JPH0426632A - Dehydrohalogenation of organic compound - Google Patents

Abstract

Organohalides are dehalogenated by bringing an organohalide or a mixture of two or more organohalides into contact with an alkali hydroxide in an alcoholic solution and in the presence of a catalytically effective amount of a heterogeneous transfer hydrogenolysis catalyst. The process can be carried out at relatively low temperatures (50 DEG - 150 DEG C) and at low pressures. <IMAGE>

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for the dehalogenation of organic compounds. More specifically, the present invention relates to the decomposition and detoxification of organic compounds containing halogen atoms.

[Background of the invention]

Organic halogenated compounds are obtained in relatively large amounts as by-products of various industrial processes. Representative, but non-limiting, examples of such compounds include chloro- or bromoaromatic compounds, such as polychlorinated and polybrominated biphenyls (PCB and PBB), polychloroheterocyclic compounds. , such as P-hexachlorocyclohexane and organic solvents such as chlorobenzene. These products are toxic and hazardous and should be disposed of by effective means.

Disposal of PCBs by incineration is expensive due to the thermal stability of these compounds, and it means that highly toxic substances such as 2,3,7,8-tetrachlorodibenzo-p-dioxin are released during the process. It is complicated because

Only a few specialized incinerators are permitted to operate such hazardous materials, and the facilities where these processes take place have been accused of causing environmental pollution ( New 5cientist, 14
．． 10.89).

These problems make it difficult to use halogenated organic compounds, especially PCs.
Much effort has been made in the art to develop effective and safe methods for the chemical degradation of B.

[Conventional technology]

Many methods have been provided in the art, including methods for the chemical treatment and reclamation of oils and fluids containing varying amounts of halogenated hydrocarbons. This type of method can be divided into two main categories. One type of method involves reductive dehalogenation, where the organic material is treated with hydrogen gas (e.g., US 4,840,721, US
4,818,368, BP 306,164 and EP
299,149), or other hydrogen-donating compounds, such as alkali hydrides (GB 2,189,804), hypophosphites (US 1, 618,686) and sodium borohydride (US 6,794, 928). These methods offer several significant drawbacks. This is because they usually involve complicated hydrogenation steps using explosive gases at high temperatures and pressures, which must be carried out in specific reactors, or they are not suitable for economic and safety reasons. This is because it involves the use of certain reagents which are disadvantageous in industry due to the

Furthermore, HCl2 is produced in the process, which adds additional complexity.

The second type of dehalogenation method can chemically cause the decomposition of carbon-halogen bonds and lead to the conversion of organic halogens to inorganic halogens bound to metals, alkaline earth metals. , reactions of alkali metals or compounds of these metals. Some examples of such methods are the use of metals or metal compounds such as tin, lead, aluminum, chloroaluminates, titanium, aluminum oxide, etc. (UP 277.858
, EP 184.342 and US 4,435,379)
. The most used compounds are alkali metals and alkali metal compounds, such as sodium/sodium hydroxide (US 4.755,628, CA L1B5,265 and UP 99,951), sodium naphthalene, sodium polyethylene glycol (EP 140,999).
and EP 60,089), sodium carbonates, bicarbonates, alcoholates, etc. (US 4,631,183 and EP 306,398).

This type of method also presents considerable drawbacks.

For metals of low reactivity, dehalogenation is usually performed for the decomposition of stable carbon-chlorine bonds and for contacting the metal with organic compounds in the form of molten salts, finely divided dispersions, etc. This includes the high temperatures of 500 to 1000°C required for

On the other hand, active metal compounds can be reacted at lower temperatures of 300-600<0>C. However, large amounts of expensive reagents are required, and the method involves complicated and expensive separation and purification steps.

Metal compounds that are capable of inducing dehalogenation at low temperatures are highly reactive, and their handling and use is therefore necessary to avoid the risk of uncontrolled exothermic decomposition of these compounds. Limited by some harsh anhydrous conditions and the need for an inert atmosphere. Therefore,
These methods are very dangerous and expensive.

