DE4022526A1 - Dehalogenating of material contg. organo-halogen cpds. - by mixing with solid particles which contain sodium or potassium - Google Patents

Abstract

Process for de-halogenating material contg. cpds. in a soln. or in gaseous form of organo-halogens, involves bringing the material to be treated into contact with particles of an inert solid material which contains sodium or potassium. The material to be treated is held at a temp. of between 20 and 160 deg. C pref. between 40 and 120 deg. C and together with the treatment medium is poured through a chute made from a material which is resistant to alkalis or alkali metals. This treatment lasts for between 120 min and 1 min but preferably between 60 min and 10 min..

Description

The invention relates to a method for dehalogenating of a treatment good from dissolved or gaseous or present in gas mixtures Organohalogen compounds by contacting the Treated goods with particles of an inert Solid sodium or potassium as Treatment agent at room temperature or higher Temperature, optionally under inert gas.

So far there are liquid halogen-containing detoxifiers organic compounds, e.g. B. halogenated Transformer oils, essentially two Process types:

In the first procedure, the contaminated transformer oil losing this valuable substance in one High temperature incinerator burned. This Technically it is very complex, it will be natural raw materials destroyed and the Recycling cycle withdrawn.

In the second method, the contaminated transformer oil detoxified by treatment with a sodium dispersion (DE-PS 28 13 200). Here, the transformer oil from the temporarily taken out of service transformer and for Treatment plant can be transported.  

Higher temperatures are effective during the treatment (about 180 ° C) on the material to be treated, which it in change in some cases so that a Cleaning operation, e.g. B. filtering over Bleaching earth, must be connected.

Procedures have already been proposed organohalogen compounds by means of inert Supported alkali metal such as sodium or Potassium to be broken down by treatment in a stirred kettle.

For example, US Pat. No. 4,639,309 describes the Possibility of solutions of organic halogen Connections by adding sodium and then Sand or by adding a sodium-doped Destroy sand and then the liquid material to be treated to separate from solids.

For this, organochlorine compounds are used in strong dilute solutions in a batch mode reacted quantitatively with sodium in a stirred kettle. In principle, according to the procedure described above the melting point of sodium or potassium and worked on them with a large excess will. Because the stirred tank has mechanically moving parts and sand is abrasive, is damaged by Container material and agitator to be expected. Through the Abrasion can result in the finest suspended matter Difficulty separating the liquid phase can prepare. The abrasive properties of the sand are called required to the total amount of sodium due to ongoing abrasion by stirring to make available.  

Since in the known procedure large amounts of sand are needed, this means that the mechanical Separation of material to be treated and solid Difficulties because of the large to be funded Solid quantities are to be expected.

The object of the invention is such Avoid disadvantages and an improved process Find.

The invention accordingly relates to a method for Dehalogenation of a treatment good from dissolved or gaseous or in gas mixtures Organohalogen compounds by contacting the Treated goods with particles of an inert Solid sodium or potassium carried as Treatment agent at room temperature or higher Temperature, optionally under inert gas. The procedure is characterized in that the material to be treated at temperatures of 20-160, preferably 40-120 ° C, by at least one as the treatment agent Pillar made of alkali metal and alkali-resistant material with a dwell time in the Range of 120-1, preferably 60-10 minutes. the treatment agent 1-50, preferably 10-30 % By weight of the alkali metal, based on the weight of the inert carrier, contains and the amount of the bed so it is measured that the alkali metal content is sufficient to bind the halogen contained in the material to be treated.  

The atomic ratio of sodium to chlorine in Treated goods depend on the respective Reaction partner for the sodium. It varies from 1: 1 to 3: 1, using the higher ratios are, if at the same time a sodium consumption for Side reactions (such as ethylate formation) is expected.

The inventive method allows temperatures to choose, compared to the previously known relevant process usual reaction temperatures are much lower. Compared to the otherwise often selected application of sodium dispersion brings that The inventive method has the advantage that on a no liquid dispersant as auxiliary can be. Furthermore, the process does not include any moving parts, which in particular the Maintenance effort can be significantly reduced.

Despite that, due to the inert carrier solids significantly increased surface area of sodium is its Reactivity towards condensed water in comparison significantly reduced to pure sodium. This makes it easier the handling. By cascading several structurally identical, filled with sodium on a solid support Columns can be used quantitatively ensure the sodium used.

Basically all common ceramic Carriers as used in catalysis, advantageously as an inert carrier for the alkali metal be used.  

Aluminum oxides, activated carbon, common salt, calcined soda, silicas or zeolites in Powdered or in the form of granules up to 6 mm Diameter.

