Method for synthesizing urea based on coupling reaction of metal nitride and carbon dioxide

Abstract

The invention relates to a method for synthesizing urea based on a coupling reaction of metal nitride and carbon dioxide, the metal nitride is any one nitride of Li, Na, K, Be, Mg, Ca, Fe, Co, Ni, Al or Zn, the air pressure of the carbon dioxide is 1-10 bar, the metal nitride and the carbon dioxide are heated to form a compound, the compound is hydrolyzed to form urea, and the urea is prepared by the coupling reaction of the metal nitride and the carbon dioxide. And green and efficient synthesis of urea can be realized.

Description

Technical Field

[0001] The present invention belongs to the field of urea synthesis, and particularly relates to a new method for synthesizing urea based on the coupling reaction of metal nitride and carbon dioxide. Background Art

[0002] At present, the global population is increasing continuously, the world economy is developing continuously, and the human demand for food is increasing day by day. In the agricultural field, in the past century, about 27% of the global population has relied on food grown with nitrogen fertilizers for survival. Urea is regarded as one of the important nitrogen fertilizers due to its high nitrogen content (46%), and it is of great significance in meeting the growing population demand. Urea production belongs to an energy-intensive industry, mainly through the Bosch−Meiser process. This process requires the coupling reaction of NH 3 and CO 2 under high temperature (150~200 °C) and high pressure (130~200 bar) conditions (Yildirim, Ö., Nölker, K., Büker, K., et. al. Chemical conversion of steel mill gases to urea:an analysis of plant capacity. Chemie Ingenieur Technik, 2018, 90(10), 1529-1535). This process also releases a large amount of CO 2 and consumes a large amount of fossil fuels. Specifically, every ton of urea production requires 21~29 GJ of energy consumption and emits an average of 0.7~2.3 tons of CO 2 (Masjedi, S. K., Kazemi, A.,Moeinnadini, M., et. al. Urea production: an absolute environmentalsustainability assessment. Science of the Total Environment, 2024, 908,168225). In addition, the urea synthesis process also requires complex equipment and multiple cycle synthesis steps to improve the conversion efficiency. The traditional urea synthesis process has problems such as high energy consumption, serious pollution and complex process.

[0003] The typical existing technologies for synthesizing urea are as follows: CN105130750B discloses a process for producing low-carbon alcohols from coke oven gas with co-production of urea and liquefied natural gas. The process is that crude coke oven gas is desulfurized and decarbonized to obtain purified coke oven gas, H 2 S is removed for sulfur recovery, and the removed CO 2Urea synthesis is carried out by stripping; the purified coke oven gas is separated, and the separated CH 4 is used as the LNG product; the separated coke oven gas is subjected to lower alcohol synthesis to obtain a gas product and a liquid product of lower mixed alcohols; the liquid product is subjected to alcohol-water separation to obtain a lower alcohol product; the gas product is separated, and the separated CO, CO 2 and other gases are returned to the purification of coke oven gas, and the separated H 2 is combined with nitrogen and then subjected to ammonia synthesis, and the synthesized ammonia and CO 2 from stripping are used for urea synthesis together. The pressure and temperature for synthesizing urea by this method are relatively high, and the energy consumption is high.

[0004] US20200087153A1 discloses a method for co-producing methanol and ammonia and producing urea from a hydrocarbon feed, without discharging the carbon dioxide captured from the methanol or ammonia synthesis gas into the atmosphere, nor using expensive air separation devices and water gas shift devices. The carbon dioxide in the flue gas of the reforming section is removed to convert part or all of the ammonia into urea. However, its pressure reaches dozens of bar.

[0005] US20020035293A1 discloses a method for preparing urea and ammonia reactants by combining the steps of ammonia synthesis gas containing carbon dioxide and converting the synthesis gas into ammonia reactants, and reacting the ammonia reactants with the carbon dioxide in the synthesis gas to form ammonium carbamate and urea products. This method includes further steps before converting the synthesis gas into ammonia reactants: (i) washing the synthesis gas with an aqueous solution of ammonia reactants and forming a solution rich in ammonium carbamate; (ii) removing the excess ammonia reactants from the washed synthesis gas by washing with water and taking out the aqueous solution of ammonia reactants; (iii) purifying the water-washed synthesis gas by removing a reminder amount of water and ammonia; and (iv) introducing the purified synthesis gas into a gas to be converted into ammonia reactants. The pressure for concentrating ammonia in this process usually reaches 15 - 17 kg / cm 2 .

