Effect of aromatic and aliphatic pendants in poly(maleic acid amide-co-vinyl acetate) on asphaltene precipitation in heavy oil

Asphaltene precipitation often brings difficulties to the recovery and transportation of heavy crude oil. Poly(maleic acid amide-co-vinyl acetate) copolymers with various aromatic (phenyl, naphthyl, and benzimidazole) pendants and/or aliphatic (octyl, tetradecyl, and octadecyl) grafts were synthesized and found to be capable of dispersing asphaltenes effectively. To study the influence of aromatic and aliphatic pendants in copolymers on asphaltene precipitation behaviors, the initial precipitation point, turbidity, and size of asphaltene precipitates from model heavy oils in the presence and absence of copolymers were determined by UV-vis spectroscopy, turbidity meter, and dynamic light scattering, respectively. The effect of copolymers on the viscosity of Tahe heavy oil with high asphaltene content was investigated by the rheological approach. The results revealed that the copolymers with both aromatic and aliphatic pendants dispersed asphaltene, reduced its precipitates, and thus improved the flowability of Tahe heavy oil more effectively than those with only aromatic or aliphatic graft. The combination of pi-pi delocalized conjugation attraction" from blocking" from pendants and "steric aliphatic grafts should be the reason.