Fluorocarbon disposal methods

Abstract

To provide a method for efficiently decomposing iodofluorocarbon to hydrogen fluoride and carbon dioxide.SOLUTION: In a treatment method of iodofluorocarbon exhibited as formula: I-(CF2)n-I (where, n is an integer of 2-12),: the iodofluorocarbon is reacted with alcohols in the presence of a base and reduced to a corresponding hydrofluorocarbon; an obtained reaction liquid is separated to an aqueous layer and an organic layer containing hydrofluorocarbon by being added with water; and subsequently, the organic layer is decomposed to hydrogen fluoride in hydrofluorocarbon and carbon dioxide.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention provides a method for treating fluorocarbons. [Background technology]

[0002] Iodofluorocarbons, a type of chlorofluorocarbon (CFC), are considered a cause of ozone depletion, just like other CFCs, and therefore require proper disposal. Existing technologies exist for decomposing CFCs into hydrogen fluoride and harmless fluorine. For example, these include combustion pyrolysis, catalytic decomposition, chemical decomposition, and methods that destroy CFCs by reacting them with supercritical water. Furthermore, there are methods for separating CFCs and destroying the separated CFCs, as well as methods for destroying them together with a mixture of CFCs. In the latter case, most processing methods involve combustion pyrolysis, and most of the processing equipment consists of calcination furnaces or electric furnaces. However, there was a problem in that the presence of iodine and iodides could damage the furnaces. Therefore, there was a need to develop an efficient processing method that would not damage calcination furnaces or electric furnaces.

[0003] This invention provides a method for efficiently decomposing iodofluorocarbons into iodine, iodide, hydrogen fluoride, and carbon dioxide without damaging firing furnaces or electric furnaces. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 7-223981 [Overview of the project] [Problems that the invention aims to solve]

[0005] The inventors have discovered a method for efficiently decomposing iodofluorocarbons into iodide and hydrofluorocarbons during waste disposal, and then further decomposing the resulting liquid hydrofluorocarbons into hydrogen fluoride and carbon dioxide. Therefore, the present invention provides the following method for treating iodofluorocarbons.

[0006] 1. Equation I - (CF2) n A method for treating iodofluorocarbons represented by -I (wherein n is an integer from 2 to 12), The iodofluorocarbon is reduced to the corresponding hydrofluorocarbon by reacting it with alcohols in the presence of a base; By adding water to the resulting reaction solution, it is separated into an aqueous layer and an organic layer containing the hydrofluorocarbon; then The aforementioned organic layer is subjected to a decomposition treatment that yields hydrofluorocarbons to hydrogen fluoride and carbon dioxide; A method that includes the act of doing so. 2. The method according to 1, wherein the alcohols are a mixture of methanol and isopropyl alcohol. 3. The method according to 1 or 2, wherein the organic layer is subjected to superheated steam decomposition treatment to decompose the hydrofluorocarbon into hydrogen fluoride and carbon dioxide. 4. The method according to any one of 1 to 3, wherein the superheated steam decomposition treatment is performed at a temperature of 880°C or higher. 5. The method according to any one of 1 to 4, further comprising the step of neutralizing the generated hydrogen fluoride and / or carbon dioxide. [Effects of the Invention]

[0007] The present invention provides the effect of efficiently decomposing iodofluorocarbons into iodide, iodine, hydrogen fluoride, and carbon dioxide. [Modes for carrying out the invention]

[0008] The present invention provides a method for treating iodofluorocarbons. Preferably, the iodofluorocarbon is in solid form and is represented by the following formula: I-(CF2) n -I (In the formula, n is an integer from 2 to 12, preferably an integer from 6 to 10).

