DE29619606U1 - Catalyst for the oxidation of organic and inorganic compounds in the aqueous phase - Google Patents

Description

Catalyst for the oxidation of organic and inorganic compounds in aqueous phase

Description

The invention relates to a catalyst for the oxidation of organic and/or inorganic compounds contained in water.

Many organic syntheses and industrial production processes are carried out in the aqueous phase, resulting in wastewater that is contaminated with starting materials, intermediates, by-products and end products. Other wastewater contaminated with organic substances is produced during the isolation and processing of the products. All of this wastewater and sludge must be cleaned before it is released into the environment. The usual cleaning method, if the wastewater is discharged into the sewer (indirect discharge), is biological cleaning in sewage treatment plants. In many cases, however, the wastewater contains substances that cannot be broken down in sewage treatment plants or only very slowly, e.g. polycyclic aromatic hydrocarbons (PAH) and adsorbable organic halogen compounds (AOX).

In addition, groundwater and seepage water can also contain dissolved organic ingredients that are difficult or impossible to biodegrade, leading to ever-increasing disposal problems.
Typical pollutants contained in waste water, groundwater, seepage water or sludge are polycyclic aromatic hydrocarbons, halogenated

Hydrocarbons, mineral oil hydrocarbons, cyanides, phenols, heavy metals, pesticides, polychlorinated biphenyls, etc.

Polycyclic aromatic hydrocarbons (PAHs), adsorbable organic halogens (AOX), polychlorinated biphenyls (PCBs), ethylenediaminetetraacetic acid (EDTA) and organic amines are particularly difficult to break down pollutants.

A number of wastewater treatment processes are known from the state of the art, such as: adsorption processes, especially with activated carbon and activated adsorbents, biological purification, precipitation/flocculation, reverse osmosis, evaporation/drying.

In recent years, the oxidative degradation of pollutants by chemical wet oxidation has become increasingly important.

Processes are known in which the oxidative effect of hydrogen peroxide and ozone can be increased by catalysts. Metal oxides and metal salts, preferably of transition elements (e.g. Fenton's reagent, oxides, sulfates and chlorides of copper, zinc, nickel, iron, tungsten) are used as catalysts (DE-OS 43 14 521, DE-OS 29 27 911, DE-OS 27 35 892, DE-OS 4118 626). The disadvantage here is the formation of large quantities of contaminated metal sludge, e.g. iron hydroxide sludge, which must be specially disposed of or disposed of. Furthermore, the oxidation catalyzed by iron(II) ions (Fenton's reagent) requires an acidic pH range, which has a detrimental effect on material resistance (corrosion) and fish toxicity.

There is often a risk that the catalysts will be deactivated by the suspended matter often contained in the waste water. The known wet oxidation processes are usually carried out under increased

temperatures and pressures, which leads to high investment and operating costs.

In processes operating in lower temperature (150-175 ⁰ C) and pressure ranges (10-20 bar), in addition to the presence of a catalyst, the pH value must be adjusted to 0.5 -1.5 to enable oxidation.

Nevertheless, these processes do not achieve complete oxidation of the pollutants into water and carbon dioxide.

Processes are also known in which the oxidation is carried out in the presence of full metal catalysts (DE-OS 4131 596,

DE-PS 195 03 865).

Oxidation on activated carbons is also described, whereby the catalytic effectiveness of the carbons is increased by using carbon supports that are anodically oxidized and then doped with molybdenum VI and/or tungsten VI and/or vanadium V compounds. The salt compounds of the elements mentioned are used to dope the supports (DE-OS 34 30 484). Metals or metal oxides of the elements platinum, nickel, titanium, cobalt, manganese, molybdenum, copper and tungsten are also used to dope activated carbon.

The known catalysts for catalytic wet oxidation have the disadvantage that they do not allow complete degradation of the pollutants, particularly in the case of high pollutant loads or pollutants that are difficult to degrade, and the efficiency and service life of the catalysts are limited.

The invention is based on the object of providing an easily produced catalyst for the oxidation of organic and inorganic compounds in water, which is also effective in the presence of high levels of pollutants containing compounds that are difficult to degrade.

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has a high degradation rate and high effectiveness under normal conditions.

This object is achieved according to the invention by a catalyst which contains one or more chelate complex compounds of the elements of the 1st, 2nd, 4th to

8th subgroup of the periodic table of elements.

It has been found that chelate complex compounds of the elements of the 1st, 2nd and 4th to 8th subgroups of the Periodic Table of the Elements are highly effective for the oxidative degradation of organic and inorganic compounds in water. Chelate complex compounds with dichalcogens as ligand atoms are particularly suitable.

