Hydrodehalogenation of chlorobenzene on activated carbon and activated carbon supported catalysts.
Chlorinated aromatic compounds in (waste) gases can be removed and/or dehalogenated by passing over a bed of activated carbon (AC) in a hydrogen containing atmosphere. Dehalogenation of the model compound chlorobenzene (PhCl) to HCl is complete at 490 degrees C--rather than the approximately 900 degrees C needed for the mere gas-phase reaction--but part of the benzene moieties is retained on the AC, resulting in its rather rapid deactivation, apparently due to a large decrease in surface area. Therefore, <1 mmol PhCl per gram of 'catalyst' could be processed. At 600 degrees C chlorobenzene yields 100% of both HCl and benzene, but still the AC lost most of its activity in time. Performances are compared of three different commercial ACs. As a HCl-washed AC is just as active, metals are not involved. This acid-washed AC was used as a support for 10 wt% Ni or Fe catalysts. While Fe did not show appreciable activity, results with Ni are promising. The yields of HCl and benzene from PhCl are approximately 100% already at T<400 degrees C, and T(50%) congruent with 260 degrees C, over 200 degrees C lower than with AC alone. There is no appreciable decrease of activity after having injected >20 mmol PhCl per gram of catalyst at partial conversion.
Santoro
Danilo
D
Center for Chemistry and the Environment, Leiden Institute of Chemistry, Gorlaeus Labs, Leiden University, 2300 RA Leiden, The Netherlands.
de Jong
Vincent
V
Louw
Robert
R
D001554:Benzene / Q000032:analysis; D002384:Catalysis; D002606:Charcoal / Q000737:chemistry*; D002722:Chlorobenzenes / Q000737:chemistry*; D004785:Environmental Pollutants; D005290:Ferric Compounds / Q000737:chemistry; D006851:Hydrochloric Acid / Q000032:analysis; D009532:Nickel / Q000737:chemistry; D009566:Nitrates / Q000737:chemistry; D013696:Temperature; D014865:Waste Disposal, Fluid / Q000379:methods*
D002722:Chlorobenzenes; D004785:Environmental Pollutants; D005290:Ferric Compounds; D009566:Nitrates; D002606:Charcoal; C022838:nickel chloride; D009532:Nickel; D001554:Benzene; C031294:chlorobenzene; C025302:ferric nitrate; D006851:Hydrochloric Acid