CN115785037A - Green synthesis method for preparing 2, 5-furandicarboxylic acid by catalyzing tandem oxidation of 5-hydroxymethylfurfural - Google Patents

Abstract

The invention belongs to the technical field of organic synthesis, and specifically relates to a green synthesis method for preparing 2,5-furandicarboxylic acid by catalyzing the series oxidation of 5-hydroxymethylfurfural. HMF, a reaction medium, TBHP and C@CoMn are added to the reaction In the container, stir the oxidation reaction to obtain FDCA; C@CoMn is the catalyst, and the porous carbon on the outer layer of the catalyst is rich in pyridinic nitrogen, pyrrole nitrogen and graphitic nitrogen. Basic sites promote HMF to form readily oxidizable gem-diol intermediates, At the same time, the bimetallic catalyst has abundant oxygen vacancies and Mn ³⁺ can activate TBHP to form highly active superoxide radicals. The invention overcomes the low selectivity of the HMF oxidation process and the environmental pollution caused by the use of alkaline reagents, and promotes the generation of superoxide free radicals that are beneficial to the oxidation reaction through the regulation of the Lewis base site of C@CoMn and the active species of manganese. Realize efficient and highly selective conversion of HMF to FDCA under a mild environment, and have industrial application prospects.

Description

A method for catalyzing the tandem oxidation of 5-hydroxymethylfurfural to prepare 2,5-furandicarboxylic acid Green Synthesis Method

technical field

The invention belongs to the technical field of organic synthesis, and in particular relates to a green synthesis method for catalyzing the serial oxidation of 5-hydroxymethylfurfural to prepare 2,5-furandicarboxylic acid.

Background technique

With the increasing consumption of fossil energy and global warming caused by the greenhouse effect, the development and utilization of sustainable energy has been greatly promoted. If the abundant biomass resources in nature can be converted into high value-added chemicals through the development of new catalytic reaction technologies, this will alleviate the current energy and environmental crisis. 5-Hydroxymethylfurfural (HMF) is a versatile compound that can be obtained by hydrolysis of cellulose. HMF can be synthesized into high value-added chemicals through catalytic oxidation, such as 2,5-furandicarbaldehyde (DFF), 2,5-furandicarboxylic acid (FDCA), 5-hydroxymethyl-2-furanoic acid (HMFCA), horse to acid (MA) and so on. Among them, FDCA is considered to be the key monomer with the most market potential and an important monomer for the production of green polymer polyethylene 2,5-furandicarboxylate. Therefore, using 5-hydroxymethylfurfural (HMF) as a platform compound to prepare FDCA through multi-step oxidation through green catalytic technology is of great significance for the development of green chemical routes for the synthesis of bio-based chemicals to replace traditional petrochemical products. .

To develop environmentally friendly epoxidation technology, it is very important to use green molecular oxygen (O ₂ ), hydrogen peroxide (H ₂ O ₂ ) and tert-butyl hydroperoxide (TBHP) as oxidants. Compared with O ₂ activation that requires noble metals or photosensitizers, H ₂ O ₂ and TBHP can use molecular sieves, transition metals, carbon materials, etc. as catalysts to realize the conversion of HMF. The disadvantage of _H2O2 and _TBHP as oxidizing agents is the low selectivity of FDCA. This is because H ₂ O ₂ and TBHP will simultaneously form superoxide radicals (HO ₂ ·) and hydroxyl radicals (·OH) during the activation process, and ·OH is easy to cause side reactions and reduce the reaction selectivity. In order to improve the selectivity of FDCA, the conversion of HMF to FDCA was promoted by additionally adding alkali (such as _NaHCO3, etc.) in the reaction solution. However, the addition of alkali brings inconvenience to the subsequent separation and purification, and also causes environmental pollution. The oxidation of HMF can also be catalyzed by utilizing the solid base catalytic sites of the material itself without additional base addition. Compared with transition metal catalysts, non-metal catalysts are cheaper, and the process of disposal and recycling is environmentally friendly. In the catalytic oxidation reaction of HMF, non-metallic catalysts based on carbon and nitrogen show excellent performance. For example, nitrogen-doped carbon materials have the advantages of simple preparation process, low cost, and good catalytic performance. The doping of N atoms can form porous carbons containing pyridinic nitrogen, pyrrolic nitrogen, and graphitic nitrogen basic sites due to the formation of these basic sites. At the same time, the N site can activate TBHP to form superoxide radical HO ₂ ·, and promote the efficient and selective conversion of HMF into FDCA.

