SO2 Gas Research Articles

A novel method of combined desulfurization and heat utilization of low-temperature flue gas from hot blast stove for blast furnace: Laboratory research and industrial application

To address the challenges of low waste heat utilization rates and high desulfurization costs, this study proposes a novel method for combined desulfurization and heat utilization of low-temperature flue gas. By utilizing the low-temperature flue gas from hot blast stoves to dry lump metallurgical coke, the method also achieves flue gas desulfurization during the lump coke drying process. During the drying process, the wet lump coke desulfurizes due to the reaction between water vapor in the lump coke and the SO2 and oxygen in the flue gas, resulting in the formation of sulfuric acid. Additionally, the coke powder generated by friction during the drying process of lump coke has a large specific surface area, enabling it to adsorb additional quantities of SO2 and enhance the desulfurization process. It's important to note that the lump coke itself does not exhibit adsorption properties towards SO2 during the drying process, and the gas is not retained within the lump coke. Industrial applications indicate the outlet flue gas temperature is reduced from 175 °C to 60 °C, and the concentration of SO2 in the outlet flue gas is reduced from 150 mg/m3 to 29 mg/m3.

Selectivity of an Ag/BTO-Based Nanocomposite as a Gas Sensor Between NO2 and SO2 Gases.

The novel Ag/BTO/TiO2 nanocomposite was assessed for its gas-sensing capabilities toward hazardous gases NO2 and SO2. It exhibited p-type behavior with increasing resistance for SO2 with a response and recovery time of ∼5 and ∼2 s, respectively, switching to n-type behavior when exposed to NO2 with a response and recovery time of ∼20 and ∼250 s, respectively. Analyte gas concentrations from 0 to 220 ppm were taken for analysis. Selectivity analysis at room temperature revealed NO2's superior response of ∼20% above 180 ppm, compared to SO2's < 3% response at 180 ppm. NO2(VC) achieved its highest response (∼45%) at 30 ppm and remained constant above 80 ppm, while SO2(VC) peaked at ∼30% at 60 ppm but declined with increasing flow rates. Further, the increasing temperature led to an amplified response for NO2, whereas SO2 showed an increase in response after 180 °C. SO2(VC) exhibited a significant response of ∼70% from 140 °C onward. Additionally, NO2(VC) showed distinct peaks at 160, 250, and 290 °C with responses of 50, 65, and 80%, respectively. The calculated limit of detection values were 236 ppm for NO2, 644.07 ppm for SO2, 401.32 ppm for NO2(VC), and 496.86 ppm for SO2(VC).

Recycling of pyrite and gypsum mining residues through thermochemical conversion into valuable products

Pyrite-containing tailings pose an environmental challenge due to the risk of Acid Mine Drainage (AMD) upon storing if not properly managed. AMD can, however, be neutralized with alkali materials like lime which leads to the generation of gypsum that also ends up in the landfill. Instead of landfilling this residue, it can be recycled into potentially useful products. A proposed process involves decomposing pyrite, reduction of pyrrhotite, and finally conversion of gypsum to lime. This study evaluates the recycling/thermochemical conversion process of pyrite tailings and gypsum residues from the Boliden Aitik mine using thermodynamic modeling, simultaneous thermal analyses coupled with mass spectroscopy, and mineralogical composition identification. It was observed that pyrite can undergo complete decomposition into pyrrhotite and release elemental sulfur below 750 °C in an inert atmosphere. Furthermore, successful reduction of pyrrhotite was achieved through the application of biochar in the presence of lime at 950 °C in an inert atmosphere. The study also reveals that gypsum can be effectively converted to lime at 1200 °C in an inert atmosphere when accompanied by calcium sulfide (CaS). Moreover, the energy and material balance of the process was analyzed, considering the conversion of 1 ton of pyrite tailings. The products include 0.4 tons of iron powder, 2.7 tons of SO2 gas, 0.4 tons of CO2 gas, and 1.21 tons of excess active lime. The calculated energy consumption for this process was determined to be 2893 kWh.