Surprisingly, these compounds have a high level of activity under normal conditions and ensure the almost complete degradation of even difficult-to-degrade pollutants such as polychlorinated biphenyls (PCB), volatile halogenated hydrocarbons (VHC), ethylenediaminetetraacetic acid (EDTA), organic amines, pesticides, adsorbable organic halogenated hydrocarbons (AOX) and other oxidizable compounds (COD). It was not foreseeable that these compounds have a high catalytic activity even at a neutral pH value, so that when using the catalysts according to the invention there is no additional salting of the water and the formation of sludge that has to be disposed of is avoided.

The catalysts according to the invention are highly stable against the metal compounds, inorganic salts and suspended matter contained in waste water. The activity of the catalysts is not negatively affected by these substances. As a result, the catalysts have a high catalytic activity and a long service life. The catalyst poisons

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Known heavy metal ions and sulfur compounds surprisingly do not inhibit the catalysts according to the invention.

Particularly suitable catalysts are chelate complex compounds with the same or different ligands, which are selected from the following group: oxyketones, oxyaldehydes, oxyquinones, diketones, enols, oxyacids, dicarboxylic acids, ketocarboxylic acids and their acid esters as well as the analogous sulfur or selenium-containing compounds. The ligands can have an aliphatic, cycloaliphatic, aromatic or araliphatic structure. Chelate complexes with oxygen ligand atoms are preferably used.

Oxyketones, oxyacids, ketocarboxylic acids, dicarboxylic acids and ß-diketones as well as the corresponding acid esters are particularly suitable as chelating ligands.

Examples of these ligands are: glycolates, lactates, citrates, salicylates, oxalates, oxyquinones, o-oxyacetophenone, benzoylacetonate, alkyl acetoacetate.

The ligands of the complexes can be substituted at one or more carbon atoms by one or more of the

the following groups: halogen, nitro, hydroxy, carbonyl, carboxy, alkoxy, aralkoxy, phenoxy, alkyl, aryl and aralkyl, where the carbonyl, carboxy, alkyl and aryl radicals may optionally also be substituted by one or more of the groups mentioned.
25

The chelate complex compounds of iron, vanadium, manganese, copper, cobalt, molybdenum, tungsten, ruthenium, rhodium, palladium, platinum and their mixtures have a particularly high catalytic activity under normal conditions.

Preference is given to one or more chelate complexes of the elements of the 7th and

8. Subgroup used.

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Particularly high degradation rates for organic and inorganic compounds, especially for compounds that are difficult to degrade, are achieved by using chelate complex compounds of oxyketones, oxyacids, ketocarboxylic acids, dicarboxylic acids, ß-diketones, especially dicarboxylic acids and ß-diketones, and the corresponding acid esters with elements of the 7th and 8th subgroups.

Suitable catalysts are, for example, complexes of tris(benzoylacetonato)cuprate(II), tris(alkylsalicylato)ferrate(III), bis(thiobisphenolato)niccolate(II), bis(dialkyl-dithiocarbamato)cobaltate(II),

Tris(oxalato)manganate(III), tris(2-hydroxyacetophenonato)ferrate(III), bis(2-hydroxy-5-methylbenzophenonato)manganate(in).

The catalysts according to the invention can be used as homogeneous or heterogeneous catalysts in fluidized bed, fixed bed or fluidized bed processes.

However, heterogeneous catalysts, especially supported catalysts, are preferred. This allows for optimal use of the activity of the catalysts and a high degradation rate of the pollutants. Activated carbon, polymeric resins, Al ₂ O ₃ , SiO ₂ and zeolites are used as supports, with activated carbon being preferred due to its large BET surface area.

These catalysts are relatively easy to produce. The chelate complex compound can be fixed to the carrier matrix in a known manner by ion exchange, impregnation or precipitation from a solution. The complex compounds are produced in a known manner.

An advantage of the catalysts according to the invention is that they are completely recyclable.

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The catalysts according to the invention are used in particular for the catalytic wet oxidation of organic and inorganic compounds in the aqueous phase. The wet oxidation is carried out in the presence of one or more of the following oxidizing agents: hydrogen peroxide, air, ozone, organic and inorganic peroxides, with hydrogen peroxide being preferred.

The catalysts according to the invention can be used for the oxidative purification of wastewater, process water, drinking water and groundwater containing organic and/or inorganic compounds as well as for the treatment of contaminated aqueous extraction agents from soil washing.

The catalysts according to the invention break down the organic and inorganic compounds into environmentally friendly reaction products. In most cases, depending on the type of pollutants oxidized, carbon dioxide, water, chlorides, sulfates and other salts are formed, as well as some nitrogen-containing compounds such as ammonia, nitrogen oxides and nitrogen. There is no risk of dangerous, toxic or non-biodegradable materials being released into the air, water or soil.

