Study On The Influence Of Heavy Crude Components And Emulsifiers On The Interfacial Properties

Gudao and Liaohe heavy crudes were isolated to polar components by adsorption chromatograph. By means of the modified Brown-Ladner's method, the average structural parameters of heavy crudes and their polar components were calculated based on nuclear magnetic resonance spectroscopy combined with infrared spectroscopy, ultimate analysis and average molecular weight determination. In order to search for the interaction between emulsifiers and heavy crude components, the relation between composition structure and interfacial properties of components, the oil-water interfacial tension and zeta potential of components simulated oil were studied.Gudao and Liaohe heavy crudes with the characteristic of high density, high viscosity, high solidifying point, high acid number and basic nitrogen content are typical heavy crudes. In the series of components, resin and asphaltene have the characteristic of high content, high acid number and basic nitrogen content, more hetero atoms, more ring structure. Therefore, most of the polar substance of heavy crudes concentrated in resin and asphaltene.The study of interfacial activity of heavy crudes and components showed that, saturate is inertia in the interface, aromatic has no interfacial activity, resin and asphaltene are the main interfacial active agents in heavy crudes. Resin and asphaltene have following characteristic: little H/C ratio, more hetero atoms, high acid number and basic nitrogen content, all of these lead to the high interfacial activity of polar components, decreased the interfacial tension of their simulated oil. For same component of different oils, the one whose average molecular weight, acid number and basic nitrogen content are higher, has stronger interfacial activity. For different polar components of the same oil, the one with larger aromatic factors and condensation index of aromatic ring, smaller branchiness index, has stronger interfacial activity. Heavy crudes and polar components were more active in the alkalic condition, this comes to the conclusion that acidic groups are prevailing in heavy crudes and polar components. Concentration of sodium chloride in aqueous phase made only a small contribution to the interfacial tension, this suggest that most of the interfacial active agents in heavy crudes are oil-soluble.When water phase was pure water, the zeta potential of heavy crudes and components simulated emulsions were negative and their absolute values increased with the polarity of components in oil phase. In the strong acidic and alkalic conditions, the zeta potential of simulated emulsion has a greater decrease more than that under neutral condition. Under strong acidic environment, the zeta potential reduced by 60mV. The absolute value of zeta potential were decreased by the addition of salt.With a larger branchiness index, saturate decreased the solubility of asphaltene in the saturate-asphaltene simulated oil, so there was negative synergetic effect between saturate and asphaltene. With larger aromatic factor and condensation index of aromatic ring, aromatic had a larger aromaticity, it could increase the solubility of resin and asphaltene; Thanks to the low branchiness index and small molecular volume, aromatic molecule could insert into resin and asphaltene aggregate and break them, and the number of structural unit increased, so there were positive synergetic effect between aromatic and resin, aromatic and asphaltene; The synergetic effect between resin and asphaltene derived from the hydrogen-bonding energy.In the process of emulsify, the higher the polarity of component, the stronger the intermolecular force between component and emulsifier. The interaction between component and emulsifier lied on the interfacial activity of components, and the higher interfacial activity is, the stronger interaction is. Saturate and aromatic, which hadn't interfacial activity, hardly adsorb on the interface, and had no chance to interact with emulsifiers. Resin and asphaltene, which had many heteroatom groups, could get to the interface and interact with emulsifier there. In the neutral, weak acidic and weak alkalic conditions, the interaction between component and anionic emulsifier was stronger, and the interfacial tension of simulated oil reduced to 2mN·m^-1,the zeta potential increased to 120mV. The addition of salt could increase the interaction between component and anionic emulsifier, and the stability of emulsion was enhanced.