Formation Of SO Research Articles

Boosting SO2-tolerance of Mn-doped CeO2-ZrO2 for Hg catalytic oxidation via NaOH etching

Manganese-doped CeO2-ZrO2 solid solution (CZM) is a prominent sorbent for extracting Hg0 from flue gas, operating optimally around 150 °C, but impaired by SO2 exposure. In this research, we apply a hydrothermal method, employing a sodium hydroxide (NaOH) solution, to enhance CZM's SO2 resilience. The detrimental effect of SO2 on CZM primarily arises from the reduction of active oxygen species, diminishing Hg0 removal efficacy. After conducting a 10-hour test in the atmosphere comprising N2, 6 %O2, and 500ppmSO2, the mercury removal efficiency of the unmodified CZM significantly decreased from ∼99.5 % to ∼26.0 %. Conversely, the modified sorbents, designated as CZM-1M, demontrasted enhanced stability, with its mercury removal efficiency modestly reducing from ∼97 % to ∼60 %. We then conducted comprehensive characterizations of both sorbents to understand the mechanism behind this improved SO2 tolerance. In CZM-1M, we noted an enhanced conversion rate from Ce4+ to Ce3+, a key factor in boosting the production of active oxygen species, necessary for Hg0 oxidation. Additionally, the formation of SO3 - a result of the interaction between the abundant oxygen species and SO2 - emerged as a novel active site that further promoted Hg0 oxidation. This shift in active site offers a pathway for enhancing SO2 resistance in such material.

Direct observation of the complex S(IV) equilibria at the liquid-vapor interface

The multi-phase oxidation of S(IV) plays a crucial role in the atmosphere, leading to the formation of haze and severe pollution episodes. We here contribute to its understanding on a molecular level by reporting experimentally determined pKa values of the various S(IV) tautomers and reaction barriers for SO2 formation pathways. Complementary state-of-the-art molecular-dynamics simulations reveal a depletion of bisulfite at low pH at the liquid-vapor interface, resulting in a different tautomer ratio at the interface compared to the bulk. On a molecular-scale level, we explain this with the formation of a stable contact ion pair between sulfonate and hydronium ions, and with the higher energetic barrier for the dehydration of sulfonic acid at the liquid-vapor interface. Our findings highlight the contrasting physicochemical behavior of interfacial versus bulk environments, where the pH dependence of the tautomer ratio reported here has a significant impact on both SO2 uptake kinetics and reactions involving NOx and H2O2 at aqueous aerosol interfaces.

In Situ Generatable and Recyclable Oxygen Vacancy-Modified Fe2O3-Decorated WO3 Nanowires with Super Stability for ppb-Level H2S Sensing.

Detecting hydrogen sulfide (H2S) odor gas in the environment at parts-per-billion-level concentrations is crucial. However, a significant challenge is the rapid deactivation caused by SO42- deposition. To address this issue, we developed a sensing material comprising Fe2O3-decorated WO3 nanowires (FWO) with strong interfacial interaction. During the H2S sensing process, important oxygen vacancies (OVs) are generated in situ and are recyclable on the surface of the Fe2O3 cluster. This sensor achieves a response of 140 (Ra/Rg) toward 50 ppm of H2S at 250 °C, with an experimentally measured detection limit of 1 ppb. It also exhibits remarkable stability, with no significant change observed over a long period of 150 days. Based on a combination of in situ DRIFT and DFT calculations, we have identified that the overactivation of O2 is the key step in the formation of SO42-. This overactivation can be partially modulated by the synergistic effect of Fe2O3 decoration and the in situ generated OVs, regulating the oxidation product to SO2 rather than the toxic SO42-. Furthermore, the continuous generation of OVs compensates for the loss of active sites pertaining to SO42- deposition, thereby contributing to the excellent stability of the sensor. This study underscores the beneficial impact of in situ OV generation in FWO for H2S sensing, offering a dynamic strategy to enhance sensor performance, particularly in terms of stability.

