SO2 Sorbent Research Articles

Modulator-Dependent Dynamics Synergistically Enabled Record SO2 Uptake in Zr(IV) Metal-Organic Frameworks Based on Pyrene-Cored Molecular Quadripod Ligand.

Developing innovative porous solid sorbents for the capture and storage of toxic SO2 is crucial for energy-efficient transportation and subsequent processing. Nonetheless, the quest for high-performance SO2 sorbents, characterized by exceptional uptake capacity, minimal regeneration energy requirements, and outstanding recyclability under ambient conditions, remains a significant challenge. In this study, we present the design of a unique tertiary amine-embedded, pyrene-based quadripod-shaped ligand. This ligand is then assembled into a highly porous Zr-metal-organic framework (MOF) denoted as Zr-TPA, which exhibits a newly discovered 3,4,8-c woy net structure. Remarkably, our Zr-TPA MOF achieved an unprecedented SO2 sorption capacity of 22.7 mmol g-1 at 298 K and 1 bar, surpassing those of all previously reported solid sorbents. We elucidated the distinct SO2 sorption behaviors observed in isostructural Zr-TPA variants synthesized with different capping modulators (formate, acetate, benzoate, and trifluoroacetate, abbreviated as FA, HAc, BA, and TFA, respectively) through computational analyses. These analyses revealed unexpected SO2-induced modulator-node dynamics, resulting in transient chemisorption that enhanced synergistic SO2 sorption. Additionally, we conducted a proof-of-concept experiment demonstrating that the captured SO2 in Zr-TPA-FA can be converted in situ into a valuable pharmaceutical intermediate known as aryl N-aminosulfonamide, with a high yield and excellent recyclability. This highlights the potential of robust Zr-MOFs for storing SO2 in catalytic applications. In summary, this work contributes significantly to the development of efficient SO2 solid sorbents and advances our understanding of the molecular mechanisms underlying SO2 sorption in Zr-MOF materials.

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.

An experimental study on the feasibility of in-situ desulfurization performance in a CFB combustor co-burning red mud and coal

As the hazardous solid waste from alumina production, red mud (RM) is often used in the preparation of slurry or catalyst, but rarely considered for in-situ desulfurization of fluidized bed. In this paper, an experimental study was conducted on a lab-scale circulating fluidized bed (CFB) combustor to explore the feasibility of RM replacing limestone for in-situ desulfurization, from the perspectives of efficiency, combustion stability, CaO activity, deposition, NOx emission and operation cost. Although the adopted limestone showed better performance under most working conditions, the highest RM desulfurization efficiency still reached over 94% at 900 °C bed temperature and 20% blending ratio. Better combustion stability could be achieved at 900 °C and no more than 6.11% RM blending. The increase of RM addition had opposite effect on carbon content in bottom ash and fly ash, as well as the SO2 and NOx emissions whatever the bed temperature was. Compared with Zhundong coal, no severe ash deposition was observed at cyclone outlet, but the ash sintering got much worse at the upper furnace. The results demonstrated the feasibility to adopt RM directly as SO2 sorbents during CFB combustion, and achieved the dual effects of SO2 reduction and resource recovery of RM.

The Miocene Lacustrine Chalk from Lignite Bełchatów Deposit (Poland)—Structural and Textural Character and SO2 Sorption Properties in the Fluid Combustion Conditions

The Miocene lacustrine chalk in the Bełchatów lignite deposit is one of the most important accompanying minerals. It is found in three lithological varieties: white, dark and silicified. It is selectively operated and stored on anthropogenic deposits, representing the mineral resource base. The article presents the results of research on lacustrine chalk from the Szczerców mine excavation and accumulated on the anthropogenic deposit (the Szczerców field external landfill) regarding the possibility of using SO2 sorbent in the fluid combustion technology. It has been shown that primarily the structural and textural parameters of the rock, and to a lesser extent, the CaCO3 content, are responsible for the high efficiency of SO2 sorption. It has been proven that in this type of technology, the presence of carbonised plant matter only seemingly lowers the quality parameters of the raw material. It has a significant impact on the sorption properties, effectively influencing the expansion of porosity and specific surface during thermal decomposition. The expansion of the surface is mainly based on the pores on the border of mesopores and macropores, i.e., pores considered to be sorptive towards SO2. These pores, because they are formed in a lower temperature range than the calcite thermal dissociation process and are connected together to form a system, act as diffusion channels of CO2 from inside and SO2 into the inside of the sorbent grains, intensifying the decarbonisation and SO2 sorption processes.