First-principles study of gas molecule adsorption on Ga-doped silicene

In this paper, based on first-principles calculations, the geometric structure and electronic properties of intrinsic silicene and metal element Ga doped silicene were studied, and three harmful gases CO, SO2 and NH3 gas molecules and H2O molecules were analyzed in two adsorption properties on the surface of two material. For each gas molecule, the optimal adsorption site was tried and determined, and parameters such as adsorption distance, adsorption energy, transfer charge, recovery time, and density of states were calculated to understand the adsorption mechanism. It was found that the adsorption capacity of the selected gas molecules on intrinsic silicene was weak except for NH3. While Ga doped silicene is a relatively stable structure, the adsorption energies of CO, SO2 and NH3 gas molecules on its surface increase in different degrees, the adsorption energies are −0.51 eV, −0.82 eV and −0.73 eV, but no adsorption to H2O. The results show that the doping of Ga atoms improves the adsorption performance of silicene materials, and is less affected by the humidity in the air in practical applications, which provides a theoretical reference for the gas-sensing properties of Ga doped silicene materials.

Adsorption of sulfur-containing contaminant gases by pristine, Cr and Mo doped NbS2 monolayers based on density functional theory

The adsorption and sensor performance of hazardous gases containing sulfur (SO2, H2S and SO3) on pristine, Cr and Mo doped NbS2 monolayers (Cr-NbS2 and Mo-NbS2) were investigated in detail based on density functional theory. The comparative analysis of the parameters such as density of states, adsorption energy, charge transfer, recovery time and work function of the systems showed that the pristine NbS2 monolayer have poor sensor performance for sulfur-containing hazardous gases due to weak adsorption capacity, insignificant charge transfer and insignificant changes in electronic properties after gas adsorption on the surface. After doping with Cr atoms, the adsorption performance of Cr-NbS2 was significantly improved, and it can be used as a sensor for SO2 and H2S gases and as an adsorbent for SO3 gas. The adsorption performance of Mo-NbS2 is also significantly improved by doping with Mo atoms, and it can be used as a sensor for H2S gas and as an adsorbent for SO2 and SO3 gas. Therefore, Cr-NbS2 and Mo-NbS2 are revealed to be sensing or elimination materials for the harmful gases containing sulfur (SO2, H2S and SO3) in the atmosphere.

Highly Selective Chemiresistive SO2 Sensor Based on a Reduced Graphene Oxide/Porphyrin (rGO/TAPP) Composite

AbstractThe emergence of toxic pollutants due to heavy human intervention in the ecosystem causes serious environmental problems. Therefore, sensors based on material having a strong affinity towards specific environmental gaseous pollutants are urgently needed. The present study deals with chemiresistive gas sensors for the detection of sulfur dioxide (SO2) based on a composite of reduced graphene oxide (rGO) and 5,10,15,20-tetrakis(4-aminophenyl) porphyrin (TAPP). The improved Hummers method was used to synthesize graphene oxide (GO); it was further thermally reduced to rGO. The pattern of the copper electrode was coated on glass slides with a shadow mask using thermal evaporation. Then, GO was drop-cast between the two copper electrodes, thermally reduced to obtain rGO, and then modified by TAPP. The spectroscopic, structural, morphological, electrical, and optical studies were carried out using Fourier transform infrared spectroscopy, x-ray diffraction, Raman spectroscopy, atomic force microscopy, field emission scanning electron microscopy, current–voltage (I–V) and UV–visible spectroscopy, respectively. The developed sensor shows high selectivity towards SO2 gas analytes among exposed gaseous analytes. It exhibited reproducible response from 50 ppm to 200 ppm with enhanced repeatability at 50 ppm. The rGO/TAPP sensor exhibited a significant response (57 s) and recovery time (61 s), with a 5 ppm limit of detection. Graphical Abstract

First-principles study on α/β/γ-FeB6 monolayers as potential gas sensor for H2S and SO2.

