A method for synthesizing urea

Abstract

The present invention discloses a method for synthesizing urea. A mixed gas containing water molecules, nitrogen, and carbon dioxide is introduced into a discharge reaction chamber, causing the water molecules to generate water radical cation clusters, which react with nitrogen and carbon dioxide to produce urea radical cations. These urea radical cations are then captured using a grounded or negatively connected device to produce urea. This method addresses the existing problem of harsh reaction conditions and the need for high temperature and high pressure when preparing urea from carbon dioxide. Furthermore, the method is environmentally friendly, mild, and catalyst-free, meeting carbon reduction requirements.

Description

Technical Field

[0001] The present invention relates to the technical field of nitrogen fixation, in particular to a method for synthesizing urea. Background Art

[0002] Nitrogen is widely present in the atmosphere and is an abundant, cheap, and readily available nitrogen source. However, nitrogen cannot be directly absorbed and utilized by humans, animals, and plants. It can only be applied to industrial production by converting free nitrogen in the air into nitrogen-containing compounds through chemical or biological methods. Therefore, research on nitrogen fixation and conversion is of great significance to the development of human society. The main methods of nitrogen fixation are biological nitrogen fixation, artificial chemical nitrogen fixation, and high-energy nitrogen fixation. Among the existing nitrogen fixation methods, only artificial chemical nitrogen fixation can be applied on a large scale in industrial production, and its main products are ammonia-containing compounds, such as urea.

[0003] Carbon dioxide (CO2) is a cheap and renewable C1 resource, yet it is also the primary culprit for global warming. Against this backdrop, CO2 reuse has become a global concern. Humans can capture CO2 from the environment and chemically transform it into high-value-added chemicals, currently primarily derived from petroleum, such as urea, carbonates, methanol, oxalic acid, and other important chemical products. However, CO2 is an extremely stable molecule, and its use as a raw material in chemical synthesis requires significant energy. Therefore, achieving efficient and economical chemical conversion has become a highly challenging research topic.

[0004] The synthesis of urea is a remarkable achievement in human industrial history. In 1828, German scientist Wöhler first achieved the synthesis of organic urea from inorganic matter in a laboratory. This achievement broke the historical barrier to artificial synthesis of organic matter and sparked the idea of ​​building a bridge between the living and non-living worlds. Currently, the mainstream process for industrial urea production worldwide is the direct synthesis of ammonia and CO2 (2NH3+CO2=NH4COONH2; NH3COONH2=NH2CONH2+H2O). This process requires high temperature and high pressure, making efficient conversion of CO2 to urea under mild conditions a hot topic for researchers. Summary of the Invention

[0005] The purpose of the present invention is to solve at least one of the technical problems existing in the prior art and to provide a novel reaction for the rapid synthesis of urea based on the reaction of water radical cations with CO2 and nitrogen. This reaction not only meets the requirements of new energy, but also has the characteristics of atom economy, greenness and pollution-freeness, and is a model of green synthetic chemistry.

[0006] The technical solutions of the present invention are as follows:

[0007] A method for synthesizing urea comprises introducing a mixed gas containing water molecules, nitrogen and carbon dioxide into a discharge reaction chamber to ionize the water molecules to generate water radical cation clusters, which react with nitrogen and carbon dioxide to obtain urea radical cations. The urea radical cations are then captured using a grounded or negatively connected device to produce urea.

[0008] The reaction principle is as follows:

[0009]

[0010] Furthermore, the flow rate of the nitrogen is 0.1 to 0.4 L / min.

[0011] Furthermore, the carbon dioxide flow rate is 0.1 to 0.4 L / min.

[0012] Furthermore, the discharge voltage in the discharge reaction chamber is 4-6 kV.

[0013] Furthermore, a discharge array needle plate and a stainless steel tank are provided in relative positions in the discharge reaction chamber, the discharge array needle plate is connected to the positive electrode of the high-voltage power supply, and the stainless steel tank is connected to the negative electrode of the high-voltage power supply. A reaction space is provided between the discharge array needle plate and the stainless steel tank, and the mixed gas is introduced into the reaction space.

[0014] Furthermore, the discharge array needle board is made by welding tungsten needles on a PCB perforated board, the spacing between needles on the discharge array needle board is optimized to be between 3 and 8 mm, and the curvature radius of the needle tip is optimized to be between 0.01 and 0.1 mm.