[0009] 1) Reduction reaction Iodofluorocarbons can consist of a single carbon atom or a mixture of atoms with varying carbon numbers, for example, I-(CF2)6-I, I-(CF2)8-I, and I-(CF2). 10 -It may be a mixture of I, etc. The reduction of iodofluorocarbon to its corresponding hydrofluorocarbon is carried out, for example, by dissolving solid iodofluorocarbon preferably in alcohols in a reaction vessel and reacting it with an alkaline agent, such as a base such as potassium hydroxide, sodium hydroxide, or calcium hydroxide. When dissolving iodofluorocarbon in alcohols, the amount of iodofluorocarbon relative to the alcohols is preferably 10 to 60% by weight, more preferably 30 to 50% by weight. The amount of aqueous solution of base used per mole of iodofluorocarbon is not particularly limited, but for example, it is preferably in the range of 1 mole or more and 20 moles or less, more preferably in the range of 1 mole or more and 10 moles or less, and even more preferably in the range of 1 mole or more and 5 moles or less.

[0010] I-(CF2) n The corresponding hydrofluorocarbon obtained by reducing -I is represented by the following formula: H-(CF2) n -H (In the formula, n is "I-(CF2) n (This corresponds to the n in "-I")

[0011] The reduction reaction is carried out by dissolving the iodofluorocarbon in an alcohol and then bringing it into contact with an aqueous solution of a base. Examples of alcohols include methanol, ethanol, 1-propanol, 2-propanol (isopropyl alcohol), 1-butanol, 2-butanol, isobutanol, etc., but are not particularly limited. These alcohols may be used individually or in combination of two or more. Preferably, a mixture of methanol and isopropyl alcohol is used, for example, a mixture in which methanol:isopropyl alcohol is 1:1 to 20:1 by weight, preferably 5:1 to 10:1.

[0012] The amount of alcohol added is not particularly limited, but is preferably in the range of 1 mole to 100 moles, more preferably 1 mole to 50 moles, and even more preferably 1 mole to 10 moles, per mole of iodofluorocarbon to be reduced. It is preferable to add the alcohol dropwise over time so that the reduction reaction proceeds gradually. For example, if the iodofluorocarbon solution is 20 L, the alcohol may be added slowly dropwise over 20 to 200 minutes, preferably 50 to 100 minutes. The dropping temperature may be set by heating the alcohol from room temperature to a temperature slightly below its boiling point. For example, when using a mixture of methanol and isopropyl alcohol, it can be added dropwise at a temperature of 50 to 55°C. (The boiling points of methanol and isopropyl alcohol are 64.7°C and 82.5°C, respectively).

[0013] The reduction reaction may be carried out by stirring the solution as needed after the addition of the alcohols. Preferably, it may be carried out at a temperature slightly lower than the boiling point of the alcohols used, over several hours to several days, for example, 10 hours to 3 days.

[0014] 2) Separation into aqueous and organic layers After reduction to hydrofluorocarbon, an aqueous solution such as water is added to the solution and allowed to stand, separating it into an organic layer and an aqueous layer. The hydrofluorocarbon is contained in the organic layer. The aqueous layer contains the iodide of the base; for example, if potassium hydroxide is used as the base, it will contain potassium iodide.

[0015] 3) Decomposition of Hydrofluorocarbons into Hydrogen Fluoride and Carbon Dioxide By heat-treating the organic layer, hydrofluorocarbons can be decomposed into hydrogen fluoride and carbon dioxide. The heat treatment is preferably carried out using a superheated steam decomposition apparatus. When performing superheated steam decomposition treatment, particularly preferred temperatures are 800°C or higher and 1200°C or lower, for example, 880 - 1000°C. The treatment flow rate of the organic layer solution can be, for example, about 1 - 10 kg / Hr, preferably about 2 - 6 kg / Hr. The steam flow rate can be, for example, about 1.0 - 10.0 kg / Hr, preferably about 2 - 5 kg / Hr. The flow rate of Air can be, for example, about 1 - 30 Nm 3 / Hr, preferably about 5 - 25 Nm 3 / Hr. The generated hydrogen fluoride and carbon dioxide can be neutralized, if necessary, with, for example, slaked lime.

[0016] According to the present invention, iodofluorocarbons can be efficiently decomposed into hydrogen fluoride and carbon dioxide.

