Method for decomposing SiC or SiC-containing materials

Abstract

A method for the decomposition of SiC or SiC-containing materials is disclosed in which the reaction is induced exclusively through gaseous products to achieve as complete a conversion as possible. A preferred application is the recycling process of catalytic materials comprising platinum metal on a support material made of silicon carbide (SiC). In a thermal process, the catalytic material is released from the support material and can then be further purified.

Description

[Technical field]

[0001] The present invention relates to a method for the decomposition of SiC or SiC-containing materials, in which the reaction is induced exclusively through gaseous products in order to achieve as complete a conversion as possible. A preferred application is the recycling process of catalytic materials comprising platinum metal on a support material made of silicon carbide (SiC). In a thermal process, the catalytic material is released from the support material. [Background technology]

[0002] In technology, catalysts are used for various reactions to promote them or to make them possible in the first place. Usually for this purpose they are applied, most often in a thin layer, on a support material, which on the one hand increases the surface available for the reaction and on the other hand thereby simultaneously reduces the required amount of expensive catalytic metal. Furthermore, application on a support material increases the mechanical strength of the catalyst. In addition, it makes the supported catalyst easier to handle, apply in chemical reactors and protect against unwanted emissions. In the case of exhaust gas catalytic converters for combustion engines or plants, their use is first made possible by the support structure, since the channel structure plated with the catalytic metal actually allows an efficient flow of the exhaust gases and their contact with the catalytic metal.

[0003] As support materials, especially ceramic materials have proven their value because they are characterized by mechanical stability and inertness in the required reaction conditions. In particular, silicon carbide (SiC) is increasingly used as a catalyst support material. Recycling of these catalytic materials is an interesting problem for several reasons. On the one hand, the catalytically active materials applied are often expensive or very expensive metals, due to their rarity or the difficulties of their production. An example is the particularly frequently used platinum metal.

[0004] Platinum metals, also known in English usage as platinum group metals (PGM) or platinum group elements (PGE), refer to the elements in groups 8 to 10 of the fifth and sixth periods of the periodic table. Thus, they include the precious metals ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir) and platinum (Pt).

[0005] On the other hand, clever reaction-guided processing can also yield economically interesting by-products in addition to the recovered catalytic material. Thus, for example, it is possible to crystallize particularly pure silicon that could find a buyer in the semiconductor industry. However, the quantities achieved to date are still rather modest, so that recycling is mainly carried out from the perspective of recovering the catalytic metals.

[0006] As is also typical for heterogeneous catalysis, especially for oxidation gas-solid reactions, ceramic materials are primarily used as support materials in exhaust gas catalytic converters for automobiles. In the case of catalytic converters for gasoline engines, which have been installed since the early 90s, cordierite is usually used. For recycling, this magnesium aluminosilicate ceramic can be melted very well in high-temperature electric furnaces. The melting is carried out under reducing conditions. There, the ceramic is separated, releasing oxygen, from the bound precious metals, which are obtained in high yields as so-called collected metals.

[0007] The support material of diesel particulate filters (DPF) for diesel engines is significantly different from that for gasoline engines. Typically, in the case of diesel particulate filters, the support material consists of SiC. During recycling, this material requires a significantly different melting process than cordierite. Here, with the addition of oxygen, oxidative melting takes place in order to convert the carbide carbon into carbon dioxide. Only after this is an efficient recovery of the precious metals possible.

[0008] Problems arise during the recycling process not only when both types of catalysts for gasoline engines and diesel particulate filters are mixed, which becomes almost impossible or at least uneconomical if they contain foreign matter above a certain concentration, but also in the case of diesel particulate filters alone. In the process of treating diesel particulate filters at temperatures starting from about 800 °C in an oxidizing atmosphere on silicon carbide, a glass-like coating made of SiO2 is formed, which slows down and eventually completely stops further reactions. To accommodate this surface passivation, very high temperatures are used to oxidize the silicon carbide in an oxidizing atmosphere, significantly exceeding the melting point of SiO2 (1,710 °C) to 1,700 °C, so that it can be melted together with the catalytic metals. This means a considerable expenditure of energy.

