Method for preparing formic acid from MOF-derived porous carbon composite manganese oxide catalyst

Abstract

The invention provides a method for preparing formic acid from an MOF-derived porous carbon composite manganese oxide catalyst. The method comprises the following steps: preparing a manganese MOF precursor; carbonizing the MOF precursor to obtain an MOF-derived carbon composite manganese oxide; the MOF-derived carbon composite manganese oxide is used as a catalyst, monosaccharide is catalyzed in a water environment for an oxidation reaction, and formic acid is obtained. According to the method for preparing formic acid by using the MOF-derived porous carbon composite manganese oxide catalyst provided by the invention, the MOF-derived carbon composite manganese oxide is prepared, and the MOF-derived carbon composite manganese oxide is used as the catalyst to prepare formic acid, so that the steps are simple, the efficiency of converting monosaccharide into formic acid can be effectively improved, and the method is higher in safety and environment-friendly.

Description

Technical Field

[0001] The present application relates to the technical field of catalytic synthesis, and in particular to a method for preparing formic acid using a MOF-derived porous carbon composite manganese oxide catalyst. Background Art

[0002] Formic acid is a commonly used reducing agent with a simple structure but strong acidity. It is an important organic chemical raw material and is widely used in industries such as chemical, agriculture, textile, leather, pharmaceutical and rubber. It is also an important food additive used to increase the shelf life of food. Due to its high net capacity at ambient temperature and its simplicity and cleanness, formic acid is considered to be one of the most promising hydrogen storage materials today. The most commonly used method for producing formic acid in industry is the hydrolysis of methyl formate, but the raw materials of this method are derivatives of non-renewable resources. It is very necessary to develop a greener formic acid production system. Lignocellulose has the characteristics of a wide range of sources and rich substances. The main components of lignin cellulose, cellulose and hemicellulose, and their derivative sugars have great potential for conversion into formic acid. At present, the research on the production of formic acid using the above components as raw materials mainly focuses on homogeneous catalytic systems represented by vanadium-containing catalysts, but this system has the characteristics of high biological toxicity and poor environmental friendliness, and homogeneous catalysts are difficult to recycle. Summary of the invention

[0003] The purpose of the present application is to provide a method for preparing formic acid using a MOF-derived porous carbon composite manganese oxide catalyst, which can effectively improve the efficiency and safety of formic acid preparation.

[0004] In a first aspect, the present application provides a method for preparing formic acid using a MOF-derived porous carbon composite manganese oxide catalyst, comprising:

[0005] Preparation of manganese MOF precursor;

[0006] Carbonizing the MOF precursor to obtain a MOF-derived carbon-composite manganese oxide;

[0007] The carbon-composite manganese oxide derived from the MOF is used as a catalyst to catalyze an oxidation reaction of monosaccharides in a water environment to obtain formic acid.

[0008] In some possible embodiments, the preparation of a manganese MOF precursor comprises:

[0009] Dissolving a manganese source and a complexing agent in corresponding solvents respectively to obtain a manganese solution and a complexing agent solution;

[0010] Stirring the manganese solution and the complexing agent solution separately, and adding the manganese solution and the complexing agent solution into a reaction kettle under stirring to obtain a reaction solution;

[0011] Controlling the temperature of the reactor to a preset temperature range, and controlling the reaction liquid to react for a preset time within the preset temperature range;

[0012] The reaction solution after the reaction is centrifuged and dried to obtain the manganese MOF precursor.

[0013] In some possible embodiments, the manganese source is a manganese salt.

[0014] In some possible embodiments, the manganese salt includes one or more of KMnO4, Mn(NO3)2, (CH3COO)2Mn, MnCl2, and MnSO4.

[0015] In some possible embodiments, the complexing agent includes one or more of tribenzoic acid, 2.5-dihydroxyterephthalic acid, 2-methylimidazole, terephthalic acid, and imidazole.

[0016] In some possible embodiments, the molar ratio of the manganese source to the complexing agent is 1:1-9:1.

[0017] In some possible embodiments, the carbonization temperature for carbonizing the MOF precursor is 200-1000° C., the heating rate is 1-10° C. / min, and the carbonization time is 2-5 hours.

