SO2 Capture Research Articles

Efficient SO2 capture and conversion to cyclic sulfites by protic ionic liquid-based deep eutectic solvents under mild conditions

SO2 capture has been a research hotspot targeting mitigation of SO2 emission, and the subsequent conversion of SO2 is an ingenious protocol, which can avoid regeneration of absorbents and realize utilization of SO2 simultaneously. To this end, a series of protic ionic liquids (PILs)-based deep eutectic solvents (DESs) composed of N-alkylimidazole hydrochloride-based PILs and azoles were designed for the capture and conversion of sulfur dioxide. Among them, [MImH]Cl/2-MIm (1:1) exhibited SO2 loading capacity as high as 1.45 g/g at 1.0 bar and 20 °C, and remarkable SO2 solubility up to 0.56 g/g were achieved at low concentrations (0.6 vol%, 20 °C). In particular, the absorbed SO2 can be directly converted to cyclic sulfites through cycloaddition reaction catalyzed by these DESs under very mild condition (30 °C and 1.0 bar of SO2) without any solvent of additive. By using gas chromatograph-mass spectrometer (GC-MS), yields of cyclic sulfites were determined to be excellent for styrene oxide (98 %) and 1,2-epoxybutane (97 %), and moderate for the sterically hindered epoxides (56 %–76 %). Recycling experiments proved that these DESs maintained good absorption and catalytic performance after five cycles. Furthermore, the absorption and catalytic mechanism were studied by Fourier transform infrared (FT-IR), nuclear magnetic resonance (NMR) spectroscopies, and theoretical calculations, revealing the multi-site absorption mechanism and synergic catalysis in PIL-based DES.

Tunable and facile preparation of chelate-based ionic liquids for highly efficient SO2 separation under low concentration in flue gas

A strategy for facile preparation of chelate-based ionic liquids (ILs) by simple chelation was developed, where a series of chelate-based ILs with tunable functionalized anions (azole), cheap ligands (PEG400), and simple metal ions (Li+, Na+, and K+) were designed for SO2 capture under 2000 ppm in flue gas. Both the anion-tunable strategy and the fine-tuned strategy were used to explore the effect of anions, ligands, and metal ions. The experimental absorptions, spectroscopic investigations, and DFT calculations indicated that the process of SO2 capture was mostly based on the nucleophilic effect of electronegative N site toward SO2. Furthermore, the tuning of alkali metal ions was proved to have little influence on SO2 absorption. The ideal IL, [Na(PEG400)][Tetz], exhibited splendid available absorption capacity of SO2 (0.57 mol/mol), excellent selectivity (63 under 2000 ppm SO2/15% CO2), and outstanding reversibility, indicating good potential for industrial application.

Efficient SO2 capture at ultra-low concentration using a hybrid absorbent of deep eutectic solvent and ethylene glycol

Deep eutectic solvents (DESs) are considered as the highly effective absorbents for sulfur dioxide (SO2) capture. However, the high viscosity of DESs and the resulting slow absorption rate as well as low absorption capacity at low SO2 concentration seriously hinder their industrial application. In this study, DES of N-methyldiethanolamine (MDEA) and imidazole (Im) is simply blended with ethylene glycol (EG) forming a hybrid absorbent, namely MDEA/Im-EG, which exhibits extremely high SO2 capture capacity at low concentration. In particular, SO2 capture capacity in MDEA/Im-EG (molar ratio = 1:1) reaches 0.446 g SO2/g absorbent at 293.2 K with SO2 concentration of 2000 ppm. Moreover, the corresponding desorption enthalpy is only −40.67 kJ/mol. To well understand the results, thermodynamic analysis of SO2 capture is performed and the SO2 capture mechanism is speculated by nuclear magnetic resonance and Fourier transform infrared spectroscopy.

