JP3027763B2 - Activated carbon for recovery of organic halogenated solvents - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a granular activated carbon for recovering an organic halogen-based solvent and a method for producing the same, and particularly to adsorbing and desorbing an organic halogen-based solvent contained in a gas such as air. It is used for recovery in the process.

[Conventional technology]

Various activated carbons have been used for a long time to adsorb and recover the vapor of an organic halogen-based solvent contained in a gas such as air. However, since these organic halogen-based solvents are easily decomposed, these solvents are decomposed in the pores of the activated carbon when they are adsorbed on the activated carbon surface or when high temperature steam or air is introduced during desorption. . For this reason, halogen ions such as chlorine and fluorine are generated and cause corrosion of the adsorption device. In order to use a material having corrosion resistance, for example, it is necessary to use titanium or the like, which is very expensive, and thus has a practical problem.

In recent years, a large amount of halogen-based solvents such as chlorofluorocarbon and trichlene have been used for cleaning, cleaning of electronic parts, and the like. Recently, however, chlorofluorocarbon has been raised as a cause of ozone depletion in the atmosphere, and its emission into the atmosphere has been banned. The use of organic chlorinated solvents, alcohols, etc. is being planned as a substitute for CFCs. Activated carbon has been mainly used to recover trichloroethane, trichloroethylene, methylene chloride, carbon tetrachloride and other solvents as these organic chlorine-based solvents, chlorofluorocarbons and chlorofluorocarbon substitutes, but there were still many problems in performance. .

[Problems to be solved by the invention]

Halogen-based solvents such as chlorofluorocarbon and trichloroethane are easily decomposed, and particularly when they are adsorbed on activated carbon, they are easily decomposed by the catalytic properties of activated carbon and the action of heat or steam added during desorption to generate halogen ions. For this reason, the decomposition products degrade the quality of the recovered solvent, and halogen ions are harmful to sanitation. In particular, chlorine ions corrode the recovery equipment severely, which causes problems in maintenance and management. Accordingly, there has been a strong demand for an activated carbon having a low solvent decomposability in the adsorption / desorption step.

[Means for solving the problem]

The present inventor studied the relationship between the decomposability of the organic halogenated solvent and the surface structure of the granular activated carbon, and found that the total acidic group content of the granular activated carbon had a significant effect on the decomposition of the organic halogenated solvent. As a result of research on the present invention, the present invention has been reached.

That is, the activated carbon is a granular activated carbon for recovering an organic halogen-based solvent, wherein the total amount of acidic groups contained in the activated carbon is 0.5 meq / g or more, preferably 1.0 meq / g or more. In this method, the total amount of acidic groups is adjusted to 0.5 meq / g or more, thereby producing an activated carbon for recovering an organic halogen-based solvent.

 Hereinafter, the present invention will be described in detail.

Here, the total amount of acidic groups refers to the equivalent amount of alkali consumed when a diluted alkali solution is added to activated carbon and shaken for a long time. This value is based on studies by Boem et al. (Boem et al: Angew
According to andte Chemie P.617 [1966]), it corresponds to the amount of carbonyl group, lactone group and carboxyl group bonded to the surface of the carbon material. The specific quantification method is as follows.

Put 1 g of dried powdered activated carbon in a 100 ml Erlenmeyer flask,
Add 50 ml of pure water and 50 ml of 0.1N NaOH solution, and shake with a shaker at 25 ° C. for 24 hours. Then, centrifuge 80
The sample is settled at 00 rpm for 15 minutes, 20 ml of the supernatant is collected in a 100 ml Erlenmeyer flask, and the total amount of acidic groups is determined by back titration with 0.1N hydrochloric acid. At the time of titration, methyl red is used as an indicator, and in order to eliminate carbonic acid error, boiling is driven out near the end point to remove carbonic acid, and after cooling, titration is performed again, and the point indicated by redness is regarded as the end point. (Aml), and perform a blank test in the same manner (Bml) Total acid group amount C: C = (BA) × 0.1 × f × 50/20 C: Total acid group amount (meq / g) f: 0.1N hydrochloric acid Factor of the granular activated carbon used in the present invention is not particularly limited. Granular activated carbon obtained by carbonizing synthetic resins such as aromatic polycyclic condensates obtained from natural plants such as sawdust and coconut palm, coal and petroleum, and phenolic resins, and activating the resin by a conventional method. The specific surface area of these activated carbons is not particularly limited.
00m ² / g or less is preferable.

The granular activated carbon can be used in a crushed form, a granulated form having a predetermined shape, or a granular form.