Dolomites as SO2 Sorbents in Fluid Combustion Technology

Dolomites are not used as SO2 sorbents in fluid combustion technology. The literature data show fundamental discrepancies in the possibility of such use. They mainly concern the role of magnesium in the sorption process of SO2 and the durability of desulfurization products under high-temperature conditions. The article demonstrates that MgO is actively involved in the SO2 binding under fluidized furnace conditions. The resulting products of sulfation contain magnesium in their compositions, and their thermal transformations begin only after the temperature exceeds 1100 °C. It has been shown that dolomites are a potential raw material for the production of SO2 sorbents for fluid combustion technology, and their use is justified due to the higher desulfurization efficiency. Parameters of dolomite descriptions were given, by which it will be possible to predict the effects of flue gas desulfurization before the dolomites’ use in industrial conditions. It has been shown that there are opportunities to expand the domestic raw-material base for the production of SO2 sorbents, based on both dolomite resources present in deposits and dolomite waste accumulated in dumps, as well as generated during the current exploitation and processing of dolomites.

Adsorption of SO2 and H2S by sonicated raw eggshell

In this study, raw eggshell was sonicated in presence of N,N-dimethyl-formamide (DMF) and tested for its capacity to adsorb SO2 and H2S. The flow rate was kept constant at 300 ml/min throughout the study. Sonication was carried out at different temperature (30 °C, 60 °C and 80 °C) with a constant contact time of 3 h. It was found that sonication at higher temperature (80 °C) had the best adsorption capacities for both SO2 (2.4 mg/g) and H2S (1.85 mg/g) respectively. The BET surface area of sonicated raw eggshell particles was about 3.39 m2/g. The reading was higher compared to raw eggshell. Moreover, in the process study, the sorbents were tested with 40% of relative humidity and at 2 different reaction temperature i.e. 100 °C and 200 °C. Increasing the reaction temperature and the relative humidity in the inlet gas further increased the adsorption capacities for both SO2 and H2S. The results show that sonicated eggshell particles can be valorised as sorbents for SO2 and H2S.

Interaction of SO2 with ZnO Nanoshapes: Impact of Surface Polarity

As petroleum-related products dominate the global fuel market, acid gas resistant materials are in demand. ZnO is one of the widely used materials as SO2 sorbent and catalyst/catalyst support. To u...

Dehydrated Na6[AlSiO4]6 sodalite as a promising SO2 sorbent material: A first principles thermodynamics prediction

AbstractThe capture of sulfur dioxide (SO2) using dehydrated Na6[AlSiO4]6 sodalite was investigated using the first principles density functional theory calculations and thermodynamics analysis. The adsorption geometries, energetics, and electronic structures were predicted with the increasing number of SO2 adsorbates. Upon adsorption, the S atom of single SO2 molecule tends to align to the framework O2− and the two oxygen atoms are oriented to the framework Na+, through electrostatic interactions and with a minor charge transfer. Increasing the number of SO2 adsorbates, the Na6[AlSiO4]6 sodalite framework shrinks first and then expands. Statistical thermodynamics analysis suggests that the capture reaches its saturation limit of four SO2 molecules per Na6[AlSiO4]6 formula (~300 mg/g) at room temperature and a low SO2 partial pressure of 0.001 atm, indicating that dehydrated Na6[AlSiO4]6 can be an efficient SO2 sorbent even at its extremely low concentrations. Higher SO2 partial pressures lead to a higher capture capacity. A low baking temperature of 100‐150°C can efficiently release the adsorbed SO2 and hence restore the capture capacity of Na6[AlSiO4]6.

THE ASSESSMENT OF USEFULNESS OF LIMESTONES FROM THE KLESZCZÓW GRABEN (BEŁCHATÓW LIGNITE DEPOSIT – SZCZERCÓW FIELD) AS POTENTIAL SO2 SORBENTS IN THE POWER INDUSTRY – PROBLEMS OF GEOLOGICAL DOCUMENTING

