Numerous thermal processes （e.g. waste incineration, steel and nonferrous industry, wastes recycling plants, hot dip galvanizing etc. ） have been identified as emission sources of PolyChlorinated Dibenzo-p-Dioxins ...Numerous thermal processes （e.g. waste incineration, steel and nonferrous industry, wastes recycling plants, hot dip galvanizing etc. ） have been identified as emission sources of PolyChlorinated Dibenzo-p-Dioxins （PCDD） and PolyChlorinated DibenzoFurans （PCDF）, which are named in brief ＂dioxins＂ The processes by which such dioxins （PCDD/F） are formed are still incompletely understood and probably proceed catalytically by multiple and parallel pathways. However, two major pathways of formation have been identified during final stages of the combustion process： The first one is the precursor route, i.e. the formation of PCDD/F from related structures, such as simple or chlorinated benzenes, phenols, biphenyls, and polycyclic aromatic hydrocarbons （PAH）, and the second one is the de novo synthesis of PCDD/F from macromolecular solid carbon （ or other structures unrelated to dioxins）, organic and inorganic chlorine, oxygen, etc. Knowledge of the relevant thermodynamic parameters is essential for predicting possible stability domains of PCDD/F during combustion processes and their equilibrium distribution at emission sources. In the previous study, thermodynamic parameters of PCDDi predicted with density functional theory （DFF） method have been reported. A comprehensive thermodynamic database of the standard entropy （ S^0 ）, specific heat （Cp）, enthalpy of formation （ΔfH^0） and Gibbs free energy of formation （ΔfG^0） for 135 gaseous PCDF （including dibenzofuran） was studied. From the enthalpies of formation the order of stability of individual congeners is reported. Additionally, the results obtained in this study are compared with values determined by other electronic structural methods.展开更多
In this paper, the thermodynamic parameters are calculated for all gaseous Poly Chlorinat Dibenzo-p-dioxins （PCDDs） using the Density Functional Theory （DFF） method and both the enthalpy of formation （ΔfH^0） an...In this paper, the thermodynamic parameters are calculated for all gaseous Poly Chlorinat Dibenzo-p-dioxins （PCDDs） using the Density Functional Theory （DFF） method and both the enthalpy of formation （ΔfH^0） and Gibbs free energy of formation （Δf G^0） are derived, from which the order of stability of individual congeners is then predicted. All these properties, together with the calculated entropies （ S^0） and heat capacities （ Cp）, are presented as a function of the number of chlorine atoms in the various PCDD molecules. The accuracy of the method used here, is evaluated by comparing the thermodynamic parameters of gaseous chlorobenzenes with experimental values collected from literature.展开更多
文摘Numerous thermal processes （e.g. waste incineration, steel and nonferrous industry, wastes recycling plants, hot dip galvanizing etc. ） have been identified as emission sources of PolyChlorinated Dibenzo-p-Dioxins （PCDD） and PolyChlorinated DibenzoFurans （PCDF）, which are named in brief ＂dioxins＂ The processes by which such dioxins （PCDD/F） are formed are still incompletely understood and probably proceed catalytically by multiple and parallel pathways. However, two major pathways of formation have been identified during final stages of the combustion process： The first one is the precursor route, i.e. the formation of PCDD/F from related structures, such as simple or chlorinated benzenes, phenols, biphenyls, and polycyclic aromatic hydrocarbons （PAH）, and the second one is the de novo synthesis of PCDD/F from macromolecular solid carbon （ or other structures unrelated to dioxins）, organic and inorganic chlorine, oxygen, etc. Knowledge of the relevant thermodynamic parameters is essential for predicting possible stability domains of PCDD/F during combustion processes and their equilibrium distribution at emission sources. In the previous study, thermodynamic parameters of PCDDi predicted with density functional theory （DFF） method have been reported. A comprehensive thermodynamic database of the standard entropy （ S^0 ）, specific heat （Cp）, enthalpy of formation （ΔfH^0） and Gibbs free energy of formation （ΔfG^0） for 135 gaseous PCDF （including dibenzofuran） was studied. From the enthalpies of formation the order of stability of individual congeners is reported. Additionally, the results obtained in this study are compared with values determined by other electronic structural methods.
文摘In this paper, the thermodynamic parameters are calculated for all gaseous Poly Chlorinat Dibenzo-p-dioxins （PCDDs） using the Density Functional Theory （DFF） method and both the enthalpy of formation （ΔfH^0） and Gibbs free energy of formation （Δf G^0） are derived, from which the order of stability of individual congeners is then predicted. All these properties, together with the calculated entropies （ S^0） and heat capacities （ Cp）, are presented as a function of the number of chlorine atoms in the various PCDD molecules. The accuracy of the method used here, is evaluated by comparing the thermodynamic parameters of gaseous chlorobenzenes with experimental values collected from literature.
