CN1234367A

CN1234367A - Process for recovering, separating and purifying NO gas

Info

Publication number: CN1234367A
Application number: CN 98108604
Authority: CN
Inventors: 陈贻盾; 马锦波
Original assignee: Fujian Institute of Research on the Structure of Matter of CAS
Current assignee: Tongliao Gold Coal Chemical Co., Ltd.
Priority date: 1998-05-06
Filing date: 1998-05-06
Publication date: 1999-11-10
Anticipated expiration: 2018-05-06
Also published as: CN1155509C

Abstract

The method for recovering, separating and purifying NO gas includes NO gas absorbent and technological equipment for recovering, separating and purifying NO gas. Said NO gas absorbent is a complex compound produced by using chitosan ligand and transition metals of Pt, Pd, Fe, Ni, Cu, Ag and Zn, etc or their salts. Said absorbent can absorb NO gas in the exhaust gas at normal temp., then through the processes of heating and diluting treatment, the NO gas whose concentration reaches greater than or equal to 95%. Said absorbent can be repeatedly and cystically used. Said invention is favourable for reducing waste of NO resource, reducing environmental pollution, so that can obtain extensive application.

Description

Method for recovering, separating and purifying NO gas

The invention belongs to the field of chemical industry and environmental protection.

It is well known that nitrogen oxides are both important resources and a major source of atmospheric pollution. It is mainly derived from gases discharged from nitric acid manufacturing plants, chemical plants using nitric acid, and gases discharged from stationary generation sources such as power plants, iron works, cement plants, glass plants, chemical plants, etc. which burn fuel and exhaust smoke, and mobile generation sources such as automobiles, etc. Among them, nitric acid plants and chemical plants using nitric acid are the most preferred. Data show that NO is currently artificially formed worldwide_xThe total emission was about 5000 million tons/year, of which 90% was NO gas. Due to the presence of NO_xThe gas contains more than 3 percent of oxygen and a small amount of SO₂Besides, the catalyst also contains a lot of CO, water vapor, dust and the like, which can eliminate NO_xContamination presents various difficulties. How to recover or eliminate the environmental pollution of NO is always the key point of environmental protection work, causes great attention of governments and scientists of various countries, has invested a great deal of manpower and material resources for development, and has achieved many achievements. The currently developed methods for removing nitrogen and pollution include tens of methods in the two major categories of dry method and wet method. The wet method comprises the following steps: wet alkali neutralization absorption, acid absorption, complex formation absorption, liquid phase reduction, gas phase oxidation absorption, liquid phase oxidation absorption, and the like; the dry method comprises the following steps: catalytic decomposition, catalytic reduction, adsorption, absorption, electron beam irradiation, and the like. Many of these methods are still not very practical and each has advantages and disadvantages. Recently, M.Iwamato et al developed a copper ion-ZSM-5 zeolite catalyst capable of directly decomposing NO to O₂+N₂It is a great progress, but has not yet reached a practical stage. It has been expected that people will find out how to develop a new practical process for eliminating NO pollution, which has the advantages of simple process, easy operation, low cost and NO need of post-treatment of the recovered substances.

NO gas is an important chemical reaction raw material and can be used for manufacturing a plurality of nitrogen-containing compounds, such as nitrite (formula ①), dinitrile (formula ②③) and a plurality of nitric acid (formula ②④).

..........①

......................②

.............③

.................④

However, the source of pure NO gas is very small, and it is mainly composed of NaNO₂Reacting with sulfuric acid to form NO and NO₂The mixture is subjected to alkali absorption to remove NO₂And (3) preparing:

....⑤

many chemical reactions, such as CO gas phase catalytic synthesis of carbonic acid diester (formula ⑥), CO gas phase catalytic synthesis of oxalic acid diester (formula ⑦), and reaction exhaust gas from ethylene glycol oxidation to oxalic acid, starch oxidation to oxalic acid, etc., generate a large amount of NO gas.

..............⑥

.............⑦

The tail gas of the nitric acid production plant also has a large amount of NO gas discharged into the atmosphere. If the method and the process for recovering, separating and purifying the CO gas can be used for recovering, separating and purifying the NO gas from the tail gas of the chemical reaction or the tail gas of the nitric acid plant, the required large amount of high-concentration NO gas can be provided for the chemical plant, the consumption of raw materials is reduced, the production cost is reduced, the pollution of the NO gas to the environment is reduced, and the quality of the environment for human life is improved. Meanwhile, a large amount of NO gas with high concentration is provided, so that the production process for preparing the concentrated nitric acid can be improved, and the method has important economic significance. However, the method and the process which can effectively recover, separate and purify NO gas like the method and the process which can recover, separate and purify CO gas have not been realized and applied so far, and have not been reported.