The adsorptions of toxic gases SO2 and H2S on 2D α/β/γ-FeB6 monolayer were investigated using density functional theory calculations. To analyze the interaction between gas molecule H2S/SO2 and α/β/γ-FeB6 monolayer, we calculated adsorption energy, adsorption distance, Mullikan charge, charge density difference, band structure, the density of states, work function, and theoretical recovery time. The adsorption energies show that H2S/SO2 is chemisorbed on α/β-FeB6 while H2S/SO2 is physiosorbed on γ-FeB6 monolayer. As a result, γ-FeB6 has a short recovery time for H2S (5.71×10-8 s)/SO2 (1.94×10-5 s) due to modest adsorption. Therefore, γ-FeB6 may be a promising candidate for reusable H2S/SO2 sensors at room temperature. Although H2S is chemisorbed on α/β-FeB6, as the working temperature rises to 500 K, the recovery time of α/β-FeB6 for H2S can decrease to 1.13×10-1 s and 2.08×10-1 s, respectively, which are well within the detectable range. So, α/β-FeB6 monolayer also may be a good candidate for H2S gas sensor. Calculations were performed at GGA-PBE/DNP level using the Dmol3 module implemented in the Material Studio 2018 software package.

Gas-sensing properties and first-principles comparative study of metal (Pd, Pt)-decorated MoSe2 hierarchical nanoflowers for efficient SO2 detection at room temperature

The online detection and control of concentration for agricultural greenhouse gas SO2 is an important technology to ensure normal agricultural production. This paper reports on a facile hydrothermal method to synthesis Pd-decorated and Pt-decorated MoSe2 nanomaterials, i.e. multistage flower-like structures with attached nanometallic particles and nanosheets hierarchical structures. The Pd/MoSe2 and Pt/MoSe2 hierarchical materials were characterized for the nanostructure, microscopic morphology and elemental compositions. The gas-sensing properties results show that the Pd/MoSe2 and Pt/MoSe2 nanofilm sensors have good sensitivity, stability and response rate to SO2 gas. The response values for the metal Pd and Pt decorated samples to 20 ppm SO2 were 2.04 and 3.42 times higher than those for the intrinsic MoSe2 samples at room temperature. The hierarchical flower-like structure proved to be beneficial in providing more adsorption drop points. In addition, based on the first-principles, the geometrical parameters and electronic properties of the metal-decorated modified structures were calculated to comparatively investigate the enhanced sensing mechanism of SO2 by nanoflower materials. The Pt-MoSe2 nanofilm sensor achieves a high sensitivity detection with a response value of 2.89 for low concentration (1 ppm) of SO2, which is confirming the promotion of charge transfer by metal decorating. This study suggests that Pd-MoSe2 and Pt-MoSe2 hierarchical structures may be recommended for the detection of the agricultural greenhouse gas SO2.

Enhanced adsorption and sensitivity for SF6 decomposition gas detection on penta PdSe2 monolayer: A Density Functional Theory investigation with van der Waals correction

The breakdown of the insulating gas SF6 causes the Gas-Insulated Switchgear (GIS) fault type to occur during high-voltage power operation putting the power system's safety in threat. The adsorption behaviour and sensitivity of five gases (H2S, SO2, SO2F2, SOF2 and HF) dissolved by SF6 on PdSe2 monolayers is explored using Density Functional Theory (DFT) in this work. Perdew-Burke-Ernzerhof (PBE) within a Generalised Gradient Approximation (GGA) was employed for the computational investigation. PdSe2 monolayer and SF6 decomposition gas adsorbed PdSe2 are built and optimized to get the most stable structures. The adsorption energy (Ead), charge transfer (QT), bandgap (Eg), Density of States (DOS), Work Function (WF), Sensitivity (S), and recovery time (τ) were computed to investigate the adsorption mechanism of PdSe2 monolayer to SF6 decomposition gas. The computation revealed that the SO2 and H2S adsorption systems have the highest adsorption energy of − 0.51 eV and − 0.52 eV respectively. The SO2F2 adsorption system has the weakest adsorption energy of − 0.44 eV. The findings show that PdSe2 systems have improved sensing performance for SO2 and H2S gas. The PdSe2 monolayer exhibits better sensitivity and a stable desorption time. The PdSe2 monolayer for SO2 and H2S detection shows high sensitivity, attaining 91.89% and 85.53%, respectively. This research establishes the groundwork for the development of PdSe2 monolayer adsorbents for use in SF6-insulated equipment.

