Process for the capture of a noble metal, especially rhodium and / or platinum, lost by volatilization from a catalyst to a high heated gas stream by using an oxide of formula a2o3

Abstract

The present invention relates to a process for the capture of a noble metal, especially of rhodium and / or platinum, lost by volatilization from a catalyst to a high heated gas stream (including local heating due to a highly exothermic reaction) by contacting the highly heated gas stream containing the volatilized noble metal with a first oxide element comprising an oxide of formula A2O3, especially Nd2O3, as well as the use of an oxide of formula A2O3, especially Nd2O3 for capture of such a noble metal or catchment devices comprising an oxide of formula A2O3, especially Nd2O3. This process is especially useful in relation to the industrial processes like the Ostwald process (showing a highly exothermic reaction) where a catalyst containing rhodium and platinum is used. In selected circumstances these oxides may also act on the decomposition of unwanted N2O arising in said Ostwald process.

Description

[0001] K.A. Rasmussen

[0002] Process for the capture of a noble metal, especially rhodium and / or platinum, lost by volatilization from a catalyst to a high heated gas stream by using an oxide of formula A2O3

[0003] FIELD OF THE INVENTION:

[0004] The present invention relates to a process for the capture of a noble metal, especially of rhodium and / or platinum, lost by volatilization from a catalyst to a high heated gas stream (including local heating due to a highly exothermic reaction) by contacting the highly heated gas stream containing the volatilized noble metal with a first oxide element comprising an oxide of formula A2O3, especially Nd20s, as well as the use of an oxide of formula A2O3, especially Nd20s for capture of such a noble metal or catchment devices comprising an oxide of formula A2O3, especially Nd2Os. This process is especially useful in relation to the industrial processes like the Ostwald process (showing a highly exothermic reaction) where a catalyst containing rhodium and platinum is used. In selected circumstances these oxides may also act on the decomposition of unwanted N2O arising in said Ostwald process.

[0005] BACKGROUND OF THE INVENTION:

[0006] Chemical processes on an industrial scale often rely on catalysts of noble metals. One of the metals used in this way is rhodium, a highly precious metal that is lost from the catalyst over time, especially if the process is proceeding at high temperatures and / or is highly exothermic. One of these industrial processes is the Ostwald process. Nitrogen-based inorganic fertilizers are produced from nitric acid obtained in the Ostwald process. In the first step, ammonia is oxidized over a Pt-Rh (typically 95:5 wt%) catalytic gauze at high temperature and moderate pressure to produce nitric oxide (NO). Under industrial conditions the yields achieved with the catalytic gauzes are 95-97 % depending on pressure and temperature. The strong greenhouse gas nitrous oxide (N2O) is an unwanted byproduct. Due to the highly exothermic nature of the oxidation reaction, Pt and Rh are lost as PtO2 and RhO2 into the gas phase, with Pt being the dominating loss. Along with the cost of the ammonia feedstock, metal loss causes the largest costs in the production of nitric acid. Capturing and recycling of the precious metals is therefore a key problem that needs to be solved.

[0007] There are different Pt catchment systems that have been utilized industrially to reduce the Pt loss including glass wool filters, Raschig rings, marble chips and Pd-X alloys (X = Au, Cu, Co, Ni). The most common technology used today is woven Pd-Ni (95:5 wt%) catchment gauzes installed downstream of the Pt-Rh catalyst gauzes; capturing the formed gaseous PtO2 and incorporate Pt into the Pd based alloy. Unfortunately, there are a few drawbacks with the Pd-Ni catchment system. Complete reconstruction of the Pd-Ni wire give rise to swelling and significant blockage of the gauzes; which in turn creates an undesired pressure drop. In addition, Pd is lost into gas phase, affecting the cost-benefit of the process.

[0008] One other path of Pt catchment that was explored was the identification of CaO to be suited for Pt catchment due to the possible formation of CaxPt3O4 (0 < x < 1) (“N.I. Zakharchenko, Recovery of platinum with calcium oxide sorbent in ammonia oxidation, Russ. J. Appl. Chem. 75 (2002) 402-407”).

[0009] Still, it remains an important task to find alternative and improved ways for the capture of noble metals, especially rhodium or platinum, that get lost from catalysts during high temperature industrial processes.

[0010] SUMMARY OF THE INVENTION:

[0011] This task is solved by the present invention.

[0012] The present invention discloses a process for the capture of a noble metal, selected from rhodium or platinum or both, lost by volatilization from a catalyst to a high heated gas stream by contacting the highly heated gas stream containing the volatilized noble metal with a first oxide element comprising an oxide of formula A2O3, especially Nd20s, as well as the use of an oxide of formula A2O3, especially Nd20s, for capture of such a noble metal or catchment devices comprising an oxide of formula A2O3, especially Nd20s,. The invention is directed in a main aspect to a process for the capture of at least one noble metal being selected from rhodium and platinum lost by volatilization from a catalyst comprising the at least one noble metal to a high heater gas stream contacted therewith in a high temperature gas reaction carried out at temperatures of at least 700°C which comprises contacting such highly heated gas stream, after its contact with such catalyst, which contains the volatilized at least one noble metal while such volatilized noble metal is still essentially in the vapor phase and at a temperature of at least 700 °C with a first oxide element comprising at least one oxide selected from an oxide of formula A2O3 with A being selected from rare earth elements / lanthanoids, optionally with one or more elements on A position in form of a solid solution.

[0013] The invention is based on the surprising effect that the oxides of formula A2O3, especially Nd2C>3, are / is able to highly effectively capture platinum or rhodium, especially both, if these noble metals are mobilized / volatilized by the high temperature gas reaction from a catalyst. The inventors have seen this in their experiments showing a clear advantage over CaO - known from the art to capture platinum. The inventors have found that the use of Nd2C>3 in this process was able to capture both platinum and rhodium and furthermore especially platinum to a much larger extent than seen in the art (CaO).

[0014] FIGURES:

[0015] Fig. 1 ) shows the result of a 26 days experiment for the catchment of platinum and rhodium (starting with 10 wt.% Rh) in a 5- zone furnace at 700, 800 and 900°C with CaO, showing the respective relations of the detected metals Ca, Pt, and Rh at the various temperatures (see Example 1 ).

