Synthesis And Performance Of A Series Of Imidazole Ionic Liquid Surfactants

Ionic liquid has the characteristics of low toxicity,no corrosion,harsh environment resistance and strong structure adjustable,so it has a broad application prospect as oil displacement agent in enhancing oil recovery.In this paper,imidazole,2-methylimidazole,benzimidazole,2-methylbenzimidazole,brominated alkanes,etc.were used as raw materials to synthesize ionic liquid surfactants with the aid of microwave.The process conditions of the series products were optimized through single factor experiment and orthogonal experiment.Fourier infrared spectroscopy,hydrogen nuclear magnetic resonance spectroscopy,and high-resolution mass spectrometry were used to characterize the structure of the synthesized product,and the surface/interface performance of the product was evaluated,including critical micelle concentration（CMC）,interfacial tension,and Wetting performance and emulsification performance,etc.Finally,the structure-activity relationship of the molecule was summarized through experimental results.The experimental results show that the optimal process conditions for the intermediate synthesis reaction of the nonsubstituted imidazole series product[C12-n-C12im]Br₂ are:reaction temperature 50℃,reaction time 9min,microwave reactor power 400w,and feed ratio1:2.Under these conditions,the yield was 88.49%.For the substituted imidazole series products,[C12-2-C12-2-Mim]Br₂、[C12-2-C12Bim]Br₂、[C12-2-C12-2-MBim]Br₂,synthesized by 2-methylimidazole,benzimidazole and 2-methylbenzimidazole,the optimal synthesis conditions determined by taking[C12-2-C12Bim]Br₂ as an example:reaction temperature 50℃,The reaction time is 5min,the microwave reactor power is 400w,and the feed ratio is 1:1.1.Under this process condition,the total yield of[C12-2-C12Bim]Br₂ product is 49.15%.The chemical structure of synthesized molecular structure is consistent with the designed target product molecular.For Gemini-type imidazole products,the CMC value of[C12-4-C12im]Br₂ is smaller than[C12-2-C12im]Br₂,but the reduction in surface tension value[C12-4-C12im]Br₂ is slightly smaller than[C12-2-C12im]Br₂.In terms of reducing oil-water interfacial tension and emulsification performance,[C12-4-C12im]Br₂ is better than[C12-2-C12im]Br₂.The contact angles of the two products are similar,and the difference in wettability is small,indicating that the increase in the number of carbon atoms in the linking group can reduce the CMC of the solution and effectively improve the surface properties of the product.For Gemini-type substituted imidazole products,the cationic head group structure affects the surface/interface activity.The introduction of aromatic rings is beneficial to reduce CMC but not conducive to reducing surface tension.The CMC of[C12-2-C12-2-Mim]Br₂ is much greater than[C12-2-C12Bim]Br₂ and[C12-2-C12-2-MBim]Br₂,and[C12-2-C12-2-Mim]Br₂also reduces the surface tension value more than[C12-2-C12Bim]Br₂ and[C12-2-C12-2-MBim]Br₂.Among the three Gemini ionic liquid surfactant products derived from substituted imidazoles,[C12-2-C12-2-Mim]Br₂ has the best ability to reduce oil-water interfacial tension,the oil-water interfacial tension between Daqing crude oil and the oil displacement system can be reduced to 0.00727m N/m.[C12-2-C12-2-Mim]Br₂ has similar advantages in terms of wetting performance and emulsifying performance.With the gradual increase of the solution concentration,the wetting angle of[C12-2-C12-2-Mim]Br₂ decreased most obviously,and its emulsifying power value was 42.8%.