DE2447552A1 - METHOD OF MANUFACTURING A CATALYST USED IN THE CATALYTIC OXIDATIVE DECOMPOSITION OF GASEOUS AMMONIA - Google Patents

Description

HENKEL, KERN, FEILER & HÄNZEL

BAVARIAN MORTGAGE AND

29 802 HNKL D CTMT ADF »5ΓΗΜΙΠ <! TBA <! SF ? EXCHANGE BANK MUNICH No. 318-85111

U3 iv sui ni ^ EDUAKÜ-ilCHMllJ-SIKAiSJl Z DRESDNER BANK MUNICH 3 914

TELEPHONE: (089) 66 3197, 663091 - 92 D-8000 MUNICH 90 POST CHECK: MUNICH 162147 -

TELEGRAMS: ELLIPSOID MUNICH

Ricoh Co., Ltd.

Tokyo, Japan ♦ · OCT. W \

Process for the production of a catalytic converter which can be used in the catalytic oxidative decomposition of gaseous ammonia

The invention relates to a method for producing a gas in the catalytic oxidative decomposition of gaseous Ammonia suitable catalyst, which is particularly suitable for the deodorization of copier devices with Ammonia development escaping exhaust gases and the like is suitable.

Ammonia copier for two-component diazotype materials are generally advantageous because in such copiers with high Copy speed and inexpensive, relatively quickly finished copies with high fade resistance up to one Can produce sheet size of AO and because such copiers are relatively easy to use. For these reasons, copiers using ammonia are used given preference over other copiers.

However, since copiers working with ammonia run the risk of environmental pollution by leaking

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of ammonia, more and more attention must be paid to avoiding environmental pollution in this regard will. For example, it has already been proposed that from copying devices working with ammonia to catalytically decompose escaping ammonia. There are already numerous publications regarding a oxidative decomposition of ammonia in a low temperature environment, in particular platinum metal catalysts for this purpose were used. However, when using such catalysts, the rate of ammonia conversion is slower at low temperature always less than 99.95%, so these catalysts do not do this suitable, the emission of ammonia from working with ammonia copiers under the legally prescribed To press maximum value.

The invention was based on the object of specifying a method for preparing a catalyst, by means of which in the oxidative ammonia decomposition in an atmosphere of low temperature, ie at a temperature of about 180 ° to 250 ⁰ C, an ammonia conversion efficiency of about 99.95% is achieved.

The invention thus relates to a method for production. a catalyst suitable for the catalytic oxidative decomposition of gaseous ammonia, which is characterized in that a catalyst consisting of a heat-resistant support with 0.3 to 2.0 wt Calcined at ^{0 C.}

The method according to the invention enables the production of catalysts that operate at temperatures in the range

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from 150 ° to 30O ⁰ C practically no N0 "can be formed and the ammonia contained in the exhaust gases of copiers operating with ammonia for two-component diazotype materials are able to almost completely decompose or reduce its concentration below a value that can practically still be smelled.

The accompanying drawing is a graph showing the relationship between the calcining temperature and the temperature for the ammonia gas decomposition reaction.

It has been considered that upon further heating of a catalyst prepared by a conventional method to a temperature between 500 ° is lowered to 1000 ⁰ C, its specific surface, whereby the catalytic activity of the catalyst undergoes degradation. Surprisingly, however, it has been found that such a catalyst has experienced a certain reduction in its specific surface area compared to an untreated catalyst, but that at the same time it is better in terms of its catalytic decomposition effect on gaseous ammonia in a low-temperature atmosphere has become. The reproducibility of this phenomenon was confirmed by the fact that identical specimens were repeatedly calcined and uniformly identical results were obtained. The reason for this phenomenon has not yet been fully clarified, but presumably the catalyst metal infiltrated into the fine pores of the support surface forms a coherent thin layer when calcined at a temperature within the specified range

