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`Europaisches Patentamt
`European Patent Office
`Office europeen des brevets
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`E P 0 5 0 8 0 2 0 B 1
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`EUROPEAN PATENT SPECIFICATION
`
`ation and mention
`(45) Date of publication and mention
`of the grant of the patent:
`24.07.1996 Bulletin 1996/30
`
`(21) Application number: 91400974.1
`
`(22) Date of filing: 11.04.1991
`
`(54) Denitration catalyst and method
`Entstickungskatalysator und Methode
`Catalyseur et methode de denitration
`
`(84) Designated Contracting States:
`AT BE DE ES FR IT
`
`(43) Date of publication of application:
`14.10.1992 Bulletin 1992/42
`
`(73) Proprietor: MITSUBISHI JUKOGYO KABUSHIKI
`KAISHA
`Tokyo (JP)
`
`(72) Inventors:
`• Morii, Atsusi,
`c/o Nagasaki Shipyard & Eng. Works
`Nagasaki, Nagasaki Pref. (JP)
`• Kobayashi, Norihisa,
`c/o MITSUBISHI JUKOGYO K.K.
`Tokyo (JP)
`
`(51) |nt. CI.6: B01 D 53/56, B01 D 53/86
`
`• Izumi, Jun,
`c/o Nagasaki Technical Institute
`Nagasaki, Nagasaki Pref. (JP)
`• Yasutake, Akinori,
`c/o Nagasaki Technical Instit.
`Nagasaki, Nagasaki Pref. (JP)
`
`(74) Representative: Keib, Gerard et al
`Cabinet Claude Rodhain SA
`3, rue Moncey
`75009 Paris (FR)
`
`(56) References cited:
`EP-A-0 311 066
`EP-A-0 393 917
`
`EP-A- 0 393 905
`DE-A- 3 802 871
`
`Remarks:
`The file contains technical information submitted
`after the application was filed and not included in
`this specification
`
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`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).
`
`Printed by Rank Xerox (UK) Business Services
`2.13.0/3.4
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`1
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`JM 1033
`Johnson Matthey v BASF
`IPR2015-01267
`
`

`
`Description
`
`EP 0 508 020 B1
`
`The present invention relates to a method of removing NOx present in exhaust gases from combustors, such as
`boilers, gas turbines, gasoline engines, diesel engines and waste incinerators.
`The release of NOx, which is present in exhaust gases from combustors and causes air pollution, is now under
`strict regulations. A variety of improvements in combustion processes have been devised, and denitration apparatuses
`have widely been used. As examples of improvement in a combustion process, the lowering of the temperature of a fur-
`nace and the utilization of the reducing property of fire have been employed because NOx is produced by the dissoci-
`ation of N2 and 02 or by the reaction between nitrogen in the fuel and 02 in the furnace at high temperatures. These
`10 methods have certain limitations in the extent of NOx reduction. A common method adopted in fixed NOx sources such
`as a boiler, therefore, is to add ammonia to the exhaust gas in an amount approximately equal to the amount of NOx in
`the exhaust gas at 300-400°C and bring the mixture in contact with a NOx reducing catalyst so that NOx is converted
`to N2 and H20.
`The methods of improving combustion mentioned above have limitations in NOx reduction, and denitration using
`ammonia and a reducing catalyst would likely be a popular method for the moment. It is vanadium pentoxide carried on
`a carrier of titanium oxide that is considered to be most active among catalysts used in this method. This catalyst of
`vanadium-titania type has been most widely used. Although this vanadium-titania catalyst has an advantage of being
`less prone to be poisoned by a high concentration of sulfur components which is often found in, for example, an exhaust
`gas from a coal fired boiler, it has the following problems:
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`(1) A vanadium-titania catalyst shows a SV value of about 30,000 (h"1). Because if the value of SV is greater (which
`means higher catalytic activity), further reductions in fixed costs could be achieved owing to reduction in the amount
`of the catalyst used, and the power consumption could be also reduced due to smaller pressure losses in a catalyst
`layer, a catalyst with even higher activity is still strongly desired.
