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Title:
METHOD FOR RECOVERING PRECIOUS METALS FROM WASTE CATALYST
Document Type and Number:
WIPO Patent Application WO/2010/084364
Kind Code:
A1
Abstract:
The method according to the invention consists recovery noble-metals by removing the layer containing catalytically active noble-metal from the surface of the substrate by means of selective powdering, and separating the fine powder enriched in noble-metals obtained this way by means of physical operation from the monolith substrate remained substantially in its original state or being less powdered during selective powdering than the component containing catalytically active noble-metal or separating the fine powder enriched in noble-metal obtained this way and/or the noble metal content remained in the waste catalyst after selective powdering, by means of chemical operation. The fraction enriched in noble-metals can be processed by any metallurgical or chemical processes known per se.

Inventors:
DOBOS GABOR (HU)
Application Number:
PCT/HU2010/000010
Publication Date:
July 29, 2010
Filing Date:
January 25, 2010
Export Citation:
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Assignee:
DOBOS GABOR (HU)
International Classes:
C22B7/00; C22B11/02
Domestic Patent References:
WO2005035804A12005-04-21
Foreign References:
EP0648848A11995-04-19
JPH05212297A1993-08-24
US20040156764A12004-08-12
US20060084572A12006-04-20
US3985854A1976-10-12
US5328669A1994-07-12
CA2520275A12006-03-21
US5160711A1992-11-03
Other References:
GMELIN: "Handbook.", vol. AL, pages: 174 - 196
M. SHELEF; R. W. MCCABE: "Twenty-five years after introduction of automotive catalysts: what next?", CATALYSIS TODAY, vol. 62, 2000, pages 35 - 45
A. SERPE ET AL., COORDINATION CHEMISTRY REVIEWS, vol. 252, 2008, pages 1200 - 1212
RONALD M. HECK; ROBERT J. FARRAUTO; SURESH T. GULATI: "Catalytic Air Pollution Control: Commercial Technology", 2009, JOHN WILEY & SONS, pages: 176,183
YU. A. VOLCHENKO; V. A. KOROTEEV, THE URALS PLATINUM POLYGON - NEW DATA INSTITUTE OF GEOLOGY AND GEOCHEMISTRY
"Leipzig", 1987, VEB FACHBUCHVERLAG, article "Wissensspeicher Ultraschalltechnik", pages: 365
SUSLICK, K. S.; DIDENKO, Y.; FANG, M. M.; HYEON, T.; KOLBECK, K. J.; MCNAMARA, W. B. III; MDLELENI, M. M.; WONG, M.: "Acoustic Cavitation and Its Chemical Consequences", PHIL. TRANS. ROY. SOC. A, vol. 357, 1999, pages 335 - 353
V. AVRAMESCU; G ORASANU ET AL.: "Technologies and Equipments for Complex Surfaces Nanofinishing by Abrasive Flowing", ANNALS OF THE ORADEA UNIVERSITY, FASCICLE OF MANAGEMENT AND TECHNOLOGICAL ENGINEERING, vol. VII, no. XVII, 2008
Attorney, Agent or Firm:
DANUBIA PATENT & LAW OFFICE LLC (Budapest, HU)
Download PDF:
Claims:
Claims

1. Method for recovery noble-metal from e waste supported catalyst containing catalytically active noble-metal, characterized by removing the layer containing catalytically active noble-metal from the surface of the substrate by means of selective powdering.

2. Method according to claim 1, characterized by separating the fine powder enriched in noble-metal obtained this way by means of physical operation from the monolith substrate remained substantially in its original state or being less powdered during selective powdering than the component containing catalytically active noble-metal. 3. Method according to claim 1 , characterized by separating the fine powder enriched in noble-metal obtained this way and/or the noble metal content remained in the waste catalyst after selective powdering, by means of chemical operation.

4. Method according to claim 1 , characterized by achieving said selective powdering in such a way that the grain size of the active material removed from the surface of the monolith is smaller by at least 1-2 orders than the grain size of the monolith substrate.

