(19)
(11)EP 2 948 242 B1

(12)EUROPEAN PATENT SPECIFICATION

(45)Mention of the grant of the patent:
29.08.2018 Bulletin 2018/35

(21)Application number: 14701218.1

(22)Date of filing:  24.01.2014
(51)International Patent Classification (IPC): 
B01J 23/00(2006.01)
C01B 21/26(2006.01)
(86)International application number:
PCT/EP2014/051427
(87)International publication number:
WO 2014/114764 (31.07.2014 Gazette  2014/31)

(54)

AN AMMONIA OXIDATION CATALYST FOR THE PRODUCTION OF NITRIC ACID BASED ON METAL DOPED YTTRIUM ORTHO COBALTATE

AMMONIAKOXIDATIONSKATALYSATOR ZUR HERSTELLUNG VON SALPETERSÄURE AUF DER BASIS VON METALLDOTIERTEM YTTRIUM-ORTHOKOBALTAT

CATALYSEUR D'OXYDATION DE L'AMMONIAC DESTINÉ À LA PRODUCTION D'ACIDE NITRIQUE BASÉ SUR UN ORTHO-COBALTATE D'YTTRIUM DOPÉ EN MÉTAL


(84)Designated Contracting States:
AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

(30)Priority: 28.01.2013 NO 20130145

(43)Date of publication of application:
02.12.2015 Bulletin 2015/49

(73)Proprietor: YARA International ASA
0213 Oslo (NO)

(72)Inventors:
  • WALLER, David
    3931 Porsgrunn (NO)
  • GRØNVOLD, Marianne Søbye
    3936 Porsgrunn (NO)
  • SAHLI, Nibal
    3743 Skien (NO)

(74)Representative: Onsagers AS 
P.O. Box 1813 Vika
0123 Oslo
0123 Oslo (NO)


(56)References cited: : 
EP-A1- 2 202 201
WO-A1-2009/054728
WO-A1-2006/010904
  
  • GINA PECCHI ET AL: "Catalytic performance in methane combustion of rare-earth perovskites RECoMnO(RE: La, Er, Y)", CATALYSIS TODAY, ELSEVIER, NL, vol. 172, no. 1, 14 February 2011 (2011-02-14), pages 111-117, XP028275045, ISSN: 0920-5861, DOI: 10.1016/J.CATTOD.2011.02.032 [retrieved on 2011-03-04] cited in the application
  
Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention).


Description

FIELD OF THE INVENTION



[0001] The present invention relates to a catalytically active component of a catalyst, which comprises single phase oxides, based on metal doped yttrium ortho-cobaltate, catalysts comprising the catalytically active component, methods for the oxidation of ammonia in the presence of said catalysts comprising said catalytically active component and the use thereof.

BACKGROUND OF THE INVENTION



[0002] Currently, nitric acid is produced industrially via the catalytic oxidation of ammonia, over a platinum or platinum alloy-based gauze catalyst. This process, known as the Ostwald process, has essentially remained unchanged, since its inception in the first decades of the twentieth century. Ostwalds's patent was dated 1902 and when combined with Haber's development of synthesising ammonia, in 1908, the basis for the commercial production of nitric acid, which is used today, was in place.

[0003] The combustion of ammonia is carried out over a platinum based metal or alloy catalyst in the form of a gauze or mesh or net. A number of gauzes are installed together, and they constitute the gauze pack. The upper-most gauzes have compositions optimised for the combustion of ammonia, and are referred to as the combustion gauzes. Gauzes with other compositions may be located below the combustion gauzes, and these may have other roles, as described below. The whole stack of gauzes is referred to as the gauze pack. The gauzes are produced either by weaving or knitting.

[0004] The operating temperatures of the plants are typically 830 to 930°C and the range of pressures is from 100 kPa to 1500 kPa. Typically, the combustion gauzes are installed in the plant for between six months and two years, depending on the plant operating conditions. Plants operating at high pressures typically have shorter campaigns than low-pressure plants.

