DE10230623A1 - Catalyst for oxidative degradation of (in)organic compounds in water, especially using hydrogen peroxide, contains a mixed-oxide, -hydroxide or - oxyhydrate of a sub-Group 7 and/or 8 element and sub-group 1 elements - Google Patents

Abstract

A catalyst for oxidizing (in)organic compounds in the aqueous phase contains (i) a mixed-oxide, -hydroxide or -oxyhydrate of a sub-Group 7 and/or 8 element; and (ii) sub-group 1 elements. An independent claim is also included for preparation of the catalyst by impregnating or solution precipitating mixed crystal compounds onto a carrier matrix, optionally followed by calcining.

Description

The invention relates to a catalyst for the Oxidation of organic and / or inorganic compounds that in water are included.

Many industrial production processes and Synthesis processes are in the aqueous phase carried out in the result of which is wastewater that is associated with initial, intermediate, By-products and end products are contaminated. More with organic Waste water contaminated with substances arise during the isolation and processing of the products. Alles this sewage and sludges have to, be cleaned before being released into the environment. The usual cleaning method is provided the sewage be discharged into the sewer (indirect discharge), biological cleaning in sewage plants. In many cases however contain the waste water Substances in wastewater treatment plants are not or only very slowly degradable, e.g. B. polycyclic aromatic Hydrocarbons (PAH) and adsorbable organic halogen compounds (AOX).

In addition, groundwater and leachate can be dissolved, biologically contain difficult or non-degradable organic ingredients, the because of their ecotoxic Potential must be eliminated.

Typical in sewage, groundwater and leachate or whitewash contained pollutants are polycyclic aromatic hydrocarbons, halogenated Hydrocarbons, mineral oil hydrocarbons, Cyanides, phenols, heavy metals, pesticides, polychlorinated biphenyls et al

Polycyclic aromatic hydrocarbons (PAH), adsorbable organic halogens (AOX), polychlorinated biphenyls (PCB), ethylenediaminetetraacetic acid (EDTA) and organic amines are particularly difficult to degrade pollutants represents.

From the prior art are one Series of wastewater treatment processes known, such as: adsorption processes, Precipitation / flocculation, Stripping, internal exchange, oxidative and reductive processes, microbiological Cleaning, membrane process, evaporation / drying.

In recent years, the oxidative Degradation of pollutants through chemical wet oxidation is becoming increasingly important won.

Methods are known in which the oxidative effect of the hydrogen peroxide and of the ozone can be increased by means of catalysts. Metal oxides and metal salts, preferably of transition elements (for example Fentons 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 41 18 626 ). The disadvantage here is the formation of large amounts of polluted metal sludge, eg. B. iron hydroxide sludge, which must be deposited or disposed of. Furthermore, an acidic pH range is required for the oxidation (Fentons reagent) catalyzed by iron (II) ions, which has a disadvantageous effect on the material resistance (corrosion) and fish toxicity.

Frequently there is a risk that the Catalysts through the often suspended particles contained in the wastewater are deactivated.

The known methods for wet oxidation are usually raised under Temperatures and pressures carried out, which leads to high investment and operating costs.

For processes that are in lower temperature (150-175 ° C) and pressure ranges (10-20 bar) must work in addition to In the presence of a catalyst, the pH is adjusted to 0.5-1.5 to allow the oxidation. Nevertheless, these processes do not completely oxidize the hydrocarbonaceous Pollutants to water and carbon dioxide reached.

Processes are also known in which the oxidation is carried out in the presence of full metal catalysts ( DE-OS 41 31 596 . DE-PS 195 03 865 ).

Oxidation on activated carbons is also described, the catalytic activity of the carbons being increased by using anodically oxidized carbon carriers which are subsequently doped with molybdenum VI and / or tungsten VI and / or vanadium V compounds. The salt compounds of the elements mentioned are used for doping 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 for the doping of activated carbon.

The known catalysts for catalytic wet oxidation have the disadvantage that they especially with high pollutant loads or difficult to degrade No complete pollutants Enable degradation of pollutants, the efficiency and service life of the catalysts are limited or their production is associated with considerable technical and cost expenditure is.

