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
  • 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 [3D] 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
  • B01J37/0201—Impregnation

Definitions

• the invention relates to a method for producing a plate-shaped carrier of catalytically active compounds by degreasing or pickling a profiled, full-surface or lattice-shaped metallic basic structure with subsequent application of an enamel coating.
• the object of the invention is to provide plate-like supports with a coating of catalytically active compounds, regardless of a specific shape, and in particular to achieve a coating that is uniform over the entire surface.
• the method according to the invention is characterized in that an enamel, a low-pore sub-layer and a rough top layer of high enamel is placed on the metallic basic structure
• Acid resistance is formed, applied and baked on its surface as a base enamel and further that the base structure coated with the base enamel follows the fire initially with a catalyst slip, which liquefies under the influence of shear forces, from a powder of compounds having a catalytic action, a binder, Water and, if necessary, wetting agents by swap into a moving catalyst slip bath and the wetted backbone is removed from the bath while maintaining the movement of the slip bath and then fed to drying.
• a catalyst slip which liquefies under the influence of shear forces, from a powder of compounds having a catalytic action, a binder, Water and, if necessary, wetting agents by swap into a moving catalyst slip bath and the wetted backbone is removed from the bath while maintaining the movement of the slip bath and then fed to drying.
• the slip bath Immersed in the slip bath, in particular, penetration of the catalyst slip, which is flowable under the action of shear forces, into the depressions of the rough enamel cover layer, and thereby mechanically stable interlocking of the enamel and the catalyst coating.
• the slip solidifies on the surfaces of the metallic, enamelled carrier to such an extent that it is no longer within the desired layer thickness, preferably 0.5 to 2 mm, under the influence of gravity from the surface of the plate-shaped carrier drains away.
• the catalyst slip in this case wets the profiling of a carrier plate in such a way that the increase in the thickness of the carrier plate due to the coating remains constant over the entire area, that is to say, for example, depressions are not filled with the catalyst slip.
• a carrier plate can be provided with layer thicknesses of up to 1 mm.
• the movement of the slurry bath can be achieved particularly advantageously by exchanging a vibration exciter or inserting a stirrer into the bath.
• the slip bath is moved indirectly starting from one or more vessel walls.
• the bottom of the vessel for the slip bath can be supported on a vibration exciter or vibrators can be arranged on the jacket of the same.
• the vibrations can be excited electromechanically, pneumatically or by ultrasound, with unregulated vibrations being generated in the slip bath while avoiding standing waves for the wetting of the basic framework coated with the basic enamel.
• expandable agents for example silicon carbide to the enamel frit
• the low-porosity bottom layer to the metallic see backbone blocks which cause blähCher during firing of the enamel, due to the share agent aufnch ⁇ the gas bubbles, the formation of a rough and viable for the catalyst slurry topcoat.
• Layer, the enamel the functions combines a thermal From ⁇ equal layer between the metallic carrier and the Coating of catalytically active compounds with those of a protective layer of the metallic basic structure and an adhesive layer for the coating to be applied.
• the liquefaction of the slip bath under the action of shear forces can be supported by additives having a thixotropic effect, such as, for example, xanthan and carboxypolymethylene.
• Another possibility of liquefying the catalyst slip under the action of shear forces consists in the choice of the particle size distribution on the basis of the production of the powder of compounds having a catalytic action.
• the powder is used in such a grain size distribution that less than 1% by weight has a grain diameter smaller than 10 lim and less than 5% by weight has a grain diameter larger than 200 ⁇ m of the powder.
• the above-mentioned grain size distribution can be adjusted by grinding, optionally with the addition of the liquid used to prepare the slip.
• Particularly advantageous for applying a firmly adhering coating is the addition of up to 2% of wetting agents and up to 5% of agents which liquefy the slip in addition to water and / or a binder up to the slip consistency corresponding to the desired thickness of the coating.
• organic esters are suitable as wetting agents and colloidal silicon dioxide is suitable as binders.
• Another advantage for increasing the strength of the coating due to the build-up of solid bridges is impregnation of the coated carrier with a Alkyl silicate or a solution thereof.