5. Method according to claims 1 , characterized by achieving said selective powdering in such a way that the catalyst is dipped into a liquid, cavitation is produced by ultrasound energy and the catalytically active material containing noble-metal is removed from the surface of the monolith substrate by means of said cavitation. 6. Method according to claim 5, characterized by producing cavitation by alternating ultrasonic frequencies within the range of 10 - 1000 KHz and/or by scanning frequencies within one or more narrower frequency ranges within said range.

7. Method according to claims 5 or 6, characterized by crushing the catalyst before the ultrasonic treatment to a grain size wherein the passages of the monolith substrate are open.

8. Method according to claim 7, characterized by crushing the catalyst to a grain size of at most 3 mm.

9. Method according to claims 5 to 8, characterized by mixing the liquid to prevent the granules from settling, while applying ultra sound. 10. Method according to claim 1, characterized in that selective powdering consists of abrasive flow machining.

11. Method according to claim 1, characterized in that selective powdering consists of immersing the catalyst into a suspension of abrasive grains and to impart oscillations to the catalyst parallel to the passages of the monolith by a frequency between 5 and 500 Hz. 12. Method according to claim 1 , characterized in that selective powdering consists of grit blasting achieved by blowing airborne adhesive grains through the passages of the catalyst.

13. Method according to claim 12, characterized by achieving grit blasting by means of grit particles being greater than 50 microns in grain size. 14. Method according to claims 1-13, characterized by processing the fraction enriched in noble-metals by means of metallurgical or chemical processes known per se.

Description:
METHOD FOR RECOVERYNOBLE-METAL FROM WASTE CATALYSTS

The present invention relates to a method for recovery noble-metal from waste catalysts. The invention is applicable in relation to all catalysts containing noble-metals, which are provided with a catalytically active layer containing a noble-metal agent (washcoat) and deposited on a compact monolith substrate having low-porosity and providing mechanical stability.

Supported catalysts mentioned above are widely used in chemical industry (Gmelin Handbook. Pt Suppl. Vol. Al p 174-196). A significant amount of platinum group metals has been used from eighties for producing automotive catalysts decreasing the proportion of deleterious substances in exhaust gases (M. Shelef, R. W. McCabe: Twenty-five years after introduction of automotive catalysts: what next? Catalysis Today 62 (2000) 35-45). Laws recently in force in the industrial countries are fixing limit values of pollution that can hardly be accomplished without catalysts. Since the lifetime of catalysts is expected to be between 3 and 5 years, recovery of noble-metal content of used catalysts, along with catalysts production, has become a separate industrial field of late 30 years. However, only 20 % of the waste catalysts is processed to obtain PGMs (Platinum Group Metals) as yet (A. Serpe et al., Coordination Chemistry Reviews 252 (2008) 1200-1212). Hence a significant development is envisaged in this field in the near future both for economical and waste disposal service reasons. Since used catalysts are harmful wastes their collection should be enforced by environmental authorities sooner or later.

At the very beginning it had been used pyrometallurgical processes comprising grinding the whole catalyst then fluxed with a collector metal (Cu, Fe or Pb) and a flux forming a low viscosity and low melting point slag with metal oxides of the monolith substrate. Thus the platinum group metals enrich in the collector metal worked further by hydrometallurgical way by acidic dissolution of collector metal (Gmelin Handbook. Pt Suppl. Vol. Al p 8). Since the noble-metal content of the catalyst is generally no more than a few tenth percents, and much more additives (collector metal and flux) are also needed, it must be smelted a mass of many thousand times more than that of the noble -metal yielded. Thus this is a very energy-consuming process. Further processing of the collector metal also has a significant reagent demand.

About these shortcomings recent developments for recovering catalyst wastes use hydrometallurgical methods in most cases. But these methods also suffer from several disadvantages:

The chemically inert noble-metal content of the catalyst can be dissolved only by means of largely aggressive, highly oxidative chemical agents, like aqua regia (i.e.: WO 2005/035804 Al), C1/C12 and/or Br2, 12,NaC103, etc. (i.e.: US 3,985,854). In addition, dissolution reaction in most cases takes place by a sufficient reaction rate only at high temperature and at high pressure (i.e.: US 5,328,669). Since the catalytically inactive monolith ceramic substrate forms the main portion of mass of the catalyst, "smearing" thereof with aggressive chemical agents necessary to dissolve noble-metal content is inevitable. This results in increased consumption of chemical agents and water and causes significant waste forming.