[0018] In some possible embodiments, the mass ratio of the monosaccharide to the manganese oxide is 1:(0.1-1), and the volume ratio of the monosaccharide to the water is 1 mg:(0.025-0.1) mL.

[0019] In some possible embodiments, the reaction pressure of the oxidation reaction is 0.5-4 MPa, the reaction temperature is 140-180° C., and the reaction time is 15-360 min.

[0020] In a second aspect, an embodiment of the present application provides formic acid, which is prepared by the method for preparing formic acid using a MOF-derived porous carbon composite manganese oxide catalyst as described in any one of the above items.

[0021] The present application provides a method for preparing formic acid using a MOF-derived porous carbon-composite manganese oxide catalyst, comprising: preparing a manganese MOF precursor; carbonizing the MOF precursor to obtain a MOF-derived carbon-composite manganese oxide; using the MOF-derived carbon-composite manganese oxide as a catalyst to catalyze an oxidation reaction of monosaccharides in an aqueous environment to obtain formic acid. The method for preparing formic acid using a MOF-derived porous carbon-composite manganese oxide catalyst provided in the present application, by preparing a MOF-derived carbon-composite manganese oxide, and using the MOF-derived carbon-composite manganese oxide as a catalyst to prepare formic acid, has simple steps, can effectively improve the efficiency of converting monosaccharides into formic acid, and has higher safety and is environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The technical solution and other beneficial effects of the present application will be made apparent by describing in detail the specific implementation methods of the present application in conjunction with the accompanying drawings.

[0023] Figure 1 It is a schematic flow chart of a method for preparing formic acid using a MOF-derived porous carbon composite manganese oxide catalyst provided in an embodiment of the present application;

[0024] Figure 2 It is a schematic diagram of the process of preparing a MOF precursor of manganese oxide provided in an embodiment of the present application;

[0025] Figure 3 XRD spectra of Examples 1 and 2 of the present application;

[0026] Figure 4 TEM spectra of carbon composite manganese oxide catalysts 1 and 2 prepared in the examples of the present application;

[0027] Figure 5 The monosaccharide conversion rate and formic acid yield of the carbon composite manganese oxide catalyst prepared in Example 1 and Example 2 provided in the examples of the present application;

[0028] Figure 6 HPLC chromatograms of Examples 1 and 2 provided in this application. DETAILED DESCRIPTION

[0029] The present application is further described in detail below in conjunction with the accompanying drawings and examples. It is particularly noted that the following examples are only used to illustrate the present application, but are not intended to limit the scope of the present application. Similarly, the following examples are only some embodiments of the present application rather than all embodiments, and all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of this application.

[0030] In the following description of the present application, reference is made to “some embodiments”, which describe a subset of all possible embodiments, but it can be understood that “some embodiments” may be the same subset or different subsets of all possible embodiments and may be combined with each other without conflict.

[0031] In the following description of the present application, the terms "first\second\third" involved are merely used to distinguish similar objects and do not represent a specific ordering of the objects. It can be understood that "first\second\third" can be interchanged with a specific order or sequence where permitted, so that the embodiments of the present application described here can be implemented in an order other than that illustrated or described here.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein are only for the purpose of describing the embodiments of this application and are not intended to limit this application.

[0033] The following is a detailed description with reference to specific embodiments. It should be noted that the serial numbers of the following embodiments are not intended to limit the preferred order of the embodiments.

[0034] The present application discloses a method for preparing formic acid using a MOF-derived porous carbon composite manganese oxide catalyst. The method uses carbon composite manganese oxide as a catalyst to prepare formic acid, which is described in detail below.

[0035] See also Figure 1 , Figure 1 : is a schematic flow chart of a method for preparing formic acid using a MOF-derived porous carbon composite manganese oxide catalyst provided in an embodiment of the present application. The specific flow chart of the method for preparing formic acid using a MOF-derived porous carbon composite manganese oxide catalyst can be as follows:

[0036] 101. Prepare manganese MOF precursor.