Process compatible desulfurization of NSP cement production: A novel strategy for efficient capture of trace SO2 and the industrial trial

Cement industry contributes to more and more SO2 emission due to utilization of alternative raw materials and fuels, whereas the available calcium-based dry flue gas desulfurization (FGD) technologies present low efficiency due to slow reversible de-SO2 reactions and short gas-solid contact time in the preheater. In the present study, the SO2 capture potentials of CaCO3, CaO, and Ca(OH)2 in the preheater environment were maximized by introducing V2O5-based catalyst and selecting optimal reaction temperature, and the de-SO2 mechanism was extensively discussed. The results showed that the de-SO2 efficiency of calcium-based adsorbents increased by 10–57 times as SO2 was effectively oxidized to SO3 in the presence of V2O5-based catalyst, then maximum de-SO2 efficiency of 75.5% was achieved using Ca(OH)2 and V2O5-CeO2 at 600 °C. Furthermore, CaCO3 assisted by V2O5-CeO2 also had a de-SO2 efficiency of 65.6%. Subsequently, a novel process compatible FGD technology was designed to maximize the de-SO2 ability of raw meal in the preheater by adding V2O5-based catalyst and humidification, the SO2 concentration of flue gas reduced from 1000 mg/Nm3 to less than 100 mg/Nm3 in the industrial-scale trial, as more sulfur was solidified into clinker in the form of alkali sulfate without reducing its properties. This novel process compatible de-SO2 strategy is of real significance for reducing SO2 emission of cement industry at low economic cost.

Effect of the sulfur compounds structure on the SO2 conversion and capture in a bubbling fluidized-bed combustor

SO2 is the main pollutant produced by fluidized bed boiler. Most studies only consider the effect of operating parameters on SO2, while the influence of sulfur structure in coal is ignored. Combustion experiments using pure char loaded with various sulfur structures in a bench-scale bubbling fluidized bed combustor was carried out in this paper to determine the influence of different sulfur structures on SO2 conversion. Effects of excess air, bed temperature and desulfurization efficiency were also investigated. The experimental results show that the order of SO2 conversion is ferrous sulfate > 1-Dodecanethiol > pyrite > diphenyl sulfide > diphenyl sulfoxide > dibenzothiophene. Most sulfur models showed an increase in SO2 conversion with increasing temperature. When the excess air increases, the oxygen content in the furnace is increased, which is beneficial to the conversion of sulfur model to SO2. The desulfurization efficiency of ferrous sulfate and pyrite is higher than that of organic sulfur.

Robust Six-Connected Self-Penetrating Net with Two-Fold Interpenetration for Trace SO2 Removal and UO22+ Detection.

We reported in this work a new metal-organic framework, ECUT-177, showing a highly rare six-connected net with both self-penetrating and interpenetrating features. More interestingly, ECUT-177 also enables promising applications in both trace SO2 capture and luminescence sensing of uranyl.

Magnesite as a Sorbent in Fluid Combustion Conditions—Role of Magnesium in SO2 Sorption Process

This article presents the results of research on magnesites from the Polish deposits of Szklary, Wiry and Braszowice as SO2 sorbents under the conditions of fluidized bed combustion technology. In practice, magnesites are not used as SO2 sorbents, and the role of magnesium in the desulfurization process under the conditions of fluidized bed combustion technology is evaluated differently among researchers. The literature data question the participation of magnesium in the process of SO2 capture from flue gas and prove its high reactivity. Similarly, previous studies referred to the problem of the stability of magnesium-containing desulfurization products under high temperature conditions. This paper analyzes the SO2 binding process and determines the parameters of the sorbent responsible for the efficiency of magnesite sorption. It was shown that MgO, formed as a result of thermal dissociation of magnesite, actively participates in the SO2 binding reaction to form magnesium sulfate phases (MgSO4 and CaMg2(SO4)3) stable in the temperature conditions of fluidized bed boilers. The problem of differentiated reactivity of magnesium-containing sorbents should be associated with the porosity of the sorbents. If the secondary surface of the sorbent is developed based on micropores and smaller mesopores (below 0.1 µm), the sorbent will be characterized by low sorption activity. It was shown that the SO2 binding process is then limited only to the outer part of the sorbent grains. This results in the formation of a massive, SO2-impermeable desulfurization-product layer on the sorbent grain surface. In real conditions, where the reactions of CaCO3 thermal dissociation and SO2 sorption occur almost simultaneously, the inside of the sorbent grains may remain undissociated. The results of experimental research allowed us to trace the dynamics of the SO2 binding process in relation to real conditions prevailing in fluidized bed boilers.

