ИСТИНА

Asphaltenes are harmful components of heavy crude oil. They lead to high viscosity of oils, increase their transportation cost, and poison the catalytic systems. Currently, one of the main problems of oil industry is utilization of asphaltenes after their removing from heavy crude oil. In this research, we proposed a new method for solution of asphaltene utilization problem by creating asphaltene-stabilized water-in-oil emulsions with their following application. Asphaltenes are nanosize macromolecular particles that are adsorbed at the water/oil interface. They are natural surfactants, which for this reason could be used to stabilize concentrated emulsions of water as well as of saturated aqueous salt solutions. In turn, concentrated salt-containing emulsions can be used in agriculture as liquid fertilizers, which are a source of potassium, nitrogen, phosphorus, and other trace elements for plant nutrition. Another possible application consists in obtaining phase-change emulsion-based thermal energy storages. Asphaltenes were dissolved in ester oil in which water or aqueous salt solutions (such as ammonium nitrate, potassium monophosphate, and sodium acetate) were then emulsified. The morphology and rheology of asphaltene solutions and water-in-oil emulsions depending on asphaltene and dispersed phase concentrations were investigated by methods of optical microscopy and rotational rheometry. Asphaltenes are miscible with non-polar ester oil such as dioctyl sebacate. Up to a concentration of 65%, asphaltenes form dilute solutions that are Newtonian fluids. However, about 3% of asphaltenes are sufficient to make water-in-oil emulsions resistant to droplet coalescence. Water droplets form spatial agglomerates in asphaltene-solution medium, which lead to the fact that these emulsions are characterized by the presence of a yield stress even when the content of droplets is low. These emulsions are viscoelastic non-Newtonian fluids. Increasing the concentration of asphaltenes leads to a decrease of water droplets size and an increase in the effective viscosity of the emulsions. The use of asphaltenes allows obtaining emulsions containing up to 85 vol % of water droplets. With increasing water content, the viscoelasticity of emulsions and the value of their yield stress increase. Replacing water with saturated salt solutions does not cause the emulsions to lose their resistance to coalescence, which opens the possibility of their further use in agriculture or for other purposes.