The invention is based on the object an easy to manufacture catalyst for the oxidation of organic and inorganic compounds in water places that are difficult to degrade even at high pollutant loads Compounds have a high degradation rate and under normal conditions (25 ° C, 1 atm) has a high effectiveness.

This object is achieved according to the invention solved a catalyst, of mixed oxides, hydroxides or oxyhydrates from the elements of 7th and / or 8th subgroup and elements of the 1st subgroup of the periodic table containing elements or their mixtures.

It has been found that mixed oxides, hydroxides or oxyhydrates from the elements of 7th and / or 8th Subgroup and elements of the 1st subgroup of the periodic table of the elements is highly effective for the oxidative degradation of have organic and inorganic compounds in water. Especially mixed oxides, hydroxides or oxyhydrates are suitable, the iron and / or manganese ions and copper and / or silver ions.

The compounds according to the invention have a Mixed crystal structure and contained in their layered lattice both metal ions of the elements of the 7th and / or 8th subgroup as also the elements of the 1st subgroup of the Periodic Table of the Elements. They are synthesized according to Hahn's rules or the rule of Kolthoff.

By incorporating metal ions the 1st subgroup of the periodic table of the elements in the crystal lattice the metal oxides, hydroxides and oxyhydrates of the elements of the 7th and / or 8th subgroup, compounds with a mixed crystal structure are formed, the surprisingly high catalytic activity for the Have oxidation of organic and inorganic compounds under normal conditions. You ensure the almost complete Degradation of pollutants that are difficult to decompose, such as polychlorinated Biphenyls (PCB), volatile halogenated hydrocarbons (LHKW), ethylenediaminetetraacetic acid (EDTA), organic amines, pesticides, adsorbable organic halogenated hydrocarbons (AOX) as well as other oxidizable compounds (COD). It was unpredictable that these Compounds have high catalytic activity even at neutral pH so that at Use of the catalysts according to the invention no additional Salting of the water takes place and the formation of sludge to be disposed of is eliminated.

The catalysts of the invention have compared to the in sewage contained metal compounds, inorganic salts and suspended matter high stability on. The activity the catalysts are not adversely affected by these substances. Thereby the catalysts have a high catalytic activity and long service life. Also the heavy metal ions known as catalyst poisons and sulfur compounds surprisingly inhibit the catalysts of the invention Not.

Particularly suitable as catalysts are the mixed crystal compounds from the oxides, hydroxides and Oxyhydrates of iron and / or manganese and the elements of the 1st Subgroup, preferably of copper and / or silver, and their Mixtures.

Particularly high degradation rates with organic and inorganic compounds, especially those that are difficult to degrade Compounds are created through the use of mixed oxyhydrates, mixed hydroxides and their mixtures achieved.

Mixed crystal compounds of the formulas (1) and (2) and mixtures thereof are preferred n _a A (OH) _{xn b} B (OH) _y (1), n _a A (OH) _x · n _b B (OOH) _y (2), used, where B is selected from the 7th and / or 8th subgroup, preferably represents manganese and iron, and A is selected from the 1st subgroup of the Periodic Table of the Elements, preferably represents copper and silver and n _a and n _b > 0 , x and y ≥ 1.

The mixed crystal compounds according to the invention preferably have a molar ratio of elements A: B in the compounds of formula (1) and (2) of 1: 100 to 1: 1.

Examples of suitable catalysts are: n _a copper (II) hydroxiden _b manganese (II) hydroxiden _c iron (III) hydroxide, n _a silver (I) oxiden _b manganese (II) hydroxiden _c iron ( II) hydroxide, n _a gold (III) hydroxide · n _b manganese (II) hydroxide · n _c iron (II) hydroxide, n _a copper (II) hydroxide · n _b manganese (II) hydroxide · n _c iron (III) oxyhydrate, n _a copper (II) hydroxiden _b manganese (II) hydroxiden _c iron (III) hydroxide, n _a silver (I) oxiden _b manganese (IV) oxiden _c iron (III) (II ) oxide, and their mixtures,
where n _a > 0, n _b and n _c ≥ 0 and n _b and n _{c are} not 0 at the same time.

The catalysts of the invention are as heterogeneous catalysts in fluid bed, fixed bed or fluidized bed processes used.