It is understood that the provided according to the invention Specifications for treatment temperature, residence time and Alkali metal content of the treatment agent each Treatment items are to be adjusted. Is to be taken as a basis its reactivity to the chosen one Alkali metal. The general rule is that one Treatment temperature, residence time and Alkali metal content of the treatment agent at higher chemical reactivity of the material to be treated low chooses, and vice versa.

The apparatus design of the reactor column follows that Requirements of the method according to the invention. So can provide that a heated column is used, to be a cheap one for slow-moving items Achieve implementation speed. The The reaction column points over her in the lower part Cross section of a gas and liquid permeable plate-shaped element, which as a support for the Filling the treatment agent.

It has proven to be cheap, liquid Treat items from bottom to top through the column send; gaseous substances or mixtures of substances can flow through the column in any direction.  

An essential additional within the scope of the invention Design relates to the regeneration of the carrier for the alkali metal after consumption of the latter. Accordingly is a method for recovering the carrier of the im described method used treatment agent characterized in inert form that the Treatments one after the other

• a) an inert solvent,
• b) a lower alcohol, and - if water insoluble carriers - still
• c) water

rinses and the residue 30 min. to 2 hours at 100- 400 ° C dries.

The method can u. a. be subjected to:

• - Solid or liquid organohalogenous Compounds, each dissolved in solvents,
• - Pure gaseous organohalogen compounds and
• - Gas mixtures containing Organohalogen compounds.

The inherent advantages of the method according to the invention can contain PCBs using the example of dehalogenation Transformer oils are illustrated.  

So far, polychlorinated biphenyls (PCB’s) because of their favorable electrical properties, such as e.g. B. high insulation and non-flammability, in Transformers used. In the meantime one is closed realizes that the polychlorinated Biphenyls are hazardous to health and that of them in the event of a polychlorinated fire Dibenzofurans are highly toxic. By collecting this Danger potential was started, against PCB replace mineral transformer oils or silicone oils.

However, the replacement transformer oil is mostly here with remnants of PCB that remained in the transformer were contaminated and must therefore also be classified as be viewed as problematic. It also happens that uncontaminated insulating oils at one at intervals cleaning (drying, separation of Solids) with PCB from the cleaning system be contaminated. This also does one Treatment necessary for detoxification.

It is shown using the example of transformer oil detoxification complete process, starting with preparation of the treatment agent until the regeneration of the Carrier explained.

example 1

The carrier material α-Al ₂ O ₃ (type XL 129, Rhône Poulenc) in the form of a granulate with an average diameter of 3 mm and a surface area of 95 m ² / g is first 2 hours at 400 ° C under normal pressure in a muffle furnace dried. In parallel, sodium is liquefied by heating under inert gas.

The one presented in a rotary tube and in mixed motion staggered granulate is opened under an inert gas stream 150 ° C heated. 30 wt .-% sodium, based on that Weight of the inert carrier, are melted and added to the agitated granules. After 30 minutes it is Granules, recognizable by their black color, with finely divided sodium coated. That with sodium coated carrier material is now in a heatable vertical treatment column (height 50 cm) made of steel with a volume of 1 l filled. The Treatment material, a mineral transformer oil with a The content of 1 wt pumped through the column (column temperature 120 ° C, Contact time 1 h). The PCB content of the transformer oil was able to with a single pass to below the detection limit be lowered.

The reusability of the cleaned transformer oil could in an investigation by an independent institute beeing confirmed.

Surprisingly, there is also regenerated granulate from the process of Example 1 as excellent proven suitable. Both the recoatability with 30% by weight of sodium, based on the weight of the granules, as also the dehalogenation of the same material as in Example 1 was unexpectedly successful.  

The pellets were regenerated by

• a) rinsing with hexane,
• b) rinsing with ethanol and
• c) Rinsing with water and then one hour Drying at 300 ° C.

In the context of the invention comes the right coating of the carrier material to special importance. It has shown in the course of development that with some possible ways of working seem unsatisfactory Dehalogenation results could be achieved. It has not proven particularly useful to provide sodium and liquefy and then add pellets, Submit pellets and add solid sodium to then heat up, submit pellets, one with Add isopropanol purified sodium and then heat up.

The poor suitability was based in all 3 cases the fact that only small amounts of sodium can be applied were, so that only a shiny silver pellet from a wafer-thin layer of sodium with less specific surface resulted.

Rather, the optimal coating method has been the in described in this example result in a) -c), although the last critically discussed methods are basically applicable.  

Example 2

An attempt was made with an analog US Pat. No. 4,639,309 prepared Na-coated sand in a column dehalogenate.