`(2) The reduction property of vanadium carried in the vanadium-titania catalyst is poisoned by alkali metals, such
`as potassium, present in an exhaust gas.
`(3) Titanium oxide used as a carrier is increasingly in demand as an ingredient for expensive metal materials and
`also as a white pigment for plastics and inks. Its price has trended upward and a cheaper substitute has been
`desired.
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`35
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`EP-A-0 393 917 discloses a method for reduction of nitrogen oxides comprising passing a gaseous stream con-
`tainig nitrogen oxides, amonia and oxygen through a zeolite catalyst to selectively catalyse the reduction of nitrogen
`oxides. The method disclosed in this document includes the use of a zeolite catalyst which comprises a metal (e.g. iron
`or copper) promoted Na-Y zeolite.
`EP-A-0 31 1 066 discloses a process for the production of copper-containing zeolite comprising subjecting a zeolite
`to ion exchange with copper ions in a aqueous solution containing a water soluble copper salt and ammonia. This pat-
`ent application describes equally a process for catalytic decomposition of nitrogen oxides contained in a gas, compris-
`ing bringing said gas into contact with said copper-containing zeolite.
`An object of the present invention is, in view of the above described state of art, to provide a method for removing
`40 NOx which can overcome the above described problems.
`The inventors have experimentally confirmed that if the NOx containing gas to which ammonia has been added in
`an amount at least equivalent to the molar amount of NOx is brought into contact with a Cu (II) exchanged Y zeolite
`which has been exchanged with Cu(ll) ions 60 to 200%, much higher activity can be achieved at a temperature between
`300 and 750°C, compared to the widely used vanadium-titania catalyst. The present invention has been based on this
`experimental finding.
`The denitration catalyst according to the present invention comprising a Cu (II) exchanged Y zeolite usable in a
`denitration process of a gas containing NOx using ammonia and said catalyst, wherein said catalyst is produced by
`exchanging 60 to 200% of exchangeable Na ions in a Na-Y zeolite with Cu (II) ions. The denitration method according
`to the present invention is defined in claim 2.
`Also, it is possible to add ammonia to the exhaust gas, at a temperature of 300 to 750°C, and pass it through the
`above-described catalyst reactor.
`According to the present invention, ammonia is added to a combustion exhaust gas containing NOx in a molar
`amount substantially equal to or more than the amount of NOx in the exhaust gas, and then the gas is led to a catalyst
`reactor filled with the Cu(ll) exchanged Y zeolite at 300-750°C. NOx then reacts with coexisting ammonia and oxygen
`and converts to nitrogen and water.
`The Cu(ll) exchanged Y zeolite used in the present invention can be obtained by exchanging Na ion positions in an
`Na faujasite (mineral name) whose ratio of silica to alumina (Si02/AI02 ratio) is 5 or more with Cu(ll) ions.
`When an Na-Y zeolite is immersed and stirred in a Cu(ll) ion solution, Na is exchanged by Cu(ll). If the exchange
`ratio of Cu(ll) is small, no particular differences are observed compared to the Na-Y zeolite. However, the exchange
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`so
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`EP 0 508 020 B1
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`ratio exceeds 30%, special activity particular to Cu(ll) exchange is observed. Here, the ratio of Cu(ll) exchange is
`defined as follows:
`
`Cu(ll) exchange ratio = (m°ls of Cu(ll) in zeolite after treatment) X 2 x
`(mols of Na in zeolite before treatment)
`Although it had previously been noted that the exchange with Cu(ll) is limited to 60%, it is now known that this
`limitation can be overcome by the following procedure:
`
`(1) The process for ion exchange is automated to repeat the renewal of solutions.
`(2) The exchange of Na ions is carried out using a Cu(ll)-ammonia complex. (Professor Masakazu Iwamoto of
`Hokkaido University reported this method for Cu(ll) exchange in Shokubai. Vol.31, No.2, 1989.)