Therefore, there is an urgent need to provide a new green synthetic method for the preparation of 2,5-furandicarboxylic acid, which can achieve efficient and highly selective conversion of HMF.

Contents of the invention

The purpose of the present invention is to overcome the above-mentioned problems existing in the traditional technology, and to provide a green synthesis method for preparing 2,5-furandicarboxylic acid by catalyzing the series oxidation of 5-hydroxymethylfurfural, which can realize the high efficiency and high selectivity of HMF transform.

In order to achieve the above-mentioned technical purpose and achieve the above-mentioned technical effect, the present invention is realized through the following technical solutions:

A green synthesis method for catalyzing the serial oxidation of 5-hydroxymethylfurfural to prepare 2,5-furandicarboxylic acid, which is characterized in that HMF, reaction medium, TBHP and C@CoMn are added to a reaction vessel and stirred for oxidation Reaction, get FDCA.

Further, the preparation method of the C@CoMn includes the following steps:

1) dissolving polyoxyethylene polyoxypropylene ether and dopamine hydrochloride in a water-ethanol mixed solution according to the ratio, adding manganese salt and cobalt salt under stirring conditions to obtain a solution;

2) adding ammonia water to solution A, stirring and reacting to obtain a catalyst precursor;

3) Calcining the obtained catalyst precursor in an air atmosphere at 330-370° C. for 2-6 hours to obtain C@CoMn.

Further, in step 1), the molar ratio of polyoxyethylene polyoxypropylene ether, dopamine hydrochloride, manganese salt, and cobalt salt is 1:60-65:50-55:60-65;

Described manganese salt is manganese nitrate tetrahydrate, manganese acetate dihydrate, manganese sulfate monohydrate or manganese carbonate;

The cobalt salt is cobalt nitrate tetrahydrate, cobalt carbonate, cobalt sulfate or cobalt acetate;

Water and ethanol are mixed in any proportion in the water-ethanol mixed solution.

Further, in step 2), the mass fraction of the ammonia water is 25-28%, and the ratio of the ammonia water to polyoxyethylene polyoxypropylene ether is 3-5ml/g.

Further, in step 3), the temperature of calcination is 350° C., and the time is 4 hours.

Further, the concentration of the added C@CoMn is 30-35 g/L.

Further, the concentration of the added HMF is 0.15-0.2 mol/L.

Further, the molar amount of TBHP is 3-6 times that of HMF.

Further, the reaction medium is any one of toluene, acetonitrile, tetrahydrofuran, and 1,4-dioxane.

Further, the reaction temperature is controlled at 60-75° C., and the reaction time is controlled at 5-7 hours.

The beneficial effects of the present invention are:

1. The present invention provides a green synthesis method for catalyzing the serial oxidation of 5-hydroxymethylfurfural to prepare 2,5-furandicarboxylic acid. HMF, reaction medium, oxidant TBHP and catalyst C@CoMn are added to the reaction tube Mix evenly, carry out oxidation reaction, obtain FDCA. In the present invention, C@CoMn is used as a catalyst. The porous carbon in the outer layer of the catalyst is rich in pyridinic nitrogen, pyrrole nitrogen and graphitic nitrogen basic sites to promote HMF to form easily oxidizable gem-diol intermediates, and the bimetallic catalyst has abundant oxygen vacancies. And Mn ³⁺ can activate TBHP to form highly active superoxide radicals, and realize the efficient and high-selective conversion of HMF to FDCA in a mild environment, which has industrial application prospects.

