In order to improve the flowing effect of offshore crude oil in pipeline transportation,polymethylperfluoroalkyl ethylcarboxylate-maleic anhydride(GM)is made from methylperfluoroalkyl ethylcarboxylate(GMA)and maleic anhydride(MA),and with azodiisobutyronitrile as initiator.GM is taken as main component to compound with ethylene-vinyl acetate copolymer(EVA)to obtain fluorine-containing carboxylate-maleic anhydride pour point depressant for crude oil.The synthesis conditions for GM copolymer,the factors influencing the de-coagulation effect,the rheology and micromorphology of crude oil before and after addition of pour point depressant are evaluated and analyzed.Results show that the optimal synthesis conditions for GM copolymer are as follows:the molar ratio of GMA to MA is 5∶1,the dosage of azodiisobutyronitrile is 0.6 wt.%,reaction temperature is 75℃,and reaction time is 8 h.There exists a synergistic effect between GM and EVA.The freezing point of crude oil declines by 13℃to 5.5℃when w(GM)∶w(EVA)=6∶4 and the dosage of pour point depressant is 400 mg·L-1.At 10℃,the viscosity of crude oil after adding pour point depressant decreases to 93.1 mPa·s from 562.9 mPa·s before adding pour point depressant,with a reductionrate of 83.5%,and the yield value of crude oil decreases from 986.6 Pa to 68.02 Pa,with a decrease of 93.1%.Before and after dosing,the wax crystal morphology changes from rod-needle like large aggregate stacking to small aggregate dispersion,and the dosing generates obvious effect on improving the low-temperature flow state of crude oil.
fluorine-containing copolymerspour point depressantsynergistic de-coagulationrheologymicrostructure
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