JPS63205140A - Adsorbent for nitrogen monoxide and method for separating and removing nitrogen monoxide - Google Patents

Abstract

PURPOSE:To recover nitrogen monoxide at high concn. from gas containing nitrogen monoxide at low concn., by using a nitrogen monoxide adsorbent prepared by a method wherein activated carbon and a divalent or trivalent iron salt are mixed in a solvent and the solvent is removed to dry the resulting mixture. CONSTITUTION:After activated carbon and a divalent or trivalent iron salt such as ferrous sulfate, ferrous chloride, ammonium ferrous sulfate, ferric sulfate, ferric chloride or ferric acetate are mixed in a solvent, the solvent is removed and the resulting mixture is dried to prepare a nitrogen monoxide adsorbent. There is no limit in the shape of activated carbon but the particle size thereof is 0.01-50mm, pref., 0.1-5mm. As the solvent, 1-6C alcohol is pref. and the addition amount thereof is 1-1,000cm<3>, pref., 10-100cm<3> per 10g of activated carbon. When the obtained adsorbent is used, NO can be selectively adsorbed from a gaseous mixture containing 30%-1ppm of NO.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides - an adsorbent that can rapidly adsorb and desorb nitric oxide (NO) from a mixed gas containing nitrogen oxide, and a method for separating NO from a mixed gas using the adsorbent. It relates to a method of removal.

No. 9, an air pollutant, is normally emitted into the atmosphere in large amounts from waste gas from thermal power plants and steel mills at concentrations ranging from several hundred to several thousand ppm, but methods for removing this NO include:
Currently, the main method used is to mix reducing gas such as ammonia into waste gas and bring it into contact with a catalyst to reduce the waste gas to harmful nitrogen gas. For example, 300 ppm NO
and 250 ppm of ammonia.
space velocity of 2 for alumina-copper oxide-titania catalyst at °C.
When contacted at 0000h-1, the N contained in the sample gas
60% of o is removable. This method reduces nitrogen oxides with ammonia to produce nitrogen gas, but has drawbacks such as requiring ammonia and difficulty in completely removing nitrogen oxides under mild conditions.

Additionally, using excess ammonia can increase the NO reduction rate, but in this case, there are drawbacks such as the need for ammonia removal equipment to prevent harmful excess ammonia from being released into the atmosphere. be. Furthermore, the above method is aimed at removing NO, not at separating and recovering it.

In addition, in order to remove nitrogen oxides from automobile exhaust, carbon monoxide generated by incomplete combustion of fuel Ganlin is brought into contact with a platinum-copper-cordierite catalyst as a reducing agent.
Converts nitrogen oxides into nitrogen gas.

- A method is used to convert carbon oxide into carbon dioxide and make it harmless, but in order to keep the concentrations of both carbon monoxide and nitrogen oxides in the gas released after catalyst contact low, it is necessary to mix air with the fuel. It is difficult to strictly control the combustion conditions such as the ratio, and it also has drawbacks such as the impossibility of complete detoxification. Even though it is illegal, it is not aimed at separating and recovering NO.

Zhurnal Pr1kladnoi Khimi
I magazine, published in 1958, volume 31, page 138, states that activated carbon has the ability to adsorb No.

However, its adsorption capacity is low, and according to the authors' additional tests, 1
6 dm3 and 1.6 nitrogen gas containing 1000 pp NO
Contact with 10g of activated carbon at a rate of dm3@min''.

Even after 90 minutes, only about 37 g of NO was adsorbed, which does not have adsorption capacity suitable for practical use.

Industrial and Engineering
g Chem'1try.

Process Design and Development
pment magazine, published in 1980, volume 19, page 377, describes that an aqueous solution of iron(11)-EDTA (ethylenediaminetetraacetic acid) complex and sodium sulfite absorbs NO. However, with this absorbent, the absorbed No reacts to produce sodium imidobis sulfate and the like, so it is not possible to separate and recover No. Furthermore, when only an aqueous solution of iron ([)-EDTA complex is used as an absorbent, it is possible to separate and recover NO, but the central metal iron (U) ion is easily oxidized to trivalent by the mixed oxygen. Absorbent deteriorates.

Furthermore, since it is an aqueous solution system, it has drawbacks such as water vapor, which is a solvent, mixing with the recovered NO.

Industrial and Engineering
g Chemistry.

Product Research and Development
lopment magazine, published in 1984, Volume 23, 417
The page states that molten salts consisting of sodium sulfite, lithium bisulfite and vanadium oxide remove NO. However, this method requires ammonia and NO is converted into nitrogen, and NO is not separated and recovered. Also, how to remove No.

