Synthesis Of Nanoparticals In 1, 1, 1, 2-Tetrafluoroethane Fluid

Abstract A new method for synthesizing size-controllable nano-particales in hydrofluorocarbon fluid is proposed. Considering the lower critical temperature and lower critical pressure of hydrofluorocarbon fluid than that of supercritical carbon dioxide(scCO₂), and its easy being operated in industry, the nano-reactor formed in microemulsion containing fluorinated surfactant and water system is used to synthesize nano-particales. The fluorinated surfactants having high solubility in hydrofluorocarbon fluid will be synthesized in this project because it is very important to form microemulsion in hydrofluorocarbon fluid media. Obtaining the physical properties of hydrofluorocarbon fluid, which is useful to a new catalytic reaction and synthesis of polymeric materials in this system. The structure and size of the nano-reactor formed in microemulsion are affected by type of surfactant and surfactant concentration in supercritical fluid. By adjusting the properties of nano-reactor, nano-particales formed in this reactor are size controllable. The effects of reaction style, separation of nano-particales and purification of nano-particales synthesis process will also be studied, which is beneficial to the synthesis of nano-materials in the industrial application of this new process. The results of this investigation will impact on the application of hydrofluorocabon fluid in industry, nano-material science and application of nanoreactor.1. A series of surfactants, sodium salt of dibutyl-2-sulfosuccinate (DBSS), sodium salt of dipentyl-2-sulfosuccinate (DPSS), sodium salt of dihexyl-2-sulfosuccinate (DHSS) and sodium salt of dioctyl-2-sulfosuccinate (DOSS) were synthesized. A series of fluorinated AOT (Aerosol-OT, AOT) analogues surfactants, sodium salt of bis (2,2,3,3,3-pentafluoro-propyl)-2-sulfosuccinate (di-CF2), sodium salt of bis(2,2,3, 4,4,4-hexafluoro-butyl)-2-sulfosuccinate (di-HCF3), sodium salt of bis(3,3,4,4,5,5, 6,6,6-nonafluoro-hexyl)-2-sulfosuccinate (di-HCF5) and sodium salt of bis(2,2,3,3-tetrafluoro-propyl)-2-sulfosuccinate (di-HCF2) were synthesized using fluorinated alcohol with different length of chain and fluorinated degree. The target products were obtained by filtration, extraction, distillation, recrystallization. The surfactants synthesized were characterized by ¹H NMR and elemental analysis.2. A static method coupled with gravimetric analysis is developed to measuresolubility of surfactants in 1,1,1,2-tetrafluoroethane (HFC-134a) and supercritical CO2. The solubilities of surfactants in HFC-134a and SCCO2 are affected by temperature, pressure and length of hydrocarbon. The solubilities of surfactants in HFC-134a and SCCO2 increased with increasing of temperature and pressure. The solubility of the same surfactant in HFC-134a fluid is approximately two times as compared with that in the most commonly used SCCO2. The surfactant with longer hydrocarbon has higher solubility in HFC-134a and SCCO2. We selected surfactants with higher solubility as compounds to form microemulsion in HFC-134a and SCCO2.3. The pressure-temperature phase diagrams for W/HFC-134a microemulsions stabilized by surfactants synthesized were determined using cloud-point measurements under different conditions in a high pressure vessel. The phase behaviors in supercritical CO2 and HFC-134a fluid of different surfactants were as a function of temperature, pressure, water-to-surfactant ratio, and the concentration of surfactants. At a fixed temperature, cloud point pressures increased with increasing water-to-surfactant molar ratio and surfactant concentrations. The surfactant with the longest hydrocarbon chain has the highest cloud point pressure even at lower surfactant concentrations. While we find the cloud point pressures decrease with increasing temperature at fixed Wo and surfactant concentration, and this phenomenon is in opposition to the results in supercritical CO2.4. CuS nanoparticles were prepared by inverse microemulsion method in HFC-134a fluid. The nanoparticales were separated by Rapid Expansion of Supercritical Solution(RESS), and washed with organic solvent and water. The products were characterized through Transmission Electron Microscopy (TEM). The diameter of the nanoparticales systhesized in water/HFC-134a microemulsion is related to the diameter of water core. The diameter of the nanoparticales increases with increasing of Wo.