Method for selectively synthesizing methyl formate by catalyzing ozonized methanol at ultralow temperature by using graphdiyne catalyst

Abstract

The invention discloses a method for selectively synthesizing methyl formate by catalyzing ozonized methanol at an ultralow temperature by using a graphdiyne catalyst, and belongs to the technical field of fine chemical engineering. The method comprises the following steps: taking graphdiyne as a catalyst, carrying out catalytic reaction in a mixed atmosphere containing methanol and ozone, and selectively synthesizing methyl formate, the temperature of the catalytic reaction is-25 DEG C to 25 DEG C; the concentration of the methanol in the mixed atmosphere is 3000 to 10000 ppm; the concentration of ozone in the mixed atmosphere is 750 ppm. An activity test result shows that the graphdiyne catalyst has 92% methyl formate selectivity and 16-round cycle test stability at an ultralow temperature (25 DEG C). According to the method, the graphdiyne catalyst does not need to be activated, the catalytic activity is high, no metal exists in the catalyst, and pollution to the environment is avoided.

Description

Technical Field

[0001] The invention relates to the technical field of fine chemical engineering, and in particular to a method for selectively synthesizing methyl formate by using a graphyne catalyst to catalyze ozonation of methanol at ultra-low temperature. Background Art

[0002] Methyl formate (MF) is a colorless, fragrant, volatile liquid. It is often considered to be one of the most basic structural units of C1 chemistry and a key synthetic intermediate in the coal chemical industry chain. Long-term exposure to the atmosphere of methyl formate will have a strong irritating effect on the human respiratory tract, eyes, and nose, and can cause chest oppression and lead to breathing difficulties. Importantly, methyl formate is an important intermediate, solvent and additive widely used in the fields of petrochemicals, pesticides, organic synthesis and medicine. For example, it can be directly used as a fumigant and fungicide for treating tobacco, dried fruits, grains, etc.; it is also commonly used as a solvent for nitrocellulose and cellulose acetate; in medicine, it is often used as a synthetic raw material for drugs such as methyl pyrimidine sulfonate and the antitussive dextromethorphan. The market application potential is huge.

[0003] At present, the methods for selectively preparing methyl formate from methanol that have been reported mainly include: direct methanol esterification (strong acid, 70°C), methanol carbonylation (high pressure, 110°C), methanol catalytic dehydrogenation (300°C), formaldehyde dimerization, direct synthesis of synthesis gas, photocatalysis (currently unable to be scaled up), and carbon dioxide methanol hydrogenation condensation. Among them, methanol catalytic dehydrogenation is considered to be the most industrially significant process route at present, but its industrial-scale synthesis reaction has high energy consumption and is constrained by thermodynamic equilibrium. Therefore, it is crucial to develop a new green, low-carbon and scalable technology for selectively preparing methyl formate from methanol at ultra-low temperature. Summary of the invention

[0004] The purpose of the present invention is to provide a method for selectively synthesizing methyl formate by ultra-low temperature catalytic ozonation of methanol using a graphene catalyst, so as to solve the problem that most of the existing methods for catalyzing the synthesis of methyl formate with methanol have high temperatures, resulting in high energy consumption in the production process of methyl formate.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] One of the technical solutions of the present invention is the use of graphyne as a catalyst in the ultra-low temperature catalytic ozonation of methanol to selectively synthesize methyl formate, wherein the ultra-low temperature specifically refers to -25-25°C.

[0007] The second technical solution of the present invention is a method for selectively synthesizing methyl formate by ultra-low temperature catalytic ozonation of methanol using a graphene catalyst, comprising the following steps:

[0008] Using graphene (named GDY) as a catalyst, a catalytic reaction is carried out in a mixed atmosphere containing methanol and ozone to selectively synthesize methyl formate; the temperature of the catalytic reaction is -25-25°C, preferably 25°C.

[0009] In the reaction system of the present invention, ozone molecules first react with the electron-rich active site sp-C in gydne to rapidly generate surface active oxygen species (active single oxygen), which oxidize sp-C to C=O double bonds, and gydne generates oxidized gydne (named GDY-6O) in situ during the reaction. The newly generated C=O functional group acts as a proton acceptor, and methanol acts as a proton donor, generating weak hydrogen bond interactions at the interface of oxidized gydne (GDY-6O), and further proton tunneling effect occurs, so that the hydroxyl protons of methanol are rapidly transferred to the C=O functional group of oxidized gydne (GDY-6O), and finally the dehydrogenation of methanol (obtaining CH2O·) and CO coupling to produce methyl formate (CH3OH+CH2O·→CH3OCHO+2H(C-OH)) are achieved, and at the same time, the C=O functional group is reduced to a hydroxyl group (C-OH), and then oxidized by ozone to a C=O functional group in the next step, achieving active site regeneration and sustainable catalysis.

