A quantative relationship exists between the structrue and physical properties of organic compounds.The molecular structrue of the examined compounds is selectively described by a molecular distance-edge（MDE）vector....A quantative relationship exists between the structrue and physical properties of organic compounds.The molecular structrue of the examined compounds is selectively described by a molecular distance-edge（MDE）vector.The physical properties of alkanes such as boiling points,density at 25℃,refractive index at 25℃, heat capacity at 300K,Gibbs energy,enthalpy at 300K are estimated with satisfactory results by a novel modified back- propagation neural network method based on the above MDEvectot.展开更多
采用巨正则系综蒙特卡罗(grand canonical Monte Carlo,GCMC)与分子动力学(molecular dynamics,MD)相结合的方法,研究烷烃分子在丝光沸石(MOR)型分子筛中的吸附和扩散性质.采用GCMC方法研究温度为300K、330K时,MOR型分子筛中甲烷、乙烷...采用巨正则系综蒙特卡罗(grand canonical Monte Carlo,GCMC)与分子动力学(molecular dynamics,MD)相结合的方法,研究烷烃分子在丝光沸石(MOR)型分子筛中的吸附和扩散性质.采用GCMC方法研究温度为300K、330K时,MOR型分子筛中甲烷、乙烷、丙烷、丁烷的吸附.研究表明,随着压力的增加吸附量增加,随温度的升高吸附量有所降低.饱和吸附量从大到小依次为:甲烷>乙烷>丙烷>丁烷.由模拟所得到的单组分吸附等温线,通过理想吸附溶液理论(IAST)计算二元混合物的吸附平衡相图,模拟结果与计算结果一致.采用分子动力学方法,研究乙烷、丙烷在MOR分子筛上的扩散性质,结果表明各个方向上的扩散系数不同,z方向上的扩散系数最大.展开更多
Zinc-modified Pt/SAPO-11 catalysts were prepared by incipient wetness impregnation and assessed in the hydroisomerization of n-octane.Their physicochemical properties were investigated using powder X-ray diffraction,s...Zinc-modified Pt/SAPO-11 catalysts were prepared by incipient wetness impregnation and assessed in the hydroisomerization of n-octane.Their physicochemical properties were investigated using powder X-ray diffraction,scanning electron microscopy,nitrogen adsorption-desorption,pyridine-adsorbed infrared spectroscopy,temperature-programmed desorption of NH3,temperature-programmed reduction of hydrogen,temperature-programmed desorption of hydrogen,transmission electron microscopy,and X-ray photoelectron spectroscopy.The addition of zinc resulted in high dispersion of platinum.Zinc acted as a competitive adsorbent,changed the location of platinum.The catalyst with a zinc loading of 0.5%gave the highest selectivity to dimethylhexanes,but the conversion was lower than those achieved with the other catalysts.Dimethylhexanes have large molecular diameters,and therefore their diffusion may be difficult.This weakens the catalytic activity of the zinc-modified catalysts and lowers the n-octane conversion.展开更多
In this paper,based on distance matrix and adjacent matrix,a new topological index has been developed to be used in research on physical and chemical properties of alkanes.It is concluded that the index bears good str...In this paper,based on distance matrix and adjacent matrix,a new topological index has been developed to be used in research on physical and chemical properties of alkanes.It is concluded that the index bears good structural selectivity and relativity.展开更多
Normal （n）-alkanes and polycyclic aromatic hydrocarbons （PAHs） in PM2.5 were collected from Beijing in 2006 and analyzed using a thermal desorption-GC/MS technique. Annual average concentrations of n-alkanes and P...Normal （n）-alkanes and polycyclic aromatic hydrocarbons （PAHs） in PM2.5 were collected from Beijing in 2006 and analyzed using a thermal desorption-GC/MS technique. Annual average concentrations of n-alkanes and PAHs were 282 ±96 and 125 ± 150ng/m^3, respectively： both were highest in winter and lowest in summer. C19-C25 compounds dominated the n-alkanes while benzo[b]fluoranthene, benzo[e]pyrene, and phenanthrene were the most abundant PAHs. The n-alkanes exhibited moderate correlations with organic carbon （OC） and elemental carbon （EC） throughout the year, but the relation- ships between the PAHs, OC and EC differed between the heating and non-heating seasons. The health risks associated with PAHs in winter were more than 40 times those in spring and summer even though the PM2.5 loadings were comparable. Carbon preference index values （〈1.5） indicated that the n-alkanes were mostly from fossil fuel combustion. The ratios of indeno[123-cd]pyrene to benzo[ghi]pyrelene in summer and spring were 0.58 ± 0.12 and 0.63 ± 0.09, respectively, suggesting that the PAHs mainly originated from motor vehicles, but higher ratios in winter reflected an increased infuence from coal, which is extensively burned for domestic heating. A comprehensive comparison showed that PAH pollution in Beijing has decreased in the past 10 years.展开更多
A novel atomic electronegative distance vector (AEDV) has been developed to express the chemical environment of various chemically equivalent carbon atoms in alcohols and alkanes. Combining AEDV and γ parameter, four...A novel atomic electronegative distance vector (AEDV) has been developed to express the chemical environment of various chemically equivalent carbon atoms in alcohols and alkanes. Combining AEDV and γ parameter, four five-parameter linear relationship equations of chemical shift for four types of carbon atom are created by using multiple linear regression. Correlation coefficients are R = 0.9887, 0.9972, 0.9918 and 0.9968 end roots of mean square error are RMS = 0.906, 0. 821, 1.091 and 1.091 of four types of carbons, i.e., type 1, 2, 3, and 4 for primary, secondary, tertiary, and quaternary carbons, respectively. The stability and prediction capacity for external samples of four models have been tested by cross-validation.展开更多
文摘A quantative relationship exists between the structrue and physical properties of organic compounds.The molecular structrue of the examined compounds is selectively described by a molecular distance-edge（MDE）vector.The physical properties of alkanes such as boiling points,density at 25℃,refractive index at 25℃, heat capacity at 300K,Gibbs energy,enthalpy at 300K are estimated with satisfactory results by a novel modified back- propagation neural network method based on the above MDEvectot.