[0005] The duration of the campaign is governed by a loss in the selectivity of the catalyst, towards the desired nitric oxide product, through the increased formation of unwanted nitrogen and nitrous oxide by-products. The loss of selectivity is related to a number of phenomena. During combustion, platinum is lost through the formation of PtO2 vapour. Some of the platinum may be recovered by the installation of palladium metal based gauzes, directly below the platinum based combustion gauzes. The PtO2 vapour alloys with the palladium, therefore, platinum is retained in the catalytically active zone. However, due to the depletion of platinum in the upper combustion zone of the gauze pack, not all of the ammonia is immediately combusted. If the ammonia is combusted in the palladium gauze region, the selectivity towards nitric oxide is reduced, and secondly, if ammonia and nitric oxide coexist in the vapour phase for a period of time, nitric oxide is reduced by ammonia, through a homogeneous reaction. This leads to both nitric oxide and ammonia losses. A final mechanism for loss of selectivity is related to the fact that the platinum is lost from the combustion gauzes at a higher rate than the other alloying elements (typically rhodium). This leads to rhodium enrichment of the gauze surface which leads to selectivity loss.

[0006] Over the last sixty years, many attempts have been made to replace the expensive platinum-based combustion catalyst with a lower cost catalysts, based for example on metal oxides. To date, the only commercially available oxide based catalyst for ammonia combustion, was developed by Incitec Ltd (Australia). This is based on a cobalt oxide phase. However, in terms of its selectivity of combustion of ammonia to the desired nitric oxide product, its performance is inferior to that of platinum-based systems. The cobalt oxide based systems have shown selectivity levels of circa 90%, in commercial units, compared to the 94 to 98% achieved with platinum based catalysts.

[0007] The use of mixed oxides with the perovskite structure, such as rhombohedral lanthanum cobaltate, as catalysts for ammonia oxidation, has received much attention. However, when considering the conditions that the catalyst is subjected to in industrial ammonia oxidation, it can clearly be seen that they are not suitable for stability reasons. Ammonia oxidation on an industrial scale, takes place at temperatures from 830 to 930°C and at pressures from 100 kPa to 1500 kPa. The concentration of ammonia is in the range of 8.5 to 12mol%, depending on plant conditions, with the remainder of the gas consisting of air. Thus the gas feed for oxidation has a composition of approximately 10mol% NH3, 18.7mol% O2 and the balance being nitrogen. When the ammonia is oxidised to NOx (NO + NO2), with an efficiency of 95%, the gas composition is approximated by 9.5% NOx, 6% O2 and 15% water vapour. (The balance of gas composition is nitrogen and some 800 to 2000 ppm of N2O). Thus the ammonia oxidation catalyst is subjected to high temperatures and a gas environment that contains oxygen and water vapour. These are the ideal conditions for the evaporation of metal ions, in the form of hydroxides and oxyhydroxides. Thus material will be lost from the catalytic reaction zone as vapour phase species, which will in turn be deposited downstream in a cooler zone of the reactor system.

[0008] If considering evaporation from mixed oxides (those that contain more than one metal component), it most often has an incongruent evaporation process. This is the situation where one component in the oxide has a higher evaporation rate than another or than the others. If considering the lanthanum cobaltate perovskite system, when heated in an atmosphere containing oxygen and water vapour, cobalt species, such as CoOOH, have much higher vapour pressures than the dominant lanthanum species La(OH)3. The effect of this is that cobalt evaporates to a larger extent than lanthanum, thus incongruent evaporation. The result of preferential cobalt evaporation is that in time, the non-stoichiometry limit of the lanthanum cobalt perovskite X will be exceeded (LaCo1-XO3 where X and 0 < X ≈ < 0.03). When the limit is exceeded, La2O3 will be precipitated. When operating, La2O3 does not have a negative effect on the catalyst performance. However, when the plant is shut-down or when it trips, the oxide catalyst is exposed to the ambient air. On cooling in air, the free La2O3 will hydrate; forming La(OH)3. 1 mole of La2O3 will form 2 moles of La(OH)3, which involves a 50% expansion of the volume of the free lanthanum species. This results in a mechanical disintegration of the catalyst.

[0009] Different perovskite type oxidation catalysts are known for use in different oxidation reactions. Examples of such catalysts and reactions are mentioned below.

