Separation and analysis of interface-active substances in Daqing crude oil

The interface-active substances (IFSs) are separated by extracting Daqing crude oil with a NaOH/methanol mixture. The procedure of extraction and following treatment is optimized. The amount of IFSs obtained is in range 0.80 - 0.93 mg/g crude and is 0.877 mg/g crude in average. FT-IR and element analyses show that the IFSs are composed mostly of organic acids and of some nitrogen-containing polar substances. Their number-average molecular weight is 480 (by VOP). The interfacial tension between 1.0% IFSs solution in toluene and alkaline solutions is low,of 10 -2 mN/m.