This ensures optimal use of activity of the catalysts and a high degradation rate of the pollutants.

The catalysts of the invention contain the mixed crystal compounds of mixed oxides, hydroxides or oxyhydrates and their mixtures bound on an inert carrier.

Activated carbon, polymeric resins, Al ₂ O ₃ , SiO ₂ and zeolites are used as carriers, the activated carbon being preferred because of the large BET surface area.

These supported catalysts are relatively easy to manufacture. The mixed crystal compounds are by impregnation or precipitation from a solution to the carrier matrix fixed.

The production of mixed crystal compounds takes place in a known manner by simultaneous hydroxide precipitation individual metal compounds in aqueous solution. The mixed oxide compounds can be produced by subsequent heat treatment (Calcination).

An advantage of the catalysts according to the invention is, that you Completely are recyclable.

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

The catalysts of the invention can oxidative cleaning of organic and / or inorganic compounds containing wastewater, process, Drinking water and groundwater can be used.

By the catalysts of the invention the organic and inorganic compounds become environmentally compatible Reaction products degraded. In most cases arise depending on the chemical composition of the oxidizable pollutants carbon dioxide, Water, chlorides, sulfates and other salts as well as some nitrogenous ones Compounds such as ammonium, nitrogen oxides and nitrogen. The danger the release of dangerous, toxic or non-biodegradable materials in the air, the There is no water or soil.

A particular advantage of the catalysts is that by their use the oxidative treatment of water with high degradation rates, short treatment times and relatively low use of oxidizing agents carried out can be. Moreover are slow-stable due to the relatively long service life of the catalyst Conditions guaranteed whereby the overall cost is low.

By the catalysts of the invention the oxidation of the pollutants is already at normal temperature, Normal pressure and a pH from 6 to 8 optimally catalyzed. The oxidation can also occur at higher or low pressures and temperatures as well as at pH values from 3 to 10.

Optimal degradation rates are at 20 ° C to 30 ° C, normal pressure and achieved in a pH range of 6.5 to 7.5.

It is advantageous that acidic output water the oxidation can be fed directly without prior pH adjustment can. After oxidation, these waters have a pH around 7, So that the In most cases, legally prescribed introductory conditions already exist without additional pH value setting fulfilled become.

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 degraded within a short time with the addition of hydrogen peroxide. Even very heavily contaminated wastewater with pollutant levels of 8-10 kg / m ³ COD can be effectively cleaned within 30–60 minutes, so that it can either be discharged into the receiving water or recycled as process water.

Treatment of the organically contaminated Water can take place in continuous or batch operation.

The excellent properties of the catalysts are also evident in the reaction rates, which are achieved in the treatment of water containing phenol. So it is done in the catalytic oxidation in the presence of hydrogen peroxide a practically complete degradation of the phenol after just 30 minutes, see above that the Phenol concentration well below that required by law Limit for the indirect introduction is.

With the catalysts of the invention can Degradation rates of 95% to 99% can be achieved. These catalysts allow the degradation of hard-to-break down organic and inorganic Pollutants, even in high concentrations in water and aqueous Suspensions can be included. The The pollutants are also degraded in cloudy water containing particles a very complex pollutant matrix. It can also contain organically bound heavy metals be prepared by these catalysts so that the existing ones Heavy metal ions are converted into defined oxidation levels and complex bound ligands are oxidatively destroyed. The free metal ions can subsequently be eliminated according to the state of the art.

It is also noteworthy that the catalysts of the invention the high degradation rates even with heavily fluctuating pollutant loads, as is usually the case with renovation projects.

The invention is based on the following of examples closer explained without the catalysts of the invention on these versions to restrict.

embodiments

example 1

Preparation of the catalyst

0.01 mol of silver nitrate, 0.3 mol of manganese (II) nitrate and 0.3 mol of Fe (II) nitrate are dissolved in 100 ml of water. 50 g of a SiO ₂ / Al ₂ O ₃ support material are stirred into this solution. After a residence time of 10 min, the suspension is adjusted to a pH of 10.5 with 10% sodium hydroxide solution with continuous stirring. Then the particulate phase is separated and three times with dist. Washed water. The catalyst is then dried.