[0010] Pecchi, G et al., "Catalytic performance in methane combustion of rare-earth perovskites RECo0,50Mn0,50O3 (RE: La, Er,, Y)", Catalysis today 172 (2011) page 111-117. This article describes physic-chemical properties for compounds where Co and Mn are present in equimolar quantities. The catalytic activity is related to methane combustion.

[0011] Russian patent RU2185237 describes catalysts for use in ammonia oxidation. The active catalyst is a composition with perovskite structure of the formula Mn1-x R1+xO3, wherein R= Y, La, Ce or Sm and X=0-0.596. A catalyst support of alumina is used. However, this patent describes a method of producing N2O, which is used in various areas as in semiconductors, perfume industries, in medicine and food industry. The catalysts show increased activity and selectivity for N2O and low selectivity for NO, which is the opposite of what is wanted for nitric acid production.

[0012] EP 532 024 relates to a catalyst for catalytic reduction of nitrogen oxide. More particularly, it relates to a catalyst for reduction of nitrogen oxide using a hydrocarbon and/or an oxygen-containing organic compound as a reducing agent, which is suitable for reducing and removing harmful nitrogen oxide present in emissions from factories, automobiles, etc. It is used a perovskite type compound oxide on a solid carrier. This catalyst selectively catalyses a reaction of nitrogen oxide with the reducing agent so that nitrogen oxide in emissions can be reduced efficiently without requiring a large quantity of the reducing agent.

[0013] WO 2009/054728 A1 discloses a catalyst for production of nitric oxide from ammonia and oxygen, wherein the catalyst comprises the composition A((n+1)-x)BxC(n(1-y))Dny0(3n+1)+d, where A is a lanthanide (La, Gd, Nd, Sm) or yttrium, B is an alkaline-earth cation (Ca, Sr or Ba), C is Fe and D is Cr, Mn, Ni, Ce, Ti, Co or Mg, wherein A, B, C and D are selected independent of each other, n is larger than 0, x is a number in the interval [<0 and 5] and y is a number in the interval [<0 and 5] and d is a number in the interval [-1 and 1].

[0014] WO 2006/010904 A1 discloses the oxidation of ammonia with a perovskite oxidation catalyst of formula ABO3 in which A comprises bismuth and/or one or more lanthanide metal cations excluding Lanthanum, such as Bi, Pr, Sm, Ce or Gd or mixtures thereof and B comprises one or more transition metal cations, such as Co, Fe, Mn, Cu, Cr, Ti or Ni or mixtures thereof.

[0015] EP 2202201 A1 discloses catalysts for ammonia oxidation having a perovskite structure of the ABO3 type, wherein A is a rare earth-element or an alkaline earth element or mixtures thereof and B is a transition metal element or mixtures thereof.

SUMMARY OF INVENTION



[0016] The object of the invention is to find an oxide system suitable to be used as oxidation catalyst. A further object is to find a catalyst especially for ammonia oxidation where problems with swelling of the catalyst are avoided. Still a further object is to find a catalyst with high selectivity towards NOx and giving low levels of the undesired N2O.

[0017] These and other objects of the invention are obtained by the oxide systems as described in the enclosed patent claims.

[0018] The present invention thus provides a catalyst for the oxidation of ammonia, with a refractory support phase and a catalytically active single phase oxide based on metal doped yttrium ortho-cobaltate oxide systems, with the general formula YCo1-XMXO3, where X has values between 1> X > 0, and M is iron, chromium, vanadium and titanium, aluminium or an alkaline earth metal or the oxide phases has the general formula YCo1-XMnxO3 where X has values between 0.5 > X > 0. Preferably X is greater than 0.1. In particular embodiments of the invention the catalytically active component has the formula YCo0.9Mn0.1O3, YCo0.8Mn0.2O3, YCo0.7Mn0.3O3, YCo0.5Mn0.5O3, YCo0.9Ti0.1O3 or YCo0.9Fe0.1O3.

[0019] The refractory support phase may be selected from the group consisting of cerium dioxide, zirconium dioxide, alumina, yttrium oxide, gadolinium oxide, and a mixed oxide of these refractory oxides, silicon carbide, and sodium zirconium phosphate type phases.

