Fe (at) Sn-NMC catalyst, preparation method thereof and application of Fe (at) Sn-NMC catalyst in catalysis of B-V reaction

Abstract

The invention belongs to the technical field of catalytic materials, and particularly discloses a Fe-Sn-NMC catalyst, a preparation method thereof and application of the Fe-Sn-NMC catalyst to catalysis of B-V reaction, oxygen is used as a green oxidant, aldehydes are used as a co-oxidant, Fe-Sn-NMC is used as the catalyst, and ketones are catalytically oxidized to synthesize esters. A catalyst, ketone and aldehyde are added into a reactor containing a solvent, oxygen is introduced by a bubbling method, heating and stirring are performed, the catalyst is filtered out after the reaction is finished, and the highest ketone conversion rate can reach 98% and the highest yield can reach 98% after gas chromatographic analysis. The Fe-Sn-NMC catalyst prepared by the method is simple to prepare and mild in reaction condition, has the advantages of high activity, high selectivity, good stability and the like, has excellent repeatability, still has good catalytic activity after being circulated for 9 times, and has a good industrial prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of catalytic materials, and relates to a Fe@Sn-NMC catalyst and a preparation method thereof and use of the catalyst in catalyzing a BV reaction, and in particular to use of a three-dimensional porous Fe@Sn-NMC catalyst in a Baeyer-Villiger (BV) oxidation reaction. Background Art

[0002] The reaction of directly inserting oxygen atoms into the ketone molecule to generate esters is called the Baeyer-Villiger reaction (BV oxidation reaction). The Baeyer-Villiger reaction was first discovered by Baeyer and Villiger in 1899. Subsequent researchers expanded the research and found a large number of cyclic ketones that can be oxidized to lactones by peracids, and speculated on the mechanism of the reaction. This type of reaction is named the Baeyer-Villiger oxidation rearrangement reaction. The Baeyer-Villiger reaction (BV oxidation reaction) oxidation method is divided into H2O2 oxidation method, O2 oxidation method, peracid oxidation method and biological oxidation method according to the different raw materials. Although the peracid oxidation method has been maturely used in industrial production, organic peracids are not only expensive, but also have certain dangers in the subsequent purification and concentration of peracids during the production process. It also produces a lot of acidic waste and pollutes the environment. In addition, it is also difficult to recycle carboxylic acids and separate late by-products. In addition, the use of biological oxidation method to prepare ε-caprolactone by utilizing the specificity and efficiency of enzymes is more environmentally friendly and has milder reaction conditions, but it has poor stability, high production costs, high environmental requirements, and high environmental risks. The H2O2 oxidation method uses cheap and easily available low-concentration H2O2 as an oxidant. Since the by-product is water, the reaction is clean and pollution-free, but H2O2 is easy to decompose and inconvenient to transport. Therefore, the O2 oxidation method uses molecular O2 as an oxidant, which is clean, safe, and inexpensive, meets the requirements of the current development of green chemistry, and is favored by more and more scholars.

[0003] Metal-organic frameworks are hybrid porous materials made of organic linkers and metal clusters or ions, suitable for stabilizing metal nanoparticles. In addition, the size of metal particles can be adjusted by the cavities and windows of MOFs. Controlling the size of metal particles allows access to active catalytic sites and overcomes several obstacles, such as difficulty in recovery from the reaction environment, agglomeration, and accumulation of nanoparticles. Organic ligands with specific functional groups can be obtained by pre-screening, and then MOFs with functional groups can be obtained. The presence of functional groups can also affect the yield or selectivity of the catalytic reaction. At present, the existing BV oxidation catalysts are mostly metal oxides or supported on molecular sieves, most of which have low reaction efficiency and unstable catalytic effect. For example, Subramanian et al. used MCM-48 molecular sieve as a carrier to prepare a supported catalyst Fe-MCM-48 (Fe = 0.54wt.%), 1,2-dichloroethane as a solvent, molecular oxygen as an oxidant, and benzaldehyde as a co-oxidant. The catalyst Fe-MCM-48 was used to catalyze the oxidation of cyclohexanone. The results showed that the yield reached 62%, and the catalyst was only recycled three times.

