Preparation and use method of a refined cotton-supported Co3O4 catalyst

Abstract

The present invention discloses a method for preparing and using a refined cotton-supported Co3O4 catalyst. The preparation method comprises: 1) pretreatment of refined cotton; 2) immobilizing Co3O4 on refined cotton: sequentially adding the neutral gel-like refined cotton, Co(Ac)2·4H2O, and ethanol to a flat-bottomed flask, then adding a certain amount of NaOH to the ethanol solution, ultrasonicating until it dissolves, slowly dripping the NaOH ethanol solution into the refined cotton cobalt system, continuing to stir at room temperature for 12 hours, the system will change from gray to dark brown, rotary evaporation to obtain a dark brown solid, and sequentially washing with ethanol and distilled water three times each to remove excess Ac- and other impurities. 3) post-treatment of the catalyst: placing the solid catalyst in step 2) in a vacuum drying oven under reduced pressure and drying to obtain a refined cotton-supported Co3O4 catalyst. The advantages of the present invention are that the catalyst carrier refined cotton used is abundant and easily available, and the method for preparing the supported catalyst is simple and easy to operate.

Description

Technical Field

[0001] The present invention relates to the technical field of catalytic material preparation, and in particular to a method for preparing a catalyst using refined cotton to immobilize metal oxide Co3O4 and its use. Background Art

[0002] Epoxides play a crucial role in pharmaceutical chemistry and fine chemistry, particularly as important organic chemical intermediates, with widespread applications in food, pharmaceuticals, fragrances, and other fields. Cobalt oxides have been reported to effectively catalyze the synthesis of epoxides from olefins, particularly in heterogeneous catalysis using molecular oxygen (air or oxygen) as the oxidant. This process has attracted attention due to its mild and environmentally friendly nature. This technology, in turn, relies heavily on the activity of the cobalt-containing catalyst. One approach to improving catalytic activity remains to reduce the size of the active particles to expose more surface active sites, effectively exploiting the size effect in nanocatalysis. Therefore, selecting suitable supports to obtain smaller, more dispersed, and more stable metal ions or oxides for catalytic reactions with organic compounds remains a goal.

[0003] Cellulose has the following advantages as a catalyst carrier material: (1) Cellulose has good stability and is resistant to dilute acids, alkalis, and various organic solvents; (2) Due to the rigidity of the cellulose molecular chain, cellulose in nature often has a nano-multi-level porous structure, which is more conducive to the dispersion of metal particles in the three-dimensional space of the fiber; (3) The cellulose molecular chain contains a wealth of characteristic functional groups (-OH, COC), which will strongly interact with metal particles and thus anchor the metal. Therefore, cellulose can be used as a carrier material to immobilize active metal oxides and construct cellulose / cobalt-supported catalysts.

[0004] In the prior art, molecular sieves such as Na-ZSM-5, MCM-41, Na-Y, and Na-β, or natural layered or porous minerals such as kaolinite, vermiculite, illite, montmorillonite, and rectorite, are generally used as carriers for immobilizing active metal oxides. However, relatively few reports have been published on the use of organic polymers, particularly environmentally friendly natural polymers, as carrier materials. Cellulose, the most abundant natural polymer in nature, is widely found in plant cell walls. It possesses numerous functional groups, a multi-layered pore structure, and excellent biocompatibility and biodegradability, making it an ideal raw material for constructing functional materials. Therefore, the development of catalysts using cellulose as a carrier is of great significance. Summary of the Invention

[0005] In order to solve the problems existing in the prior art, the purpose of the present invention is to provide a method for preparing a catalyst of Co3O4 immobilized on refined cotton. The refined cotton used as the catalyst carrier is abundant in source and easy to obtain, and the method for preparing the loaded catalyst is simple and easy to operate.

[0006] Another object of the present invention is to provide a catalyst prepared by the above-mentioned preparation method for use in catalyzing olefin epoxidation, which has the characteristics of short reaction time, high reaction conversion rate and mild reaction conditions.

[0007] To further achieve the above objectives, the present invention adopts the following technical solutions:

[0008] A method for preparing a refined cotton-supported Co3O4 catalyst comprises refined cotton as a carrier and an active ingredient, Co3O4, supported on the refined cotton. The active ingredient, Co3O4, is loaded in an amount ranging from 0.5 to 15 wt%, where the loading amount is the mass of Co3O4 relative to the carrier refined cotton. The preparation method comprises the following steps:

[0009] 1) Pretreatment: Refined cotton was added to a swelling solution formed by mixing alkali and urea for 30 minutes. The mixture was then frozen at -20°C for 48 hours and thawed. The mixture was vigorously stirred at room temperature for 25 minutes. The mixed solution was centrifuged, the supernatant was discarded, and deionized water was added. This process was repeated several times to obtain a neutral gel-like purified cotton with a solid content of 13%.

