Study On Influence Of Resins And Asphaltenes On Gelation Of Waxy Model Oils

Dissolved wax precipitating out from liquid oil can generate bad impacts on the flowability of waxy oils.In the worst scenario,the precipitated wax can form gelled structures at low ambient temperature,which can cause a variety of issues for the safe transportation of waxy oils.Resins and asphaltenes as two heavy components of oils can affect the crystallization and gelation of waxy oils.However,the investigations on the influence mechanism of resins on gelation of waxy oils are relatively rare,and the literatures on the effect of asphaltenes on gelation of waxy oils still contain conflicting views.In the present work,the commercial wax?Wax A?and n-tetracosane?Wax B?were used to formulate two types of model oil,namely model oil A and model oil B.The influence mechanisms of resin content,resin polarity,and asphaltene content on gelation of waxy model oils have been conducted by studying the wax precipitation and the structure strength of wax crystal.The influence of wax composition on the efficiency of the resins and asphaltenes affecting gelation and crystallization has been conducted as well.Firstly,the influence of resin content on gelation of waxy model oils was explored.In the scope of the testing concentration?0.0?7.0 wt%?,both the gelation temperature and yield stress of model oils decreased monotonously with the increase of the resin content.Up to 8.0°C and 70%of reduction in gelation temperature and yield stress were achieved when the model oil A contained 7.0 wt%resins.And up to 4.5°C and 85%were achieved for model oil B.Resins suppress wax precipitation and decrease structure strength of wax crystal,which collectively lead to lower gelation temperature and lower yield stress of model oils.The defects of wax crystals may be responsible for the weaker strength of model oils,whereas the variation of wax crystal morphology plays a minor role.Then,the influence of resin polarity on gelation of waxy model oils was studied further.Resins were fractioned into three subfractions,namely Resins1,Resins 2,and Resins 3?polarity increases in turn?,which were used to formulate model oils with Wax A and Wax B respectively.With the increase of polarity,the unsaturation of resin subfraction increases and aggregation state remains unchanged.In the scope of the testing concentration?0.0?7.0 wt%?,both the gelation temperature and yield stress of model oils decreased monotonously with the increase of resin content and decrease of resin polarity.Resins 1,which consists of 3 fused aromatic rings constructed by N₁,N₁O₁ and N₁S₁ class species,owning the lowest polarity decreased the gelation temperature and yield stress of model oils most.Up to 9.4°C and 66%of reduction in gelation temperature and yield stress were achieved when the model oil A1?Resins 1-Wax A?contained 7.0 wt%Resins 1.And up to 6.4°C and 89%were achieved for model oil B1?Resins 1-Wax B?.The difference of efficiency of resin subfraction in decreasing the gelation temperature and yield stress derives from the different effect of resin subfraction on suppressing wax precipitation and decreasing structure strength of wax crystal.The morphology of wax crystal is not the primary cause of the difference of flowability improvements caused by different resin subfractions.The unsaturation of resin subfraction may be partially related to the efficiency of resin subfraction decreasing the gelation temperature,yield stress and WAT.The species and the aggregation state of resin subfraction have no influence on that.All of the species,the unsaturation and the aggregation state of resin subfraction are not the major factors for the morphology of wax crystal.Finally,the influence of asphaltene content on gelation of waxy model oils was researched.In the scope of the testing concentration?0.000?0.070 wt%?,adding asphaltenes had no influence on the gelation temperature of the model oil A,whereas sharply increased the one of the model oil B.Asphaltenes promote wax precipitation and decrease structure strength of wax crystal,the former of which is the major factor for the increase of gelation temperature.Adding asphaltenes sharply increased the yield stress of both model oil A and model oil B at 8?.Asphaltenes promoting wax precipitation and increasing structure strength of wax crystal are collectively responsible for higher yield stress of model oils.All of the change of morphology of wax crystal,wax crystal particle and defect of wax crystal are not the primary causes of variation of structure strength of wax crystal.The effects of resins and asphaltenes on gelation temperature,yield stress,crystallization depend on wax composition of model oils.