Method for promoting air conversion to generate nitrate radicals by using organic aldehyde / alcohol

Abstract

The invention discloses a method for promoting air conversion to generate nitrate by using organic aldehyde / alcohol, which comprises the following steps: introducing air and organic aldehyde / alcohol into a stainless steel reaction kettle, and obtaining nitrate and corresponding high-added-value organic acid under the condition of 160-280 DEG C and light assistance. The invention aims to solve the problems of ammonia source consumption, high energy consumption, environmental pollution and the like in the traditional nitric acid production process. According to the method, a clean and environment-friendly photocatalytic reaction mode is adopted, and the yield is greatly improved on the premise that organic aldehyde / alcohol is used as a co-reactant. A catalyst used in the reaction is an iron-based catalyst. According to the method, gas-solid catalytic reaction is adopted, nitrate and corresponding organic acid are directly generated on the surface of the catalyst, emission of greenhouse gas is relieved, environmental protection, equipment miniaturization and use convenience are facilitated, and under the large background of domestic de-productivity, implementation of the scheme has great commercial value and market prospects.

Description

Technical Field

[0001] The present invention belongs to the field of chemical technology, and relates to a method for preparing nitric acid, in particular to a method for generating nitric acid and high-value organic acids by nitrogen, oxygen, organic aldehyde / alcohol and water under photo-assisted catalysis Background Art

[0002] Nitric acid (HNO3) is an important raw material for fertilizers and explosives. Its industrial production mainly relies on the Ostwald process, using ammonia as the nitrogen source. However, ammonia is usually synthesized by the Haber-Bosch process under high temperature (≈700K) and high pressure (≈100atm) conditions. This process not only consumes a large amount of energy but also emits a large amount of greenhouse gases, seriously restricting its environmental friendliness and sustainable development prospects

[0003] In contrast, the direct oxidation of nitrogen (N2), oxygen (O2) and water (H2O) to produce HNO3 (reaction formula: 2N2 + 5O2 + 2H2O → 4HNO3) theoretically provides a more green and low-consumption synthesis route. The raw materials required for this method are rich and widely available, which can effectively reduce the energy consumption and environmental pollution problems in industrial production. However, there are multiple challenges in directly using atmospheric nitrogen for oxidation synthesis. First, the triple bond in the nitrogen molecule is extremely stable, with a bond energy as high as 941 kJ / mol, making the activation of N2 molecules extremely difficult; second, the Gibbs free energy of the nitrogen oxidation reaction is about 87.7 kJ / mol, resulting in a large kinetic barrier for the direct reaction between nitrogen and oxygen. In addition, the mismatch of the molecular orbitals between nitrogen and oxygen further reduces the possibility of their direct reaction. These factors together make it difficult to achieve efficient conversion of this reaction under conventional conditions

[0004] In recent years, in order to overcome this challenge, researchers have focused on exploring new catalysts that can activate nitrogen molecules under mild conditions. Iron-based catalysts have received extensive attention due to their low cost, rich resources and unique advantages in activating inert molecules (such as N2, CO2, CH4, etc.). Although certain progress has been made in other reaction systems, there are still severe challenges in using iron-based or other new catalysts to achieve efficient direct oxidation of nitrogen to prepare nitric acid, and their reaction activity and selectivity need to be further improved

[0005] Therefore, it is necessary to invent a synthesis route to increase the yield of nitrate radicals to solve the problems of high energy consumption and high pollution in traditional industrial production Summary of the Invention

[0006] In view of the above problems, the technical objective of the present invention is to provide a method for efficiently synthesizing nitrate radicals to significantly increase the yield. Specifically, the present invention provides a method for promoting the conversion of air into nitrate radicals by organic aldehydes / alcohols. This method uses a gas-solid two-phase system reaction, and under photo-assisted and low-temperature conditions, directly generates nitric acid and corresponding high-value organic acids, with the advantages of alleviating greenhouse gas emissions, being environmentally friendly, miniaturizing equipment, and being convenient to use. In the context of promoting capacity reduction in the country, the implementation of this technical solution has great commercial value and market prospects.

