NL7908288A - CATALYST FOR OZONE DESTRUCTION IN OZONE-CONTAINING AIR AND OZONE-CONTAINING GASES. - Google Patents

Description

N.O. 28.157 ’*

Catalyst for the destruction of ozone in air containing ozone and gases containing ozone

The invention relates to a catalyst for the destruction of ozone in air containing ozone and gases containing ozone.

Ozone is now successfully used in the most diverse areas as an oxidizing agent and disinfectant, and ozone-containing waste air or gas containing ozone is also always obtained. For example, when using ozone to clean and disinfect water in swimming pools, drinking water and other water that can be used in breweries, in the treatment of waste water, etc. Ozone-enriched air is frequently generated in hospital rooms in which ozone is used for disinfection and also in areas where high-pressure ultraviolet lamps and ultraviolet radiators are used.

As is known, ozone is a very toxic irritant gas and already in minimal amounts of about 0.5 ppm in the air can be harmful to health with a relatively long action. Sr causes irritation of the mucous membrane and disturbances of the central nervous system can also occur. It is therefore very important to develop suitable catalysts with which it is possible to destroy already small amounts of ozone in the air or in other gases.

Oxides of iron, lead, cobalt, nickel, copper or silver as catalysts for ozone destruction are already known from German patent specification 1,133,154. However, it has been found that the catalytic activity of these oxides with regard to the beneficial effect and the life span is only sufficient when high temperatures (80-120 ° C) are used. Since the waste gases generally have a temperature of 20 - 25 ° C, an increase in temperature is associated with higher costs, both for the equipment (corrosion-resistant materials) and for the energy. In German patent law "1,966,533, as catalysts for the ozone destruction, oxidic mixtures of nickel (II) oxide and ((III) oxide) are used, with or without doping of lithium oxide, of manganese (IV) oxide , copper (I) - and - (Il) oxide and silver oxide on a support, but also in these catalyst systems the catalytic activity is to convert ozone to the purity of the odor (<0,1 ppm). to destroy only above 50 ° G sufficient.

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Silver-manganese catalysts for the destruction of ozone in air have already been used (German "offenlegungsschrift" 2.537 * 090). These catalysts are also used, inter alia, at 20 ° C. At this temperature, however, the purification capacity 5 is low. Thus, at 20 ° C, an ozone content of 0.05 ppm is reached only at a volume rate of Ί 10,000 h. At higher volume rates, the degree of purification decreases at this temperature. * A good purification capacity at a volume rate greater than 10,000 h "is only achieved at temperatures above 50 ° C.

The invention relates to catalysts for the ozone destruction in air or in other gases which do not have these disadvantages.

The catalysts according to the invention are characterized in that they consist of a mixing system based on man-15, silver, aluminum and silicate, which is heated by heating a manganese compound, a silver salt, aluminum silicate and an alkali metal silicate at a temperature of 300 - 600 ° C is obtained in the presence of an organic compound which decomposes at the heating temperature.

Surprisingly, the catalysts according to the invention allow the ozone decomposition - in contrast to the known catalysts - to already have a high activity at 15 - 25 ° C.

By using the catalysts according to the invention it is possible to achieve excellent purification capacities also at 20 ° C with high volume velocities of the ozone-containing air of 11,000-18,000 h. The ozone content of the air can be up to 2% and can be reduced to less than 0.0½ ppm according to the invention.

The catalysts according to the invention contain silver and manganese in a weight ratio of 0.033: 1 to 2: 1. Already small amounts of silver cause a good effect, which can be further enhanced by increasing the silver content. Preferably, the weight ratio of the silver to the manganese should be 1 - 1.5: 1.

S1O2 should be present in the catalysts of the invention in a weight ratio to the manganese of 0.2: 1 to 0.3: 1 and the alumina in a weight ratio to the manganese of 0.02: 1 to 0.03: 1 to be.

In order to obtain the catalysts according to the invention 40, as manganese compounds, in particular Μηθθ or manganese salts 7908288 3 **, such as manganese citrate, are suitable.

As aluminum silicate, the aluminum silicate known by the name "Bentonit" from the company SÜd-Chemie AG in Munich with a ratio of the S102 to the Al2O4 of 3 * 5 -: 1 5 has proved suitable.

In particular, the silver salt can be silver nitrate.

As organic compounds, organic hydroxycarboxylic acids such as citric acid, other hydroxy compounds such as cellulose and also urea are preferably used. However, other organic compounds which decompose at a temperature of 300-600 ° C are also suitable. It has been found that the porosity of the catalysts is favorably influenced by the presence of the organic compounds. The organic compound is added in an amount of 70% by weight, based on the manganese.

It is also possible to add the organic compound in the form of a salt of the manganese with an organic acid such as citric, tartaric, gluconic and the like. In such a case, the weight ratio of the organic compound to the manganese is given by the salt in question and, for example, 20 manganese citrate is greater than 70% wt based on the manganese.

