Synthesis Of New Pour Point Depressants Based On EVA Structure And Corresponding Mechanism Analysis

Crude oil is a complex mixture of saturated hydrocarbons,naphthenes,aromatic hydrocarbons,asphaltenes and resins.Wax is a mixture of hydrocarbons,high wax content leads to high wax precipitation temperature(WAT).When the oil temperature is lower than the WAT,wax crystals appear and tend to form a three-dimensional network structure in the oil phase,resulting in poor fluidity,or even the loss of fluidity,which causes difficulties for the exploitation and transportation of crude oil.As a common chemical additive,pour point depressant(PPD)is widely used in the process of exploitation and transportation of crude oil.It can effectively improve the fluidity of crude oil and reduce the transportation cost and risk of crude oil.Daqing crude oil belongs to paraffin-based crude oil,which has the characteristics of high pour point,high viscosity and high wax content.However,the traditional PPDs have poor sensitivity to high waxy crude oil.In order to further improve the performance of traditional EVA PPD,compounding EVA and fatty acid amide.The graft modified EVA PPD and EVA/nano-MMT composite PPD were prepared based on compounding experiment,and macro fluidity test and micro wax crystal analysis of crude oil were carried out.Based on the experimental results and relevant literature,the PPD mechanism of various new PPDs was analyzed and summarized in detail,laying a good foundation for the PPD structure optimization in the future.The main research contents and results of this paper are as follows.The depressing performance of EVA PPDs with different VA content was tested,and the best PPD of them was EVA(33).Therefore,EVA(33)was selected for the subsequent experiments.A series of fatty acid amide compounds were synthesized and compounded with EVA(33).The experimental results show that there is a good synergistic effect between EVA PPD and fatty acid amide.Fatty acid amide can further improve the performance of EVA PPD and reduce the pour point of crude oil.Among them,the carbon number of alkyl long chain has influence on the PPD performance of fatty acid amides,and when the carbon number is 18 and 20,the combination with EVA PPD has the best depressant effect.A series of symmetric double-chain maleic acid compounds were synthesized by esterification and amidation reaction.A series of symmetrical double-chain maleic acid compounds were grafted to EVA to synthesize graft modified EVA compounds which were characterized by ~1H-NMR and GPC.It is proved that all graft modified EVA PPDs has the better pour point and viscosity depressing performance than that of EVA PPDs by pour point and rheological test.Among them,the PPD graft 18 carbon exhibit the best co-crystallization ability between PPD molecules and wax crystal molecules which exhibits the best depressing performance.The PPD containing N is more conducive to wax crystal dissolution and wax crystal dispersion than the PPD containing O.when PPD containing benzene ring,it promotes the dissolution of PPD in crude oil,dispersing wax crystals and changing the precipitating habit of wax crystal.The best pour point depressing performance was obtained with 0.1 wt%of the PPD,in which the pour point dropped from 38°C to 16°C,and the depressant rate can reach 57.9%.The morphology and quantity of wax crystal changed obviously after adding different graft modified EVA PPDs.The nano-montmorillonite(nano-MMT)was modified by octadecyl trimethyl ammonium chloride(OTAC).Based on the organic modification of nano-MMT,the EVA/nano-MMT(NEVA)PPD was prepared and confirmed by XRD analysis and so on.Through depressing performance experiments of model oil and crude oil,the depressing performance order of NEVA is as follows:NEVA(33)>NEVA(28)>NEVA(38).NEVA(33)can reduce the pour point of crude oil from 38°C to 22°C,and the depressing rate reaches42.1%.NEVA PPDs with different VA content has good viscosity reduction ability.The morphology and quantity of model oil and crude oil wax crystal changed obviously after adding different NEVA PPD,the morphology between model oil and crude oil wax crystal is different due to the existence of resin and asphaltene.