| Responsive emulsion refers to the emulsion which can get to de-emulisification state rapidly after exposing the external stimulus,such as pH,light or magnetism.In many processes of actual production,the emulsion need to be stable in the early stage,but break into two state rapidly in the later stage,such as transportation of crude oil.Therefore,it is extremely crucial to study the main factors which affect the emulsification and de-emulsification of the responsive emulsion systematically.Switchable surfactants are always used to prepare the swichable emulsion,but the synthesis process is complex and has a lower productivity.In recent years,a relatively simple way has been used in some studies,and without complex synthesis,the same emulsification and demulsifaction processes can be equally achieved.Some studies use fatty acid and CO2 switchable solvent to form the CO2-switchable emulsion.The other one is to use traditional anionic surfactant and CO2-switchable solvent,traditional anionic surfactant is used as emulsifier before bubbling of CO2,after bubbling of CO2,tertiary amine is protonated and combined with surfactant,traditional anionic surfactant lose its function as the emulsifier,and the system demulsify into complete two parts.So the selection of amine is considerably important.Based on this,the first part of this paper selects a series of different alkane carbon number of tertiary amine and a traditional anionic surfactant sodium dodecyl benzene sulfonate(SDBS)for study,and than the stability and demulsification of the system before and after bubbling of CO2 which affected by the tertiary amine are compared systematically.First,by using interfacial tension,water separated rate and the change of particle size of the emulsion droplets to characterized the stability of the emulsion system,proving that because a very small amount of tertiary amine has been protonated into corresponding tertiary ammonium bicarbonate in the process of mixed with water,it inserts into the arrangement of SDBS which has already arranged on the oil-water interface,and this tertiary ammonium bicarbonate can enhance the stability of the emulsion.After bubbling of CO2,the tertiary amine is protonated into tertiary ammonium bicarbonate quickly and completely,and combined with SDBS by electrostatic interaction,and formed the new ion pair.The SDBS has a hydrophobic property because of the long alkane carbon number.And the longer the carbon chain length of tertiary ammonium bicarbonate has,the easier for the ion pairs formed by SDBS and tertiary ammonium bicarbonate to separate from water phase,this conclusion can be proved by the interfacial curve.With the increase of the alkane carbon number,the change of interfacial tension before and after bubbling of CO2 are increase obviously,which indicates that the content of separated ion pairs formed by tertiary amine and SDBS are much more,and further indicates the emulsion are also easier to demulsify.By using of UV-vis,the corresponding content of separated ion pairs is also figured out,which also prove the effect of alkane carbon number of the tertiary amine of the emulsion is obviously.At last,the mechanism of tertiary amine and SDBS after bubbling of CO2 is prove by zeta potential and microscope,so the control of the switchable property of switchable emulsion is acieved.And then the different functional groups of amine with a traditional anionic surfactant,sodium oleate(NaOA)are selected for study,and the stability and demulsification of emulsion system after mixing amine are also researched.The PMA is used as example,proving that the emulsion after mixing PMA is more stable and easier to de-emulsify after bubbling of CO2.Then the responsiveness of the NaOA,PMA and NaOA/PMA in the condition of CO2 are studied,the result shows that they both response to CO2,and have a god solubility,but when mixed PMA and NaOA together with bubbing of CO2,the insoluble substance with light yellow is formed and separated from water phase.By 1H nuclear magnetic method,the mechanism of PMA and NaOA after bubbling of CO2 is proved,some water soluble amine can also form ion pair after bubbling of CO2,and the corresponding emulsion turns into demulsification state entirely.So the functional group of amine is a very important parameter for the selection.And than by choosing three teams amines containing different functional groups,through comparing the change before and after bubbling of CO2,the functional groups have an enhanced effect on the stability of emulsion is proved,and the emulsion with the amines contains the hydroxyl group are the best because of its strong water-soluble effect.After bubbling of CO2,the amines with different functional groups have different effects on demulsification,which means that the different structure of amine is an important reason for the demulsifaction of the emulsion.Finally,after the comparasion,the de-emulsifacation effect of amine with different carbon chain number is better than the effect of the functional group of amine.Therefore,the initial research of the application of CO2-responsive emulsion in crudre oil is conducted,proving that this kind of CO2-responsive emulsion can emulsify effectively and demulsify rapidly when the oil phase is crude oil.It is proved that the choice of CO2 switchable solvent can control crude oil emulsion effectively,and the system can be used to emulsify and demulsify rapidly of crude oil. |
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