[0010] Furthermore, the concentration of methanol in the mixed atmosphere is 3000-10000 ppm (specifically referring to volume concentration).

[0011] Furthermore, the concentration of ozone in the mixed atmosphere is 750 ppm (specifically referring to volume concentration).

[0012] Furthermore, the ozone is generated by oxygen under the action of an ozone generator.

[0013] Furthermore, the specific operation of using graphyne as a catalyst to carry out a catalytic reaction in a mixed atmosphere containing methanol and ozone is as follows: placing the graphyne catalyst in a reaction container, introducing methanol gas and nitrogen into the reaction container, and simultaneously introducing oxygen into an ozone generator, and the mixed gas (containing oxygen and ozone) output after the oxygen reacts with the ozone generator to generate ozone enters the reaction container (the concentration of ozone in the mixed atmosphere in the reaction container is controlled by controlling the gas flow rate of oxygen and the power of the ozone generator, and nitrogen is used as a balance gas in the mixed atmosphere), and the methanol gas undergoes a catalytic reaction under the action of the graphyne catalyst and ozone to synthesize methyl formate.

[0014] Furthermore, the space velocity of the catalytic reaction is 30000-120000 mL g -1 h -1 .

[0015] Furthermore, the graphyne is used in the form of pure graphyne powder, or prepared into an integral catalyst with a carrier.

[0016] Furthermore, the particle size of the graphyne powder is 40-60 mesh.

[0017] The present invention discloses the following technical effects:

[0018] The present invention proposes for the first time the use of graphyne as a catalyst in the ultra-low temperature (-25-25° C.) catalytic ozonation of methanol to selectively synthesize methyl formate.

[0019] The present invention provides a new method for selectively synthesizing methyl formate by ultra-low temperature catalytic ozonation of methanol using a graphyne catalyst. Different from the traditional methanol thermal catalytic dehydrogenation synthesis pathway, the high reactivity of ozone enables the reaction to be carried out at an ultra-low temperature (-25-25°C), greatly reducing the energy consumption of process equipment and lowering economic costs.

[0020] The method of the present invention can achieve a 3% methanol conversion rate and a 92% methyl formate selectivity at ultra-low temperature (25° C.), which has an obvious energy consumption advantage compared with traditional processes.

[0021] The method of the invention has few reaction pollutants, generates only a small amount of carbon monoxide and carbon dioxide in addition to methyl formate, and the separation of process products is simple.

[0022] In the method of the present invention, the graphyne catalyst does not need to undergo an activation process, has high catalytic activity and good stability (remains stable after 16 rounds of cycle testing), contains no metal, and does not cause pollution to the environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 is a gas chromatogram of the catalytic reaction product in Example 1;

[0025] Figure 2 is the mass spectrum of the catalytic reaction product in Example 1;

[0026] Figure 3 The characterization results of the graphyne catalyst used in the embodiments and comparative examples of the present invention; wherein, a is the XRD pattern of the prepared graphyne catalyst (GDY); b is the Raman pattern of GDY; c is the XPS survey pattern of GDY; d is the XPS C1s pattern of GDY; e is the infrared spectrum of GDY; f is the SEM pattern and element mapping pattern of GDY;

[0027] Figure 4 This is the XPS O1s graph of the Graphdiyne catalyst (GDY) before the catalytic reaction in Example 1;

[0028] Figure 5 This is the XPS O1s graph of the sample graphene oxide (GDY-6O) after the graphene catalyst was used to catalyze the selective synthesis of methyl formate from methanol by ozonation in Example 1;

[0029] Figure 6 This is the EPR superoxide radical detection spectrum of graphyne (GDY) and graphyne oxide (GDY-6O);

[0030] Figure 7 These are the cyclic stability test results of the selective synthesis of methyl formate by ozonation of methanol over graphyne catalyst. DETAILED DESCRIPTION

[0031] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0032] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0033] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0034] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to the skilled artisan. The present invention description and examples are exemplary only.