[0015] Furthermore, a urea detection developer or water or other absorbent solution for enriching urea is also placed in the discharge reaction chamber.

[0016] Furthermore, the urea detection color developing agent is p-dimethylaminobenzaldehyde or diacetyl oxime.

[0017] The present invention has the following beneficial effects: it utilizes a discharge reaction chamber to generate water radical cation clusters from a mixed gas containing water molecules. These water radical cation clusters react with nitrogen and carbon dioxide gases to produce urea radical cations. These urea radical cations quickly reach a stainless steel tank to produce urea. This method addresses the existing issue of using CO2 to produce urea, which requires harsh reaction conditions, high temperature, and high pressure. Furthermore, the method is green, mild, and catalyst-free. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments with reference to the accompanying drawings, in which:

[0019] Figure 1 Schematic diagram of the structure of a urea preparation device according to an embodiment of the present invention;

[0020] Figure 2 It is a structural diagram of the discharge array needle plate;

[0021] Figure 3 It is a structural diagram of the stainless steel tank;

[0022] Figure 4 This is the UV spectrum of urea prepared by the reaction of water radical cations with nitrogen and CO2 and then developed with p-dimethylaminobenzaldehyde;

[0023] Figure 5 The following are the UV spectra of urea standards with different concentrations reacting with p-dimethylaminobenzaldehyde;

[0024] Figure 6 This is the standard curve of urea.

[0025] 1-first pipe, 2-second pipe, 3-discharge reaction chamber, 4-reactant input channel, 5-discharge array needle plate, 6-stainless steel tank, 7-water storage container, 8-PCB perforated board, 9-tungsten needle, 10-rectangular groove. DETAILED DESCRIPTION

[0026] This section will describe in detail the specific embodiments of the present invention. The preferred embodiments of the present invention are shown in the accompanying drawings. The purpose of the accompanying drawings is to supplement the description of the text part of the specification with graphics, so that people can intuitively and vividly understand each technical feature and the overall technical solution of the present invention, but it should not be understood as a limitation on the scope of protection of the present invention.

[0027] In the description of the present invention, it should be understood that descriptions involving orientations, such as up, down, front, back, left, right, etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they cannot be understood as limitations on the present invention.

[0028] In the description of the present invention, "several" means one or more, "many" means more than two, "greater than," "less than," and "exceed" are understood to exclude the number itself, while "above," "below," and "within" are understood to include the number itself. The use of "first" and "second" in the description is solely for the purpose of distinguishing technical features and should not be construed as indicating or implying relative importance, implicitly specifying the number of the indicated technical features, or implicitly specifying the order of the indicated technical features.

[0029] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, and connecting should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention based on the specific content of the technical solution.

[0030] See also Figure 1-3 A urea preparation device used in a urea synthesis method according to an embodiment of the present invention specifically includes a discharge reaction chamber 3 , on which a reactant input channel 4 into which water is introduced is provided.

[0031] The discharge reaction chamber 3 is a frame structure with an open cover on top. When the cover is closed, it forms a sealed chamber with the frame structure. After the reaction is completed, the cover is opened and an auxiliary agent can be added to the stainless steel tank to confirm whether urea is produced or to facilitate the removal of the product.

[0032] The reactant channel 4 is connected to the water storage container 7, which is connected to a nitrogen gas source and a carbon dioxide gas source through a first pipeline 1 and a second pipeline 2, respectively.

[0033] After being moistened by a water storage container, nitrogen and carbon dioxide enter the discharge reaction chamber 3 through reactant channel 4. A water storage device 7 facilitates the introduction of water vapor into the discharge reaction chamber 3 and maintains a certain humidity. Preferably, the water molecules comprise 60 (v / v)% of the mixed gas, but this is not limited to this.

[0034] The discharge reaction chamber 3 is provided with a discharge array needle plate 5 and a stainless steel tank 6 positioned opposite each other. The discharge array needle plate 5 is connected to the positive electrode of a high-voltage power supply, and the stainless steel tank 6 is connected to the negative electrode of the high-voltage power supply. A reaction space is defined between the discharge array needle plate 5 and the stainless steel tank 6. Preferably, the voltage of the high-voltage power supply is 4 to 6 kV.