A particular advantage of catalysts is that their use enables the treatment of water that occurs under normal conditions to be carried out cost-effectively through high degradation rates, short treatment times and relatively low use of oxidizing agents. The relatively long service life of the catalyst also ensures long-term stable conditions.

The complex compounds according to the invention optimally catalyze the oxidation of the pollutants even at normal temperature, normal pressure and a pH value of 6 to 7. However, the oxidation can also take place at higher

or low pressures and temperatures and at pH values from 2.5 to 9.5.

Optimum degradation rates are achieved at 20 ⁰ C to 25 ⁰ C, normal pressure and in a pH range of 5 to 7.5.

It is advantageous that acidic starting water can also be fed directly to the oxidation process without prior pH adjustment. After oxidation, this water has a pH value of 7 to 7.5, so that the legally specified discharge conditions are met without additional pH adjustment.

Due to the high activity of the catalyst according to the invention, oxidizable hydrocarbons such as aromatics, phenols, chlorinated hydrocarbons, organic dyes and cyanides are broken down within a short time with the addition of hydrogen peroxide. Even very heavily contaminated waste water with pollutant quantities of 8-12 kg/m ³ COD is effectively cleaned within 30-60 minutes, so that it can either be discharged into the receiving water or reused as process water.
The treatment of organically contaminated water can be carried out in continuous or batch operation.

The outstanding properties of the catalysts are also reflected in the reaction rates achieved when processing water containing phenol. In the catalytic oxidation in the presence of hydrogen peroxide, the phenol is almost completely broken down after just 30 minutes, so that the phenol concentration is well below the limit required by law for indirect discharge.

The catalysts according to the invention also accelerate the oxidative degradation of the pollutants in the presence of UV light. This additional activation of the hydrogen peroxide and the pollutant species can

For particularly difficult to break down pollutants, the degradation rate can be increased even further.

With the catalysts according to the invention, degradation rates of 95% to 99% can be achieved. These catalysts also allow the degradation of organic and inorganic pollutants that are difficult to degrade and that can be present in high concentrations in water and aqueous suspensions. The degradation of the pollutants also takes place in cloudy and colored water with a very complex pollutant matrix.

In addition, organically bound heavy metals can be processed by these catalysts in such a way that the existing heavy metal ions are converted into defined oxidation states and thus become separable, and complexly bound ligands are destroyed oxidatively.

It is also noteworthy that the catalysts according to the invention ensure high degradation rates even with strongly fluctuating pollutant loads, as is usually the case in remediation projects.

The invention will be explained in more detail below using examples, without restricting the catalysts according to the invention to these embodiments.

Examples of implementation

example 1 Preparation of the catalyst:

10 g of tripotassium tris(alkylsalicylato)ferrate(III) are dissolved in 100 ml of water. 50 g of a SiO/Al2CV support material are stirred into this solution and, after a residence time of 10 minutes, filtered off and washed three times with distilled water. The catalyst is then dried.

Use of the catalyst according to the invention:

20 g of the prepared catalyst is added to 1 liter of brown-colored, cloudy wastewater with a phenolic smell (pH= 8).

At temperatures of 20 ⁰ C, 1.8 ml of hydrogen peroxide (30%) was added. After 30 minutes, > 95% of the organic contaminants had oxidized. The treated water was clear, colorless and odorless.

After treatment, the purified wastewater was separated and the catalyst was treated again with the same wastewater. After the same treatment time, the same results were achieved as in the first treatment, which indicates high catalyst activity and service life.

The pollutant values of the untreated and treated water can be found in the table below.

Chemical parameters
(from the original substance) μΦ; Application of the method according to the invention after treatment before treatment <1 BTEX &mgr;§/&igr; 3540 <1 Benzen vsfi 521 <1 Toluen μβ/1 770 <1 Ethylbenzen &mgr;«&Lgr; 184 <1 Xylenes mg/1 2085 0.785 PAH mg/1 14423 <0.005 Phenols _total . 7.6 0.006 Cyanide _gcs . 0.36

Example 2

40 kg of activated carbon doped with sodium tris(benzoylacetonato)niccolate(II) is used to purify groundwater from a tar paper production plant. The groundwater is first separated from the oil phase in a phase separation stage. It is then fed to a pre-cleaning stage in which the water is de-ironed in a known manner. This is followed by fine filtration. The pre-cleaned water is continuously mixed with hydrogen peroxide and then fed into the fluidized bed reactor. The reactor was filled with activated carbon doped with sodium tris(benzoylacetonato)niccolate(II). The hydrogen peroxide is dosed volume-controlled in a quantity of 2.0 l/m ³ of groundwater.
The oxidation takes place at normal temperature and under normal pressure.