Desulfurization in co-firing of sewage sludge and wooden biomass in a bubbling fluidized bed combustor under air and oxy-fuel conditions

This work presents results of an experimental investigation of a direct addition of Ca-based sorbent for SO2 capture in a bubbling fluidized bed combustion. The fuel of interest was secondary biomass represented by a dried sewage sludge, which was mixed with primary biomass represented by wooden pellets in a weight ratio of 30:70. The performance of this SO2 capture approach is compared in air and oxy-fuel combustion conditions, since the different gas environment in the bed significantly affects the SO2 capture process. The experiments were carried out in an experimental bubbling fluidized bed combustor with a power load of about 30 kW.Sewage sludge is typical for its high ash content and has sufficient dimensions and attrition resistance to create the fluidized bed without the support of external bed materials. However, it typically consists of S-containing organic substances, resulting in the presence of SOX in the off-gas. A reference case was initially conducted without any sorbent addition in order to investigate the effect of sulfur self-retention in the fuel ash. The sulfur retention in the ash reached almost 45 % in air- and up to 55 % under oxy-combustion.In the next phase, the performance of Ca-based sorbents in sulfur capture was evaluated. The sorbents were represented by two types of limestone with diverse CaCO3 content produced at different locations. The experiments were carried out with three Ca/S mole ratios (1.5, 3, and 4.5). The effect of the fluidized bed temperature was also investigated as the most important parameter.The SO2 capture ratio (used as a performance indicator) was calculated based on emission factors, due to the different specific volumes of flue gas in the air and oxy-fuel modes. The results show in general a significantly higher SO2 capture ratio under oxy-fuel conditions. The differences are more significant in lower Ca/S ratios, where the SO2 capture ratio increased from 46 % under air conditions to 75 % under oxy-fuel for Ca/S = 1.5. In the case of the highest Ca/S ratio examined (Ca/S = 4.5), the increase in SO2 capture was from 90 % to 95 %.

A novel reutilization of ash from biomass gasification process: Feasibility and products improvement analysis

Due to the significant growth of the biomass gasification industry, management and disposal of ash has become one of the major environmental issues. This work proposed an innovative strategy that reutilizes ash into gasification process based on its potential catalysis to improve gas products. Reutilization of ash from corn straw (CS) air gasification in a downdraft fixed-bed gasifier was conducted for a feasibility analysis. The effect of ash loading rates (2 wt%, 5 wt%, 10 wt%, 15 wt%, and 20 wt%) on gasification performance were evaluated for an optimal condition analysis. Ash reutilization was proved to be feasible and able to achieve dual objective of improving gas product quality and reducing SO2 release. Results revealed that loading ash exhibited catalysis promoting CO formation, which correlated with the metal active sites provided by the ash and led to an improvement in dry or/and steam reforming. H2 production was also improved. These positive effects increased as ash loading rates increased, and maximum CO and H2 content (19.97 vol% and 15.72 vol%) were achieved at the ash loading rate of 10 wt%. Accordingly, the maximum LHV of gas products (6.47 MJ/Nm3) and the minimum tar content (3.62 g/Nm3) were obtained. While excess ash (loading rate > 10 wt%) showed unsatisfactory performance, even being far behind CS gasification without ash addition. Due to containing CaO, gasification ash showed SO2 capture capacity by forming CaSO4. This reaction competed with the concurrent CaO carbonation, whereas the latter was the priority. The properties of by-products (regenerated ash) were evaluated for overall economic benefits, and the results indicated that it had a high fertilizer potential. These results seemed to be interesting and valuable for ash utilization and effective gasification.

Functionalized Mo[formula omitted]BX[formula omitted] (X = H, OH, O) MBenes as a promising sensor, capturer and storage material for environmentally toxic gases: A case study of 1T and 2H phase

MBenes analogous to MXenes, exfoliated from the bulk MAB phase (M = transition metal, A = IIIA and IVA group, and B = boron) have appeared as promising two dimensional (2D) materials due to their intriguing properties. Here, we report the 2D 1T-2H-phase of Mo2B with their functionalized derivatives Mo2BX2 (X= H, OH, O) and investigate their structural, electronic, and adsorption behavior of toxic gases using the first-principles calculations. This study finds that pristine and functionalized MBenes have dynamic and thermal stability and possess metallic nature in both phases. Based on adsorption behavior and comparison with other 2D materials, we find that pristine MBenes are a desirable adsorbent for NO2, SO2, and CO2 capture. In contrast, the moderate adsorption energies for functionalized MBenes-NH3 systems reveal good sensitivity for NH3 gas detection in both phases. In particular, 2H-Mo2BH2 has higher CT (−0.11e) and appropriate adsorption energy (−0.30 eV), leads a shorter recovery time. Further, DOS calculations reveal that the electrical conducting behavior of MBenes makes them suitable for NH3 detection with a short recovery time. Our results would provide the first insight into the surface-functionalized effect on the structural and electronic properties of the MBenes, and shed light on the application of MBenes for the sensing and catalyst of typical toxic and greenhouse gases, respectively.