2. The catalytic reaction system adopted in the present invention is simple and easy to operate, does not need to add additional alkaline reagents to improve the selectivity of the product, and can realize high-efficiency conversion of HMF at a relatively low temperature. The preparation conditions of the catalyst are simple, the reaction process is green, and the environmental pollution problem caused by the use of alkaline reagents is avoided.

Of course, implementing any product of the present invention does not necessarily need to achieve all the above advantages at the same time.

Description of drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the accompanying drawings that are required for the description of the embodiments. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. Those of ordinary skill in the art can also obtain other drawings based on these drawings without any creative effort.

Figure 1 is the XRD spectrum of the C@CoMn catalyst;

Figure 2 is the O1s XPS spectrum of the C@CoMn catalyst;

Figure 3 is the EPR diagram of C@CoMn activating TBHP to form HO ₂ ·;

Fig. 4 is the ¹ H NMR spectrogram of the prepared FDCA;

Figure 5 is a schematic diagram of the HMF oxidation reaction.

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

The invention uses dopamine hydrochloride as a nitrogen source and a carbon source, adds cobalt and manganese ions, and prepares a coated bimetallic catalyst precursor in one step through a polymerization method. The carbon-coated bimetallic catalyst C@CoMn was obtained by high-temperature calcination. Using TBHP as the oxidant, without the participation of alkaline additives, the efficient conversion of HMF to FDCA was achieved with a stable, cheap and environmentally friendly carbon-based catalyst. This process is a green and pollution-free chemical process, which is in line with the strategic goal of green and sustainable development promoted by the country.

In the present invention, the HMF oxidation reaction is shown in FIG. 5 . After completing the HMF oxidation reaction, the present invention preferably centrifuges the obtained reaction liquid to recover the catalyst, and evaporates the obtained oil phase liquid to obtain FDCA. The processes of centrifugation, evaporation and filtration are not particularly limited, and can be performed according to processes well known in the art.

In the present invention, C@CoMn is used as a catalyst. The porous carbon in the outer layer of the catalyst is rich in pyridinic nitrogen, pyrrole nitrogen and graphitic nitrogen basic sites to promote HMF to form easily oxidizable gem-diol intermediates, and the bimetallic catalyst has abundant oxygen vacancies. And Mn ³⁺ can activate TBHP to form highly active superoxide radicals, and realize the efficient and selective conversion of HMF to FDCA in a mild environment.

Relevant specific embodiments of the present invention are:

In the following examples, the preparation method of C@CoMn is: dissolve 1g polyoxyethylene polyoxypropylene ether (molecular weight 12600), 1g dopamine hydrochloride in 100mL water-ethanol (volume ratio 1:1) mixed solution, add 4mmol Manganese nitrate tetrahydrate and 5mmol cobalt nitrate tetrahydrate. 4 mL of ammonia water (26% by mass) was added to the solution, and stirred for 24 hours to obtain a catalyst precursor. The obtained catalyst precursor was placed in a muffle furnace and calcined at 350 °C for 4 h in an air atmosphere to obtain a C@CoMn catalyst.

The XRD results of C@CoMn catalyst are shown in Figure 1, the O1s XPS results of C@CoMn catalyst are shown in Figure 2, and the results of C@CoMn activation of TBHP to form HO ₂ are shown in Figure 3.

Example 1

5-Hydroxymethylfurfural HMF (0.5 mmol), acetonitrile (5 mL), oxidant TBHP (2.5 mmol) and catalyst C@CoMn (0.1 g) were added into the reaction tube. The reaction temperature was 70° C., and the reaction was stirred at 800 rpm for 5 h. After the reaction, the target product FDCA was obtained by separation and purification. HMF conversion was >99.9% with a selectivity of 94%.

The ¹ H NMR of the prepared FDCA is shown in Figure 4:

¹ H NMR (400MHz, CDCl ₃ )δ7.54,7.28,7.16,7.02,5.60,4.22,4.18,2.38,2.30,2.28,1.56,1.45,1.39,1.36,1.31,1.28,1.05,0.90,0.88,0.87 ,0.17,0.02,-0.13.