[0004] Based on the above problems, it is urgent to develop a catalyst suitable for the BV oxidation reaction of ketones that can improve the catalytic reaction efficiency and have good stability. Summary of the invention

[0005] The purpose of the present invention is to provide a three-dimensional porous Fe@Sn-NMC catalyst for use in a Baeyer-Villiger oxidation reaction.

[0006] The technical solution of the present invention is to provide an application of a three-dimensional porous Fe@Sn-NMC catalyst in a Baeyer-Villiger oxidation reaction and an application method thereof, with ketone as a substrate, aldehyde as a co-oxidant, oxygen as a green oxidant, Fe@Sn-NMC as a catalyst, mild reaction conditions, high conversion rate and yield, high atomic utilization rate, easy recovery and reuse of the catalyst, many cycles, up to 9 cycles, and stable catalytic effect, and the catalyst is a three-dimensional porous Fe@Sn-NMC.

[0007] The specific technical solution for implementing the present invention is:

[0008] A method for catalyzing a Baeyer-Villiger (BV) reaction using a Fe@Sn-NMC catalyst comprises the following steps: sequentially mixing the Fe@Sn-NMC catalyst, a solvent, a ketone and a co-oxidant aldehyde, introducing oxygen, stirring and heating, separating the Fe@Sn-NMC catalyst after the reaction is completed, and subjecting the reaction solution to reduced pressure distillation to obtain a product.

[0009] In some preferred embodiments, the Fe@Sn-NMC catalyst uses SiO2 balls as templates, ZIF as a carbon substrate, and is modified with iron and tin elements; wherein Fe and Sn bimetallics are at the ZIF site to form Fe@Sn-ZIF; only the spherical structure formed by the template SiO2 is retained, and Fe@Sn-ZIF is attached to the surface of the SiO2 spherical structure to form a nano-carbon structure interconnected with the SiO2 nano-balls, and after NaOH etching, the SiO2 ball template is removed to form a nitrogen-doped carbon Fe@Sn-NMC catalyst;

[0010] and / or

[0011] The Fe@Sn-NMC catalyst is a three-dimensional porous material; and / or

[0012] The pores of the Fe@Sn-NMC catalyst are orderly; and / or

[0013] The pores of the Fe@Sn-NMC catalyst have a pore diameter of 20 to 40 nm; and / or

[0014] The Fe@Sn-NMC catalyst has a spherical structure; and / or

[0015] The SiO2 particle size is 200-300nm.

[0016] In some preferred embodiments, the ketone is selected from any one or a combination of two or more of the following groups: cyclohexanone, 2-methylcyclohexanone, cyclopentanone, adamantane ketone; and / or

[0017] The aldehydes are selected from any one or a combination of two or more of the following groups: benzaldehyde, 4-methylbenzaldehyde, tert-butylaldehyde; and / or

[0018] The solvent is selected from 1,2-dichloroethane and / or sec-butyl acetate.

[0019] In some preferred embodiments, the mass of the Fe@Sn-NMC catalyst is 4% to 10% of the mass of the ketone.

[0020] In some preferred embodiments, the conditions of the BV reaction include:

[0021] The reaction temperature is 45 to 65°C; and / or

[0022] The reaction time is 4 to 7 hours; and / or

[0023] The oxygen flow rate is 15-30 mL / min.

[0024] In some preferred embodiments, the ratio of the amount of cyclohexanone to the solvent is 1.96 g: (8-30) mL; that is, the amount of the cyclohexanone to the solvent is 1 / g: (5-20) / g; and / or

[0025] The molar ratio of the ketones to the aldehydes is 1:(1.5-3).

[0026] In a second aspect, the present invention provides a Fe@Sn-NMC catalyst.

[0027] In a third aspect, the present invention provides an application of the Fe@Sn-NMC catalyst in catalyzing a BV reaction.

