Formation Mechanism Study On Chloromercuridioxins/Furans In The Refuse Incineration Power Plant

The quantum chemical calculation method and density functional theory were used to analyze the chloromercuri-dibenzo-p-dioxins,and the suitable precursors were found to further study the gas-phase reaction mechanism of chloromercuri-dibenzo-pdioxins.Revealing the inherent law of the reaction,which provides the theoretical basis for the subsequent research on the chloromercuri-dibenzo-p-dioxins.The basis set of SDD was used for Hg,and the set of 6-31+G(d,p)was used for nonmetal atoms(C,H,O,Cl)by Gaussian09.The property of stable minimums were validated by vibration frequencies analysis.The regularized variational transition state theory with small curvature tunneling correction was used to calculate the activation energy.The geometrical structures of 15 chloromercuri-dibenzo-p-dioxins were optimized by quantum chemistry method to obtain the lowest energy geometrical structure.2,3,7,8-tetrachloromercuri-dibenzo-dioxins and 2,3,7,8-tetrachloromercuri-dibenzofurans were the most unstable structures which was found by the relationship between bond length and bond energy.The molecular dynamics of these two structures at 1000 K were calculated by using Gaussian 09.It was concluded that these 15 kinds of chloromercuri-dibenzo-p-dioxins were thermodynamically stable materials.The reaction mechanism of 4 cholro-chloromercuri-phenol with H and ·OH radicals was calculated by density functional theory.The reaction heat of O-H bond cleavage was calculated.The number of chloromercury substituents was negatively correlated with the intensity of OH bond in cholro-chloromercuri-phenol.The O-H bond cleavage reaction heat of cholro-metachloromercuri-phenol was lower than cholro-parachloromercuriphenol's.The range of reaction heat by using H is from-305 to-215 kcal/mol,and the range of reaction heat by using ·OH radicals is from-176 to-129 kcal/mol.Hydroxyl radicals were more effective than hydrogen atoms in the H abstraction reactions.Nine kinds of reactants contains 4 chloromercuri-phenoxy radicals which were used as precursors to synthesize 50 kinds of chloromercuri-dioxins/furans in 81 kinds of reaction pathways.The kinetic parameters from 298.15 K to 1500 K were calculated to obtain the optimal reaction activation energy.The formation mechanisms of 14 kinds of chloromercuri-dioxins/furans at 2,3,7,8 substituted position was obtained.The reaction of ring closure or intramolecular H elimination was the decisive step in the formation of dioxins,OH elimination reaction is the key step in formation of furans.The range of optimal reaction activation energy in forming dioxins was from 329.46 to 341.59 kcal/mol,which was from 325.54 to 371.26 kcal/ mol in foring furans.The activation energy of the reaction forming dioxins is lower than that forming furan.