The invention aims to provide a method for recovering, separating and purifying NO gas from exhaust gas, fills the blank at home and abroad, realizes the recovery, separation and purification of NO gas from the exhaust gas, provides a large amount of high-concentration NO gas for chemical industry, fully recovers and utilizes NO resources, reduces resource waste, lightens environmental pollution and improves the quality of human living environment.

The method for recovering, separating and purifying NO gas uses a modified natural polymer-transition metal complex NO gas absorbent to absorb, separate and purify NO gas from discharged gas, and the specific scheme is as follows:

the NO gas absorbent is made of a complex of chitosan and certain transition metals or theirsalts. The chitosan is prepared from natural chitosan prepared from shell of shrimp, crab or insect (such as engineering fly), and is modified with strong alkali to remove acetyl and obtain chitosan. The deacetylation degree is 50-100%, preferably 80-100% (chitosan with deacetylation degree not less than 80% may be used). The chitosan is then dissolved in certain dilute acids to form complexes with certain transition metals or their salts. The complex can selectively absorb NO gas in an aqueous solution with pH = 1-7 at normal temperature (-5-40 ℃), then, the absorbed NO gas is completely explained under the heating condition of 60-110 ℃, the released gas is isolated from air, and the NO gas with purity of more than 95% can be obtained.

The transition metal for forming a complex with chitosan may be Pt, Pd, Fe, Ni, Cu, Ag, Zn, etc., and the salts thereof may be inorganic salts such as sulfate, phosphate, nitrate, chloride, etc., or organic salts such as lactate, citrate, acetate, formate, etc.

The acid for dissolving chitosan and some transition metals or their salts may be inorganic acid such as nitric acid, sulfuric acid, hydrochloric acid, phosphoric acid, etc., or organic acid such as formic acid, acetic acid, lactic acid, tartaric acid, citric acid, etc., and its concentration is 0.1-10%, preferably 0.5-4%. Firstly, dissolving some transition metals or salts thereof in a dilute acid solution according to a certain concentration, then stirring and mixing the transition metals or salts thereof with the dilute acid solution of the chitosan according to the ratio of 1: 1-1.5: 1 (gram-molecule ratio) to form a polymer-transition metal complex, and then dissolving the polymer-transition metal complex in water to obtain the modified natural polymer-transition metal complex NO gas absorbent.

The process flowschematic diagram of the NO gas absorbent recovery, separation and purification of NO gas is shown in the attached drawing: wherein 1, gas compressor 2, gas flowmeter 3, NO absorption tower 4, gas flowmeter 5, absorption liquid storage tank 6, liquid transfer pump 7, heater 8, NO gas interpretation tower 9, barren solution storage tank 10, liquid transfer pump 11, cooler 12, gas flowmeter 13, NO gas storage tank

The process flow of NO gas absorbent recovery, separation and purification of NO gas will now be further described with reference to the accompanying drawings: the gas containing NO is sent into an absorption tower 3 by a compressor 1 through a flow meter 2, the NO gas is absorbed by NO gas absorption liquid from top to bottom in the tower 3, tail gas is metered by a flow meter 4 and then discharged to the air, the absorption liquid for absorbing the NO gas is sent out by a liquid delivery pump 6, and the absorption liquid enters an explanation tower 8 after being heated by a heater 7. In the column 8, the NO gas is interpreted from the absorption liquid, cooled by the cooler 11, measured by the flow meter 12, and collected into the gas holder 13. The absorption liquid (lean liquid) after the explanation of NO gas is cooled by the storage tank 9 and then is sent back to the absorption tower 3 by the pump 10 for recycling. The reciprocating circulation can recover, separate and purify NO gas from the discharged tail gas containing NO gas, the purity of the obtained NO gas reaches more than 95 percent, and the purity of the obtained NO gas reaches more than 98 percent, and the obtained NO gas is an ideal raw material for chemical reaction and is also an ideal raw material for producing concentrated nitric acid.

The NO gas absorbent has simple preparation process and rich raw material sources. The chitosan for preparing the chitosan is chitin widely existing in shells of arthropods such as shrimps, crabs and the like and shells of many insects (such as engineering flies). According to the data report, the storage amount of chitin on the earth is equivalent to that of plant cellulose, and the resource is extremely rich. The technology for preparing chitosan (chitosan) from chitin is also mature and common, and a plurality of factories have mass production and sale of the chitosan product in China.

The invention has the characteristics of simple process flow, high efficiency of absorbing and recovering NO gas by the absorbent and repeated long-term use. 5.2 g of NO gas absorbent is dissolved in 100 ml of water solution to absorb NO gas in the discharged gas for 8 hours, then the water solution is heated to 100 ℃, 560 ml of NO gas is released, the NO content reaches 982 percent, the water solution is repeatedly used for more than 35 times, the amount of the absorbed and recovered NO gas is stable and unchanged, and the recovery rate of NO in the discharged tail gas is more than or equal to 80 percent.