[0028] In a fourth aspect, the present invention further provides a method for preparing the Fe@Sn-NMC catalyst, comprising the following steps:

[0029] 1) preparing silica microspheres; the particle size of the SiO2 is 200 to 300 nm;

[0030] 2) adding silica microspheres to a methanol solution containing tin tetrachloride pentahydrate and zinc nitrate hexahydrate, stirring after ultrasonication, and centrifugally drying to collect powder A;

[0031] 3) Pour powder A into methanol solution and then add benzimidazole and stir evenly, then add ferric nitrate nonahydrate, heat and stir, separate and dry to obtain the precursor Fe@Sn-ZIF-SiO2, in which the ZIF containing dual active sites of Fe and Sn is coated on the surface of SiO2 microspheres;

[0032] 4) annealing the above precursor at high temperature to obtain powder B;

[0033] 5) The obtained powder B is added to a NaOH solution for etching, and after washing, separation, and drying, the SiO2 template is removed and the spherical structure of SiO2 is retained to obtain a nitrogen-doped carbon Fe@Sn-NMC catalyst.

[0034] In some preferred embodiments, the mass ratio of tin tetrachloride pentahydrate to zinc nitrate hexahydrate is 1:(0.1-3); and / or

[0035] The mass ratio of the tin tetrachloride pentahydrate to the silicon dioxide microspheres is 1:(0.25-5); preferably, the mass of the silicon dioxide microspheres is 0.1-2 g; and / or

[0036] The mass ratio of tin tetrachloride pentahydrate to benzimidazole is 1:(1.25-5); preferably, the mass of the benzimidazole is 0.5-2 g; and / or

[0037] The mass ratio of the tin tetrachloride pentahydrate to the ferric nitrate nonahydrate is 1:(0.025-0.5); preferably, the mass of the ferric nitrate nonahydrate is 0.01-0.2 g; and / or

[0038] In the step 2), the volume of the methanol solution is 1 to 15 mL, and the ultrasonic time is 15 to 50 min;

[0039] In the step 4), high temperature annealing is performed in a tube furnace;

[0040] In the step 4), the high temperature annealing temperature is 500-900°C; the high temperature annealing time is 0.5-2.5h; the heating rate is 2-20°C / min; and / or

[0041] In the step 5), the etching temperature is 40 to 70° C.; the etching time is 10 to 48 hours; and / or

[0042] In the step 5), the preparation method of silica microspheres is as follows: tetraethyl silicate (ethanol aqueous solution / V: tetraethyl silicate / V=1: (0.5-1) mL) is added to ethanol aqueous solution (ethanol / V: water / V=1: (1-4) mL), and after stirring evenly, ammonia water (tetraethyl silicate / V: ammonia water / V=1: 0.5 mL) is added, and stirring is continued for 3-18 hours; and silica microspheres are obtained by centrifugation, washing, and drying.

[0043] Preferably, the concentration of the NaOH solution in step 5) is 1-2 mol / L.

[0044] The beneficial effects of the present invention are:

[0045] (1) Compared with the current Baeyer-Villiger oxidation reaction catalyst, the Fe@Sn-NMC catalyst of the present invention has high catalytic activity and good catalytic effect, with a maximum yield and conversion rate of more than 98%; at the same time, it has good stability and maintains good catalytic activity after 9 cycles.

[0046] (2) The Fe@Sn-NMC catalyst of the present invention has mild reaction conditions for catalytic oxidation of ketones to generate esters, does not require high temperature and high pressure, uses less solvent, and uses less co-oxidant, thus saving costs to a great extent.

[0047] (3) The present invention uses oxygen as an oxidant, which is green and pollution-free. DETAILED DESCRIPTION

[0048] The present invention is further described in detail below in conjunction with specific implementation modes.

[0049] The term "ZIF" herein refers to a zeolite imidazolate framework material, which is a MOF material with a zeolite structure synthesized by reacting Zn ions with imidazole ligands.

[0050] The term "NMC" herein refers to nitrogen-doped carbon materials.

[0051] Preparation of catalyst materials

[0052] Example 1

[0053] 1) Add 65 mL of ethanol to 25 mL of deionized water, stir for 15 min, then add 3 mL of tetraethyl silicate and stir thoroughly, finally add 10 mL of ammonia water, and stir the mixture for 8 h. Subsequently, the obtained mixed solution is centrifuged, washed, and dried to obtain silica microspheres.