Sulfur fixation performance of calcium-bearing carbonates in iron ore roasting process: Thermodynamics, phase transition, microstructure evolution, and kinetics

Roasting technology is increasingly used in the beneficiation of refractory iron ores. During the roasting process, the presence of pyrite in some iron ores leads to the formation of SO2, requiring effective sulfur fixation techniques. This study proposed an innovative in-situ sulfur fixation method by pre-oxidation roasting, in which sulfur was fixed during the oxidation roasting process before reduction roasting. The effects of the main iron mineral (hematite), primary gangue mineral (quartz), and common calcium-containing carbonate minerals (calcite and dolomite) on sulfur migration during pyrite roasting were investigated, with particular emphasis on the sulfur fixation capabilities of calcite and dolomite. The study included thermodynamic equilibrium analysis, phase transitions and microstructural evolution in different reaction systems. The results showed that calcite and dolomite effectively reduced SO2 emissions by forming CaSO4 and MgSO4, with calcite exhibiting a stronger sulfur fixation capacity for the same mass. Kinetic analysis indicated that pyrite pyrolysis followed a two-step random nucleation and growth model. Furthermore, the addition of calcite increased the apparent activation energy of SO2 formation and altered the reaction pathway, providing insight into the sulfur fixation mechanism of calcite from a kinetic perspective.

Effect of calcite on the thermal decomposition of pyrite: Thermodynamics, phase transformation, microstructure evolution and kinetics

Pyrite, a common iron mineral in refractory iron ores, emits SO2 during oxidative roasting, contributing to environmental pollution. This study investigated the effect of calcite on the thermal decomposition of pyrite, focusing on thermodynamics, phase transformation, microstructural evolution, and non-isothermal kinetics, with emphasis on SO2 formation inhibition. Results showed that pyrite decomposed first to pyrrhotite, then to magnetite and hematite, with SO2 as the primary gaseous product. Higher temperatures and lower oxygen concentrations favored S2 gas formation. Non-isothermal decomposition of pyrite occurred between 400–725°C, initiated at the particle surface, and significantly increased product porosity, resulting in butterfly-shaped hematite. The addition of calcite resulted in the reaction of SO2 with calcite to form anhydrite on the particle surface, inhibiting the release of SO2. Initially, the thermal decomposition of pyrite proceeded with a low apparent activation energy, making the reaction relatively easy. However, the presence of calcite significantly increased the apparent activation energy and inhibited the thermal decomposition reaction.

Seasonal simulation and source apportionment of SO42− with integration of major highlighted chemical pathways in WRF-Chem model in the NCP

Particulate sulfate (SO42−) is the major component of fine particles in the North China Plain (NCP). It plays an essential role in the entire atmosphere and climate system. Accurately reproducing the SO42− levels is challenging for chemical transport model. Here, the major highlighted multiple phase SO42− formation pathways are integrated into the WRF-Chem model and seasonal model performance of SO42− are assessed by observed SO42− at multiple sampling sites located in the NCP. The results show that the integration of these SO42− formation pathways obviously narrow the gap between simulation and observation in autumn, winter, and summer at three sampling sites in the NCP, for high RH conditions facilitate the hygroscopic growth of PM2.5 and promote the multiple phase reaction to form SO42−. The underestimation in autumn, winter, and summer may ascribe to the missed SO42− source from photo-induced chemical route and missed hygroscopicity of organic aerosols. The obviously discrepancy between simulation and observation in spring may ascribe to the large underestimation of SO2 levels and lack consideration of dust scheme. Source apportionment results show that the gas phase reaction played a vital role in the formation of SO42− in each season. The contribution of aqueous phase SO2 oxidation by H2O2 is higher in autumn and summer due to simultaneously high RH levels and stronger photochemical reaction activity. The Mn(II) catalytic SO2 oxidation pathway at the particle interface is important in autumn and make greater contribution to SO42− formation during winter severe haze events under extremely high RH levels.

In-situ inhibition mechanism of SO3 formation over MoS2 modified V2O5/TiO2 catalyst within selective catalytic reduction process

