Formation of chlorinated aromatics by reactions of Cl*, Cl2, and HCl with benzene in the cool-down zone of a combustor.
Conversion of benzene to chlorobenzenes and monochlorophenols by reaction with chlorine radicals (Cl*) in the cool-down zone of a plug-flow combustor has been studied, and a mechanistic analysis of the initial steps of the oxy-chlorination process is proposed. Superequilibrium concentrations of Cl* are formed during combustion of chlorocarbon species and persist at significant concentration levels even after a substantial reduction in the flue gas temperature (T = 500-700 degrees C). At these temperatures, Cl* attack on benzene present in trace concentrations (initial benzene concentration of 300 ppmv or 1080 ppmv were used for the experiments) in the post-flame gas is shown to result in stable chlorinated products (chlorobenzenes and chlorophenols) and loss of benzene. These results suggest that Cl* attack on trace level aromatics and possibly other organic species may be the initial step in the formation of a broad class of chlorinated and oxy-chlorinated pollutants in the post combustion zone.
Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Carlo
C
Procaccini
Joseph W
JW
Bozzelli
John P
JP
Longwell
Adel F
AF
Sarofim
Kenneth A
KA
Smith
D000393:Air Pollutants / Q000032:analysis*; D001554:Benzene / Q000737:chemistry*; D002712:Chlorides / Q000737:chemistry; D017606:Chlorine Compounds / Q000737:chemistry*; D004784:Environmental Monitoring; D006841:Hydrocarbons, Aromatic / Q000737:chemistry*; D006851:Hydrochloric Acid / Q000737:chemistry; D017745:Incineration; D012037:Refuse Disposal; D013696:Temperature
D000393:Air Pollutants; D002712:Chlorides; D017606:Chlorine Compounds; D006841:Hydrocarbons, Aromatic; D001554:Benzene; D006851:Hydrochloric Acid