[0016] The results seen on Fig. 1 ) are as follows:

[0017] - at 700°C the respective relations of the detected metals are: o 100% Ca at 800°C the respective relations of the detected metals are: o 98% Ca o 2% Pt

[0018] - at 900°C the respective relations of the detected metals are: o 96% Ca o 1% Pt o 3% Rh.

[0019] Fig. 2) shows 2 different views of the results of a 26 days experiment for the catchment of platinum and rhodium (starting with 10 wt.% Rh) in a 5- zone furnace at 700, 800 and 900°C with Nd2C>3, showing the respective relations of the detected metals Nd, Pt, and Rh at the various temperatures (see Example 1 ).

[0020] The results seen on Fig. 2) are as follows:

[0021] - at 700°C the respective relations of the detected metals are: o 100% Nd

[0022] - at 800°C the respective relations of the detected metals are: o 85% Nd o 14% Pt o 1% Rh

[0023] - at 900°C the respective relations of the detected metals are: o 65% Nd o 18% Pt o 17% Rh.

[0024] Fig. 3) shows the results of two 26 days experiment for the catchment of a) platinum and rhodium and b) platinum alone in a 5- zone furnace at 700, 800 and 900°C with Nd2Os, showing the respective relations of the detected metals Nd, Pt (and Rh) at the various temperatures (see Example 4).

[0025] The results seen on Fig. 3a) (Pt-Rh; 10 wt.% Rh) are as follows:

[0026] - at 700°C the respective relations of the detected metals are: o 100% Nd

[0027] - at 800°C the respective relations of the detected metals are: o 85% Nd o 14% Pt o 1% Rh

[0028] - at 900°C the respective relations of the detected metals are: o 65% Nd o 18% Pt o 17% Rh

[0029] The results seen on Fig. 3b) (Pt only) are as follows:

[0030] - at 700°C the respective relations of the detected metals are: o 100% Nd

[0031] - at 800°C the respective relations of the detected metals are: o 74% Nd o 26% Pt

[0032] - at 900°C the respective relations of the detected metals are: o 92% Nd o 8% Pt.

[0033] DETAILED DESCRIPTION OF THE INVENTION:

[0034] The invention relates to a process for the capture of at least one noble metal being selected from rhodium and platinum lost by volatilization from a catalyst comprising the at least one noble metal to a high heater gas stream contacted therewith in a high temperature gas reaction carried out at temperatures of at least 700°C which comprises contacting such highly heated gas stream, after its contact with such catalyst, which contains the volatilized at least one noble metal while such volatilized noble metal is still essentially in the vapor phase and at a temperature of at least 700 °C with a first oxide element comprising at least one oxide selected from

[0035] - an oxide of formula A2O3 with A being selected from rare earth elements / lanthanoids, optionally with one or more elements on A position in form of a solid solution. As said above, the invention is based on the surprising effect that these oxides (of formula A2O3), especially Nd20s, are / is highly effective in capturing platinum - if mobilized by the high temperature gas reaction from a catalyst - but that it is also able to highly effectively capture rhodium. This is especially true if seen on the experiments of EXAMPLE 1. In these experiments showing the use of Nd20s compared to CaO - known from the art to capture platinum - showed that the use of Nd20s in this process was able to capture platinum and rhodium and further more to a much larger extent than seen in the art (CaO). This was not predictable over what is described in the art, with the art being - especially on rhodium capture - mostly silent.

[0036] In a preferred embodiment of the process according to the invention said oxide is an oxide of formula A2O3 with A being selected from La, Ce, Pr, Nd, Pm, Sm, Eu and Gd; or from La, Nd, Pm, Sm, Eu and Gd; or from La, Ce, Pr, Nd, Pm, Sm, Eu and Gd; preferably from La, Nd and Gd, more preferably from La and Nd; especially wherein said oxide is selected from Nd20s, La2Os, and Gd2Os, preferably from Nd20s and Gd2Os; most preferably wherein said oxide is Nd20s.

[0037] In a thus very preferred ASPECT A), the invention relates to a process for the capture of at least one noble metal being selected from rhodium and platinum lost by volatilization from a catalyst comprising the at least one noble metal to a high heater gas stream contacted therewith in a high temperature gas reaction carried out at temperatures of at least 700°C, wherein the catalytic reaction of the high temperature gas reaction is a catalytic ammonia oxidation or catalytic ammonia combustion, which comprises contacting such highly heated gas stream, after its contact with such catalyst, which contains the volatilized at least one noble metal while such volatilized noble metal is still essentially in the vapor phase and at a temperature of at least 700 °C with a first oxide element comprising at least one oxide selected from an oxide of formula A2O3 with A being selected from Nd and Gd.

[0038] In a SUB-ASPECT A1) of ASPECT A) it is preferred if the at least one oxide is selected from an oxide of formula A2O3 with A being Nd. In another SUB-ASPECT A2) of ASPECT A) it is preferred if the at least one oxide is selected from an oxide of formula A2O3 with A being Gd.

[0039] In an alternative ASPECT B), the invention relates to a process for the capture of at least one noble metal being selected from rhodium and platinum lost by volatilization from a catalyst comprising the at least one noble metal to a high heater gas stream contacted therewith in a high temperature gas reaction carried out at temperatures of at least 700°C, wherein the catalytic reaction of the high temperature gas reaction is a catalytic ammonia oxidation or catalytic ammonia combustion, which comprises contacting such highly heated gas stream, after its contact with such catalyst, which contains the volatilized at least one noble metal while such volatilized noble metal is still essentially in the vapor phase and at a temperature of at least 700 °C with a first oxide element comprising at least one oxide selected from an oxide of formula A2O3 with A being selected from Pm, Sm and Eu.

[0040] In a SUB-ASPECT B1) of ASPECT B) it is preferred if the at least one oxide is selected from an oxide of formula A2O3 with A being Pm.

[0041] In a SUB-ASPECT B2) of ASPECT B) it is preferred if the at least one oxide is selected from an oxide of formula A2O3 with A being Sm.

[0042] In a SUB-ASPECT B3) of ASPECT B) it is preferred if the at least one oxide is selected from an oxide of formula A2O3 with A being Eu.

