Hao Wen

Molecular dynamics simulation on the decomposition of type SII hydrogen hydrate and the performance of tetrahydrofuran as a stabiliser

Molecular dynamics simulation is used to study the decomposition and stability of SII hydrogen and hydrogen/tetrahydrofuran (THF) hydrates at 150 K, 220 K and 100 bar. The modelling of the microscopic decomposition process of hydrogen hydrate indicates that the decomposition of hydrogen hydrate is led by the diffusive behaviour of H2 molecules. The hydrogen/THF hydrate presents higher stability, by comparing the distributions of the tetrahedral angle of H2O molecules, radial distribution functions of H2O molecules and mean square displacements or diffusion coefficients of H2O and H2 molecules in hydrogen hydrate with those in hydrogen/THF hydrate. It is also found that the resistance of the diffusion behaviour of H2O and H2 molecules can be enhanced by encaging THF molecules in the (51264) cavities. Additionally, the motion of THF molecules is restricted due to its high interaction energy barrier. Accordingly, THF, as a stabiliser, is helpful in increasing the stability of hydrogen hydrate.

Theoretical discussion on the mechanism of binding CO2 by DBU and alcohol

Quantum chemical studies on the reaction of binding CO2 by amidine base diazabicyclo [5.4.0]-undec-7-ene (DBU) and alcohol were carried out at the B3LYP/6-31g(d) level in order to find the reaction mechanism. The structures of reactants and product were optimised, and thermodynamic analyses were also carried out using the single point energy calculation and frequency analyses. It is noted that the reaction of binding CO2 by DBU and propanol is thermodynamically feasible and qualitatively in accordance with the experimental observations. The results of thermodynamic and kinetic analyses demonstrate that the possible reaction mechanisms can be a two-step bimolecular reaction and a one-step trimolecular reaction. In the two-step bimolecular mechanism, the first step is the formation of intermediate by DBU and CO2, and the second step is the nucleophilic attack of propanol on the intermediate. In the one-step trimolecular mechanism, O and H atoms of hydroxyl in propanol form an O–C bond with CO2 and an H–N bond with DBU, respectively. The one-step trimolecular reaction seems a more reasonable mechanism because of the consideration of kinetic parameters.

Quantum chemical study on influence of substituents and solvents in reaction complexing ethylene with nickel dithiolene

The influences induced by various terminal substituents and solvents on the reaction mechanism and chemical dynamics of complexing ethylene with Ni dithiolene are theoretically studied by using B3LYP method and Onsager model. It is shown that the reaction should be a two-step process, and the first step is the rate-determining step. We find that the rate constant of the rate-determining step becomes small when the electron-donating ability of the substituents is increased, while it becomes large when the electron-withdrawing ability of the substituents is increased. Subsequently, we consider the solvent effects on the reaction adding ethylene to the simplified hydrogen-substituted nickel dithiolene. It is found that the solvents will make slight changes to the geometries of the reactants, transition states, intermediates and products. However, the corresponding molecular dipole moments become large with the increase of the solvent polarity, which is beneficial to accelerate the reaction. Moreover, we show that, as the solvent polarity becomes large, the activation energies of the reaction decrease exponentially, while the reaction rate constants increase exponentially. These results demonstrate that in polar solvents, the reaction complexing ethylene with Ni dithiolene may become easier and faster to occur, and the product rate is improved. We believe that this research can be seen as a reference for complex and solvent selection in olefin separation process.

The design and development of a project-oriented information system

In this paper, the idea of building a project-oriented information system based upon a specialized information database was discussed. It attempts to provide tools for helping researchers use Internet resources effectively in the course of their research. Based on this idea, a web-based project-oriented information system was constructed. The paper systematically expounds the design and development process of the project-oriented information system. Furthermore, examples of utilizing the project-oriented information system to obtain useful information and suggestions for specific projects were described. According to our discussion and utilization of the system, we believe that building a project-oriented information system can help researchers with their research projects.