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Surface layer, whereby the catalytically ^ activity improves and accelerates the reaction course is ₀ catalysts, the catalytic activity can be improved in the oxidative decomposition of gaseous ammonia respect by calcining at a temperature within the specified range, are those which, by applying 0 3 to 2.0% by weight of platinum metal (s) have been produced on a heat-resistant carrier. Platinum metal (s) are to be understood as meaning platinum itself, ruthenium, palladium, rhodium, iridium and / or osmium. According to the invention, catalysts which have been produced by combining the platinum metals mentioned with oxides of metals such as copper, iron, cobalt, chromium and the like are also suitable. Refractory carriers are silicon dioxide, aluminum trioxide, titanium dioxide and refractory masses of silicon dioxide and aluminum trioxide. As already mentioned, these supports carry 0.3 to 2.0% by weight of the platinum metal catalysts mentioned. The catalysts prepared in this way are then calcined according to the invention for a few hours at a suitable temperature. The calcination temperature differs widely depending on the kind of platinum metal, the kind of refractory support and the amount of platinum metal supported on the support. Conveniently, it is in the range of 500 ° to 1000 ⁰ C, preferably in the range of 600 ° to 800 ⁰ Co A two-hour calcination at a temperature of 500 ° to 1000 ⁰ C leads to catalysts which have a sufficient decomposition of gaseous ammonia to ensure fortune . As already mentioned, the attached drawing shows the relationship between the calcination temperature and the reaction temperature of the catalyst obtained in the calcination in the context of a catalytic oxidative ammonia gas decomposition,

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The calcination time in this case was always 1 hour. In the drawing, the reaction temperature means the temperature at a time when the ammonia gas concentration at an inlet concentration of 2000 ppm reached an outlet concentration of 1 ppm at a space velocity of 6000 hours. As can be seen from the drawing, in the case of a calcination temperature of less than 500 ^° C. or more than 1000 ^° C., the decomposition temperature for the ammonia gas reaches a value of over 250 ^° C., ie a catalyst calcined at a temperature outside the specified range is not suitable for the decomposition of gaseous ammonia in an atmosphere of low temperature (180 ° to 250 ⁰ C), as is intended according to the invention. Further, at a more than two hours, no further improvement calcination at a calcination temperature ranging from 500 ° to 1000 ⁰ C in the catalytic activity more, which katalytisehe activity falls rather even from. If the particular catalyst will no longer be calcined than 2 hours at a temperature in the range of 500 ° to 1000 ⁰ C, though its specific surface area decreases, but it gets an improved catalytic decomposition action of gaseous ammonia, can be practically even at a temperature of about 150 ° to 300 ⁰ C caused no nO and can, for example, from a working with ammonia copying apparatus escaping ammonia gas almost completely to eliminate and to press below the legally prescribed maximum value. When using a catalyst prepared according to the invention to remove the ammonia contained in exhaust gases from copying devices, the existing copying devices only need to be converted somewhat, with the ammonia to be deodorized

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Exhaust gas containing a catalyst (ammonia concentration: about 1000 to 5000 ppm) after separation from the cooling air for the high-voltage mercury arc lamp used for exposure is introduced into the catalyst bed containing a catalyst prepared according to the invention at a space velocity of less than 1800 hours. In this way, the gaseous ammonia almost completely decompose under a given reaction temperature of 150 ° to 300 ⁰ C and render them harmless.

The following examples are intended to illustrate the process according to the invention in more detail. In the examples, the measurement of the active catalyst surface was carried out with the aid of a commercially available measuring device for the specific surface and a silicone oil manometer operating with gaseous hydrogen. The residual ammonia content was determined by the neutralization method and the indophenol method (JIS K0099). The contents of NO, NO ₂ and N ₂ O were determined by the naphthylethylenediamine method (JIS K0104) and by gas chromatography.

example 1

An article prepared by coating of 0.5 wt .-? A platinum on -AIpO $ ^ commercial catalyst was std calcined in a muffle furnace for 1 hour at a temperature of 800 ⁰ C and then stored in a desiccator. If the catalyst calcined in this way was packed in a reaction tube and a gas containing 2000 ppm of ammonia was introduced into this reaction tube at a space velocity of 6000 hours, the residual ammonia content at the outlet after decomposition of the ammonia in a reaction

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tion temperature of 200 ⁰ C 1 ppm. If the reaction temperature was increased to 248 ° C., no more residual ammonia could be detected at the outlet.

If the catalyst mentioned at the beginning was used without calcination under the same reaction conditions at a reaction temperature of 2 ^ 8 ° C., the residual ammonia content was at the outlet 1 ppm. Furthermore, 1 ppm NO could also be detected.