[0017] All documents mentioned in this specification are hereby incorporated by reference in their entirety.

[0018] The embodiments of the present invention described below are for illustrative purposes only and do not limit the technical scope of the present invention. The technical scope of the present invention is limited only by the description of the claims. Changes to the present invention, for example, addition, deletion, and substitution of the constituent elements of the present invention, can be made on the condition that the gist of the present invention is not deviated from.

Examples

[0019] <Example 1> Reduction of Iodofluorocarbons to Hydrofluorocarbons From I-(CF2)6-I to I-(CF2) 12-17.9 kg of iodofluorocarbon, a mixture of I, was dissolved in a mixed solution of 18.0 kg of methanol and 1.7 kg of isopropyl alcohol. Meanwhile, 14.8 kg of 48% potassium hydroxide aqueous solution was placed in a 65 L fluoropolymer-lined reaction vessel, and the iodofluorocarbon solution was added dropwise to this vessel over 100 minutes at a temperature of 50-55°C.

[0020] The reaction equation for a mixture of iodofluorocarbon, methanol, and isopropyl alcohol in the presence of potassium hydroxide is as follows: [ka]

[0021] The above reaction solution was stirred at a temperature of 60-63°C for 21 hours to carry out the reduction reaction. As a result of this reaction, approximately 98.5% of the iodonefluorocarbon was ultimately reduced to hydrofluorocarbon. This reaction solution was transferred to a 200L chemical drum, 17.9kg of pure water was added, and after stirring, it was allowed to stand to separate into an aqueous layer and an organic layer. Hydrofluorocarbon was contained in the organic layer, and potassium iodide was contained in the aqueous layer.

[0022] <Example 2> Decomposition of hydrofluorocarbons into hydrogen fluoride and carbon dioxide An organic layer containing hydrofluorocarbons having the composition shown in Table 1 was subjected to superheated steam decomposition under the conditions shown in Table 2. CD6H represents H-(CF2)6-H, and CD8H represents H-(CF2)8-H. The organic layer was identified and quantified by GC-MS analysis. The results are shown in Table 2. [Table 1]

[0023] [Table 2]

[0024] The evaluation test procedure is as follows: The superheated steam decomposition tank was a cylindrical metal container with an inner diameter of 125 mm and a length of 1,500 mm. Organic layers containing hydrofluorocarbons were pre-vaporized and supplied through its inlet, while predetermined amounts of water vapor and pure water were supplied simultaneously. A portion of the processed gas from the decomposition tank was sampled every 10 minutes, and the concentrations of C6DH, C8DH, and CO in the gas were measured to confirm that a steady state was maintained.

[0025] As shown in Table 2, the hydrofluorocarbon was almost 100% decomposed into hydrogen fluoride and carbon dioxide. The reaction equation is shown below. [ka]

[0026] From the above, it was found that hydrofluorocarbon liquids, mainly composed of C8DH, can be decomposed using a superheated steam decomposition apparatus.

Claims

1. Formula I - (CF 2 ) n A method for treating iodofluorocarbons represented by -I (wherein n is an integer from 2 to 12), The iodofluorocarbon is reduced to the corresponding hydrofluorocarbon by reacting it with alcohols in the presence of a base; The resulting reaction solution is separated into an aqueous layer and an organic layer containing the hydrofluorocarbon by adding water; then The aforementioned organic layer is subjected to a decomposition treatment that yields hydrofluorocarbons to hydrogen fluoride and carbon dioxide; A method that includes the act of doing so.

2. The method according to claim 1, wherein the alcohols are a mixture of methanol and isopropyl alcohol.

3. The method according to claim 1, wherein the organic layer is subjected to superheated steam decomposition treatment to decompose the hydrofluorocarbon into hydrogen fluoride and carbon dioxide.

4. The method according to claim 3, wherein the superheated steam decomposition treatment is performed at a temperature of 880°C or higher.

5. The method according to claim 1, further comprising the step of neutralizing the generated hydrogen fluoride and / or carbon dioxide.

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