WO2014169935A1 - Procédé et système de catalyseur pour la réduction sélective d'oxydes d'azote - Google Patents

Procédé et système de catalyseur pour la réduction sélective d'oxydes d'azote Download PDF

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Publication number
WO2014169935A1
WO2014169935A1 PCT/EP2013/057780 EP2013057780W WO2014169935A1 WO 2014169935 A1 WO2014169935 A1 WO 2014169935A1 EP 2013057780 W EP2013057780 W EP 2013057780W WO 2014169935 A1 WO2014169935 A1 WO 2014169935A1
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WO
WIPO (PCT)
Prior art keywords
catalyst
zeolite
ammonia
alumina
process according
Prior art date
Application number
PCT/EP2013/057780
Other languages
English (en)
Inventor
Pär L. GABRIELSSON
Sebastian FOGEL
Original Assignee
Haldor Topsøe A/S
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Haldor Topsøe A/S filed Critical Haldor Topsøe A/S
Priority to PCT/EP2013/057780 priority Critical patent/WO2014169935A1/fr
Publication of WO2014169935A1 publication Critical patent/WO2014169935A1/fr

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J29/00—Catalysts comprising molecular sieves
    • B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
    • B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
    • B01J29/70—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of types characterised by their specific structure not provided for in groups B01J29/08 - B01J29/65
    • B01J29/72—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of types characterised by their specific structure not provided for in groups B01J29/08 - B01J29/65 containing iron group metals, noble metals or copper
    • B01J29/76—Iron group metals or copper
    • B01J29/7615—Zeolite Beta
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
    • B01D53/86—Catalytic processes
    • B01D53/8621—Removing nitrogen compounds
    • B01D53/8625—Nitrogen oxides
    • B01D53/8628—Processes characterised by a specific catalyst
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
    • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
    • B01D53/9404—Removing only nitrogen compounds
    • B01D53/9409—Nitrogen oxides
    • B01D53/9413—Processes characterised by a specific catalyst
    • B01D53/9418—Processes characterised by a specific catalyst for removing nitrogen oxides by selective catalytic reduction [SCR] using a reducing agent in a lean exhaust gas
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/02—Impregnation, coating or precipitation
    • B01J37/024—Multiple impregnation or coating
    • B01J37/0244—Coatings comprising several layers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/02—Impregnation, coating or precipitation
    • B01J37/024—Multiple impregnation or coating
    • B01J37/0246—Coatings comprising a zeolite
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2251/00—Reactants
    • B01D2251/20—Reductants
    • B01D2251/202—Hydrogen
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2251/00—Reactants
    • B01D2251/20—Reductants
    • B01D2251/206—Ammonium compounds
    • B01D2251/2062—Ammonia
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2255/00—Catalysts
    • B01D2255/10—Noble metals or compounds thereof
    • B01D2255/104—Silver
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2255/00—Catalysts
    • B01D2255/20—Metals or compounds thereof
    • B01D2255/207—Transition metals
    • B01D2255/20738—Iron
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2255/00—Catalysts
    • B01D2255/50—Zeolites
    • B01D2255/502—Beta zeolites
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2255/00—Catalysts
    • B01D2255/90—Physical characteristics of catalysts
    • B01D2255/902—Multilayered catalyst
    • B01D2255/9022—Two layers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2257/00—Components to be removed
    • B01D2257/40—Nitrogen compounds
    • B01D2257/404—Nitrogen oxides other than dinitrogen oxide
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2258/00—Sources of waste gases
    • B01D2258/01—Engine exhaust gases
    • B01D2258/012—Diesel engines and lean burn gasoline engines
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
    • B01J23/48—Silver or gold
    • B01J23/50—Silver