[0043] In an alternative ASPECT B), the invention relates to a process for the capture of at least one noble metal being selected from rhodium and platinum lost by volatilization from a catalyst comprising the at least one noble metal to a high heater gas stream contacted therewith in a high temperature gas reaction carried out at temperatures of at least 700°C, wherein the catalytic reaction of the high temperature gas reaction is a catalytic ammonia oxidation or catalytic ammonia combustion, which comprises contacting such highly heated gas stream, after its contact with such catalyst, which contains the volatilized at least one noble metal while such volatilized noble metal is still essentially in the vapor phase and at a temperature of at least 700 °C with a first oxide element comprising at least one oxide selected from an oxide of formula A2O3 with A being La. In a preferred embodiment of the process according to the invention (especially according to ASPECT A) and its SUB-ASPECTS, but also ASPECTS B) and C}) said highly heated gas stream in addition to contacting said first oxide element is further also contacting a metallic element comprising a metallic material selected from the group consisting of palladium, and palladium alloys, more specifically palladium-nickel alloys and palladiumgold alloys.

[0044] This preferred embodiment of the invention carries the additional advantage that it is based on the selection of combining a metal element such as the Pd / Ni catchment device and the oxide This is a very advantageous combination as the Pd / Ni catchment device captures platinum and the first oxide element with Nd20s helps capturing also rhodium.

[0045] In this, it is preferred in the process according to the invention when the contact with said metallic element precedes and / or is upstream from the contact with said first oxide element; or follows and / or is downstream from the contact with said first oxide element.

[0046] In a preferred embodiment of this embodiment (the process) of the invention (especially according to ASPECT A) and its SUB-ASPECTS, but also ASPECTS B) and C}) involving also said metal element, the highly heated gas stream after its contact with said catalyst is contacted with said first oxide element at a temperature at around or above 900 °C (or at 850°C to 950°C).

[0047] This specific embodiment of the invention is further based on the surprising finding that a higher rhodium capture on the oxide of formula A2O3, especially Nd20s, seems to be connected to a higher temperature. This more pronounced capture of rhodium with these higher temperatures at around 900°C can be seen in Example 1. Thus, the Nd20s does more pronouncedly capture the rhodium, while the metal element would capture the platinum.

[0048] In a preferred embodiment of this embodiment (the process) of the invention (especially according to ASPECT A) and its SUB-ASPECTS, but also ASPECTS B) and C}) there is no further oxide element, comprising metal oxides, and / or no further N2O-decomposition catalyst used in the process; and / or the first oxide element comprises only one metal oxide.

[0049] Thus, in a preferred embodiment of this process of the invention (especially according to ASPECT A) and its SUB-ASPECTS, but also ASPECTS B) and C}) there is no further oxide element, comprising metal oxides, used in the process. This feature applies especially (as one example) if the at least one oxide is selected from an oxide of formula A2O3 with A being Gd.

[0050] This means, that - in this respective and special embodiment - the process according to the invention involves only one oxide element, which comprises metal oxides. Again, this feature applies especially (as one example) if the at least one oxide is selected from an oxide of formula A2O3 with A being Gd.

[0051] In another related preferred embodiment of this process of the invention (especially according to ASPECT A) and its SUB-ASPECTS, but also ASPECTS B) and C)) there is (optionally also) no further N2O-decomposition catalyst used in the process. This feature applies especially (as one example) if the at least one oxide is selected from an oxide of formula A2O3 with A being Gd.

[0052] This means, that - in this respective and special embodiment - the process according to the invention does not involve (or - optionally - does not include in the equipment used for the process) an (additional / further) N2O-decomposition catalyst. This feature again applies especially (as one example) if the at least one oxide is selected from an oxide of formula A2O3 with A being Gd.

[0053] Possibly, in an embodiment of the invention (see below), if the highly heated gas stream also contains N2O) and this is decomposed / converted upon contact with said first oxide element, (preferably wherein the N2O is decomposed / converted to NO, NOX, N2 and / or O2) said first oxide element could (also) take the role of an (additional / further) codecomposition catalyst. In another thus preferred embodiment of this process of the invention (especially according to ASPECT A) and its SUB-ASPECTS, but also ASPECTS B) and C)) the first oxide element comprises only one metal oxide (or at least 95, 97, 98 or 99% w / w of the metal oxides comprised). This feature applies especially (as one example) if the at least one oxide is selected from an oxide of formula A2O3 with A being Nd

[0054] This means, that - in this respective and special embodiment - in the process according to the invention there is no other metal oxide (above trace amounts) comprised by the first oxide element than the at least one oxide (or this being at least 95, 97, 98 or 99% w / w of the metal oxides comprised) selected from an oxide of formula A2O3 as described and defined above, especially in ASPECT A) and its SUB-ASPECTS, but also in ASPECTS B) and C}.

[0055] In a parallel preferred embodiment of the process according to the invention (especially according to ASPECT A) and its SUB-ASPECTS, but also ASPECTS B) and C}) said highly heated gas stream in addition to contacting said first oxide element is further also contacting a second oxide element comprising at least one further oxide being different from said at least one oxide, wherein said at least one further oxide is selected from

[0056] - an oxide of formula ABO3, especially in perovskite form with A being selected from alkaline earth and rare earth elements / lanthanoids, preferably with A being selected from La, Ce, Pr, Nd, Pm, Sm, Eu and Gd, Sr, Ca and Ba, and with B being selected from 3-5d elements, and p-block elements, preferably with B being selected from Ti, V, Cr, Mn, Fe, Co, Ni, Mg, Al, Ga; optionally with one or more elements on A position in form of a solid solution or in an ordered arrangement and / or optionally with one or more elements in B-position in form of a solid solution or in an ordered arrangement and / or optionally in its respective RP phases; or

[0057] - an oxide of formula A2O3 with A being selected from rare earth elements / lanthanoids, optionally with one or more elements on A position in form of a solid solution; preferably an oxide of formula A2O3 with A being selected from La, Ce, Pr, Nd, Pm, Sm, Eu and Gd; or from La, Nd, Pm, Sm, Eu and Gd; or from La, Ce, Pr, Nd, Pm, Sm, Eu and Gd; preferably from La, Nd and Gd, more preferably from La, Ce and Nd.