[0006] So far, a technology for simply and efficiently reducing energy consumption and carbon dioxide emissions in synthesizing urea under atmospheric pressure conditions has not been reported; the present invention aims to solve the above problems. Summary of the Invention

[0007] To solve the disadvantages and deficiencies of the prior art, the present invention provides a method for synthesizing urea based on the coupling reaction of metal nitride and carbon dioxide.

[0008] To achieve the above object, the present application proposes to form a compound by reacting metal nitride with carbon dioxide under heating conditions, and then hydrolyzing the compound to form urea.

[0009] Specifically, to achieve the above object, the present invention is realized by at least one of the following technical solutions.

[0010] A method for synthesizing urea based on the coupling reaction of metal nitride and carbon dioxide provided by the present invention comprises the following steps: Step 1: Using metal nitride and carbon dioxide as raw materials, heating and reacting in a reaction kettle to obtain mixture solid 1; Step 2: Reacting mixture solid 1 with a to obtain urea.

[0011] Preferably, in step 1, the metal nitride is a nitride such as Li, Na, K, Be, Mg, Ca, Fe, Co, Ni, Al or Zn.

[0012] Preferably, in step 1, the air pressure of carbon dioxide is 1-10 bar, preferably 1-3 bar.

[0013] Preferably, in step 1, the mass of the metal nitride is 0.001-10000 g, preferably 0.005-1.0 g.

[0014] Preferably, in step 1, the heating temperature is 100-500 °C, preferably 200-400 °C.

[0015] Preferably, in step 1, the heating time is 0.1-6 h.

[0016] Preferably, in step 1, the volume of the reaction kettle is 10 cm 3 ~10 m 3 .

[0017] Preferably, in step 2, the solvent is water vapor, deionized water, acidic solution, neutral solution or alkaline solution, preferably water vapor, hydrochloric acid solution, sulfuric acid solution, deionized water.

[0018] Further, in step 2, if a is a solution, the solute concentration of solution a is 0.01-12 mol / L.

[0019] Advantages of the present invention: The present invention can realize the reaction of heating metal nitride and carbon dioxide under atmospheric pressure conditions, and then obtain urea through simple hydrolysis. The equipment is simple, the synthesis steps are few, and the conversion rate of metal nitride to urea is high; a new idea for synthesizing urea is proposed. Description of the drawings

[0020] Figure 1 It is a schematic diagram of the reaction kettle for the method of synthesizing urea based on the coupling reaction of metal nitride and carbon dioxide.

[0021] Figure 2The conversion rate of urea under different qualities of lithium nitride.

[0022] Figure 3 is the yield of urea for Li 3 N under different pressures.

[0023] Figure 4 is the yield of urea for Mg 3 N 2 and Fe x N under different pressures.

[0024] In the figure: 1, pressure gauge; 2, carbon dioxide inlet pipe; 3, stainless steel outer kettle; 4, quartz inner liner; 5, metal nitride; 6, carbon dioxide outlet pipe. Specific implementation manner Example 1

[0025] A method for synthesizing urea based on the coupling reaction of metal nitride and carbon dioxide in this example uses 40 mg of Li 3 N, the pressure of CO 2 is 1 bar, the heating temperature is 370 °C, the heating duration is 1.0 h, and solution a is 1.5 mol / L HCl solution. It specifically includes the following steps: (1) First, place 40 mg of Li 3 N in a reaction kettle with a volume of 20 cm 3 and fill the reaction kettle with 1 bar of CO 2 . (2) Place the reaction kettle on a heating platform and heat it at 370 °C for 1.0 h to obtain mixture solid 1; (3) React the mixture solid 1 with 1.5 mol / L HCl solution to obtain a urea solution. Example 2

[0026] This example uses 5 mg of Li 3 N, the pressure of CO 2 is 1 bar, the heating temperature is 370 °C, the heating duration is 1.0 h, and solvent a is 1.5 mol / L HCl solution. It specifically includes the following steps: (1) First, place 5 mg of Li 3 N in a reaction kettle with a volume of 20 cm 3 and fill the reaction kettle with 1 bar of CO 2 .

