Purification method of 4N-purity nitric oxide gas

Abstract

The invention discloses a purification method of 4N-purity nitric oxide gas, and the purification method comprises steps of mixing reaction of dilute sulfuric acid and sodium nitrite, absorption through alkali liquor, gas-liquid separation, drying and separation, and the purification method is characterized in that dried gas forwardly flows through a polyethyleneglycol dimethacrylate adsorption area under the condition with temperature of minus 20DEG to 30DEG C and pressure of 0.5MPa to 1.0MPa; and the adsorbed gas is collected. The polyethyleneglycol dimethacrylate is used as an adsorption agent, so that the disproportionation and oxidization of the nitric oxide can be effectively inhibited, content of impurities such as nitric dioxide and nitrous oxide can be reduced, the purity of the nitric oxide gas is improved, the purity of the purified nitric oxide gas is more than 99.99 percent, the content of the nitric dioxide is smaller than 20ppm, and the content of nitrous oxide is less than 20ppm.

Description

technical field [0001] The invention relates to a gas purification method, in particular to a purification method of 4N (99.99%) 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 PVC production, that is, it can quickly terminate the polymerization of PVC monomer in the reactor when there is a power failure or an emergency. , to prevent the temperature in the kettle from being too high to cause an explosion and avoid dangerous accidents. Nitric oxide has obvious advantages over the liquid 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 ga...

AI Technical Summary

Problems solved by technology

However, in general, nitrogen monoxide 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 Nitrogen dioxide content in the nitric oxide gas stream (not to exceed 50ppm), and the purity of nitric oxide should not be less than 4N

[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; the most widely used one is the reaction of sodium nitrite and dilute sulfuric acid to prepare nitric oxide. Sodium nitrate reacts with dilute sulfuric acid in the reaction tank to generate sodium sulfate and sodium nitrate solution as well as NO and 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 (Affected by the entry of air), etc., and the prepared nitric oxide is easy to combine with oxygen to generate nitrogen dioxide, and at the same time, nitric oxide itself will slowly undergo disproportionation reaction in the presence of lye or high temperature to generate nitrogen dioxide and nitrous oxide Nitrogen, therefore, there are a number of technical researches at home and abroad to remove nitrogen dioxide, nitrous oxide, and

[0004] Chinese Patent No. 98108604.7 points out that complexes formed by polyglucosamine ligands and transition metals such as Pt, Pd, Fe, Ni, Cu, Ag, Zn or their salts are used as NO gas adsorbents, and then diluted by heating To obtain nitric oxide with a concentration ≥ 95%, but the purity of the obtained nitric oxide is too low to meet 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 impurities, 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] Some other practical sorbents are reported 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 practical metal-free cation 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, and still cannot meet the 4N purity Nitric Oxide Gas Requirements

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