CN112174166A

CN112174166A - Method for preparing high-purity ammonia

Info

Publication number: CN112174166A
Application number: CN202011132561.9A
Authority: CN
Inventors: 金先波; 王志勇; 胡杨
Original assignee: Wuhan University WHU
Current assignee: Wuhan University WHU
Priority date: 2020-10-21
Filing date: 2020-10-21
Publication date: 2021-01-05

Abstract

The invention provides a method for preparing high-purity ammonia. Mixing metal nitride (AxNy) and anhydrous ammonium salt, heating for reaction at the reaction temperature of 473-. The method adopts solid-solid reaction, the prepared ammonia gas is dry and is the only gaseous product, and the ammonia gas is hardly decomposed in the preparation process, so that the contents of water, nitrogen and hydrogen in the product are extremely low, and the high-purity ammonia is the only gaseous product. The method is simple to operate, and the high-purity ammonia can be quickly prepared only by heating.

Description

Method for preparing high-purity ammonia

Technical Field

The invention belongs to the field of chemical industry, and particularly relates to a method for preparing high-purity ammonia.

Background

The modern microelectronics and optoelectronics industries are developing on nitrides, especially gallium nitride (GaN) and silicon nitride (Si)₃N₄) Higher quality requirements are imposed. GaN is a new generation of light emitting diode material, and trimethyl gallium (Ga (CH) is mainly adopted at present₃)₃) And high purity ammonia (NH)₃) And (3) reaction preparation. Si₃N₄As an insulating layer, the organic electroluminescent material is widely applied to the fields of large-scale integrated circuits, liquid crystal displays, solar cells and the like. Si₃N₄Is carried out by high-purity ammonia (NH)₃) With Silane (SiH)₄) And (3) reaction preparation. The purity of ammonia has a very significant impact on these preparations. In the case of GaN, if the ammonia gas contains 3ppm of water or oxygen in MOCVD, the wavelength of the light emitted from the epitaxial wafer prepared therefrom will be that ofCannot be controlled; in the preparation of Si₃N₄In the case of ammonia containing 50ppm of water or oxygen, only SiO silicon oxide is formed₂Without generating Si₃N₄。

At present, high-purity ammonia is industrially prepared by synthesizing ammonia at high temperature and high pressure, wherein a large amount of unreacted nitrogen and hydrogen impurities are contained, the impurities are removed by twice rectification in a rectifying tower, and trace water is further removed by a multi-stage absorber, so that the high-purity ammonia is obtained. The preparation process is long, the equipment is complex and the preparation cost is high.

There are also other synthetic methods for ammonia synthesis, such as the production of ammonia gas by the reaction of ammonium chloride with calcium hydroxide, by the reaction of lithium nitride with water, etc., but these methods produce products that contain large amounts of water that are difficult to remove.

Therefore, the problems of high energy consumption, harsh reaction conditions, complex process and the like exist in the preparation of high-purity ammonia at present, and the development of a new technology for preparing high-purity ammonia economically, environmentally and rapidly and efficiently is urgently needed.

Disclosure of Invention

Aiming at the defects in the prior art, the invention provides a method for preparing high-purity ammonia. High-purity ammonia free of nitrogen, hydrogen, water and other impurities is directly prepared by reacting metal nitride with anhydrous ammonium salt.

In order to achieve the purpose, the invention adopts the following technical scheme:

a method for preparing high-purity ammonia comprises the steps of mixing metal nitride AxNy with anhydrous ammonium salt, carrying out heating reaction at the reaction temperature of 473-973K, and collecting a gas product after cooling and dedusting to obtain the high-purity ammonia.

In the metal nitride AxNy, A is one or more of alkaline earth metal or alkali metal, and x and y are natural numbers of 1-5.

Preferably, the metal nitride AxNy is Mg₃N₂、LiN₃、Ca₃N₂、Ba₃N₂One or more of them.

The anhydrous ammonium salt is (NH)₄)₂SO₄、NH₄HSO₄、NH₄H₂PO₄、(NH₄)₂HPO₄、(NH₄)₂S、NH₄HS and ammonium halide.