• a Alkyl silicate or a solution thereof tetramethyl orthosilicate or ethyl or methyl polysilicate, if appropriate mixed with industrial alcohols, in particular methanol, are suitable for this.
• connections are coated, to produce continuously, it proves to be particularly advantageous that steel that can be enamelled is first drawn off from a coil and profiled in series and separated into measurement sections and then further degreased or stained the measurement sections in series, an enamel applied to them and etched on them is fired, then the measuring sections are wetted in a moving bath of a catalyst slip and finally fired and optionally subsequently calcined.
• a coating process is technically simple to carry out. Due to the shaping of the plate-shaped carrier before it is coated with the catalytically active compounds, drying and, if appropriate, calcination of the coating is now to be carried out. The calcination, as a thermal aftertreatment, can only be added to the drying of the catalytically active compounds on the metallic support in cases of extreme erosive stress.
• circulating regenerative heat exchangers can be provided with carriers of catalytically active compounds both for the oxidation of carbon monoxide and for the reduction of the nitrogen oxides.
• those for the oxidation of carbon monoxide can be included in the mixtures of the catalytically active compounds for nitrogen oxide reduction or in the associated slip.
• the hot and cold gas side includes not only the combination within a single catalytic converter, but also the division into separate catalytic converters, for example those at the so-called hot end of a boiler system, in direct connection to the boiler egg for nitrogen oxide reduction and on so-called cold end, that is to say, for example, in direct association with wet desulfurization, within the exhaust gas stream of a boiler system.
• the danger can be countered that primary measures for nitrogen oxide reduction on the furnace side are purchased with an increased release of carbon monoxide in the exhaust gases to the environment, which equally pollutes the environment.
• the following example describes the production of plate-like supports with catalytically active compounds for the construction of catalysts for reducing nitrogen oxides in the exhaust gases from combustion plants.
• a basic enamel frit was applied to the metallic base frame in the form of carrier plates hanging from an endless conveyor belt while passing through a spray booth.
• the carrier plates were then predried in a pre-dryer at a temperature of 200 ° C. and then in a period of time between 6 and 10 minutes through a furnace with a temperature of 820 ° C.
• the carrier plates were then cooled in ambient air over a period of 30 minutes and then placed in a catalytic converter for a period of one minute. dipped in the analyzer slip bath and removed from the strip again. Subsequently, the carrier plates coated with the slip bath were dried in still ambient air for a period of 10 hours.
• the elongated container for the slip tape had a rectangular base area, with unregulated vibrations being generated in the container via vibration exciters attached to the side walls during the immersion process of the carrier plates.
• the catalyst slip bath consisted of a mixture of the powder titanium oxide, doped with transition metal oxides, in particular vanadium and tungsten oxides as catalytically active compounds, and a water glass with colloidal silicon oxide as a binder.
• the slip bath contained mineral fibers to increase the abrasion resistance.
• a carboxypoly ethylene-water mixture was also added as a thioxotropic agent.
• the slip bath also contained an organic ester ("Glydol" from Zschimmer & Schwarz) as a wetting agent.
• Coated carrier plates were installed in a stationary test section using the method described.
• the overflow length was 0.9 m.
• the addition of the reducing agent CAmmoniak) to this partial exhaust gas flow was equimolar, i.e. the ratio of the nitrogen oxides contained in the flue gases from the boiler to the ammonia added was 1. Under these conditions, a nitrogen oxide reduction of 82% was achieved.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Organic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Catalysts (AREA)
• Exhaust Gas Treatment By Means Of Catalyst (AREA)

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Publications (1)

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Cited By (1)

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Citations (2)

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• 1988
  • 1988-06-29 DE DE3821920A patent/DE3821920A1/de active Granted
• 1989
  • 1989-05-26 EP EP89906061A patent/EP0375759B1/de not_active Expired - Lifetime
  • 1989-05-26 US US07/457,816 patent/US4994430A/en not_active Expired - Lifetime
  • 1989-05-26 JP JP1505505A patent/JPH03500145A/ja active Pending
  • 1989-05-26 DE DE8989906061T patent/DE58901283D1/de not_active Expired - Fee Related
  • 1989-05-26 WO PCT/EP1989/000586 patent/WO1990000089A1/de not_active Ceased
  • 1989-06-29 ES ES8902287A patent/ES2013942A6/es not_active Expired - Fee Related

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