[0058] It is preferred in this parallel process according to the invention if the second oxide element comprises as the at least one further oxide LaNiOs.

[0059] As an alternative it can be preferred if in this parallel process according to the invention the second oxide element comprises as the at least one further oxide an oxide as described above for - but different from - said at least one oxide of the first oxide element especially according to ASPECT A) and its SUB-ASPECTS, but also ASPECTS B) and

[0060] CL

[0061] In a preferred embodiment of this parallel process (especially according to ASPECT A) and its SUB-ASPECTS, but also ASPECTS B) and C)) according to the invention said at least one further oxide comprised in the second oxide element is selected from LaNIOs, La2NIO4, La4Ni30io, NdNIOs, Nd2NiO4, Nd4Ni30io, LaFeOs, and LaCoOs.

[0062] In a preferred embodiment of this parallel process according to the invention (especially according to ASPECT A) and its SUB-ASPECTS, but also ASPECTS B) and C)) said at least one further oxide comprised in the second oxide element is selected from LaNIOs, La2NIO4, La4Ni30io, NdNIOs, Nd2NiO4, Nd4Ni30io, and LaFeOs.

[0063] In a preferred embodiment of this parallel process according to the invention (especially according to ASPECT A) and its SUB-ASPECTS, but also ASPECTS B) and C)) said at least one further oxide comprised in the second oxide element is selected from LaNIOs, La2NIO4, La4Ni30io, LaFeOs, LaCoOs.

[0064] In a preferred embodiment of this parallel process according to the invention (especially according to ASPECT A) and its SUB-ASPECTS, but also ASPECTS B) and C}) said at least one further oxide comprised in the second oxide element is selected from LaNIOs, La2NIO4, La4Ni30io, NdNIOs and LaFeOs.

[0065] In a preferred embodiment of this parallel process according to the invention (especially according to ASPECT A) and its SUB-ASPECTS, but also ASPECTS B) and C)) said at least one further oxide comprised in the second oxide element is selected from LaNIOs, La2NIO4, La4Ni30io, NdNIOs and LaFeOs. In a preferred embodiment of this parallel process according to the invention (especially according to ASPECT A) and its SUB-ASPECTS, but also ASPECTS B) and C}) said at least one further oxide comprised in the second oxide element is selected from LaNIOs, La2NIO4, and La4Ni30 .

[0066] In a preferred embodiment of this parallel process according to the invention (especially according to ASPECT A) and its SUB-ASPECTS, but also ASPECTS B) and C)) said at least one further oxide comprised in the second oxide element is selected from NdNIOs, Nd2NIO4, Nd4Ni30io, and LaFeOs.

[0067] In a preferred embodiment of this parallel process according to the invention (especially according to ASPECT A) and its SUB-ASPECTS, but also ASPECTS B) and C}) said at least one further oxide comprised in the second oxide element is selected from NdNIOs, Nd2NIO4, Nd4Ni30io, and LaFeOs.

[0068] In a preferred embodiment of this parallel process according to the invention (especially according to ASPECT A) and its SUB-ASPECTS, but also ASPECTS B) and C)) said at least one further oxide comprised in the second oxide element is selected from LaNIOs, La2NIO4, La4Ni30io, NdNIOs, Nd2NIO4 and Nd4Ni30io.

[0069] In a preferred embodiment of this parallel process according to the invention (especially according to ASPECT A) and its SUB-ASPECTS, but also ASPECTS B) and C}) said at least one further oxide comprised in the second oxide element is selected from LaNIOs, NdNIOs, and LaFeOs.

[0070] In a preferred embodiment of this parallel process according to the invention (especially according to ASPECT A) and its SUB-ASPECTS, but also ASPECTS B) and C}) said at least one further oxide comprised in the second oxide element is selected from LaNIOs and NdNIOs.

[0071] In a preferred embodiment of this parallel process according to the invention (especially according to ASPECT A) and its SUB-ASPECTS, but also ASPECTS B) and C}) said at least one further oxide comprised in the second oxide element is selected from NdNIOs, and LaFeOs. In a preferred embodiment of this parallel process according to the invention (especially according to ASPECT A) and its SUB-ASPECTS, but also ASPECTS B) and C}) said at least one further oxide comprised in the second oxide element is LaFeOs.

[0072] In a preferred embodiment of this parallel process according to the invention (especially according to ASPECT A) and its SUB-ASPECTS, but also ASPECTS B) and C)) said at least one further oxide comprised in the second oxide element is NdNiOs.

[0073] In a preferred embodiment of this parallel process according to the invention (especially according to ASPECT A) and its SUB-ASPECTS, but also ASPECTS B) and C}) said at least one further oxide comprised in the second oxide element is LaNiOs.

[0074] It is most preferred in this parallel process according to the invention (especially according to ASPECT A) and its SUB-ASPECTS, but also ASPECTS B) and C)) if the second oxide element comprises at least one further oxide being LaNiOs.

[0075] It is further preferred in the parallel process according to the invention (especially according to ASPECT A) and its SUB-ASPECTS, but also ASPECTS B) and C}) if the contact with said second oxide element precedes and / or is upstream from the contact with said first oxide element; or if the contact with said second oxide element follows and / or is downstream from the contact with said first oxide element.

[0076] This embodiment carries the additional advantage that this combination could e.g. allow that the second oxide element can be chosen to be better suited to capture platinum while the first (e.g. comprising the oxide of formula A2O3, especially Nd20s) oxide element helps more effectively capture rhodium or vice versa (maybe also relying on different temperatures of around 800° or around 900° C depending on which noble metal to capture).

[0077] It is a preferred embodiment of the process of the invention (especially according to ASPECT A) and its SUB-ASPECTS, but also ASPECTS B) and C}), if the process according to the invention serves for the capture of both rhodium and platinum lost by volatilization from a catalyst comprising rhodium and platinum to a high heater gas stream contacted therewith in a high temperature gas reaction carried out at temperatures of at least 700°C which comprises contacting such highly heated gas stream, after its contact with such catalyst, which contains thus volatilized rhodium and platinum while such volatilized rhodium and platinum is still essentially in the vapor phase and at a temperature of at least 700 °C with said first oxide element.