[0009] However, it is difficult to avoid the formation of SiO2. One approach in this connection is to lower the oxygen partial pressure in the reaction chamber by means of a gas mixture with a low oxygen content. This leads to the formation of gaseous SiO2 instead of glassy SiO2. But here, in practice, too high an oxygen partial pressure occurs on the SiC support material, and nevertheless it is inevitable that SiO2, which passivates the surface, is also formed. Moreover, if little oxygen is supplied, the reaction time increases.

[0010] DE 43 05 647 A1 describes a method for the recovery of valuable metals from used exhaust gas catalytic converters, which follows a reverse approach in order to separate the precious metals and not the support material. For this purpose, the optionally ground catalytic converter material is mixed with alkali chloride and heated in a rotating cylindrical furnace under a chlorine atmosphere at temperatures between 350 ° C and 700 ° C for 0.2 h to 3 h. Thus, a direct conversion of platinum metal into water-soluble hexachloro compounds is achieved. The discharged reaction mass is then extracted with water and hydrochloric acid, and the extract is further processed in the usual way. In this method, the support material of the catalytic converter is not altered and can therefore also be reused. Only the valuable metals are put into solution.

[0011] This is an improved form of reaction of the material being treated with chlorine and / or hydrogen chloride gas at high temperatures. In contrast to pyrometallurgical processes, the reaction temperatures are low and no slag is produced. However, it is necessary to carry out laborious processing of the reaction products using wet chemical methods and to use a strong atmosphere of chlorine.

[0012] EP 0767243 discloses a method for recovering active components from supported or bulk catalysts by reaction with substantially water-free hydrogen halides and, optionally, fractional separation. In said method, the catalytic material is reacted in a cylindrical furnace, while being maintained in its original form, with substantially water-free hydrogen halides at temperatures between 20°C and 900°C and pressures between 0.01 and 10 bar. For example, in the case of platinum and palladium, this is achieved in the absence of oxygen. Support materials suitable for catalysts include, in particular, SiC. Processing is preferably carried out at normal pressure and between 150°C and 700°C. The chlorides formed can be discharged in gaseous form or solubilized with acid. The hydrogen halide gas is preferably diluted with an inert gas, preferably nitrogen. Thus, here too, there is a significant disadvantage that a subsequent treatment using wet chemical methods must be carried out to obtain the platinum metal, and that it is necessary to work in a strong atmosphere of hydrogen chloride.

[0013] Thus, the prior art methods have in common that they require laborious treatments using wet chemical methods and reactions in the gas phase with powerful chlorine or hydrogen chloride gases at high temperatures to separate the platinum metal from the SiC support material, whereas the separation of the SiC support material from the platinum metal requires very high temperatures, resulting in high energy demands or very long reaction times. Summary of the Invention [Problem to be solved by the invention]

[0014] The object of the present invention is therefore to provide an improved method for decomposition of SiC or SiC-containing materials, which is not impaired by the disadvantages of the prior art. When a method for separating platinum metal from catalyst materials is used, it should be possible to achieve an almost residue-free separation of the SiC support material from the platinum metal, and thus a method as economical as possible, particularly for catalyst support materials based on SiC. [Means for solving the problem]

[0015] This object is solved by a method according to claim 1. Variations of advantageous embodiments are the subject matter of the dependent claims.

[0016] According to the present invention, there is provided a method for decomposing SiC or SiC-containing material, comprising the steps of: feeding SiC or a SiC-containing material and an additive in the form of one or more oxygen-containing compounds, excluding oxygen, into a reactor under reduced pressure; The temperature and pressure in the reactor are set so that the equilibrium partial pressure of oxygen in the reactor is lower than the partial pressure of oxygen in the oxygen-containing compound, such that the equilibrium reaction between the oxygen-containing compound and oxygen in the lower oxidation state is shifted toward the formation of the oxygen-containing compound and oxygen in the lower oxidation state; lower than the partial pressure of oxygen in the SiO2 formed from the SiC by oxidation of the additive with oxygen, so as to avoid the formation of condensed SiO2 on the surface of the SiC; Adjust so that For the oxidation of SiC, only oxygen is added in the form of an additive.