Development of emission reduction measures of trace gas emissions from coal-fired power plants in Indonesia

Most of Indonesia’s electricity demand is supplied by coal fired power plants (CFPPs) which can potentially emit huge amounts of air pollutant gases such as NOx and SO2 gas. The country has committed to reduce Greenhouse Gases (GHGs) emission by 2030 through Nationally Determined Contributions but some emission reduction measures may also reduce air pollutant gases. Flue Gas Desulfurization (FGD) and Atmospheric Fluidized Bed Combustion (AFBC) are the leading control technologies for reducing SO2 and NOx emissions that can be installed in the CFPPs. This study aims to determine the pollution load of SO2 and NOx gases in 2030 generated from CFPPs operation with (reduction scenario) and without FGD and AFCB control technology (business as usual (BAU)). The gas pollution load was calculated using the Atmospheric Brown Clouds- Emissions Inventory Manual (ABC-EIM) procedure. Based on the BAU scenario, the emission load accounted of 1,440,192 tons/year for NOx and 613,121 tons/year for SO2 in 2030. After implementing the control technology scenarios in 2030, the NOx emission load is projected to decrease to 579,610 tons/year, and the SO2 emission load decrease to 77,920 tons/year. The application of AFBC and FGD control technologies can potentially reduce NOx and SO2 emissions load from CFPPs operation in 2030 thus it can help to improve air quality in the future.

Density functional theory study on gas-sensing property of (SnO2)n (n = 1–3) modified MoTe2 towards chlorine, ammonia, and sulphur dioxide upon diesel-driven vehicle

Chlorine (Cl2), ammonia (NH3), and sulphur dioxide (SO2) are three typical toxic gases of tank-vehicle transportation. it is necessary to conduct online detection of these gases to ensure transportation safety and exhaust emission monitoring. In this study, tin dioxide (SnO2)n (n = 1–3) modified molybdenum (IV) telluride (MoTe2) monolayer were selected to explore its adsorption characteristics towards Cl2, NH3, and SO2 gases. All calculations are based on density function theory, geometric structure, charge transfer, adsorption energy, the density of states, and molecular orbitals were taken into account to compare and analyze the adsorption performance of the gas-sensing material before and after surface modification. The results show that these three gases are physically adsorbed on the intrinsic material. The modified (SnO2)n (n = 1–3) are all stably bound to the MoTe2 surface. For both Cl2 and NH3, the adsorption energies are in order of SnO2-MoTe2 > (SnO2)2-MoTe2 > (SnO2)3-MoTe2. And the adsorption energies for SO2 can be ranked as (SnO2)3-MoTe2 > SnO2-MoTe2 > (SnO2)2-MoTe2. The significant changes in electrical conductivity indicate the modified MoTe2 system consistently showed excellent sensitivity to the three gases. Therefore, the (SnO2)n-modified MoTe2 system is expected to be a candidate gas-sensing material for Cl2, NH3, and SO2, opening up a new perspective on MoTe2 in the field of gas detection.

