Nonaaqueous Lyoltropic Ionic Liquid Crystals:Preparation,Characterization,and Application In Extraction

Liquid-liqud extractive separation is an essential process in chemical separation fields.In recent years,ionic lqiuds?ILs?with their special physical and chemical properties are widely applied in liquid-liquid extractive separation process and they have also achieved a lot of improvements in extractive efficiencies compared to common organic solvents extractants.However the affinity between ILs and some nonpolar solutes is hindered by the innate stronger polarity of ILs which is stem from their ionic structure.As a result,it is hard to get high level of distribution coefficient and capacity of solutes to satisfy the ever-increasing need in extractive separation fields.Herein a series of long chain carboxylate ILs which have strengthen hydrogen basicity,stronger lipiphility and ability of self-aggregating were synthesized and used to develop a novel nonaqueous ionic liquid crystal extractants.On that basis,a novel extractive separation method with brilliant extractive performance,e.g.higher distribution coeffient,larger extractive capacity,accurate selective recognition and convenient recovery,was build for some liposoluble compounds.A series of long chain carboxylate ionic liquids were synthesized and their self-aggregation performance in nonaqueous solvents were investigated concerning the effects of structures of their anions and cations,types of solvents.And it was found that ILs of[Ch][C12OO],[Ch][C14OO],[N2222][C12OO],[Emim][C12OO]and[OHemim][C12OO]with shorter substituents on cations can form various types of lyotropic liquid crystals?e.g.Cubic phase,hexagonal phase and lameller phase?in nonaqueous solvents of acetonitrile,DMSO,DMF and methanol.And cations like[P4444]+ will eradicate the formation of lyotropic liquid crystal because of their bulk spatial size of cation.However carboxylate anions with longer alkyl chain would be in favor of the presence of lamellar phase.The novel nonaqueous lyotropic ionic liquid crystal,for the first time,was applied in the extractive separation of natural tocopherol homologues and the influences on their extractive performance caused by structures of ILs,amount of ILs and solvents were systematically investigated.And the novel extractants provided more powerful extractive ability for tocopherol homologues than the existing extractans.The distribution coefficients of nonaqueous ionic liquid crystal extractans for tocopherols reached the unprecedented values of 50?60 at very high feed concentrations?100 mg/mL?,which are 800-1000 times greater than those of common ILs,traditional organic solvents,polymer extractants and mixtures of ILs/cosolvents.As for mechanism of this novel extractive separation methods,solvatochromism,IR,XRD and POM were used to illustrate to explain their brilliant extraction performance.The results is that the long chain carboxylate anions of ILs can interact with tocopherols through hydrogen bond ineraction,meanwhile liquid cystal aggregation in extractants will provide numerous polar/nonpolar microenviroments which induced the incorporation of tocopherols in the palisade layer of liquid crystals.Both of the two effects ensured the highly effective extractive ability and strenthgen selective recognition of different homologues.Besides,after adding certain amount of solvents to the extractant phase to interrupt the aggregations,ILs can be easily separated from solutes.The novel nonaqueous lyotropic ionic liquid crystal extractants also showed excellent extraction capacities for other H-bond donor compounds,such as oleic acid,naphthenic acid,phenol and sudanI.The distribution coefficient of oleic acid can reach 400-1900,and the selectivity of oleic acid to olein reached unpreccedent value of 105,which means oleic acid can be precisely recognized by the novel extractants.For naphthenic acid/octane mixtures,the distribution coefficient of naphthenic acid is 9 times higher than common ILs/solvents extractants and the selectivety of naphthenic acid to octane can be larger than 1000.In addition,the novel nonaqueous lyotropic liquid crystal extractants also showed excellent extraction capacity for phenol,the distribution coefficients of phenol are higher than 1200.Since great successes were achieved when using nonaqueous lyotropic ionic liquid crystal as extractants in extractive separation process.Their ability endowed by stronger hydrogen bond basicity and liquid crystal nanostructures were used as solvents and templates to synthesize nitrogen-doped porous carbon materials,and a series of porous nitrogen-doped carbon materials with varied morphologies were synthesized.The BET specific surface area of those nitrogen-doped carbon materials range is 252?551 m2/g.And the total nitrogen?pyridinic type and pyrrolic type?amount reached 2.63?11.2 wt%.The uptake amount of materials to CO₂ can be 1.8 mmol/g.