| Surfactants,because of their excellent surface activity,were widely used in many areas,such as oil exploitation,commodity industries and textile industry.However,it is very hard to achieve oil-water separation by using traditional surfactant.And it was discharged into the environment after it was used,which caused resource waste and environmental damage in a certain degree.In this thesis,we synthesized a CO2/N2 switchable Gemini cationic surfactant with a new structure.The synthesized surfactant can be separated after using or loss its surface activity,and easily realized the oil-water separation.In the process of its use,it neither cause the environmental pollution,nor introduce other impurities to the system.In this paper,ethylenediamine,decanoyl chloride,lauroyl chloride,myristoyl chloride and N,N-dimethyl-3-chloropropionic amine were employed to synthesize two kinds of CO2/N2 switchable surfactants,N,N'-dialkyl ethylenediamine diacetamidine(CnEA n=10,12.14)and N,N'-di(N,N-dimethyl amine)-N,N'-didodecyl ethylenediamine(C12MAEd).And then,the target products,N,N'-dialkyl ethylenediamine diacetamidinium bicarbonate were obtained by reacting with a large number of dry ice.The optimal reaction conditions of diacetamidine were determined by the single factor,and the optimal reaction conditions of C12MAEd were optimized by using the orthogonal experiment.Finally,the intermediate products and the target products were characterized by FTIR spectrum and 1H-NMR spectrum.The results indicated that the products were the desired.The performances of four kinds of surfactants were characterized in this study.The results showed that the Krafft points of the three kinds of amidine group surfactants were low,so them exhibited good water solubility;The critical micelle concentration of C10EAB,C12EAB,C14EAB and C12MAEd were 2.37×10-4mol/L,1.68×10-4mol/L,1.25×10-4mol/L and 3.76×10-4mol/L,respectively.The ?cmc of C10EAB,C12EAB and C14EAB were gradually decrease from 28.8mN/m to 24.9mN/m,while the value of ?cmc increased slightly when the carbon chain was C14,and the value of ?cmc was 27.8mN/m.The values of CMC and ?cmc were all less than traditional cationic and anionic surfactant,namely N,N,N-trimethyl-l-dodecanaminium bromide and 1-dodecane sulfonic acid sodium salt,which showed higher surface activity.At the same time,the results of other surface active parameters(pC20,?max,Amin)stated that these four kinds of surfactants had strong adsorption on gas-liquid interface and high efficiency in reducing surface tension.The test of foam properties indicted that all the four kinds of surfactants had the good foaming ability and foam stability.Emulsification-demulsification experiments showed that amidine switchable surfactants had good emulsification-demulsification to liquid paraffin.We verified the switchability of CO2/N2 trigger by testing the surface tension,electrical conductivity,Zeta potential and foaming volume when the CO2 and N2 were bubbled into the solution.The results showed a law that with the CO2 and N2 were bubbled into the solution circularly,the surface tension decreased first and then increased,the electrical conductivity,absolute value of Zeta potential and the foaming volume increased first and then decreased.All the experiments confirmed that four kinds of surfactants had switchability and reversibility during injecting CO2 or N2.In addition,we discussed the physicochemical properties and CO2/N2 switching properties advantages and disadvantages of two kinds of CO2/N2 switchable surfactants which with the same carbon chain length.The results showed that amidine CO2/N2 switchable surfactants was superior to tertiary amine CO2/N2 switchable surfactants;but the reversibility of tertiary amine CO2/N2 switchable surfactants was better than amidine CO2/N2 switchable surfactants. |
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