[0035] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0036] The present invention provides the use of graphyne as a catalyst in the ultra-low temperature catalytic ozonation of methanol to selectively synthesize methyl formate, wherein the ultra-low temperature specifically refers to -25-25°C.

[0037] The present invention also provides a method for selectively synthesizing methyl formate by ultra-low temperature catalytic ozonation of methanol using a graphene catalyst, comprising the following steps:

[0038] Using graphyne as a catalyst, a catalytic reaction is carried out in a mixed atmosphere containing methanol and ozone to selectively synthesize methyl formate; the temperature of the catalytic reaction is -25-25°C, preferably 25°C.

[0039] As a preferred embodiment of the present invention, the concentration of methanol in the mixed atmosphere is 3000-10000 ppm.

[0040] As a preferred embodiment of the present invention, the concentration of ozone in the mixed atmosphere is 750 ppm.

[0041] As a preferred embodiment of the present invention, the ozone is generated by oxygen under the action of an ozone generator.

[0042] As a preferred embodiment of the present invention, the specific operation of using graphyne as a catalyst to carry out a catalytic reaction in a mixed atmosphere containing methanol and ozone is as follows: placing the graphyne catalyst in a reaction vessel, introducing methanol gas and nitrogen into the reaction vessel, and simultaneously introducing oxygen into an ozone generator, and the mixed gas (containing oxygen and ozone) output after the oxygen reacts with the ozone generator to generate ozone enters the reaction vessel (the concentration of ozone in the mixed atmosphere in the reaction vessel is controlled by controlling the gas flow rate of oxygen and the power of the ozone generator), and the methanol gas undergoes a catalytic reaction under the action of the graphyne catalyst and ozone to synthesize methyl formate.

[0043] As a preferred embodiment of the present invention, the concentration of methanol and the concentration of ozone in the mixed atmosphere are both inlet concentrations at the reaction container.

[0044] As a preferred embodiment of the present invention, the methanol gas specifically refers to a gas containing methanol, that is, a mixed gas of methanol and other gases (air or nitrogen, as a carrier gas), which can be generated by a VOCs generator. There is no special requirement for the concentration of methanol in the methanol gas, as long as the concentration of methanol in the mixed atmosphere in the final reaction container is 3000-10000ppm.

[0045] As a preferred embodiment of the present invention, the nitrogen is pure nitrogen with a concentration of >99.5%.

[0046] As a preferred embodiment of the present invention, the oxygen is pure oxygen with a concentration of >99.2%.

[0047] As a preferred embodiment of the present invention, the space velocity of the catalytic reaction is 30000-120000 mL g -1 h -1 .

[0048] As a preferred embodiment of the present invention, the catalytic reaction is carried out in a quartz glass tube fixed bed reactor, and the reaction container is a quartz glass pipe.

[0049] As a preferred embodiment of the present invention, the temperature of the catalytic reaction specifically refers to the reaction bed temperature, which is controlled by a constant temperature water bath or a low-temperature circulating freezing tank, and one of methanol, ethanol and ethylene glycol can be added as a freezing liquid.

[0050] As a preferred embodiment of the present invention, the concentration of ozone is monitored online in real time by an ozone detector.

[0051] As a preferred embodiment of the present invention, the concentration changes of components such as methanol, methyl formate, carbon monoxide and carbon dioxide in the tail gas are monitored by FID gas chromatography (FID detector) and a handheld VOCs concentration detector.

[0052] As a preferred embodiment of the present invention, the graphyne is used in the form of pure graphyne powder, or prepared into an integral catalyst with a carrier (ie, graphyne powder and a carrier are composited to prepare an integral catalyst for the catalytic reaction).

[0053] As a preferred embodiment of the present invention, when the graphyne is used in the form of pure graphyne powder, the particle size of the graphyne powder is 40-60 mesh (controlled by tabletting and sieving by a tablet press); the amount of the graphyne powder is 50-100 mg.

[0054] As a preferred embodiment of the present invention, when the graphyne and the carrier are prepared into an integral catalyst for use, the graphyne catalyst includes but is not limited to a graphyne / copper foam integral catalyst or a graphyne / carbon cloth integral catalyst; the specific preparation method of the integral catalyst can refer to the conventional method in the art and is not intended to be a limitation of the present invention.