[0078] This embodiment is based on the surprising effect that it was found that catchment behavior appears to be different depending on whether Pt is collected alone or together with another element as seen in the example with Rh. Thus, the oxide of formula A2O3, especially Nd20s when tested on capture of platinum alone seems to show a different behavior if compared to the situation when both platinum and rhodium are present (see Example 4 and Fig. 3). Thus, depending on the relative presence of the respective noble metal, the temperature conditions can be adapted.

[0079] In a preferred general embodiment of the process of the invention (especially according to ASPECT A) and its SUB-ASPECTS, but also ASPECTS B) and C)) the highly heated gas stream after its contact with said catalyst is contacted with said first oxide element at a temperature at around or above 800°C (or at 750°C to 900°C or at 750°C to 850°C or at 800°C to 900°C), preferably at around or above 900 °C (or at 850°C to 950°C), preferably wherein said high temperature gas reaction is carried out at temperatures of at around or above 800°C, preferably at around 900°C or above.

[0080] In a preferred embodiment of the process of the invention (especially according to ASPECT A) and its SUB-ASPECTS, but also ASPECTS B) and C}) the highly heated gas stream after its contact with said catalyst is contacted with said first oxide element at a temperature at around or above 800°C (or at 750°C to 900°C or at 750°C to 850°C or at 800°C to 900°C), or at a temperature at around or above 900 °C (or at 850°C to 950°C). In this, it might be preferred if said high temperature gas reaction is carried out at the same temperature, e.g. of at around or above 800°C, or at around 900°C or above.

[0081] This preferred broader embodiment of the invention is further based on the surprising finding that rhodium capture on the oxide of formula A2O3, especially Nd20s seems to be connected to a higher temperature. This more pronounced capture of rhodium with these higher temperatures at around 900°C can be seen in Example 1 . It can be seen there as well, that at around 800 °C Platinum capture seems optimized and dominates. The art is completely silent on this influence of temperature on rhodium or platinum capture.

[0082] In a preferred embodiment of the process of the invention (especially according to ASPECT A) and its SUB-ASPECTS, but also ASPECTS B) and C)) in the process the highly heated gas stream also contains N2O, which is decomposed / converted upon contact with said first oxide element, preferably wherein the N2O is decomposed / converted to NO, NOX, N2 and / or O2.

[0083] This is a further preferred embodiment of the process of the invention (especially according to ASPECT A) and its SUB-ASPECTS, but also ASPECTS B) and C}) which is based on that N2O seems to also be decomposed / converted by said oxides. The strong greenhouse gas nitrous oxide (N2O) is an unwanted byproduct of the Ostwald process. This would be very advantageous as thus the (first) oxide element or the oxide (e.g. Nd20s) comprised therein would serve a double purpose (or even a triple purpose if both platinum and rhodium are captured) in the process according to the invention with the additional conversion / decomposition of N2O. The art is not suggesting this aspect.

[0084] In a preferred embodiment of the process of the invention (already included in ASPECT A) and its SUB-ASPECTS, but also in ASPECTS B) and C}) the catalytic reaction of the high temperature gas reaction is a catalytic ammonia oxidation or catalytic ammonia combustion.

[0085] This refers mostly to the Ostwald process being the process to which the inventive process refers. It is especially useful for converting N2O that is - as said above - an unwanted byproduct of the Ostwald process,

[0086] In another aspect, the invention relates to a use of an oxide element comprising at least one oxide selected from an oxide of formula A2O3 with A being selected from rare earth elements / lanthanoids, optionally with one or more elements on A position in form of a solid solution for the capture of at least one noble metal being selected from rhodium and platinum, especially from a highly heated gas stream (at a temperature of at least 700 °C), which contains the volatilized at least one noble metal while such volatilized noble metal is still essentially in the vapor phase. It is highly preferred if the at least one oxide comprised by said oxide element used according to the invention is selected from an oxide of formula A2O3 with A as defined above for ASPECT A) and its SUB-ASPECTS, but also - alternatively - ASPECTS B) and C)). Thus, it is highly preferred if the at least one oxide comprised by said oxide element used according to the invention is selected from an oxide of formula A2O3 with A being selected from Nd and Gd (or - alternatively - as defined in the other ASPECTS).

[0087] In a preferred embodiment of said use according to the invention, the highly heated gas stream is at a temperature of at least 700 °C and / or the use is for the capture of rhodium and platinum.

[0088] In a preferred embodiment of said use according to the invention the use is for the capture of rhodium and platinum.

[0089] In a preferred embodiment of this use according to the invention the use is for the capture of platinum and rhodium, especially in the same process.

[0090] In a further preferred embodiment of this use according to the invention the use further encompasses the decomposition / conversion of N2O, especially in the same process, preferably wherein the N2O is decomposed / converted upon contact with said oxide element, most preferably wherein the N2O is decomposed / converted to NO, NOX, N2 and / or O2.

[0091] In another different aspect, the invention relates to a device for the capture of at least one noble metal being selected from rhodium and platinum from a combustion furnace of the type having a noble metal gauze arranged across the furnace in a direction transverse to the flow of gas therethrough, said device being an oxide element comprising or consisting of at least one oxide selected from an oxide of formula A2O3 with A being selected from rare earth elements / lanthanoids, optionally with one or more elements on A position in form of a solid solution.

[0092] In a further different aspect, the invention relates to a catchment device for the capture of at least one noble metal being selected from rhodium and platinum, in an ammonia oxidation reaction, comprising an oxide element comprising or consisting of at least one oxide selected from an oxide of formula A2O3 with A being selected from rare earth elements / lanthanoids, optionally with one or more elements on A position in form of a solid solution.

[0093] It is highly preferred if the at least one oxide comprised by said oxide element comprised by the device or catchment device according to the invention is selected from an oxide of formula A2O3 with A as defined above for ASPECT A) and its SUB-ASPECTS, but also - alternatively - ASPECTS B) and C}). Thus, it is highly preferred if the at least one oxide comprised by said oxide element comprised by the device or catchment device according to the invention is selected from an oxide of formula A2O3 with A being selected from Nd and Gd (or - alternatively - as defined in the other ASPECTS).

[0094] In a preferred embodiment of the device or catchment device according to the invention, the use of the device or catchment device is for the capture of rhodium and platinum.

