| Crude oil,as the blood of industry,plays an irreplaceable role in the industrial production.However,with the depletion of petroleum resources,the light crude oil is rapidly decreasing,thereby the persistence of high wax and high asphaltene/resin heavy oil becoming the main resource in oil extraction and transportation gradually.However,long chain paraffins in waxy crude oil can usually precipitate as wax crystals when the temperature is reduced below the wax appearance temperature(WAT);and asphaltene/resin incline to aggregate in certain conditions.As a result,the viscosity of waxy crude oil or heavy oil is remarkably elevated,leading to a big challenge to the exploitation and transport of crude oils.In this work,a series of comb-type polymers containing various functional groups have been designed and synthesized with the aim to destroy the regularity of wax crystallization and prevent the aggregation of the asphaltene/resin through the assembly between the copolymers and the wax or asphaltene/resin,yielding a handle to improve flow-ability of crude oils.In addition,the underlying mechanism of the effects of comb-copolymers on the oil flow-ability has been revealed on the basis of the investigations on the interactions between the copolymers and crude oils.The specific work is summarized as follows:1.Waxy crude oil containing large amounts of paraffins often results in various difficulties in extraction and transportation,especially at low temperature.Comb-type copolymers with phenyl pendants have been found to be able to improve the flow-ability of waxy oils effectively.To investigate the influence of spacer length between phenyl pendant and polymer backbone in comb copolymers on the flow-ability of waxy oil,poly(a-octadecene-co-maleic acid phenyl alkyl amide)s with various spacer length were synthesized by modifications of poly(a-octadecene-co-maleic anhydride)with aniline(AMAC),phenethylamine(EMAC),phentermine(BMAC)and phenyl-undecanoicamide(UMAC),respectively.Their effects on the morphology and crystallization of model and crude oils were observed by polarized light microscopy and DSC.The flow-ability of these oils in the presence of copolymers were studied by means of rheology,including the measurements of yield stress,viscosity,and thixotropic properties.It demonstrates that the spacer length indeed presents remarkable effects on the rheological properties and wax crystallization behaviors of the oils.Longer spacer in the copolymers makes the phenyl pendants more flexible,leading to more effective dispersion of asphaltenes.Moreover,long spacer can co-crystallize with long chain paraffins.2.The flow behaviors of waxy crude oil and formation of wax deposits in the presence of polymeric wax depressants under normal pressure have been extensively investigated.However,the influences of pressure on the rheology of waxy oil and wax formation process are lack of investigations.In this work,a novel pressure responsive copolymer,poly(a-octadecene-co-maleic acid azobenzene amide)(Azo-MAC),was successfully synthesized.The pressure response of this copolymer under various pressures has been revealed by a high-pressure UV-Vis spectrometer(HP-UV).The rheological properties of Liaohe high waxy crude oil in the presence of copolymers,including yield stress and viscosity,were studied under different pressures relying on a high-pressure rheometer(HP-rheometer).In addition,the WAT of waxy oils as a function of different pressures were measured by high-pressure Differential Scanning Calorimeter(HP-DSC).In the condition of high pressure,it was found that the Azo-MAC copolymers translated into cis-configuration and presented a higher dispersion effect on asphaltenes compared with the copolymers without azo group.This can be explained by the increase in the distance between the two benzenes of Azo.The well dispersed asphaltenes thus block the crystallization of waxes and improve the flow-ability of waxy crude oil.These copolymers with pressure responsive functional groups are promising to be good wax inhibitors for the recovery and transportation of waxy crude oil under high pressures.3.It has been proposed that more than 30%of the composition of Liaohe heavy crude oil are resin,which thereby leads to challenging problems in oil recovery and transportation.In this study,matrix assisted laser desorption ionization-time of flight-mass spectrometer(MALDI-TOF-MS),elemental analysis,Fourier transform infrared(FTIR)spectroscopy,and nuclear magnetic resonance(NMR)were employed to determine the chemical structure of resin extracted from Liaohe heavy oil.The results showed that the resin molecule is composed of an anthracene bearing two cycloalkanes and six grafted alkyl chains.4.Through the studies on the resin aggregation behavior,the high viscous flow behavior of Liaohe heavy oil containing high concentration of resin can be explained.UV-visible spectroscopy(UV-Vis),turbidity measurement,dynamic light scattering(DLS),polarized light microscope(PLM),and scanning electron microscopy(SEM)were used to observe resin aggregation behavior by the addition of poor solvent.The effects of resin on the rheological properties of model oils were investigated systematically.The ?-? interactions between resin molecules impose a critical impact on the assembly of resins.The quantum mechanics calculations revealed that there were two low well depths of interaction energy when two resin molecules approach.This result implies that the bending and branching structure of resin aggregates may originate from the staggered stacking of resin molecules.These findings can improve our understanding on resin aggregation behavior,and thus enlighten the solution of flowing problem during recovery and transportation of heavy oil including a high content of resin.5.The maleic anhydride vinyl acetate copolymer was synthesized by free radical polymerization.Following the grafting of octadecylamine onto the side chain of the copolymer,aniline(PMN-A-18),naphthylamine(PMN-18),benzothiazole(PMV-B-18)were introduced onto the polymer back bone,respectively.The aforementioned three polymers were compared with previously synthesized AMAC,EMAC and BMAC bearing different length of spacer.In resin model oil,when acetone was added in,the resin would precipitate from the liquid system.UV-Vis spectroscopy found that the addition of polymer can effectively inhibit the red shift of resin aggregates produced by the addition of acetone,indicating the effective inhibition of the polymer on the resin aggregation.Relying on the static/dynamic light scattering experiments,the particle size and the diffusion coefficient can be detected to reveal the influence of the stability of resin in the presence of polymers.The results signify that PMV-B-18 shows a better dispersion ability since the benzimidazole groups can not only produce ?-? interactions but also can form hydrogen bonds with resin molecules.Furthemore,if is also found that the polymer backbone of the ester group can effectively increase the dispersion of the model resin oil in addition of acetone.Therefore,it suggests that the polymer backbone,the length of the spacer,and the polar groups play an important role on the performance of resin dispersant. |
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