[0054] 2) 1 g of silica microspheres was added to 10 mL of a methanol solution containing 0.4 g of tin tetrachloride pentahydrate and 0.4 g of zinc nitrate hexahydrate, and the mixture was stirred after ultrasonication and centrifuged to dry to collect powder A.

[0055] 3) Pour the dried and collected powder A into 10 mL of methanol solution, add 1.7 g of benzimidazole and stir evenly, then add 0.06 g of ferric nitrate nonahydrate, stir at 50° C. for 2 h, centrifuge and dry to obtain the desired precursor.

[0056] 4) The above precursor was annealed in a tube furnace at 900° C. for 2 h to obtain powder B.

[0057] 5) The obtained powder B was added to a 2M NaOH solution and etched in a 70°C water bath for 24 h, washed, centrifuged, and dried to obtain a Fe@Sn-NMC-1 catalyst.

[0058] Example 2

[0059] Based on Example 1, the step 2) is modified into the following steps:

[0060] 2) adding 1 g of silica microspheres to 10 mL of methanol solution containing 0.04 g of tin tetrachloride pentahydrate and 0.4 g of zinc nitrate hexahydrate, stirring after ultrasonication, and centrifuging and drying to collect powder A;

[0061] The other steps are the same as those in Example 1 to obtain the Fe@Sn-NMC-2 catalyst.

[0062] Example 3

[0063] Based on Example 1, the step 2) is modified into the following steps:

[0064] 2) adding 1 g of silica microspheres to 10 mL of methanol solution containing 1.2 g of tin tetrachloride pentahydrate and 0.4 g of zinc nitrate hexahydrate, stirring after ultrasonication, and centrifuging and drying to collect powder A;

[0065] The other steps are the same as in Example 1 to obtain the Fe@Sn-NMC-3 catalyst.

[0066] Example 4

[0067] Based on Example 1, the step 3) is modified into the following steps:

[0068] 3) Pour the dried collected powder A into 10 mL of methanol solution and add 1.7 g of benzimidazole and stir evenly, then add 0.01 g of ferric nitrate nonahydrate, stir at 50° C. for 2 h, centrifuge, and dry to obtain the desired precursor;

[0069] The other steps are the same as in Example 1 to obtain the Fe@Sn-NMC-4 catalyst.

[0070] Example 5

[0071] Based on Example 1, the step 3) is modified into the following steps:

[0072] 3) Pour the dried collected powder into 10 mL of methanol solution and add 1.7 g of benzimidazole and stir evenly, then add 0.2 g of ferric nitrate nonahydrate, stir at 50° C. for 2 h, centrifuge, and dry to obtain the desired precursor;

[0073] The other steps are the same as those in Example 1 to obtain the Fe@Sn-NMC-5 catalyst.

[0074] Example 6

[0075] Based on Example 1, step 1) is omitted, i.e., silica microspheres are not added.

[0076] The other steps are the same as in Example 1 to obtain the Fe@Sn-NMC-6 catalyst.

[0077] Example 7

[0078] Based on Example 1, the step 3) is modified into the following steps:

[0079] 3) Pour the dried collected powder A into 10 mL of methanol solution and add 1.7 g of benzimidazole and stir evenly, then add 0.06 g of cobalt nitrate hexahydrate, stir at 50° C. for 2 h, centrifuge, and dry to obtain the desired precursor;

[0080] The other steps are the same as in Example 1 to obtain the Co@Sn-NMC catalyst.

[0081] Example 8

[0082] Based on Example 1, the step 3) is modified into the following steps:

[0083] 3) Pour the dried collected powder A into 10 mL of methanol solution and add 1.7 g of benzimidazole and stir evenly, then add 0.06 g of copper nitrate trihydrate, stir at 50 ° C for 2 h, centrifuge, and dry to obtain the desired precursor;

[0084] The other steps are the same as in Example 1 to obtain the Cu@Sn-NMC catalyst.