[0020] The invention also concerns the use of a catalyst comprising a catalytically active single phase oxide based on metal doped yttrium ortho-cobaltate oxide systems, with the general formula YCo1-XMXO3, where X has values between 1> X > 0 in the oxidation of ammonia in the Ostwald process wherein a gas blend comprising ammonia and oxygen is converted. Preferably the catalyst has a selectivity towards NOx (NO + NO2), exceeding 90%, and a selectivity towards N2O (< 0.05%).

[0021] Another embodiment of the invention concerns the use of a catalyst comprising stable, single phase oxides, based on a metal doped yttrium ortho-cobaltate oxide systems, with the general formula YCo1-XMXO3, where X has values between 1 > X > 0, and M is a metal including manganese, iron, chromium, vanadium and titanium, aluminium or a transition metal, or an alkaline earth metal for the selective oxidation of ammonia. Preferably the oxide phase has the general formula YCo1-XMnXO3 where 1 > X > 0 or is selected from YCo0.9Mn0.1O3, YCo 0.8Mn0.2O3, YCo0.7Mn0.3O3, YCo0.5Mn0.5O3, YCo0.9Ti0.1O3 or YCo0.9Fe0.1O3.

DETAILED DESCRIPTION OF THE INVENTION



[0022] The current invention is a catalyst especially for high temperature ammonia oxidation, which is resistant to the above hydration issues of lanthanum containing mixed oxides. An evaluation of the hydration resistance of large metal ions that may adopt a trivalent oxidation state shows that the following are candidates: Scandium, yttrium, gadolinium, terbium, dysprosium, holmium, erbium, ytterbium and lutetium.

[0023] Scandium is eliminated as it is too small to form an ortho cobaltate phase. Terbium, dysprosium, holmium, erbium, ytterbium and lutetium are suitable in terms of their ionic radii and hydration resistance, but they are very expensive. However, yttrium meets the set requirement in terms of ionic radii, when in the trivalent oxidation state and its hydration resistance.

[0024] Yttrium and cobalt, in a 1:1 mole ratio form a stable orthorhombic phase YCoO3 - yttrium ortho-cobaltate. When this mixed oxide phase is tested under industrially relevant ammonia oxidation conditions (a feed-stock containing 10% ammonia, 18% oxygen and a balance of inert gas or nitrogen, at a temperature of 900°C), it combusts ammonia to a mixture of NOx (NO + NO2), N2 and N2O. However, the selectivity towards the nitrogen containing oxides that are desired in the production of nitric acid (NOx) is lower than that obtained by platinum-based catalysts and is in the range of 91.3%. Examination of the YCoO3 phase prior to and after the ammonia oxidation test, using X-ray powder diffraction, shows clearly that there has been a reduction of the YCoO3 phase

        2YCoO3 → Y2O3 + 2CoO     (1)



[0025] It is known that the CoO phase demonstrates some activity towards ammonia oxidation, but the selectivity towards desired NOx products is low - high levels of N2 and N2O are produced.

[0026] Thermo-gravimetric analysis of the YCoO3, in air shows that the YCoO3 phase reduces according to equation 1, at a temperature of 970°C. When combusting ammonia at 900°C, as in industrial plants, the 900°C temperature is that of the product gas directly downstream of the catalyst. The temperature of the catalyst is significantly higher than the gas temperature. Therefore, pure YCoO3 is not sufficiently stable for use as an industrial ammonia oxidation catalyst.

[0027] From the literature, it is known that the yttrium ortho-ferrate phase YFeO3 and the yttrium ortho-manganate phase YMnO3, are stable in air, up to high temperatures (1500 and 1350°C, respectively). An approach to improve the stability of the yttrium ortho-cobaltate phase could be to replace a proportion of the cobalt with either iron or manganese (based on the fact that the pure iron and manganese yttrium phases are significantly higher in stability than the YCoO3 phase. Two series of doped yttrium ortho-cobaltate phases were prepared, YCo1-XMnXO3 and YCo1-XFeXO3. Thermo-gravimetric analysis of these two series of yttrium ortho-cobaltates demonstrated that both iron and manganese doping of the yttrium ortho-cobaltates, improved the stability of the phases. A surprising, and unexpected result, is that the manganese doping is more effective at stabilizing the yttrium ortho-cobaltates, than iron doping, given that the stability of the pure YFeO3 is much higher than the pure YMnO3.

