Method for efficiently synthesizing ammonia through chemical looping

Abstract

The invention discloses a method for efficiently synthesizing ammonia through a chemical chain, and belongs to the technical field of novel chemical materials. The method comprises the following steps: 1) placing a metal nitride in a ball milling reactor for ball milling, introducing hydrogen into the ball milling reactor at normal pressure to start an ammonia production reaction, with the gas hourly space velocity of the introduced hydrogen being 1000 h <-1 >; (2) after the reaction in the step (1) is completed, nitrogen is introduced into the ball milling reactor, ball milling is carried out under normal pressure for a nitrogen fixation reaction, a nitride catalyst is prepared through regeneration, and the gas hourly space velocity of the introduced nitrogen is 1000 h <-1 >; (3) repeating the step (1) and the step (2) on the regenerated nitride catalyst in the step (2), and continuously synthesizing ammonia. The ammonia synthesis method adopting the metal nitride catalyst has the advantages that the energy consumption is obviously lower than that of a traditional ammonia synthesis process, the safety is good, the cost is low, and ammonia can be circularly produced.

Description

Technical Field

[0001] The invention belongs to the technical field of new chemical materials, and in particular relates to a method for synthesizing ammonia through a high-efficiency chemical chain. Background Art

[0002] Synthetic ammonia is one of the most important chemical processes in modern industry. Its product is ammonia gas ( ) is a core raw material in the fields of fertilizers, explosives, and medicines. It is also a clean energy carrier that has attracted much attention in recent years (such as liquid ammonia hydrogen storage). Traditional ammonia synthesis technology is dominated by the Haber-Bosch process. Since its industrialization in the early 20th century, although the process has been continuously optimized, its core reaction mechanism still relies on high temperature (400-500°C), high pressure (15-25 MPa) conditions and iron-based catalysts, resulting in huge energy consumption (about 1-2% of the world's total energy consumption) and significant carbon dioxide emissions (about 1.8 tons per ton of ammonia). ). In addition, this method requires fossil fuels (such as natural gas) as the hydrogen source, further exacerbating the carbon footprint and resource unsustainability issues.

[0003] In the field of synthetic ammonia technology, inorganic nitrogen-containing compounds have become a research hotspot due to their rich active sites and excellent kinetic properties, mainly including metal nitrides, nitrogen oxides, nitrogen hydrides and (sub)amino compounds. There are currently three types of chemical chain synthesis ammonia systems: (1) metal nitride-oxide chemical chain synthesis of ammonia, which faces technical bottlenecks such as high reaction temperature (>1000 ℃) and low energy efficiency, and the reduction and regeneration method of metal oxides still needs to be broken through; (2) nitrogen-poor-nitrogen-rich nitride chemical chain synthesis of ammonia, with For example, studies have shown that only 3.1% of the lattice nitrogen can participate in the hydrogenation reaction to generate , about 73% of the lattice nitrogen is By developing Fe-Mn composite nitrogen carriers, the defects of the difficulty of nitridation of single Fe-based materials and the low efficiency of ammonia of Mn-based materials have been partially overcome. Although the system shows application potential in the medium temperature range of 500-700℃, it still needs to overcome the core problems such as low lattice nitrogen conversion rate and insufficient nitrogen fixation capacity of nitrogen-poor phase; (3) Hydride-imino compounds for chemical chain synthesis of ammonia, such as TM-LiH, The system can achieve efficient ammonia synthesis at 300 °C and 1 bar. However, the AH bond in the metal hydride is easily deactivated by hydrolysis, and the catalyst has safety hazards such as spontaneous combustion and explosion, which seriously restricts the industrial application of the system. Therefore, how to develop a newer and milder ammonia synthesis process and solve the problem of nitrogen fixation by nitrogen carriers after denitrification is one of the key issues that need to be solved in the field of ammonia synthesis technology. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for efficient chemical-looping ammonia synthesis. This method uses metal nitrides to react with hydrogen to synthesize ammonia, providing a new reaction interface, and then reacts with nitrogen to regenerate the metal nitrides to continuously produce ammonia, effectively improving the reaction rate and the ammonia synthesis amount, and having obvious industrial value.

