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
  • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
  • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
  • B01J23/89—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper combined with noble metals
  • B01J23/8926—Copper and noble metals
• • 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
  • B01D53/9436—Ammonia
• • 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
  • B01J29/08—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the faujasite type, e.g. type X or Y
  • B01J29/10—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the faujasite type, e.g. type X or Y containing iron group metals, noble metals or copper
  • B01J29/14—Iron group metals or copper
  • B01J29/146—Y-type faujasite
• • 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
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J35/00—Catalysts, in general, characterised by their form or physical properties
  • B01J35/50—Catalysts, in general, characterised by their form or physical properties characterised by their shape or configuration
  • B01J35/56—Foraminous structures having flow-through passages or channels, e.g. grids or three-dimensional monoliths
• • 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
  • B01J37/0215—Coating
• • 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
  • B01D2255/102—Platinum group metals
  • B01D2255/1021—Platinum
• • 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
  • B01D2255/20761—Copper
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2255/00—Catalysts
  • B01D2255/50—Zeolites
• • 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
  • B01J2229/00—Aspects of molecular sieve catalysts not covered by B01J29/00
  • B01J2229/30—After treatment, characterised by the means used
  • B01J2229/32—Reaction with silicon compounds, e.g. TEOS, siliconfluoride

Definitions

• the present invention relates to an ammonia oxidation catalyst and a system for treating slipped ammonia or waste ammonia using the same, and more particularly to an ammonia oxidation catalyst comprising either Cu-containing zeolite impregnated with platinum or Cu/Si-containing alumina impregnated with platinum, which has improved low-temperature activity of oxidizing ammonia generated in a mobile source or fixed source system and is used to inhibit the formation of nitrogen oxides caused by ammonia, as well as a system for the treatment of ammonia contained in vehicle exhaust gas, a chemical reactor system and an environmental device and system, which include said ammonia oxidation catalyst.
• Background Art
• NOx generated from systems is generally used in an ammonia preparation process, industrial processes that use ammonia as main raw material or subsidiary raw material, and the fields of multi-purpose boilers, engines, furnaces and vehicle engines.
• the SCR or selective non-catalytic reduction (SNCR) system is used to reduce the emission of nitrogen oxides from exhaust gas containing NOx, particulate matter and hydrogen carbon, which is discharged from chemical factories, boilers, engines, furnaces, and vehicle engines.
• reducing agent ammonia in a fixed source SCR system is injected into an exhaust gas stream in an exhaust gas treatment system in which an SCR reduction catalyst bed is disposed.
• the injected ammonia catalytically reduces a large amount of nitrogen oxide contained in the exhaust gas so as to convert the nitrogen oxide into water and nitrogen. Because the nitrogen oxide removal catalyst used in the SCR system is carefully treated and expensive, it is preferable to control the stoichiometry of exhaust gas/ammonia/catalyst reactions, but there is a problem of secondary contamination due to the slip of ammonia unreacted with NOx. Meanwhile, methods of using a urea or ammonia SCR catalyst to remove nitrogen oxides from the exhaust gas of lean burn engines have been studied, but the problem caused by ammonia slip in vehicles still remains as a problem to be solved, like the problem in the fixed source system.
• ammonia slip is defined as a phenomenon in which ammonia gas, which is injected for the purpose of reacting with nitrogen oxides contained in exhaust gas discharged from the fixed source or mobile source nitrogen oxide generator, does not participate in an NOx reduction reaction due to various causes, but rather is emitted to the external environment.
• slipped ammonia is defined to mean ammonia which is slipped and emitted to the external environment.
• the present invention relates to a catalyst composition, which is effectively used to oxidatively degrade either waste ammonia (NH ) emitted from the fixed source system or ammonia slipped from the fixed source SCR and SNCR systems and the mobile source SCR system into nitrogen (N ) and water (H O) under preferred temperature conditions and, at the same time, to minimize nitrogen oxides caused by side reactions, as well as a system for treating ammonia using the above catalyst composition.