[0017] According to the invention, the conditions of the method are selected such that the formation of a passivating SiO2 layer on the SiC or SiC-containing material is avoided and an almost complete transfer of silicon carbide into the gas phase is achieved. Here, silicon carbide is oxidized by oxygen-containing compounds, and under reaction conditions, almost exclusively gaseous products are formed, which are rapidly removed from the surface by decompression. The formed volatile reaction products leave the reaction zone via the gas phase, so that there is no kinetic inhibition of the reaction progress by the deposition of reaction products. The reaction can be controlled by the oxygen partial pressure of the reaction partner, which is influenced by the temperature, pressure and oxygen partial pressure in the reactor.

[0018] Here, the equilibrium reaction of oxygen-containing compounds and oxygen to the reduced form is targeted to the oxygen release side by adjusting the oxygen partial pressure in the reactor lower than that of the oxygen-containing compounds, which is realized by selecting the appropriate pressure and temperature in the reactor. At the same time, the partial pressure of oxygen in the reactor must be lower than the oxygen partial pressure in the SiO2 formed from SiC by oxidation, whereby oxygen is released, so that the equilibrium reaction of SiO formed from SiC by further oxygen to SiO2 in the first step is shifted to the SiO side. This will be further explained below.

[0019] What is important for the invention is that elemental oxygen is not added to the reactor in the form of a gas, but the oxygen required for the oxidation of SiC is generated exclusively by the decomposition equilibrium of the added oxygen-containing compounds. In the case of SiC-containing materials, additional oxygen can be generated by the decomposition of these further materials. Thus, for example, besides SiC, the catalyst support material based on SiC can also contain additional substances such as SiO2, Al2O3 or other oxides that can release oxygen under the process conditions. This is also envisaged according to the invention.

[0020] Particularly preferably, the partial pressure of oxygen in the reactor is 10 -13 hPa. For example, 1·10 -14 Less than 2·10 hPa -14 Less than 3·10 hPa -14 Less than 4·10 hPa -14 Less than 5·10 hPa-14 Less than 6·10 hPa -14 Less than 7·10 hPa -14 Less than 8·10 hPa -14 Less than hPa or 9·10 -14 It can be less than 1·10 hPa. -16 hPa, at least 2·10 -16 hPa, at least 3·10 -16 hPa, at least 4·10 -16 hPa, at least 5·10 -16 hPa, at least 6·10 -16 hPa, at least 7·10 -16 hPa, at least 8·10 -16 hPa, or at least 9·10 -16 In particular, the oxygen partial pressure in the reactor can be 10 -16 hPa≦p(O2)<10 -13 hPa, 10 -15 hPa≦p(O2)<10 -13 hPa, or 10 -14 hPa≦p(O2)<10 -13 hPa.

[0021] In a particularly preferred embodiment variant, the SiC-containing material comprises a catalyst support material. In a particularly preferred embodiment variant, the SiC-containing material further comprises platinum metal, and a separation of the platinum metal from the catalyst support material is performed. In such a method, after evaporating the SiC support material, the platinum metal remains as an accumulated residue. In an optional subsequent step, it can be further purified if necessary, or in the case of a mixture of platinum metals in the catalyst, they can be separated from each other.

[0022] In a variant of the embodiment, the pressure in the reactor is preferably 0.001 hPa to 900 hPa, more preferably 0.01 hPa to 800 hPa, more preferably 0.02 hPa to 700 hPa, more preferably 0.03 hPa to 600 hPa, more preferably 0.04 hPa to 500 hPa, more preferably 0.05 hPa to 400 hPa, more preferably 0.06 hPa to 300 hPa, more preferably 0.07 hPa to 250 hPa, more preferably 0.08 hPa to 200 hPa, more preferably 0.09 hPa to 150 hPa, and most preferably 0.1 hPa to 100 hPa. The pressure in the reactor can be particularly preferably at least 0.001 hPa, more preferably at least 0.01 hPa, more preferably at least 0.02 hPa, more preferably at least 0.03 hPa, more preferably at least 0.04 hPa, more preferably at least 0.05 hPa, more preferably at least 0.06 hPa, more preferably at least 0.07 hPa, more preferably at least 0.08 hPa, more preferably at least 0.09 hPa, most preferably at least 0.1 hPa. In particular, the pressure in the reactor can be preferably at most 900 hPa, more preferably at most 800 hPa, more preferably at most 700 hPa, more preferably at most 600 hPa, more preferably at most 500 hPa, more preferably at most 400 hPa, more preferably at most 300 hPa, more preferably at most 250 hPa, more preferably at most 200 hPa, more preferably at most 150 hPa, most preferably at most 100 hPa. By adjusting the pressure in the reactor, the equilibrium reaction between silicon carbide and the oxygen-containing compound can be controlled in a targeted manner.