Sensing properties of SF6 decomposition gas sensor based on Rh doped α-AsP monolayer

The detection of decomposition components of SF6 insulating gas in gas-insulated switchgear (GIS) is of great significance to evaluating GIS's operating state and ensuring the equipment's safety. In order to detect and diagnose the main decomposition gases SO2, SOF2, and SO2F2 of SF6, this work systematically analyses the intrinsic α-AsP monolayer and two Rh-modified α-AsP monolayers. Specifically, the adsorption structure, energy, charge transfer and deformed charge density, the total density of states, the partial density of states, and recovery time were discussed and calculated in detail, and the internal mechanism of the entire adsorption process was clarified. Meanwhile, the results show that Rh adsorbed on α-AsP monolayer (Rh-AsP-O) has a good adsorption effect on SO2, SOF2, and SO2F2 gases. From the sensor's perspective, the Rh-AsP-O monolayer has potential applications in the gas-sensing field of SO2, SOF2, and SO2F2.

Adsorption and Sensing of NO2, SO2, and NH3 on a Janus MoSeTe Monolayer Decorated with Transition Metals (Fe, Co, and Ni): A First-Principles Study.

This paper reports the adsorption of toxic gases (NO2, SO2, and NH3) on a MoSeTe structure based on first principles. It was found that the gas (NO2, SO2, and NH3) adsorption on a pure MoSeTe monolayer was weak; however, the adsorption performance of these gas molecules on transition-metal-atom-supported MoSeTe monolayers (TM-MoSeTe) was better than that on pure MoSeTe monolayers. In addition, there was more charge transfer between gas molecules and TM-MoSeTe. By comparing the adsorption energy and charge transfer values, the trend of adsorption energy and charge transfer in the adsorption of NO2 and SO2 was determined to be Fe-MoSeTe > Co-MoSeTe > Ni-MoSeTe. For the adsorption of NH3, the effect trend was as follows: Co-MoSeTe > Ni-MoSeTe > Fe-MoSeTe. Finally, by comparing their response times, the better gas sensor was selected. The Ni-MoSeTe system is suitable for NO2 gas sensors, and the Fe-MoSeTe and Co-MoSeTe systems are suitable for SO2 gas sensors. The Fe-MoSeTe, Co-MoSeTe, and Ni-MoSeTe systems are all suitable for NH3 gas sensors. Janus transition-metal dichalcogenides have the potential to be used as gas-sensing and scavenging materials.

Computational and Experimental Study on the Combined Sulfur and Chromium Poisoning Mechanism of LSM, LSCF and LNO Cathodes

Prevovskite (La,Sr)MnO3 (LSM), (La,Sr)(Co,Fe)O3 (LSCF) and Ruddlesden-Popper (RP) type La2NiO4 (LNO) phase, as solid oxide fuel cell (SOFC) cathodes, has been used due to its high efficiency and low emissions. To further understand the long-term degradation mechanism of the LSM, LSCF, and LNO phase in SO2 and Cr vapor gas impurities, they were prepared, sintered, and heat-treated at 800, 900, and 1000 ℃ in the sulfur, chromium, and water vapor-containing atmospheres, respectively. Later, XRD, SEM and TEM techniques were applied to the samples and corresponding simulations were made by the CALPHAD approach based on the same experimental conditions to verify the formation of the detrimental secondary phases. Results showed good agreement among the predictions and experiments. More importantly, extensive simulations were also conducted under different conditions (temperature, the partial pressure of oxygen and impurities) to understand the long-term degradation mechanism and optimize the operating conditions.

Effect of additives on sulfur resistance of catalytic filter material during denitrification and synergistic decomposition of 1,2-DCBz.

Modified Mn-Ce/P84 catalytic filter material can be used to achieve high removal efficiency of NOx and 1,2-DCBz in bag-filtering dust precipitator synergistic removal of multiple pollutants. However, the presence of SO2 in the actual industrial flue gas has an adverse impact on the catalytic performance of the catalytic filter material. In this paper, a kind of Mn-Ce catalytic filter material was prepared by the impregnation method, which was modified by Fe, Cu, and Co, respectively. As a result, the sulfur resistance of the catalytic filter material was improved. The change of catalytic activity of the three kinds of modified catalytic filter material at different concentrations was compared in the SO2 flue gas fixed bed system. And the modified catalytic filter materials were characterized by SEM, BET, XPS, XRD, and H2-TPR. When the temperature was over 80 °C, different concentrations of SO2 were injected into the simulated flue gas to test the denitrification activity of the catalytic filter material. The results showed that under the low SO2 concentration of 150 ppm, the denitrification activity and 1,2-DCBz activity of Fe, Co, and Cu-modified filter material were increased, and the sulfur resistance of Fe was better under the flue gas conditions of 300 ppm and 450 ppm SO2. Under the condition of 450 ppm SO2 and 200 °C reaction, 93.4% denitrification efficiency and 96.1% 1,2-DCBz removal efficiency could be achieved by using modified Fe-Mn-Ce catalytic filter material.