[0005] To solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0006] A method for efficient chemical-looping ammonia synthesis, comprising the following steps:

[0007] 1) Place the metal nitride in a ball-milling reactor for ball milling. Under normal pressure, introduce hydrogen into the ball-milling reactor to start the ammonia production reaction. Among them, the gas hourly space velocity of the introduced hydrogen is 1000 h -1 ;

[0008] 2) After the reaction in step 1) is completed, introduce nitrogen into the ball-milling reactor, and carry out nitrogen fixation reaction by ball milling under normal pressure to regenerate and prepare a nitride catalyst. Among them, the gas hourly space velocity of the introduced nitrogen is 1000 h -1 ;

[0009] 3) Repeat step 1) and step 2) with the nitride catalyst regenerated in step 2) to continuously synthesize ammonia.

[0010] Further, the metal nitride is one or a mixture of two of tungsten nitride and molybdenum nitride.

[0011] Further, the reaction time in step 1) is 1 - 10 h.

[0012] Further, the reaction time in step 2) is 2 - 10 h.

[0013] Further, the rotation speed of the ball mill in step 1) and step 2) is 50 - 1500 r / min.

[0014] Further, the reaction temperature in step 1) and step 2) is 20 - 100 °C.

[0015] Further, the reaction pressure in step 1) and step 2) is 1 bar.

[0016] Compared with the prior art, the present invention has the following advantages:

[0017] (1) The ammonia synthesis rate of the metal nitride catalyst adopted by the present invention is significantly better than that of the traditional ammonia synthesis catalyst, and the process is simple, the cost is low, and the ammonia synthesis rate is high at low temperature and normal pressure.

[0018] (2) In the catalytic reaction of the present invention, the reaction of metal nitride with hydrogen to synthesize ammonia provides a new reaction interface, and then reacts with nitrogen to regenerate the metal nitride to continuously produce ammonia, effectively improving the reaction rate. Description of the Drawings

[0019] Figure 1 It is a schematic diagram of the reaction device for chemical-looping ammonia synthesis of this application. Specific Embodiments

[0020] The following further clarifies the present invention in conjunction with specific embodiments. The embodiments are implemented on the premise of the technical solution of the present invention. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention.

[0021] In the following examples, the Nessler reagent spectrophotometry was used to analyze the ammonia yield (GB / T 14668-93).

[0022] The atmospheric pressure in the following examples is 1 bar.

[0023] The calculation formula for the total amount of ammonia synthesis in the following examples is: ammonia production rate = total amount of ammonia synthesis / total reaction time of ammonia production reaction.

[0024] Example 1

[0025] A method for highly efficient chemical-looping ammonia synthesis includes the following steps:

[0026] (1) Weigh 10 g of tungsten nitride powder catalyst. Use a self-made ball-milling reactor as the reaction device. The rotation speed of the ball mill is 1500 r / min, the reaction temperature is 20 °C, and hydrogen is introduced at atmospheric pressure to start the ammonia production reaction. The gas hourly space velocity (GHSV) of hydrogen is 1000 h -1 , and stop introducing hydrogen after reacting for 1 h, and the reaction ends;

[0027] (2) After the ammonia production reaction ends, introduce nitrogen into the ball-milling reactor. After the ball-milling reactor is in an environment of introducing nitrogen at atmospheric pressure, carry out the nitrogen fixation reaction. The gas hourly space velocity (GHSV) of nitrogen is 1000 h -1 , the rotation speed of the ball mill is 300 r / min, the reaction temperature is 20 °C, and ball-mill for 10 h at atmospheric pressure to regenerate the reaction by-product metal tungsten and nitrogen into tungsten nitride catalyst in step 1);

[0028] (3) Repeat steps 1) and 2) for the tungsten nitride catalyst obtained in step 2), and carry out the cyclic ammonia production reaction. After the catalyst is recycled 5 times, use the Nessler reagent spectrophotometry to analyze the ammonia yield. The total amount of ammonia synthesis in 5 reactions is 6 mmol, and the ammonia production rate per gram of catalyst is 0.12 mmol / h.