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

[0008] The present invention first discloses a method for promoting the conversion of air into nitrate radicals by organic aldehydes / alcohols, including:

[0009] Introduce air and organic aldehydes / alcohols into the catalytic system reactor, introduce the gas at room temperature, seal the reaction kettle and heat it to a predetermined temperature, add an iron-based catalyst, and carry out the reaction under photo-assisted action to generate nitrate radicals and corresponding high-value organic acids.

[0010] Further, the organic aldehyde includes at least one of acetaldehyde, isobutyraldehyde, terephthalaldehyde, and benzaldehyde; the organic alcohol includes at least one of ethanol, isobutanol, terephthalyl alcohol, and benzyl alcohol.

[0011] Further, the rate of introducing the organic aldehydes / alcohols into the catalytic system reactor is 0.1 - 5 mL / min.

[0012] Further, the iron-based catalyst includes but is not limited to any one of Fe-TiO2, Fe-WO3, Fe2O3, and 316L steel.

[0013] Further, the introduced gas is air, or a mixed gas of nitrogen and oxygen; the total pressure of the introduced gas is not less than 0.5 MPa, and the gas flow rate is 10 mL / min.

[0014] Further, the volume ratio of nitrogen to oxygen is 4:1.

[0015] Further, the predetermined temperature is 160 - 280 °C; the photo-assisted irradiation intensity is 100 - 600 mW / cm 2 .

[0016] Further, the catalytic system reactor is a tubular stainless steel reactor or a kettle-type stainless steel reactor.

[0017] The present invention also discloses a mixed solution of nitrate radicals and high-value organic acids generated by any of the above methods.

[0018] The beneficial effects of the present invention are as follows:

[0019] The present invention creatively uses nitrogen, oxygen, and an organic aldehyde / alcohol solution as raw materials. Under the condition of 160 - 280 °C and with the assistance of light irradiation, nitric acid and high - value - added organic acids are catalytically generated. This method makes full use of nitrogen and oxygen in the air and synthesizes nitrate on the catalyst surface through synchronous photocatalysis. This method is conducive to saving fossil energy and reducing the emissions of carbon dioxide. The experimental steps of the present invention are relatively simple and it is easy to collect the products. Its reactants are humidified air and an organic aldehyde / alcohol solution, and the raw materials are cheap and easily available.

[0020] The photocatalytic reaction of the present invention can occur at a low temperature (160 - 280 °C), and the reaction pressure can be adjusted according to the experiment. Compared with the traditional high - temperature and high - pressure direct synthesis method, low temperature and high pressure are more conducive to the progress of the process.

[0021] The experimental results show that for the preparation method provided by the present invention, a mixed gas of nitrogen and oxygen is introduced and the reaction occurs under sunlight irradiation conditions. The products are analyzed by ion chromatography and isotope GCMS, indicating the generation of nitrate in the solution. Description of the Drawings

[0022] See Figure 1 , Figure 1 which is the design drawing of the device for catalytic synthesis of nitric acid provided by the present invention. Among them, 1. air generating device, 2. air pressure indicator, 3. air outlet pipeline, 4. liquid injection pump, 5. liquid sampling pipeline, 6. liquid source device, 7. liquid injection pump outlet pipeline, 8. pre - heating cavity, 9. pipeline pressure indicator, 10. pre - heating cavity outlet pipeline, 11. light source injection port of the tubular reactor, 12. tubular reaction furnace, 13. condenser, 14. reaction liquid outlet pipeline, 15. tubular reaction furnace outlet pipeline, 16. xenon light source, 17. condenser gas outlet pipeline.

[0023] Figure 2 It is the performance evaluation diagram of photocatalytic nitrogen oxidation reaction with nickel - doped titanium dioxide as the photocatalyst and different concentrations of acetaldehyde solution as the reaction substrate at 200 °C.

[0024] Figure 3 It is the performance evaluation data of photocatalytic nitrogen oxidation reaction with nickel - doped titanium dioxide as the photocatalyst and 40% volume fraction of acetaldehyde solution as the reaction substrate at different temperatures.