On a New Mode of Catalytic Oxidation of Sulfite in the Presence of Mn(II) in Excess of Metal Ions

The paper considers data on the kinetics of catalysis by manganese(II) ions of sulfite oxidation in excess of metal ions. Along with experiments in solutions, information on the dynamics of the reaction in aerosol particles was also involved. For the first time, a fast degenerate-branched (D-B) reaction mode was revealed. Its dynamics is determined by the rate of branching of the chain with the participation of the intermediate \({\text{HSO}}_{5}^{ - }\) and Mn(II) ions. Estimates of the rate constant of this reaction are given in the paper, and the criterion for the transition of the reaction to the D-B mode is considered. It is shown that the observed acceleration of the formation of sulfates in the D-B regime in experiments with aerosol is the result of the coupling of the catalytic reaction and the capture of SO2 from the gas. Calculations within this framework of reaction dynamics find agreement with the data of experiments in smog chambers, as well as with the results of atmospheric aerosol monitoring

Detection of SO2 using a chemically stable Ni(II)-MOF.

The MOF-type Ni2(dobpdc) shows a high chemical stability towards SO2, high capacity for SO2 capture at low pressure (4.3 mmol g-1 at 298 K and up to 0.05 bar), and exceptional cycling performance. Fluorescence experiments demonstrated the SO2 detection properties of Ni2(dobpdc) with a remarkable SO2 detection selectivity. Finally, time-resolved photoluminescence experiments provided a plausible mechanism of SO2 detection by this Ni(II)-based MOF material.

SO2 capture enhancement due to confined methanol within MIL-53(Al)-TDC.

The SO2 capture performance of MIL-53(Al)-TDC was optimised by confining a small amount of MeOH within its pores (MeOH@MIL-53(Al)-TDC). In comparison with fully activated MIL-53(Al)-TDC, MeOH@MIL-53(Al)-TDC shows a 39% higher SO2 capture capacity. Monte Carlo simulations revealed that such an enhancement is associated with an increase in the degree of confinement via the SO2 molecules resulting from the formation of a lump (MeOH molecules) in the vicinity of the μ-OH groups.

Efficient SO2 capture using an amine-functionalized, nanocrystalline cellulose-based adsorbent

Adsorbents made from cellulose derivatives have been widely studied for removal of contaminants such as toxic gases, pharmaceutical ingredients, dyes, and metals due to the availability, cost-effectiveness, and non-contaminating nature of these adsorbents. In this study, amine-functionalized cellulose is proposed as a green adsorbent for SO2 capture. Cellulose nanocrystals were chemically modified with ethylenediamine (EDA) using a solvent-free method. The surface modification was confirmed using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), solid-state carbon nuclear magnetic resonance (13C NMR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and elemental analysis. The effects of functionalization time, temperature, and amount of EDA on the SO2 capture capacity were assessed. During these investigations, the highest adsorption capacity obtained was 2.07 mg-SO2/gsorbent, which is six times higher than for pristine nanocrystalline cellulose (NCC) used under the same conditions. Furthermore, the effect of various operating adsorption temperatures and flow rates was investigated. When the temperature was reduced, there was a significant increase in capture capacity and breakthrough time, confirming an adsorption mechanism for SO2 capture. It was also confirmed that as the flow rate of the feed gas increases, the breakthrough time decreases, as expected, with a steeper breakthrough curve, because of the faster transport of the adsorbate molecules.

MOF-303 as an Effective Adsorbent to Clean CH4: SO2 Capture and Detection

Catalysts for the oxidation of CH4 commonly suffer from poisoning by sulfur-containing molecules, such as H2S and SO2. This is a huge problem in real energy applications. As a possible solution, a material capable of selectively capturing the poisoning SO2 is necessary. In this work, water-stable MOF-303 shows high performance for SO2 capture at low pressures (6.21 mmol·g–1 at 298 K and 0.1 bar), ideal characteristics for the adsorption of trace amounts of SO2. Furthermore, MOF-303 showed high chemical stability toward dry and humid SO2 and a remarkable cycling performance with facile regeneration. In addition, MOF-303 displayed high selectivity toward SO2 over CH4 and CO2. Finally, fluorescence experiments proved that the SO2 detection properties of this MOF material are highly promising, even in the presence of CH4 and CO2.

