mode and the like, dialdehyde terphenyl (monomer I) with TEMPO and a monomer II with active methylene are reacted, a TEMPO immobilized catalyst is prepared through condensation reaction, a reaction center (TEMPO) of the TEMPO immobilized catalyst is immobilized on a catalyst framework through a covalent bond, and the TEMPO immobilized catalyst is prepared through a covalent bond. The catalyst has the characteristics of low TEMPO inactivation rate, good stability, high activity and capability of being simply filtered, recycled and repeatedly used.

Description

Technical Field

[0001] The invention relates to the technical field of catalysts, and in particular to a TEMPO immobilized catalyst and a preparation method and application thereof. Background Art

[0002] TEMPO (2,2,6,6-tetramethylpiperidinyl oxide or 2,2,6,6-tetramethylpiperidinyl 1-oxyl) is an important oxidation reaction catalyst. Due to its good effect in catalytic reactions, it has also become a major research hotspot in the field of catalysis. As a highly efficient catalyst, TEMPO is difficult to recycle, which brings about problems such as high catalytic cost and heavy pollution. Some people have adsorbed TEMPO on a catalytic substrate to achieve the purpose of fixing and recovering the TEMPO catalyst. However, not only does the structure of the catalytic substrate affect the catalytic reaction, but the TEMPO that is physically adsorbed can easily fall off, causing the loss of TEMPO. Some people have also bonded TEMPO to the catalytic substrate by chemical bonds, but the structure of these catalytic substrates is unstable, which has a great impact on the catalytic effect.

[0003] Organic framework materials (COFs) have obvious advantages in the field of catalysis. Their structure is highly ordered, and their pore size is uniform and adjustable, which facilitates substrate transport and selective catalysis. They have a large specific surface area and can provide abundant catalytic active sites. They are connected by covalent bonds and have good chemical and thermal stability. In addition, their structure is easy to functionalize and can be customized according to the needs of different catalytic reactions, showing excellent catalytic performance in heterogeneous catalysis.

[0004] Benzil is an important organic chemical raw material, and can also be used for the synthesis of various drugs and photosensitizers, pesticides, printing inks for food packaging, and corrosion inhibitors for low-carbon steel. It is mainly used as a photoinitiator for ultraviolet assimilation resins and coatings. Within the effective wavelength range, its initiation efficiency, curing speed, thick film solid, resistance to impurity interference, and matching with pigments are better than benzoin ethers and benzophenones. The industrial synthesis of benzil is mostly oxidized by concentrated nitric acid, so a lot of waste acid and nitrogen and oxygen gases that are not friendly to the environment are generated. In order to better meet the requirements of green chemistry, the present invention provides a green and environmentally friendly oxidation method. Summary of the invention

[0005] To solve the above problems, the purpose of the present invention is to provide a TEMPO supported catalyst and a preparation method thereof and application thereof in benzoin oxidation reaction. The present invention reacts a dialdehyde terphenyl (monomer I) with TEMPO with a monomer II with an active methylene group. The methylene group in the monomer II is affected by a strong electron withdrawing group (cyano group), and the two hydrogen atoms on the methylene group are very easy to leave, and have strong acidity. Therefore, under certain conditions, it can undergo a condensation reaction with the aldehyde group in the monomer I, remove a molecule of water, obtain a carbon-carbon double bond, and obtain a structure as shown below.

[0006]

[0007] Catalyst I obtained by reacting monomer I of formula (IV) with monomer II of formula (V-1)

[0008]

[0009] Catalyst II obtained by reacting monomer I of formula (IV) with monomer II of formula (V-II)

[0010] The reaction center (TEMPO) of the TEMPO supported catalyst obtained by the present invention is supported on the catalyst framework by covalent bonds, and compared with the scheme of physical adsorption on the carrier, the TEMPO has the characteristics of low TEMPO deactivation rate, good stability, high activity, etc. At the same time, the catalyst can be repeatedly recycled and used after simple filtration after the reaction is completed. The present invention also discloses a scheme of using the catalyst to oxidize benzoin to benzil.

[0011] The technical solution adopted by the present invention is:

[0012] A TEMPO immobilized catalyst as shown in structure I and a preparation method thereof, wherein the catalyst is prepared by reacting a monomer A as shown in structure II and a monomer B as shown in structure III in a certain ratio in the presence of a catalyst for a certain period of time, followed by filtration and THF washing;

[0013]

[0014] The monomer A of the structure shown in II is preferably the dialdehyde terphenyl TEMPO amide shown in formula (IV); the monomer B of the structure shown in III is preferably two active methylene compounds shown in formula (V-1) and formula (V-2);

[0015]

[0016] The preparation method of the TEMPO immobilized catalyst comprises the following steps: adding monomer A and monomer B into an organic solvent in a certain proportion, reacting at a temperature of 100 to 130° C. in the presence of a catalyst, and reacting for 24 to 72 hours; the organic solvent is o-dichlorobenzene or a mixed solvent of o-dichlorobenzene and n-butanol in a mass ratio of 1:0 to 3; and the catalyst is solid KOH or an aqueous solution of 1,8-diazabicyclo[5.4.0]undec-7-ene.