[0023] The temperature to which the SiC or SiC-containing material and additives are heated can be between 1,000 ° C. and 1,650 ° C., preferably between 1,100 ° C. and 1,625 ° C., more preferably between 1,200 ° C. and 1,600 ° C., most preferably between 1,300 ° C. and 1,600 ° C. In particular, the temperature can be preferably at least 1,100 ° C., more preferably at least 1,150 ° C., more preferably at least 1,200 ° C., more preferably at least 1,250 ° C., most preferably at least 1,300 ° C. In particular, the temperature can be preferably up to 1,625 ° C., most preferably up to 1,600 ° C. or 1,550 ° C. This temperature range has been shown to be advantageous since it achieves an optimization of the reaction rate, the heat load of the reactor, the required reduced pressure, and the shift of the equilibrium towards the gaseous decomposition products.

[0024] In a variant of the embodiment, the oxygen-containing compound is selected from the group consisting of CO2, H2O, and metal oxides or semi-metal oxides. Particularly preferred are metal oxides and semi-metal oxides that are capable of forming gaseous suboxides under the reaction conditions.

[0025] In a variation of the embodiment, the metal oxide or semi-metal oxide is heated for 10 minutes at between 1300° C. and 1700° C. -11 It has an equilibrium partial pressure of oxygen of less than 1·10 hPa. ―12 hPa or less, 2·10 -12 hPa or less, 3·10 -12 hPa or less, 4·10 -12 hPa or less, 5·10 -12 hPa or less, 6·10 -12 hPa or less, 7·10 -12 hPa or less, 8·10 -12 hPa or less, or 9·10 -12 It may be less than 1·10 hPa. -14 hPa, at least 2·10 -14 hPa, at least 3·10 -14 hPa, at least 4·10 -14 hPa, at least 5·10 -14 hPa, at least 6·10 -14 hPa, at least 7·10-14 hPa, at least 8·10 -14 hPa, or at least 9·10 -14 In particular, the equilibrium partial pressure of oxygen may be 10 -14 hPa≦p(O2)≦10 -11 hPa, 10 -13 hPa≦p(O2)≦10 -11 hPa, or 10 -12 hPa≦ p(O2)≦10 -11 hPa.

[0026] Preferably, the metal oxide or semi-metal oxide is selected from the group consisting of SiO2 and Al2O3.

[0027] The mix ratio by weight of the SiC-containing material to the metal oxide or semi-metal oxide may be between 2:1 and 1:2.

[0028] The reaction equation for the equilibrium reaction between silicon carbide and an oxygen-containing compound, for example, in the case of SiO2 and Al2O3, is as follows:

[0029] [ka]

[0030] [ka]

[0031] As can be easily seen, the equilibrium can be shifted to the right by reducing the pressure.

[0032] The formation of volatile suboxides is thermodynamically dependent on the partial pressure of oxygen in the reactor, which in this case is determined by the CO / CO2 gas equilibrium. This equilibrium in the presence of carbon or, as in this case, carbon-containing substances, is quantitatively described by the known Boudouard equilibrium.

[0033] [ka]

[0034] The relationship between the partial pressures of carbon monoxide, carbon dioxide, and oxygen is expressed, for example, by the following formula.

[0035] [ka]

[0036] According to the thermodynamic data for free enthalpy, the equilibrium partial pressures are:

[0037]

number

[0038] The appropriate boundary conditions (high temperature, low pressure) shift the CO / CO2 equilibrium very strongly towards carbon monoxide, allowing the oxygen partial pressure in the reaction chamber to be very low. CO / P CO2 depends on pressure and temperature. At 1,500°C and the total pressure in the reaction chamber is about 1 hPa, the equilibrium partial pressures of CO2, CO, and O2 are p CO2 =9 10 -8 hPa, p CO2 ≒1hPa, p O2 =2 10 -19 Under the same conditions, the partial pressure of oxygen in silicon dioxide is p O2 (in SiO2)=3·10 -15 hPa.