Example 2

5-Hydroxymethylfurfural HMF (0.5 mmol), acetonitrile (4.5 mL), oxidant TBHP (3.2 mmol), and catalyst C@CoMn (0.12 g) were added into the reaction tube. The reaction temperature was 70° C., and the reaction was stirred at 800 rpm for 5 h. After the reaction, the target product FDCA was obtained by separation and purification. HMF conversion was >99.9% with a selectivity of 89%.

Example 3

5-Hydroxymethylfurfural HMF (0.5 mmol), acetonitrile (5.5 mL), oxidant TBHP (2 mmol), and catalyst C@CoMn (0.06 g) were added into the reaction tube. The reaction temperature was 70° C., and the reaction was stirred at 800 rpm for 5 h. After the reaction, the target product FDCA was obtained by separation and purification. HMF conversion was 90% with a selectivity of 87%.

Example 4

5-Hydroxymethylfurfural HMF (0.5 mmol), acetonitrile (5 mL), oxidant TBHP (2.5 mmol) and catalyst C@CoMn (0.1 g) were added into the reaction tube. The reaction temperature was 60° C., and the reaction was stirred at 800 rpm for 5 h. After the reaction, the target product FDCA was obtained by separation and purification. HMF conversion was 90% with a selectivity of 90%.

Example 5

5-Hydroxymethylfurfural HMF (0.5 mmol), acetonitrile (5 mL), oxidant TBHP (2.5 mmol) and catalyst C@CoMn (0.1 g) were added into the reaction tube. The reaction temperature was 75° C., and the reaction was stirred at 800 rpm for 5 h. After the reaction, the target product FDCA was obtained by separation and purification. HMF conversion was 90% with a selectivity of 85%.

Example 6

5-Hydroxymethylfurfural HMF (0.5 mmol), acetonitrile (5 mL), oxidant TBHP (2.5 mmol) and catalyst C@CoMn (0.1 g) were added into the reaction tube. The reaction temperature was 70° C., and the reaction was stirred at 500 rpm for 5 h. After the reaction, the target product FDCA was obtained by separation and purification. The conversion of HMF was 88.2%, and the selectivity was 91%.

Example 7

5-Hydroxymethylfurfural HMF (0.5 mmol), acetonitrile (5 mL), oxidant TBHP (2.5 mmol) and catalyst C@CoMn (0.1 g) were added into the reaction tube. The reaction temperature was 70° C., and the reaction was stirred at 1200 rpm for 5 h. After the reaction, the target product FDCA was obtained by separation and purification. The conversion of HMF was 98%, and the selectivity was 91.5%.

Example 8

5-Hydroxymethylfurfural HMF (0.5 mmol), acetonitrile (5 mL), oxidant TBHP (2.5 mmol) and catalyst C@CoMn (0.1 g) were added into the reaction tube. The reaction temperature was 70° C., and the reaction was stirred at 800 rpm for 3 h. After the reaction, the target product FDCA was obtained by separation and purification. HMF conversion was 65% with a selectivity of 80%.

Example 9

5-Hydroxymethylfurfural HMF (0.5 mmol), acetonitrile (5 mL), oxidant TBHP (2.5 mmol) and catalyst C@CoMn (0.1 g) were added into the reaction tube. The reaction temperature was 70° C., and the reaction was stirred at 800 rpm for 6 hours. After the reaction, the target product FDCA was obtained by separation and purification. HMF conversion was >99.9% with a selectivity of 92%.

Example 10

5-Hydroxymethylfurfural HMF (0.5 mmol), toluene (5 mL), oxidant TBHP (2.5 mmol) and catalyst C@CoMn (0.1 g) were added into the reaction tube. The reaction temperature was 70° C., and the reaction was stirred at 800 rpm for 6 hours. After the reaction, the target product FDCA was obtained by separation and purification. The HMF conversion was 90% with a selectivity of 86%.

