Pressure Effect on the Rheological Behavior of Waxy Crude Oil with Comb-Type Copolymers Bearing Azobenzene Pendant

In this work, a pressure responsive poly(α-octadecene-co-maleic acid azobenzene amide) (Azo-MAC) was synthesized and able to enhance the flowability of waxy crude oil with asphaltenes significantly under high pressure. High-pressure UV-vis spectrometer was used to characterize its pressure response under pressures. The onset temperature and enthalpy during wax crystallization of Liaohe waxy crude oil under various pressures were determined by using high-pressure differential scanning calorimeter. The viscosity and yield stress were measured by high-pressure rheometer. On the basis of our experimental data, a mechanism was propounded that the conformation transformation from cis to trans of azobenzene groups in Azo-MAC at enhanced pressure may destroy the assembly of asphaltenes, disturb the crystallization of paraffins and thus improve the flowability of oils. Azo-MAC should be an ideal additive for exploitation and transportation of oils under high pressure.