[0095] In a preferred embodiment of the use according to the invention, the device according to the invention or catchment device according to the invention said oxide is an oxide of formula A2O3 with A being selected from La, Ce, Pr, Nd, Pm, Sm, Eu and Gd; or from La, Nd, Pm, Sm, Eu and Gd; or from La, Ce, Pr, Nd, Pm, Sm, Eu and Gd; preferably from La, Nd and Gd, more preferably from La and Nd; especially said oxide is selected from Nd20s, La2O3, and Gd2O3, preferably from Nd20s and Gd2Os; most preferably said oxide is Nd20s.

[0096] Definitions:

[0097] In the context of the invention “lanthanoid” is to be understood as meaning a series of chemical elements of atomic numbers 57-71 , from lanthanum through lutetium. Preferably the “lanthanoids” in the context of the invention are selected from La, Ce, Pr, Nd, Pm, Sm, Eu and Gd.

[0098] In the context of the invention “transition metal” is to be understood as meaning a chemical element in d-block od the periodic table, including groups 3 to 12. Preferably the “transition metals” in the context of the invention are selected from Fe, Co, Ni and Zn ....

[0099] Y1 In the context of the invention “alkaline earth metal” is to be understood as meaning the chemical elements Be, Mg, Ca, Sr, Ba and Rd from Group 2 of the periodic table.

[0100] In the context of the invention “alkali metal” is to be understood as meaning the chemical elements Li, Na, K, Rb, Cs and Fr from Group 1 of the periodic table.

[0101] In the context of the invention “capture” is to be understood as meaning the fixation of the noble metal that was volatilized before on e.g. an oxide element, the oxide or the metal element or a metal of the metal element.

[0102] In the context of this invention “decompose” and / or “convert” is to be understood as meaning the conversion / decomposition, especially of N2O, especially to NO, NOx, N2 and / or O2. This happens upon contact with an element, e.g. the “first oxide element”, (or the oxide comprised therein) and thus for example leads to an abatement of the laughing gas.

[0103] In the context of the invention “volatilization (from a catalyst)” is to be understood as meaning the removal of the noble metal like rhodium or platinum from e.g. the solid metal structure of e.g. the catalyst and putting this noble metal or any derivative in its “vapor phase”, including taking it up in this vapor phase e.g. in a gas stream. This volatilization usually happens at “high temperatures”.

[0104] In the context of the invention “high temperature” is to be understood as meaning at a temperature of or above 700°C.

[0105] In the context of the invention “contact” is to be understood as meaning a physical contact or close contact e.g. coming within 1 cm or less, e.g. between the gas of a “high heated gas stream” or a volatilized noble metal (or a derivative, e.g. in said gas stream with an oxide element or the metal element.

[0106] In the context of the invention “high heated gas stream” is to be understood as meaning as steam of gas like N2, NH3, air, O2, CO2 or any other gas at temperatures of or above 700°C.

[0107] In the context of the invention “perovskite” is to be understood as meaning that a perovskite is a compound, ABX3, that belong to the class of compounds that take a perovskite type structure. When X = O, the perovskite is an oxide ABO3. In the ideal perovskite structure, the B-site cation is 6-coordinated to oxygen and A-site is 12- coordinated to oxygen. A site cation is generally from (alkali earth) alkaline earth and rare earth elements whereas B site cation is generally selected from 3-5d elements, p-block elements. The perovskite oxide can have lower symmetry, being distorted, and may have oxygen vacancies in random or ordered patterns.

[0108] In the context of the invention “RP-phase” is to be understood as meaning that an RP phase is a phase that is described by the so-called Ruddlesden-Popper type structure. The general formula is An+iBnO3n+i or (ABO3)n(AO) whereof n is an integer. The atomic arrangement in ABO3 (part of the structure) is the same as in the perovskite whereas AO is a structure fragment corresponding to half a rock salt layer. A site cation is generally from alkaline earth and rare earth elements whereas B site cation is generally selected from 3-5d elements, p-block elements. A RP-phase is conveniently described by the parameter “n” in the formula An+iBnO3n+i ; for example RP1 is meaning an RP structure with n =1 and hence representing A2BO4.

[0109] In the context of the invention “in form of a solid solution” is to be understood as meaning that a solid solution is a uniform mixture of two crystalline solids that share a common crystal lattice. Solid solutions often consist of two or more types of atoms that occupy the same crystallographic site in the crystal structure in a random manner.

[0110] In the context of the invention “in an ordered arrangement” is to be understood as meaning that an ordered arrangement occurs when two or more types of atoms are having the potential to occupy the same crystallographic site in a crystal structure, however, their distribution is not random in nature as for a solid solution, but rather systematically alternating in manner.

[0111] Accordingly, in the context of this invention “one or more elements on A position in form of a solid solution or in an ordered arrangement” is to be understood as meaning that the compound has two or more types of category A-atoms that occupy the same crystallographic site in the structure in a random manner (solid solution) or in a systematic manner (ordered arrangement). In the context of the invention “rare earth” is to be understood as meaning a cation representing Sc, Y, La or the fourteen 4f-elements; i.e. elements with numbers 21 , 38, and 57 to 71 in the Periodic Table.

[0112] In the context of the invention “lanthanoids / rare earth elements” is to be understood as meaning that the respective “A” is selected from both the lanthanoids or rare earth elements as defined herein. Thus, in a preferred embodiment it encompasses or is selected from Ce, Pr, Nd, Pm, Sm, Eu, Gd, or La, Sc, or Y.

[0113] In the context of the invention “An+iBnO3n+i(n = 1 , 3) — Ruddlesden Popper phases is to be understood as described in the explanation given above for “RP-Phase”.

[0114] In the context of the invention “3-5d elements” is to be understood as meaning that 3-5d elements refer to 3d, 4d and 5d elements in the periodic table, altogether 10, 10 and 10 elements, respectively

[0115] In the context of the invention “p-block elements” is to be understood as meaning that p- block elements refer to the elements in groups 13, 14 and 15, in the periodic table.

[0116] The present invention is illustrated below with the aid of examples. These illustrations are given solely by way of example and do not limit the general spirit of the present invention.

[0117] EXAMPLES:

[0118] Example 1 :

[0119] CaO and Nd2Os were tested in a lab scale for Pt and Rh catchment at 700, 800 and 900°C.