[0028] Samples of the YCo1-XMnXO3 catalysts were tested for their catalytic performance towards ammonia oxidation, in a laboratory test reactor system. They were found to be active towards ammonia oxidation with a high selectivity towards the desired NOX product.
Table 1. Performance of YCo1-XMnXO3 orthocobaltomanganates, sintered at 900°C, towards ammonia oxidation.
SampleIgnition temperature °CSelectivity towards NOx %N2O emission ppm
YCoO3 271 91.3 50
YCo 0.9Mn0.1O3 264 95.4 22
YCo 0.8Mn0.2O3 248 95.5 22
YCo 0.7Mn0.3O3 273 96.9 23
YCo0.5Mn0.5O3 257 94.3 37
YMnO3 239 92.4 112
In the table the corresponding values for YCoO3 and YMnO3 are also included for comparison. These compounds do not form a part of the invention.

[0029] It is observed that manganese doped yttrium ortho-cobaltate (YCo1-X MnXO3) exhibit both high selectivity towards the desired NOx product, along with low levels of the powerful N2O greenhouse gas. The compounds YCo0.9Mn0.1O3, YCo0.8Mn0.2O3, YCo0.7Mn0.3O3 have especially low levels of N2O emission. X-ray powder diffraction analysis of the fresh and used manganese doped yttrium ortho-cobaltates show that these phases had not undergone a reduction towards:

        2YTmO3 → Y2O3 + 2TmO     (2)

Where Tm is an oxide of cobalt and/or manganese. Thus the doping of yttrium ortho-cobaltate with a reduction resistant dopand, such as manganese leads to high selectivity towards NOx and low levels of the undesired N2O, under industrially relevant oxidation conditions.
By adding a dopant like Mn, Fe, Ti or other transitions metals, the catalyst stability have increased. Samples of the YCo1-XMXO3 catalysts where M is Fe or Ti, were tested for their catalytic performance towards ammonia oxidation, in the laboratory test reactor system. (See Table 2). Corresponding results for YCoO3 is shown for comparison.
Table 2. Performance of YCo1-XFeXO3 and YCo1-XTiXO3 towards ammonia oxidation.
SampleIgnition temperature °CSelectivity towards NOx %N2O emission ppm
YCoO3 271 91.3 50
YCo0.9Fe0.1O3 245 93.6 31
YCo0.9Ti0.1O3 284 95.3 25


[0030] The catalysts may be prepared by co-precipitation, complexation, combustion synthesis, freeze-drying or solid-state routes, or by other state-of-the-art methods of producing mixed-metal oxides. The catalysts according to the present invention can be used to catalyse several reactions.

[0031] Examples of such uses are:
  1. I. The catalysts may be used as oxidation catalysts,
  2. II. as catalysts for the selective oxidation of ammonia
  3. III. as catalysts for the oxidation of hydrocarbons
  4. IV. as catalysts for the complete oxidation of hydrocarbons to CO2, in gas turbine power generation applications
  5. V. as catalysts for the complete oxidation of hydrocarbons to CO2, at temperatures below 600°C, for the abatement of hydrocarbon emissions from vehicle exhaust gases.



Claims

1. Catalyst for the oxidation of ammonia, with a refractory support phase and a catalytically active single phase oxide, characterized in that it comprises stable, single phase oxides, based on a metal doped yttrium ortho-cobaltate oxide system, with the general formula YCo1-XMXO3, where X has values between 1 > X > 0, and M is iron, chromium, vanadium, titanium, aluminium or an alkaline earth metal, or in that the single phase oxide has the general formula YCo1-XMnXO3 where 0.5 > X > 0.
 
2. Catalyst according to claim 1, characterized in that M is iron or titanium.
 
3. Catalyst according to claim 1 or 2, characterized in that the single phase oxide has the formula YCo0.9Mn0.1O3, YCo0.8Mn0.2O3, YCo0.7Mn0.3O3.
 