[0025] Figure 4 It is the performance evaluation diagram of photocatalytic nitrogen fixation reaction with nickel - doped titanium dioxide as the photocatalyst and different volume fractions of ethanol solution at 200 °C.

[0026] Figure 5Performance evaluation diagram for the photocatalytic nitrogen oxidation reaction with an ethanol solution at a volume fraction of 80% as the substrate at 200 °C.

[0027] Figure 6 Based on the preparation method of the present invention, isotope qualitative analysis of the gas-phase products was carried out using GCMS.

[0028] Figure 7 Calibration line of the chromatogram test of nitrate ions for the preparation method of the present invention. Detailed implementation mode

[0029] The present invention will be described in detail below in conjunction with embodiments and drawings. However, it should be understood that the embodiments and drawings are only used for exemplary description of the present invention and do not constitute any limitation to the protection scope of the present invention. All reasonable transformations and combinations within the scope of the inventive concept of the present invention fall within the protection scope of the present invention.

[0030] For all raw materials of the present invention, there is no particular limitation on their sources. They can be purchased on the market or prepared according to the conventional methods well-known to those skilled in the art.

[0031] For all raw materials of the present invention, their sources and abbreviations belong to the conventional sources and abbreviations in the art, and are clear and definite in the fields related to their relevant uses. Those skilled in the art can purchase them from the market or prepare them by conventional methods according to the abbreviations and corresponding uses.

[0032] The present invention provides a method for synthesizing nitrate, which is characterized by including the following steps: humidified air and an organic aldehyde / alcohol solution are introduced into a stainless steel reaction kettle and directly obtain nitrate after photocatalytic reaction.

[0033] The present invention has no particular limitation on the reaction device sand core. Those skilled in the art can select and adjust it according to the actual situation, the particle size of the catalyst, and the speed of capillary action.

[0034] The photochemical reaction of the present invention can occur at low temperatures, and the reaction pressure can be adjusted according to experiments. Compared with the traditional high-temperature and high-pressure direct synthesis method, low temperature and high pressure are more conducive to the process.

[0035] The present invention has no particular limitation on the specific selection and conditions of the nitrogen. The conventional conditions and selections of nitrogen well-known to those skilled in the art can be used, and those skilled in the art can select and adjust according to the actual situation.

[0036] The present invention has no particular limitation on the specific selection and conditions of the oxygen gas. The conventional conditions and selections of carbon dioxide gas well-known to those skilled in the art can be used, and those skilled in the art can select and adjust according to the actual situation.

[0037] The volume ratio of nitrogen gas to oxygen gas in the present invention is 4:1 or air. The pressure is preferably above 0.5 Mpa.

[0038] The present invention also provides a nitric acid synthesis device. Refer to the attached Figure 1 In the reactor, the acetaldehyde solution is vaporized under heating, reaches the surface of the catalyst, and forms nitrate radicals under light illumination conditions.

[0039] In the present invention, the device for photochemically synthesizing nitrate radicals includes a gas mixing device.

[0040] To further illustrate the present invention, the following describes in detail the method for directly synthesizing nitrate radicals provided by the present invention in combination with embodiments. However, it should be understood that these embodiments are implemented on the premise of the technical solution of the present invention, and give detailed implementation manners and specific operation processes. They are only to further illustrate the features and advantages of the present invention, rather than a limitation on the claims of the present invention. The protection scope of the present invention is not limited to the following embodiments.

[0041] Example 1

[0042] Evenly sprinkle 5 mg of iron-doped titanium dioxide powder on the sand core. Place the sand core in a quartz glass reaction dish containing 1 ml of acetaldehyde / alcohol solution, and then place the quartz glass reaction dish in a photocatalytic reaction kettle. First, introduce compressed air into the reaction kettle for 5 minutes, close the valve of the reaction kettle to increase the air pressure in the kettle to 0.5 Mpa or above. Turn on the photocatalytic xenon lamp light source, shine the light into the reaction cavity, and directly irradiate the surface of the catalyst. After reacting for 1 hour, turn off the light source, take out the reaction glass dish, collect the solution, and conduct tests.