Preparation and SO2 capture kinetics of a DeSOx coating for the desulfurization of exhaust emission

Sulfur dioxide (SO2) is an extremely harmful pollutant in diesel engine exhaust fumes, which must be controlled and removed effectively. In order to better integrate desulfurization materials into diesel exhaust systems, a new desulfurization powder coating (DeSOx coating) was prepared. The SO2 capture performance and kinetics of the DeSOx coating were subsequently studied. This study used a fixed-bed reactor to test the DeSOx coating SO2 capture performance and conduct kinetic analysis at various temperatures and gas flows. The analysis obtained the kinetic parameters of the activation energy and Arrhenius constant, with the derived rate control equations, under isothermal conditions. The DeSOx coating and filter which were prepared using metal oxide powders, SiO2 colloidal sol, and additives, exhibited an enhanced SO2 capture performance. In this experiment, an MnO2/SiO2/LiOH coating had the best SO2 removal rate and capture capacity at 400 °C. Under a reaction space velocity of 10700 h−1, the MnO2/SiO2/LiOH coating SO2 removal rate was 100% within the first hour of reaction. Under a reaction space velocity of 32000 h−1, the MnO2/SiO2/LiOH coating SO2 capture capacity was 132.7 mgSO2/gmaterial during the second hour of reaction. The SO2 capture conversion rate of the DeSOx coating and filter follows the second-order kinetic mechanism model. For the MnO2/SiO2/LiOH coating, the Arrhenius equation gives an activation energy of 4952 J/mol and the Arrhenius natural logarithmic constant is 8.969 s−1. For the MnO2/SiO2/LiOH filter, the activation energy of the rate constant is 214 J/mol, and the Arrhenius natural logarithmic constant is 3.744 s−1. Therefore, the desulfurization coating is an effective way to remove SO2 pollutants from diesel exhaust gases.

Designing and integrating NOx, SO2 and CO2 capture and utilization process using desalination wastewater

• A novel capture and utilization process for NO x , SO x , and CO 2 is proposed. • The process utilizes metal ion in desalination wastewater. • Using the Ca(OH) 2 for desulfurization, the additional CO 2 emission is prevented. • NO x can be utilized as Ca(NO 3 ) 2 using Ca(OH) 2 as a reactant. • Using the desalination wastewater, all of the absorbent complete can be substituted. Numerous industries are facing serious environmental contamination, because of the significant emission of nitrogen oxide (NO x ), sulfur dioxides (SO 2 ), and carbon dioxide (CO 2 ) and it has become imperative to reduce these gaseous emissions. To reduce pollution caused by gaseous emissions, desalination wastewater is possible to be used because it contains highly concentrated useful mineral ions such as Ca 2+ , Mg 2+ , and Na + which react with carbonate, nitrogen, and sulfate ions. This work designed and integrated NO x , SO 2 , and CO 2 capture and utilization processes using desalination wastewater for cleaner production. To design and integrate the NO x , SO 2 , and CO 2 capture and utilization process, a process model is developed based on validated experimental data. The proposed process model comprises the following three steps: (1) electrolysis and metal ion separation of desalination wastewater to produce NaOH, Mg(OH) 2 , and Ca(OH) 2 ; (2) NO x and SO 2 capture and utilization via Ca(OH) 2 ; (3) CO 2 capture and utilization using NaOH, Mg(OH) 2 and Ca(OH) 2 . Then the economic feasibility of the suggested process is demonstrated compared to conventional process by economic assessment. As a result, the NO x and SO 2 are captured and utilized at about 90% and 99% respectively. In addition, the CO 2 is captured at about 91% and the conversion yields of each carbonate are 99% and 63% respectively. To demonstrate the economic feasibility of the proposed process, two cases are set. Case 1 is the case that employs selective catalytic reduction (SCR), wet flue gas desulfurization (WFGD), and a CO 2 capture process that uses amine as a CO 2 absorbent with an electrodialysis reclaiming unit. Case 2 is the case that employs SCR, WFGD, and the CO 2 capture process that uses amines with an ion-exchange resin reclaiming unit. As a result, the total annualized cost of the proposed process was ∼7.9% and 14% lower than those of Case 1 and Case 2, respectively.