[0017] The preparation method of the TEMPO immobilized catalyst comprises the following steps: the catalyst is solid KOH or 1,8-diazabicyclo[5.4.0]undec-7-ene aqueous solution; the amount of solid KOH added is such that the molar ratio of monomer A to KOH is 1:3-5; the amount of 1,8-diazabicyclo[5.4.0]undec-7-ene aqueous solution added is such that the mass ratio of monomer 1 to the mass ratio of 1,8-diazabicyclo[5.4.0]undec-7-ene aqueous solution is 1:4-7; and the concentration of the 1,8-diazabicyclo[5.4.0]undec-7-ene aqueous solution is 4-7 mol / L.

[0018] In the preparation method of the TEMPO immobilized catalyst, the molar ratio of the monomer A to the monomer B is 1:0.67-1.

[0019] The preparation method of the TEMPO immobilized catalyst comprises the following steps: the reaction temperature is 100° C. to 130° C., preferably 110° C. to 120° C.; and the reaction time is 24 h to 72 h, preferably 36 h to 48 h.

[0020] The TEMPO immobilized catalyst is used in the preparation of benzil from benzoin by oxidation. The raw material benzoin is dissolved in glacial acetic acid, sodium nitrite, 1,3-dibromo-5,5-dimethylhydantoin (hereinafter referred to as DBDMH) and the TEMPO immobilized catalyst are added, the temperature is increased in an oxygen environment, the catalyst is filtered out after a certain reaction time, the solvent glacial acetic acid is evaporated, and then the product is washed with water.

[0021] The use of the TEMPO immobilized catalyst in the oxidation of benzoin to prepare benzil is characterized in that the molar ratio of sodium nitrite to benzoin is 0.2-0.4:1, the molar ratio of DBDMH to benzoin is 0.05-0.1:1, the reaction temperature is 40-90°C, preferably 50-70°C, and the reaction time is 1-2h.

[0022] The application of benzoin oxidation to prepare benzil, the reaction formula is as follows:

[0023]

[0024] The beneficial effects of the present invention are: providing a method for preparing a recyclable TEMPO immobilized catalyst and a green method in the benzoin oxidation reaction.

[0025] The present invention aims to solve the problems that TEMPO is difficult to recycle, TEMPO is easily lost or the structure of the catalytic substrate is unstable in the existing immobilization method, and the present invention reacts a dialdehyde terphenyl (monomer I) carrying TEMPO with a monomer II carrying an active methylene group to obtain a TEMPO immobilized catalyst through a condensation reaction, wherein the reaction center (TEMPO) is immobilized on the catalyst framework through a covalent bond, and the TEMPO has the advantages of low TEMPO deactivation rate, good stability, high activity and can be simply filtered, recovered and reused. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a physical picture of the catalyst I obtained in the present invention;

[0027] Figure 2 This is a physical picture of the catalyst II obtained in the present invention;

[0028] Figure 3 is a scanning electron microscope (SEM) image of the catalyst I obtained in the present invention;

[0029] Figure 4 is a scanning electron microscope (SEM) image of the catalyst II obtained in the present invention;

[0030] Figure 5 is a transmission electron microscope (TEM) image of the catalyst I obtained in the present invention;

[0031] Figure 6 This is a transmission electron microscope (TEM) image of the catalyst II obtained in the present invention. DETAILED DESCRIPTION

[0032] The present invention is further described below in conjunction with specific embodiments, but the protection scope of the present invention is not limited thereto:

[0033] Example 1

[0034] Monomer A (65.24 mg, 0.135 mmol), monomer B of formula (V-1) (38.1 mg, 0.09 mmol), KOH (30.3 mg, 0.54 mmol), 1.7 mL of o-dichlorobenzene and 3.3 mL of n-butanol were added into the reactor, stirred and heated to 100°C. After keeping the temperature for 72 hours, the mixture was filtered and the filter cake was washed with DMF and THF to obtain 95.3 mg of catalyst I with a yield of 92.2%.

[0035] The obtained catalyst I was a light yellow powder ( Figure 1 ). Scanning electron microscope (SEM) analysis showed that the catalyst was in the form of round cake particles ( Figure 3), there are mesh gaps between particles, which is conducive to the mass transfer of reactants on the catalyst surface. Transmission electron microscopy (TEM) analysis shows that the catalyst has a regular mesh structure ( Figure 5 ), indicating that the catalyst has good crystal form retention, which is beneficial to improve the selectivity of the reaction and reduce the formation of by-products.