[0055] The technical solution of the present invention is further described below in conjunction with specific embodiments.

[0056] The graphyne catalyst used in the following examples and comparative examples is graphyne powder prepared in the laboratory, and the preparation method is as follows:

[0057] 400 mg (0.61 mmol) hexa((trimethylsilyl)ethynyl)benzene and 5 mL 1M tetrabutylammonium fluoride solution (solvent is THF, containing 5 mmol of tetrabutylammonium fluoride) were added to 15 mL tetrahydrofuran (THF), stirred at 0°C in the dark for 10 min, then diluted with ethyl acetate, washed with saturated brine, dried with anhydrous Na2SO4, and the solvent was removed in vacuo to obtain product A. Product A was diluted with 120 mL pyridine, and the diluent was slowly added to a copper foil solution of 100 mL pyridine at 110°C, wherein 20 pieces of copper foil were added, each piece of copper foil having a size of 0.1×10×100 mm. Then the reaction was allowed to stand at 110°C in a nitrogen atmosphere for 3 days. After the reaction is completed, the mixture is washed with 60°C deionized water, ethanol and DMF (N,N-dimethylformamide) in sequence until the washing liquid is clear and colorless, and vacuum dried at 60°C for 24 hours to obtain black graphyne powder, which is pressed by a tablet press and sieved to prepare a 40-60 mesh powder as the graphyne catalyst (denoted as GDY) used in the specific embodiment of the present invention.

[0058] In addition to the graphyne catalyst prepared as described above, graphyne obtained by other means may also be selected, such as purchasing commercially available graphyne, which can achieve the technical effect of the present invention, that is, achieve the same or similar catalytic effect as the graphyne catalyst prepared as described above.

[0059] Example 1

[0060] A method for selectively synthesizing methyl formate by ultra-low temperature catalytic ozonation of methanol using a graphene catalyst, the specific operation is as follows:

[0061] 50 mg of graphyne catalyst was placed in a quartz glass tube of a U-shaped quartz glass tube fixed bed reactor with an inner diameter of 6 mm and an outer diameter of 8 mm. The temperature of the reaction bed was controlled to be 25°C by a constant temperature water bath. Methanol gas (gas flow rate of 30 mL / min, methanol concentration of 10000 ppm, carrier gas was nitrogen) and nitrogen (pure nitrogen, gas flow rate of 40 mL / min) were introduced into the quartz glass tube. At the same time, oxygen (pure oxygen, gas flow rate of 30 mL / min) was introduced into the ozone generator. The mixed gas (including oxygen and ozone) output after the oxygen reacted with the ozone generator to generate ozone entered the quartz glass tube. The concentration of methanol gas (inlet concentration) in the mixed atmosphere in the quartz glass tube was 3000 ppm, and the concentration of ozone (inlet concentration) was 750 ppm (the concentration of ozone was controlled by adjusting the power of the ozone generator). The reaction mass space velocity of the reaction system was 120000 mL g -1 h -1 .

[0062] The exhaust gas was collected twice with an air bag and tested and analyzed by gas chromatography-mass spectrometry respectively. Each test was named sample 1 and sample 2, and a methyl formate standard sample (standard sample, purchased commercial analytical grade methyl formate, brand Sinopharm) was used as a standard reference. Figure 1 The gas chromatogram obtained from the test shows that the peak positions of sample 1 and sample 2 are consistent with the peak position of the standard sample. Figure 2 is the corresponding mass spectrometry detection result. It can be seen that the peak positions of sample 1 and sample 2 are consistent with the peak position of the standard sample. Figure 1 and Figure 2 The results all proved the successful synthesis of methyl formate.

[0063] At the same time, the concentration changes of each gas in the tail gas were monitored by FID gas chromatography (FID detector) and handheld VOCs concentration detector, and the conversion rate of methanol and the selectivity of main products and by-products were calculated (tested 6 times within 1 hour, once every 10 minutes, and the average value was taken). The test results are as follows: methanol conversion rate is 3%, methyl formate selectivity is 92%, carbon monoxide selectivity is 2%, and carbon dioxide selectivity is 6%.