文摘采用巨正则系综蒙特卡罗(grand canonical Monte Carlo,GCMC)与分子动力学(molecular dynamics,MD)相结合的方法,研究烷烃分子在丝光沸石(MOR)型分子筛中的吸附和扩散性质.采用GCMC方法研究温度为300K、330K时,MOR型分子筛中甲烷、乙烷、丙烷、丁烷的吸附.研究表明,随着压力的增加吸附量增加,随温度的升高吸附量有所降低.饱和吸附量从大到小依次为:甲烷>乙烷>丙烷>丁烷.由模拟所得到的单组分吸附等温线,通过理想吸附溶液理论(IAST)计算二元混合物的吸附平衡相图,模拟结果与计算结果一致.采用分子动力学方法,研究乙烷、丙烷在MOR分子筛上的扩散性质,结果表明各个方向上的扩散系数不同,z方向上的扩散系数最大.
基金supported by the National Natural Science Foundation of China(21676300)~~
文摘Zinc-modified Pt/SAPO-11 catalysts were prepared by incipient wetness impregnation and assessed in the hydroisomerization of n-octane.Their physicochemical properties were investigated using powder X-ray diffraction,scanning electron microscopy,nitrogen adsorption-desorption,pyridine-adsorbed infrared spectroscopy,temperature-programmed desorption of NH3,temperature-programmed reduction of hydrogen,temperature-programmed desorption of hydrogen,transmission electron microscopy,and X-ray photoelectron spectroscopy.The addition of zinc resulted in high dispersion of platinum.Zinc acted as a competitive adsorbent,changed the location of platinum.The catalyst with a zinc loading of 0.5%gave the highest selectivity to dimethylhexanes,but the conversion was lower than those achieved with the other catalysts.Dimethylhexanes have large molecular diameters,and therefore their diffusion may be difficult.This weakens the catalytic activity of the zinc-modified catalysts and lowers the n-octane conversion.
文摘In this paper,based on distance matrix and adjacent matrix,a new topological index has been developed to be used in research on physical and chemical properties of alkanes.It is concluded that the index bears good structural selectivity and relativity.
基金supported by the Natural Science Foundation of China(NSFC40925009 and NSFC41230641)a project from the "Strategic Priority Research Program" of the Chinese Academy of Sciences(XDA05100401)
文摘Normal （n）-alkanes and polycyclic aromatic hydrocarbons （PAHs） in PM2.5 were collected from Beijing in 2006 and analyzed using a thermal desorption-GC/MS technique. Annual average concentrations of n-alkanes and PAHs were 282 ±96 and 125 ± 150ng/m^3, respectively： both were highest in winter and lowest in summer. C19-C25 compounds dominated the n-alkanes while benzo[b]fluoranthene, benzo[e]pyrene, and phenanthrene were the most abundant PAHs. The n-alkanes exhibited moderate correlations with organic carbon （OC） and elemental carbon （EC） throughout the year, but the relation- ships between the PAHs, OC and EC differed between the heating and non-heating seasons. The health risks associated with PAHs in winter were more than 40 times those in spring and summer even though the PM2.5 loadings were comparable. Carbon preference index values （〈1.5） indicated that the n-alkanes were mostly from fossil fuel combustion. The ratios of indeno[123-cd]pyrene to benzo[ghi]pyrelene in summer and spring were 0.58 ± 0.12 and 0.63 ± 0.09, respectively, suggesting that the PAHs mainly originated from motor vehicles, but higher ratios in winter reflected an increased infuence from coal, which is extensively burned for domestic heating. A comprehensive comparison showed that PAH pollution in Beijing has decreased in the past 10 years.
基金Project supported by Ministry of Education "Chunhui Program" and Fok Ying Tung Education Foundation.
文摘A novel atomic electronegative distance vector (AEDV) has been developed to express the chemical environment of various chemically equivalent carbon atoms in alcohols and alkanes. Combining AEDV and γ parameter, four five-parameter linear relationship equations of chemical shift for four types of carbon atom are created by using multiple linear regression. Correlation coefficients are R = 0.9887, 0.9972, 0.9918 and 0.9968 end roots of mean square error are RMS = 0.906, 0. 821, 1.091 and 1.091 of four types of carbons, i.e., type 1, 2, 3, and 4 for primary, secondary, tertiary, and quaternary carbons, respectively. The stability and prediction capacity for external samples of four models have been tested by cross-validation.