The utilization of commercial vanadium-titanium based catalysts (V2O5/TiO2) within the selective catalytic reduction (SCR) process is a prominent contributor to the emergence of sulfur trioxide (SO3) in coal-fired boiler environments. The direct modification of vanadium-titanium based catalysts has big potential to be an efficacious strategy for in-situ inhibiting SO3 formation. This research evaluates the effectiveness of MoS2 modified V2O5/TiO2 catalyst on SO2 oxidation under diverse conditions, using controlled condensation for SO3 collection. The results showed that V2O5-MoS2/TiO2 catalysts outperformed conventional V2O5/TiO2 catalysts in inhibiting the oxidation from SO2 to SO3 between 200 and 400 °C, with optimal performance at 350 °C. No significant effect was observed on the catalytic oxidation of SO2 when the O2 concentration was lower than that of SO2, whereas the introduction of appropriate quantities of NO promoted the generation of SO3. The excessive inclusion of NH3 nearly doubled the SO3 generation rate, increasing it from 0.284 % to 0.434 %. The NO and NH3 mixture markedly reduced SO3 generation to 0.085 % at a 62 mL/min mixture concentration, just 30 % of the rate without the mixture. Following the reaction of SO2 and O2, the reacted catalyst exhibited reduced pore volume, enhanced thermochemical stability, and lower susceptibility to SO2 catalytic oxidation. The addition of low-valence sulfur improves catalyst reducibility, reduces V5+–OH reactions in various atmospheres, and decreases the formation of sulphate and gaseous SO3. The Mo-S-Mo group also effectively prevents the formation of HSO4− intermediates. Additionally, MoS2 reacts with SO3 via a reduction reaction, significantly lowering the SO3 levels. Finally, in diverse atmospheric conditions, the catalysts maintained their V5+ content and catalytic efficiency, thus improving SCR performance stability.

Two-dimensional transition metal-sulfide-modified V2O5-WS2/TiO2 catalysts for SCR: Comprehensive mechanistic insights into the in situ inhibition of SO3 generation

The by-product SO3, generated by the conventional catalyst V2O5-WO3/TiO2 employed in selective catalytic reduction (SCR) systems, has garnered attention in pollution control efforts. Studies on existing control have predominantly concentrated on the tail gas section, with insufficient understanding of in-situ suppression theories and methods at the source of SO3 generation. We propose for the first time the introduction of low-valence reduced sulfur to synthesize a novel SCR catalyst, V2O5-WS2/TiO2, which elucidates the remarkable effect and in-situ mechanism of action in inhibiting SO3 formation at its source. Compared to conventional catalysts, the new catalysts showed enhanced SO3 inhibition, particularly at 350 °C, where SO3 production was 64.1 % and 33.9 % lower than that with VTi and VW/Ti catalysts, respectively. This was due to their reduced surface area, smaller pore volume, and fewer alkaline sites, which hindered SO2 adsorption and oxidation. The results revealed that S2− on the catalyst surface reacts with V5+, reducing it to V4+ and V3+. This reaction hinders the interaction between V5+-OH and adsorbed SO2, thereby reducing the formation of VOSO4 intermediates. Furthermore, the WS bond in WS2 impedes the formation of intermediate HSO4−, and the reduction of these intermediates ultimately leads to a decrease in SO3 generation. Additionally, the incompletely depleted S2− reacts with the final SO3 produced, forming SO2 and SO42−, which further decreases the SO3 generation rate and supports the maintenance of a reduced state on the catalyst surface. It is evident that low-valence reduced sulfur plays a crucial role in inhibiting SO3 generation.

Correlation between Thermodynamic Studies and Experimental Process for Roasting Cobalt-Bearing Pyrite

Cobalt is a critical metal widely distributed in nature, but cobalt ore has hardly been found as an independent mineral. Cobalt-bearing pyrite tailings separated from iron ore is one of the resources for recovering cobalt. In the following study, roasting is carried out to oxidize cobalt-bearing pyrite tailings for preparing and recovering the cobalt by acid leaching. The further aim of the research is to determine and control the optimal technological regime for roasting by using thermodynamic modeling. The phase transition in Fe–S–O and Co–S–O systems and its mechanism are analyzed under the partial pressure of oxygen and sulfur dioxide at constant temperatures. Thermodynamic modeling proves that iron and cobalt sulfides can be intensively oxidized at a relatively high temperature (>900 °C) under an atmosphere of logp(O2) > −5, leading to the formation of SO2 (logp(SO2) < 0). The results of the roasting experiment indicate 98% desulfurization degree upon holding for about 4–5 h and at > 1000 °C. Based on these thermodynamic modeling and experimental results, the roasting of cobalt containing pyrite can be optimized with substantial productivity with regard to the metal oxide and cobalt thereof. Oxidative roasting also allows the elimination of environmentally hazardous gases such as sulfur during the process.