[0064] Test Example 1

[0065] Figure 3 The characterization results of the Graphdiyne catalyst (powder before tablet press processing) used in the examples and comparative examples of the present invention are shown in Figure 1. Among them, a is the XRD pattern of the prepared Graphdiyne catalyst (GDY); b is the Raman pattern of GDY; c is the XPS survey pattern of GDY; d is the XPS C1s pattern of GDY; e is the infrared spectrum of GDY; and f is the SEM pattern and element mapping pattern of GDY. Figure 3 XRD patterns of a and Figure 3 The Raman images of b all prove that the basic structural unit of the Graphene catalyst contains a benzene ring and a diacetylene bond. Figure 3 The infrared spectrum of e also detected the characteristic peaks of benzene ring C=C and acetylenic bond on the surface of GDY. Figure 3 The XPS survey of c shows that GDY is mainly composed of C and O elements. Figure 3 Element mapping of f also detected that C and O elements were evenly distributed on the GDY surface. Figure 3The XPS C1s peak fitting results of d show that GDY is mainly composed of sp-C and sp2-C, containing a small amount of CO bonds and C=O double bond functional groups (the surface of the graphyne catalyst will adsorb oxygen and will also be oxidized by X-rays during XPS detection, so XPS can detect the presence of a small amount of O element).

[0066] Figure 4 is the XPS O1s graph of the Graphdiyne catalyst (GDY) before the catalytic reaction in Example 1, Figure 5 This is the XPS O1s graph of the sample graphene oxide (GDY-6O) after the graphene catalyst catalyzed the ozonation of methanol to selectively synthesize methyl formate in Example 1. Figure 6 This is the EPR superoxide radical detection spectrum of graphyne (GDY) and graphyne oxide (GDY-6O).

[0067] Figure 4 This indicates that the GDY surface mainly contains adsorbed oxygen species. Figure 5 The peak fitting results show that C=O functional groups and C-OH functional groups are generated in situ on the surface of the catalyst material after ozone oxidation, among which the C=O functional group will become a new active site to participate in the dehydrogenation of methanol and CO coupling to produce methyl formate. Figure 6 This indicates that the oxygen-containing functional groups generated on the surface of the graphyne catalyst through ozone oxidation enable the resulting oxidized graphyne to produce stronger superoxide radical signals.

[0068] Example 2

[0069] The same as Example 1, except that the temperature of the reaction bed is controlled at 10° C. by a constant temperature water bath. The test results of this example are as follows: the methanol conversion rate is 2.7%, the methyl formate selectivity is 92%, the carbon monoxide selectivity is 3%, and the carbon dioxide selectivity is 5%.

[0070] Example 3

[0071] The same as Example 1, except that the temperature of the reaction bed is controlled to be 0° C. by a constant temperature water bath. The test results of this example are as follows: the methanol conversion rate is 2.2%, the methyl formate selectivity is 94%, the carbon monoxide selectivity is 3%, and the carbon dioxide selectivity is 3%.

[0072] Example 4

[0073] The same as Example 1, except that the temperature of the reaction bed is controlled at -10° C. by a thermostatic water bath. The test results of this example are as follows: the methanol conversion rate is 1.5%, the methyl formate selectivity is 95%, the carbon monoxide selectivity is 4%, and the carbon dioxide selectivity is 1%.

[0074] Example 5

[0075] The same as Example 1, except that the temperature of the reaction bed is controlled at -20° C. by a thermostatic water bath. The test results of this example are as follows: the methanol conversion rate is 0.4%, the methyl formate selectivity is 96%, the carbon monoxide selectivity is 3.4%, and the carbon dioxide selectivity is 0.6%.

[0076] Comparative Example 1

[0077] The same as Example 1, except that the catalytic reaction was carried out using an equal amount of activated carbon (with a particle size of 40-60 mesh) instead of the graphyne catalyst. The test results of this comparative example are as follows: the methanol conversion rate is 0.3%, the methyl formate selectivity is 0%, the carbon monoxide selectivity is 41%, and the carbon dioxide selectivity is 59%.

[0078] Comparative Example 2

[0079] The same as Example 1, except that the Graphene catalyst was replaced with an equal mass of graphene (with a particle size of 40-60 mesh) for catalytic reaction. The test results of this comparative example are as follows: methanol conversion is 4%, methyl formate selectivity is 0%, carbon monoxide selectivity is 37%, and carbon dioxide selectivity is 63%.

