Design Of Functional Ionic Liquids And Deep Eutectic Solvents And Their Applications In The Absorption Of Nitric Oxide

Nitric oxide(NO),a main air pollutant,mainly generated from fossil fuel-fired flue gas,is one of the major reasons for many environment problems,such as photochemical smog,which causes harm to the environment and human health.Moreover,NO also plays an important role in the preparation of nitric acid and other nitro-containing chemicals.Therefore,it is important for environment and society to explore a new way to efficiently absorb and recover NO.Ionic liquids(ILs)and deep eutectic solvents(DESs)are widely used in the absorption of acid gases due to their low vapor pressure,good stability and tunable structure.However,the research on the absorption of NO is still infancy.At present,the designed-absorbents are still very limited,and there are some problems,such as difficulty in desorption,low absorption capacity,and lack of data on the absorption of NO with low concentrations.To solve these problems,in this work,several functional ILs and DESs were designed,and the effects of absorption and desorption of NO by these ILs and DESs were investigated.Besides,the mechanisms of the absorption of NO by these ILs and DESs were explored.The major contents and results are as follows:(1)Based on the complexation between Fe2+and NO,ferrous-based IL with[FeC14 2-were designed.The absorption and desorption of NO with low concentrations and the kinetic of the reaction between NO and[Bmim]2[FeCl4]were investigated.Besides,the mechanism of the absorption of NO in[Bmim]2[FeCl4]was studied.The results show that ferrous-based IL has good absorption capacity of NO with low concentrations.The absorption capacity of NO decreases with the increase of absorption temperature,and increases with the increase of NO concentration.However,the absorption of NO by[Bmim]2[FeCl4]does not allow to Henry's law,which indicates that the IL is functional.The Fe2+in[FeCl4]2-is the main chemical active site.[Bmim]2[FeCl4]has good reusability.The reaction between the[Bmim]2[FeCl4]and NO is a quasi first order exothermic reaction.The desorption of NO can be achieved by increasing temperature due to that the reaction equilibrium constant decreases with the increase of absorption temperature.(2)ILs with L-Proline(L-Pro)as anion were designed based on the nucleophilic reaction between secondary amines and NO.The absorption and desorption of NO by L-Pro-based ILs and the mechanism were studied.The results show that the three L-Pro based ILs show good absorption capacity for NO with low concentrations,compared with conventional anions[BF4]-and[Tf2N]-.Besides,it is also indicated that water,as an inert component,does not participate in the reaction between[Ch][L-Pro]and NO.However,the present of water will accelerate the oxidation of NO by O2.The results of ATR-FTIR,1H NMR,UV and DFT calculation indicate that the-NH-in L-Pro is the main absorption site.The absorption of NO by[Ch][L-Pro]is a reversible exothermic reaction.The results also indicate that[Ch][L-Pro]is renewable and has a good reusability.(3)Based on the nucleophilic interactions between both the amine groups and NO and azoles and NO,the ILs composed with amines as cations and azoles as anions were synthesized.The absorption and desorption of NO by ILs were studied.The data show that the absorption capacity of 0.41 vol%NO in all nine ILs at 30? are over 1 mol NO/mol IL,and their viscosities do not exceed 100 mPa-s during the whole NO absorption process.The low viscosity ensures good mass transfer in the absorption process.The molar absorption capacity of[TEPA][Im]for 0.1 MPa NO at 30? is 6.79 mol NO/mol IL,which is the largest absorption capacity reported in the literature.There is no obvious decrease of absorption capacity during at least five cycles of the absorption and desorption of NO indicating that[TEPA][Im]has good reusability and stability.Besides,the absorption mechanism was also proposed by the characterizations of FTIR,UV and 1H NMR.The results show that the N(2)on[Im]-and the-NH-on[TEPA]+are active sites for the absorption of NO.(4)The idea that the absorption of NO with low concentrations by amine chloride-based DESs has been proposed due to that they are cheaper,easier to prepare and have better biodegradability compared with ILs.Amine-based DESs were designed composed with tetraethylenepentamine chloride([TEPA]Cl)and triethylenetetramine chloride([TETA]Cl)as HBAs and 1,3-propanediol(PG),glycerol(Gly),polyethylene glycol 2000(PEG)and ethylene glycol(EG)as HBDs,respectively.The results indicate that all DESs synthesized can effectively absorb NO with low concentrations.There is no obvious influence for water on the intereaction between EG-[TEPA]Cl DES and NO.Moreover,the existence of a proper amount of water in the DES can effectively reduce the viscosity of DES,which is beneficial to increase the absorption rate of NO by DES.The results also indicate that EG-[TEPA]Cl DES has a good regeneration ability.The-NH-groups in[TEPA]Cl are the main chemical active groups for the absorption of NO.There is a strong nucleophilic interaction between-NH-groups and NO.(5)To solve the problem of the high energy consumption for the regeneration of DESs due to the absorption of water during the NO absorption,a series of hydrophobic DESs were synthesized.The hydrophobic DESs are based on imidazole(Im),pyrazole(Py),1,2,4-triazole(Triz)and tetrazole(Tetz)as HBDs and methyl trioctyl ammonium bromide([N8881]Br)and methyl trioctyl ammonium chloride([N8881]Cl)which are hydrophobic hydrophobic quaternary ammonium salts as HBAs.The data show that all DESs have good hydrophobicity before and after the absorption of NO which effectively decrease the amount of water-absorbed during the absorption of NO,and further reduces the regeneration energy consumption of DESs.Im-[N8881]Cl DES can chemically absorb NO and shows good regeneration ability.The N(2)and N(5)on Im are the main active sites.Although[N8881]Cl can not chemically absorb NO,it can increase the reactivity of Im-[N8881]Cl DES on the absorption of NO through hydrogen bondings between chloride ion and H connected to N(2)in Im.(6)A nucleophilic reaction occurs between ketone and NO.According to this reaction,ketone-based DESs were synthesized,which were composed of acetone(Ace)and Zinillone(Zin)as HBDs and[N8881]Cl and[N8881]Br as HBAs,respectively.The results indicate that all DESs synthesized have good hydrophobicity and high absorption selectivity of NO.Besides,the energy consumption for regeneration of DESs is low.The ?-CH2 group attached to the carbonyl group is the main active site for the absorption of NO.The HBA[N8881]Cl can enhance the absorption capacity of NO by DES through the hydrogen bond formed with ?-H and NO.