To obtain the catalyst, it is expedient to proceed in such a way that an amount of water is first added to the manganese compound, the aluminum silicate and the sodium metasilicate to form a paste. To this the concentrated solution of the silver salt is first added, after which the solid organic compound is added and mixed. Then, the obtained mass is spread thin, first dried at 110 ° C and then treated with slowly increasing the temperature in the range of 300-600 ° C for 3-5 hours. After cooling, the catalyst mass is brought into finely divided form and sieved. Preferably the sieve fraction of 1-3 πω * is used

However, it is also possible to process the catalyst mass (before or after drying or heat treatment) into tablets, pellets or pressed pieces in the form of strands according to known methods, or to use the catalyst as articles with a honeycomb structure.

A column is filled with the catalyst and the moist or dry, ozone-containing air of 15-25 ° C is passed through the column filled with the catalyst.

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Example I

100 g of finely powdered manganese dioxide (obtained from potassium permanganate and manganese sulfate according to Helvetica Chimica Acta, part 53 (1970) »453) were mixed with 10 g of aluminum silicate (Bentonit M, a product of Sud Chemie), 15 g sodium metasilicate (anhydrous) is mixed intensively with such an amount of distilled water that a porridge is stirred well. 16 g of silver nitrate (in the form of a saturated solution) were added to the mixture at 20 ° C and the mixture was stirred for about 5 minutes. Slowly - to avoid foaming or foaming - and with further stirring, 47 g of citric acid (42.97 g of citric acid) containing crystal water were added to the gruel. After further stirring for 10 minutes, the resulting mass was streaked in a layer thickness of 2-3 mui and then dried at 110 ° C. The dried material was thermally treated at 600 ° C for 4 hours, slowly increasing the temperature, finely divided after cooling, and then sieved.

The sieve fraction 1 - 5 ® ni was placed in the catalyst column.

Examples II-XI

Analogous to Example I, catalysts were prepared from the components listed in Table A in the amounts stated.

Table A

Catalyst- MnO- »Manganese- AgNO, Na2Si0 ~ Bentonit Ci- Cell Urea Sator Citrate 2 2 M (2) Tren- lu- according to ® (1), gggg Acid Loss Example H_0 ___2« S «« _ ii ioo - 5 .5 15 10 47 iii (3) ioo - 14.6 15 10 47 - - IV 200 - 29.32 50 20 94 v 100 - 31.5 15 10 47 VI 100 - 100.0 15 10 47 VII 100 - 157 .5 15 10 47 VIII 100 - 157.5 15 10 47 IX 126 - 24.0 22 14.4 - - 30 X 126 - 24.0 22 14.4 30 XI - 170.4 16.0 15 10 (1 ) Use of moist, water containing manganese citrate content: 170.4 g Mn ^ (CgH ^ 0 ^) 2 (2) Aluminum silicate from Sud-Chemie AG, Munich

(3) Heat treatment of the catalyst at 300 ° C (4 hours); all other catalysts: 4 hours at 600 ° C

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Examples of the application

At 20 ° C, the stream of ozone-containing air was passed through the catalyst column under atmospheric pressure at relative moisture contents of 80% and 90%, respectively (Run 8a, Table B).

After exhaustion of the catalyst, the catalyst could be regenerated at 300-600 ° C for 3-5 hours and reused.

The results are summarized in Table B.

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Claims (10)

Catalysts for the destruction of ozone in air or gases, characterized in that the catalysts consist of a mixing system based on manganese, silver, aluminum and silicate, which is heated by heating a manganese compound, a silver salt, aluminum silicate and an alkali metal metasilicate at a temperature of 300-600 ° C in the presence of an organic compound which is decomposed at the heating temperature. Catalyst according to claim 1, characterized in that the weight ratio of the silver to the manganese is from 0.035 to 1: 2: 1. Catalyst according to claims 1 and 2, characterized in that the weight ratio of the S1O2 to the handling is 0.2 1 to 0.3: 1. 4 ·. Catalyst according to claims 1-3, characterized in that the weight ratio of the aluminum oxide to the manganese is 0.02: 1 to 0.03: 1. Catalyst according to claims 1-4, characterized in that the manganese compound is MnO2 and / or a manganese salt, preferably manganese citrate Catalyst according to claims 1-5, characterized in that the silver salt is silver nitrate. Catalyst according to claims 1-6, characterized in that the organic compound is citric acid, cellulose or urea. Catalyst according to claims 1-7, characterized in that the organic compound is added in an amount of up to 70% by weight, based on the manganese. 30 Catalyst according to claims 1-7, characterized in that the organic compound is added in the form of a salt of manganese. 10. A process for the preparation of catalysts for the ozone destruction in air or gases, characterized in that the manganese compound, the aluminum silicate and the sodium metasilicate are mixed with water to form a paste, the concentrated silver salt solution and then the organic compound, the mass obtained dries and then treats at 300-600 ° C. ****** / 908288