[0010] 2) Immobilized Co3O4: The neutral gel-like purified cotton, cobalt acetate, and ethanol were sequentially added to a flat-bottomed flask. After stirring at room temperature for 1 hour, the mixture was ultrasonically treated at 700W for 30 minutes to form a purified cotton cobalt system. NaOH was then added to the ethanol solution and ultrasonicated until it dissolved. The mixed solution of NaOH and ethanol was slowly dripped into the purified cotton cobalt system. Stirring was continued at room temperature for 12 hours. The purified cotton cobalt system turned from gray to dark brown. A dark brown solid catalyst semi-finished product was obtained by rotary evaporation. The catalyst was washed three times with ethanol and distilled water respectively to remove excess Ac- and impurities.

[0011] 3) Post-treatment: The semi-finished solid catalyst obtained in step 2) is placed in a vacuum drying oven and dried under reduced pressure to obtain a refined cotton-supported Co3O4 catalyst.

[0012] In one possible embodiment, the refined cotton is obtained by pulverizing refined cotton. The molecular weight of the refined cotton can be a high molecular weight with a degree of polymerization of 10,000-15,000, or a low molecular weight with a degree of polymerization of 6,000-8,000. The lower the molecular weight, the better the dispersion of the metal oxide in the prepared catalyst and the better the catalytic effect. Refined cotton with a degree of polymerization of 6,000-8,000 is preferred.

[0013] Furthermore, the mass ratio of the refined cotton to the swelling liquid is 1:12-60, preferably 1:15-40.

[0014] Furthermore, in the swelling liquid formed by mixing alkali and urea, the mass ratio of alkali, urea and water is 1:1:7 to 1:5:30.

[0015] Furthermore, in step 2), the mass ratio of gel-like purified cotton: cobalt acetate: ethanol is 1:1:5 to 1:4:9.

[0016] Furthermore, in step 2), the mass ratio of NaOH to ethanol in the mixed solution of NaOH and ethanol is 1:200 to 1:450.

[0017] Furthermore, in step 2), the mass ratio of the mixed solution of NaOH and ethanol to the refined cotton cobalt system is 1:2 to 1:5.

[0018] Furthermore, in step 3), the vacuum degree of the vacuum drying oven is 0.01 MPa to 0.1 MPa, the oven temperature is 60-70° C., and the drying time is 4-12 h.

[0019] The invention discloses a method for using a catalyst of Co3O4 immobilized on refined cotton, which is used in the field of heterogeneous catalytic organic synthesis, namely, a catalytic reaction of oxidizing olefins to epoxy compounds using oxygen or air as an oxygen source.

[0020] Furthermore, the olefin includes one or more of α-pinene, α-methylstyrene, cyclohexene, styrene, cyclooctene, β-pinene and limonene.

[0021] Furthermore, the catalyst for catalyzing the epoxidation reaction is 30-150 mg of refined cotton-supported Co3O4, 3 mmol of olefin, 10 g of DMF (N, N-dimethylformamide) solvent, 30-50 mL / min of air or oxygen flow rate, 60-95°C of reaction temperature, and 3-7 h of reaction time.

[0022] Compared with the prior art, the present invention has at least the following beneficial effects:

[0023] 1. The catalyst carrier used is refined cotton, which is abundant in source, green and environmentally friendly, has little pollution to the environment, and the process for preparing the catalyst is simple, so the catalyst cost is low.

[0024] 2. The active metal used in the catalyst is Co3O 4， The present application effectively controls the particle size of Co3O4 to the nanometer level or even the quantum dot level through the synthesis conditions, which can effectively reduce the particle size of active metals to expose more surface active sites and thus improve the activity of Co3O4.

[0025] 3. Cellulose is used as a carrier in the system. On the one hand, the natural nano-multi-level porous structure of cellulose is more conducive to the dispersion of Co3O4 in the three-dimensional space of the fiber; on the other hand, the rich characteristic functional groups (-OH, COC) on the cellulose molecular chain produce strong interactions with metal particles, thereby firmly anchoring the metal, which is advantageous for improving the stability of the catalyst.