Jurassic limestones of the Kleszczów Graben are among the most important accompanying raw materials in the Bełchatów lignite deposit. In recent years, there has been a need to recognize their suitability as SO2 sorbents for use in the energy industry. The limestones are characterized by high lithological variability. They show both high hardness and compactness, and are weakly concise or even silty. At the top parts, they are subjected to karst processes. The lower parts are affected by secondary mineralization processes, among which the silicification process is most advanced. The effects of other transformation processes, such as compaction, cementation, dissolution and recrystallization of calcite are also visible. These processes contributed to a significant diversification of the mineral and chemical composition of limestone, and differentiation of physico-chemical and physical-mechanical parameters responsible for assessing the suitability for their commercial use as a raw material for the production of SO2 sorbents. Other problems associated with documenting the limestones in the Bełchatów deposit are related to their lesser importance compared to the main mineral. Its degree of exploration is low, characterized by a lower density of exploratory boreholes and significantly longer average lengths of samples collected from drill cores. At the present stage of the accompanying mineral exploration, only a preliminary estimation of limestone resources as potential SO2 sorbents is possible. The precise estimation will be possible after constructing a 3D model of criterion parameters and developing an extraction scenario.

Role of CuO in improving NH3 and SO2 capture on nanoporous Fe2O3 sorbents

In this work, mixed Fe/Cu oxides as sorbents for SO2 and NH3 removal were investigated. Nanoporous iron oxide mixed with 10, 20 and 30 at.% CuO were prepared by thermal decomposition of the corresponding oxalates at 250 °C for 5 h in air. The mixed Fe/Cu oxalates were obtained from the co-precipitation of iron/copper sulfate and ammonium oxalate during ultrasonication. The physical properties of the oxalate precursors and the resulting mixed Fe/Cu oxides were characterized with SEM, TGA-DSC, FTIR, powder XRD and Mössbauer spectroscopy. The porosity was studied by N2 adsorption-desorption isotherms and small angle X-ray scattering. Evenly dispersed CuO hindered the crystallization of Fe2O3, which significantly increased the specific BET surface area from 211 m2/g for Fe2O3 to 354 m2/g for Fe0.8Cu0.2Ox. As a result, SO2 and NH3 adsorption on Fe0.8Cu0.2Ox were enhanced by about 70% compared to Fe2O3. Compared to Fe2O3-impregnated activated carbons, nanoporous Fe0.8Cu0.2Ox could capture five times more SO2 per unit weight, which will be attractive for applications in respirators with lower weight and smaller size.

Amine-Functionalized Covalent Organic Framework for Efficient SO2 Capture with High Reversibility

Removing sulfur dioxide (SO2) from exhaust flue gases of fossil fuel power plants is an important issue given the toxicity of SO2 and subsequent environmental problems. To address this issue, we successfully developed a new series of imide-linked covalent organic frameworks (COFs) that have high mesoporosity with large surface areas to support gas flowing through channels; furthermore, we incorporated 4-[(dimethylamino)methyl]aniline (DMMA) as the modulator to the imide-linked COF. We observed that the functionalized COFs serving as SO2 adsorbents exhibit outstanding molar SO2 sorption capacity, i.e., PI-COF-m10 record 6.30 mmol SO2 g−1 (40 wt%). To our knowledge, it is firstly reported COF as SO2 sorbent to date. We also observed that the adsorbed SO2 is completely desorbed in a short time period with remarkable reversibility. These results suggest that channel-wall functional engineering could be a facile and powerful strategy for developing mesoporous COFs for high-performance reproducible gas storage and separation.

Analysis of the influence of fusion synthesis parameters on the SO2sorption properties of zeolites produced out of fly ash

Fly ash zeolites are interesting alternative for zeolies produced out of pure chemicals as well as for natural zeolites. It can be applied as SO2 sorbents out of flue gases. In the work the experiments were aimed at investigation of SO2 sorption capacity of samples produced out of fly ash in fusion process. The influence of fusion reaction parameters on the type of obtained zeolites and on the efficiency of synthesis was investigated. The samples containing the same types of zeolites, but with different production yield were testes on SO2 sorption capacity.

Multiple-Site SO2 -Capture Ionic Liquids with Nearly Uniform Site Performance.

We propose a series of azolium poly(azolyl)borate ionic liquids (ILs) for reversible SO2 capture. Density functional calculations demonstrate that the designed borate anions can strongly bond to SO2 at multiple sites with nearly uniform binding energies. Thus, as well as high overall uptakes, the ILs can achieve much higher effective uptakes (the uptake difference between absorption and desorption conditions) than existing SO2 -capture reagents. The larger size of the borate anions, the evenly distributed negative charge among the azolyl rings, and the blocking of the conjugation by the tetrahedral boron concertedly reduce absorbate-absorbate repulsion, which leads to a large disparity among binding sites in other multiple-site SO2 sorbents.