[0027] (2) Place the reaction kettle on a heating platform and heat it at 370 °C for 1.0 h to obtain mixture solid 1; (3) React the mixture solid 1 with 1.5 mol / L HCl solution to obtain a urea solution. Example 3

[0028] This example uses 20 mg of Li 3 N, CO 2 The pressure is 1 bar, the heating temperature is 370 °C, the heating duration is 1.0 h, and the solvent a is 1.5 mol / L HCl solution. The specific steps are as follows: (1) First, place 20 mg of Li 3 N in a reaction kettle with a volume of 20 cm 3 and fill the reaction kettle with 1 bar of CO 2 ; (2) Place the reaction kettle on a heating platform and heat it at 370 °C for 1.0 h to obtain mixture solid 1; (3) React the mixture solid 1 with 1.5 mol / L HCl solution to obtain a urea solution. Example 4

[0029] This example uses 60 mg of Li 3 N, CO 2 The pressure is 1 bar, the heating temperature is 370 °C, the heating duration is 1.0 h, and the solvent a is 1.5 mol / L HCl solution. The specific steps are as follows: (1) First, place 60 mg of Li 3 N in a reaction kettle with a volume of 20 cm 3 and fill the reaction kettle with 1 bar of CO 2 ; (2) Place the reaction kettle on a heating platform and heat it at 370 °C for 1.0 h to obtain mixture solid 1; (3) React the mixture solid 1 with 1.5 mol / L HCl solution to obtain a urea solution. Example 5

[0030] This example uses 5 mg of Li 3 N, CO 2 The pressure is 2 bar, the heating temperature is 370 °C, the heating duration is 1.0 h, and the solvent a is 1.5 mol / L HCl solution. The specific steps are as follows: (1) First, place 5 mg of Li 3 N in a reaction kettle with a volume of 20 cm 3 and fill the reaction kettle with 2 bar of CO 2 ; (2) Place the reaction kettle on a heating platform and heat it at 370 °C for 1.0 h to obtain solid mixture 1; (3) React solid mixture 1 with 1.5 mol / L HCl solution to obtain a urea solution. Example 6

[0031] This example uses 5 mg of Li 3 N, CO 2 The pressure is 3 bar, the heating temperature is 370 °C, the heating duration is 1.0 h, and the solvent a is 1.5 mol / L HCl solution. The specific steps are as follows: (1) First, place 5 mg of Li 3 N in a reaction kettle with a volume of 20 cm 3 and fill the reaction kettle with 3 bar of CO 2 ; (2) Place the reaction kettle on a heating platform and heat it at 370 °C for 1.0 h to obtain solid mixture 1; (3) React solid mixture 1 with 1.5 mol / L HCl solution to obtain a urea solution. Example 7

[0032] This example uses 40 mg of Mg 3 N 2 , CO 2 The pressure is 3 bar, the heating temperature is 370 °C, the heating duration is 1.0 h, and the solvent a is 1.5 mol / L HCl solution. The specific steps are as follows: (1) First, place 40 mg of Mg 3 N 2 in a reaction kettle with a volume of 20 cm 3 and fill the reaction kettle with 3 bar of CO 2 ; (2) Place the reaction kettle on a heating platform and heat it at 370 °C for 1.0 h to obtain solid mixture 1; (3) React solid mixture 1 with 1.5 mol / L HCl solution to obtain a urea solution. Example 8

[0033] This example uses 40 mg of Fe x N, CO 2 The pressure is 4 bar, the heating temperature is 370 °C, the heating duration is 1.0 h, and the solvent a is 1.5 mol / L HCl solution. The specific steps are as follows: (1) First, place 40 mg of Fe xN is placed in a reactor with a volume of 20 cm 3 and 4 bar of CO is filled into the reactor 2 ; (2) The reactor is placed on a heating platform and heated at 370 °C for 1.0 h to obtain solid mixture 1; (3) React solid mixture 1 with 1.5 mol / L HCl solution to obtain a urea solution. Comparative Example 1