The technology can be used for recovering, separating and purifying NO gas in the tail gas of chemical reaction and NO gas in the tail gas discharged by a chemical factory using nitric acid, can be used for recovering and recycling the NO gas in the tail gas discharged by the nitric acid factory, and fills the gap that the equivalent NO gas in the tail gas discharged by the chemical factory can not be recycled, thereby greatly reducing the waste of NO raw materials, lowering the production cost, simultaneously lightening the pollution of the NO gas to the environment, and making contribution to improving the quality of the human living environment and creating better economic benefit and social benefit.

Example one

1.6 g of chitosan (degree of deacetylation. gtoreq.80%) are weighed out and dissolved in 30 ml of 1% HCOOH solution (solution A). 1.0 g of CuCl was weighed into 20 ml of 1% HCI (solution B). Then mixing the A and B solutions, and stirring them uniformly to form the chitosan-copper complex. Then dissolved in 100 ml deionized water, NO gas containing 8% is introduced at the speed of 0.5L/hr, bubbling is carried out at the temperature of 15 ℃ for absorption for 8 hours, and then the absorption liquid is heated to the temperature of 100 ℃, so that a large amount of NO gas is released. The released gas was recovered in the isolation air to obtain 260 ml of NO gas with 98.5% content.

Example two

1.6 g of chitosan was dissolved in 30 ml of 1% HCOOH solution (solution A). Taking 1.7 g of PdCl₂Dissolved in 20 ml of 1% HCI (solution B). Mixing the A liquid and the B liquid, stirring uniformly, adding 100 ml of water, introducing 10% NO gas at the speed of 0.4L/hr, bubbling and absorbing at 20 ℃ for 8 hours, heating the absorption liquid to 95 ℃, and collecting 250 ml of released NO gas, wherein the NO content reaches 98.8%.

Claims

1. A method for recovering, separating and purifying NO gas is characterized in that: the NO gas is recovered, separated and purified from the discharged gas by using a modified natural polymer-transition metal complex NO gas absorbent.

2. The method for recovering, separating and purifying NO gas as claimed in claim 1, wherein: the modified natural polymer-transition metal complex NO gas absorbent adopts nitrogen-containing modified natural polymer chitosan with deacetylation degree of 50-100% as a ligand of the modified natural polymer-transition metal complex.

3. The method forrecovering, separating and purifying NO gas as claimed in claim 1, wherein: the modified natural polymer-transition metal complex NO gas absorbent adopts transition metals such as Pt, Pd, Fe, Ni, Cu, Ag, Zn and the like or salts thereof as the metal center of the complex.

4. The method for recovering, separating and purifying NO gas as claimed in claim 1, wherein: the modified natural polymer-transition metal complex NO gas absorbent absorbs NO gas in an acidic aqueous solution medium, and the pH value of the aqueous solution is 1-7.

5. The method for recovering, separating and purifying NO gas as set forth in claim 1, wherein: the temperature of the modified natural polymer-transition metal complex NO gas absorbent for absorbing NO gas is-5-40 ℃.

6. The method for recovering, separating and purifying NO gas as claimed in claim 1, wherein: the modified natural polymer-transition metal complex NO gas absorbent is separated and explained that the temperature of NO gas is 60-110 ℃.

7. A method for recovering, separating and purifying NO gas as claimed in claim 2 or 3, wherein: the acid for dissolving the chitosan ligand and transition metal such as Pt, Pd, Fe, Ni, Cu, Ag, Zn, or salts thereof to form a coordination complex may be organic acid such as formic acid, acetic acid, lactic acid, tartaric acid, citric acid, etc., and the concentration of the acid is 0.1-10%.

8. A method for recovering, separating and purifying NO gas as claimed in claim 2 or 3, wherein: the acid for dissolving the chitosan ligand and transition metal such as Pt, Pd, Fe, Ni, Cu, Ag, Zn, or salts thereof to form a coordination complex may be an inorganic acid such as nitric acid, sulfuric acid, hydrochloric acid, or phosphoric acid, and the concentration of the acid is 0.1 to 10%.

9. A method for recovering, separating and purifying NO gas as claimed in claim 3, wherein: the transition metal salt used as the metal center of the modified natural polymer-transition metal complex NO gas absorbent can be inorganic salts such as sulfate, phosphate, nitrate, chloride and the like.

10. A method for recovering, separating and purifying NO gas as claimed in claim 3, wherein: the transition metal salt used as the metal center of the modified natural polymer-transition metal complex NO gas absorbent may be an organic salt such as lactate, citrate, acetate, formate, or the like.