[0043] Example 2

[0044] Evenly sprinkle 5 mg of Fe-doped titanium dioxide powder on the sand core. Place the sand core in a quartz glass reaction dish containing 1 ml of benzyl alcohol / aldehyde solution, and then place the quartz glass reaction dish in a photocatalytic tripod reaction kettle. First, introduce compressed air into the reaction kettle for 5 minutes, close the valve of the reaction kettle to increase the air pressure in the kettle to 0.5 Mpa. Turn on the photocatalytic xenon lamp light source, shine the light into the reaction cavity, and directly irradiate the surface of the catalyst. After reacting for 1 hour, turn off the light source, take out the reaction glass dish, collect the solution, and conduct tests.

[0045] Example 3

[0046] Sprinkle 5 mg of Fe-doped titanium dioxide powder evenly on the sand core. Place the sand core in a quartz glass reaction vessel containing 1 ml of isopropanol / aldehyde solution, and then place the quartz glass reaction vessel in a photocatalytic reactor. First, introduce compressed air into the reactor for 5 minutes, then close the valve of the reactor to increase the pressure inside the reactor to 0.5 Mpa. Turn on the photocatalytic xenon light source and shine the light into the reaction cavity, directly irradiating the surface of the catalyst. After reacting for 1 hour, turn off the light source, take out the reaction glass vessel, collect the solution, and conduct tests.

[0047] Example 4

[0048] Place 5 mg of 316L mesh on the sand core. Place the sand core in a quartz glass reaction vessel containing 1 ml of acetaldehyde / alcohol solution, and then place the quartz glass reaction vessel in a photocatalytic reactor. First, introduce compressed air into the reactor for 5 minutes, then close the valve of the reactor to increase the pressure inside the reactor to 0.5 Mpa. Turn on the photocatalytic xenon light source and shine the light into the reaction cavity, directly irradiating the surface of the catalyst. After reacting for 1 hour, turn off the light source, take out the reaction glass vessel, collect the solution, and conduct tests.

[0049] Example 5

[0050] Place 5 mg of 316L mesh on the sand core. Place the sand core in a quartz glass reaction vessel containing 1 ml of isopropanol / aldehyde solution, and then place the quartz glass reaction vessel in a photocatalytic reactor. First, introduce compressed air into the reactor for 5 minutes, then close the valve of the reactor to increase the pressure inside the reactor to 0.5 Mpa. Turn on the photocatalytic xenon light source and shine the light into the reaction cavity, directly irradiating the surface of the catalyst. After reacting for 1 hour, turn off the light source, take out the reaction glass vessel, collect the solution, and conduct tests.

[0051] Example 6

[0052] Place 5 mg of 316L mesh on the sand core. Place the sand core in a quartz glass reaction vessel containing 1 ml of benzyl alcohol / aldehyde solution, and then place the quartz glass reaction vessel in a photocatalytic reactor. First, introduce compressed air into the reactor for 5 minutes, then close the valve of the reactor to increase the pressure inside the reactor to 0.5 Mpa. Turn on the photocatalytic xenon light source and shine the light into the reaction cavity, directly irradiating the surface of the catalyst. After reacting for 1 hour, turn off the light source, take out the reaction glass vessel, collect the solution, and conduct tests.

[0053] Test Example 1

[0054] Detect the preparation process provided in Example 1 of the present invention.

[0055] Dilute the collected solution to a constant volume of 30 ml, take 0.5 - 1 ml of it for appropriate dilution, and then use ion chromatography for detection.

[0056] The results show that Ni-doped titanium dioxide powder has a stronger effect on the direct synthesis of nitrate from nitrogen. See Figures 2 - 6 .

[0057] Figure 2 It is a performance evaluation diagram of photocatalytic nitrogen oxidation reaction with nickel-doped titanium dioxide as the photocatalyst and different concentrations of acetaldehyde solution as the reaction substrate at 200 °C. The best substrate is found to be 40% acetaldehyde solution, with the nitrate production rate reaching 6380.388 nom / h and the acetate production rate reaching 15162.45 nom / h.