200 g of a solution of chlorobenzene in xylene (equivalent to 10,000 ppm organically bound chlorine) are passed within 20 minutes from bottom to top over the column heated to 60 ° C., already used in Example 1, containing a bed of granulated zeolite, trade name MS 330, pumped with an average particle diameter of 1.4 mm and a specific surface area of 1.1 m ² / g. The zeolite was first dried in a muffle furnace at 400 ° C. for 4 hours and then coated with 8% by weight of sodium, based on the amount of granules used. During the treatment it is purged with nitrogen only until complete wetting of the sodium-coated carrier material with the solution is ensured. After allowing the column to flow through twice, chlorobenzene could no longer be detected (detection limit = NWG = 10 ppm).

Example 3

In addition, a zeolite powder (trade name Wessalith P, Degussa AG, surface area: approx. 30 m ² / g) was used for coating with sodium. The powder was dried for 2 hours at 600 ° C. under normal pressure in a muffle furnace and coated with 5% by weight sodium, based on the amount of zeolite powder used. The reactivity of the sodium is increased so that work must be carried out under the strictest exclusion of oxygen.

Due to this great reactivity, this is suitable coated powder excellent for breaking down organic bound halogens, which are otherwise very difficult to degrade are.

The powder coated with sodium is in the in Example 1 mentioned a treatment column heated to 50 ° C filled. A solution of 5000 ppm becomes organic bound chlorine-containing methylene chloride in hexane pumped from the bottom upwards, the Contact time is 40 minutes. The rate of degradation of the organic bound chlorine lies after two Let the solution run through at <99%.

Example 4

The α-Al ₂ O ₃ granulate used in Example 1 is dried for 3 hours at 150 ° C. and 32 mbar in a vacuum drying cabinet and then coated with 31% by weight sodium, based on the amount of Al ₂ O ₃ granulate used.

Dechlorination of chloroethane, dissolved in Hexane (equivalent to 50,000 ppm organically bound Chlorine) in that described in Example 1 Treatment column made of steel, which with the sodium-coated granules was filled. At a The temperature of 60 ° C is reached when flowing through the column from top to bottom and a residence time of the solution in the column of 10 min. a degradation rate below Detection limit achieved.  

Example 5

An α-Al ₂ O ₃ granulate of the type SCM 99 XT (average particle diameter 2.5 mm and specific surface area 110 m ² / g) regenerated according to Example 1 is dried at 150 ° C. and 26 mbar for 2 hours. In the rotary tube furnace, the granules are heated to 150 ° C. under an inert gas stream and liquid sodium is added until 30% by weight sodium, based on the amount of granules used, has been taken up.

After decanting in two series Treatment columns made of steel of the example 1 Type used is at a temperature of 110 ° C a transformer oil doped with 10,000 ppm PCB each from pumped down through the column, the Contact time is 15 minutes. Here could after once flowing through, no organically bound chlorine or PCB can be detected more.

Example 6

Sodium chloride with a grain size of 0.3-0.6 mm Dried for 2 hours at 200 ° C in a vacuum drying cabinet. Then it is filled into a stirring flask and placed under it Stir at 120 ° C under inert gas (argon) with sodium added until a loading of 10%, based on Cooking salt is reached.

The sodium-coated table salt is colored gray and free-flowing. At 60 ° C a solution of 3-chloro-1-propene (equivalent to 8900 ppm organic Chlorine) in hexane over a sodium-coated one Salt filled column sent.  

With a contact time of 20 minutes there was none in the eluate organically bound chlorine more detectable.

Example 7

α-Al ₂ O ₃ granulate type SCS 79, Rhône-Poulenc, with an average diameter of 3.0 mm and a surface area of 98 m ² / g, is dried for 3 hours at 150 ° C. and 25 mbar.

Sodium is liquefied under an inert gas stream and added to the granules, which are mixed in a rotary kiln at 150 ° C., until a loading of the α-Al ₂ O ₃ granules of 25% by weight sodium, based on the amount of granules used is. The sodium-coated granulate is filled into the treatment column made of steel (according to Example 1) and heated to 50 ° C.

A CFC gas F131 (= trichlorofluoroethylene) is with Diluted argon as an inert gas so that 5 vol.% Halogen are available. The gas is carried through the column mentioned a flow rate of 15 l / h. Here a degradation rate of 85% is achieved.

When increasing the column temperature to 70 ° C and otherwise same degradation was able to achieve a degradation rate organic chlorine of <99% can be achieved.  