`
`The definition of the ion exchange ratio, as noted above, is expressed as the percentage of "exchanged" ions with
`respect to cations (normally Na+ ions) which can be exchanged in the zeolite. For Cu(ll), however, the exchange ratio
`can in fact be more than 1 00% when calculated according to the above definition. Here, we show values calculated by
`this conventional definition for the sake of unity.
`It should be noted that a Y zeolite which is highly exchanged with Cu(ll) shows much higher activity than the con-
`ventionally employed vanadium-titania catalyst. This is not disclosed by the above reference.
`
`FIG. 1 is a chart showing flow for an embodiment of the present invention; and
`FIGS. 2 and 3 are graphs indicating the effects of present invention: FIG. 2 shows relations between the tempera-
`ture of the catalyst reactor and the denitration ratio; and FIG. 3 shows relations between the Cu(ll) exchange ratio
`and the denitration ratio.
`
`Referring to FIG. 1 , an embodiment of the present invention will be explained below.
`A combustor 1 used fuel oil A, and the concentration of NOx in the exhaust gas was 500ppm. The combustor 1 was
`provided with a heat exchanger 2 so that the temperature can be varied from 250°C to 1000°C. Numeral 3 indicates a
`container for liquified ammonia, and gasified ammonia was accompanied by steam and flowed through a flow passage
`4a. From the flow passage 4a, the gasified ammonia which had been adjusted to 500ppm, a mole equivalent of NOx in
`the exhaust gas, was connected to an exhaust gas passage 4b and mixed into the exhaust gas which had been cooled
`down.
`A gas mixture of NOx and ammonia passed through catalyst layers 6 filled with a catalyst 5 and reacted with oxy-
`gen present in the exhaust gas at a concentration of 4 volume % so that the mixture converts to nitrogen and water.
`Here we shall explain the preparation of the Cu(ll) exchanged Y zeolite.
`Two methods exist for the preparation of the Cu(ll) exchange, and we shall describe both here, but as long as the
`Cu(ll) exchange ratio reaches 60 to 200%, either of these methods will achieve the same performance.
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`[Method 1]
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`After a crystal powder of an Na-Y zeolite is left open overnight so that it can absorb moisture, a slurry is made from
`this powder and water, and its pH value is adjusted to 4 using acetic acid. When copper (II) acetate (Cu(ll)(CH3COO)2)
`is dropped into this slurry, Na ions are exchanged by Cu(ll) and the Cu(ll) exchanged zeolite is obtained.
`If the Cu(ll) concentration in the mother liquor exceeds 0.1 M, excessive absorption occurs and CuO separates out
`by burning or the like which will be described later. Therefore the concentration should preferably kept under the above
`45 value. However, separated CuO does not participate in reactions. Most of Cu(ll) absorbed excessively will remain
`bound to the zeolite and show considerable reaction activity.
`Cu(ll) ion exchange at one time is only about 20% in the exchange ratio. The filtration and renewal of the mother
`liquor have to be repeated a number of times before an exchange ratio of 60-200% can be achieved.
`Although Cu(ll) "exchange" of more than 100% cannot possibly take place according to the above definition of the
`exchange ratio, more than 100% of Cu(ll) is in fact carried without separating from the zeolite.
`Because the carrying of Cu(ll) on a carrier is basically accomplished by ion exchange, values exceeding 100% are
`also expressed as the exchange ratio (mol %) defined above.
`
`so
`
`[Method 2]
`
`After a crystal powder of an Na-Y zeolite is left open overnight so that it can absorb moisture, a slurry is made from
`this powder and water, and its pH value is adjusted to 7 using acetic acid or ammonia.
`When a copper (ll)-ammonia complex salt solution which has been prepared separately is dropped into this slurry,
`Na ions in the zeolite are exchanged with Cu(ll)-ammonia complex ions, and the Cu(ll) exchanged Y zeolite results.
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`EP 0 508 020 B1
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`Cu(ll) ion exchange for one time is only about 50% in the exchange ratio. The filtration and renewal of the mother
`liquor have to be repeated a number of times before the exchange ratio reaches 60-200%.
`This method is advantageous in that the Cu(ll) ion exchange ratio is higher compared to the method described
`above.
