10.1021/es1004285.s001
Qingzhu Zhang
Qingzhu
Zhang
Wanni Yu
Wanni
Yu
Ruixue Zhang
Ruixue
Zhang
Qin Zhou
Qin
Zhou
Rui Gao
Rui
Gao
Wenxing Wang
Wenxing
Wang
Quantum Chemical and Kinetic Study on Dioxin Formation from the 2,4,6-TCP and 2,4-DCP Precursors
American Chemical Society
2010
rate constants
DCP
MWI
TCP
SCT
precursor
chlorophenol
PCDD
calculation
CVT
formation mechanism
MPWB 1K level
PCDF
2010-05-01 00:00:00
Journal contribution
https://acs.figshare.com/articles/journal_contribution/Quantum_Chemical_and_Kinetic_Study_on_Dioxin_Formation_from_the_2_4_6_TCP_and_2_4_DCP_Precursors/2773312
This study focuses on the homogeneous gas-phase formation of polychlorinated dibenzo-<i>p</i>-dioxins (PCDDs) and dibenzofurans (PCDFs) from the 2,4,6-trichlorophenol (2,4,6-TCP) and 2,4-dichlorophenol (2,4-DCP) precursors, which were found both in the gas phase and in the fly ash samples as the dominating chlorophenol congeners in municipal waste incinerators (MWIs). Molecular orbital theory calculations have been performed for the formation mechanism. The geometrical parameters and vibrational frequencies of all the stationary points were calculated at the MPWB1K level with the 6-31+G(d,p) basis set. Single-point energy calculations were carried out at the MPWB1K/6-311+G(3df,2p) level of theory. Canonical variational transition-state (CVT) theory with small curvature tunneling (SCT) contribution was used to predict the rate constants of crucial elementary steps over the temperature range of interest (600−1200 K). The rate-temperature formulas were fitted for the first time. The pre-exponential factor, the activation energy, and the rate constants are reported. This study shows that at least one chlorine substituent in the ortho position is needed for the formation of PCDDs from the condensation of chlorophenols. The results presented here should help to clarify and detail the formation mechanism of PCDD/PCDFs (PCDD/Fs for short) from chlorophenol precursors in real waste combustion.