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
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
Measurements of three chlorofluorocarbons (CFCs): trichlorofluoromethane (CFC-11), dichlorodifluoromethane (CFC-12) and trichlorotrifluoroethane (CFC-113), along with methyl chloroform (CH 3CCl 3) and carbon tetrachlo...Measurements of three chlorofluorocarbons (CFCs): trichlorofluoromethane (CFC-11), dichlorodifluoromethane (CFC-12) and trichlorotrifluoroethane (CFC-113), along with methyl chloroform (CH 3CCl 3) and carbon tetrachloride (CCl 4) were made in water samples from Lake Washington, using Electron Capture-Gas Chromatography (EC-GC). The samples were collected in mid-autumn, a period when the lake’s upper layer undergoes rapid cooling. At the time of sampling, a strong vertical temperature gradient was present in the lake, with surface temperatures of ～14℃, and near bottom (50 meters) temperatures of ～8℃. The concentrations of dissolved CFC-12 and CFC-11 increased with depth, as expected from the higher solubilities of these gases at lower temperatures. Atmospheric measurements made at the sampling site at the time of the cruise, showed that CFC-11 and CFC-12 saturations in the near surface samples were 100 % and 106%, respectively. For the deepest sample (52 meters) CFC-11 and CFC-12 saturations were 102 % and 126 %. Because the surface layer of the lake responds to changes in atmospheric CFCs on a time scale of several weeks, the higher than equilibrium concentrations of CFC-12 observed at the time of sampling may reflect earlier episodes of elevated levels of atmospheric CFC-12 in this urban area. High concentrations of dissolved CFCs in runoff or industrial effluent might also lead to elevated CFC levels in the lake. The cold, deep water of Lake Washington is relatively isolated from the effects of surface gas exchange except during winter, and the supersaturations observed in the deep layer may reflect periods of elevated atmospheric CFC-12 levels from the previous winter season. These results were compared to summertime profiles of CFC-11 and CFC-12 made in 1994.展开更多
Trifluoroiodomethane (CF3l) is consider as a Promising refrigerant alternative, especially as a component inmixtures, to replare CFC-12. But reliable thermophysical propelty data for CF3I are still limited. The invest...Trifluoroiodomethane (CF3l) is consider as a Promising refrigerant alternative, especially as a component inmixtures, to replare CFC-12. But reliable thermophysical propelty data for CF3I are still limited. The investigationson thermophysical Propelties of CF3I developed by us are summarized in this paper. Experimental data of criticalParamethe, and the condations of saturated liquid and vapor density, enthaipy of vaporization, vapor pressurs,PVT prowtes, second vinal coefficient ideal-gas heat capacity, surface tension, viscosity and thermalconduchvity are given in the Present paper.展开更多
Pentafluoroethane (HEC-125) and trifluoroiodomethane (CF3I) are considered as promising refrigerant alternatives, especially as components in mixtures, to replace CFCs or HCFCs. Effective uses of HFC-125 and CF3I requ...Pentafluoroethane (HEC-125) and trifluoroiodomethane (CF3I) are considered as promising refrigerant alternatives, especially as components in mixtures, to replace CFCs or HCFCs. Effective uses of HFC-125 and CF3I require that the thermophysical properties be accurately measured. In the present work, vapor pressure data of HFC-125 and CF3I have been measured in the temperature range from 292 to 337 K and 288 to 336 K, respectively. Maximum total pressure uncertainty of HEC-125 data is estimated to be within ±1.2 kPa and ±780 Pa for CF3I. Based on the data set and literature values, the vapor pressure equations for HEC-125 and CF3I have been developed. The relative deviation of the equations correlate the measurements within 0.022% for HEC-125 and 0.068% for CF3I, respectively.展开更多
基金supported by the National Natural Science Foundation of China(Nos.U1604283,21402041)the Plan for Scientific Innovation Talent of Henan Province(No.164200510008)+2 种基金the China Postdoctoral Science Foundation Funded Project(No.2016M592293)the Program for Innovative Research Team in Science,Technology in University of Henan Province(No.15IRTSTHN003)the Program of Introducing Talents of Discipline to Universities(111 Project,No.D17007)~~
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.
文摘Measurements of three chlorofluorocarbons (CFCs): trichlorofluoromethane (CFC-11), dichlorodifluoromethane (CFC-12) and trichlorotrifluoroethane (CFC-113), along with methyl chloroform (CH 3CCl 3) and carbon tetrachloride (CCl 4) were made in water samples from Lake Washington, using Electron Capture-Gas Chromatography (EC-GC). The samples were collected in mid-autumn, a period when the lake’s upper layer undergoes rapid cooling. At the time of sampling, a strong vertical temperature gradient was present in the lake, with surface temperatures of ～14℃, and near bottom (50 meters) temperatures of ～8℃. The concentrations of dissolved CFC-12 and CFC-11 increased with depth, as expected from the higher solubilities of these gases at lower temperatures. Atmospheric measurements made at the sampling site at the time of the cruise, showed that CFC-11 and CFC-12 saturations in the near surface samples were 100 % and 106%, respectively. For the deepest sample (52 meters) CFC-11 and CFC-12 saturations were 102 % and 126 %. Because the surface layer of the lake responds to changes in atmospheric CFCs on a time scale of several weeks, the higher than equilibrium concentrations of CFC-12 observed at the time of sampling may reflect earlier episodes of elevated levels of atmospheric CFC-12 in this urban area. High concentrations of dissolved CFCs in runoff or industrial effluent might also lead to elevated CFC levels in the lake. The cold, deep water of Lake Washington is relatively isolated from the effects of surface gas exchange except during winter, and the supersaturations observed in the deep layer may reflect periods of elevated atmospheric CFC-12 levels from the previous winter season. These results were compared to summertime profiles of CFC-11 and CFC-12 made in 1994.
文摘Trifluoroiodomethane (CF3l) is consider as a Promising refrigerant alternative, especially as a component inmixtures, to replare CFC-12. But reliable thermophysical propelty data for CF3I are still limited. The investigationson thermophysical Propelties of CF3I developed by us are summarized in this paper. Experimental data of criticalParamethe, and the condations of saturated liquid and vapor density, enthaipy of vaporization, vapor pressurs,PVT prowtes, second vinal coefficient ideal-gas heat capacity, surface tension, viscosity and thermalconduchvity are given in the Present paper.
文摘Pentafluoroethane (HEC-125) and trifluoroiodomethane (CF3I) are considered as promising refrigerant alternatives, especially as components in mixtures, to replace CFCs or HCFCs. Effective uses of HFC-125 and CF3I require that the thermophysical properties be accurately measured. In the present work, vapor pressure data of HFC-125 and CF3I have been measured in the temperature range from 292 to 337 K and 288 to 336 K, respectively. Maximum total pressure uncertainty of HEC-125 data is estimated to be within ±1.2 kPa and ±780 Pa for CF3I. Based on the data set and literature values, the vapor pressure equations for HEC-125 and CF3I have been developed. The relative deviation of the equations correlate the measurements within 0.022% for HEC-125 and 0.068% for CF3I, respectively.