The genesis of acid alteration in the Luohe IOA-type deposit, Eastern China and its constraints on mineralization

Luohe is the largest IOA-type deposit in the Middle and Lower reaches of the Yangtze Metallogenic belt. The iron ore body is hosted in thick volcanic rocks, and widespread acidic alteration (secondary quartzite) developed at shallow depths, providing an excellent opportunity to study the genesis of acidic alteration rocks and the genetic links with the IOA mineralization. In this study, detailed mineralogy, in situ sulfur isotopes, and trace element analyses were performed on pyrite from a shallow drill hole in the Luohe deposit. The results indicate that the formation time of acidic alteration is between magnetite (stage II) and anhydrite-pyrite (stage IV), with pyrite sulfur isotopes ranging from −14 to 4‰, which is significantly different from those in stage IV (7-9‰). The anomaly negative sulfur isotope suggests the existence of SO2 disproportionation reaction, and the δ34S of pyrite increases with depth decrease, ultimately falling within the mantle sulfur range. This indicates that the sulfur origin of acidic alteration pyrite is a single magma sulfur source, which is significantly different from the deep iron mineralization system (magmatic + evaporite). The trace elements Co, Ni, As, Ti, Cu, Sb, Tl in pyrite indicate that the acidic alteration fluid has the characteristics of low temperature, low pH, and is rich in F and Cl. Combined with the sulfur isotope results, it is believed that pyrite in the acidic alteration rock of the Luohe was formed by the mixing of gaseous SO2 and shallow groundwater, which is a part of the Luohe magmatic-hydrothermal mineralization system and an important indication for regional exploration of similar deposits.

Dynamic detection of ppb-level SO2 based on a differential photoacoustic cell coupled with UV-LED.

We design a photoacoustic (PA) SO2 sensor based on the coupling of a differential photoacoustic cell (DPAC) and cost-effective UV-LED, which realized the dynamic monitoring of SO2 gas at the ppb level. Aiming at the limitation of UV-LED divergence, a light source combination module with high condensing efficiency was devised based on a lens through theoretical derivation and experimental analysis. The PA signal with the optimum matching of the lens was 20-times larger than the direct coupling of the UV-LED. Due to the excellent beam collimation effect of the lens assembly, the background interference was only 1 ppm. In addition, the DPAC gathered the merits of doubling the PA signal and reducing the flow noise interference. The analysis of Allan-Werle deviation showed that the detection limit of SO2 was 1.3 ppb with the averaging time of 100 s.

Improvement of sensing performance of SO2, SOF2, and SO2F2 gases on monolayer and bilayer HfSe2 under electric field

In this contribution, we use DFT simulations to gain a systematic understanding of how an external vertical electric field (E-field) affects the improvement of the sensing performance of SF6 gases on monolayer and bilayer HfSe2. The individual layered HfSe2 nanosheets' predicted band gaps and lattice constants agree with previously published results, demonstrating the validity of our theoretical framework and computational details. In the current study, it is examined the viability of stacked HfSe2 nanosheets as a candidate for detection SO2, SOF2, and SO2F2. An external E-field can facilitate the adsorption and the stability of SF6 products onto monolayer and bilayer HfSe2 nanosheets. The highest adsorption energies of SO2, SOF2, and SO2F2 on bilayer HfSe2 occurred at an E-field intensity of roughly −0.41 V/A0, with values −1.46, −1.39, and −1.16 eV, respectively. The electronic structures of the layered HfSe2 systems were seen to change as a result of the adsorption of gas molecules, where all the monolayer HfSe2 systems containing adsorbed molecules exhibited semiconductor properties with various band gaps, barring the monolayer HfSe2/SO2 system. Also, all bilayer HfSe2 systems exhibit metallic behavior in all values of E-field. Overall, these study's findings demonstrated that monolayer and bilayer HfSe2 might be utilized in techniques for the adsorption and detection of SF6 products. That bilayer HfSe2 also works to remove these gases.