[0037] 101. Carbonizing the MOF precursor to obtain MOF-derived carbon-composite manganese oxide.

[0038] 102. Using MOF-derived carbon-complexed manganese oxide as a catalyst, monosaccharides are catalyzed for oxidation reaction in an aqueous environment to produce formic acid.

[0039] The present application provides a method for preparing formic acid using a MOF-derived porous carbon-composite manganese oxide catalyst, comprising: preparing a manganese MOF precursor; carbonizing the MOF precursor to obtain a MOF-derived carbon-composite manganese oxide; using the MOF-derived carbon-composite manganese oxide as a catalyst to catalyze an oxidation reaction of monosaccharides in an aqueous environment to obtain formic acid. The method for preparing formic acid using a MOF-derived porous carbon-composite manganese oxide catalyst provided in the present application, by preparing a MOF-derived carbon-composite manganese oxide, and using the MOF-derived carbon-composite manganese oxide as a catalyst to prepare formic acid, has simple steps, can effectively improve the efficiency of converting monosaccharides into formic acid, and has higher safety and is environmentally friendly.

[0040] Among them, MOF (Metal organic Framework) is the abbreviation of metal organic framework compounds; it is a type of crystalline porous material with a periodic network structure formed by the self-assembly of inorganic metal centers (metal ions or metal clusters) and bridging organic ligands, which has the rigidity of inorganic materials and the flexibility of organic materials. This application first prepares a manganese MOF precursor, and further prepares a carbon-composite manganese oxide derived from MOF, and finally uses the carbon-composite manganese oxide derived from MOF as a catalyst to prepare formic acid.

[0041] In some embodiments, preparing a MOF precursor of manganese oxide may include the following steps:

[0042] 201. Dissolve the manganese source and the ligand in corresponding solvents to obtain a manganese solution and a ligand solution.

[0043] 202. Stir the manganese solution and the complexing agent solution separately, and add the manganese solution and the complexing agent solution into the reaction kettle under stirring to obtain a reaction solution.

[0044] 203. Control the temperature of the reactor to a preset temperature range, and control the reaction liquid to react for a preset time within the preset temperature range.

[0045] 203. The reaction solution after the reaction is centrifuged and dried to obtain a manganese MOF precursor.

[0046] In the embodiments of the present application, manganese oxide is prepared as a catalyst for subsequent reactions, and first a manganese-containing solution needs to be prepared; specifically, a manganese source can be dissolved in a solvent to obtain a manganese solution. In the present application, a ligand solution needs to be prepared; wherein the ligand can achieve coordination to obtain a MOF precursor. After the manganese solution and the ligand solution are prepared respectively, the two can be added to a reactor and mixed under a rotating stirring state to obtain a reaction solution; the manganese solution and the ligand in the reaction solution will undergo a chemical reaction to obtain a corresponding reaction product, and the reaction product will undergo a crystal growth process to generate a manganese MOF precursor. After the reaction is preset for a certain period of time, the reaction solution can be subjected to processes such as centrifugal drying to extract crystals from the reaction solution, and the extracted crystals are manganese MOF precursors. It should be noted that the manganese solution and the ligand solution are chemically reacted to obtain only a MOF precursor having a manganese element, and the manganese element at this time does not exist in the form of manganese oxide. After obtaining the precursor, the precursor needs to be further processed to obtain a porous carbon composite manganese oxide. In some embodiments, the precursor may be carbonized to obtain a carbon-composite manganese oxide, which has a porous carbon-composite structure and can thus be used as a catalyst to improve reaction speed and reaction efficiency.

[0047] In the above embodiment, the manganese source can be a manganese salt; more specifically, it can be a mixture of one or more of KMnO4, Mn(NO3)2, (CH3COO)2Mn, MnCl2, and MnSO4. The ligand can include one or more of tribenzoic acid, 2.5-dihydroxyterephthalic acid, 2-methylimidazole, terephthalic acid, and imidazole. In an embodiment of the present application, the molar ratio of the manganese source to the ligand is 1:1-9:1, and more preferably, the molar ratio of the manganese source to the ligand is 1:1-6:1. In some embodiments, the concentration of the manganese solution can be 0.01-0.1mol / L, and the concentration of the ligand is 0.01-0.1mol / L. Preferably, the concentration of the manganese solution can be 0.02-0.08mol / L, and the concentration of the ligand can be 0.01-0.05mol / L.