Example 8

Anhydrous Na ₂ CO ₃ is placed in a stirred vessel under argon and liquid sodium is added with stirring at 125 ° C. until a sodium content of 7%, based on Na ₂ CO ₃ , is reached. The gray, free-flowing, sodium-coated Na ₂ CO ₃ is filled into the heatable treatment column according to Example 1. At room temperature, a solution of chlorobenzene with 10,000 ppm organically bound chlorine in hexane is then passed over the treatment column with a contact time of 20 minutes. The organic chlorine content of the eluate is 5100 ppm.

At a column temperature of 90 ° C and otherwise organic chlorine Content of the leaking solution below the detection limit.

Example 9

200 g of activated carbon type Epanit, powdered, are 3 hours dried at 180 ° C in a vacuum drying cabinet and in placed in a stirred vessel under inert gas at 130 ° C. While stirring, liquid sodium is added until 35% sodium, based on activated carbon, are added. The coated activated carbon is gray-black and free-flowing. A sample left in the air glows a few moments. The coated activated carbon is placed in a treatment column (as in example 1) filled and then a chlorobenzene solution in hexane (10,000 ppm organically bound chlorine) Room temperature and a contact time of 20 minutes at 83% dechlorinated.  

By increasing the temperature in the as preferred claimed area can be the same Experimental arrangement increase the degradation rate to <99%.

Example 10

SiO ₂ pellets with a diameter of 4-7 mm are dried in a muffle furnace at 400 ° C. for 2 hours, placed in a stirred vessel at 140 ° C. under argon and mixed with 5% liquid sodium, based on the pellets. After stirring for 60 minutes, the pellets are coated evenly black. The sodium-coated SiO ₂ pellets were introduced into the heatable treatment column described in Example 1. A chlorobenzene solution in hexane (10,000 ppm organically bound chlorine) is allowed to flow from bottom to top through this at 120 ° C. and a contact time of 20 minutes.

The Cl content in the eluate is below the detection limit.

Example 11

An attempt was made with an analogous US patent 46 39 309 produced Na-coated sand in a column Perform dehalogenation.

200 g sand (grain diameter 0.3-2 mm) are in 500 ml Xylene heated to 120 ° C and 20 g of sodium added. The silvery shining, the sodium-containing carrier transferred into a column under a protective gas atmosphere and then 100 ml of a 1000 ppm organically bound Chlorine-containing solution of chlorobenzene in hexane given up. Dechlorination was up to 30% at 60 ° C possible.  

The excess sodium, based on chlorine, is included 8: 1, which indicates poor wetting (low Surface and high layer thickness).

Example 12

Based on the experience from example 11, an attempt was made to Sand in the optimal mode of operation according to the invention coat. For this purpose, 200 g of sand are heated to 150 ° C and 20 g sodium liquid added. The sodium draws on the surface of the sand in silver gray color. After transferring this sodium coated The carrier material was again chlorobenzene in hexane (with 10,000 ppm organically bound chlorine) over the Column headed. In this case too Dechlorination cannot be performed quantitatively.

Claims (6)

1. A process for dehalogenating a material to be treated from dissolved or gaseous or organohalogen compounds present in gas mixtures by contacting the material to be treated with sodium or potassium carried by particles of an inert solid as a treatment agent at room temperature or elevated temperature, optionally under inert gas, characterized in that the material to be treated is characterized in that Temperatures of 20-160 ° C, preferably 40-120 ° C, passes through at least one column containing the treatment agent as a bed of alkali metal and alkali-resistant material with a residence time in the range of 120-1, preferably 60-10 minutes the treatment agent contains 1-50, preferably 10-30 wt .-% of the alkali metal, based on the weight of the inert carrier, and the amount of the bed is dimensioned so that the alkali metal content is sufficient to bind the halogen contained in the material to be treated. 2. The method according to claim 1, characterized, that as a carrier for the alkali metal aluminum oxides, Activated carbon, table salt, calcined soda, silicas or zeolites in powder form or in the form of Granules with a diameter of up to 6 mm are used becomes.   3. The method according to claim 1 or 2, characterized, that treatment temperature, residence time and Alkali metal content of the treatment agent higher chemical reactivity of the material to be treated chooses low, and vice versa. 4. The method according to claims 1 to 3, characterized, that you use a heated column and the Pouring the treatment agent on an im lower part of the column across its cross section attached, gas and liquid permeable, plate-shaped element, preferably a sieve or a frit. 5. The method according to claims 1 to 4, characterized, that you can treat liquid from bottom to top through the pillar. 6. A method for recovering the carrier of the treatment agent used in the process claimed above in an inert form, characterized in that the treatment agent is used in succession

• a) an inert solvent,
• b) a lower alcohol - as well as in water-insoluble carriers
• c) Rinsing water and drying the residue at 100-400 ° C for 30 minutes to 2 hours.