• NH waste ammonia
• N nitrogen
• H O water
• the catalyst preparation method disclosed in said patent comprises the steps of: alloying the surface layer of a steel material, having an annular shape or honeycomb, with aluminum; subjecting the steel material having the alloy layer to aluminum dissolution using a solution capable of dissolving aluminum, thus making the steel material surface layer porous; oxidizing the steel material according to known processes to obtain a catalyst substrate; dipping the oxidized steel material in a chloroplatinate solution adjusted to weak alkalinity using barium hydroxide; and removing the treated catalyst substrate from the solution, followed by drying.
• a known exhaust treatment system for use in mobile sources such as diesel engines comprises: (a) an exhaust system through which exhaust gas flows; (b) a selective catalytic reduction catalyst placed in the exhaust system, the catalyst serving to catalyze the reduction of NOx into nitrogen by ammonia and adsorbing and desorbing ammonia during an engine cycle; (c) an ammonia source; (d) a means for supplying ammonia from the ammonia source to the catalyst; and (e) a means for intermittently supplying ammonia during the engine cycle.
• a system for treating slipped ammonia is not yet disclosed.
• a known fixed source system for the treatment of exhaust gas comprises: (a) a combustion chamber having no reducing agent-injection unit; (b) a waste heat boiler through which exhaust gas generated in the combustion chamber flows; (c) a dry, semi-dry or wet reaction column; (d) a bag filter; (e) an SCR exhaust treatment system including an ammonia-reducing agent supply unit and a catalyst column; and (f) a means for emitting exhaust gas.
• a system for treating slipped ammonia is not yet known.
• a known fixed source NSCR system for the treatment of exhaust gas comprises: (a) a combustion chamber equipped with a reducing agent-injection unit; (b) a waste heat boiler; (c) a reaction column; (d) a bag filter; and (e) a means for emitting exhaust gas.
• an ammonia treatment system for preventing ammonia, used as a reducing agent, from being emitted to the external environment is not yet known.
• the present invention aims to provide a system for treating slipped ammonia or waste ammonia generated in a mobile source or fixed source SCR reaction or NSCR reaction, or in ammonia-related processes. Disclosure of Invention Technical Problem
• Another object of the present invention is to provide an ammonia oxidation catalyst, which can inhibit nitrogen oxide formation caused by an ammonia oxidation reaction.
• Still another object of the present invention is to apply an ammonia oxidation catalyst having improved low-temperature activity in an exhaust treatment system.
• the ultimate object of the present invention is to provide an ammonia oxidation catalyst, which is used to minimize the formation of nitrogen oxides caused by slipped ammonia or waste ammonia generated from SCR or NSCR reaction or ammonia-related processes in an mobile source or fixed source system and to effectively remove ammonia under preferred temperature conditions, as well as a system for treating ammonia using the ammonia oxidation catalyst.
• the above objects can be accomplished by providing a catalyst composition comprising either Cu-containing zeolite impregnated with precious metal (platinum, palladium or rhodium) or Cu/Si-containing alumina impregnated with precious metal, as well as a system for treating ammonia, in which a monolithic ceramic or metal substrate having the composition supported thereon is disposed.
• the zeolite used in the present invention, is an aluminosilicate zeolite-based natural or synthetic zeolite and is selected from the group consisting of metallic or non- metallic ZSM5, zeolite Y, ⁇ Zeolite, ⁇ zeolite, and mordenite.
• the metallic zeolite is preferably Fe-zeolite, Cu-zeolite or Fe/Cu-zeolite, which are ion-exchanged with Fe or Cu.
• the Fe-zeolite may also be impregnated with Cu.
• the alumina, used in the present invention, is preferably ⁇ alumina, in which Cu and Si are included or impregnated.
• the precious metal (platinum, palladium or rhodium), used in the present invention, is impregnated in an amount of less than 1.0 wt%.
• Said catalyst composition may be coated on a catalyst substrate, and all measurement values with respect to the catalyst composition are based on weights after coating the composition on the substrate.