Nanofibrous carbon microspheres with hierarchical porosity for deep eutectic solvent loading and highly efficient SO2 adsorption

Deep eutectic solvents (DESs) are promising absorbents for SO2 capture. However, the high viscosity of DESs limits their applications in the SO2 separation industry. In this study, nanofibrous and porous carbon microspheres (NCMs) with a large surface area (344.5 m2·g−1) were prepared from chitin and used to load [emim]Cl + imidazole DESs for the first time using a physical dispersion process. The DESs were uniformly adsorbed onto the nanofibrous carbon surfaces, and a novel adsorbent (NCMs-xDESs) was formed with a three-dimensional hierarchical porous structure. NCMs showed high loading capacity for DESs (the ideal load ratio was 5:1) and exhibited an appropriate solid-state with significantly decreased DESs viscosity. NCMs-xDESs were used to capture SO2, and the results showed that NCMs-5DESs had the highest adsorption capability for SO2 compared with other NCMs-xDESs. The adsorption capacity of NCMs-5DESs for pure SO2 reached up to 14.66 mol/kg under 25 ℃ and 1 bar conditions. The adsorption capacity remained at 2.89 mol/kg even at low-content SO2 (1,700 ppm) in the mixed gas, which was higher than most solid adsorbents reported in the literature. The excellent adsorption capability was due to the porous structure of the NCMs and the multiple interactions between DESs and SO2. The DESs contained the strong electron-donating ability of Cl−1 and weakly basic tertiary N that can interact with SO2 via electron deficiency and Lewis acids. H-bonding interactions also formed between the DESs and SO2. Additionally, the NCMs-DESs absorbent exhibited excellent reversibility and selectivity for SO2 adsorption after ten cycles. Therefore, the NCMs-DESs absorbent may be a promising candidate for SO2 capture in polluted gas.

Biomass gasification ash reutilization: Recirculation reusability and mechanism analysis

A biomass gasification ash disposal method, recirculating it to gasification process, was proposed in this work. The recirculation reusability was analyzed via reusing corn straw (CS) gasification ash for six recirculation in a gasifier. Metals, especially K, got enriched in ash during ash recirculation. Under the 1st ash recirculation, CO content, H2 content and lower heating value of gas products increased from 16.02 to 19.97 vol%, from 11.30 to 15.72 vol%, from 5.38 to 6.47 MJ/Nm3, respectively. Moreover, it also exhibited an ability in tar decomposition, resulting in a tar reduction (4.63 g/Nm3 for raw CS gasification and 3.62 g/Nm3 for 1st ash recirculation). These positive effects gradually increased during the first four ash recirculation. The positive effects highly depended on the accumulation of metals (K, Na, Ca, Mg, and Fe) in ash. The positive effect did not increase as the fifth and sixth ash recirculation were conducted, resulting from the constant metals content in ash. Grey relational analysis showed that the total content of these metals was the most significant influencing parameter, followed by K content, water-soluble K content, Ca content, respectively. Moreover, pollutant SO2 could be captured by CaO during ash recirculation. This reaction competed with simultaneous CaO carbonation reaction, while it was inferior to the latter. Thus, only the first and second ash recirculation exhibited satisfactory ability in SO2 capture. In summary, ash recirculation in gasification process was feasible for upgrading gasification performance and its effect was persistent.

Efficient and selective absorption of SO2 by low-viscosity matrine-based deep eutectic solvents

Designing excellent liquid absorbents with low viscosity for efficient and selective absorption of sulfur dioxide (SO2) from flue gas is important but still challenging. Herein, matrine-based binary deep eutectic solvents (DESs) were prepared by mixing matrine (Mat) with three different amides including N-methylformamide (MFA), N-ethylformamide (EFA), and N-methylacetamide (MAA). It is found that the viscosities of these three DESs were lower than 20 cP at room temperature, which is significantly lower than other previous DESs or ILs that have been reported. Moreover, the results of SO2 capture showed that the absorption rate of SO2 by the Mat-MFA (1:2) DES was very fast (<3 min) to achieve a relatively large absorption capacity (0.84 g/g at 293.2 K and 1 bar). Mat-MFA (1:2) DES also displayed very high selectivity (576) for the SO2/CO2 (10/90, v/v) mixture, which is higher than most of the liquid absorbents and solid adsorbents currently reported. Furthermore, breakthrough experiments verified the good separation performance of Mat-MFA (1:2) DES in capturing 2% SO2 in the mixture of SO2/N2 or SO2/CO2, respectively. The results illustrated that the features of low viscosity, fast absorption rate, and high selectivity of SO2 capture make the matrine-based DESs have great potential for flue gas desulfurization.