It is therefore clear that it would be highly desirable to provide a method for the dehalogenation of waste organic compounds that is simple and inexpensive.

[Summary of the invention]

It is an object of the present invention to provide a method which does not require specially manufactured equipment and which is simple, cheap and non-hazardous, and which overcomes the drawbacks of the prior art.

The method for dehalogenation of organic halides of the present invention comprises combining an organic halide or a mixture of organic halides with an alcoholic solution in the presence of a catalytically effective amount of a heterogeneous transfer hydrogenolysis catalyst. The method comprises reacting with an alkali hydroxide.

[Specific description of the invention]

Preferably, the alcohol found in the alcoholic solution is a lower alcohol. Preferred alkali hydroxides are
Sodium or potassium hydroxide, although of course other hydroxides can also be used.

Regarding the catalyst, any transfer hydrogenolysis catalyst may be used as long as it is provided in a catalytically effective amount. A preferred catalyst is, for example, palladium on carbon. This catalyst is usually supplied as 5% or 10% palladium on carbon.

The method of the invention is very convenient as far as temperature is concerned. The preferred reaction temperature is 50°C to 150°C. Although higher temperatures are used, this is not necessary for boat fishing. Similarly, the reaction can proceed at low pressure, for example in an open vessel at atmospheric pressure. It is usually preferred to carry out the reaction in a sealed reactor under pressures below 3 to 4 atmospheres. As will be clear to those skilled in the art, this is a significant advantage over prior art techniques which require significantly higher temperatures and pressures.

Furthermore, the methods of the invention do not require anhydrous conditions and can be conveniently carried out in the presence of high water concentrations (eg, 25%). This is an additional advantage of the present invention since anhydrous conditions require effort and expense.

Preferably, the concentration of organic halide in the reaction mixture is from 0.1 to 10% of the reaction mixture, and the alkali hydroxide is present in theoretical excess over the organic halide. Typically, the concentration of organic halide remaining in the reaction mixture under normal conditions is below the detection limit.

The catalyst used in the reaction is quantitatively recovered after completion of the reaction, washed with water and reused in the subsequent reaction. Therefore, this method is also very effective in terms of catalyst utilization.

The present invention also includes a method for the purification and reclamation of fluids contaminated with organic halides, the method comprising:
Contacting the fluid to be purified with a theoretical excess of alkali hydroxide relative to the organic halide in an alcoholic solution in the presence of a catalytically effective amount of a heterogeneous transfer hydrogenolysis catalyst. It consists of forcing. Examples of such contaminated fluids are mineral oils, silicone oils, lubricating oils, gas oils, transformer oils, etc., which are contaminated with chlorinated organic compounds in a concentration range of about 0.1-60%.

These and other features of the invention will be better understood from the following illustrative but non-limiting example. In the following example, commercially available dielectric liquid Pyrale
ne'' was used to determine the effectiveness of the present invention.
Pyrazino contains approximately 40% by weight of trichlorobenzene and 60% by weight of a mixture of PCBs.

The total chlorine content in pyrazino is approximately 60%.

Quantification of total PCB content in pyrazinos was performed using sodium aluminum hydride for analytical reductive dehalogenation according to A. Kachen, 0. B]aste
r and B, Marek (Fresenins Z, A
nal, Chem, +326+747 (1987)
) was carried out according to the method. A value of 22 gw of dehalogenated biphenyl was obtained.

0.2 d (286 ■) of open-earth pyrazino, 780 mg (19,5 mmol) of sodium hydroxide and 30 ■ of 10% palladium on carbon (palladium at 0.03 mA) were placed in a glass reactor and 2 d of methanol .5 kura was added.

Purge the reactor twice with nitrogen, seal, and incubate for 10
Heated to 0°C for 16 hours. Upon completion of the reaction, the catalyst is separated by filtration or centrifugation and purified with tetrahydrofuran (THP).
) and methanol, and the collected filtrates were subjected to GC and HPLC analysis.

