Application Of CETSA-based Ionic Liquids

Due to the rapid development of economy and technology,people pay more and more attention to environmental protection and resource conservation.Ionic liquids,which have the characteristics of low vapor pressure,good thermal stability,designable structure and non-toxicity,have attracted extensive attention in many fields of application research.At present,cations play a leading role in the design and use of ionic liquids,while anions fail to play a full role.Therefore,this paper chooses carboxylethyl thiocarbobutyric acid（CETSA）containing three carboxyl groups as anion to synthesize a series of ionic liquids with different cations to observe the performance of CETSA-based ionic liquids in the application of corrosion inhibition and catalysis.Relevant research contents and conclusions are as follows:First,three kinds of corrosion inhibitors for mixed ionic liquid system were synthesized by adding different proportions of N-butyl imidazole and CETSA,named ILHS₁,ILHS₂and ILHS₃.Due to the regional selectivity of the three carboxyl groups on CETSA,the structures of the three mixed ionic liquid systems were determined by ¹H NMR analysis.By weight loss method,electrochemical impedance method,scanning electron microscope and contact angle test,it was proved that the three ionic liquid corrosion inhibitors had excellent corrosion inhibition performance.Among the three ionic liquid systems,ILHS₂had the best corrosion inhibition performance.Under the situation of adding 10m M ILHS₂to 1M HCl and soaking the measured iron sheet at 308 K for 24 hours,the corrosion inhibition efficiency could reach90.63%.The polarization curve showed that the mixed ionic liquid system can inhibit the corrosion of the two poles,namely,the anions and cations could cooperate with each other and even anions dominate.Meanwhile,the adsorption isotherm conformed to the Langmuir adsorption law.Combined with the molecular dynamics simulation,the adsorption mechanism between the inhibitor molecules in the ionic liquid mixed systems and the iron surface had been deeply studied at the atomic scale.It was proved that ILHS₁,ILHS₂and ILHS₃are mainly mixed adsorption based on chemical adsorption on the metal interface.Furthermore,in the equilibrium configuration simulated by molecular dynamics,the corrosion inhibitor had higher adsorption energy than water and HCl,which proved that the three kinds of corrosion inhibitors could be more stable adsorption on the surface of iron sheet.Secondly,CETSA and basic cations were selected to synthesize a variety of hydrophilic ionic liquids.Anions and cations could synergically capture and activate hydrogen sulfide gas molecules to promote the preparation ofβ-mercaptopropionic acid addition reaction.Combining the catalytic effect and economic cost,eight kinds of ionic liquid catalysts with better performance were selected:[TMHDAH]CETSA,[TMPDAH]CETSA,[TMEDAH]CETSA,[DBNH]CETSA,[DBUH]CETSA,[DEAPAH]CETSA,[TMGH]CETSA and[NEt₃H]CETSA.The structure and properties of the ionic liquid were characterized by ¹H NMR,¹³C NMR,TG,differential scanning calorimetry（DSC）,high performance liquid chromatography-mass spectrometry（HRMS）and infrared spectroscopy（IR）.The analytical results confirmed the successful synthesis of ionic liquids.Using acrylic acid and hydrogen sulfide as raw materials,the catalytic effect of hydrophilic CETSA-based ionic liquid was investigated.The reaction conditions were as follows:The amount of acrylic acid was 2.16g,the solvent was tetrahydrofuran,sufficient hydrogen sulfide was generated in situ instead of the traditional gas cylinder,various ionic liquid catalyst was 3mmol,the reaction temperature was 363k in the hydrothermal synthesis reactor,the reaction time was 4.5h,and the samples were then sampled and analyzed by liquid chromatography.Under the action of the above ionic liquid catalysts,the conversion of acrylic acid could reach 95%,the selectivity of the target product could reach 85%with the yield could reach 90%.Taking[TMPDAH]CETSA and[DBNH]CETSA as examples,the conversion rate of acrylic acid under their action was 99.21%and 100%,the product selectivity was 92.57%and 90.57%,the yield could reach 91.84%and 90.57%,and the recycling for 7 times still had a high activity.