There are problems with container materials that are resistant to molten salts.

Journal of the Chemical Society of Japan, published in 1985, page 2315, states that α-F, an iron oxide, is added to activated carbon fiber (not activated carbon).
An adsorbent for NO obtained by depositing ed(OH) is described. However, in this system, Fed(OH)
Because the bond between surface oxygen and NO is strong, desorption and recovery are not easy. Furthermore, since the conditions for producing α-Pea (Ot-1) and the process of depositing this crystal onto activated carbon fibers are delicate, it has the disadvantage that it is difficult to prepare an adsorbent.

Although nine other types of adsorbents and separation/removal methods have been proposed, there is still no method that is completely satisfactory for separating and removing NO from a mixed gas.

The present applicants have proposed that cross-linked polystyrene resin V having functional groups
By using a polymer complex supporting a C2-valent iron salt, we have already succeeded in adsorbing and removing dilute No.

Based on the results of this research, we worked hard to find a carrier that was more economical than polymer resins.

By using activated carbon as a carrier and supporting divalent or trivalent iron salts, the authors have already developed polymer resin-supported iron (for the development of a highly active adsorbent comparable to the old complex). Successful.

The adsorbent in the present invention is a solid obtained by stirring and mixing activated carbon and a divalent or trivalent iron salt in a solvent, and then distilling off the solvent under heating or reduced pressure.

The iron salt used in the present invention is 9, for example, iron(II) sulfate.

Iron chloride (formerly, iron sulfate (formerly ammonium (Mohr's salt)).

It is a divalent or trivalent iron salt such as iron sulfate (■), iron chloride (■), and iron acetate ([1). How much iron salt to add?

Although not particularly important, preferably 1g per 10g of activated carbon.
~100g.

The activated carbon described in the specification is a material obtained by carbonizing a raw material containing carbon as a main component and then subjecting it to activation treatment.

The shape of the activated carbon used in this adsorbent preparation is not particularly limited.
Its particle size is 0.01-50m, preferably 0.1-5m
It is.

The amount of solvent to be added is 1 cm3 to 1 cm3 to 10 g of activated carbon.
0000m3 preferably 10-1000m3. The stirring time is 10 minutes to 1 day, preferably 1 hour to 5 hours.

The temperature during solvent distillation is 10 to 300°C, preferably 50 to 100°C.

This adsorbent preparation can be carried out under air, but it is preferable to carry out under nitrogen only when divalent iron salts are used.

If the adsorbent of the present invention is used, 30% to I I) I) m
A mixed gas containing NO can selectively adsorb NO. This adsorption is -4000~12 under normal pressure.
It can be carried out at 0°C, preferably 0 to 100°C. Furthermore, by performing adsorption under pressure, it is possible to adsorb more quickly and in large amounts. Either raise the temperature of the adsorbent that has adsorbed NO to 50 to 200°C, or
Adsorbed NO can be desorbed by lowering the partial pressure of O to 10-3 to 100 rrmHg, preferably 0.1 to 10 mmHg. Desorption of NO can also be carried out by lowering the partial pressure of NO while increasing the temperature of the adsorbent. This desorption operation regenerates the adsorbent,
It can be used again to adsorb NO. Moreover, this combination of adsorption and desorption of NO makes it possible to concentrate and recover NO to a high concentration from a mixed gas containing a low concentration of NO. Conventionally, NO has only been disposed of or made harmless9, but the present invention makes it possible to recover it as highly concentrated NO, making it possible to use this NO as a chemical raw material9 to produce, for example, nitrous acid and nitric acid. Become.

Example 1 Iron chloride (It) 4.59 hydrate was a special grade reagent manufactured by Kanto Kagaku Co., Ltd., and was used as it was. Activated carbon.

Manufactured by Kureha Chemical Industry Co., Ltd., BAC, G-7OR, approximately 20
It was used after being subjected to a vacuum treatment of 5 mrrJ (g or less) for 5 hours at 0°C. Distilled water was used.

As the nitrogen gas containing 11,000 pp of NO, a cylinder gas manufactured by Takachiho Chemical Industry Co., Ltd. was used as it was.

'! , In a 200 cm3 two-turon type flask, the above activated carbon Log, iron chloride 4.59 hydrate 1.04
g (5 mmol) and distilled water 500 m3,
After replacing the atmosphere with nitrogen, the mixture is stirred using a magnetic stirrer for 3 hours. This mixture of activated carbon and iron chloride (n) aqueous solution was heated at 80°
By placing the mixture under reduced pressure, water as a solvent was distilled off to prepare an adsorbent. Adsorption experiments were conducted using this adsorbent as follows. First, an adsorbent was placed in a glass column with an inner diameter of 11, which was placed in a closed circulation reactor, and after the system was degassed, 6 dm3 of nitrogen gas containing 11,000 pp of NO was introduced at room temperature and normal pressure. This gas is 1, 5 dm3・
It was circulated through the apparatus at a speed of m1n-' and brought into contact with the adsorbent in the column.