The invention has the following beneficial effects:

the chemical principle of the preparation method of the high-purity ammonia provided by the invention is to prepare the ammonia gas through solid-solid double decomposition reaction, and the prepared ammonia gas is a dry and only gaseous product. In addition, ammonia gas is hardly decomposed in the preparation process, so that the contents of water, nitrogen and hydrogen in the product are extremely low, and the product is directly high-purity ammonia. The method is simple to operate, and the high-purity ammonia can be quickly prepared only by heating.

Drawings

FIG. 1 is a graph showing the ammonia production rate and yield in terms of magnesium nitride conversion in example 1;

FIG. 2 is the XRD of the solid product of example 1 after 90 minutes of reaction at the indicated temperature;

FIG. 3 is a comparison of a gas chromatogram for detection of hydrogen in the forming gas in example 5 with a standard map of hydrogen.

Detailed Description

The features and advantages of the present invention will be further understood from the following detailed description taken in conjunction with the accompanying drawings. The examples provided are merely illustrative of the method of the present invention and do not limit the remainder of the disclosure in any way.

In the invention, the proportion of the used amount only influences the amount of the ammonia produced by the reaction, and the set temperature and time required for completely releasing the ammonia. Generally, the amount is 1:1 stoichiometric, which results in 100% release of nitrogen from the metal nitride as ammonia.

Example 1

Weighing 0.83g of magnesium nitride and 2.64g of anhydrous ammonium chloride in a glove box, uniformly mixing, heating to 373, 473, 573, 673 or 773K under a sealed condition for 20, 30, 50, 80 or 90 minutes, wherein ammonia gas is generated, and the amount of the prepared ammonia gas after the reaction at 773K for about 80 minutes is equivalent to the theoretical yield after the magnesium nitride is completely reacted.

Example 2

Weighing 0.83g of magnesium nitride and 8g of anhydrous ammonium chloride in a glove box, uniformly mixing, heating to 673K under a sealed condition, reacting for 2 hours, collecting a gas product of the reaction, and analyzing to show that the amount of the prepared ammonia gas is equivalent to the theoretical yield of the completely reacted magnesium nitride.

Example 3

0.83g of magnesium nitride and 2.64g of anhydrous ammonium chloride are weighed in a glove box and uniformly mixed, the mixture is heated to 873K under a sealed condition for 1 hour, and the gas product of the reaction is collected, and analysis shows that the amount of the prepared ammonia gas is equivalent to the theoretical yield of the completely reacted magnesium nitride.

Example 4

0.302g of high-purity magnesium nitride and 1g of high-purity anhydrous ammonium chloride are weighed in a glove box, then uniformly mixed, heated to 673K under a sealed condition, and a reaction gas product is sealed in a quartz tube with a gas valve. After reacting for 30 minutes, opening the gas valve, and introducing the gas into the optical cavity through the conduit to ring down the moisture analyzer for testing the moisture content. The test results showed a water content of 5 ppb.

Example 5

0.302g of high-purity magnesium nitride and 1g of high-purity anhydrous ammonium chloride are weighed in a glove box, then uniformly mixed, heated to 673K under a sealed condition, and a reaction gas product is sealed in a quartz tube with a gas valve. After reacting for 60 minutes, introducing the gaseous product into a sulfuric acid solution by using argon, completely absorbing ammonia gas, analyzing the amount of ammonia, and introducing tail gas into a gas chromatograph to measure the hydrogen content. Analysis shows that the amount of the prepared ammonia gas is equivalent to the theoretical yield of the magnesium nitride after 80 percent of reaction; the concentration of hydrogen in the product was less than 1ppm, indicating NH was formed₃Hardly decomposed, so that N in the product₂Gas and H₂The content is extremely low. At the temperature of 673K, the prepared ammonia gas has low thermal decomposition rate, and directly reaches the standard of electronic grade high-purity ammonia.

Example 6

Weighing 0.302g of high-purity magnesium nitride and 1g of high-purity anhydrous ammonium chloride in a glove box, uniformly mixing, heating to 773K under a sealed condition, and sealing a reaction gas product in the glove boxA quartz tube with a gas valve. After 80 minutes of reaction, the gaseous product is introduced into sulfuric acid solution by argon gas, the ammonia gas is completely absorbed, the ammonia amount is analyzed, and the tail gas is introduced into a gas chromatograph to measure the hydrogen content. Analysis shows that the amount of the prepared ammonia gas is equivalent to the theoretical yield of the magnesium nitride after complete reaction; the concentration of hydrogen in the product was about 30ppm, indicating NH₃The decomposition rate of (A) is only about 0.003%. At 773K above, because the ammonia generated by ammonia decomposition is not theoretically 6N, 7N electronic grade high-purity ammonia, nitrogen (boiling point 77.35K) and hydrogen (boiling point 20.27K) can be removed by simple rectification, thereby obtaining electronic grade high-purity ammonia (boiling point 239.8K).