Example 2

Commercially available ^ f-Al <£> ■? Granules were impregnated with a chloroplatinic acid solution to produce a 0.3% by weight platinum-bearing ^ -AlpO ^ catalyst. After drying and subsequent calcining for one hour at a temperature of 300 ^° C. in a stream of hydrogen, the catalyst obtained was left to lie in a desiccator. Part of the catalyst was removed from the desiccator and ^{calcined for a further hour at a temperature of 900 °} C. in air. Once calcined catalyst or twice calcined catalyst was packed in the described in Example 1 in a reaction tube, introduced containing gas into the reaction tube, a 3000 ppm ammonia, and carried out the ammonia decomposition at a reaction temperature of 210 ⁰ C, the residual ammonia content was in the once calcined catalyst at the reaction tube outlet 190 ppm. The NO content at the outlet was 0.5 ppm. NO2 and ^ O could not be detected. When the twice calcined catalyst was used, the residual ammonia content at the reactor tube outlet was 1 ppm. The NO content at the outlet was 0.5 ppm, NO ^ and NpO could not be detected.

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Example 3

A mixture consisting of 2 wt .-% platinumcarrying Jf-Al ₂ O, existing commercial catalyst was std calcined in a muffle furnace for 1 hour at a temperature of 750 ⁰ C and then dried in a desiccator. If the catalyst calcined in this way was packed into a reaction tube, 1800 ppm of gaseous ammonia

gas with a space velocity of 6000 hours and the decomposition of the ammonia was carried out at a reaction temperature of 223 ° C., the residual ammonia content at the outlet was 10 ppm. NO and N ₂ O could not be detected.

Of the aforementioned catalyst without calcining in the reaction tube was packed and carried out the decomposition of ammonia at a reaction temperature of 260 ⁰ C, the residual ammonia content was ppm on Reaktorrohrauslaß 10th The NO content was 5 ppm, the NO ₂ content was 1.0 ppm and the N ₂ O content was 0.3 ppm.

Example 4

A mixture consisting of 0.5 wt .-% Ru carrying ^ f-Al ₂ O, existing commercial catalyst was 1 h calcined in a stream of hydrogen at a temperature of 750 ⁰ C for and then are left in a desiccator. If the catalyst calcined in this way was packed into a reaction tube, a gas containing 3000 ppm of gaseous ammonia was introduced into the reaction tube at a space velocity of 9000 hours and the ammonia was decomposed at a reaction temperature of 185 ^° C.

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the content of residual ammonia at the outlet 1 ppm, of NO 5 ppm, of NOp 0.5 ppm and of NpO 0.3 ppm.

If the catalyst mentioned at the beginning was packed into the reaction tube without calcination and the ammonia was decomposed under the specified conditions, the content of residual ammonia at the reactor outlet was 15 ppm, the content of NO was 8 ppm and the content of NO _{2 was} 0.8 ppm . NoO could not be detected.

Example 5

A mixture consisting of 2 wt .-% platinumcarrying Jf-AIPO ^ existing commercial catalyst was calcined in a muffle furnace for 2 hours at a temperature of 700 ⁰ C and then allowed to lie in a desiccator. The thus calcined catalyst was packed into a reaction tube, introduced std into the reaction tube, a 2000 ppm gaseous ammonia-containing gas having a space velocity of 6000 and carried out the decomposition of ammonia at a reaction temperature of 220 ⁰ C, the residual ammonia content was ppm on Reaktorrohrauslaß. 1 NO and NOp could not be detected.

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Claims (3)

Claims φ A process for the production of a catalyst which can be used in the catalytic oxidative decomposition of gaseous ammonia, characterized in that a heat-resistant carrier consisting of a 0.3 to 2.0% by weight of platinum metal (s) is carried at a temperature of 500 ° calcined to 1000 ^{° C.} 2. The method according to claim 1, characterized in that the heat-resistant carrier is silicon dioxide, aluminum trioxide, Titanium dioxide and / or a refractory silicon dioxide / aluminum trioxide mass used. 3. The method according to claim 1, characterized in that calcining is not longer than 2 hours. 509819/0971