[0058] Figure 3 It is the performance evaluation data of photocatalytic nitrogen oxidation reaction with nickel-doped titanium dioxide as the photocatalyst and 40% volume fraction of acetaldehyde solution as the reaction substrate at different temperatures. It is concluded that 200 °C is the optimal reaction temperature, and it is proved that the acetaldehyde substrate cannot be activated at low temperatures, which affects the reaction efficiency, and too high temperature will cause the C-H bond of the acetaldehyde substrate to break and the active intermediate cannot be obtained, thus affecting the performance.

[0059] Figure 4 It is a performance evaluation diagram of photocatalytic nitrogen fixation reaction with nickel-doped titanium dioxide as the photocatalyst and ethanol solutions with different volume fractions at 200 °C. It is concluded that 80% volume fraction of ethanol solution is the optimal concentration for the reaction, with the nitrate production rate reaching 3256.04 nom / h and the acetate production rate reaching 7428.38 nom / h.

[0060] Figure 5 It is the evaluation of photocatalytic nitrogen oxidation performance with 80% volume fraction as the substrate. It is concluded that at 200 °C, the best nitrate production rate is 3256.04 nom / h, and at 225 °C, the best acetate production rate is 10691.86 nom / h.

[0061] Figure 6 Based on the preparation method of the present invention, GCMS is used for isotope qualitative analysis of the gas-phase products. As can be seen from the figure, when using 15 N as the reaction nitrogen source, we can detect 15 N2 16 O in the gas-phase products. When we use 18 O as the reaction oxygen source, we can detect 14 N2 18 O in the gas-phase products. When we use both 15 N and 18 O as the nitrogen source and oxygen source, we can detect 15 N2 18 O in the gas-phase products, which proves the feasibility of our nitrogen fixation reaction.

[0062] Figure 7 It is the calibration curve of the nitrate ion chromatographic test for the preparation method of the present invention. And the standard curve of nitrate is obtained as Y = 361289x + 674.8.

[0063] The above embodiments are only the preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions within the idea of the present invention belong to the protection scope of the present invention. It should be pointed out that for those of ordinary skill in the art, improvements and refinements made without departing from the principle of the present invention should also be regarded as within the protection scope of the present invention.

Claims

1. A method for promoting the conversion of air into nitrate by organic aldehyde / alcohol, comprising: Introducing air and organic aldehyde / alcohol into a catalytic system reactor, introducing the gas at room temperature, sealing the reaction kettle and heating it to a predetermined temperature, adding an iron-based catalyst, and reacting under the assistance of light to generate nitrate and corresponding high-value organic acids.

2. The method according to claim 1, wherein: The organic aldehyde includes at least one of acetaldehyde, isobutyraldehyde, terephthalaldehyde, and benzaldehyde; The organic alcohol includes at least one of ethanol, isobutanol, terephthalyl alcohol, and benzyl alcohol.

3. The method according to claim 1, wherein: The rate of introducing the organic aldehyde / alcohol into the catalytic system reactor is 0.1 - 5 mL / min.

4. The method according to claim 1, wherein: The iron-based catalyst includes any one of Fe-TiO2, Fe-WO3, Fe2O3, and 316L steel.

5. The method according to claim 1, wherein: The introduced gas is air, or a mixed gas of nitrogen and oxygen; The total pressure of the introduced gas is not less than 0.5 MPa, and the gas flow rate is 10 mL / min.

6. The method according to claim 5, wherein: The volume ratio of nitrogen to oxygen is 4:

1.

7. The method according to claim 1, wherein: The predetermined temperature is 160 - 280 °C; The intensity of the light-assisted irradiation is 100 - 600 mW / cm 2 .

8. The method according to claim 1, wherein: The catalytic system reactor is a tubular stainless steel reactor or a kettle-type stainless steel reactor.

9. A nitrate generated by the method according to any one of claims 1 to 8.

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