[0120] A laboratory scale six-zone furnace (Entech Energiteknik AB, Sweden) was used in the Pt and Pt+Rh catchment experiments. All the experiments were run in dry air (< 300 ppm H2O) with a flow of approximately 450 mL / min in quartz tubes of inner diameter 4 mm, giving a similar linear gas velocity as in the ammonia oxidation process. Rolled up nets of Pt or Pt-Rh were placed upstream of the oxide rectangular pellets in a zone set to 1000 °C to yield PtC / RhC in the gas phase. The duration of the catchment experiments were in the range from 1 to 26 days, and 3 parallel experiments were run at the same time by placing the oxide pellets in 3 parallel tubes in 3 different zones of different temperatures: 700, 800 and 900 °C.

[0121] For results see Fig. 1 ) for CaO and 2) for Nd2Os.

[0122] The results seen on Fig. 1 ) for CaO are as follows:

[0123] - at 700°C the respective relations of the detected metals are: o 100% Ca

[0124] - at 800°C the respective relations of the detected metals are: o 98% Ca o 2% Pt

[0125] - at 900°C the respective relations of the detected metals are: o 96% Ca o 1% Pt o 3% Rh

[0126] The results seen on Fig. 2) for Nd2Os are as follows:

[0127] - at 700°C the respective relations of the detected metals are: o 100% Nd

[0128] - at 800°C the respective relations of the detected metals are: o 85% Nd o 14% Pt o 1% Rh

[0129] - at 900°C the respective relations of the detected metals are: o 65% Nd o 18% Pt o 17% Rh As can be seen there, the capture of both Pt and Rh was clearly improved in the Nd2O3 over the CaO.

[0130] The results further seem to indicate that rhodium catchment improves with the rise of the temperature being most effective at temperatures around 900°C or at least favored over Pt. To put these results to scale: if the wire contains 10wt% Rh, the atom % Rh in the wire is 20%; i.e., a 1 :1 correlation in Pt-Rh catchment relative to the Pt-Rh catalyst should then give a ratio of Pt / Rh = 80 / 20.

[0131] On the other hand, these results seem to point at that at 800 °C is overall good for Pt catchment but is alo very good and present at 900° C.

[0132] Example 2:

[0133] CaO Gd2Os and Nd20s were tested in a lab scale for Pt and Rh catchment at 700, 800 and 900°C.

[0134] A laboratory scale six-zone furnace (Entech Energiteknik AB, Sweden) was used in the Pt and Pt+Rh catchment experiments. All the experiments were run in dry air (< 300 ppm H2O) with a flow of approximately 450 mL / min in quartz tubes of inner diameter 4 mm, giving a similar linear gas velocity as in the ammonia oxidation process. Rolled up nets of Pt or Pt-Rh were placed upstream of the oxide rectangular pellets in a zone set to 1000 °C to yield PtC / RhC in the gas phase. The duration of the catchment experiments were in the range from 1 to 26 days, and 3 parallel experiments were run at the same time by placing the oxide pellets in 3 parallel tubes in 3 different zones of different temperatures: 700, 800 and 900 °C.

[0135] Results on Pt catchment from lab scale experiments at 700, 800 and 900°C are shown in Table 1. Table 1 shows a summary of EDX results and crystal structure from XRD of surfaces of pellets of catchment oxides after reaction with PtO2(g) at 700, 800 and 900°C for 26 days. The primary cation of each oxide is called A and EDX quantifications are given as Pt / (Pt+A) molar fraction.

[0136] Table 1 :

[0137] Example 3:

[0138] In a pilot plant CaO, GCI2O3 and Nd2Os were tested at 900 °C in a first round for 21 days and a second round for 12 days for their ability to capture Pt and Rh.

[0139] A) First round in pilot plant:

[0140] Nd2C>3, Gd2C>3 and CaO were exposed to the real process conditions based on the Ostwald process (T = 900 °C, P = 5 bar and gas mix of 10 % NOx, 15 % H2O, 5 % O2 and 1300 ppm N2O in N2) for 21 days. Cylindrical pellets of the oxides were sewn into megapyr nets for easier handling. The samples were placed at the top of raching rings in the gas stream after the Pt-Rh catalyst (95:5 wt.%)+Pd-Ni catchment gauze+Co-containing laughing gas.

[0141] The results as far as available are given below in Table 2. Some of the results for the other oxides are not available as the influx of Si was maybe too high due to a suspected weakness of the megapyr nets (which contain Si). Others are not finally analyzed, yet, while in some cases the oxide material got damaged.

[0142] TABLE 2:

[0143] Sum of Si, Co and Ni B) Second round in pilot plant

[0144] NCI2O3, CaO and Gd2Os were exposed to real process conditions (T = 900 °C, P = 5 bar and gas mix of 10 % NOx, 15 % H2O, 5 % O2 and 1300 ppm N2O in N2) for 21 days. Cylindrical pellets of the oxides were sewn into megapyr nets for easier handling. The samples were placed in the gas stream just after the Pt-Rh catalyst (95:5 wt.%) and before a laughing gas catalyst.

[0145] The results of said second round are given in Table 3 below:

[0146] TABLE 3: It can be seen in Table 2 and especially 3 that e.g. for Gd2C>3, where there was no Pt capture in lab scale in Example 2 (see Table 1 ), a more pronounced Pt capture is seen in the experiments of example 3 (which is in some aspects close to the industrial situation).

[0147] Example 4:

[0148] Lab scale experiments for a) combined Rh and Pt catchment and b) Pt (only) catchment were done in a similar set up as discussed for Examples 1 and 2 with Nd2Os at 700, 800 and 900°C. The results are shown in Fig. 3. These results seem to indicate that the catchment behavior appears to be different depending on if Pt is collected together with another element (as shown here with Rh) or not. In both cases there also seems to be a temperature influence with good results at 800°C and also above.