ZnO enhanced molten Na2CO3-K2CO3 system for simulated waste resins treatment: Efficient conversion and fixation of organic sulfur and iron(III)

The radioactive spent resins from pressurized water nuclear power plant always contain a significant proportion of 55Fe, which invariably leads to the release of radionuclides and acidic gases if not treated promptly. Herein, an efficient ZnO enhanced molten salt oxidation (MSO) method was established for the removal and fixation of organic sulfur and Fe in simulated radioactive resins containing Fe3+ (Fe-CERs). The existence of Fe3+ facilitates the reaction with O2 to form Fe2O3, which contributes to the fracture of organic skeleton. The comparative study was conducted to explore the impact of ZnO on the oxidation behavior of Fe and S at 600–800 °C. The introduction of ZnO caused the continuous formation of ZnS at 600–700 °C, and the conversion of ZnO at 800 °C indirectly promotes the retention rate of S (85.42 %). The potential conversion of Zn0.73Fe0.27S to ZnS may occur within the temperature range of 700 °C to 800 °C. Additionally, the predominant presence of carbon in residues at approximately 700 °C could exert a stimulating effect on the sulfidation process of Fe2O3 and inhibit the formation of SO2. The coexistence of Fe2O3, carbon and ZnO effectively diminishes H2S and SO2 amounts while further enhancing the fixation of S and Fe. The increase generation of K2SO4, FeS and Fe3O4 leads to a high formation rate of SO42- (79.36 %) and a great retention efficiency of Fe (96.23 %) at 800 °C. The proposed novel MSO method holds promising potential for applications in the treatment of organic contaminants.

Gas-phase F-atom migration reaction of deprotonated N-fluoroarenesulfonamides.

Recently N-Fluoroarenesulfonamides (ArSO2 NHF) were found to be promising precursors for the preparation of N-fluorobenzenesulfonimide derivatives without applying F2 . However, very few studies have discussed the mass spectrometric behaviors of ArSO2 NHF with N-F structure. In this article, we applied high-resolution electrospray ionization tandem mass spectrometry (HR-ESI-MS/MS) to study the effect on the mass spectrometric behaviors of ArSO2 NHF after the introduction of the F-atom to the N-atom of ArSO2 NH2 . High-resolution electrospray ionization mass spectrometry (HR-ESI-MS) experiments showed that ArSO2 NHF produced only good signals in negative ion mode, and the dominating product ion SO2 F- at m/z 83 was observed in all HR-ESI-MS/MS of ArSO2 NF- with different substituents in the Ar group. The formation of the product ion SO2 F- was proof of the gas-phase F-atom migration rearrangement from the N-atom to the S-atom in ESI-MS/MS of ArSO2 NF- . To fully explain the gas-phase reaction mechanism from ArSO2 NF- to SO2 F- , we studied the HR-ESI-MS/MS of deprotonated ArSO2 NHF and also performed theoretical calculations. Both results confirmed that ArSO2 NF- first underwent Smiles rearrangement to yield intermediate I (INT1) ArNFSO2 - , and then the F-atom of ArNFSO2 - migrated from the N-atom to the S-atom to form intermediate II (INT2) ArN- SO2 F, which finally dissociated to SO2 F- at m/z 83 with loss of a neutral nitrene (ArN). All these results showed that the formation of the product ion SO2 F- from ArSO2 NF- was a common and intrinsic gas-phase reactivity of ArSO2 NF- .

Chamber studies of OH + dimethyl sulfoxide and dimethyl disulfide: insights into the dimethyl sulfide oxidation mechanism.

