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Decomposition of monochlorobiphenyl isomers in supercritical water in the presence of methanol
Author(s) -
Anitescu Gheorghe,
Tavlarides Lawrence L.,
Munteanu Valentin
Publication year - 2004
Publication title -
aiche journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.958
H-Index - 167
eISSN - 1547-5905
pISSN - 0001-1541
DOI - 10.1002/aic.10154
Subject(s) - chemistry , supercritical water oxidation , supercritical fluid , reactivity (psychology) , methanol , arrhenius equation , activation energy , decomposition , order of reaction , isothermal process , oxygen , kinetics , reaction rate constant , thermodynamics , organic chemistry , medicine , alternative medicine , physics , pathology , quantum mechanics
Comprehensive studies of monochlorobiphenyl (MCB) decomposition in supercritical water in the presence of methanol and other cosolvents, both with and without oxygen, are being conducted to understand the reaction kinetics and pathways of individual PCB isomers and to determine the structure–reactivity relationships. In the present study the disappearance rate of MCBs, delivered in an isothermal plug‐flow tubular reactor as methanolic solutions, is investigated at 25 MPa and temperatures of 673, 723, and 773 K. Experiments are conducted at nominal MCB feed concentrations of 1–100 μmol/L (reaction conditions) using MCB/MeOH and H 2 O 2 /H 2 O solutions (1–3 g/L and 0–10 wt. %, respectively). Molar conversions of these isomers vary from 3% (2‐CB, 773 K, 2 s) to 30% (4‐CB, 773 K, 46 s) without oxygen (SCWT) and from 1% (2‐CB, 673 K, 3.8 s) to 97% (4‐CB, 773 K, 24.5 s) with oxygen (SCWO). For SCWT the overall conversion follows apparent first order, whereas for SCWO the conversion is second order. The regressed data lead to Arrhenius parameters of frequency factor and activation energy with values of 10 20.5 –10 21.3 s −1 and 320–331 kJ/mol for SCWT and 10 24.1 –10 24.8 s −1 (mol/L) −1 and 281–292 kJ/mol for SCWO, respectively. The reactivity of the MCB isomers increases in the order 2‐MCB < 3‐MCB < 4‐MCB. The positively identified reaction products by GC‐MSD and GC‐FID/ECD/TCD analyses are mainly biphenyl, open‐ring biphenyl compounds such as acetophenone and benzaldehydes, and mineral products (CO, CO 2 , and HCl). More studies are in progress regarding the role of the second solvent on reaction rates and reaction mechanisms and pathways. © 2004 American Institute of Chemical Engineers AIChE J, 50: 1536–1544, 2004