[0029] Example 2

[0030] A method for efficient chemical-looping ammonia synthesis, comprising the following steps:

[0031] (1) Weigh 10 g of tungsten nitride powder catalyst, use a self-made ball-milling reactor as the reaction device, the rotation speed of the ball mill is 50 r / min, the reaction temperature is 100 °C, and hydrogen is introduced at atmospheric pressure to start the ammonia production reaction. The gas hourly space velocity (GHSV) of hydrogen is 1000 h -1 , and stop introducing hydrogen after reacting for 5 h, and the reaction ends;

[0032] (2) After the ammonia production reaction ends, introduce nitrogen into the ball-milling reactor, and carry out the nitrogen fixation reaction after the ball-milling reactor is in an environment of introducing nitrogen at atmospheric pressure. The gas hourly space velocity (GHSV) of nitrogen is 1000 h -1 , the rotation speed of the ball mill is 50 r / min, the reaction temperature is 100 °C, and ball-mill for 2 h at atmospheric pressure to regenerate the reaction by-product tungsten metal and nitrogen into tungsten nitride catalyst in step (1);

[0033] (3) Repeat step (1) and step (2) for the tungsten nitride catalyst obtained in step (2) to carry out the cyclic ammonia production reaction. After the catalyst is recycled 5 times, the ammonia yield is analyzed by the Nessler reagent spectrophotometry method. The total amount of ammonia synthesis in 5 reactions is 47.5 mmol, and the ammonia production rate per gram of catalyst is calculated to be 0.19 mmol / h.

[0034] Example 3

[0035] A method for efficient chemical-looping ammonia synthesis, comprising the following steps:

[0036] (1) Weigh 10 g of tungsten nitride powder catalyst, use a self-made ball-milling reactor as the reaction device, the rotation speed of the ball mill is 150 r / min, the reaction temperature is 60 °C, and hydrogen is introduced at atmospheric pressure to start the ammonia production reaction. The gas hourly space velocity (GHSV) of hydrogen is 1000 h -1 , and stop introducing hydrogen after reacting for 5 h, and the reaction ends;

[0037] (2) After the ammonia production reaction ends, introduce nitrogen into the ball-milling reactor, and carry out the nitrogen fixation reaction after the ball-milling reactor is in an environment of introducing nitrogen at atmospheric pressure. The gas hourly space velocity (GHSV) of nitrogen is 1000 h -1 , the rotation speed of the ball mill is 150 r / min, the reaction temperature is 60 °C, and ball-mill for 6 h at atmospheric pressure to regenerate the reaction by-product tungsten metal and nitrogen into tungsten nitride catalyst in step (1);

[0038] (3) Repeat steps (1) and (2) with the tungsten nitride catalyst obtained in step (2) for cyclic ammonia production reaction. After the catalyst is recycled 5 times, the ammonia yield is analyzed by Nessler's reagent spectrophotometry. The total amount of ammonia synthesis in 5 reactions is 62.5 mmol. After calculation, the ammonia production rate per gram of catalyst is 0.25 mmol / h.

[0039] Example 4

[0040] A method for highly efficient chemical-looping ammonia synthesis, comprising the following steps:

[0041] (1) Weigh 10 g of molybdenum nitride powder catalyst, use a self-made ball-milling reactor as the reaction device, the rotational speed of the ball mill is 1000 r / min, the reaction temperature is 80 °C, and hydrogen is introduced at atmospheric pressure to start the ammonia production reaction. The gas hourly space velocity (GHSV) of hydrogen is 1000 h -1 . After reacting for 1 h, stop introducing hydrogen, and the reaction ends;

[0042] (2) After the ammonia production reaction ends, introduce nitrogen into the ball-milling reactor. After the ball-milling reactor is in an environment of introducing nitrogen at atmospheric pressure, carry out the nitrogen fixation reaction. The gas hourly space velocity (GHSV) of nitrogen is 1000 h -1 . The rotational speed of the ball mill is 1000 r / min, the reaction temperature is 80 °C, and ball-mill for 8 h at atmospheric pressure to regenerate the reaction by-product metal molybdenum and nitrogen into molybdenum nitride catalyst;

[0043] (3) Repeat steps (1) and (2) with the molybdenum nitride catalyst obtained in step (2) for cyclic ammonia production reaction. After the catalyst is recycled 5 times, the ammonia yield is analyzed by Nessler's reagent spectrophotometry. The total amount of ammonia synthesis in 5 reactions is 11.5 mmol. After calculation, the ammonia production rate per gram of catalyst is 0.23 mmol / h.