[0039] In order to avoid the formation of silicon dioxide during the reaction, in the method according to the present invention, the conditions of the reaction front are designed so that the partial pressure of oxygen at this point is significantly lower than the equilibrium partial pressure of oxygen during the silicon dioxide reaction corresponding to each reaction condition.In this way, only gaseous reaction products (silicon monoxide, carbon monoxide) are produced, which escape at the reaction front and do not hinder the progress of the reaction.

[0040] Such reaction guidance according to the invention, as exemplarily shown for SiO2 and Al2O3 (see Equations 1 and 2), can be used for all oxygen-containing compounds that form volatile suboxides and / or are gaseous. An example of a gaseous oxygen-containing compound is CO2 according to the overall reaction equation shown below:

[0041] [ka]

[0042] In Figure 1, the partial pressure diagram of oxygen is plotted for various process conditions. Here, the pressure in the reactor is assumed to be related to the sum of the partial pressures of carbon monoxide, carbon dioxide, oxygen and silicon monoxide. Shown are the partial pressures of oxygen and the corresponding reactor pressures for the two reactions: The difference in partial pressures of oxygen directly correlates to the free enthalpy of reaction to silicon monoxide according to equation 7 and is a measure to avoid the formation of SiO2.

[0043] [ka]

[0044] [ka]

[0045] [ka]

[0046] This plot clearly shows that at temperatures well below 1300°C, the partial pressure of oxygen in silicon dioxide is so low that the total pressure must be reduced in an extremely laborious manner to decompose SiO2.

[0047] It has also been shown that at higher temperatures the decomposition of silicon dioxide shifts to higher oxygen partial pressures. As a result, therefore, higher process pressures can also be achieved. However, higher process temperatures always result in higher power losses and higher loads on the plant.

[0048] The SiC or SiC-containing material can be fed to the reactor in crushed, crushed and / or untreated form. The expression "untreated" in this context relates to the absence of mechanical comminution of the SiC or SiC-containing material and can therefore be understood as a synonym of "not mechanically crushed". Here, the advantages and disadvantages have to be balanced, whether the increase in surface area and thus the increase in reaction rate due to crushing or crushing into powders or granules justifies an additional preparation step. In the case of solid oxygen-containing compounds, crushing or crushing is particularly advantageous in order to be able to mix them. Here, the particle size may be, for example, in the range of 10 μm to 100 μm for powders and 100 μm to 20 mm for crushed granules. In the case of gaseous oxygen-containing compounds, untreated SiC or SiC-containing materials can also be used without problems. Moreover, this also depends on the type of SiC or SiC-containing material. In the case of large catalysts, such as diesel particulate filters, they tend to rather have to be crushed, whereas catalysts for chemical plants are in most cases already small and can therefore be used without further crushing.

[0049] Preferably, the reaction is carried out in a reactor that operates continuously.In particular, when using small SiC or SiC-containing materials and solid oxygen-containing compounds, a continuous reactor is advantageous because it can easily integrate mixing and transport functions, thus avoiding the charging time of batch plants.However, in the case of larger diesel particulate filters, batch processing can also be realized with gaseous oxygen-containing compounds, for example in a vacuum oven.

[0050] Preferably, the reactor is a rotary cylindrical furnace, a continuous furnace, a fluidized bed reactor or a flatbed furnace. Most preferably, the continuous furnace is a pusher furnace. The latter is particularly suitable for economically processing unground catalyst in a continuous process.

[0051] For these reactor types, the reaction time is preferably between 0.25 and 10 hours. It may be, for example, between 0.5 and 9.5 hours, between 0.75 and 9 hours, between 1 and 8.5 hours, between 1.5 and 8 hours, between 2 and 7.5 hours, or between 2.5 and 7 hours. Depending on the reactor type used and the particle size used, the reaction time can be adjusted. Short reaction times can be achieved if a large amount of heat is introduced into the powder material, as in the case of a fluidized bed reactor. For example, if unground diesel particulate filters, which must be treated in a vacuum oven, are selected as starting material, a correspondingly longer reaction time is required.