[0035] See also Figure 2 In this embodiment, the discharge array needle plate 5 is a rectangular structure, made by welding tungsten needles 9 onto a PCB perforated board 8. The spacing between needles on the discharge array needle plate 5 is 3-8 mm, and the radius of curvature of the needle tips is 0.01-0.1 mm. Preferably, all parts of the discharge array needle plate 5, except for the needle tips and the high-voltage contact portion, are coated with insulating varnish.

[0036] See also Figure 3 The stainless steel tank 6 has a rectangular groove 10, which has a low resistance and a strong conductive ability. The urea generated after the reaction is collected in the rectangular groove 10.

[0037] Based on the above device, the urea preparation method includes:

[0038] Nitrogen and carbon dioxide are respectively introduced into the water stored in the water storage device 7 through the first pipeline 1 and the second pipeline 2, so that the humidified mixed gas enters the discharge reaction chamber 3;

[0039] Turning on the high-voltage power supply and applying a high voltage to the discharge array needle plate 5 causes the needle tips of the discharge array needle plate 5 to generate water radical cation clusters. The generated water radical cation clusters react with nitrogen and carbon dioxide to generate urea radical cations, which are then transferred to the stainless steel tank 6 to form urea.

[0040] The urea formed on the stainless steel tank 6 is taken out and collected by opening the cover. In addition, the cover can also be opened and an auxiliary agent is added to the stainless steel tank 6. If color is developed, it is proved that urea is produced.

[0041] Specifically, by applying a high voltage (4 to 6 kV) to the discharge array needle plate 5, a corona discharge is generated at the tip of the discharge needle tip. At room temperature and pressure (for example, 25°C, one atmosphere of pressure), nitrogen with a certain humidity is used as a nitrogen source and carbon dioxide with a certain humidity is used as a carbon source. Water radical ion clusters are generated through high-voltage corona discharge. The water radical cation clusters are fully in contact with nitrogen and carbon dioxide and react to produce urea radical cations. The formed urea radical cations are simultaneously transferred to the stainless steel tank 6, and the generated urea is enriched on the stainless steel tank 6.

[0042] The following are several examples to verify the preparation results of the above urea preparation method:

[0043] Example 1

[0044] At room temperature and pressure, nitrogen (controlled flow rate of 0.1L / min) and carbon dioxide (controlled flow rate of 0.1L / min) gases are introduced into water. The humidified mixed gas flows into the discharge reaction chamber through a pipe. A high voltage (4kV) is applied to the discharge array needle plate 5, causing the generated urea free radical cations to be rapidly adsorbed into the stainless steel tank to produce urea.

[0045] Example 2

[0046] At room temperature and pressure, nitrogen (controlled flow rate of 0.2L / min) and carbon dioxide (controlled flow rate of 0.2L / min) gases are introduced into water. The humidified mixed gas flows into the discharge reaction chamber through a pipe. A high voltage (5kV) is applied to the discharge array needle plate 5, causing the generated urea free radical cations to be rapidly adsorbed into the stainless steel tank to produce urea.

[0047] Example 3

[0048] At room temperature and pressure, nitrogen (controlled flow rate of 0.3L / min) and carbon dioxide (controlled flow rate of 0.3L / min) gases are introduced into water. The humidified mixed gas flows into the discharge reaction chamber through a pipe. A high voltage (6kV) is applied to the discharge array needle plate 5, causing the generated urea free radical cations to be rapidly adsorbed into the stainless steel tank to produce urea.

[0049] Test 1: The product of Example 1 was added to a p-dimethylaminobenzaldehyde solution, and the color of the solution turned light yellow. The mixed solution was subjected to ultraviolet detection, and a characteristic absorption peak was observed at 420 nm. The characteristic absorption peak was the reaction product of urea and p-dimethylaminobenzaldehyde color developer. The peak absorption wavelength of the product was consistent with the literature report (Detection of trace urea in aqueous solution by p-dimethylaminobenzaldehyde colorimetric spectrophotometry 2011, Journal of Northeast Agricultural University, 42, 87-91). The results are as follows: Figure 4 This indicates that urea is produced by the reaction of water radical cations with nitrogen and carbon dioxide.

