Purifying method for nitric oxide gas with 3N purity

Abstract

The invention discloses a purification method of nitrogen oxide with 3N purity, which comprises the following steps: carrying out the decomposion of sodium nitrite with dilute sulfuric acid, alkali liquor absorption, gas and liquid separation, and drying and separating to obtain the gas, wherein the gas after being dried positively passes through a polyethylene glycol-methacrylate copolymer adsorption zone under the conditions that the temperature is minus 20 DEG C to 30 DEG C and the pressure is 0.5 MPa to 1.5 MPa; and then collecting the gas after being absorbed. By adopting a polyethylene glycol-methacrylate copolymer as an adsorbent, the disproprotionation of the nitrogen oxide and oxidation reaction can be effectively restrained, so that the impurity contents of nitrogen dioxide and nitrous oxide are reduced, and the purity of the nitrogen oxide is improved; the purity of the nitrogen oxide after being purified is larger than 99.9 percent; the content of the nitrogen dioxide is less than 20 ppm; and the content of the nitrous oxide is less than 50 ppm. Particularly, by adopting the secondary circulating adsorption process, foreign gas is positively absorbed, and simultaneously the negative decompression is performed to regenerate the absorbent. The invention has the advantages of simple operation process and low cost.

Description

Technical field: [0001] The invention relates to a gas purification method, in particular to a purification method of 3N (99.9%) pure nitric oxide gas with simple operation process, low cost and high purity. Background technique: [0002] At present, nitric oxide has played a unique role in various fields such as medicine, electronics, and chemical industry. For example, it can be used as an emergency terminator in the production of PVC to quickly terminate the polymerization of PVC monomer in the reactor when there is a power failure or an emergency. In order to prevent the temperature in the kettle from being too high to explode and avoid dangerous accidents, it has obvious advantages over the liquid-type termination additives used in the production of PVC in the past. It does not require N 2 As a carrier gas, combined with PVC monomer, it has strong ability, fast speed and long shelf life. However, in general, nitric oxide gas contains nitrogen dioxide gas, and nitrogen ...

AI Technical Summary

Problems solved by technology

However, in general, nitric oxide gas contains nitrogen dioxide gas, and nitrogen dioxide gas can be combined with PVC monomer to form explosive chelate, which has potential safety hazards. Therefore, it is necessary to strictly control the amount of nitrogen dioxide charged into the reactor The nitrogen dioxide content in the nitrogen monoxide gas stream shall not exceed 50ppm, and the purity of the nitrogen monoxide shall not be less than 3N

[0003] There are multiple methods for producing nitric oxide. U.S. Patent No. 3,663,167 points out that ammonia is oxidized in the air to prepare it, but the conditions required for this method are relatively high and difficult to realize; Nitrogen oxide gas, the disadvantage of this method is that the content of impurities (sulfur dioxide) is too much, and it is troublesome to remove; there is another method that uses sodium nitrite and dilute sulfuric acid to react to produce nitric oxide. The production process is to combine sodium nitrite with dilute sulfuric acid React in the reaction pool to generate sodium sulfate and sodium nitrate solutions as well as NO, H 2 O, while also producing NO 2 , N 2 O, N 2 , SO 2 , water vapor and other impurities, and sometimes a small amount of CO 2 (Air into the impact), etc.; the remaining reaction solution and generated sodium sulfate and sodium nitrate solution and a small amount of CO 2 , a small part of SO 2 , NO 2 Separation and removal from the bottom of the reactor by alkaline absorption and water washing, most of the NO 2 , N 2 O, water vapor, etc. flow out from the top of the reactor in gaseous form along with NO; water vapor is absorbed and removed in the dryer where the gas flow passes through the presence of anhydrous calcium chloride, and the operation is simple

[0004] Because nitric oxide is easy to combine with oxygen to generate nitrogen dioxide, and nitric oxide itself will slowly undergo disproportionation reaction in the presence of lye or high temperature to generate nitrogen dioxide and nitrous oxide. Therefore, there are many technologies at home and abroad. The research intends to remove nitrogen dioxide and nitrous oxide from the nitrogen monoxide gas flow. Chinese patent number 98108604.7 points out that the polyglucosamine ligand and transition metals such as Pt, Pd, Fe, Ni, Cu, Ag, Zn or The complexes formed by their salts are used as NO gas adsorbents, and then heated and diluted to obtain nitric oxide with a concentration ≥ 95%, but the purity of nitric oxide is too low to be used for high-end needs

U.S. Patent US3489515 points out and utilizes dilute nitric acid aqueous solution to clean nitrogen monoxide gas flow, and water and nitrogen dioxide react to generate nitric acid and nitrous acid, and then by water cleaning to remove impurity, but this method can not fully reduce the concentration of nitrogen dioxide, and The method of removing nitrogen dioxide by low-temperature distillation also has many disadvantages, not only the cost of distillation equipment is high, but also the consumption of nitrogen monoxide

[0005] There are also some reports on the use of adsorbents to remove nitrogen dioxide impurities from nitrogen monoxide gas streams, such as patent US5417950 pointing out the use of aluminum oxide-free ZSM5-Y type zeolite, US5514204 pointing out the use of metal-free silica gel and other A, X, Y-type zeolite, US2568396 and US41495858 point out the use of activated coke or activated charcoal, but the common disadvantage of these adsorbents is that it is easy to promote the disproportionation reaction of nitrogen monoxide gas, resulting in an increase in the content of nitrogen dioxide and nitrous oxide impurities, which still cannot meet the requirements of 3N Purity Nitric Oxide Gas Requirements

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