[0052] In a variant of the embodiment, the heating is achieved by thermal radiation, in particular of graphite, SiC or metal heaters, or by microwave radiation. These heating methods have the advantage that they ensure efficient heating of the material even under reduced pressure in the reactor.

[0053] In a further embodiment variant, the reactor is a plasma burner.

[0054] The reaction time for this reactor type is preferably between 0.1 and 5 seconds. It can be, for example, between 0.2 and 4.5 seconds, between 0.3 and 4 seconds, between 0.4 and 3.5 seconds, between 0.5 and 3 seconds, between 0.75 and 2.5 seconds, or between 1 and 2 seconds. Very short reaction times can be achieved because the temperature in the plasma is very high and a large amount of heat is introduced into the powder material.

[0055] In a variant of the preferred embodiment, the heating is realized in a plasma burner, to which the SiC or SiC-containing material and additives are supplied, and the reaction takes place directly in the plasma flame. The plasma burner can also be operated under reduced pressure. Large amounts of heat can be easily and efficiently transferred to the SiC or SiC-containing material via the generated plasma. This allows high throughputs with very short reaction times. Here, the SiC or SiC-containing material and additives have to be provided in a ground state as a powder so that they can be fed to the plasma burner together with the combustible gas. This process direction has the advantage that particularly small plant sizes can be realized.

[0056] Preferably, H2O can be used here as an additional oxygen-containing compound and can be fed to the plasma burner together with the hydrocarbon. To adjust the low oxygen partial pressure, the reaction is returned to the equilibrium water / hydrogen according to the reaction equation.

[0057] [ka]

[0058] In variants of the embodiment, the mass loss of the SiC or SiC-containing material can be at least 65%, preferably at least 70%, or at least 75%, or at least 80%, or at least 85%, or in particular at least 90%, based on the SiC portion. In variants of the embodiment, the mass loss can be up to 99.5%, or up to 99%, or up to 98%, or up to 97%. [Brief description of the drawings]

[0059] [Figure 1] 1 shows a diagram of oxygen partial pressure under various process conditions. [Diagram 2] 2 shows the particle size distribution of the SiC-containing starting material of Example 1. [Diagram 3] 2 shows the particle size distribution of the SiC-containing starting material of Example 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0060] The particle size distribution of the ground material was determined by sieve analysis on a RETSCH sieve stack, model AS200 control, based on DIN 66165-2:2016-08. The work was carried out without separation of the fine fraction prior to sieving, with an amplitude of 0.7 mm / “g”, a sieving time of 20 min and an interval time of 1 s.

[0061] 1.Flat bed furnace The SiC-containing material in this example consisted of catalyst material from a diesel particulate filter, containing a SiC-based support material and an active coating with the platinum metals Pt and Pd. It was ground in a screen ball mill to the particle size distribution shown in Figure 2. It was then mixed with DORSILIT sand (SiO2 content 99.1 wt%) in a 1:1 ratio by mass and added to an Al2O3 crucible. The SiC portion of the starting material was approximately 80 wt% (based on catalyst material).

[0062] The mixture in the Al2O3 crucibles was reacted in a vacuum furnace consisting of a water-cooled steel chamber and a treatment zone equipped with a graphite heater at a treatment temperature of 1,540 °C and a treatment time of 3.5 h. The starting mass (based on the total mixture of catalyst material and sand) was reduced by 90%. During the process, the average pressure in the reactor was 0.9 hPa. Subsequent chemical analysis showed a 10.3-fold enrichment of platinum; for palladium, a 9.8-fold enrichment. The chemical analysis was in agreement with the mass balance. Unequivocal identification of CO as a gaseous product evolved during the process was possible by mass spectrometry. SiO-containing residues were identified in filters downstream of the plant.

