| Traditional separation technologies such as extraction,distillation,evaporation and other processes were not only energy-intensive,pollution-intensive,but also cumbersome.The new green solvents-CO2/N2 switchable solvents developed in recent years could avoid the disadvantages of the traditional separation technology.The CO2/N2 switchable solvents was a smart,controllable green solvent.It was unique in that it could change the polarity,hydrophilicity and ionic strength of the solvents through simple CO2/N2 regulation.Using this feature,it was possible to simply achieve lipid extraction in natural products,separation and purification of chemical reaction products,and recycle of solvents.It was a typical green separation process and had a very broad application prospect in separation.However,the CO2/N2 switchable solvents technology still needs further research in solid waste oil treatment,oil plant extraction and organic amine separation to meet the developing of CO2/N2 switchable solvents technology.This article will conduct research on the green separation of switchable solvents.The main research contents are as follows:Firstly,mixed solvents system of tertiary amine salt solution and switchable hydrophilicity solvents was constructed using three kinds of tertiary amines such as triethylamine,N,N-dimethylbutylamine and N,N-dimethylcyclohexylamine and their salt solutions,and the cleaning performance of simulated oily sludge was studied.The performance of the mixed solvent system for cleaning oily sludge was studied.The effect of the mixed system on the treatment of oily sludge was studied.The study found that the mixed solvents system could removed 97.9%of the oil in the oil sludge,and could recovered 94%of the oil resources,and reduced the oil content of the cleaned residue to 0.306%.And the recovery properties of switchable solvents was also studied.The study found that the mixed solvent system could reduce the difficulty of recovery of the switchable hydrophilicity solvents,and improved the recovery rate of the switchable hydrophilicity solvents,and increase the recovery rate of the switchable hydrophilicity solvents to 82.6%.The mechanism of the tertiary amine bicarbonate solution in the sludge cleaning process was investigated by Zeta potential,residue wettability and N,S elemental analysis.The study found that the role of organic ammonium salt was adsorbed on the surface of the residue,and increased the wettability of the residue,and improved the cleaning efficiency of heavy component hydrocarbons,and made the cleaning efficiency of oily sludge increased.Next,triethylamine,N,N-dimethylcyclohexylamine,tri-n-propylamine,N,N-dimethyloctylamine,N,N-dicyclohexylmethylamine five kinds of tertiary amines with different LogKow values were used as the switchable hydrophilicity solvents,and the properties of soybean oil extraction with switchable hydrophilicity solvents were studied.The effect of the lipophilicity of the solvents,ie,the n-octanol-water partition coefficient of the tertiary amines,on the extraction efficiency of soybean oil was investigated.Study found that the lipophilicity of solvents had an important influence on the extraction rate of soybean oil.When the LogKow value of the solvents was in the range of 1.5-3.6,the extraction rate of soybean oil was better.When the value was greater than or less than this value,the extraction rate of soybean oil had a great drop.The effects of extraction time,solid-to-liquid ratio(g:mL),ultrasonic time,extraction temperature and the particle size of soybean meal on the extraction rate of soybean oil were also studied.The study found that when the extraction time was 60 min,the ratio of liquid to liquid(g:mL)was 1:3,the ultrasonic time was 20 min,and the soybean oil particle size was less than 0.25mm,the extraction rate of soybean oil was reached up to 95%,and the effect of the extraction temperature on the extraction rate was negligible.The cycle capacity of the switchable hydrophilicity solvents was studied by 1H-NMR and simple CO2/N2 regulation.The study found that the switchable hydrophilicity solvents could be recycled many times without changing its physical properties.And the quality of extracted soybean oil was studied by gas chromatography.It was found that the soybean oil extracted by the switchable hydrophilicity solvents contained almost no solvent residue.Again,with six fatty amines such as triethylamine,N,N-dimethylbutylamine,N,N-dimethylcyclohexylamine,tri-n-propylamine,and N,N-dimethyloctylamine,N-dicyclohexylmethylamine and four aromatic amines such as N,N-dimethylbenzylamine,N,N-dimethylaniline,pyridine and quinoline formed a mixed system of aromatic amines and aliphatic amines.The selective separation performance of aromatic amines and aliphatic amines was investigated using the switchable hydrophilicity solvents technology.The reaction kinetics of fatty tertiary amines with CO2 was studied.The study found that the reaction of aliphatic tertiary amines with CO2 accorded with the first-order reaction kinetics.The first-order reaction kinetic constants were fitted by the pseudo first-order reaction kinetics equation.By studying the protonation time of tertiary amines and combining the reaction kinetics of tertiary amines,the principle of separation of fatty tertiary amines and aromatic amines based on switchable hydrophilicity solvents was studied.The study found that aromatic amines and aliphatic amines had a huge reaction rate difference in the reaction of CO2,so that the two amines could be separated,and the tertiary amine could be recovered through the simple regulation of CO2/N2.The effect of the structure of the fatty amine and temperature on the separation efficiency was studied.It was found that the greater the LogKow value of fatty amines,the worse the separation efficiency;the better the separation effect of DMAN at 40℃,the lower or higher the of this separation efficiency would be drop.The performance of aromatic amines for the recovery of fatty amines was characterized by conductivity cycling and gas chromatography.The study found that the recovered fatty amines had a good switchable performance,and the recovered aromatic amines had no residual fatty amines and had good quality. |
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