Consequently, it would be very useful to enrich the noble-metal content of the catalyst by means of physical processes, without using chemical agents, if possible. In case of inevitable applying of chemicals the aim of the procedure is to extenuate the aggressive nature of reactions as well as decreasing of the excess of reagents. Canadian Patent document CA 2520275 Al teaches a method comprising preparation of barrows remained after recovery platinum metals from ores by mechanical enrichment to subsequent chemical processing. The base material according to CA invention is a finely ground powder to be processed by flotation known itself in the art. Other materials have to be ground to apply according to the invention. The core of the inventive perception is that it is to be analysed whether which fraction of granules or of density of the material ground in its whole mass does contain the largest amount of useful materials (PGM: platinum group metals). Having these data the enrichment process has to be achieved with the whole ground mass by means of physical methods based on differences of density or grain size, and this is a fundamental drawback. During processing the rubbish material is to be cleared off instead of components containing platinum metals.

There is a further difficulty, namely that the monolith substrate used for producing catalysts for cars has a typical porosity of about 24 - 35 %. For the time being, 95 % of these catalysts is produced by Corning Glass Works (Ronald M. Heck, Robert J. Farrauto, Suresh T. Gulati: Catalytic Air Pollution Control: Commercial Technology, 2009. John Wiley & Sons, pp. 176. and 183). Accordingly, a part of the PGM necessarily enters in the pores of the monolith. Therefor, the car catalysts may contain about 5 - 20 % of the whole PGM content (which generally means about 200 ppm) after removal of the active layer thereof. A material containing such an amount of PGM is deemed as PGM ore (Yu. A. Volchenko and V. A. Koroteev: The Urals Platinum Polygon - New Data Institute of Geology and Geochemistry of UB RAS 620151 Ekaterinburg, per. Pochtovy, 7, Russia) and, accordingly, it is worth to deal with extraction of it .

It is an object of the present invention to avoid the increased chemical agents and water consumption of the catalyst recovery process as described above. A further object of the invention is to reduce waste forming during processing, and to simplify elimination thereof. Above objects are accomplished by the method according to claim 1.

The pivot of the present invention is that the mechanical separation does not take place by the whole mass of base material ground, but the means of separation is the way of grinding itself. Consequently, the aim of the invention is just grinding and subsequent selective recovery and mechanical separation of wash coat containing noble-metal/s. Therefore, the base material is not in a ground state in its whole mass even at the end of the process, that largely simplifies said mechanical separation.

Applying the method according to the present invention enables to "soften" the conditions of the chemical operation which may be needed in some cases, which means applying less aggressive reagents, decreasing the amount of the excess reagents, avoiding the use of autoclaves and fine (typically below 20 microns) grinding of the material as well, as reducing the reaction time and improving the noble metal gain.

Solution of the problem becomes possible by the find of possibility of separation of monolith ceramic substrate and the porous agent containing active noble-metal material. This separation is possible because the mechanical stability of the monolith substrate is substantially higher than that of the active material deposited afterwards thereon. The reason of this is that a great specific surface providing high catalytic activity in the one hand and high mechanical stability in the other hand are incompatible requirements. This contradiction is solved by the conception of "supported catalyst" providing catalytic activity by means of two different structural elements: a mechanical monolith substrate and an active material deposited afterwards thereon each having dissimilar mechanical properties. Thus the properties of both said structural elements might be optimized according to requirements supported by their own functions. Consequently the supported catalyst is an immanently heterogeneous material due to its mechanical properties. This way it can be achieved at least largely a selective grinding of a catalytically active layer containing noble-metal and having generally looser structure, while in fact the compact and mechanically firmer monolith substrate remains intact. Then the fine powder thus obtained enriched in noble-metals can easily be separated by known processes from the coarsely ground monolith being in its original state or at most a little bit powdered.

Separation thus obtained is considerable, though its contrast, that is the extent of selectivity, depends on the range of the difference of mechanical strength of the components, which is immanently significant.

Since the mass of the catalytically inactive monolith substrate is usually 10-100 times greater than that of the catalytically active, noble-metal containing material deposited afterwards thereon, mechanical separation according to the invention, that is the selective powdering or grinding, can constitute an enrichment even in the range of 10- 100 times, as regards the noble-metals. At the same time water, chemical agent and energy demands of any further processing will be decreased in the same proportion, and the amount of wastes contaminated by aggressive chemical agents used for processing is also reduced.