Use of the catalyst according to the invention

20 g of the catalyst produced turns brown in 1 liter colored, dull given wastewater smelling of benzoid compounds (pH = 8).

At temperatures of 25 ° C 2.2 ml of hydrogen peroxide (30%) added. After 30 minutes,> 95% of the organic Contaminants oxidized. The treated water was clear, color and odorless.

After the treatment, it was cleaned Separated waste water and the catalyst again with the same waste water treated. Similar results were obtained after the same treatment time achieved as with the first treatment, which is consistent high catalyst activity and service life.

The table below shows the Pollutant values of the untreated and treated water taken become.

Example 2

50 kg one with copper (II) hydroxide · manganese (II) hydroxide · iron (III) oxyhydrate doped activated carbon is used for used to clean contaminated groundwater. The Groundwater is subjected to pre-filtration.

The pre-cleaned water becomes continuous mixed with hydrogen peroxide and then in the fluidized bed reactor initiated, which was infested with the catalyst material.

The hydrogen peroxide is metered volume-controlled in an amount of 2.4 l / m ³ groundwater.

The oxidation takes place at normal temperature and under normal pressure.

The pollutant values were measured during the Treatment recorded. The table below shows the Values for the untreated and treated water can be removed.

Claims (15)

Catalyst for the oxidation of organic and inorganic compounds in the aqueous phase, characterized in that it contains mixed oxides, hydroxides or oxyhydrates from the elements of the 7th and / or 8th subgroup and elements of the 1st subgroup of the Periodic Table of the Elements or their mixtures contains. Catalyst according to claim 1, characterized in that it contains mixed oxyhydrates or mixed hydroxides or mixtures thereof. Catalyst according to the claims 1 and 2, characterized in that it mixed oxides, hydroxides and oxyhydrates of iron and / or manganese and elements of the 1st Subgroup, preferably copper and silver, or mixtures thereof. Catalyst according to the claims 1 to 3, characterized in that it mixed oxides and hydroxides of Copper and / or silver and elements of the 7th and / or 8th subgroup or contains mixtures thereof. Catalyst according to the claims 1 to 3, characterized in that the mixed oxides, hydroxides and oxyhydrates iron and / or manganese ions and copper and / or Contain silver ions. Catalyst according to claims 1 to 5, characterized in that it contains mixed crystal compounds of the formula (1) and / or of the formula (2) and mixtures thereof n _a A (OH) _{xn b} B (OH) _y (1), n _a A (OH) _x · n _b B (OOH) _y (2), contains, where B is selected from the 7th and / or 8th subgroup, preferably represents manganese and iron, and A is selected from the 1st subgroup of the Periodic Table of the Elements, preferably represents copper and silver and n _a and n _b > 0 , x and y ≥ 1. Catalyst according to claim 6, characterized in that the molar ratio of the Elements A and B in the compounds of formula (1) and (2) 1: 100 up to 1: 1. Catalyst according to the claims 1 to 7, characterized in that it contains one or more mixed oxides, hydroxides or oxyhydrates whose mixtures bound on an inert carrier contains. Catalyst claim 8, characterized in that the carrier is activated carbon, Al ₂ O ₃ , SiO ₂ , a zeolite or a polymeric resin. Catalyst according to claim 9, characterized in that the carrier is activated carbon is. A process for the preparation of the supported catalyst according to claims 1 to 10, characterized in that the mixed crystal compounds are applied to the support matrix by impregnation or precipitation from a solution and then optionally subjected to a heat treatment (calcination) be. Use of the catalyst according to claims 1 to 11 for oxidative Degradation of organic and inorganic compounds in water in Presence of one or more oxidizing agents. Use of the catalyst according to claim 12 for wet oxidation from in water contained organic and / or inorganic compounds in the presence of hydrogen peroxide. Use of the catalyst according to claims 12 and 13 for oxidative Purification of organic and / or inorganic compounds containing Wastewater, process, Drinking and groundwater. Process for the oxidative cleaning of organic and / or inorganic Compounds containing wastewater, process, drinking and groundwater characterized in that the oxidation in the presence of a catalyst according to claims 1 to 10 and an oxidizing agent is carried out.