[0149] The results seen on Fig. 3a) (Pt-Rh; 10 wt:% Rh) are as follows:

[0150] - at 700°C the respective relations of the detected metals are: o 100% Nd

[0151] - at 800°C the respective relations of the detected metals are: o 85% Nd o 14% Pt o 1% Rh

[0152] - at 900°C the respective relations of the detected metals are: o 65% Nd o 18% Pt o 17% Rh

[0153] The results seen on Fig. 3b) (Pt only) are as follows:

[0154] - at 700°C the respective relations of the detected metals are: o 100% Nd

[0155] - at 800°C the respective relations of the detected metals are: o 74% Nd o 26% Pt

[0156] - at 900°C the respective relations of the detected metals are: o 92% Nd o 8% Pt

[0157] Again, the results seem to indicate that rhodium catchment improves with the rise of the temperature being most effective at temperatures around 900°C. To put the results of Fig. 3a) to scale: as the wire contains 10wt% Rh, the atom % Rh in the wire is 20%; i.e., a 1 :1 correlation in Pt-Rh catchment relative to the Pt-Rh catalyst should then give a ratio of Pt / Rh = 80 / 20.

[0158] These results seem to point at that at least at around 800 °C Pt catchment is good.

Claims

CLAIMS:1 . A process for the capture of at least one noble metal being selected from rhodium and platinum lost by volatilization from a catalyst comprising the at least one noble metal to a high heater gas stream contacted therewith in a high temperature gas reaction carried out at temperatures of at least 700°C, wherein the catalytic reaction of the high temperature gas reaction is a catalytic ammonia oxidation or catalytic ammonia combustion, which comprises contacting such highly heated gas stream, after its contact with such catalyst, which contains the volatilized at least one noble metal while such volatilized noble metal is still essentially in the vapor phase and at a temperature of at least 700 °C with a first oxide element comprising at least one oxide selected from- an oxide of formula A2O3 with A being selected from Nd and Gd.

2. The process according to claim 1 , wherein said oxide is selected from Nd20s and Gd2Os; most preferably wherein said oxide is Nd20s.

3. The process according to claims 1 or 2, wherein said highly heated gas stream in addition to contacting said first oxide element is further also contacting a metallic element comprising a metallic material selected from the group consisting of palladium, and palladium alloys, more specifically palladium-nickel alloys and palladium-gold alloys.

4. The process according to claim 3, wherein the contact with said metallic element precedes and / or is upstream from the contact with said first oxide element; or wherein the contact with said metallic element follows and / or is downstream from the contact with said first oxide element.

5. The process according to claims 1 to 4, whereinthere is no further oxide element, comprising metal oxides, and / or no N2O- decomposition catalyst used in the process; and / or the first oxide element comprises only one metal oxide.

6. The process according to claims 1 or 2, wherein the highly heated gas stream in addition to contacting said first oxide element is further also contacting a second oxide element comprising at least one further oxide being different from said at least one oxide, wherein said at least one further oxide is selected from- - an oxide of formula ABO3, especially in in perovskite form, with A being selected from alkaline earth and rare earth elements / lanthanoids, preferably with A being selected from La, Ce, Pr, Nd, Pm, Sm, Eu and Gd, Sr, Ca and Ba, and with B being selected from 3-5d elements, and p-block elements, preferably with B being selected from Ti, V, Cr, Mn, Fe, Co, Ni, Mg, Al, Ga; optionally with one or more elements on A position in form of a solid solution or in an ordered arrangement and / or optionally with one or more elements in B-position in form of a solid solution or in an ordered arrangement and / or optionally in its respective RP phases; or.- an oxide of formula A2O3 with A being selected from rare earth elements / lanthanoids, optionally with one or more elements on A position in form of a solid solution; preferably an oxide of formula A2O3 with A being selected from La, Ce, Pr, Nd, Pm, Sm, Eu and Gd; or from La, Nd, Pm, Sm, Eu and Gd; or from La, Ce, Pr, Nd, Pm, Sm, Eu and Gd;; preferably wherein the second oxide element comprises the at least one further oxide being LaNiOs.

7. The process according to claim 6, wherein the contact with said second oxide element precedes and / or is upstream from the contact with said first oxide element; or wherein the contact with said second oxide element follows and / or is downstream from the contact with said first oxide element.

8. The process according to any one of claims 1 to 7 , wherein the process serves for the capture of both rhodium and platinum lost by volatilization from a catalyst comprising rhodium and platinum to a high heater gas stream contacted therewith in a high temperature gas reaction carried out at temperatures of at least 700°C which comprises contacting such highly heated gas stream, after its contact with such catalyst, which contains thus volatilized rhodium and platinum while such volatilized rhodium and platinum is still essentially in the vapor phase and at a temperature of at least 700 °C with said first oxide element.

9. The process according to any one of claims 1 to 8, wherein the highly heated gas stream after its contact with said catalyst is contacted with said first oxide element at a temperature at around or above 800°C, preferably at around 900 °C or above, preferably wherein said high temperature gas reaction is carried out at temperatures of at around or above 800°C, preferably at around 900°C or above.

10. The process according to any one of claims 1 to 9, wherein the highly heated gas stream also contains N2O, which is decomposed / converted upon contact with said first oxide element, preferably wherein the N2O is decomposed / converted to NO, NOX, N2 and / or O2.

11. Use of an oxide element comprising at least one oxide selected from an oxide of formula A2O3 with A being selected from Nd and Gd, for the capture of at least one noble metal being selected from rhodium and platinum, especially from a highly heated gas stream at a temperature of at least 700 °C, which contains the volatilized at least one noble metal while such volatilized noble metal is still essentially in the vapor phase.

12. The use according to claim 11 , wherein the use is for the capture of rhodium and platinum; and / or wherein the use is for capture of rhodium and platinum, especially in the same process.

13. A device for the capture of at least one noble metal being selected from rhodium and platinum from a combustion furnace of the type having a noble metal gauze arranged across the furnace in a direction transverse to the flow of gas therethrough, said device being an oxide element comprising or consisting of at least one oxide selected from an oxide of formula A2O3 with A being selected from Nd and Gd.

14. A catchment device for the capture of at least one noble metal being selected from rhodium and platinum, in an ammonia oxidation reaction, comprising an oxide element comprising or consisting of at least one oxide selected from an oxide of formula A2O3 with A being selected from Nd and Gd.

15. The use according to claim 11 or 12, the device according to claim 13 or catchment device according to claim 14, wherein said oxide is selected from Nd2Os and Gd2Os; most preferably wherein said oxide is Nd20s.