Study On Synthesis And Fluid Properties Of Janus Granules

Janus particles are a novel type of colloidal particles possessing different chemical characteristics at two hemispheres of particles. Because of their excellent characteristics of asymmetric structure, such particles are expected to be used as pharmaceutical carrier, colloidal surfactants, oil and gas exploiting materials. It is a challenging work in colloids field to prepare and apply of Janus particle. The good interfacial tension and emulsifying properties of Janus particles makes their to be a new class of highly-efficient oilfield development materials.Firstly, the Janus particles precursor SiO₂ microspheres are synthesized by sol-gel method, and then different factors influence the synthesis of SiO₂ microsphere size and morphology were discussed. The result showed that SiO₂ microsphere size became larger with the increase in the TEOS concentration. NH4OH concentration, water content, ionic strength of the electrolyte, the carbon chain length of the solvent. The reaction time had little affect on the particles size, but with the increase reaction temperature the particles size became smaller. Thus, an optimized condition of synthesizing the desired particle size of SiO₂ was obtained: TEOS concentration of 0.3mol/L,NH4OH concentration of 1.0mol/L, the reaction time of 10h, the reaction temperature of 25℃, and the cosolvent of ethanol, and the resultant SiO₂ particle diameter was 420nm.Secondly, the selected SiO₂ particles was used to fabricate the Janus particles by the paraffin wax protection-deprotection method. The exposed surface of SiO₂ particle hemisphere was modified with hydrophilic group of amino or hydrophobic carbon chain, and then melted the solid wax. The other hemisphere was modified with other chemical agent or remained unmodified using this method. The synthesized three different typle of Janus by this method were named as Janus-â… , Janus-â…¡ and Janus-â…¢ respecting.The Janus particles were characteristiced by the adsorption of gold atom to the surface which was modified by the amino groups by electrostatic force and the experiment of Janus particles dispersed on the oil-water interface. It was found that a single hydrophilic or lipophilic solid particle of SiO₂ cannot make the Pickering emulsion stable only by addition of the particles. But, the addition of oppositely charged surfactants can form a stable Pickering emulsion. To form a stable Pickering emulsion, it required the increase in the concentration of surfactant with the decrease in the particle size. It was concluded that the particle size of SiO₂ to be greater than 100nm which can uniform arrangement on the surface of the solid wax particles.Thirdly, the study of oil-water interfacial tension and emulfying experiment of liquid paraffin derived by different surface-modified SiO₂ particles concluded that the ability of reducing the interfacial tension between oil and water and emulsifying effect of liquid paraffin by different forms of Janus particles found that the Janus-â…¡ particles had the best effect than the other two typles of Janus. According to the research of interfacial tension between Daqing crude oil and simulate water using the optimized Janus-â…¡ particles mixed with different types of surfactant showed that there had a positive synergy between Janus-â…¡ particles and different cationic surfactants to reduce oil-water interfacial tension, had a negative synergy between Janus- â…¡ particles and different anionic surfactants, while there showed an interesting phenomenon between Janus- â…¡ particles and non-ionic and amphoteric surfactants to reduce the interfacial tension between Daqing crude oil and simulate water, first performance a positive synergism effect, after showing a negative synergy.Finally, according to the study of the complex system of Janus-â…¡ particles with different surfactants effect on the emulsifying effect of Daqing crude oil, it can be shown that the Janus-â…¡ exhibited a positive synergistic effect with cationic surfactants for the Daqing crude oil emulsification showed, and the O/W emulsions formed; and the complex of Janus-â…¡ with anionic surfactants had a negative effect on the oil emulsification. And then it also can be found that at higher concentrations of anionic surfactants and Janus-â…¡ particles, the emulsion converted from the original O/W type emulsion to W/O/W type. However, the complex of non-ionic surfactants with Janus-â…¡ first showed a positive influence on Daqing crude oil emulsion and then showed a negative synergistic effect, and with the increase of surfactant concentration the stability of emulsion decreased. The complex with zwitterionic surface active agent had the same effect with non-ionic surfactants. In general, the mixture of Janus-â…¡ particles with zwitterionic surfactant showed the better effect on Daqing crude oil emulsification and theemulsion was more stable. The effects of Janus-â…¡ particles with different types on Daqing crude oil emulsion have consistency with oil/water interfacial tension studies.