Synthesis And Performance Evaluation Of Tertiary Amine CO₂/N₂ Switch Gemini Surfactants

Traditional surfactants have excellent properties,but they are difficult to recover,even pollute the environment,which is not conducive to the green and sustainable development of resources.The tertiary amine CO2-Responsive Gemini surfactant synthesized in this paper can be recycled after use,which saves cost,reduces the harm to the environment and achieves the goal of environmental protection.Three kinds of tertiary amine CO2-Responsive compound,N,N'-dimethyl N,N'-bis-dodecyl ethylenediamine,N,N'-dimethyl N,N'-bis-tetradecyl ethylenediamine and N,N'-dimethyl N,N'-bis-decadecyl ethylenediamine,were synthesized by two-step method from bromoalkane(bromododecyl,bromotetradecane and hexadecane bromide),ethylenediamine,formic acid and formaldehyde.Hexadecyl ethylenediamine was reacted with CO2 to prepare corresponding bicarbonate surfactants.The TSP process was simulated by Material Studio 2017 software,and the feasibility of the reaction was verified theoretically.The reaction time and temperature were optimized by orthogonal test.The optimum synthesis conditions of N,N'-dimethyl N,N'-bis-dodecyl ethylenediamine were determined.The structures of intermediate and final products were characterized by FTIR and 1H NMR.A series of surface-interface properties of three tertiary amine CO2-Responsive surfactants were studied in this paper.The results showed that the effective cationic contents of C12DE,C14DE and C16DE were 86.2%,83.7%and 82.1%respectively after the introduction of CO2;the turning points of DSC curves of C12DE,C14DE and C16DE were 60.2,62.2 and 64.7? respectively;With the increase of carbon chain length,the hydrophobicity of surfactants becomes stronger,the surfactant molecules are easier to aggregate and saturate,and micelles can be formed at lower concentration.C12DE.CI4DE and C16DE showed better surface activity with 30.42,30.61 and 33.30 mN/m,respectively;the saturated adsorption capacity of the three CO2-Responsive surfactants increased with the increase of carbon chain length,the minimum value of C16DE and the higher value of pC20 of C12DE indicated that their aggregation efficiency was relatively high,and their ?Gmic0 and ?Gads0 was negative,indicating that C12DE could spontaneously form micelles or adsorb.The Krafft point of surfactants tends to increase with the increase of carbon chain length,but its values are low,almost all near 0?,indicating that the surfactants have good low temperature solubility,that is to say,the surfactants can be used at low temperature.Emulsification experiments show that C12DE,C14DE and C16DE surfactants increase with the increase of carbon chain length.The time of water splitting decreased,because with the increase of hydrophobic chains,the ability to escape from the aqueous phase increased,and the tightness of the gas/liquid boundary film decreased.Foam performance tests showed that C12DE,C14DE and C16DE three kinds of CO2-Responsive surfactants had good foaming ability and foam stability.The DPD simulation results were very close to the critical micelle concentration calculated in our experiment.The experimental results are confirmed theoretically.The CO2-Responsive reversibility was verified by measuring the surface tension,Zeta potential,particle size distribution and foaming volume of the three CO2-Responsive surfactants.The results show that the surface tension of the three CO2-Responsive surfactants decreases,the absolute Zeta potential increases,the droplet size of CO2-Responsive surfactants droplets decreases and the foaming volume increases after the introduction of CO2.When N2 is added,the surface tension increases,the absolute Zeta potential decreases,the droplet size of CO2-Responsive surfactants increases,and the foaming volume decreases.Repeated injection of CO2 and NZ,which confirmed the responsive repeatability of CO2-Responsive surfactants.