Study On The Synergy Between Asphaltene And Wax On The Properties Of High Pour Point Oil Under Microwave

The crystallization and precipitation of wax in high pour point oils will have an adverse impact on its fluidity and bring many problems to the production and transportation.However,asphaltene as one of the most important polar non-hydrocarbon components in high pour point oils,will participate in the crystallization and precipitation process of wax molecules and affect the gelation behavior of high pour point oils.Due to the special interaction between microwave electromagnetic field and material molecules,microwave technology has significant advantages in improving the fluidity of high pour point oils.In order to further improve the performance,the relationship between the synergy of asphaltene and wax and the content of asphaltene and its influence on wax crystallization under microwave were studied,furthermore,the interaction mechanism between asphaltene and wax molecules under microwave electric field was explored by combining experimental research and molecular dynamics simulation.In macroscopic experiments,the effects of asphaltene synergistic wax on wax crystallization and the properties of high pour point oil under microwave were investigated,where the high pour point model oils were prepared using various asphaltene contents.In the scope of the testing asphaltene concentration（0～0.70 wt%）and microwave power（0～3.0 k W）,when 0.10 wt%asphaltenes are added into the model oils and 1.0 k W microwave power is applied,the viscosity and the wax appearance temperature present the lowest and the viscosity reduction effect is the best at low temperature.With the increase of asphaltene contents or microwave power,the viscosity and the WAT increase gradually.It is partially because that the addition of a small amount of asphaltenes make some wax crystals exhibit amorphous properties and reduce the crystallinity of wax crystals,meanwhile,the application of 1.0 k W microwave power will also destroy the crystal structure of wax crystals and reduce the crystallinity.From the morphology of mesoscopic wax crystal,with the increase of asphaltene contents,the wax crystals gradually change from rod shape to ellipsoid shape,and the average particle size,perimeter and average area decrease firstly and then increase.When microwave power is 1.0 k W,the average particle size,average perimeter and average area of wax crystal increase,but the range of particle size distribution becomes wider,therefore its viscosity decreases according to the suspension theory.Besides,the addition of asphaltenes and the application of 1.0 k W microwave power increase the dielectric constant and dielectric loss factor of the sample oils,indicating that the abilities of the simulated oils to absorb microwave energy and to convert microwave into heat energy are enhanced,benefiting to the active interaction between wax molecules in model oils and electric field.In macroscopic molecular dynamics simulation,the relationship between the synergy of asphaltene and wax and the content of asphaltene in homogeneous system of high pour point oils under external electric field were investigated by establishing the molecular model and its mechanism was discussed.Below the WAT,in the scope of the testing asphaltene concentration（0～4.50 wt%）and electric field strength（0～6.4V/nm）,the aggregation of wax molecules in the high pour point oil model systems is mainly the aggregation of long-chain wax molecule C₃₈H₇₈ compared with the short-chain wax molecule C₂₆H₅₄.When adding 1.50 wt%asphaltenes and applying 1.6 V/nm electric field strength,asphaltene is relatively dispersed,the spatial interference effect is strong,the aggregation degree between long-chain wax molecule C₃₈H₇₈ decreases and the diffusion coefficient increases;With the increment of asphaltene contents and electric field strengths,the aggregation degree increases,which promotes the aggregation of long-chain wax molecule C₃₈H₇₈ and decreases the diffusion coefficient.Meanwhile,below the WAT,a small amount of asphaltenes and appropriate electric field strength will produce an induction effect,resulting in the increment of dipole moment and polarization ability of the system and wax molecule,and some particles attract each other,which changes the dispersion ability of the particles within the whole system and reduces the viscosity.In addition,it is concluded that the increase of diffusion coefficient of long-chain wax molecule at low temperature is significantly greater than that at high temperature through the change of temperature,which explains the great effect of viscosity reduction at low temperature.Finally,the effects of asphaltene and temperature on the dissolution and diffusion of wax clusters in multiphase system under external electric field were investigated by constructing wax clusters.The aggregation degree between long-chain wax molecule decreases gradually,the Van der Waals interaction energy decreases gradually with increasing temperatures,applying 1.50 wt%amount of asphaltenes,and also with a 1.6V/nm electric field.Suggesting that the solubility between wax and heterogeneous system increases continuously,and large clusters dissolve into small clusters,which improves its fluidity.