[0085] Example 9

[0086] Based on Example 1, the step 2) is modified into the following steps:

[0087] 2) adding 1 g of silica microspheres to 10 mL of methanol solution containing 0.04 g of tin tetrachloride pentahydrate and 0.4 g of chromium nitrate hexahydrate, stirring after ultrasonication, and centrifuging and drying to collect powder A;

[0088] The other steps were the same as those in Example 1 to obtain the Fe@Sn-MIL catalyst.

[0089] Determination of cyclohexanone conversion and ε-caprolactone yield

[0090] Detection method:

[0091] The catalyst materials prepared in the above different embodiments, as well as cyclohexanone, benzaldehyde and 1,2-dichloroethane were added to a 50 mL three-necked flask, oxygen was introduced by bubbling method, the introduction rate of oxygen was adjusted, the reaction was carried out under stirring, and the temperature and time of the stirring reaction were controlled. After the reaction was completed, the catalyst was filtered and separated, and the product was weighed and analyzed by gas chromatography. The conversion rate of cyclohexanone and the yield of ε-caprolactone were calculated. The separated catalyst was washed with a solvent and then dried, and the reaction was repeated again for a cycle test.

[0092] The samples were tested by the internal standard method, and cyclohexanone, ε-caprolactone, benzaldehyde and benzoic acid were calibrated.

[0093] Relative correction factor calculation formula:

[0094]

[0095] f i Represents the relative correction factor of the component to be measured, m i Indicates the mass of the component to be tested, A i Represents the peak area of ​​the component to be tested, m s Indicates the mass of the internal standard, A s represents the peak area of ​​the internal standard.

[0096] The cyclohexanone conversion (C1) was calculated as follows:

[0097]

[0098] m1 represents the mass of unconverted cyclohexanone, m2 represents the total mass of cyclohexanone input, f1 represents the relative correction factor of cyclohexanone, A1 represents the peak area of ​​cyclohexanone, A s represents the peak area of ​​the internal standard, m s Indicates the mass of the added internal standard.

[0099] The selectivity of ε-caprolactone (S1) was calculated as follows:

[0100]

[0101] m3 represents the mass of ε-caprolactone generated, m4 represents the mass of ε-caprolactone generated theoretically from the converted cyclohexanone, m2 represents the total mass of cyclohexanone input, C1 represents the conversion rate of cyclohexanone, f2 represents the relative correction factor of ε-caprolactone, A2 represents the peak area of ​​ε-caprolactone, A s represents the peak area of ​​the internal standard, m s Indicates the mass of the added internal standard.

[0102] The yield (Y1) of ε-caprolactone is calculated as follows:

[0103] Y1=C1×S1

[0104] Table 1

[0105]

[0106]

[0107] Effects of different catalyst materials on cyclohexanone conversion, ε-caprolactone yield and cycle performance

[0108] The Fe@Sn-NMC-1 prepared in Example 1 and the Fe@Sn-NMC-2, Fe@Sn-NMC-3, Fe@Sn-NMC-4, Fe@Sn-NMC-5, Fe@Sn-NMC-6, Co@Sn-NMC, Cu@Sn-NMC and Fe@Sn-MIL prepared in Examples 2 to 9 were used as catalysts to test the cyclohexanone conversion rate, ε-caprolactone yield and cycle performance under the same conditions. The results are shown in Table 2.

[0109] Table 2

[0110]

[0111]

[0112] In summary, the optimal mass ratio of tin tetrachloride pentahydrate to zinc nitrate hexahydrate is 1:1, and the optimal mass ratio of tin tetrachloride pentahydrate to ferric nitrate nonahydrate is 1:0.15. At the same time, adding SiO2 as a sacrificial template greatly improves the cycle performance of the catalyst, and the loading amount of the dual active sites of iron and tin has a significant effect on the catalytic activity. In the case of tin as the basis, the catalytic activity is optimal under the synergistic effect of the two elements with iron.

[0113] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for catalyzing a Baeyer-Villiger (BV) reaction using a Fe@Sn-NMC catalyst, comprising: The Fe@Sn-NMC catalyst, solvent, ketones and co-oxidant aldehydes are mixed in sequence, oxygen is introduced, and the mixture is stirred and heated. After the reaction is completed, the Fe@Sn-NMC catalyst is separated, and the reaction solution is subjected to reduced pressure distillation to obtain the product.