`The Cu(l I) exchanged Y zeolite obtained by a process such as the above two methods was filtered and washed with
`water, and subsequently formed by extrusion molding. It was then dried preliminarily at 120°C and baked at 650°C for
`1 hour to prepare a honeycomb catalyst 5 with a pitch of 4mm and a thickness of 1 mm.
`The gas which has finished the reaction was released out of the system through the passage 7, and a part of the
`gas was branched and collected through a sampling passage 8 for analysis.
`Also, a chemiluminescence analyzer 9 was used for the analysis of NOx.
`In order to compare the effects of the present invention with conventional examples, the following were used as ref-
`erence: (1) a vanadium-titania catalyst which has been widely used and (2) ZSM-5 zeolites with varying values of the
`Cu(ll) exchange ratio between 0 and 200%.
`In order to confirm the effects of the embodiment shown in FIG. 1 , an experiment was carried out with the entrance
`15 NOx concentration being 2000ppm and the 02 concentration being 4 volume % and the NH3/NOx mole ratio being 1 .0
`at temperatures between 250 and 800°C.
`FIG. 2 shows the relation between the temperature of the Cu(ll) exchanged Y zeolite and the percentage of deni-
`tration.
`In FIG. 2, the Cu(ll) exchanged Y zeolite with a Cu(ll) exchange ratio of 150% is indicated by an annular symbol
`20 @ , Cu(ll) exchanged ZSM-5 zeolite with the Cu(ll) exchange ratio of 150% shown as reference by a circular symbol
`0. and the vanadium-titania catalyst by a black circular symbol •.
`As seen from FIG. 2, the percentage of denitration of the Cu(ll) exchanged Y zeolite increased rapidly around
`300°C and reached a maximum at 400°C. While the denitration percentage reduced gradually as the temperature
`became higher, it remained in a practical range up to 750°C. The reaction activity was shown to be higher than the
`25 vanadium-titania catalyst in the broad range of temperature.
`However, when the temperature reached 800°C the reaction stopped altogether. At the same time, the conversion
`of NH3 to NOx and the thermal degradation of the zeolites began, and no practicality can be found.
`Also, although high activity was expected for the ZSM-5 zeolite because of its high acid strength, thermal stability,
`resistance against acidity and the like, it turned out that the vanadium-titania catalyst, which is used currently, actually
`30 has higher activity.
`FIG. 3 shows the relation between the Cu(ll) exchange ratio and the denitration percentage when the temperature
`of the reactor is 400°C. The activity of the vanadium-titania catalyst is shown with a broken line for reference.
`When the exchange ratio was 40% or less, the Cu(ll) exchanged Y zeolite (marked by ©) showed little activity.
`When it exceeded 40% the denitration ratio increased rapidly and exceeded the activity level of the vanadium-titania
`catalyst at 60%. However, when the exchange ratio exceeded 1 80% the denitration percentage started decreasing
`gradually and became lower than that of the vanadium-titania catalyst over 200%. This is probably because separated
`CuO which increased in amount covered active spots of the catalyst.
`With the Cu(ll) exchanged ZSM-5 zeolite, when the Cu(ll) exchange ratio was 40% the denitration ratio was higher
`than the Cu(ll) exchanged Y zeolite. The increase of the denitration with the increasing Cu(ll) exchanged ratio was not
`significant, and the denitration ratio did not exceed that of the conventional vanadium-titania catalyst.
`Using the Cu(ll) exchanged Y zeolite of the present invention for the purification of combustion exhaust gases, it is
`possible to carry out denitration at higher efficiency than a conventional vanadium-titania catalyst.
`
`35
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`40
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`45
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`Claims
`
`1. Denitration catalyst comprising a Cu (II) exchanged Y zeolite usable in a denitration process of a gas containing
`NOx using ammonia and said catalyst, characterised in that said catalyst is produced by exchanging 60 to 200 %
`of exchangeable Na ions in a Na-Y zeolite with Cu (II) ions.