No observable residues of pyrazino were detected. The organic products were benzene and biphenyl (68
24.5% of the starting pyrazino). The dehalogenated reaction mixture was subjected to GC analysis using an EC detector. The chromatogram (FIG. 1) shows that - after dehalogenation, hardly any components of the starting pyrazino remained in detectable amounts. 12ppm of pyrazino
The chromatogram of the solution (Figure 2) consists of 8-10 components with retention times of 43-206 minutes. 10 of these ingredients
Considering that the % is still observable, the concentration of the pyrarene component is 120. OOppm to 1. opp
It can be concluded that the decrease has been reduced to 9 m.
9.999% decomposition).

■-I Example 1 was repeated. However, no catalyst was introduced. G.C.
In the -EC analysis, no change in the starting pyrazino was observed, and no biphenyl was detected as observed in the GC-FID and HPLC analyses.

There wasn't. No residual pyrazino was observed. That is 1
．． o Indicates PCB content below ppm. Biphenyl (24.5% by weight) was determined by GC and HPLC, indicating complete hydrogenolysis of the PCB.

■-Repeat Example 1. However, in addition to methanol, 0.25
Added iffi water. After the reaction was complete, biphenyl (25% by weight) was measured. GC analysis showed that no residual pyrrene components remained. Low retention time (2
0 min) is 1/1 smaller than the starting pyrazino.
0,000 was detected on the lower concentration scale.

1-5 pyrazino 1 mff1 (1,475 g), 3.6 g (90 mmol) of sodium hydroxide and 50 n+g of 10% palladium on carbon were placed in a 100 m2 flask equipped with a magnetic stirrer and a reflux condenser. Methanol 8 mf
1 and 2 ml of water were added and the mixture was heated with stirring to 80° C. for 18 hours. On completion of the reaction, the catalyst was separated and the filtrate was analyzed by GC.

No remaining pyrazino was detected by GC-EC detector. Trace amounts of product were detected at low retention times.

After the completion of the reaction, the biphenyl 385■ (26%) was analyzed by GC.
Found in the mixture by analysis.

Flame - ■ The catalyst from Example 5 was washed with water and THF and then dried under vacuum at 100°C to a constant weight (5
7■). This catalyst was mixed with 1.54 g of pyrazino, 3.6 g of sodium hydroxide, 10 ml of methanol and 2 I of water.
d into the reaction flask.

This mixture was heated to 80°C for 18 hours.

After completion of the reaction, 308 cm (20% by weight) of biphenyl was measured in the mixture, indicating that the recycled catalyst was effective.

Example 1 was repeated. However, pyrazino 0.2 d (28
0.5 mβ of mineral oil contaminated with 0 mg) was added to the dehalogenation mixture. After the reaction was completed, the mineral oil was separated from the methanol by phase separation. The solid matter was washed with methanol, and the collected methanol fraction was subjected to GC.
and subjected to HPLC analysis. Dissolve the oil phase in THF,
Then, it was subjected to GC and HPLC analysis.

No observable residue of pyrazino was detected in the solution. The organic products are mainly benzene and biphenyl (68,
6mg), which is 24.5% by weight of the starting pyrazino.
Met.

Various halogenated compounds were dehalogenated according to the following method.

halogenated compound (1 mmol), sodium hydroxide 0.72 g (18 mmol) and 10% carbon”
10 mg of Nipalladium (0.01 mAtom Pd) was placed in a glass reactor and a few liters of methanol was added to the mixture. The reactor was purged twice with nitrogen,
Seal and heat to 100°C for 16 hours.

The results of these reactions are summarized in Table 1 below.

Lium Ig (18 mmol) was used. After the reaction is complete,
No residual pyrazino was detected by GC (EC detector) analysis. Biphenyl (70.5 μm, 24.5% by weight) was determined by GC and HPLC, indicating a very effective dehalogenation reaction.

±-Repeat example 1. However, 2.5 ml of ethanol was used as the hydrogen donor and solvent. After completion of the reaction, no observable pyrazino residue was detected in the solution using GC (EC detector) analysis. Biphenyl (70,
0■, 24.8% by weight) and benzene in GC and HP
It was the main organic product in LC analysis. A small amount of additional unidentified organic product eluted with a low retention time (24 minutes) in the GC analysis.