[0036] Example 2

[0037] Monomer A (65.24 mg, 0.135 mmol), monomer B of formula (V-1) (38.1 mg, 0.09 mmol) and KOH (30.3 mg, 0.54 mmol), 1.7 mL of o-dichlorobenzene and 3.3 mL of n-butanol were added into the reactor, stirred and heated to 130°C. After reacting for 72 h, the mixture was filtered and the filter cake was washed with DMF and THF to obtain 95.8 mg of catalyst I with a yield of 92.7%.

[0038] Example 3

[0039] Monomer A (65.24 mg, 0.135 mmol), monomer B of formula (V-1) (38.1 mg, 0.09 mmol) and KOH (30.3 mg, 0.54 mmol), 1.7 mL of o-dichlorobenzene and 3.3 mL of n-butanol were added to the reactor, stirred and heated to 130°C. After reacting for 24 hours, the mixture was filtered and the filter cake was washed with DMF and THF to obtain 89.2 mg of catalyst I with a yield of 86.3%.

[0040] Example 4

[0041] Monomer A (65.24 mg, 0.135 mmol), monomer B of formula (V-1) (38.1 mg, 0.09 mmol) and KOH (30.3 mg, 0.54 mmol), 1.25 mL of o-dichlorobenzene and 3.75 mL of n-butanol were added into the reactor, stirred and heated to 100°C. After reacting for 72 h, the mixture was filtered and the filter cake was washed with DMF and THF to obtain 86.5 mg of catalyst I with a yield of 83.7%.

[0042] Example 5

[0043] Monomer A (87.0 mg, 0.18 mmol), monomer B-2 of formula (V-2) (14.8 mg, 0.12 mmol) and KOH (40.4 mg, 0.72 mmol), 1.7 mL of o-dichlorobenzene and 3.3 mL of n-butanol were added into the reactor, stirred and heated to 100°C. After reacting for 72 h, the mixture was filtered and the filter cake was washed with DMF and THF to obtain 84.2 mg of catalyst II with a yield of 82.7%.

[0044] The obtained catalyst II was a light yellow powder ( Figure 2). Scanning electron microscope (SEM) analysis showed that the catalyst was in the form of round cake particles ( Figure 4 ), there are mesh-like gaps between particles, which is conducive to the mass transfer of reactants on the catalyst surface. Transmission electron microscopy (TEM) analysis shows that the catalyst surface structure is uniform and the pores are regular ( Figure 6 ), indicating that the catalyst has good crystal form retention, which is beneficial to improve the selectivity of the reaction and reduce the formation of by-products.

[0045] Example 6

[0046] Monomer A (87.0 mg, 0.18 mmol), monomer B-2 of formula (V-2) (14.8 mg, 0.12 mmol) and KOH (40.4 mg, 0.72 mmol), 1.25 mL of o-dichlorobenzene and 3.75 mL of n-butanol were added into the reactor, stirred and heated to 100°C. After reacting for 72 hours, the mixture was filtered and the filter cake was washed with DMF and THF to obtain 82.6 mg of catalyst II with a yield of 81.1%.

[0047] Example 7

[0048] Monomer A (87.0 mg, 0.18 mmol), monomer B-2 of formula (V-2) (14.8 mg, 0.12 mmol) and KOH (40.4 mg, 0.72 mmol), 1.7 mL of o-dichlorobenzene and 3.3 mL of n-butanol were added into the reactor, stirred and heated to 130°C. After reacting for 72 h, the mixture was filtered and the filter cake was washed with DMF and THF to obtain 89.8 mg of catalyst II with a yield of 88.2%.

[0049] Example 8

[0050] Monomer A (87.0 mg, 0.18 mmol), monomer B-2 of formula (V-2) (14.8 mg, 0.12 mmol), KOH (40.4 mg, 0.72 mmol) and 5 mL of o-dichlorobenzene were added into the reactor, stirred and heated to 130°C. After reacting for 24 hours, the mixture was filtered and the filter cake was washed with DMF and THF to obtain 80.6 mg of catalyst II with a yield of 79.2%.

[0051] Example 9

[0052] The raw material benzoin (42.4 mg, 0.2 mmol) was dissolved in 1 g of glacial acetic acid, and NaNO2 (4.1 mg, 0.06 mmol), DBDMH (4.3 mg, 0.015 mmol) and 4.2 mg of catalyst I were added. The above raw materials were placed in a three-necked flask, replaced with oxygen three times, sealed with a balloon, stirred and heated to 60°C, and reacted for 1.5 hours. After the reaction was completed, the catalyst was filtered out, and the solvent was removed from the filtrate by reduced pressure distillation. The filter cake was washed with water and then dried to obtain 40.7 mg of solid benzil product. The purity was 98.3% by liquid chromatography analysis, and the molar yield was 95.3%.