[0044] Example 5

[0045] A method for highly efficient chemical-looping ammonia synthesis, comprising the following steps:

[0046] (1) Weigh 10 g of molybdenum nitride powder catalyst, use a self-made ball-milling reactor as the reaction device, the rotational speed of the ball mill is 150 r / min, the reaction temperature is 40 °C, and hydrogen is introduced at atmospheric pressure to start the ammonia production reaction. The gas hourly space velocity (GHSV) of hydrogen is 1000 h -1 . After reacting for 10 h, stop introducing hydrogen, and the reaction ends;

[0047] (2) After the ammonia production reaction ends, introduce nitrogen into the ball-milling reactor. After the ball-milling reactor is in an environment of introducing nitrogen at atmospheric pressure, carry out the nitrogen fixation reaction. The gas hourly space velocity (GHSV) of nitrogen is 1000 h -1, the ball mill rotates at 1500 r / min, the reaction temperature is 40 °C, and ball milling is carried out under normal pressure for 10 h. The reaction by-product metal molybdenum and nitrogen in step 1) for ammonia production are regenerated into molybdenum nitride catalyst;

[0048] (3) Repeat step 1) and step 2) with the molybdenum nitride catalyst obtained in step 2) to carry out the cyclic ammonia production reaction. After the catalyst is recycled 5 times, the ammonia yield is analyzed by the Nessler reagent spectrophotometry method. The total amount of ammonia synthesis in 5 reactions is 140 mmol. After calculation, the ammonia generation rate per gram of catalyst is 0.28 mmol / h.

[0049] Example 6

[0050] A method for highly efficient chemical-looping ammonia synthesis, comprising the following steps:

[0051] (1) Weigh 5 g of tungsten nitride powder catalyst and 5 g of molybdenum nitride powder catalyst. Use a self-made ball mill reactor as the reaction device. The ball mill rotates at 1500 r / min, the reaction temperature is 40 °C, and hydrogen is introduced under normal pressure to start the ammonia production reaction. The gas hourly space velocity (GHSV) of hydrogen is 1000 h -1 , stop introducing hydrogen after reacting for 3 h, and the reaction ends;

[0052] (2) After the ammonia production reaction ends, introduce nitrogen into the ball mill reactor. After the ball mill reactor is in an environment of introducing nitrogen under normal pressure, carry out the nitrogen fixation reaction. The gas hourly space velocity (GHSV) of nitrogen is 1000 h -1 , the ball mill rotates at 1500 r / min, the reaction temperature is 40 °C, and ball milling is carried out under normal pressure for 10 h. The reaction by-products metal tungsten and molybdenum in step 1) for ammonia production and nitrogen are regenerated into tungsten nitride and molybdenum nitride catalysts;

[0053] (3) Repeat step 1) and step 2) with the tungsten nitride and molybdenum nitride catalysts obtained in step 2) to carry out the cyclic ammonia production reaction. After the catalyst is recycled 5 times, the ammonia yield is analyzed by the Nessler reagent spectrophotometry method. The total amount of ammonia synthesis in 5 reactions is 49.5 mmol. After calculation, the ammonia generation rate per gram of catalyst is 0.33 mmol / h.

[0054] The above is only the preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A method for synthesizing ammonia by an efficient chemical chain, characterized in that: The following steps are involved: 1) The metal nitride is placed in a ball mill reactor for ball milling, and hydrogen is introduced into the ball mill reactor under normal pressure to start the ammonia production reaction, wherein the gas hourly space velocity of the hydrogen is 1000 h -1 ; 2) After the reaction in step 1) is completed, nitrogen is introduced into the ball milling reactor, and the ball milling is performed under normal pressure to carry out nitrogen fixation reaction, and the nitride catalyst is regenerated, wherein the gas hourly space velocity of the nitrogen is 1000 h -1 ; 3) Repeating steps 1) and 2) with the nitride catalyst regenerated in step 2) to continuously synthesize ammonia.

2. The method for synthesizing ammonia by a highly efficient chemical chain according to claim 1, characterized in that: The metal nitride is one of tungsten nitride and molybdenum nitride, or a mixture of the two.

3. The method for synthesizing ammonia by a highly efficient chemical chain according to claim 1, characterized in that: The reaction time in step 1) is 1-10 h.

4. The method for synthesizing ammonia by efficient chemical chaining according to claim 1, characterized in that: The reaction time in step 2) is 2-10 h.

5. The method for synthesizing ammonia by efficient chemical chaining according to claim 1, characterized in that: In the step 1) and the step 2), the rotation speed of the ball mill is 50-1500 r / min.

6. The method for synthesizing ammonia by efficient chemical chaining according to claim 1, characterized in that: The reaction temperature in step 1) and step 2) is 20-100°C.

7. The method for synthesizing ammonia by efficient chemical chaining according to claim 1, characterized in that: The reaction pressure in step 1) and step 2) is 1 bar.

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