[0048] After the manganese solution and the ligand solution are mixed to obtain a reaction solution, a crystal formation process will be carried out in the reaction solution to obtain a MOF precursor of manganese oxide. In this process, the reaction solution can be stirred first to fully mix the manganese solution and the ligand solution, such as controlling the stirring rate to 200-1000rpm; more specifically, the stirring rate can be controlled to 250-800rpm; further, the stirring rate can be controlled to 300-600rpm. After the two are fully mixed, it is also necessary to control the temperature of the reactor to allow the two to react chemically, and control the temperature of the reaction solution at 30-200℃; specifically, the crystal growth temperature can be controlled to 50-180℃; further, the crystal growth temperature can be controlled to 80-150℃. It should be noted that in the aforementioned embodiment, only the manganese solution and the ligand solution are mixed, and the two will not react chemically. It is also necessary to ensure the reaction temperature and other conditions before the two will react chemically. After the reaction continues for a preset time, such as 24 hours, the crystals need to be separated from the reaction solution. In the embodiment of the present application, the reaction solution can be centrifuged and dried to obtain a manganese MOF precursor. In some embodiments, the speed during centrifugation can be 6000-12000r / min; more specifically, the centrifugal speed can be controlled to be 6500-10000r / min. The centrifugal time can be 5-10min; more specifically, the centrifugal time can be 5-8min. The drying temperature can be 60-120°C; more specifically, it can be 60-100°C; more preferably, it can be 60-80°C. The drying time can be 6-24h; more preferably, the drying time can be 6-12h. In the embodiments of the present application, the relevant parameters during centrifugal drying can be selected according to actual needs, and no limitation is made here.

[0049] After centrifugal drying, a manganese MOF precursor can be obtained. In this application, the precursor needs to be further carbonized to obtain the final MOF-derived porous carbon composite manganese oxide. Specifically, the step of carbonizing the precursor may include: calcining the MOF precursor under different atmospheres to obtain a MOF-derived porous carbon composite manganese oxide. The specific calcination process can refer to the prior art and is not limited here.

[0050] In the above embodiment, the carbonization temperature of the precursor is 200-1000° C., the heating rate is 1-10° C. / min, and the carbonization time is 2-5 hours.

[0051] The MOF-derived porous carbon composite manganese oxide catalyst prepared in this application is for the further preparation of formic acid; specifically, the MOF-derived carbon composite manganese oxide can be used as a catalyst to catalyze the oxidation reaction of monosaccharides in an aqueous environment to prepare formic acid. Among them, the mass ratio of monosaccharide to MOF-derived carbon composite manganese oxide is 1: (0.1-1), and the volume ratio of the mass of monosaccharide to water is 1mg: (0.025-0.1)mL. The reaction pressure during the oxidation reaction can be 0.5-4MPa, the reaction temperature is 140-180℃; the reaction time is 15-360min.

[0052] The specific process of the method for preparing formic acid using a MOF-derived porous carbon composite manganese oxide catalyst provided in the present application is described in detail below in conjunction with specific examples.

[0053] Embodiment 1:

[0054] A solid mixture of manganese source MnCl2·4H2O (6mmol) and ligand 2,5-dihydroxyterephthalic acid (2mmol) was dissolved in a mixed solution of dimethylformamide (DMF): ethanol: water = 15:1:1 (v / v / v) to obtain a manganese solution and a ligand solution. The manganese solution and the ligand solution were stirred and mixed at a speed of 400rpm at room temperature to obtain a reaction solution, and the reaction solution was evenly transferred to a polytetrafluoroethylene-lined hydrothermal reactor to keep the reaction temperature fluctuating within a preset range. After a period of reaction, the reaction solution was placed in an oven for heating at a temperature of 135°C for 24h. After the heating was completed, the solid was centrifuged and washed and dried at a drying temperature of 80°C for 12h. The dried solid material was carbonized and calcined under nitrogen protection gas at a calcination temperature of 450°C to finally obtain a porous carbon composite manganese oxide catalyst 1 (MnxOy / C-1).