`
`so 2. A denitration method for a gas containing NOx, using a catalyst and ammonia added in an amount at least equiv-
`alent to the molar amount of NOx and in presence of oxygen, said catalyst comprising a Cu (II) exchanged Y zeo-
`lite, wherein said gas containing NOx is passed at a temperature between 300 and 750°C through a catalyst
`reactor filled with a catalyst comprising a Cu(ll) exchanged Y zeolite, characterised in that said zeolite is produced
`by exchanging 60 to 200 % of exchangeable Na ions in a Na-Y zeolite with Cu(ll) ions by way of repeated renewal
`of solutions and by using a Cu(ll)-ammonia or Cu(ll)-acetic acid complex.
`
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`3. Denitration method according to claim 2, characterized in that ammonia is added to said gas containig NOx at tem-
`peratures of 300 to 750°C.
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`Patentanspriiche
`
`EP 0 508 020 B1
`
`1. Entstickungskatalysator mit einem Cu(ll) ausgetauschten Y Zeolithen zur Verwendung in einem Entstickungsver-
`fahren fur NOx haltiges Gas unter Verwendung von Ammoniak und des Katalysators, dadurch gekennzeichnet,
`daB der Katalysator durch Austauschen von 60 bis 200% der austauschbaren Na lonen in einem Na-Y Zeolithen
`gegen Cu(ll) lonen hergestellt worden ist.
`
`2. Entstickungsverfahren fur ein NOx enthaltendes Gas unter Verwendung eines Katalysators und Ammoniak, das in
`einer Menge zugegeben wird, die zumindest gleich der Molarmenge von NOx ist, sowie in Gegenwart von Sauer-
`stoff, wobei der Katalysator einen Cu(ll) ausgetauschten Y Zeolithen enthalt und wobei das NOx enthaltende Gas
`bei einer Temperatur zwischen 300 und 750°C durch einen Katalysatorreaktor geleitet wird, der mit einem Kataly-
`sator gefullt ist, der einen Cu(ll) ausgetauschten Y Zeolithen enthalt, dadurch gekennzeichnet, daB der Zeolith
`durch Austauschen von 60 bis 200% von austauschfahigen Na lonen in einem Na-Y Zeolithen gegen Cu(ll) lonen
`bei wiederholtem Erneuern von Losungen und Verwendung eines Cu(ll)-Ammoniak-oder Cu(ll)-Essigsauerekom-
`plexes gebildet wird.
`
`3. Entstickungsverfahren nach Anspruch 2, dadurch gekennzeichnet, daB Ammoniak dem NOx enthaltenden Gas
`bei Temperaturen von 300 bis 750°C zugegeben wird.
`
`Revendications
`
`1 . Catalyseur de denitration comprenant une zeolite Y echangee par Cu (II), utilisable dans un traitement de denitra-
`tion d'un gaz contenant NOx en utilisant de I'ammoniac et ledit catalyseur, caracterise en ce que ledit catalyseur
`est produit en echangeant 60 a 200 % des ions Na echangeables dans une zeolite Na-Y avec des ions Cu (II).
`
`2. Procede de denitration pour un gaz contenant NOx, utilisant un catalyseur et de I'ammoniac ajoute en une quantite
`au moins equivalente a la quantite molaire de NOx et en presence d'oxygene, ledit catalyseur comprenant une zeo-
`lite Y echangee par Cu (II), dans lequel on fait passer ledit gaz contenant NOx a une temperature entre 300 et 750
`°C au travers d'un reacteur de catalyseur rempli d'un catalyseur comprenant une zeolite Y echangee par Cu (II),
`caracterise en ce que ladite zeolite est produite en echangeant 60 a 200 % des ions Na echangeables dans une
`zeolite Na-Y avec des ions Cu (II) au moyen d'un renouvellement repete de solutions et en utilisant un complexe
`Cu(ll)-ammoniac ou Cu(ll)-acide acetique.
`
`3. Procede de denitration selon la revendication 2, caracterise en ce que I'ammoniac est ajoute audit gaz contenant
`NOx a des temperatures de 300 a 750 °C.
`
`

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`EP 0 508 020 B1
`EP 0 508 020 B1
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