The oxidation of dimethyl sulfide (DMS) in the marine atmosphere represents an important natural source of non-sea-salt sulfate aerosol, but the chemical mechanisms underlying this process remain uncertain. While recent studies have focused on the role of the peroxy radical isomerization channel in DMS oxidation, this work revisits the impact of the other channels (OH addition and OH abstraction followed by bimolecular RO2 reaction) on aerosol formation from DMS. Due to the presence of common intermediate species, the oxidation of dimethyl sulfoxide (DMSO) and dimethyl disulfide (DMDS) can shed light on these two DMS reaction channels; they are also both atmospherically relevant species in their own right. This work examines the OH oxidation of DMSO and DMDS, using chamber experiments monitored by chemical ionization mass spectrometry and aerosol mass spectrometry to study the full range of sulfur-containing products across a range of NO concentrations. The oxidation of both compounds is found to lead to rapid aerosol formation (which does not involve the intermediate formation of SO2), with a substantial fraction (14%-47 % S yield for DMSO and 5 %-21 % for DMDS) of reacted sulfur ending up in the particle phase and the highest yields observed under elevated NO conditions. Aerosol is observed to consist mainly of sulfate, methanesulfonic acid, and methanesulfinic acid. In the gas phase, the NOx dependence of several products, including SO2 and S2-containing organosulfur species, suggest reaction pathways not included in current mechanisms. Based on the commonalities with the DMS oxidation mechanism, DMSO and DMDS results are used to reconstruct DMS aerosol yields; these reconstructions roughly match DMS aerosol yield measurements from the literature but differ in composition, underscoring remaining uncertainties in sulfur chemistry. This work indicates that both the abstraction and addition channels contribute to rapid aerosol formation from DMS and highlights the need for more study into the fate of small sulfur radical intermediates (e.g., CH3S, CH3SO2, and CH3SO3) that are thought to play central roles in the DMS oxidation mechanism.

Application Study on the Activated Coke for Mercury Adsorption in the Nonferrous Smelting Industry

The massive release of mercury undermines environmental sustainability, and with the official entry into force of the Minamata Convention, it is urgent to strengthen the control of mercury pollution. The effectiveness of activated coke (AC) in removing elemental mercury (Hg0) from high temperatures and sulfur nonferrous smelting flue gas before acid production was studied. Experimental results indicated that the optimal temperature for Hg0 adsorption by AC was 150 °C. And the adsorption of Hg0 by AC was predominantly attributed to physical adsorption. Flue gas components (SO2 and O2) impact studies indicated that O2 did not significantly affect Hg0 adsorption compared to pure N2. Conversely, SO2 suppressed the adsorption capacity, while the simultaneous presence of SO2 and O2 exhibited a synergistic effect in facilitating the removal of Hg0. The characterization results of X-ray photoelectron spectroscopy (XPS) indicated that the SO2 molecule favored to anchor at the Oα site, leading to the formation of SO3. This subsequently oxidized the mercury to HgSO4 instead of HgO. The study demonstrates that cheap and easily accessible AC applications in the adsorption of mercury technology may help improve the sustainability of the circular economy and positively impact various environmental aspects.

Environmental Impacts of Emissions Streams Within the Ironmaking in Understanding SOX and NOX Formation Using Factsage Software

The manufacturing process of coke in steel plants, emits SOx and NOx which contributes around 30% of the total environmental pollution. The environmental norms from the Central Pollution Control Board of India may implement stringent norms on steel plants for their emission into its environment. In the present study, fact sage software was used for stimulating and quantifying the emissions like SOX and NOX in volume % by incorporating different possible operating parameters such as – its composition, suction pressure, flow rate, and fuel-to-air ratio. The simulation results were also compared with the plant data. The result showed peak flame temperature increased and also shifted toward a lower mixed gas-to-air-to-fuel ratio, indicating the combustion product at different mixed gas-to-air ratios. At an increased % of coke oven gas in mixed gas at a higher value of the mixed gas to air ratio, the percentage volume of COG was reduced. The new aspect of this work involves using a higher ratio of mixed gas to air, increasing the proportion of COG (carbonaceous gas) in the mixture, reducing the volume of CO2 produced, and increasing the formation of CO and SO2, indicating incomplete burning of hydrocarbons. However, when the COG decreases and the ratio of mixed gas to air increases, it leads to higher emissions of NOX. In the study the CEMS data matches with simulated results.

Kinetic study of isoprene hydroxy hydroperoxide radicals reacting with sulphur dioxide and their global-scale impact on sulphate formation.