• Cu When Cu is impregnated into zeolite, Cu can be derived from the following copper compounds. Copper ions from the copper compounds can be divalent or trivalent, and examples of the copper compounds include copper nitrate, copper chloride, copper oxide, copper sulfate, copper oxalate, copper acetate, copper carbonate, copper hydroxide, ammonium copper chloride, ammonium copper hydroxide, ammonium copper phosphate and the like, preferred being copper nitrate or copper acetate. Copper is preferably impregnated in an amount of less than 10 wt% based on the total weight of the catalyst. If copper is impregnated in an amount higher than 10 wt%, no additional increase in the catalyst activity will be shown and no advantage in economical terms will be obtained.
• the deposition of the catalyst composition on the wall of the substrate made of, for example, monolithic ceramic material or silicon carbide material can be performed using any conventional method.
• the substrate can be impregnated with the catalyst composition.
• the catalyst composition can also be wash- coated on the substrate.
• the present invention relates to an ammonia oxidation catalyst composition
• an ammonia oxidation catalyst composition comprising either Cu-containing zeolite impregnated with platinum or Cu/ Si-containing alumina impregnated with platinum, and a system for treating ammonia using the same.
• the inventive catalyst composition has excellent low-temperature activity and can inhibit the formation of nitrogen oxides caused by an ammonia oxidation reaction.
• the inventive catalyst composition is used to inhibit the formation of nitrogen oxides caused by slipped ammonia or waste ammonia in a mobile source or fixed source SCR reaction or NSCR reaction, ammonia preparation processes or related processes.
• a substrate having said catalyst supported thereon is placed in the ammonia treatment system.
• FIGS. 1 and 2 show Cu-containing zeolite Y activity and NOx formation as a function of the content of Pt in the catalyst, respectively.
• A Cu/ zeolite Y
• B 0.3 wt% Pt-impregnated Cu/zeolite Y
• C 0.5 wt% Pt-impregnated Cu/ zeolite Y
• D 0.7 wt% Pt-impregnated Cu/zeolite Y.
• FIGS. 3 and 4 show Pt-impregnated Cu/Si-impregnated alumina activity and NOx formation, respectively.
• E 0.7 wt% Pt-impregnated alumina
• H 0.7 wt% Pt-impregnated Cu/ Alumina
• J 0.7 wt% Pt-impregnated Cu/Si alumina.
• FIGS. 5 and 6 show catalyst activity and NOx formation according to the kind of
• the present inventors evaluated the suitability of a Cu-containing zeolite catalyst composition and the effect of platinum content on the catalyst composition and, as a result, found that the Cu-containing zeolite alone had a possibility of acting as an ammonia oxidation (hereinafter, also referred to as "AO") catalyst, that the low- temperature activity of the catalyst was increased depending on the platinum content, and also that NOx formation was promoted in proportion to the increase in the platinum content.
• AO ammonia oxidation
• the present inventors examined whether alumina capable of substituting for the above-described zeolite was suitable for an AG catalyst composition, and evaluated the effect of Cu contents on the alumina catalyst composition. As a result, it was found that, when alumina was used as the catalyst support, it had AO activity, but was negative in terms of NOx formation, and an increase in the Cu content thereof led to a reduction in activity, but was advantageous in terms of NOx formation.
• the present inventors examined the suitability of alumina as an AG catalyst according to the content of Si in alumina and, as a result, found that an increase in the content of Si in alumina was advantageous in terms of the formation of NOx formation. Thus, it was found that, when the outlet temperature of NH is maintained at a constant level of about 250 0 C, the alumina catalyst could also be applied.
• test conditions were as follows: composition of injected gas: 350-390 ppm of NH , 30 ppm of NOx; 5.0% H O, 5.0% O , and a balance of N ; and space velocity: 40,000 1/h.
• FIGS. 1 and 2 show ammonia conversion and NOx formation, respectively.
• a conversion rate of 60% was achieved at about 300 0 C, suggesting that Cu-containing zeolite Y can be used as an AO catalyst at high temperatures.