[0026] 4. The catalyst prepared in this application has a good effect in catalyzing the epoxidation of olefins and only requires molecular oxygen as an oxygen source (air or oxygen), making the catalytic system more environmentally friendly. DETAILED DESCRIPTION

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention are clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0028] Unless expressly stated otherwise, throughout the specification and claims, the term "comprise" or variations such as "include" or "comprising", etc., will be understood to include the stated elements or components but not to exclude other elements or other components.

[0029] Any embodiment below is not necessarily to be construed as preferred or advantageous over other embodiments unless explicitly supported otherwise.

[0030] In addition, numerous specific details are provided in the following detailed description to better illustrate the present invention. Those skilled in the art will appreciate that the present invention can be practiced without certain specific details. In some instances, methods, means, and components well known to those skilled in the art are not described in detail in order to highlight the main purpose of the present invention.

[0031] Example 1:

[0032] The preparation method of the refined cotton immobilized Co3O4 catalyst comprises the following steps:

[0033] 2.0 g of sodium hydroxide and 4.0 g of urea were weighed and dissolved in 25.0 g of water to prepare a swelling solution; 2.0 g of refined cotton was added to the swelling solution for swelling treatment. Then, the mixture was frozen at -20°C for 48 hours and then thawed. The mixture was vigorously stirred at room temperature for 25 minutes, the mixture was centrifuged, the supernatant was discarded, and deionized water was added. This was repeated several times to obtain 16 grams of neutral gel-like refined cotton (solid content of about 10%). 16 g of the above-mentioned neutral gel-like refined cotton, 2.4 g of Co(Ac)2·4H2O and 8.0 g of ethanol were added to a flat-bottom flask in sequence. After stirring at room temperature for 1 hour, the mixture was ultrasonically treated at 700W for 30 minutes. 0.015 g of NaOH was then added to the 8.0 g ethanol solution and ultrasonicated until it dissolved. The NaOH ethanol solution was slowly (over 30 minutes) dripped into the above-mentioned refined cotton cobalt system. Stirring was continued at room temperature for 12 hours. The system would turn from gray to dark brown. A dark brown solid was obtained by rotary evaporation. The solid was washed three times with ethanol and distilled water respectively to remove excess Ac- and other impurities. The product was dried in a vacuum oven at 65°C for 8 hours at a vacuum pressure of 0.05 MPa to obtain a purified cotton-supported Co₃O₄ catalyst. The purified cotton-supported Co₃O₄ catalyst was used in the heterogeneous catalytic epoxidation of styrene using air as the oxygen source, 50 mg of catalyst, 3 mmol of olefin, 10 g of DMF (N,N-dimethylformamide) as the solvent, an air flow rate of 35 mL / min, a reaction temperature of 90°C, and a reaction time of 5 hours. The reaction achieved a styrene conversion of 93% and an epoxide selectivity of 95%.

[0034] Example 2

[0035] 2.0 g of sodium hydroxide and 6.5 g of urea were weighed and dissolved in 30.0 g of water to prepare a swelling solution; 2.5 g of refined cotton was added to the swelling solution for swelling treatment. Then, the mixture was frozen at -20°C for 48 h and then thawed. The mixture was vigorously stirred at room temperature for 25 min, the mixture was centrifuged, the supernatant was discarded, and deionized water was added. This was repeated several times to obtain 20 g of neutral gel-like refined cotton (solid content of about 10%). 20 g of the above-mentioned neutral gel-like cellulose, 4.8 g of Co(Ac)2·4H2O and 25.0 g of ethanol were added to a flat-bottom flask in sequence. After stirring at room temperature for 1 h, the mixture was ultrasonically treated at 700 W for 30 min. 0.05 g of NaOH was then added to the 20.0 g ethanol solution and ultrasonicated until it dissolved. The NaOH ethanol solution was slowly (over 30 min) dripped into the above-mentioned refined cotton cobalt system and stirred at room temperature for 12 h. The system turned from gray to dark brown. A dark brown solid was obtained by rotary evaporation and washed three times with ethanol and distilled water respectively to remove excess Ac- and other impurities. The material was dried in a vacuum oven at 70°C for 8 hours at a vacuum pressure of 0.01 MPa to obtain a purified cotton-supported Co₃O₄ catalyst. The purified cotton-supported Co₃O₄ catalyst was used for the heterogeneous catalytic epoxidation of α-pinene using oxygen as the oxygen source, 100 mg of catalyst, 3 mmol of olefin, 10 g of DMF (N,N-dimethylformamide) as the solvent, an oxygen flow rate of 30 mL / min, a reaction temperature of 90°C, and a reaction time of 6 hours. The results showed a 90% conversion of α-pinene and a 93% selectivity for epoxides.