4. Catalyst according to claim 1 or 2, characterized in that the single phase oxide has the formula YCo0.9Ti0.1O3 or YCo0.9Fe0.1O3.
 
5. Catalyst according to claim 1 or 2, characterized in that the refractory support phase is selected from cerium dioxide, zirconium dioxide, alumina, yttrium oxide, gadolinium oxide, and a mixed oxide of these refractory oxides, silicon carbide, and sodium zirconium phosphate type phases.
 
6. The use of a catalyst comprising stable, single phase oxides, based on a metal doped yttrium ortho-cobaltate oxide system, with the general formula YCo1-X MXO3, where X has values between 1 > X > 0, and M is manganese, iron, chromium, vanadium, titanium, aluminium, a transition metal or an alkaline earth metal, for the selective oxidation of ammonia.
 
7. The use according to claim 6, wherein the single phase oxide has the general formula YCo1-XMnXO3 where 1 > X > 0.
 
8. The use according to claim 7, wherein the single phase oxide has the formula YCo0.9Mn0.1O3, YCo0.8Mn0.2O3, YCo0.7Mn0.3O3, YCo0.5Mn0.5O3, YCo0.9Ti0.1O3 or YCo0.9Fe0.1O3.
 
9. The use according to any of the claims 6 to 8, wherein the selective oxidation of ammonia is according to the Ostwald process and wherein a gas blend comprising ammonia and oxygen is converted in the presence of the catalyst.
 
10. The use according to claim 9, wherein the catalyst has a selectivity towards NOx (NO + NO2) exceeding 90%, and a selectivity towards N2O (< 0.05%).
 


Ansprüche

1. Katalysator zur Ammoniakoxidation mit einer hitzebeständigen Trägerphase und einem katalytisch aktiven einphasigen Oxid, dadurch gekennzeichnet, dass er stabile einphasige Oxide umfasst, die auf einem metalldotierten Yttriumorthocobaltat-Oxidsystem mit der allgemeinen Formel YCo1-XMXO3 basieren, wobei X Werte zwischen 1 > X > 0 annimmt und M Eisen, Chrom, Vanadium, Titan, Aluminium oder ein Erdalkalimetall ist, oder dass das einphasige Oxid die allgemeine Formel YCo1-XMXO3 aufweist, wobei 0,5 > X > 0 ist.
 
2. Katalysator gemäß Anspruch 1, dadurch gekennzeichnet, dass M Eisen oder Titan ist.
 
3. Katalysator gemäß Anspruch 1 oder 2, dadurch gekennzeichnet, dass das einphasige Oxid die Formel YCo0,9Mn0,1O3, YCo0,8Mn0,2O3, YCo0,7Mn0,3O3 aufweist.
 
4. Katalysator gemäß Anspruch 1 oder 2, dadurch gekennzeichnet, dass das Monophasenoxid die Formel YCo0,9Ti0,1O3 oder YCo0,9Fe0,1O3 aufweist.
 
5. Katalysator gemäß Anspruch 1 oder 2, dadurch gekennzeichnet, dass die hitzebeständige Trägerphase aus Ceriumdioxid, Zirkoniumdioxid, Alumina, Yttriumoxid, Gadolinumoxid und einem Mischoxid von diesen hitzebeständigen Oxiden, Siliciumcarbid und Phasen vom Natriumzirkoniumphosphat-Typ ausgewählt ist.
 
6. Verwendung eines Katalysators, der stabile, einphasige Oxide umfasst, die auf einem metalldotierten Yttriumorthocobaltat-Oxidsystem mit der allgemeinen Formel YCo1-XMXO3 basieren, wobei X Werte zwischen 1 > X > 0 annimmt und M Mangan, Eisen, Chrom, Vanadium, Titan, Aluminium, ein Übergangsmetall oder ein Erdalkalimetall ist, zur selektiven Ammoniakoxidation.
 