The total amount of acidic groups contained in the activated carbon of the present invention must be 0.5 meq / g or more, preferably 1.0 meq / g or more. If the total amount of acidic groups is 0.5 meq / g or less, the organic halogenated solvent is unsuitable because of its high decomposability. Also, the larger the total amount of the acidic groups, the lower the decomposability of the solvent. Particularly, in the region of 1.0 meq / g or more, the decomposability is remarkably reduced, so that it is more preferable.

The activated carbon obtained by the ordinary activation method using steam or carbon dioxide has a total acidic group content of 0.2 to 0.4 meq / gram. Therefore, in order to prepare the activated carbon used in the present invention, it is necessary to greatly increase the total acidic group content.

The acidic group content can be increased by dry or wet oxidation of activated carbon.

In the wet oxidation method, activated carbon is immersed in an aqueous solution of sulfuric acid, hydrogen peroxide, chlorine, nitric acid, etc. as an oxidizing agent, and then dried and dried.
In this method, heat treatment is performed at 0 to 500 ° C. in an inert gas.

The dry oxidation method uses air or oxygen-containing gas.
The treatment is preferably performed at a temperature of 200 ° C. or more and 500 ° C. or less. 20
At a temperature of 0 ° C. or less, the carbon material has low reactivity and cannot be sufficiently oxidized. The wet oxidation is easier than the dry oxidation, and the amount of the surface oxide is easily controlled, which is preferable. The oxidation treatment may be a one-step method or a method of dividing the oxidation treatment into two or more steps at different temperatures. When using oxygen, for example, 1
Weight yield in an atmosphere with an oxygen partial pressure of × 10 ^-2 torr or more
It is appropriate to make it 80% or more. Weight yield
If it is less than 80%, the etching of the surface proceeds and the weight loss increases, which is not preferable. Further, the gas may be brought into contact with a gas containing ozone at a low temperature, or the activated carbon may be treated with oxygen plasma. For example, the activated carbon of the present invention can be obtained by enclosing an activated carbon electrode in a tube in which a gas containing oxygen is enclosed and performing high-pressure discharge.

〔The invention's effect〕

When the granular activated carbon of the present invention is used for recovering an organic halogen-based solvent, the decomposability in the solvent adsorption / desorption step is significantly reduced. Therefore, the quality of the recovered solvent is improved,
The corrosion of the equipment is also greatly reduced, which can significantly improve the economics.

〔Example〕

Hereinafter, the present invention will be described specifically with reference to Examples.
The present invention is not limited by this.

Examples 1 and 2 Comparative Example 1 100 parts of coconut charcoal pulverized to 100 to 300 mesh, 30 parts of coal tar pitch, 4 parts of heavy oil, and 15 parts of water were mixed well.
The mixture was granulated into pellets of 3 mm, oxidized by heating to 250 ° C. while blowing a small amount of air with a rotary kiln, and further stopping the blowing of air, followed by heating to 650 ° C. and dry distillation. Next, the gas and steam which burned liquefied petroleum gas were blown into the fluidized activation furnace, activated at 850 ° C for 4 hours, washed with hydrochloric acid, washed with water and dried, and activated carbon with a total acid group content of 0.21meq / g (compared to Example 1) was obtained.

This was oxidized in air at 500 ° C. for 1 hour to obtain activated carbon having a yield of 94% and a total acidic group content of 0.84 meq / g (Example 1). Activated carbon (Example 2) having a total acidic group content of 1.63 meq / g was obtained by further changing the conditions.

The decomposition rate of Freon 113 was measured using these activated carbons.

The decomposition rate of the solvent is as follows.
And heated to 200 ° C.
The solution was supplied at 1 / hr for 1 hour, the effluent gas was trapped with an alkaline solution, and the chloride ion in the solution was quantified by ammonium thiocyanate titration. Chlorine in activated carbon was boiled with an alkaline solution, and chloride ions in the solution were similarly quantified. The decomposition rate was calculated from the amount of chlorine in the effluent and activated carbon. Similarly 1,1,
The decomposition rate of 1-trichloroethane at 150 ° C. was measured. Table 1 shows the results.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) C01B 31/08 B01J 20/20 B01D 53/70 B01D 53/02

Claims (3)

(57) [Claims] 1. A granular activated carbon for recovering an organic halogen-based solvent, wherein the total amount of acidic groups contained in the granular activated carbon is 0.5 meq / g or more. 2. The granular activated carbon has a total acidic group content of 1.0 meq / g.
The granular activated carbon for recovering an organic halogen-based solvent according to claim 1, which is not less than gram. 3. A method for producing a granular activated carbon for recovering an organic halogen-based solvent, wherein the total amount of acidic groups is adjusted to 0.5 meq / g or more by oxidizing the granular activated carbon.