After mechanical separation described above the noble-metal can be yielded from the significantly enriched concentrate by means of hydro-metallurgical or pyro- metallurgical processes known per se.

For the method according to the invention the component containing catalytically active noble-metal is removed from the surface of the substrate of the catalyst by selective powdering, then the fine powder enriched in noble-metals obtained this way will be separated by means of physical operation known in the art from the coarsely ground or less powdered monolith substrate than the component containing catalytically active noble-metal, and remaining substantially in its original state during selective powdering.

Selective powdering can be achieved manually either by means of a knife, scalpel or a sharp tool scraping the active material containing noble-metal from the monolith substrate, without getting the monolith damaged substantially. Although this embodiment of the method according to the invention has no industrial importance, it demonstrate well the inventive concept.

Implementing of selective powdering may be achieved in many different ways.

Using ultra sound through a fluid is one of such possibilities. It is known, that ultrasonic washers are widely applied in different industrial fields to clean and degrease complex shaped work pieces, i.e. having bind holes, and remove powder like dirt as machining- grinding deposits (see: Wissensspeicher Ultraschalltechnik. VEB Fachbuchverlag Leipzig 1987 p 365). Required cleaning effect is due to acoustic cavitation created by ultrasonic oscillations in the fluid. When a piece of supported catalyst is placed in an ultrasonic washer, the catalytically active material will be removed from the surface thereof as it can be seen well also by eye and it disperses in the liquid as a fine powder, while the monolith substrate remains undamaged.

Consequently, in an advantageous embodiment of the mechanical separation according to the present invention the catalyst should be dipped into a liquid and the selective powdering, that removes catalytically active material containing noble-metal from the surface of the monolith substrate, is accomplished by means of cavitation created by ultra-sound energy imparted to the liquid.

Active material will be removed from the surface of the monolith after a treatment of only a few minutes as it can be seen well also by eyes. Much more time is needed to achieve the same result in the holes of the monolith. In a given case, results can be achieved by choosing an adequate frequency or rather by the continuous scanning of frequency range.

In a preferred embodiment according to the invention the selective powdering is achieved by altering ultrasonic frequencies within in a range of 10 and 1000 KHz and/or by scanning frequencies within one or more narrower frequency ranges within above range.

Our aim might easily be achieved by crushing the catalyst. In order to achieve a sufficient result the catalyst need not be ground or even not expedient to be ground as fine powder. It is sufficient to crush the catalyst by means of a coarse breaker, i.e. a jaw crusher as its grain size makes free the channels of the monolith substrate before ultrasonic treatment. This substantially means a maximal grain size of 2-3 mm. The catalyst crushed by such a grain size should be fed directly in the liquid placed in the vessel of an ultrasonic apparatus and mixing the liquid at an intensity sufficient to prevent the biggest granules from settling, while applying ultra sound. This technique imparts a very intensive mechanical effect, since the granules of the catalyst, during a continuous displacement, go round frequently the most intensive places of the ultra sound space. Other possibility to achieve the method according to the invention is to accomplish selective powdering by means of abrasive flow machining process (M. Alitavoli, M. Mehran: An experimental approach to Abrasive Flow Machining (AFM) process, TICME2005 December 121-15, Tehran, Iran). According to this solution the supported catalyst should be placed in a working chamber as a whole, placing the holes or passages of the monolith substrate in a current in opposite direction of a liquid containing abrasive grains. The liquid flows back and forth alternately, while abrasive grains dispersed in the liquid, which is preferably water, polish slightly the internal surface of the passages of catalyst and the catalytically active porous layer tends to be attrited soon. Instead of using abrasive flow machining process requiring a technically complex device, it is also a good solution to achieve the selective powdering to impart oscillations to the catalyst ion a direction parallel to the passages of the monolith by a frequency between 5 and 500 kHz and immersing it into a suspension of abrasive grains, rather than flowing the liquid back and forth. Because of tixotropy of the suspension the grains fluidized in the area of oscillating catalyst enter the passages in the catalyst and, rubbing against internal surface of the passages, remove the active material containing platinum metals.

