Experimental Investigation Of Furoate-based Ionic Liquids And Dipolar Solvents For Capturing SO₂

Sulfur dioxide?SO₂?emitted from the burning of fossil fuels has caused evident harm to atmosphere and human health.Wet limestone method is the most widely used flue gas desulfurization?FGD?technology nowadays.However,it has the main drawback of producing usefulness byproduct of CaSO4.As the frontier and hot spot of green chemistry,ionic liquids?ILs?has also shown significant scientific value and tremendous utilization potentiality in FGD.Meanwhile,the gradual exhausting of petrochemical resources has transferred people's attention to the renewable resources.Therefore,developing and applying ILs from biomass for capturing SO₂ are consistent with the concept of sustainable development.2-Furoic acid is a biobased compound with high boiling point,appropriate pKa value and multiple interaction sites with SO₂.Hence,2-furoic acid and its derivative of 5-bromo-2-furoic acid were chosen as the materials to prepare serials of furoate-based functional ILs.Physical properties and SO₂ capturing performances of these ILs were further investigated.Among them,[P4442][FA] possess low viscosity?82.0 mPa·s?,high thermal decomposition temperature?289??,outstanding capturing capacity of SO₂?3.70 mol SO₂ / mol IL,0.69 g SO₂ / g IL?which could be achieved very fast during the absorption process,good selectivity of SO₂/CO₂?37?,SO₂/N2?114?as well as good regeneration.Spectroscopic investigations indicated that the carboxyl group in the furoate anion existed chemical interaction with SO₂,even had the synergistic absorption of SO₂ with the oxygen atom in the furan ring.At the same time,the absorption capacity was enhanced by the ????S interaction and S=O/H-C hydrogen bonding interactions between the furan ring and SO₂.Subsequently,environmentally friendly solvent of PEG200 was chosen as diluent for solid [N2222][FA] and highly viscous [Ch][FA] to obtain the hybrid absorbents for SO₂.Physical properties and the solubility of SO₂ in these absorbents at 303.15³33.15 K,0¹.2 bar were determined.By correlating experimental data with the reaction equilibrium thermodynamic model?RETM?,results were obtained as following.Chemical absorption was dominant at low pressure range,while physical absorption was dominant at high pressure range.Meanwhile,[N2222][FA] had stronger interaction with SO₂ than [Ch][FA].[N2222][FA]/PEG200 binary mixture possessed high absorption capacity?5.96 mol·kg-1?,low absorption enthalpy and good recycling ability.In searching for diluents,the solubility of SO₂ in three dipolar solvents,DMI,DMPU and TMU with high boiling points and low viscosities,were determined at 303.15³33.15 K and 0¹.2 bar.Results showed that they had relatively high absorption capacities of SO₂?approximately 14 mol·kg-1?.By correlating the solubility results with RETM,the enthalpy of the absorption processes were obtained,which showed that all the above dipolar solvents had low absorption enthalpy,and physical interactions were dominant during the absorption processes.Finally,a FGD process was simulated using Aspen plus with the absorbent of [P4442][FA],DMPU and [N2222][FA]/PEG200.The results showed that [N2222][FA]/ PEG200 binary mixture could decrease the SO₂ volume fraction in flue gas from 3500 ppm to 35 ppm with a mass flow rate of 60603 kg·h-1 of absorbent,when an initial condition of wet flue gas was at 80? and 4000 m3·h-1.