The Carbonation Behaviors of Limestone Particle in Oxygen-Fuel Circulating Fluidized Bed O<sub>2</sub>/CO<sub>2 </sub>Flue Gas

Limestone powder is still applied as SO2 sorbent in emerging oxygen-fuel circulating fluidized bed boiler, but its carbonation in O2/CO2 flue gas is an unclear problem. For a better understanding of carbonation behaviors, the tube furnace heating system was built for simulating circulating fluidized bed boiler flue gas by regulating the supply of O, CO2, N2, SO2 and H2O, and Carbonation reaction was tested. Thermal gravimetric analysis and scanning electron microscopy were used. It was found that carbonation is closely related to temperature, CO2 concentration, impurities, water vapor, and cycle times; high temperature can promote carbonation process; high concentration of CO2 can inhibit the chemical reaction stage speed of carbonation process, but it has little effect on the final conversion rate; water vapor can increase the final conversion rate of carbonation; the cycle times will reduce the activity of carbonation. The presence of carbonation turns the traditional boiler flue gas indirect desulfurization model into indirect desulfurization mechanism which does not have a negative impact on SO2 removal efficiency.

Reversible SO2 Uptake by Tetraalkylammonium Halides: Energetics and Structural Aspects of Adduct Formation Between SO2 and Halide Ions

AbstractContact with SO2 causes almost immediate dissolution of tetraalkylammonium halides, R4NX, (R = CH3 (Me), X = I; R = C2H5 (Et), X = Cl, Br, I; R = C4H9 (nBu), X = Cl, Br), with the formation of an adduct, [R4N]+[(SO2)nX]– (n = 1–4). Vapor pressure measurements indicate the proclivity for SO2 uptake follows the order N(CH3)4+ < N(C2H5)4+ < N(C4H9)4+. This trend is in accord with the Jenkins–Passmore volume‐based thermodynamic model. Born–Haber cycles, incorporating the lattice energy and gas phase energy terms, are used to evaluate the energetic feasibility of reactions. Density functional theory calculations (B3PW91; 6‐311+G(3df)) have been used to calculate the energetics of (SO2)nX– (X = Cl and Br) anions in the gas phase. The experimental studies show that tetraalkylammonium halides are feasible sorbents for SO2. In order to correlate the theoretical model, experimental enthalpy, ΔrH° and entropy, ΔrS° changes have been determined by the van't Hoff method for the binding of one SO2 molecule to (C2H5)4NCl, resulting in the liquid adduct (C2H5)4NCl·SO2. The structure of the analogous 1:1 bromide adduct, (C2H5)4NBr·SO2, has been determined by single‐crystal X‐ray diffraction (monoclinic, P21/c, a = 9.1409(14) Å, b = 12.3790(19) Å, c = 11.3851(17) Å, β = 107.952(2)°, V = 1225.6(3) Å3). The structure consists of discrete alkylammonium cations, bromide anions and SO2 molecules with short contacts between the anion and SO2 molecules. The (C2H5)4N+ cationadopts a transoid conformation with D2d symmetry, and represents a rare example of a well‐ordered (C2H5)4N+ cation in a crystal structure. The Br– anions and SO2 molecules forms a chain, (SO2Br–)n, with bifurcated contacts. Non‐bonding electron pairs on the halide anions engage in electrostatic interactions with the sulfur atoms and charge‐transfer interactions with the antibonding S–O orbitals of the bound SO2 moiety. Raman and 17O NMR spectra provide compelling evidence for a charge‐transfer interaction between SO2 molecules and the halide ions.

SO2/Hg removal from flue gas by dry FGD

To study the mechanism of SO2 and Hg removal from flue gas, an experimental packed bed reactor was designed to simulate the dry FGD, where a mixture of lime and fly ash in ratio 1:3 w/w was used as the SO2 and Hg sorbent, and steam at temperature of 100°C was applied for activation of the sorbent, while the activation time set to 20min. The experimental factors including the SO2/Hg sorbent characteristics, 50% breakthrough time for SO2/Hg removal, sorbent packed bed depth and reaction temperature were investigated. The experimental results show that after steam activation, the BET specific surface area and specific pore volume increased from 37.8 to 45.5m2/g and from 0.42 to 0.51cm3/g, respectively. With activation of the sorbent by steam, the 50% breakthrough times of SO2 and Hg removal increased from 34 to 42min and from 23 to 45min, respectively. When the packed bed depth was increased from 5 to 25mm, the 50% breakthrough times for Hg and SO2 removal increased from 12 to 52min and from 6 to 47min, respectively. With the increase of the reaction temperature, the 50% breakthrough of SO2/Hg removal decreased accordingly. Steam activation can efficiently improve SO2/Hg removal simultaneously.