Instead of a liquid, energy required to remove active material of the catalyst from the monolith substrate may also be delivered by a gaseous medium. In this case selective powdering, that is removing active material from the monolith substrate, is achieved by grit blasting, blowing airborne adhesive grains through the passages of the catalyst. With this, the energy of impact/friction removes microscopic particles from the surface of the target.

A common feature of technical solutions described above is that the grain size of the active material removed from the surface of the monolith is smaller by at least 1-2 orders than grain size of the main mass portion of at most coarsely ground monolith. Thus the two fractions can easily be separated according to their grain sizes by means of known methods, i.e. wet screening, washing or sedimentation. Such a separation will not be disturbed by abrasive grains used, if the lest grain size thereof is bigger than 50-

100 microns.

Using the simple method according to the invention the possible enrichment of noble- metals could go up to tenfold in a single step, while using no chemicals but water only (or even without water in some cases). Monolith substrate separated this way is

"smeared" at most by water only, while all environmentally harmful catalytically active layer removed.

The separated fraction enriched in noble-metals obtained by methods used can be further processed by means of known metallurgical and/or chemical .methods. The very fine grain size of materials obtained by the mechanical method according to the invention facilitates said further processing, thus these materials might be further processed directly, without grinding.

The monolith may contain noble metal after removal of the active layer thereof, depending of the porosity and the magnitude of the active surface thereof. During the experiments it was found that dissolving the noble metal content was unexpectedly easy following said physical separation. This may be the result of the fact that the closed pores of the monolith opened by the removal of the active layer, and the chemicals can reach the noble metal remained in the pores more easily. It is known e.g. that noble metals can be solved by alkali cyanides. Solving the noble metal content of catalysts, however, should be carried out under overpressure, above a temperature of 100 0 C (preferably at about 160 0 C) in autoclaves, in order to achieve satisfactory speed (see e.g. US 5,160,711). Contrary to that, a great part of the PGM content may be extracted from the monolith by short boiling after removal of the active layer by ultrasound, according to the present invention. If ultrasound is applied during the extraction, the speed of the reaction is satisfactory even at about 70 0 C temperature.

Due to the above, according to one preferred variant of the method according to the present invention for recovery noble-metal from waste supported catalyst containing catalytically active noble-metal is carried out by removing the layer containing catalytically active noble-metal from the surface of the substrate by means of selective powdering, as outlined above, wherein the pores of the monolith are opened, and thereafter the remaining noble metal is solved from the pores by any known chemical agent, preferably without transferring the monolith and - in some cases - the concentrate from the container to another one. Further acceleration of the process may be achieved by applying ultrasound, as it is known (Suslick, K. S.; Didenko, Y.; Fang, M. M.;

Hyeon, T.; Kolbeck, K. J.; McNamara, W. B. Ill; Mdleleni, M. M.; Wong, M. (1999): Acoustic Cavitation and Its Chemical Consequences, in: Phil. Trans. Roy. Soc. A, 1999, 357, 335-353.). Thereafter, the remaining chemical agent is neutralized or inactivated or washed, if needed. The monolith and/or concentrate containing practically no noble metal can be used for building or other purposes.

The method according to the invention will be explained more in details through the following examples:

Example 1 Automotive catalyst waste was crushed by a jaw breaker to a maximal grain size of 3 mm. 100 g of crushed substance was fed into the vessel of an ultrasonic washer, and then 500 ml water added. A blade mixer with variable rotational speed immersed into the vessel and its speed was chosen to create a flow being able to entrain also the biggest solid particles. This could easily be controlled by eyes, since water did not become cloudy because of the coarse particles. Then the ultrasonic generator providing oscillations of 42 kHz with 50 W ultrasonic power was turned on. After 1 minute the liquid became milky and perfectly opaque after 8 minutes. Sampling the liquid time by time, developing of the process was controlled by visual inspection of surface of the bigger particles. After 180 minutes the visual inspection showed that the active material was completely removed from the surface of the monolith particles. The apparatus was turned off and suspension obtained this way was poured onto a 80 micron meshed screen, and fine particles were washed by water. Riddlings was then dried and weighed. Its weight was 92,4 g. Examining particles by a microscope, no traces of the active material of the catalyst was found The platinum content of the material dropped from the initial 2150 ppm to 450 ppm, which was 20,9% of the original value. Accordingly, this was the platinum content in the pores of the monolith, meanwhile 79,1 % was in the concentrate.