The pollutant levels were recorded during treatment. The following table shows the values for the untreated and treated water, which were determined from a variety of measurement results.

Chemical parameters
(from the original substance) μφ Application of the method according to the invention after treatment μφ before treatment <5 Phenol index 1300 <100 MKW μφ 5002 <1 Nuclear power plant μΦ; 27.1 0.4 PAH 1388 <1 VOC 39.9

Example 3

Groundwater from the site of a former pharmaceutical company with a pH value of 3.5 was first passed through a suspended matter filter. Hydrogen peroxide is then continuously added to the water. A dosage of approx. 1.0 l hydrogen peroxide/m ³ groundwater has proven to be advantageous.

The water is then passed through the reactor in which the catalyst support material, consisting of an aluminum silicate support and bis(2-hydroxy-5-methylbenzophenonato) manganate(III), was kept in the fluidized bed.

To prepare the catalyst, 5 kg of aluminum silicate are dispersed with 100 l of water and 1 l of an aqueous solution containing bis(2-hydroxy-5-methylbenzophenonato)manganate(in) is added. The solution is neutralized with sodium hydroxide solution. Then at least

Stirred for 6 hours, filtered and the precipitate washed three times with distilled water. The precipitate is then dried.

The oxidation was carried out under standard conditions.

The pollutant levels of the water were measured during treatment.

The values for untreated and treated water can be found in the table below.

Chemical parameters
(from the original substance) mg/1 Application of the method according to the invention after treatment mg/1 before treatment 0.057 Dichloromethane mg/1 64 < 0.001 Trichloromethane mg/1 0.036 < 0.005 Chorbenzen mg/1 0.15 0.11 Bromochloroethane mg/1 26 0.048 Dibromomethane mg/1 6.4 <0.005 Bromoethane mg/1 2.32 0.011 1,2-Dibromopropane mg/1 1.7 0.005 Benzen mg/1 0.19 <0.005 Toluen mg/1 0.39 <0.005 Ethylbenzen mg/1 0.93 <0.005 m,p-xylene 0.22 <0.005 o-Xylene 0.19

Claims (1)

Protection claims 1. Catalyst for the oxidation of organic and inorganic compounds in the aqueous phase, characterized, that he chelate complex compounds of the elements of the L, 2nd, 4th to 8. Subgroup of the Periodic Table of the Elements or their mixtures contains. 2. Catalyst according to claim 1, characterized in that it contains one or more chelate complex compounds with dichalcogens as ligand atom. 3. Catalyst according to claims 1 and 2, characterized in that it contains chelate complex compounds with identical or different ligands which are selected from the following group: oxyketones, oxyaldehydes, oxyquinones, diketones, enols, oxyacids, dicarboxylic acids, ketocarboxylic acids and their acid esters as well as the analogous sulfur- or selenium-containing compounds. 4. Catalyst according to claims 1 to 3, characterized in that it contains chelate complexes with oxygen as ligand atom. 5. Catalyst according to claims 1 to 4, characterized in that it contains chelate complexes with oxyketones, oxyacids, ketocarboxylic acids, dicarboxylic acids, ß-diketones and the corresponding acid esters as ligands. 4M It M · *« ·· ■* 6. Catalyst according to claims 1 to 5, characterized in that the ligands of the chelate complexes can be substituted on the carbon atom by one or more of the following groups: halogen, nitro, hydroxy, carbonyl, carboxy, alkoxy, aralkoxy, phenoxy, alkyl, aryl and aralkyl, where the carbonyl, carboxy, alkyl and aryl radicals can optionally be substituted by one or more of the groups mentioned. 7. Catalyst according to claims 1 to 6, characterized in that it contains chelate complexes of iron, vanadium, manganese, copper, cobalt, molybdenum, tungsten, ruthenium, rhodium, palladium or platinum or mixtures thereof. 8. Catalyst according to claims 1 to 6, characterized in that it contains chelate complexes of the elements of the 7th or 8th subgroup or mixtures thereof. 9. Catalyst according to claims 1 to 8, characterized in that it contains chelate complexes of oxyketones, ß-diketones, oxyacids, ketocarboxylic acids, dicarboxylic acids, in particular dicarboxylic acids and ß-diketones, or their acid esters with elements of the 7th or 8th subgroup or mixtures thereof. 10. Catalyst according to claims 1 to 9, characterized in that it contains one or more chelate complexes bound to an inert carrier. 11. Catalyst according to claim 10, characterized in that the carrier is activated carbon, AI2O3, S1O2, a zeolite or a polymeric resin. 12. Catalyst according to claim 11, characterized in that the carrier is activated carbon.