Defluorination of flame-bearing fluoroaromatic compounds also occurs using similar reaction conditions. For example, 190 μm (1 mmol) of 4,4' difluorobiphenyl was subjected to the reaction conditions described in Examples 8-20. However, long reaction times were required. No starting difluorobiphenyl was detected in the solution when the reaction was continued for 70 hours. 4
-Fluorobiphenyl (17 mg, O, 1 mmol, 10%) and biphenyl (123 mg, 0.8 mmol) were determined by GC as the only products in the reaction.

In the above method, environmental considerations are met regarding high efficiency of PCB decomposition and also recycling or disposal of any other reagents involved in this method.

The dehalogenated organic product is used as a heat source and contributes an additional energy source to the process. Inorganic products are harmless salts such as sodium chloride and sodium formate. The latter is a useful and salable product, and the profits obtained can reduce operating costs.

A flow diagram for the dechlorination unit of the present invention is shown in FIG. After completion of the reaction, the working process begins with evaporation of the solvent through the cooler (1) and recycling of methanol using the solvent still and cooler (2). The non-volatile residue is washed with water and sent to a liquid-liquid extraction unit useful for the recovery of refined oil. The basic aqueous solution can be reused in the subsequent dehalogenation step or neutralized with hydrochloric acid and subsequently dried by evaporation of water. Methanol is then added to allow separation of the soluble sodium formate from the sodium chloride, which is then disposed of as waste.

The above examples are illustrative and do not limit the invention. Many modifications can be made in the method of the invention:
For example, different compounds may be dehalogenated using different catalysts, solvents and hydroxides, different reaction conditions may be used, or different fluids may be purified within the scope of the present invention.

(I8)

[Brief explanation of the drawing]

FIG. 1 is a chromatogram showing the change in composition of the starting pyrazino with time after dehalogenation; FIG. 2 is a chromatogram of a 12 ppm solution of pyrazino; and FIG. 3 is a chromatogram according to the invention. 1 is a flowchart for a dechlorination unit of FIG. Explanation of reference numbers in the drawings: 1.2. and 3...cooler.

Claims (1)

[Scope of Claims] 1. A method for dehalogenating an organic halide, comprising: treating an organic halide or a mixture of a plurality of organic halides in the presence of a catalytically effective amount of a heterogeneous transfer hydrogenolysis catalyst; contacting an alkali hydroxide in an alcoholic solution at: 2. The method according to claim 1, wherein the alcohol solution comprises a lower alcohol. 3. Claim 1 or 2, wherein the alkali hydroxide is selected from the group consisting essentially of sodium hydroxide and potassium hydroxide.
Method described. 4. The method according to any one of claims 1 to 3, wherein the transfer hydrogenolysis catalyst is a palladium on carbon catalyst. 5. The method of any one of claims 1 to 4, wherein the dehalogenation reaction is carried out at a temperature of about 50° to about 150°C. 6. The method of claim 5, wherein said dehalogenation reaction is conducted at a pressure of about 4 atmospheres or less. 7. Claim 5, wherein the reaction is carried out under atmospheric pressure containing air.
Or the method described in 6. 8. A method according to any one of claims 1 to 7, wherein the concentration of organic halide in the reaction mixture is between 0.1 and 10% of the reaction mixture. 9. The method according to any one of claims 1 to 8, wherein the reaction is continued until 10 ppm or less of organic halide remains in the reaction mixture. 10. A process according to any one of claims 1 to 9, wherein the catalyst is recovered, washed and reused in subsequent reactions after completion of the reaction. 11. A method for the purification and regeneration of fluids contaminated with organic halides, the fluid to be purified comprising:
A method comprising contacting a stoichiometric excess of alkali hydroxide relative to an organic halide in an alcoholic solution in the presence of a catalytically effective amount of a heterogeneous transfer hydrogenolysis catalyst. 12. The method of claim 11, wherein the fluid to be purified comprises mineral oil, silicone oil, lubricating oil, gas oil, transformer oil, and the like.