Example 2

The test according to Example 1 was repeated with another material and another ultrasound device. The PGM content of the catalyst was as follows: Pt = 290 ppm and Pd = 2140 ppm. The ultrasonic washer of 5 liters operated at 28 kHz, with an output of 100 W ultrasound power. 100 g catalyst sample crushed to a grain size up to 3 mm was applied and 4 liters of water was added. The mixture was stirred with propeller mixer to prevent the granules from settling. After 5 hours the device was switched off. The suspension received was poured to a filter of 80 microns grain size and the fine grains were washed out with water. The deposit remained on the filter was dried and measured. The weight of the deposit was 71,9 g. Examining particles by a microscope, no traces of the active material of the catalyst was found. However, the grain size was clearly smaller, than it was originally, as the frequency of the ultrasound applied was lower. The platinum content decreased from the initial 290 ppm to 40 ppm, which was 13,8 % of the original value. The palladium content decreased from the initial 2140 ppm to 320 ppm, which was 15 % of the original value. This was, consequently, the residual PGM content in the monolith. This result can be appraised in view of the fact that earlier, the same platinum yield was achieved from car catalysts with cyanide leaching in autoclave, at a temperature of 160 0 C, in three subsequent leaching steps. In the test according to this Example, the same result was obtained, without applying chemicals. Example 3

15 g from the monolith without active layer, obtained during the test of Example 2. was added to an Erlenmeyer flask of 600 ml. 100 ml water and 1 ml of 20% hydrazine hydrate solution were added, too. A glass funnel was set in the mouth of the flask (in order to ensure some reflux) and the liquid was lightly boiled for 15 minutes. Than, the liquid was decanted from the excellently settled grains. (The liquid could be used later for the treatment of another charge, upon setting again the hydrazine content.) 100 ml water, 3 g solid NaOH and the same amount of KCN was added to the monolith grains remained in the flask, and the liquid was lightly boiled for 60 minutes, as above. The liquid was left to cool to hand- warm and was decanted from the quickly settled fine grains. (The liquid could be used later for the treatment of another charge, upon setting again the hydrazine content.) The deposit was washed and decanted with 3 x 50 ml water and dried at 120 0 C. (The wash water could be used for replacing evaporation and drying losses.) The remaining cyanide content of the solution used for wetting the PGM free material can be disposed e.g. by oxidation in aqueous solution, or harmless products can be obtained if the treated and dried material is heated in air to 600 - 800 0 C. Atomic absorption analysis proved that the platinum content of the material decreased below the detection limit (if the measurement was the same as the one used for the initial concentration), and the palladium content decreased to 50 ppm, which was 2,3 % of the original value. This shows that 97,7 % of the platinum content of the basic material can be extracted at a temperature of 100 0 C, during 1 hour.

Example 4

15 g from the monolith without active layer, obtained during the test of Example 2. was added to the ultrasonic device according to Example 2. 4 1 of water was added and heated to 70 0 C. 16 g NaOH and 40 g KCN was added, ultrasound was applied and the liquid was stirred for 4 hours. Then, the device was switched off, the liquid was decanted, the monolith was washed, collected on filter paper and dried at a temperature of 120 0 C. Atomic absorption analysis proved that the platinum content of the material decreased below the detection limit (if the measurement was the same as the one used for the initial concentration), and the palladium content decreased to 40 ppm, which was 1,9 % of the original value. This shows that 98,1 % of the platinum content of the basic material could be extracted at a temperature of 70 0 C, during 4 hour, upon prior physical enrichment and combined chemical and ultrasonic treatment. Example 5

The PGM content of the catalyst was as follows: Pt = 290 ppm and Pd = 2140 ppm. 100 g catalyst sample crushed to a grain size up to 3 mm and 4 liters of water was added to the ultrasonic device according to Example 2. The mixture was stirred with propeller mixer to prevent the granules from settling. The liquid was heated to 70 0 C, 16 g solid NaOH and 40 g KCN was added and the mixture was stirred for 4 hours, without applying ultrasound. Then, the device was switched off and the slurry was washed to a 5 1 delivery flask. It was filled until sign and the liquid was homogenized. Upon several hours of settling, the Pt and Pd concentration of the clear liquid was measured by atomic absorption analysis. The Pt content was 2,69 mg/1, the Pd content was 20,67 mg/1, which means 46,3 % and 48,3 % yield, respectively.