7. Verwendung gemäß Anspruch 6, wobei das einphasige Oxid die allgemeine Formel YCo1-XMXO3 aufweist, 1 > X > 0 ist.
 
8. Verwendung gemäß Anspruch 7, wobei das monophasige Oxid die Formel YCo0,9Mn0,1O3, YCo0,8Mn0,2O3, YCo0,7Mn0,3O3, YCo0,5Mn0,5O3, YCo0.9Ti0,1O3 oder YCo0,9Fe0,1O3 aufweist.
 
9. Verwendung gemäß einem der Ansprüche 6 bis 8, wobei die selektive Ammoniakoxidation nach dem Ostwald-Verfahren durchgeführt wird und wobei ein Gasgemisch, das Ammoniak und Sauerstoff umfasst, in der Anwesenheit des Katalysators umgesetzt wird.
 
10. Verwendung gemäß Anspruch 9, wobei der Katalysator eine Selektivität gegenüber NOx(NO + NO2) von über 90 % und eine Selektivität gegenüber N2O (< 0,05 %) aufweist.
 


Revendications

1. Catalyseur pour l'oxydation de l'ammoniac, comportant une phase de support réfractaire et un oxyde monophasique catalytiquement actif, caractérisé en ce qu'il comprend des oxydes monophasiques stables, sur la base d'un système oxyde d'ortho-cobaltate d'yttrium dopé en métal, répondant à la formule générale YCo1-XMXO3, où X a des valeurs entre 1 > X > 0, et M est du fer, du chrome, du vanadium, du titane, de l'aluminium ou un métal alcalino-terreux, ou en ce que l'oxyde monophasique répond à la formule générale YCo1-XMnXO3 où 0,5 > X > 0.
 
2. Catalyseur selon la revendication 1, caractérisé en ce que M est du fer ou du titane.
 
3. Catalyseur selon la revendication 1 ou 2, caractérisé en ce que l'oxyde monophasique répond à la formule YCo0,9Mn0,1O3, YCo0,8Mn0,2O3, YCo0,7Mn0,3O3.
 
4. Catalyseur selon la revendication 1 ou 2, caractérisé en ce que l'oxyde monophasique répond à la formule YCo0,9Ti0,1O3 ou YCo0,9Fe0,1O3.
 
5. Catalyseur selon la revendication 1 ou 2, caractérisé en ce que la phase de support réfractaire est choisie parmi le dioxyde de cérium, le dioxyde de zirconium, l'alumine, l'oxyde d'yttrium, l'oxyde de gadolinium, et un oxyde mixte de ces oxydes réfractaires, le carbure de silicium, et les phases de type phosphate de sodium et de zirconium.
 
6. Utilisation d'un catalyseur comprenant des oxydes monophasiques stables, sur la base d'un système oxyde d'ortho-cobaltate d'yttrium dopé en métal, répondant à la formule générale YCo1-XMXO3, où X a des valeurs entre 1 > X > 0, et M est du manganèse, du fer, du chrome, du vanadium, du titane, de l'aluminium, un métal de transition ou un métal alcalino-terreux, pour l'oxydation sélective de l'ammoniac.
 
7. Utilisation selon la revendication 6, dans laquelle l'oxyde monophasique répond à la formule générale YCO1-XMXO3 où 1 > X > 0.
 
8. Utilisation selon la revendication 7, dans laquelle l'oxyde monophasique répond à la formule YCo0,9Mn0,1O3, YCo0,8Mn0,2O3, YCo0,7Mn0,3O3, YCo0,5Mn0,5O3, YCo0,9Ti0,1O3 ou YCo0,9Fe0,1O3.
 
9. Utilisation selon l'une quelconque des revendications 6 à 8, dans laquelle l'oxydation sélective de l'ammoniac est selon le procédé d'Ostwald et dans laquelle un mélange de gaz comprenant de l'ammoniac et de l'oxygène est converti en présence du catalyseur.
 
10. Utilisation selon la revendication 9, dans laquelle le catalyseur présente une sélectivité vis-à-vis des NOx (NO + NO2) dépassant 90 %, et une sélectivité vis-à-vis du N2O (< 0,05 %).
 






Cited references

REFERENCES CITED IN THE DESCRIPTION



This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.

Patent documents cited in the description




Non-patent literature cited in the description