Interfacial dilational viscoelasticity of nitrogen containing components of Daqing crude oil

Two kinds of nitrogen containing components of Daqing crude oil, N1 and N2, were enriched and separated by complexation and adsorption chromatography, respectively. The dilational viscoelastic properties at kerosene-water interface containing N1 and N2 were investigated, respectively, by means of oscillating drop method. The dependencies of dilational modulus and phase angle on frequency, and N1 and N2 concentration were expounded. The experimental results showed that the interfacial dilational regularity of N1 and N2 were similar to each other because of their close relative molecular mass. However, due to their different content of nitrogen, their interfacial dilational behaviors were different. Compared N1 with N2 each other, the nitrogen content of N1 was higher and nitrogen heterocyclic rings in the molecule structure of N1 was more, so its volume was larger and activity was stronger, and the oil-water interfacial tension with N1 was lower and dilational modulus was larger at lower concentrations. Because the molecule of N2 possessed smaller volume, they arranged more closely at the interface of oil-water and were easy to diffuse between interface and bulk phase, resulting in lower interfacial tension and smaller dilational modulus at higher concentrations. The difference in interfacial dilational viscoelasticity for the two nitrogen containing components was caused by their different relaxation processes.