[0063] 2. Plasma burner A SiC-containing material similar to the catalytic material derived from a diesel particulate filter as in Example 1 was ground in a screen ball mill to the particle size distribution shown in Figure 3. Afterwards, an Ar / CO2 / H2 mixture (approximately 50 vol.% Ar, 45 vol.% CO2, and 5 vol.% H2) was directly transported and reacted by a plasma burner. The plasma burner was operated at a chamber pressure of 0.5-10 hPa. Based on similar experiments, the reaction time of the feedstock in the plasma zone was determined to be 0.1-0.5 seconds. No direct measurement of the temperature in the plasma zone was performed, but with the selected configuration and process parameters, plasma temperatures significantly higher than 10,000 K can be expected. Prior to the experiment, a characteristic spectrum of the chemical composition of the feedstock was recorded, which was compared with the spectrum of the product. This showed that the SiC was reduced by 70% (based on the original SiC content in the catalytic material). Chemical analysis of the product by inductively coupled plasma mass spectrometry (ICP-MS) showed that platinum was enriched by 7.3 times and palladium by 6.6 times.

Claims

1. 1. A method for decomposing SiC or SiC-containing material, comprising the steps of: feeding the SiC or SiC-containing material and an additive in the form of one or more oxygen-containing compounds, excluding oxygen, into a reactor under reduced pressure; The temperature and pressure in the reactor are adjusted so that the equilibrium partial pressure of oxygen in the reactor is a partial pressure of oxygen in the oxygen-containing compound such that the equilibrium reaction between the oxygen-containing compound and oxygen at a lower oxidation state from the oxygen-containing compound is shifted toward the formation of the oxygen-containing compound and oxygen at a lower oxidation state; Condensed SiO on the surface of the SiC ２ The SiO formed from the SiC by oxidation of the additive with oxygen is avoided so as to form ２ lower than the partial pressure of oxygen in Adjust so that adding only oxygen in the form of the additive for the oxidation of the SiC; method.

2. The oxygen partial pressure in the reactor is 10 －１３ The method of claim 1, wherein the pressure is less than 100 kPa.

3. 3. The process according to claim 2, wherein the pressure in the reactor is from 0.001 hPa to 900 hPa, in particular from 0.1 hPa to 100 hPa.

4. The oxygen-containing compound is CO ２ , H ２ 2. The method of claim 1 , wherein the oxide is selected from the group consisting of O, and a metal oxide or semi-metal oxide.

5. The metal oxide or semi-metal oxide is heated to a temperature between 1300° C. and 1700° C. for 10 －１１ 5. The method of claim 4, wherein the oxygen has an equilibrium partial pressure of 0.1 hPa or less.

6. The metal oxide or semi-metal oxide is SiO ２ and Al ２ O ３ The method of claim 4, wherein the compound is selected from the group consisting of:

7. 10. The process of claim 1, wherein the reaction is carried out in a continuously operating reactor.

8. 8. The method of claim 7, wherein the reactor is a rotary cylindrical furnace, a continuous furnace, a fluidized bed reactor, or a flat bed furnace.

9. 9. The process of claim 8, wherein the reaction time is between 0.25 and 10 hours.

10. The method of claim 1 , wherein the SiC or SiC-containing material and the additives are heated to a temperature of from 1000° C. to 1650° C.

11. 11. The method according to claim 10, wherein the heating is achieved by thermal radiation, in particular of a graphite, SiC or metal heater, or by microwave radiation.

12. The method of claim 1 , wherein the reactor is a plasma burner.

13. 13. The method of claim 12, wherein the reaction time is between 0.1 and 5 seconds.

14. 13. The method of claim 12, wherein the heating is achieved in a plasma burner to which the SiC or SiC-containing material and the additive are supplied, and the reaction occurs directly in the plasma flame.

15. Oxygen-containing compounds include H ２ 13. The method of claim 12, wherein O is used and is fed to the plasma burner along with a hydrocarbon.

16. The method of claim 1 , wherein the SiC or SiC-containing material is provided to the reactor in crushed, ground, and / or unprocessed form.

17. 2. The method according to claim 1, wherein the mass loss of the SiC or SiC-containing material is at least 65%, in particular at least 90%, based on the SiC portion.

18. The method of claim 1 , wherein the SiC-containing material comprises a catalyst support material.

19. 20. The method of claim 18, wherein the SiC-containing material further comprises platinum metal, and separation of the platinum metal from the catalyst support material is achieved.

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