The hydrogen abstraction reactions by ozone from fluoromethanes(CH3F, CH2F2) are the most suitable processes for modeling and testing methodologies that could be applied to larger molecules or to the complete reaction...The hydrogen abstraction reactions by ozone from fluoromethanes(CH3F, CH2F2) are the most suitable processes for modeling and testing methodologies that could be applied to larger molecules or to the complete reaction kinetic schemes for the degradation of HFCs. We presented a theoretical study of the hydrogen abstraction reactions from CH3F and CH2F2 by ozone molecule. The geometries, harmonic vibrational frequencies of all stationary points were calculated at MPW1K level of the theory. The energies of all the stationary points were refined by using higher-level(denoted as HL) energy calculations. The minimum energy paths(MEPs) were obtained by the MPW1K/6-31+G(d,p) level. Energetic information of the points along the MEPs is further refined by HL method. The rate constants were evaluated on the basis of the MEPs from the HL level of theory in the temperature range of 200—2500 K with the conventional transition state theory(TST), the canonical variational transition state theory(CVT) and the microcanonical variational transition state theory(μVT) based on the ab initio calculations. A general agreement was found among the TST, CVT, and μVT theories. The fitted three-parameter Arrhenius expressions of the calculated forward CVT/SCT, and μVT/Eckart rate constants of the ozonolysis of fluoromethane are kCVT/SCT(T)=2.76×10-34 T 5.81 e(-13975/T) and kμVT/Eckart(T)=1.15×10-34 T 5.97 e(-14530.7/T), respectively. The fitted three-parameter Arrhenius expressions of the calculated forward CVT/SCT, and μVT/Eckart rate constants of the ozonolysis of difluoromethane are kCVT/SCT(T)=2.29×10-36 T 6.42 e(-15451.6/T) and kμVT/Eckart(T)=1.31×10-36 T 6.45 e(-15465.8/T), respectively.展开更多
The potential energy surface and reaction mechanism corresponding to the reaction of ytterbium monocation with fluoromethane, which represents a prototype of the activation of C-F bond in fluorohydrocarbons by bare la...The potential energy surface and reaction mechanism corresponding to the reaction of ytterbium monocation with fluoromethane, which represents a prototype of the activation of C-F bond in fluorohydrocarbons by bare lanthanide cations, have been investigated for the first time by using density functional theory. A direct fluorine abstraction mechanism was revealed, and the related thermochemistry data were determined. The electron-transfer reactivity of the reaction was analyzed using the two-state model, and a strongly avoided crossing behavior on the transition state region was shown. The present results support the reaction mechanism inferred from early experimental data and the related thermochemistry data can provide a guide for further experimental researches.展开更多
利用气相色谱法来测定F22生产尾气中的F23的浓度。该方法是在GB T 7375-2006《工业用氟代甲烷类纯度的测定气相色谱法》的基础上,用gaspro柱进行分离,用TCD进行检测,用归一化法进行定量计算。经过改进后的方法简单可靠,通过世界银行、SG...利用气相色谱法来测定F22生产尾气中的F23的浓度。该方法是在GB T 7375-2006《工业用氟代甲烷类纯度的测定气相色谱法》的基础上,用gaspro柱进行分离,用TCD进行检测,用归一化法进行定量计算。经过改进后的方法简单可靠,通过世界银行、SGS及DOE的多次核查和认定。展开更多
文摘The hydrogen abstraction reactions by ozone from fluoromethanes(CH3F, CH2F2) are the most suitable processes for modeling and testing methodologies that could be applied to larger molecules or to the complete reaction kinetic schemes for the degradation of HFCs. We presented a theoretical study of the hydrogen abstraction reactions from CH3F and CH2F2 by ozone molecule. The geometries, harmonic vibrational frequencies of all stationary points were calculated at MPW1K level of the theory. The energies of all the stationary points were refined by using higher-level(denoted as HL) energy calculations. The minimum energy paths(MEPs) were obtained by the MPW1K/6-31+G(d,p) level. Energetic information of the points along the MEPs is further refined by HL method. The rate constants were evaluated on the basis of the MEPs from the HL level of theory in the temperature range of 200—2500 K with the conventional transition state theory(TST), the canonical variational transition state theory(CVT) and the microcanonical variational transition state theory(μVT) based on the ab initio calculations. A general agreement was found among the TST, CVT, and μVT theories. The fitted three-parameter Arrhenius expressions of the calculated forward CVT/SCT, and μVT/Eckart rate constants of the ozonolysis of fluoromethane are kCVT/SCT(T)=2.76×10-34 T 5.81 e(-13975/T) and kμVT/Eckart(T)=1.15×10-34 T 5.97 e(-14530.7/T), respectively. The fitted three-parameter Arrhenius expressions of the calculated forward CVT/SCT, and μVT/Eckart rate constants of the ozonolysis of difluoromethane are kCVT/SCT(T)=2.29×10-36 T 6.42 e(-15451.6/T) and kμVT/Eckart(T)=1.31×10-36 T 6.45 e(-15465.8/T), respectively.
基金supported by the National Science Foundation of Shandong Province(No.Z2000B02).
文摘The potential energy surface and reaction mechanism corresponding to the reaction of ytterbium monocation with fluoromethane, which represents a prototype of the activation of C-F bond in fluorohydrocarbons by bare lanthanide cations, have been investigated for the first time by using density functional theory. A direct fluorine abstraction mechanism was revealed, and the related thermochemistry data were determined. The electron-transfer reactivity of the reaction was analyzed using the two-state model, and a strongly avoided crossing behavior on the transition state region was shown. The present results support the reaction mechanism inferred from early experimental data and the related thermochemistry data can provide a guide for further experimental researches.