Definitions

  • the present invention concerns a process and catalyst sys- tern for reduction of nitrogen oxides from exhaust gases using a reducing agent such as ammonia and urea.
  • a reducing agent such as ammonia and urea.
  • the invention relates to a catalyst system, comprising two or more sandwiched layers alternately comprising an iron-beta-zeolite (Fe-beta-zeolite) and silver supported on alumina (Ag/Al20 3 ) , both catalysts being active in reduc ⁇ tion of nitrogen oxides in presence of a reducing agent.
  • High SCR activity can be achieved over Cu-zeolite materials without taking advantage of the fast SCR reaction, however, Cu-zeolites are more prone to hydrothermal deactivation than Fe-zeolites, which limits their use in many applica ⁇ tions .
  • Layered exhaust gas cleaning catalysts are known in the art. These catalysts normally comprise one layer active for SCR with the other layer providing other functionality such as NO or N3 ⁇ 4 oxidation, NO x or N3 ⁇ 4 storage etc. It is previously known from US patent 8062617B2 that iron- beta-zeolite (Fe-beta-zeolite) and silver supported on alu ⁇ mina (Ag/Al 2 03) can be combined to give enhanced results, compared to the single catalysts. In that prior art Fe-BEA is placed upstream of Ag/Al 2 03, either as separate beds or coated at each end of a single monolithic substrate.
  • Ag/Al 2 03 active at low temperatures and Fe-BEA active at higher temperatures allows an even better performance com ⁇ pared to arranging these catalysts in a dual bed system as disclosed in US 8062617B2.
  • the invention provides a process for reducing nitrogen oxides to nitrogen in an ex- haust gas comprising passing the exhaust gas in the pres ⁇ ence of a reducing agent through a catalyst system compris ⁇ ing two or more sandwiched catalyst layers alternately com ⁇ prising an iron-beta-zeolite (Fe-beta-zeolite) and silver supported on alumina (Ag/Al 2 03) .
  • the reducing agent is selected from ammonia, urea, hydrogen, alkanes such as CeHi 4 , alkenes and mixtures thereof. More preferably, the reducing agent is a mixture of hydrogen and ammonia. Such reducing agents can also be used in combination with one or more of the below embodi ⁇ ments .
  • the molar ratio of NH 3 :3 ⁇ 4:NO in the gas is 1:0.3-3:1 and the reaction temperature is in the range 150-550°C.
  • Sulphur tolerance of the catalyst is important for a cata ⁇ lyst system that performs stable over the whole catalyst lifetime.
  • Ag/Al 2 0 3 with higher Ag loads then previously believed optimal (1 wt% Ag) will increase the sulphur tolerance significantly.
  • a higher Ag load than 1 wt% gives lower NO x conversion at temperatures above 200-250°C.
  • NO x conversion was 78% for 1 wt% Ag and 43 and 23% for 3 and 4 wt% Ag respectively for tested Ag on commercial alumina catalysts ( ⁇ -alumina, SASOL Nl, BET area 150 m2/g) .
  • the alumina in combination with one or more of the above or below embodiments, is a high BET area boehmite.
  • the increased BET area allows for loading of more Ag on the catalyst due to the overall increase of acid sites. Acid sites are believed needed for N3 ⁇ 4 adsorption necessary for the SCR reaction. More Ag allows an even more sulphur tolerant catalyst. More specifi ⁇ cally 4 wt% Ag is deemed optimal for this particular boehm ⁇ ite alumina.
  • the 4 wt% Ag boehmite alumina catalyst showed above 90% NO x conversion between and 215 and 315°C compared to between 225 and 300°C for the above mentioned 3 wt% Ag on commercial alumina catalyst.
  • the amount of silver in the silver catalyst is between 0.5 and 6 wt%. More preferably, the amount of silver is about 4 wt%.
  • the silver may be loaded by incipient-wetness impregnation.
  • the alumina is preferably a ⁇ -alumina, such as a commercial alumina from SASOL (SASOL Nl, BET surface area: 150 m2/g) .
  • the present invention provides additionally a catalyst sys ⁇ tem for use in the inventive method.
  • the catalyst system according to the invention comprises two or more sandwiched catalyst layers alternately compris- ing an iron-beta-zeolite (Fe-BEA-zeolite) catalyst and a silver supported on alumina (Ag/Al 2 0 3 ) catalyst.
  • Suitable amounts of silver supported on alumina in the (Ag/Al 2 0 3 ) catalyst are between 0.5 and 6 wt%, preferably about 4 wt%.
  • the alumina carrier employed in (Ag/Al 2 0 3 ) catalyst is in a specific embodiment a boehmite ( ⁇ -alumina) .