[0055] Embodiment 2:

[0056] A solid mixture of manganese source MnCl2·4H2O (6mmol) and ligand 2,5-dihydroxyterephthalic acid (2mmol) was dissolved in a mixed solution of dimethylformamide (DMF): ethanol: water = 15:1:1 (v / v / v) to obtain a manganese solution and a ligand solution. The manganese solution and the ligand solution were stirred and mixed at a speed of 400rpm at room temperature to obtain a reaction solution, and the reaction solution was evenly transferred to a polytetrafluoroethylene-lined hydrothermal reactor to keep the reaction temperature and reaction pressure fluctuating within a preset range. After a period of reaction, the reaction solution was placed in an oven for drying and heating at a temperature of 135°C for 24h. After heating, the solid was centrifuged and washed and dried at a drying temperature of 80°C for 12h. The dried solid material was carbonized and calcined in an argon-hydrogen mixed gas (H2-Ar) at a calcination temperature of 450°C to obtain a porous carbon composite manganese oxide catalyst 2 (MnxOy / C-2).

[0057] The porous carbon composite manganese oxide catalysts prepared in Example 1 and Example 2 were subjected to X-ray diffraction analysis (XRD) to obtain the following: Figure 3 XRD spectra of carbon composite manganese oxide catalysts 1 and 2 are shown.

[0058] like Figure 4 The TEM spectra of carbon composite manganese oxide catalysts 1 and 2 prepared in the examples of the present application are shown in FIG. a, wherein FIG. b is a TEM image of the precursor, FIG. c is an EDS element distribution image of Example 1, FIG. d is a TEM image of Example 2, and FIG. e is an EDS element distribution image of Example 2. Figure 4 It can be determined that the morphology of the porous carbon composite manganese oxide catalyst is retained compared to the precursor, that is, the morphology of the porous carbon composite manganese oxide catalyst is similar to that of the precursor. At the same time, spectral analysis (EDS) can determine that the manganese element in the porous carbon composite manganese oxide catalyst mainly exists in the form of manganese oxide, and the manganese oxide is evenly distributed and presents a composite state with the carbon element.

[0059] Application Example 1:

[0060] Take 0.04 g of the porous carbon composite manganese oxide catalyst 1 (MnxOy / C-1) prepared in Example 1, 0.08 g of monosaccharide, and 4 mL of ultrapure water in a reactor, and at the same time, fill the reactor with oxygen and pressurize it to 4 MPa and heat it to 160°C, and continue the reaction for 60 min; after the reaction, the reaction mixture is quickly cooled in an ice water bath, and then filtered with a filter membrane, and the filtered solution is taken for liquid chromatography to determine the product, and the formic acid yield is calculated to be 36%.

[0061] Application Example 2

[0062] 0.04 g of the porous carbon composite manganese oxide catalyst 2 (MnxOy / C-2) prepared in Example 2, 0.08 g of monosaccharide, and 4 mL of ultrapure water were placed in a reactor. At the same time, oxygen was introduced into the reactor and pressurized to 4 MPa and heated to 160°C. The reaction was continued for 120 min. After the reaction was completed, the reaction mixture was quickly cooled with an ice water bath, and then filtered with a filter membrane. The filtered solution was taken for liquid chromatography to determine the product. The formic acid yield was calculated to be 49%. Figure 5 As shown in FIG. 1 , it is a graph of monosaccharide conversion and formic acid yield of the carbon composite manganese oxide catalyst prepared in Example 1 and Example 2 provided in the present application. Figure 6 Shown are the HPLC chromatograms of Example 1 and Example 2 provided in this application.

[0063] The conditions of liquid chromatography are as follows: the chromatographic column is Shodex SH1011, the mobile phase is 0.5 mL / min sulfuric acid solution (5 mM), the column temperature is 50°C, the injection volume is 10 uL, the glucose and formic acid detectors are differential detectors, and the detector temperature is 35°C.

