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
  • B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
  • B01J21/18—Carbon
• • 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
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
  • B01J27/06—Halogens; Compounds thereof
• • 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
  • B01J37/22—Halogenating

Definitions

• the invention relates to a method for producing a catalyst for removing nitrogen oxides from exhaust gases with the addition of ammonia, the catalyst, which consists of a carbon-containing material, being treated with a halogen or a halogen compound.
• the halogen for. B. bromine is released so that the catalytic activity decreases again.
• the released halogen reacts with ammonia to form ammonium halide. So that the halogen or the ammonium halide is not released into the atmosphere, the adsorbent layer must be followed by a further adsorbent layer in which the released bromine or ammonium bromide is adsorbed.
• the invention is based on the object of further developing the method of the type mentioned at the outset such that when the catalyst is used there is no release of a halogen or a halogen compound and the catalytic activity of the carbon-containing material is retained.
• the irreversibly bound bromine or chlorine does not react with ammonia to form ammonium bromide or chloride. There is therefore no removal of bromine or chlorine or ammonium bromide or chloride. Comparatively small quantities are therefore sufficient for the doping.
• Another advantage of the process according to the invention is that no ammonium nitrate or ammonium nitrite form on the carbon-containing adsorbents treated according to the invention.
• the gas mixture of inert gas and gaseous bromine or chlorine or gaseous bromine or chlorine compound being circulated at (low) adsorption temperature the carbon-containing material is passed through, and then the doped carbon-containing material is fed to a second reactor, with bromine or chlorine or bromine or chlorine compounds split off being separated at (higher) desorption temperature and optionally in the circuit of the first and / or or second reactor are given up again, it is possible to produce powerful catalysts.
• the two-stage treatment works with temperature ranges which are above the later operating temperature, the bromine or chlorine remaining on the carbon-containing material or the bromine or chlorine compounds are stable, ie the exhaust gas is not mixed with bromine or Chlorine contamination contaminated.
• an adsorption reactor 1 is charged with a carbon-containing material 7, which has a catalytic property, via an allocation device 3.
• the carbon-containing material 7 contained in the reactor 1 is heated to a predetermined temperature, which is preferably approximately 100 ° C. to 150 ° C., via a heating device.
• a predetermined temperature which is preferably approximately 100 ° C. to 150 ° C., via a heating device.
• iron bromide (FeBr,) or iron chloride (FeCl-,) can sublimate, so it is advisable not to heat iron-containing material above about 100 ° C.
• the carbon-containing material 7 in the reactor 1 is preferably designed as a traveling layer.
• the traveling layer in the reactor 1 is flowed through with an inert gas which flows via a line 12 into the Reactor 1 is introduced after 4 gaseous bromine or chlorine or bromine or chlorine compounds have been mixed in an evaporator, for example vaporous bromine or chlorine or hydrogen bromine or hydrogen chloride.
• the inert gas releases its gaseous load, the bromine or chlorine or the bromine or chlorine compound, to this material.
• the latter is continuously withdrawn from the adsorption reactor 1 via a discharge member 6 and fed to a desorption reactor 2.
• the doped carbon-containing material 9 drawn off from the adsorption reactor 1 is treated in the desorption reactor 2 with a desorption temperature in the range from about 200 ° C. to 500 ° C.
• the doped carbon-containing material 9 passes through the reactor 2 as a traveling layer, the bromine or chlorine or the bromine or chlorine compounds, hydrogen bromine or chlorine or FeBr .. or FeCl not being stably deposited at the selected treatment temperature . ,, split off and fed to an evaporator 5 via a line 10.
• the bromine or chlorine or the bromine or chlorine compounds can be used for another purpose (line 14) or returned to the circuit of the reactor 1 via the evaporator 4 (line 15).
• An inert gas stream is fed into the desorption reactor 2 via line 11, which flows through the reactor 2 in countercurrent to the doped carbon-containing material 9. The inert gas can be recycled.
• the residence times in the adsorption reactor 1 can be about 1 h to 20 h.
• the corresponding residence time in the desorption reactor is expediently about 0.5 h to 2 h.
• a commercially available activated coke with the trade name D 52/4 which is manufactured by the applicant, has proven to be a particularly suitable carbon-containing adsorbent.
• D 52/4 A commercially available activated coke with the trade name D 52/4, which is manufactured by the applicant, has proven to be a particularly suitable carbon-containing adsorbent.
• Table 1 a preactivate of an anthracite coal and two different activated cokes C 40/4 such as D 52/4 were doped with bromine from the gas phase at 140 ° C. and annealed at 300 ° C. The amount of bromine offered from the gas phase was 10 or 5% by weight. Only the activated coke D 52/4 was treated with the latter value.
• the pre-activate had 5.3% by weight, the active coke C 40/4 4.7% by weight and the two active cokes D 52/4 2.8 and 2.7% by weight .-? o 'residual bromine.
• the catalysts prepared in this way have been used according to Examples 2 to 4 for NO separation
• Table 2 lists the test conditions on which a laboratory test was based. Table 2; Test conditions in the laboratory
• Example 2 The laboratory tests according to Example 2 were hardened in a pilot plant. The test conditions in the pilot plant are shown in Table 4.
• the bromine-doped catalyst achieved a 30% higher NO conversion than the undoped one with a little less than half the residence time.
• the halogen bromine other experiments have been carried out with chlorine.
• the activated carbons doped with it better results could also be achieved than with activated carbons without doping, but not quite as good as activated carbons doped with bromine. This can be seen in FIG. 2, which shows a correlation of different carbon catalysts with the active surface area (ASA).

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Organic Chemistry (AREA)
• Materials Engineering (AREA)
• Environmental & Geological Engineering (AREA)
• Biomedical Technology (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• General Chemical & Material Sciences (AREA)
• Analytical Chemistry (AREA)
• Health & Medical Sciences (AREA)
• Catalysts (AREA)
• Exhaust Gas Treatment By Means Of Catalyst (AREA)
• Treating Waste Gases (AREA)

Applications Claiming Priority (2)

Publications (1)

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Family Applications (1)

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Citations (4)

• 1988
  • 1988-12-17 DE DE19883842527 patent/DE3842527A1/de active Granted
• 1989
  • 1989-12-14 WO PCT/EP1989/001536 patent/WO1990006802A1/de not_active Ceased

Patent Citations (4)

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