Experiental Study On The Capture Of SO₂ And CO₂ In Biobased Absobents

Sulfur dioxide?SO₂?and carbon dioxide?CO₂?are major acidic gases of atmospheric emission from the combustion of fossil fuels.CO₂ is main greenhouse gas causing global warming;SO₂ is responsible for the formation of smog and acid rain.Climate change and environmental pollution seriously affect human production and life.Nowadays,amine solutions and lime/limestone were used to remove CO₂ and SO₂ in the industry,respectively.Despite their low price,high efficiency and large capacity,these absorbents still suffer from several drawbacks such as the large production of secondary pollutant,intensive energy consumption and equipment corrosion.Therefore,developing renewable,inexpensive,efficient absorbents for SO₂ and CO₂ is in demand.In present work,biobased solvents?BBSs?were selected including ethyl levulinate?EL?,butyl levulinate?BL?,dibutyl succinate?DBS?,gamma-butyrolactone?GBL?and gamma-valerolactone?GVL?.Two ionic liquids?ILs?of choline levulinate?[Choline][LA]?and choline lactate?[Choline]L?were synthesized.Six deep eutectic solvents?DESs?were prepared including levulinic acid-choline chloride?LA-CC?,levulinic acid-choline acetyl chloride?LA-CAC?,levulinic acid-tetraethylammonium chloride?LA-TEAC?,levulinic acid-tetrabutylamonium chloride?LA-TBAC?,levulinic acid-tetraethylammonium bromide?LA-TEAB?,levulinic acid-tetrabutylamonium bromide?LA-TBAB?.The physicochemical properties of abovementioned three absorbents were determined in detail and capture properties of those absorbents for SO₂ and CO₂ were systematically investigated.Thermodynamic parameters were calculated by correlating the experimental data using models with corresponding conclusions as follows,?1?Five BBSs demonstrated good absorption capacities for SO₂ and CO₂.Henry's law constants?Hm?of CO₂ in EL was 0.72 MPa at 303.15 K,means that EL possessed better absorption capacity for CO₂ than NHD?1.05 MPa?.Hm of SO₂ in GBL was 12.51 kPa,means that GBL was superior to common ILs.The solubilities increased linearly with the increasing partial pressures or decreasing temperatures.GBL and GVL with the structure of ring-lactone had high dissolving ability for SO₂,while straight chain-esters of EL and BL possessed better absorption capacity for CO₂ among the five BBSs.?2?ILs/PEG-200 possessed relatively large absorption capacity for SO₂,with the solubilities of SO₂ in [Choline][LA]/PEG-200 at 303.15 K as high as 0.1181 g·g-1?4.0 kPa?,0.4638 g·g-1?100.0 kPa?.Reaction Equilibrium Thermodynamic Model?RETM?could be applied to quantitatively correlate the experimental solubility data in order to obtain Henry's law constants?H?and reaction equilibrium constants?K0?.With the raising of temperature,the H goes higher and K0 shows lower,which indicates that lower temperatures will facilitate the absorption process.?3?DESs had the advantages of simple synthesis process,low viscosity,high absorption capacity for SO₂ and selectivities of SO₂/CO₂.According to the analysis of NMR and FT-IR spectrum,the absorption of SO₂ and CO₂ in DESs was a physical process.The absorption capacity of SO₂ in DESs mainly depended on quaternary ammonium anions,DESs with bromide ions processed higher ability than those with chloride ions.DESs absorption capacity for CO₂ mainly depended on the cations,the tetrabutylammonium salt-based DESs processed higher absorption capacity than the tetraethylammonium salt-based ones.?4?With biobased chemicals as start materials,three types of absorbents had good biodegradability.They were regarded as promising absorbents for SO₂ and CO₂ due to their low absorption enthalpy,good recycling properties,low energy consumption and viscosities.On the basis of experimental research,the capture processes of SO₂ and CO₂ from flue gas was simulated by ASPEN software with LA-CC and EL as absorbents.It demonstrated that the removal efficiency was as high as 98%;High liquid-gas ratios?L/V?and low temperature of EL were helpful for capturing CO₂ from flue gas;The removal efficiency??CO₂?and energy consumption of compressor increased with increasing pressure of absorption column?p?;?CO₂ was approximately 58% at L/V=14,p=3.6 bar.