Papers by Keyword: Aromatic Hydrocarbons

Abstract: Different methods are used to prepare gallium-containing zeolites of a ZSM-5 structure. Their acidic and structural characteristics are investigated and the effect of the method of gallium introduction into a zeolite on distribution and ratio of acid sites of different strengths, as well as on pore volume and diameter is determined. The relationship between the localization of gallium introduced into a zeolite by different methods and its electronic state and the catalytic activity and selectivity of the resulting contacts in the course of propane aromatization is established. The Ga-containing zeolite prepared by impregnation is found to be the most efficient catalyst for conversion of propane into aromatic hydrocarbons.

Abstract: Using BP neural network method, we calculate and analyze the molecular structure of aromatic hydrocarbons. Then, we get the electrotopological state indices and the molecular electronegativity distance vectors of 25 aromatic hydrocarbons based on the calculation of molecular structure characteristics and adjacency matrix. By regression, we get and optimize the structural parameters E₉, E₁₃, E₁₇ and M₁₅. The four structural parameters are used as the input variables and a 4-2-1 network structure is employed to construct a BP artificial neural network model for predicting acute toxicity pEC₅₀. The total correlation coefficient R is 0.994 and the average error between the predicted value and experimental value of pEC₅₀ is 0.079, which indicate that the ANN model has good stability and superior predictive ability. The results show that there is a good nonlinear correlation between acute toxicity pEC₅₀ and the four structural parameters. The results of our research reveal that the toxicity of aromatic hydrocarbons is closely affected by electrotopological state indices and the molecular electronegativity distance vectors. Therefore, it will be helpful in assessing the hazard of aromatic hydrocarbons to environment.

Abstract: The mechanism of the formation of Cooper pairs and their role in the occurrence of nondissipative diamagnetic currents is investigated. In the previous works [1-, we suggested that in the materials with large HOMO-LUMO gaps (ΔE_HOMO-LUMO,N), the Cooper pairs are formed by the large HOMO-LUMO gaps as a consequence of the quantization of the orbitals by nature, and by the attractive Coulomb interactions between two electrons with opposite momentum and spins occupying the same orbitals via the positively charged nuclei. On the other hand, according to the recent experimental research [, the Cooper pairs have been observed at room temperatures in the neutral benzene (6an), naphthalene (10ac), anthracene (14ac), and coronene molecules. That is, our prediction in our theoretical researches [1-can be well confirmed by the recent experimental research [, and our previous theory can be reasonably applied to the explanation of the mechanism of the occurrence of the granular high temperature superconductivity in carbon materials [. We show that the forming of Cooper pairs [ can be well explained by our theory previously suggested [1-. We also suggest the reasonable mechanism of the occurrence of granular high temperature superconductivity in the graphite powder treated by water or exposed to the hydrogen plasma, discovered by Esquinazi et al. [, on the basis of our previous theoretical works described above [1-, which can be well confirmed by the recent experimental work [. We also suggest the general guiding principle towards high temperature superconductivity. We suggest that any material with large ΔE_HOMO-LUMO,N value (more than a few eV), in which valence bands are completely occupied by electrons, which has been believed to be typical insulator in view of solid state physics and chemistry, has a possibility to exhibit high temperature superconductivity in solids.

Abstract: Marine ecosystems are affected by aromatic hydrocarbons. The predicting ability based on the quantitative structureactivity relationships (QSAR) model of unknown aromatic hydrocarbons toxicity is one of the tasks of security precaution. To establish the QSAR model between the physical and chemical properties of aromatic hydrocarbons and the inhibited activity of Chlorella vulgaris(C. Vulgaris), the optimized geometries, based on the 96 hr-EC₅₀ of 25 aromatic hydrocarbons with C. Vulgaris were carried out at the B3LYP/6-311G** level by density functional theory (DFT) calculation. With matlab2 010(a) software, genetic algorithm principal components regression (GAPCR) methods was used to develop the QSAR model and compared to traditional PCR model. PC1+PC3+PC5+PC6+PC8 were finally selected by GAPCR method. The of training, prediction data set and LOO cross validation are 0.918, 0.956 and 0.933, respectively. Meanwhile, the results of PCR were 0.949, 0.755 and 0.825, respectively. The results of this work showed that the GAPCR method has great results and good generalization capability. Comparing two motheds results indicting that GAPCR gives superior results to traditional PCR procedure.

Abstract: By using CoMFA and CoMSIA methods, the new quantitative structures of 25 aromatic hydrocarbons and the 96 hr-EC₅₀ data with C. vulgaris have been investigated to obtain more detailed insight into the relationships between molecular structure and bioactivity. Compared to CoMFA (the average Q2LOO option =0.610), CoMSIA (the average Q2LOO =0.736) has the better results with robustness and stability. CoMSIA analysis using steric, electrostatic, hydrophobic, and H-bond donor and acceptor descriptors show H-bond donor is the common factor for influencing the toxicity, the steric and electrostatic descriptors are next and the hydrophobic descriptor was last. From the contour maps, the number of benzene ring is more crucial for the compound toxicity and the compounds with more benzene ring make toxicity increased. Under the same number of benzene ring, the kind of substituent group and the formed ability of H-bond are the other parameters to influencing the aromatic hydrocarbons toxicity.

Abstract: The process of diamond synthesis using metal as a catalyst-solvent is a great method of industrial production by using high pressures and high temperatures. Several aromatic hydrocarbons are already studied for the process of graphitization of carbon, many have already been tried for use as raw materials for diamond synthesis. The graphitization of anthracene was carried out at a pressure of 3Gpa at a temperature of 1000°C. The graphite was produced in mixed Ni-Mn alloy for diamond synthesis process at a pressure of 4.5 GPa at a temperature of 500° to 1300°C. Scanning electron microscope (SEM) and X-ray diffraction (XRD) techniques were used to characterize the transformation of graphite into diamond produced with anthracene starting at high pressures and high temperatures. The results of this study show that there is a diamond shape through an aromatic hydrocarbon at high pressures and temperatures with a catalyst-solvent process.

Abstract: The catalytic effect of HZSM-5 on fast pyrolysis of lignin was investigated by using an analytical pyrolyzer coupled with Gas Chromatography and Mass Spectrometry (Py-GC/MS). The distribution of products was studied primarily obtained at different reaction conditions of temperature and addition ratio of HZSM-5. The main products were phenols and aromatic hydrocarbons. With the addition of HZSM-5, the content of phenols was decreased from 67.66% (for pure lignin) to 26.07%, and the content of aromatic hydrocarbons was increased from 10.77% to 57.38% when the mass ratio of HZSM-5: lignin was 1:1. However, the effect of temperature on the reaction activity of HZSM-5 in the range of 400-600°C was not significant. It was concluded that the addition of HZSM-5 enhanced the conversion of phenols to aromatic hydrocarbons by deoxygenation, and this effect was improved with the addition ratio of HZSM-5 increasing.