Performance and Mechanism of Span Surfactants as Clean Flow Improvers for Crude Oil

In this work, Span 60 and Span 80, two representatives of nonionic surfactants, were evaluated as clean flow improvers for crude oil. The results show that both of these two nonionic surfactants can improve the flow properties of crude oil samples, especially the Span 80. In a certain condition, maximum viscosity reduction ratio of crude oil with Span 80 was up to 70.0% and the maximum pour points decrease was 9.0°C. DSC thermograms and microphotographs discover the co-crystallization of Span 80 and saturated hydrocarbon component of the crude oil, which causes the wax crystal accumulation not closely and reduces the wax peak temperature and wax precipitation point of crude oil. Combined with the steady conformations analysis, mechanism of Span surfactants as clean flow improvers for crude oil was further discussed. Due to the cis -double bonds in Span 80 and crystal form transition of wax crystal growth with Span 80, Span 80 was superior to Span 60 as flow improvers for crude oil.