2. A method for catalyzing BV reaction using a Fe@Sn-NMC catalyst according to claim 1, wherein: The Fe@Sn-NMC catalyst uses SiO2 balls as templates, ZIF as a carbon substrate, and is modified with iron and tin elements; Among them, Fe and Sn bimetallics are distributed on ZIF to form Fe@Sn-ZIF; SiO2 spheres were used as templates, and the Fe@Sn-NMC catalyst did not contain SiO2 material, and only the spherical structure of SiO2 was retained; A ZIF containing dual active sites of Fe and Sn (i.e., Fe@Sn-ZIF) is coated on the surface of the SiO2 spherical structure to form a nanocarbon structure Fe@Sn-NMC catalyst interconnected with the SiO2 spherical structure; and / or The Fe@Sn-NMC catalyst is a three-dimensional porous material; and / or The pores of the Fe@Sn-NMC catalyst are orderly; and / or The pores of the Fe@Sn-NMC catalyst have a pore size of 20 to 40 nm; and / or The Fe@Sn-NMC catalyst has a spherical structure; and / or The SiO2 particle size is 200-300nm.

3. The method for catalyzing BV reaction using Fe@Sn-NMC catalyst according to claim 1, wherein: The ketone is selected from any one or a combination of two or more of the following groups: cyclohexanone, 2-methylcyclohexanone, cyclopentanone, and adamantane ketone; and / or The aldehydes are selected from any one or a combination of two or more of the following groups: benzaldehyde, 4-methylbenzaldehyde, tert-butylaldehyde; and / or The solvent is selected from 1,2-dichloroethane and / or sec-butyl acetate.

4. The method for catalyzing BV reaction using Fe@Sn-NMC catalyst according to claim 1, wherein: The mass of the Fe@Sn-NMC catalyst is 4% to 10% of the mass of the ketones.

5. The method for catalyzing BV reaction using Fe@Sn-NMC catalyst according to claim 1, wherein: The conditions of the BV reaction include: The reaction temperature is 45 to 65°C; and / or The reaction time is 4 to 7 hours; and / or The oxygen flow rate is 15-30 mL / min.

6. The method for catalyzing BV reaction using Fe@Sn-NMC catalyst according to claim 1, wherein: The amount of cyclohexanone and solvent used is 1.96g: (8-30)mL and / or The molar ratio of the ketones to the aldehydes is 1:(1.5-3).

7. An Fe@Sn-NMC catalyst as claimed in any one of claims 1 to 6.

8. Use of the Fe@Sn-NMC catalyst according to claim 7 in catalyzing BV reaction.

9. A method for preparing the Fe@Sn-NMC catalyst according to claim 7, comprising the following steps: 1) preparing silica microspheres; the particle size of the SiO2 is 200 to 300 nm; 2) adding silica microspheres to a methanol solution containing tin tetrachloride pentahydrate and zinc nitrate hexahydrate, stirring after ultrasonication, and centrifugally drying to collect powder A; 3) Pour powder A into a methanol solution, add benzimidazole and stir evenly, then add ferric nitrate nonahydrate, heat and stir, separate and dry to obtain a precursor; 4) annealing the above precursor at high temperature to obtain powder B; 5) The obtained powder B is added to a NaOH solution for etching, and then washed, separated and dried to obtain a Fe@Sn-NMC catalyst.

10. The method for preparing the Fe@Sn-NMC catalyst according to claim 9, wherein: The mass ratio of the tin tetrachloride pentahydrate to the zinc nitrate hexahydrate is 1:(0.1-3); and / or The mass ratio of the tin tetrachloride pentahydrate to the silicon dioxide microspheres is 1:(0.25-5); and / or The mass ratio of tin tetrachloride pentahydrate to benzimidazole is 1:(1.25-5); and / or The mass ratio of the tin tetrachloride pentahydrate to the ferric nitrate nonahydrate is 1:(0.025-0.5); and / or In the step 4), the high temperature annealing temperature is 500-900° C.; the high temperature annealing time is 0.5-2.5 h; and / or In the step 5), the etching temperature is 40 to 70° C. and the etching time is 10 to 48 hours.

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