[0050] Test 2: Under normal temperature and pressure, a series of urea standard solutions with different concentrations (0, 10, 25, 50, 100, 1000 ppm) were prepared, and they were fully mixed with the p-dimethylaminobenzaldehyde solution and the color developer solution, and the shaken solutions were subjected to UV spectrum analysis. A characteristic absorption peak was observed at 420 nm ( Figure 5 ), the characteristic absorption peak is the reaction product of urea and p-dimethylaminobenzaldehyde solution, and the characteristic absorption peak is Figure 4 Consistent, indicating the adoption of Figure 1 The device shown successfully synthesized urea.

[0051] In summary, according to the urea synthesis method proposed in this embodiment, the entire synthesis process can be carried out at room temperature and pressure (referring to pressure), does not require a catalyst, saves energy, and is green and pollution-free.

[0052] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "examples," "specific examples," or "some examples" means that a specific feature, structure, material, or characteristic described in conjunction with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0053] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A method for synthesizing urea, characterized in that: At room temperature and pressure, nitrogen and carbon dioxide gas at a flow rate of 0.1L / min are introduced into water. The humidified mixed gas flows into the discharge reaction chamber through a pipe. A high voltage of 4kV is applied to the discharge array needle plate, causing the generated urea free radical cations to be quickly adsorbed into the stainless steel tank to produce urea. The discharge reaction chamber is provided with a discharge array needle plate and a stainless steel tank in opposite positions. The discharge array needle plate is connected to the positive electrode of the high-voltage power supply, and the stainless steel tank is connected to the negative electrode of the high-voltage power supply. A reaction space is defined between the discharge array needle plate and the stainless steel tank, and the mixed gas is introduced into the reaction space. The discharge array needle board is made by welding tungsten needles on a PCB perforated board. The spacing between needles on the discharge array needle board is between 3 and 8 mm, and the curvature radius of the needle tip is between 0.01 and 0.1 mm.

2. A method for synthesizing urea, characterized in that: At room temperature and pressure, nitrogen gas and carbon dioxide gas at a flow rate of 0.2L / min are introduced into water. The humidified mixed gas flows into the discharge reaction chamber through a pipe. A high voltage of 5kV is applied to the discharge array needle plate, causing the generated urea free radical cations to be quickly adsorbed into the stainless steel tank to produce urea. The discharge reaction chamber is provided with a discharge array needle plate and a stainless steel tank in opposite positions. The discharge array needle plate is connected to the positive electrode of the high-voltage power supply, and the stainless steel tank is connected to the negative electrode of the high-voltage power supply. A reaction space is defined between the discharge array needle plate and the stainless steel tank, and the mixed gas is introduced into the reaction space. The discharge array needle board is made by welding tungsten needles on a PCB perforated board. The spacing between needles on the discharge array needle board is between 3 and 8 mm, and the curvature radius of the needle tip is between 0.01 and 0.1 mm.

3. A method for synthesizing urea, characterized in that: At room temperature and pressure, nitrogen gas and carbon dioxide gas at a flow rate of 0.3L / min are introduced into water. The humidified mixed gas flows into the discharge reaction chamber through a pipe. A high voltage of 6kV is applied to the discharge array needle plate, causing the generated urea free radical cations to be quickly adsorbed into the stainless steel tank to produce urea. The discharge reaction chamber is provided with a discharge array needle plate and a stainless steel tank in opposite positions. The discharge array needle plate is connected to the positive electrode of the high-voltage power supply, and the stainless steel tank is connected to the negative electrode of the high-voltage power supply. A reaction space is defined between the discharge array needle plate and the stainless steel tank, and the mixed gas is introduced into the reaction space. The discharge array needle board is made by welding tungsten needles on a PCB perforated board. The spacing between needles on the discharge array needle board is between 3 and 8 mm, and the curvature radius of the needle tip is between 0.01 and 0.1 mm.

4. A method for synthesizing urea according to any one of claims 1 to 3, characterized in that: A urea detection developer or water or other absorbent solution for enriching urea is also placed in the discharge reaction chamber.

5. A method for synthesizing urea according to claim 4, characterized in that, The urea detection color developing agent is p-dimethylaminobenzaldehyde or diacetyl oxime.

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