Reactivity of the Intramolecular Vicinal Group-13/P- and B/Group-15-Based Frustrate Lewis Pairs with Sulfur Dioxide: Mechanistic Insight from DFT.

The emission of SO2 gas by industrialized societies contributes to the occurrence of acid rain in natural environments. In this study, we put forward a theoretical investigation into the capture reactions of SO2. Our analysis centers on the energy profiles of intramolecular 1,2-cyclohexylene-bridged FLP-associated molecules. We will particularly examine the reactions involving G13/P-based (with G13 denoting Group 13 element) and B/G15-based (with G15 representing Group 15 element) FLP-associated molecules. Except for Tl/P-FLP, B/N-FLP, and B/Bi-FLP, our theoretical examinations indicate that the remaining six FLP-associated molecules, namely G13'/P-FLP (G13' = B, Al, Ga, and In) and B/G15 ' -FLP (G15' = P, As, and Sb), can easily undergo SO2 capture reactions due to their energetic feasibility. Particularly, our theoretical findings suggested that 1,2-cyclohexylene-bridged Al/P-FLP, Ga/P-FLP, B/As-FLP, and B/Sb-FLP are capable of undergoing a reversible reaction and returning to the initial reactant state. Our theoretical evidence indicates that the G13-G15 bond length in the 1,2-cyclohexylene-linked G13/G15-FLP can serve as a basis for evaluating the free activation barrier associated with its reaction with SO2. Two theoretical methods, namely, the frontier molecular orbital theory and the energy decomposition analysis-natural orbitals of chemical valence approach, are utilized to investigate the electronic structure and bonding nature of the reactions under consideration. Moreover, the analyses based on the activation strain model revealed that it is the geometrical deformation energies of G13/G15-FLP, which is the key factor that greatly influences the activation barriers of such SO2 capture reactions. Further, our theoretical computations indicate that such capturing reactions of SO2 by intramolecular 1,2-cyclohexylene-linked G13/G15-based FLP-type molecules obey the Hammond postulate.

Intrinsic reaction selectivity between gaseous HCl and SO2 over ethanol-hydrated CaO adsorbent in coal-fired flue gas dechlorination

The reaction selectivity between HCl and SO2 on Ca-based adsorbents has attracted increasing concern for coal-fired flue gas HCl removal, while previous studies have not reached a convincing consensus. To address this knowledge gap, the reaction selectivity of HCl and SO2 over a newly-developed ethanol-hydrated CaO adsorbent was studied under series of experimental conditions. Essential factors of temperature, SO2 concentration, and products layers on the HCl reaction selectivity were revealed and the reaction pathways, thermodynamic and kinetic characteristics and turnover frequency were elucidated using DFT calculations. The results show that HCl has superior priority over SO2 to active sites. Though the opponent SO2 has thermodynamic advantage in terms of Gibbs free energy and adsorption ratios in equilibrium state, the reaction selectivity highly depends on the kinetics, where the dechlorination reaction shows larger chemical reaction rate than desulfurization reactions. The in-situ FTIR spectra indicates that HCl reacts with the desulfurized products, which exhibits the cleaning effect of sulfide product layers and benefits the high selectivity of the dechlorination reaction. The findings of competitive reaction mechanism of HCl and SO2 on Ca-based adsorbents provide a good foundation for flue gas dechlorination in commercial applications.