Application of XPS method in the research into Ni ion-modified montmorillonite as a SO2 sorbent

A series of montmorillonites with adsorbed nickel ions was prepared through adsorption of nitrates from water solutions; there were four methods adopted. The surface of the sample under modification was investigated with the method of argon adsorption and XPS (X-ray photoelectron spectroscopy). SO2 was investigated on nickel-modified montmorillonites. Nickel cations were adsorbed on the montmorillonite surface as Ni2+ in Ni(OH)2 or NiO. Montmorillonite — after nickel adsorption — adsorbs SO2 physically. An addition of Mont–Ni to hard coal in a ratio 1:500 reduces SO2 emissions in the combustion process by 75–85%. Waste bentonite can be utilized for reducing SO2 emissions after processing.

Sulfation behavior of white mud from paper manufacture as SO2 sorbent at fluidized bed combustion temperatures

The calcination characteristics, sulfation conversion, and sulfation kinetics of a white mud from paper manufacture at fluidized bed combustion temperatures were investigated in a thermogravimetric analyzer. Also, the comparison between the white mud and the limestone in sulfation behavior and microstructure was made. Although the white mud and the limestone both contain lots of CaCO3, they are different in the alkali metal ions content and microstructure. It results in a marked difference in sulfation behavior between the white mud and the limestone. The CaO derived from white mud achieves the maximum sulfation conversion of 83% at about 940 °C which is 1.7 times higher than that derived from limestone at about 880 °C. The shrinking unreacted core model is appropriate to analyze the sulfation kinetics of the white mud. The chemical reaction activation energy E a and the activation energy for product layer diffusion E p for the sulfation of the white mud are 44.94 and 55.61 kJ mol−1, respectively. E p for the limestone is 2.8 times greater than that for the white mud. The calcined white mud possesses higher surface area than the calcined limestone. Moreover, the calcined white mud has more abundant pores in 4–24 nm range which is almost optimum pore size for sulfation. It indicates that the microstructure of the white mud is beneficial for SO2 removal.

Stability study of inverse suspension copolymerization of 1,1,3,3‐tetramethylguandium acrylate and N,N′‐methylenebisacrylamide

AbstractIn a previous study, we synthesized crosslinked P(TMGA‐co‐MBA) via an inverse suspension copolymerization of 1,1,3,3‐tetramethylguandium acrylate (TMGA) and N,N′‐methylenebisacrylamide (MBA) and found that the product is a good SO2 sorbent. However, the polymerization stability appeared to be poor under some reaction conditions and is far from being elucidated. In this study, the inverse suspension copolymerization was carried out using cyclohexane as solvent, Span60 as dispersant, and ammonium persulfate (APS) as initiator. The effects of the reaction conditions such as stirring speed, dispersant concentration, and temperature on the polymerization stability and particle size were systematically examined. It is found that the polymerization stability is a strong function of these parameters. Stable crosslinked poly(TMGA‐co‐MBA) particles from micrometer to millimeter diameters were synthesized under optimized conditions. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Effects of rapid calcination on properties of calcium-based sorbents

The calcination process may influence subsequent fragmentation, sintering and swelling when CaO derived from limestone acts as a CO 2 or SO 2-sorbent in combustion, gasification and reforming. Sorbent properties are affected by CO 2 partial pressure, total pressure, temperature, heating rate, impurities and sample size. In this study, the effect of calcination heating rate was investigated based on an electrically heated platinum foil. The effects of heating rate (up to 800 °C/s), calcination temperature (700–950 °C), particle size (90–180 μm) and sweep gas velocity were investigated. Higher initial heating rates led to lower extents of limestone calcination, but the extents of carbonation of the resulting CaO were similar to each other. Calcium utilization declined markedly during carbonation or sulphation of CaO after calcination by rapid heating. Experimental results show that carbonation and calcium utilization were most effective for carbonation temperatures between 503 and 607 °C. Increasing the extent of calcination is not the best way to improve overall calcium utilization due to the vast increase in energy consumption.