This paper presents the results of molecular dynamics (MD) simulation on the rutile titanium dioxide and potassium hexatitanate (K2O.6TiO2 or K2Ti6O13) crystal. The interaction of atoms is described by two-body central force interatomic potential, which includes Coulombic term, Gilbert-type repulsion term, van der Waals term and Morse-type potential. The optimized crystal structure of rutile TiO2 is in very good agreement with the experimental data in the literature. The present MD simulation also gives several physical properties, including volume thermal expansivity and elastic bulk modulus.
Abstract A cylindrical pore model was used to represent approximately the pore of β-zeolite catalyst that had been used in the alkylation of benzene with ethylene and spherical Lennard-Jones molecules represented the components of the reaction system-ethylene, benzene and ethylbenzene. The dual control volume-grand canonical molecular dynamics (DCV-GCMD) method was used to simulate the adsorption and transport properties of three components under reaction in the cylindrical pore at 250℃ and 270℃ in the pressure range from 1 MPa to 8 MPa. The state map of the reactant mixture in the bulk phase could be divided into several different regions around its critical points. The simulated adsorption and transport properties in the pore were compared between the different near-critical regions. The thorough analysis suggested that the high pressure liquid region is the most suitable region for the alkylation reaction of benzene under the near-critical condition.
The microstructure of cationic gemini surfactant 1,6-bis(dodecyldimethylammonium) hexane dibromide C12H25(CH3)2N(CH2)6N(CH3)2C12H252Br (126122Br) and oppositely charged polyelectrolyte poly(acrylic acid, sodium salt) (NaPA) in aqueous solution has been studied by using fluorescence, conductivity measurement, freeze-etching and TEM. The data obtained from fluorescence and conductivity measurement show that micelle-like or complex can form between the gemini surfactant (126122Br) and polyelectrolyte NaPA due to the static electric interaction and hydrophobic forces. Through freeze-etching and TEM, the microstructure of the mixture solution has been studied, which is consistent with the result from micropolarity. Comparing the fluorescence spectrum of system of dodecyltrimethylammonium bromide (DTAB) and NaPA with that of system of gemini surfactant (126122Br) and NaPA, it can be found that the interaction between gemini surfactant (126122Br) and NaPA is stronger than that between DTAB and NaPA. And the phase behavior of (126122Br) and NaPA in aqueous solution has also been detected. It can be shown that the precipitate will transform into gel in higher NaPA concentration.
