Study On The Removal Of Benzenic Volatile Organic Compounds With Ionic Liquids

In recent years,the air quality in China has been improved to a large extent on the whole,but at present,the emission of Volatile Organic compounds（VOCs）is still at a high level.Besides,VOCs released from industrial activities are on the rise,causing great harm to the environment and human health.Among the VOCs treatment methods,liquid absorption is mature,economical and widely used,and the key is utilization of the absorbent with high solubility and stability.As a new type of green solvent,ionic liquid was widely used in gas separation.In this work,a customer-designed absorber was used to study the ability of ionic liquid to efficiently absorb benzenic VOCs.Combined with traditional organic solvents,a mixed absorbent of ionic liquid and ethylene glycol（EG）was prepared and its toluene absorption performance was studied.Three imidazolium hydrophobic ionic liquids,1-ethyl-3-methylimidazole-bis（trifluoromethyl sulfonyl）imide salts（[Emim][Tf₂N]）,1-butyl-3-methylimidazole-bis（trifluoromethyl sulfonyl）imide salts（[Bmim][Tf₂N]]）and 1-octyl-3-methylimidazole-bis（trifluoromethyl sulfonyl）imide salts([Omim][Tf₂N],have been studied by single factor method.The results showed that the toluene absorptivity by ionic liquid decreases with the increase of N₂ intake rate or absorption temperature.And with the increase of ionic liquid flow rate,the absorption of toluene in the ionic liquid increased firstly and then becalmed stable.In addition,the toluene absorptivity of these three ionic liquids was more than 90%.Under the same experimental conditions,as the length of cationic carbon chain of ionic liquid increased,the toluene absorptivity increased in the order of[Omim][Tf₂N]>[Bmim][Tf₂N]>[Emim][Tf₂N].The toluene absorptivity by[Omim][Tf₂N]remained above 97%when the absorbed ionic liquid was regenerated 5times after vacuum drying at 140℃for 5 h,which showing good regeneration performance.In order to reduce the cost of ionic liquid,the toluene absorption properties by the mixed[Omim][Tf₂N]and EG（[Omim][Tf₂N]:EG=1:n）were studied.The results showed that the mixed absorbent can effectively absorb toluene and there was a synergistic effect between them.However,with the increase of EG content,the synergistic effect weakened.The toluene absorptivity with mixed absorbent[Omim][Tf₂N]:EG=1:1,can reach 98.45%.Compared with the pure ionic liquid,the mixed absorbent had a better economic advantage.The industrial scale toluene removal processes by[Omim][Tf₂N]and EG were simulated by using Aspen Plus software.The differences in absorption efficiency,energy consumption and economy of the two processes were compared.The simulation results showed that the solvent cost of[Omim][Tf₂N]was higher than that of EG under the same toluene removal rate.But the energy consumption of[Omim][Tf₂N]was lower than EG.The study provided a new idea for dealing with VOCs,and some theoretical support for industrial practical application.