Structure effect in the demulsification performance of cationic surfactants

In this study, various cationic surfactants and MgO nanoparticles were used for dehydration of crude oil. The results of bottle tests exhibited that in demulsification of crude oil in the serious of alkyl trimethyl ammonium bromide homologs (CnTAB, n = 12, 14, and 16) with the increase of alkyl chain length, the optimum concentration level decreased and speed of dehydration decreased. Also, for surveying the role of head group, two cetrimonium bromide and cetylpyridinium bromide surfactants were used. Evaluation of the counter ion effect indicated in the high concentration of surfactants the counter ion can greatly influence the demulsification performance. Moreover, for enhancing demulsification, MgO nanoparticles were mixed with cetrimonium bromide (CTAB) surfactant. The mixture of MgO nanoparticles and CTAB (in ratio 1:3) could dehydrate crude oil in 300s. For better understanding of asphaltene-demulsifier interaction, was used the quantum calculation. The results demonstrate MgO interacts with asphaltene strongly. As well as the result of asphaltene adsorption on MgO indicate the asphaltene adsorption flow from Freundlich model. Finally, the interaction energy between surfactants or MgO and asphaltene were estimated by quantum calculation.