[0053] Example 10

[0054] The raw material benzoin (42.4 mg, 0.2 mmol) was dissolved in 0.85 g of glacial acetic acid, and NaNO2 (2.8 mg, 0.04 mmol), DBDMH (5.7 mg, 0.02 mmol) and 12.7 mg of catalyst I were added. The above raw materials were placed in a three-necked flask, replaced with oxygen three times, sealed with a balloon, stirred and heated to 40°C, and reacted for 2 hours. After the reaction was completed, the catalyst was filtered out and the solvent was removed from the filtrate by vacuum distillation. The filter cake was washed with water and then dried to obtain 40.2 mg of solid benzil product. The purity was 98.8% by liquid chromatography analysis and the molar yield was 94.6%.

[0055] Embodiment 11

[0056] The raw material benzoin (42.4 mg, 0.2 mmol) was dissolved in 12.7 g of glacial acetic acid, and NaNO2 (5.5 mg, 0.08 mmol), DBDMH (2.9 mg, 0.01 mmol) and 8.5 mg of catalyst I were added. The above raw materials were placed in a three-necked flask, replaced with oxygen three times, sealed with a balloon, stirred and heated to 90°C, and reacted for 1 hour. After the reaction was completed, the catalyst was filtered out and the solvent was removed from the filtrate by vacuum distillation. The filter cake was washed with water and then dried to obtain 41.1 mg of solid benzil product. The purity was 98.1% by liquid chromatography analysis and the molar yield was 96.0%.

[0057] Example 12

[0058] The catalyst I-1 in Example 9 was replaced with an equal amount of catalyst II, and other conditions remained unchanged to obtain 39.3 mg of solid benzil product. The purity was 98.6% as analyzed by liquid chromatography, and the molar yield was 92.2%.

[0059] Examples 13-17

[0060] The catalyst obtained by filtering after the reaction in Example 9 was dried to obtain a recovered catalyst I. The recovered catalyst I was recycled and utilized in Examples 13-16.

[0061] The catalyst I in Example 9 was replaced with the recovered catalyst I, and other conditions were unchanged and recycled for 5 times. The results are shown in the following table. From the data in the table, it can be seen that after the catalyst I was recycled 5 times, the product purity and purity of the catalyst I were slightly changed from those of Example 9, indicating that the recycling activity of the catalyst I was high.

[0062]

Claims

1. A TEMPO immobilized catalyst, characterized in that: Its structure is shown in Formula I or Formula II:

2. The method for preparing the TEMPO immobilized catalyst according to claim 1, characterized in that: The following steps are involved: Monomer A and monomer B react in the presence of a catalyst, and after the reaction, the TEMPO immobilized catalyst is obtained by filtering and washing; The monomer A is a dialdehyde terphenyl TEMPO amide as shown in formula (IV); the monomer B is two active methylene compounds as shown in formula (V-1) or formula (V-2); 3. The method for preparing the TEMPO immobilized catalyst according to claim 2, characterized in that: The reaction temperature is 100-130°C, and the reaction time is 24-72h.

4. The method for preparing the TEMPO immobilized catalyst according to claim 3, characterized in that: The reaction temperature is 110°C to 120°C, and the reaction time is 36h to 48h.

5. The method for preparing the TEMPO immobilized catalyst according to claim 2, characterized in that: The organic solvent for the reaction is o-dichlorobenzene or a mixed solvent of o-dichlorobenzene and n-butanol, and the mass ratio thereof is 1:0.01-3.

6. The method for preparing the TEMPO immobilized catalyst according to claim 2, characterized in that: The catalyst is solid KOH or 1,8-diazabicyclo[5.4.0]undec-7-ene aqueous solution.

7. The method for preparing the TEMPO immobilized catalyst according to claim 2, characterized in that: The molar ratio of monomer A to monomer B is 1:0.67-1.

8. Use of the TEMPO supported catalyst as claimed in claim 1 in the preparation of benzil by oxidation of benzoin.

9. The use according to claim 8, characterized in that Specifically include: The raw material benzoin is dissolved in glacial acetic acid, sodium nitrite, 1,3-dibromo-5,5-dimethylhydantoin and TEMPO immobilized catalyst are added, the temperature is raised in an oxygen environment, the catalyst is filtered out after the reaction, the solvent glacial acetic acid is evaporated, and then benzil is washed with water to obtain the product.

10. The use according to claim 9, characterized in that The molar ratio of sodium nitrite to benzoin is 0.2-0.4:1; The molar ratio of 1,3-dibromo-5,5-dimethylhydantoin to benzoin is 0.05-0.1:1; the reaction temperature is 40-90° C., and the reaction time is 1-2 hours.

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