Example 7

Weighing 0.153g of lithium nitride and 1.4g of anhydrous ammonium chloride in a glove box, uniformly mixing, heating to 773K under a sealed condition for 1 hour, collecting a reaction gas product, and analyzing to show that the amount of prepared ammonia gas is equivalent to the theoretical yield of the lithium nitride after complete reaction.

Example 8

Weighing 0.133g of barium nitride and 0.1g of anhydrous ammonium chloride in a glove box, uniformly mixing, carrying out temperature programming heating to 973K at the speed of 10 ℃/min under a sealed condition, wherein the heating time is 1 hour, cooling, filtering and collecting a reacted gas product, and analysis shows that the amount of prepared ammonia gas is equivalent to the theoretical yield of lithium nitride after complete reaction.

Example 9

Weighing 0.233g of calcium nitride and 0.954g of anhydrous ammonium bromide in a glove box, uniformly mixing, carrying out temperature programming heating to 973K at the speed of 10 ℃/min under a sealed condition, wherein the heating time is 1 hour, cooling, filtering and collecting a reacted gas product, and analysis shows that the amount of the prepared ammonia gas is equivalent to the theoretical yield of the lithium nitride after complete reaction.

Example 10

Weighing 0.09g of magnesium nitride and 0.363g of anhydrous ammonium sulfate in a glove box, uniformly mixing, heating to 673K under a sealed condition for 3 hours, collecting a reaction gas product, and analyzing to show that the amount of the prepared ammonia gas is equivalent to the theoretical yield of the lithium nitride after the lithium nitride completely reacts.

Example 11

Weighing 0.09g of magnesium nitride, 0.16g of lithium nitride, 0.37g of anhydrous ammonium sulfate and 1.43g of anhydrous ammonium chloride in a glove box, uniformly mixing, heating to 673K under a sealed condition for 2 hours, collecting a reaction gas product, and analyzing to show that the amount of prepared ammonia gas is equivalent to the theoretical yield of the lithium nitride after complete reaction.

Example 12

Weighing 0.09g of magnesium nitride, 0.16g of lithium nitride and 2.63g of anhydrous ammonium chloride in a glove box, uniformly mixing, heating to 673K under a sealed condition for 1 hour, collecting a reaction gas product, and analyzing to show that the amount of prepared ammonia gas is equivalent to the theoretical yield of the lithium nitride after complete reaction.

Example 13

Weighing 0.11g of magnesium nitride, 0.2g of anhydrous ammonium sulfate and 0.4g of anhydrous ammonium chloride in a glove box, uniformly mixing, heating to 673K under a sealed condition for 2 hours, filtering, dedusting and collecting a reaction gas product, wherein analysis shows that the amount of the prepared ammonia gas is equivalent to the theoretical yield of the lithium nitride after complete reaction.

Claims

1. A method for preparing high-purity ammonia, which is characterized by comprising the following steps: mixing the metal nitride AxNy with anhydrous ammonium salt, then carrying out heating reaction at the reaction temperature of 473-973K, and collecting the gas product after cooling and dedusting to obtain the high-purity ammonia.

2. The method for producing high-purity ammonia according to claim 1, wherein: in the metal nitride AxNy, A is one or more of alkaline earth metal or alkali metal, and x and y are natural numbers of 1-5.

3. The method for producing high-purity ammonia according to claim 1 or 2, wherein: the metal nitride AxNy is Mg₃N₂、LiN₃、Ca₃N₂、Ba₃N₂One or more of them.

4. The method for producing high-purity ammonia according to claim 1, wherein: the anhydrous ammonium salt is (NH)₄)₂SO₄、NH₄HSO₄、NH₄H₂PO₄、(NH₄)₂HPO₄、(NH₄)₂S、NH₄HS and ammonium halide.