[0034] In this comparative example, 40 mg of Li 3 N, with a CO 2 pressure of 1 bar, a heating temperature of 30 °C, a heating duration of 1.0 h, and solution a being 1.5 mol / L HCl solution. The specific steps are as follows: (1) First, 40 mg of Li 3 N is placed in a reactor with a volume of 20 cm 3 and 1 bar of CO is filled into the reactor 2 ; (2) The reactor is placed on a heating platform and heated at 30 °C for 1.0 h to obtain solid mixture 1; (3) React solid mixture 1 with 1.5 mol / L HCl solution to obtain a solution, and test the urea concentration in the solution.

[0035] The urea solutions provided in Examples 1 - 8 are detected for the component content of urea by the diacetyl monoxime colorimetric method.

[0036] The yields of Li 3 N to urea obtained in Examples 1 - 4 are as Figure 2 shown, and the yields of Li 3 N to urea obtained in Examples 2, 5, and 6 are as Figure 3 shown, and the yields of urea obtained in Examples 7 and 8 are as Figure 4 shown. No urea is generated in Comparative Example 1. It can be seen that the method provided by the present invention realizes urea synthesis using carbon dioxide.

[0037] In summary, the new method for efficient urea synthesis provided by the present invention uses metal nitride and carbon dioxide as reaction sources to synthesize urea under heating conditions. The reaction process is simple, the reaction conditions are mild, it is easy to operate, and can achieve green and efficient synthesis of urea.

[0038] The above embodiments are only preferred exemplary embodiments of the present application, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any person skilled in the art within the technical scope disclosed by the present invention can easily think of development or replacement, which all fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A method for synthesizing urea based on the coupling reaction of metal nitride and carbon dioxide, characterized in that: The steps include: Step 1, using metal nitride and carbon dioxide as raw materials for heating reaction to obtain a mixture solid 1; Step 2, reacting the mixture solid 1 with a to obtain urea; The a is any one of water vapor, deionized water, acidic solution, neutral solution or alkaline solution.

2. The method for synthesizing urea based on the coupling reaction of metal nitride and carbon dioxide according to claim 1, characterized in that: In step 1, the metal nitride is any nitride of Li, Na, K, Be, Mg, Ca, Fe, Co, Ni, Al or Zn.

3. The method for synthesizing urea based on the coupling reaction of metal nitride and carbon dioxide according to any one of claims 1 to 2, characterized in that: In step 1, the gas pressure of the carbon dioxide is 1-100 bar, preferably 1-3 bar.

4. The method for synthesizing urea based on the coupling reaction of metal nitride and carbon dioxide according to any one of claims 1 to 2, characterized in that: In step 1, the mass of the metal nitride is 0.001~10000 g, preferably 0.005~1.0 g.

5. The method for synthesizing urea based on the coupling reaction of metal nitride and carbon dioxide according to any one of claims 1 to 2, characterized in that: In step 1, the heating temperature in the reactor is 100-1000°C, preferably 200-400°C.

6. The method for synthesizing urea based on the coupling reaction of metal nitride and carbon dioxide according to any one of claims 1 to 2, characterized in that: In step 1, the heating time is 0.1 to 10 h.

7. The method for synthesizing urea based on the coupling reaction of metal nitride and carbon dioxide according to any one of claims 1 to 2, characterized in that: In step 1, the volume of the reactor is 10 cm 3 ~10 m 3 .

8. The method for synthesizing urea based on the coupling reaction of metal nitride and carbon dioxide according to any one of claims 1 to 2, characterized in that: In step 2, a is any one of water vapor, hydrochloric acid solution, sulfuric acid solution, and deionized water.

9. The method for synthesizing urea based on the coupling reaction of metal nitride and carbon dioxide according to claim 7, characterized in that: In step 2, a is a solution, and the concentration of the solute is 0.01-12 mol / L.

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