[0036] Example 3

[0037] 3.0 g of sodium hydroxide and 9.0 g of urea were weighed and dissolved in 45.0 g of water to prepare a swelling solution; 3.5 g of refined cotton was added to the swelling solution for swelling treatment. The mixture was then frozen at -20°C for 48 hours, thawed, and vigorously stirred at room temperature for 25 minutes. The mixture was centrifuged, the supernatant discarded, and deionized water added. This process was repeated several times to obtain 30 g of neutral gel-like purified cotton (solid content approximately 10%). The above neutral gel-like purified cotton, 6.0 g of Co(Ac)2·4H2O, and 40.0 g of ethanol were added to a flat-bottom flask, stirred at room temperature for 1 hour, and then sonicated for 30 minutes. 0.03 g of NaOH was then added to 15.0 g of the ethanol solution and sonicated until dissolved. The NaOH ethanol solution was then slowly added dropwise (over 30 minutes) to the purified cotton-cobalt system. Stirring was continued at room temperature for 12 hours. The system turned from gray to dark brown. Rotary evaporation yielded a dark brown solid, which was washed three times with ethanol and then with distilled water to remove excess Ac- and other impurities. The solid was then dried in a vacuum oven at 0.01 MPa and 68°C for 6 hours to obtain the purified cotton-supported Co3O4 catalyst. A refined cotton catalyst immobilized with Co₃O₄ was used for the heterogeneous catalytic epoxidation of α-pinene. Air was used as the oxygen source, the catalyst was 80 mg, the olefin was 3 mmol, the solvent was DMF (N, N-dimethylformamide) 10 g, the air flow rate was 35 mL / min, the reaction temperature was 95°C, and the reaction time was 5 h. The α-pinene conversion rate could reach 88%, and the selectivity for the epoxide compound could reach 90%.

[0038] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for preparing a catalyst comprising: preparing a catalyst comprising: a purified cotton-supported Co3O4 catalyst for catalytically oxidizing olefins to epoxides using oxygen or air as an oxygen source; The preparation method of the catalyst comprises the following steps: 1) Pretreatment: Add refined cotton to a swelling solution formed by mixing alkali and urea for 30 minutes, then freeze at -20°C for 48 hours before thawing. Stir vigorously at room temperature for 25 minutes, centrifuge the mixed solution, discard the supernatant, and add deionized water. Repeat this process several times to obtain a neutral gel-like refined cotton with a solid content of 10%. 2) Immobilized Co3O4: The neutral gel-like purified cotton, cobalt acetate, and ethanol were sequentially added to a flat-bottomed flask. After stirring at room temperature for 1 hour, the mixture was ultrasonically treated at 700W for 30 minutes to form a purified cotton cobalt system. NaOH was then added to the ethanol solution and ultrasonicated until it dissolved. The mixed solution of NaOH and ethanol was slowly dripped into the purified cotton cobalt system. Stirring was continued at room temperature for 12 hours. The purified cotton cobalt system turned from gray to dark brown. The dark brown solid catalyst semi-finished product was obtained by rotary evaporation. The semi-finished product was washed with ethanol and distilled water three times each to remove impurities. 3) Post-treatment: The semi-finished solid catalyst obtained in step 2) is placed in a vacuum drying oven and dried under reduced pressure to obtain a refined cotton-supported Co3O4 catalyst.

2. The use according to claim 1, characterized in that In the step 1), the mass ratio of the refined cotton to the swelling liquid is 1:12-60.

3. The use according to claim 1, characterized in that: In step 2), the mass ratio of NaOH to ethanol in the mixed solution of NaOH and ethanol is 1:200 to 1:

450.

4. The use according to claim 1, characterized in that: In the step 2), the mass ratio of the mixed solution of NaOH and ethanol to the refined cotton cobalt system is 1:2 to 1:

5.

5. The use according to claim 1, characterized in that: In step 3), the vacuum degree of the vacuum drying oven is 0.01 MPa to 0.1 MPa, the oven temperature is 60-70° C., and the drying time is 4-12 h.

6. The use according to claim 1, characterized in that The olefins include one or more of α-pinene, α-methylstyrene, cyclohexene, styrene, cyclooctene, β-pinene and limonene.

7. The use according to claim 1, characterized in that The catalyst of Co3O4 supported on refined cotton for catalytic epoxidation reaction is 30-150 mg, the olefin is 3 mmol; the solvent DMF is 10 g; the air flow rate or oxygen flow rate is 30-50 mL / min; the reaction temperature is 60-95°C; and the reaction time is 3-7 hours.