  • the Ag/Al 2 0 3 catalyst forms an outer layer and Fe-BEA-zeolite catalyst forms an inner layer.
  • the catalyst system is in particular useful in the treat ⁇ ment of exhaust gases from lean combustion engines, gas turbines and boilers, tough not limited to these uses.
  • Ammonia can be supplied in the form of ammonia or a urea solution.
  • ammonia When ammonia is supplied in pure form it can be stored as liquid ammonia in a pressurized tank or in solid form as a metal amine salt where the ammonia is liberated from the salt by e.g. heating or other means as for instance described in WO-A-07000170.
  • the ammonia is supplied from an ammonia storage media in the form of a solid metal amine out of which ammonia is liberated and the hydrogen is supplied by decomposing ammonia in an ammonia decomposition reactor.
  • the hydrogen may be supplied from a hydrogen storage tank or by reforming some of the fuel used in the combustion process, e.g. diesel.
  • the active catalyst components will for most applications be coated on a monolith substrate.
  • the monolith substrate can be based on extruded cordierite or corrugated struc ⁇ tures of metal or fibre materials.
  • the catalysts may also be coated separately on the particu ⁇ late filter in order to integrate the filter and SCR func ⁇ tionality.
  • Figure 1 shows an embodiment the catalyst system according to the invention in form of a sandwiched dual layer configuration and Figures 2-4 show the positive effect of the dual layer catalyst over the individual catalysts (same total amount of catalyst) .
  • the positive effect of the proposed invention becomes more pronounced when the 3 ⁇ 4 amount is reduced. This will allow a control strategy that dose less 3 ⁇ 4 at higher temperatures, lowering the cost associated to 3 ⁇ 4 while at the same time maintaining a high NO x conversion.
  • 1 wt% Fe-beta-zeolite catalyst is coated onto a cordierite monolith (400 cpsi) as the inner layer and 4 wt% Ag/Al 2 C>3 catalyst is coated as the outer layer in two layer sandwich layout (dual-layer) .
  • This is compared to a system compris ⁇ ing of two separate monoliths, one with the same Fe-beta zeolites catalyst and one with the same Ag/Al 2 03 catalyst The Ag/Al 2 03 catalyst monolith is placed upstream and the Fe-beta catalyst monolith is placed downstream (dual-bed) .
  • the total and individual catalyst amounts are comparable as well as total monolith volume to allow a comparison of H 2 assisted NH 3 -SCR NO x removal efficiency as well as need for H 2 dosing.
  • Reaction conditions GHSV 15000 h "1 , 240 ppm NO, 270 ppm NH 3 , 0-600 ppm H 2 , 12% 0 2 , 6% H 2 0, balance N 2 and Ar .
  • the temperature was allowed to reach steady-state at each temperature tested.
  • the test results obtained in the example are summarised in Figs. 2 to 4.
  • Fig. 5 shows the temperature dependency of NO x conversion for the two catalyst systems, dual-layer and dual-bed, at different levels of H 2 .
  • the two systems showed very similar ⁇ conversion when 600 and 250 ppm H 2 was supplied. When no H 2 was supplied the dual-layer system performed much better than the dual-bed system.
  • the results also showed that at temperatures between approx. 240 and 340°C it is sufficient to supply 250 ppm H 2 since no difference in NO x conversion could be seen when either 250 or 600 ppm H 2 was supplied. At temperatures above 340 °C almost the same NO x conversion could be reached without supplying H 2 as compared to supplying either 250 or 600 ppm H 2 for the dual- layer system.
  • the dual-layer system was superior in this comparison with a dual-bed system when it came to maintaining a high NO x conversion while at the same time keeping the H 2 consump- tion as low as possible.
  • 3 ⁇ 4 i.e. fuel penalty
  • the following 3 ⁇ 4 dosing strategy could be suggested for the dual-layer system: at temperatures below 240°C, 600 ppm H 2 will be dosed; between 240 and 340°C, 250 ppm 3 ⁇ 4 will be dosed and above 240°C no 3 ⁇ 4 will be dosed.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Environmental & Geological Engineering (AREA)
  • Organic Chemistry (AREA)
  • Materials Engineering (AREA)
  • Health & Medical Sciences (AREA)
  • Biomedical Technology (AREA)
  • Analytical Chemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Combustion & Propulsion (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Catalysts (AREA)
  • Exhaust Gas After Treatment (AREA)