• an increase in the platinum content thereof led to an improvement in the low-temperature activity thereof, but resulted in an increase in NOx formation.
• Cu-containing zeolite can be used alone as an AO catalyst, but needs to be impregnated with platinum in order to increase the low- temperature activity thereof.
• the present inventors evaluated an alumina impregnated with 0.7 wt% platinum, but containing no Cu, a Cu-containing alumina impregnated with 0.7 wt% platinum, and a Cu/Si-containing alumina impregnated with 0.7% platinum, in comparison with Cu-containing zeolite Y impregnated with 0.7 wt% platinum (see FIGS. 3 and 4).
• the presence of Cu in the catalyst led to a decrease in the low- temperature activity of the catalyst, but was advantageous in terms of the formation of NOx.
• a result similar to this catalyst was shown for the catalyst containing both Cu and Si.
• the Cu and Si-containing alumina support was disadvantageous for low- temperature activity compared to zeolite, but showed results similar to those of zeolite with respect to NOx formation.
• inventive catalyst can be supported on a metal or ceramic honeycomb and be used in an exhaust treatment system for the oxidation of unreacted ammonia contained in exhaust gas emitted from mobile internal combustion engines such as diesel engines and gasoline engines. Also, the inventive catalyst can be used in an exhaust gas treatment system in order to minimize the formation of nitrogen oxides caused by slipped ammonia or waste ammonia generated in an SCR or NSCR system and related processes, including ammonia preparation processes, and to effectively oxidize the ammonia.
• the inventive catalyst can be used in a mobile source system for the treatment of exhaust gas, such as a diesel engine, which comprises (a) an exhaust system through which exhaust gas flows, (b) a selective catalytic reduction catalyst serving to catalyze the reduction of NOx into nitrogen by ammonia and adsorbing and desorbing ammonia during an engine cycle, (c) an ammonia source, (d) a means for supplying ammonia from the ammonia source to said selective catalytic reduction catalyst, and (e) a means for intermittently supplying ammonia during the engine cycle, wherein an ammonia oxidation catalyst comprising either Cu-containing zeolite impregnated with platinum or Cu-containing alumina impregnated with platinum is supported on a monolithic metal or ceramic substrate and is disposed at a stage following the selective catalytic reduction catalyst.
• a selective catalytic reduction catalyst serving to catalyze the reduction of NOx into nitrogen by ammonia and adsorbing and desorbing ammonia during an engine cycle
• the inventive catalyst can be applied in a fixed source SCR system for the treatment of exhaust gas, which comprises (a) a combustion chamber having no reducing agent-injection unit, (b) a waste heat boiler through which exhaust gas generated in the combustion chamber flows, (c) a dry, semi-dry or wet reaction column, (d) a bag filter, (e) an SCR exhaust treatment system including an ammonia- reducing agent supply unit and a catalyst column, and (f) a means for emitting exhaust gas, wherein an ammonia oxidation catalyst comprising either Cu-containing zeolite impregnated with platinum or Cu-containing alumina impregnated with platinum is supported on a monolithic metal or ceramic substrate and is disposed at a stage following the catalyst column.
• a fixed source SCR system for the treatment of exhaust gas which comprises (a) a combustion chamber having no reducing agent-injection unit, (b) a waste heat boiler through which exhaust gas generated in the combustion chamber flows, (c) a dry, semi-dry or wet reaction column
• the inventive catalyst can be applied in a fixed source NSCR system for the treatment of exhaust gas, which comprises (a) a combustion chamber equipped with a reducing agent-injection unit, (b) a waste heat boiler, (c) a reaction column, (d) a bag filter, and (e) a means for emitting exhaust gas, wherein an ammonia oxidation catalyst comprising either Cu-containing zeolite impregnated with platinum or Cu- containing alumina impregnated with platinum is supported on a monolithic metal or ceramic substrate and is disposed at a stage following the combustion chamber.

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• 2005
  • 2005-11-07 EP EP05820593.1A patent/EP1904229A4/de not_active Withdrawn
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