[0080] Comparative Example 3

[0081] 50 mg of graphyne catalyst was placed in a quartz glass tube of a U-shaped quartz glass tube fixed bed reactor with an inner diameter of 6 mm and an outer diameter of 8 mm. The reaction bed temperature was controlled at 25 °C by a constant temperature water bath. Methanol gas (gas flow rate of 30 mL / min, methanol concentration of 10000 ppm, carrier gas of nitrogen), nitrogen (pure nitrogen, gas flow rate of 40 mL / min), and oxygen (pure oxygen, gas flow rate of 30 mL / min) were introduced into the quartz glass tube. The concentration of methanol gas in the mixed atmosphere in the quartz glass tube was 3000 ppm, and the reaction mass space velocity of the reaction system was 120000 mL g -1 h -1 The concentration changes of each gas in the tail gas were monitored by FID gas chromatography (FID detector) and handheld VOCs concentration detector, and the conversion rate of methanol and the selectivity of the main product and by-product were calculated (6 tests within 1 hour, once every 10 minutes, and the average value was taken). The test results are as follows: methanol conversion rate is 0%, methyl formate selectivity is 0%, carbon monoxide selectivity is 0%, and carbon dioxide selectivity is 0%.

[0082] Example 6

[0083] Cyclic stability test

[0084] 50 mg of graphyne catalyst was placed in a quartz glass tube of a U-shaped quartz glass tube fixed bed reactor with an inner diameter of 6 mm and an outer diameter of 8 mm. The temperature of the reaction bed was controlled to be 25°C by a constant temperature water bath. Methanol gas (gas flow rate of 30 mL / min, methanol concentration of 10000 ppm, carrier gas was nitrogen) and nitrogen (pure nitrogen, gas flow rate of 40 mL / min) were introduced into the quartz glass tube. At the same time, oxygen (pure oxygen, gas flow rate of 30 mL / min) was introduced into the ozone generator. The mixed gas (including oxygen and ozone) output after the oxygen reacted with the ozone generator to generate ozone entered the quartz glass tube. The concentration of methanol gas in the mixed atmosphere in the quartz glass tube was 3000 ppm and the concentration of ozone was 750 ppm (the concentration of ozone was controlled by adjusting the power of the ozone generator). The reaction mass space velocity of the reaction system was 120000 mL g -1 h -1 After the catalytic reaction was carried out for 12 hours, the reaction gas path was switched to the bypass for 30 minutes, and then switched to the main path for catalytic reaction for 12 hours, and this was repeated for a total of 16 cycles of reaction.

[0085] The results of the cyclic stability test are shown in Figure 7 As shown by Figure 7 It can be seen that the graphyne catalyst remained stable after 16 rounds of cycle testing and maintained excellent catalytic activity during the 16th round of cycle testing. During the cyclic stability test, the methanol conversion rate was stably maintained at about 3%, and the methyl formate selectivity was maintained at about 92%.

[0086] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. The application of graphyne as a catalyst in the ultra-low temperature catalytic ozonation of methanol to selectively synthesize methyl formate, characterized in that: The ultra-low temperature specifically refers to -25-25°C.

2. A method for selectively synthesizing methyl formate by ultra-low temperature catalytic ozonation of methanol using a graphene catalyst, characterized in that: The following steps are involved: Using graphene as a catalyst, a catalytic reaction is carried out in a mixed atmosphere containing methanol and ozone to selectively synthesize methyl formate; the temperature of the catalytic reaction is -25-25°C.

3. The method for selectively synthesizing methyl formate by ultra-low temperature catalytic ozonation of methanol using a graphene catalyst as claimed in claim 2, characterized in that: The concentration of methanol in the mixed atmosphere is 3000-10000 ppm.

4. The method for selectively synthesizing methyl formate by ultra-low temperature catalytic ozonation of methanol using a graphene catalyst as claimed in claim 2, characterized in that: The concentration of ozone in the mixed atmosphere is 750 ppm.

5. The method for selectively synthesizing methyl formate by ultra-low temperature catalytic ozonation of methanol using a graphene catalyst as claimed in claim 2, characterized in that: The ozone is generated by oxygen under the action of an ozone generator.

6. The method for selectively synthesizing methyl formate by ultra-low temperature catalytic ozonation of methanol using a graphene catalyst as claimed in claim 2, characterized in that: The space velocity of the catalytic reaction is 30000-120000 mL g -1 h -1 .

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