Abstract

La présente invention concerne un procédé pour réduire des oxydes d'azote en azote dans un gaz d'échappement comprenant le passage du gaz d'échappement en présence d'un agent réducteur à travers un système de catalyseur comprenant deux couches de catalyseur en sandwich comprenant de façon alternée un catalyseur de fer-bêta-zéolite (Fe-bêta-zéolite) et un catalyseur d'argent sur support d'alumine (Ag/Al2O3) et un système de catalyseur pour utilisation dans le procédé.
PCT/EP2013/057780 2013-04-15 2013-04-15 Procédé et système de catalyseur pour la réduction sélective d'oxydes d'azote WO2014169935A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PCT/EP2013/057780 WO2014169935A1 (fr) 2013-04-15 2013-04-15 Procédé et système de catalyseur pour la réduction sélective d'oxydes d'azote

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/EP2013/057780 WO2014169935A1 (fr) 2013-04-15 2013-04-15 Procédé et système de catalyseur pour la réduction sélective d'oxydes d'azote

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109689204A (zh) * 2016-09-12 2019-04-26 株式会社科特拉 废气净化用催化剂和废气净化用催化剂的制造方法

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2007000170A1 (fr) 2005-06-29 2007-01-04 Amminex A/S Procédé et dispositif pour la fourniture sans danger et contrôlée d’ammoniac à partir d’un support de stockage d’ammoniac solide
US20100111796A1 (en) * 2008-11-03 2010-05-06 Basf Catalysts Llc Integrated SCR and AMOX Catalyst Systems
US20110070134A1 (en) * 2009-09-24 2011-03-24 Alexandr Stakhev PROCESS AND CATALYST SYSTEM FOR SCR OF NOx

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2007000170A1 (fr) 2005-06-29 2007-01-04 Amminex A/S Procédé et dispositif pour la fourniture sans danger et contrôlée d’ammoniac à partir d’un support de stockage d’ammoniac solide
US20100111796A1 (en) * 2008-11-03 2010-05-06 Basf Catalysts Llc Integrated SCR and AMOX Catalyst Systems
US20110070134A1 (en) * 2009-09-24 2011-03-24 Alexandr Stakhev PROCESS AND CATALYST SYSTEM FOR SCR OF NOx
US8062617B2 (en) 2009-09-24 2011-11-22 Haldor Topsøe A/S Process and catalyst system for SCR of NOx

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN109689204A (zh) * 2016-09-12 2019-04-26 株式会社科特拉 废气净化用催化剂和废气净化用催化剂的制造方法
US11311859B2 (en) 2016-09-12 2022-04-26 Cataler Corporation Exhaust gas purification catalyst and method for manufacturing exhaust gas purification catalyst
CN109689204B (zh) * 2016-09-12 2022-06-24 株式会社科特拉 废气净化用催化剂和废气净化用催化剂的制造方法

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