Example 11

5-Hydroxymethylfurfural HMF (0.5 mmol), tetrahydrofuran (5 mL), oxidant TBHP (2.5 mmol), and catalyst C@CoMn (0.1 g) were added into the reaction tube. The reaction temperature was 70° C., and the reaction was stirred at 800 rpm for 6 hours. After the reaction, the target product FDCA was obtained by separation and purification. The conversion of HMF was 90.9%, and the selectivity was 83%.

Example 12

5-Hydroxymethylfurfural HMF (0.5 mmol), 1,4-dioxane (5 mL), oxidant TBHP (2.5 mmol), and catalyst C@CoMn (0.1 g) were added into the reaction tube. The reaction temperature was 70° C., and the reaction was stirred at 800 rpm for 6 hours. After the reaction, the target product FDCA was obtained by separation and purification. HMF conversion was 95% with a selectivity of 80%.

The invention overcomes the low selectivity of the HMF oxidation process and the environmental pollution caused by the use of alkaline reagents, and promotes the generation of superoxide free radicals that are beneficial to the oxidation reaction through the regulation of the Lewis base site of C@CoMn and the active species of manganese. Realize efficient and highly selective conversion of HMF to FDCA under mild environment, and have industrial application prospects.

The preferred embodiments of the invention disclosed above are only to help illustrate the invention. The preferred embodiments do not exhaust all details nor limit the invention to specific implementations. Obviously, many modifications and variations can be made based on the contents of this specification. This description selects and specifically describes these embodiments in order to better explain the principle and practical application of the present invention, so that those skilled in the art can well understand and utilize the present invention. The invention is to be limited only by the claims, along with their full scope and equivalents.

Claims (10)

1. A green synthesis method for preparing 2,5-furandicarboxylic acid by catalyzing the series oxidation of 5-hydroxymethylfurfural, characterized in that HMF, reaction medium, TBHP and C@CoMn are added to the reaction vessel, stirred Oxidation reaction is carried out to obtain FDCA. 2. The green synthesis method according to claim 1, wherein the preparation method of the C@CoMn comprises the following steps: 1) dissolving polyoxyethylene polyoxypropylene ether and dopamine hydrochloride in a water-ethanol mixed solution according to the ratio, adding manganese salt and cobalt salt under stirring conditions to obtain a solution; 2) adding ammonia water to solution A, stirring and reacting to obtain a catalyst precursor; 3) Calcining the obtained catalyst precursor in an air atmosphere at 330-370° C. for 2-6 hours to obtain C@CoMn. 3. The green synthesis method according to claim 2, characterized in that, in step 1), the molar ratio of the polyoxyethylene polyoxypropylene ether, dopamine hydrochloride, manganese salt, and cobalt salt is 1:60 to 65: 50～55: 60～65; Described manganese salt is manganese nitrate tetrahydrate, manganese acetate dihydrate, manganese sulfate monohydrate or manganese carbonate; The cobalt salt is cobalt nitrate tetrahydrate, cobalt carbonate, cobalt sulfate or cobalt acetate; Water and ethanol are mixed in any proportion in the water-ethanol mixed solution. 4. The green synthesis method according to claim 2, characterized in that, in step 2), the mass fraction of the ammoniacal liquor is 25 to 28%, and the volume of the ammoniacal liquor and the molar weight of polyoxyethylene polyoxypropylene ether The proportioning relationship is 6-10ml/mol. 5. The green synthesis method according to claim 2, characterized in that, in step 3), the temperature of calcination is 350° C., and the time is 4 hours. 6. The green synthesis method according to claim 1, characterized in that the concentration of the C@CoMn added is 30-35 g/L. 7. The green synthesis method according to claim 1, characterized in that the concentration of the added HMF is 0.15-0.2 mol/L. 8. The green synthesis method according to claim 1, characterized in that the molar weight of TBHP is 3 to 6 times that of HMF. 9. The green synthesis method according to claim 1, wherein the reaction medium is any one of toluene, acetonitrile, tetrahydrofuran, and 1,4-dioxane. 10. The green synthesis method according to claim 1, characterized in that the reaction temperature is controlled at 60-75° C., and the reaction time is controlled at 5-7 hours.

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