Example 6

The catalyst material in this example was the same as in Example 5. The material was added to the ultrasonic device according to Example 2. 4 1 of water was added and the mixture was stirred with propeller mixer to prevent the granules from settling. Ultrasound was switched on and applied for 4 hours. Samples taken from the settled grains showed under microscope that the washcoat was removed from the surface of the monolith grains. Thereafter, the cloudy liquid was stirred again, without applying ultrasound. Upon heating the liquid up to 70 0 C, 16 g solid NaOH and 40 g KCN was added and the mixture was stirred for 4 hours, without applying ultrasound. Then, the device was switched off and samples were prepared for chemical analysis, as in Example 5. The results were as follows: Pt = 5,48 mg/1, Pd = 40,83 mg/1, which means 94,5 % and 95,4% yield, respectively. As there was no ultrasound applied during the chemical reaction, considerable improvement of the yield results is not due to the already mentioned "sono-chemical" activation, but to the preceding selective powdering and opening the pores according to the invention. Furthermore, there was no need of transferring the monolith or the washcoat to another device. Example 7

A miniature and simplified apparatus was built for the purpose of our abrasive circulation tests on the base of a literary source (V. Avramescu, G Orasanu et al.: Technologies and Equipments for Complex Surfaces Nanofmishing by Abrasive Flowing..., Annals of the Oradea University, Fascicle of Management and Technological Engineering, Vol. VII (XVII), 2008.) A prism of 1x1 cm in size cut out of an automotive catalyst just held the working chamber of the apparatus and it placed there in such a way that the suspension containing abrasive grains could flow through its passages parallel to its longitudinal axis. Water was used as suspending medium and silicon carbide particles of 50-150 micron in grain size were used as abrasive grains. 30 cycle/minute were accomplished. The pressure in pneumatic cylinders was 6 bar. It has been found that the active material was completely removed from the inner walls of the passages in the catalyst after 2 hours, while the monolith substrate did show a minor change only, except that the front edges wore a bit.

Example 8 A single monolith unit of a catalyst removed from the exhaust box of a car was mounted as a whole (without crushing) on an end of a rod oscillated with variable amplitude by means of an eccentric disk in the direction of its longitudinal axis in a frequency range of 5-500 Hz, so that the direction of the oscillation was parallel to the honeycomb structured passages in the monolith. Silicon carbide abrasive powder of 100-200 micron grain size was placed in a vessel having adequate sizes and added water in a quantity just to dip the powder after getting wet completely. Turning on the vibrator the monolith oscillating along with the rod was immersed into that suspension of abrasive grains. Because of the oscillation the abrasive grains adjacent the monolith came into fluid state and entered also the honeycomb structured passages in the monolith. Abrasive grains attrited catalytically active material also from the inner passages of the monolith after a period depending on the frequency and amplitude of the oscillation, and the clean monolith remained. The latter was rinsed with water, dried, then its inner passages was examined by microscope, after some "dissecting". Active material was not found even in traces.

Example 9

A prism of 1x1 cm in size was cut out of the catalyst of a car such as the passages of the monolith were parallel of the longitudinal axis of the prism, so that they were perpendicular to its 1x1 cm side. A grit blasting machine was filled with silicon carbide particles of 100-250 micron in grain size as in Example 2. The catalyst prism was then grit blasting by means of this machine in the direction of its 1x1 cm side so that the airborne abrasive grains came through the passages of the catalyst. The passages of the catalyst were observed time by time by means of a loupe and it has been found that the active layer on the passage walls in the catalyst was successively thinning then completely wore.

The above examples clearly show that both selective powdering and separation of fine powder enriched in noble-metals from the substrate can be achieved by different methods and it is obvious to a person skilled in the art to apply several other solutions, which are therefore comprised in the scope of the invention claimed in attached claims.