[0064] Glucose conversion rate (%) = (molar amount of glucose in reaction / molar amount of glucose in the initial reaction) × 100%

[0065] Formic acid yield (%) = (mol amount of formic acid generated / (initial molar amount of glucose × 6)) × 100%

[0066] It can be seen that the method for preparing formic acid using the MOF-derived porous carbon-composite manganese oxide catalyst disclosed in the present application, by preparing MOF-derived carbon-composite manganese oxide and using the MOF-derived carbon-composite manganese oxide as a catalyst to prepare formic acid, has simple steps, can effectively improve the efficiency of converting monosaccharides into formic acid, and is safer and environmentally friendly.

[0067] The present application also provides formic acid, which is prepared by the method for preparing formic acid using the MOF-derived porous carbon composite manganese oxide catalyst provided in any of the above embodiments, and therefore has all the same beneficial effects, and this embodiment will not be repeated here.

[0068] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0069] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application shall be included in the protection scope of the present application. The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing formic acid using a MOF-derived porous carbon composite manganese oxide catalyst, characterized in that: include: Preparation of manganese MOF precursor; Carbonizing the MOF precursor to obtain a MOF-derived carbon-composite manganese oxide; The carbon-composite manganese oxide derived from the MOF is used as a catalyst to catalyze an oxidation reaction of monosaccharides in a water environment to obtain formic acid.

2. The method for preparing formic acid using a MOF-derived porous carbon composite manganese oxide catalyst according to claim 1, characterized in that: The preparation of the manganese MOF precursor comprises: Dissolving a manganese source and a complexing agent in corresponding solvents respectively to obtain a manganese solution and a complexing agent solution; Stirring the manganese solution and the complexing agent solution separately, and adding the manganese solution and the complexing agent solution into a reaction kettle under stirring to obtain a reaction solution; Controlling the temperature of the reactor to a preset temperature range, and controlling the reaction liquid to react for a preset time within the preset temperature range; The reaction solution after the reaction is centrifuged and dried to obtain the manganese MOF precursor.

3. The method for preparing formic acid using a MOF-derived porous carbon composite manganese oxide catalyst according to claim 2, characterized in that: The manganese source is a manganese salt.

4. The method for preparing formic acid using a MOF-derived porous carbon composite manganese oxide catalyst according to claim 3, characterized in that: The manganese salt includes one or more of KMnO4, Mn(NO3)2, (CH3COO)2Mn, MnCl2, and MnSO4.

5. The method for preparing formic acid using a MOF-derived porous carbon composite manganese oxide catalyst according to claim 2, characterized in that: The complexing agent includes one or more of tribenzoic acid, 2.5-dihydroxyterephthalic acid, 2-methylimidazole, terephthalic acid, and imidazole.

6. The method for preparing formic acid using a MOF-derived porous carbon composite manganese oxide catalyst according to claim 2, characterized in that: The molar ratio of the manganese source to the complexing agent is 1:1-9:

1.

7. The method for preparing formic acid using a MOF-derived porous carbon composite manganese oxide catalyst according to claim 2, characterized in that: The carbonization temperature for carbonizing the MOF precursor is 200-1000° C., the heating rate is 1-10° C. / min, and the carbonization time is 2-5 hours.

8. The method for preparing formic acid using the MOF-derived porous carbon composite manganese oxide catalyst according to claim 1, characterized in that: The mass ratio of the monosaccharide to the manganese oxide is 1:(0.1-1), and the volume ratio of the mass of the monosaccharide to the water is 1 mg:(0.025-0.1) mL.

9. The method for preparing formic acid using the MOF-derived porous carbon composite manganese oxide catalyst according to claim 1, characterized in that: The reaction pressure of the oxidation reaction is 0.5-4 MPa, the reaction temperature is 140-180° C., and the reaction time is 15-360 min.

10. Formic acid, characterized in that The method for preparing formic acid using the MOF-derived porous carbon composite manganese oxide catalyst as described in any one of claims 1 to 9 is adopted.

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