The concentration of No. is 23.8 cm3 and the optical path length is 1.
Samples were taken in a 001& quartz cell, and absorbance was measured at 226.5 nm to observe changes over time. the result,
Thirty-five minutes after the start of contact with the sample gas, almost the entire amount (100%) of the charged NO was adsorbed and equilibrium was reached, and no deterioration was observed thereafter. After this, stop the gas circulation and use the mantle heater.

When the temperature of the adsorbent that had adsorbed NO was heated to 120'C and the gas was circulated again, 28 of the adsorbed No.
It took 5 minutes to put on and take off.

Example 2 1.39 g (5 mmol) of iron sulfate (n) heptahydrate (special grade reagent manufactured by Koso Chemical Co., Ltd.) was added, and further 500 m3 of water was added as a solvent, followed by the same method as in Example 1. When an adsorbent was prepared and an adsorption experiment was conducted in the same manner as in Example 1, 84% of the NO charged was adsorbed 15 minutes after the start of the adsorption experiment.

Deterioration of the adsorbent then occurred and re-release of adsorbed NO into the gas phase was observed.

Example 3 The amount of iron chloride (n) supported was 4.18 g (20 mmol
), the adsorbent was prepared in the same manner as in Example 1,
An adsorption experiment was conducted in the same manner as in Example 1.

Approximately 100 units of No. were adsorbed in 35 minutes and equilibrium was reached.

Example 4 656 g of iron chloride (n) 4.59 hydrate in activated carbon Log
(31.3 mmol) was added, and 500 m3 of ethanol (manufactured by Kanaka Kagaku Sangyo Co., Ltd.) was added as a solvent to create a nitrogen atmosphere in the flask. After stirring with a magnetic stirrer for 3 hours, the solvent was depressurized at 50°C for 12 hours. The adsorbent was prepared by distillation. When an adsorption experiment was conducted using this adsorbent in the same manner as in Example 1, it adsorbed 70 tons of charged NO in 55 minutes and reached equilibrium.Example 5 Iron chloride (Ill) was added to 10 g of activated carbon.・Hexahydrate 1.3
5 g (5 mmol, first class reagent manufactured by Yanagishima Pharmaceutical Co., Ltd.) was added, water was added as a solvent, and the mixture was stirred and mixed in air for 3 hours, and then the solvent was distilled off at 80° C. under reduced pressure to prepare an adsorbent. When an adsorption experiment was conducted using this adsorbent in the same manner as in Example 1, it adsorbed 95% of the charged NO and reached equilibrium 15 minutes after the start of contact with the sample gas.

Example 6 Iron sulfate (■) (special grade reagent manufactured by Kosui Chemical Company) t, 40
When an adsorption experiment was conducted in the same manner as in Example 1 using 10 g of activated carbon and 5 mmol of iron (III), 2
In 5 minutes, 73% of the charged NO was adsorbed and equilibrium was reached.

Comparative Example 1 An adsorption experiment was conducted in the same manner as in Example 1 on activated carbon obtained by adding 50 cm3 of ethanol to 10 g of activated carbon, stirring for 3 hours, and then distilling the solvent off under reduced pressure at 50'C for 12 hours. As a result, 25 minutes after the start of contact with the sample gas, the NO was 15% compared to the charged NO.

The adsorption activity was 37 in 90 minutes, which was much lower than that of the adsorbents prepared in any of the systems of Examples 1 to 6.

Claims (1)

[Scope of Claims] 1) A nitric oxide adsorbent produced by mixing activated carbon and iron salt in a solvent, then removing the solvent and drying. 2) A method of separating nitrogen monoxide from a mixed gas using an adsorbent according to item 1). 3) An adsorbent for nitric oxide in which the solvent in item 1) is water. 4) An adsorbent for nitrogen monoxide when the iron salt in item 1) is divalent iron. 5) An adsorbent for nitrogen monoxide when the iron salt in item 1) is trivalent iron. 6) An adsorbent for nitrogen monoxide in which the solvent in item 1) is an alcohol having 1 to 6 carbon atoms. 7) An adsorbent for nitrogen monoxide in which the solvent in item 1) is a cyanated hydrocarbon having 2 to 8 carbon atoms. 8) An adsorbent for nitrogen monoxide in which the solvent in item 1) is a ketone having 1 to 8 carbon atoms.