Isoprene is the most relevant volatile organic compound emitted during the biosynthesis of metabolism processes. The oxidation of isoprene by a hydroxy radical (OH) is one of the main consumption schemes that generate six isomers of isoprene hydroxy hydroperoxide radicals (ISOPOOs). In this study, the rate constants of ISOPOOs + sulphur dioxide (SO2) reactions that eventually generate sulphur trioxide (SO3), the precursor of sulphate aerosol (SO42-(p)), are determined using microcanonical kinetic theories coupled with molecular structures and energies estimated by quantum chemical calculations. The results show that the reaction rates range from 10-27 to 10-20 cm3 molecule-1 s-1, depending on the atmospheric temperature and structure of the six ISOPOO isomers. The effect of SO3 formation from SO2 oxidation by ISOPOOs on the atmosphere is evaluated by a global chemical transport model, along with the rate constants obtained from microcanonical kinetic theories. The results show that SO3 formation is enhanced in regions with high SO2 or low nitrogen oxide (NO), such as China, the Middle East, and Amazon rainforests. However, the production rates of SO3 formation by ISOPOOs + SO2 reactions are eight orders of magnitude lower than that from the OH + SO2 reaction. This is indicative of SO42-(p) formation from the direct oxidation of SO2 by ISOPOOs, which is almost negligible in the atmosphere. The results of this study entail a detailed analysis of SO3 formation from gas-phase reactions of isoprene-derived products.

Homogeneous oxidation of SO2 in the tail gas incinerator of sulfur recovery unit

The formation and emission of sulfur trioxide (SO3) in sulfur recovery unit has received increasing attention due to its adverse effects on the operation of plant and environment. Due to the excess oxygen, high concentration of SO2 and high temperature, SO3 formation in the sulfur recovery unit tail gas incinerator may significantly increase. A small horizontal tube reactor was employed to simulate the homogeneous oxidation of SO2 in the tail gas incinerator. The SO3 concentration was measured with a controlled condensation method at the outlet of the reactor. The present work focuses on the gas-phase chemistry and examines the impact of different combustion parameters and atmospheres on the formation of SO3 in the tail gas incinerator. Experiment results show that the increased O2 and SO2 concentrations along with increasing temperature are favorable for enhancing SO3 formation over the range of tested parameters. The presence of water vapor has an enhancing effect of SO2 oxidation in the experiments conducted. No significant effect of CO2 was found to the oxidation of SO2.

Aerosol acidity and its impact on sulfate and nitrate of PM2.5 in southern city of Beijing-Tianjin-Hebei region

Aerosol acidity, similar to the pH of a solution, influences the water-phase reactions within aerosols, thereby impacting the formation and composition of particle components. This study investigated the chemical composition of PM2.5, pH of PM2.5 and its impact on formation of SO42− and NO3− in Handan city from March 2015 to February 2016. The results showed that NO3− was the dominant inorganic secondary ion in PM2.5, accounting for 16.4% of PM2.5, slightly higher than SO42− at 14.2%. The average pH of PM2.5 in Handan was 4.3, indicating moderate acidity, with higher acidity observed in spring and winter. Nitrogen oxidation ratio (NOR) was synergistically influenced by pH and aerosol water content (AWC), while sulfur oxidation ratio (SOR) was associated with high aerosol acidity or AWC. The activity coefficient of NO3− exhibited a negative correlation with activity coefficient of [H+], with an R2 value of −0.20 (“-” means negative correlation). Conversely, a positive correlation was observed between activity coefficient of SO42− and [H+], with an R2 value of 0.19. The partition coefficient (ε(NO3−)) of nitrate, representing its assignment to the solid phase, is given by the function y = −0.5x2+4.2x-7.6 (R2 = 0.60), where x corresponds to pH and y corresponds to ε(NO3−). It suggested that NO3− is most likely to enter the solid phase in significant quantities under moderately acidity condition (at around pH = 4.2). A significant correlation observed between pH, surface tension, and particle radius, indicating that pH influences the aging process of aerosols. However, the impact of pH varies depending on the pollution episode.

Effect of ammonia and coal co-firing on the formation mechanism and composition characteristics of particulate matter

Ammonia-coal co-firing is considered to be an effective method to reduce carbon dioxide emissions and the existing researches mainly focus on the combustion characteristics and NOx emission characteristics. In this study, co-firing of coal and ammonia was carried out in the high temperature drop tube furnace system with a large co-firing ratio of 0–50%. Firstly, the unburned fuels and the main composition of flue gas were measured as a baseline result. The results showed that ammonia co-firing will lead to the increase of NO and NOx concentration. Further, the particulate matters generated under different conditions were collected and tested. It was found that ammonia co-firing will affect the formation characteristics of particulate matter, especially sub-micron particulate matter. With the increase of co-firing ratio, the concentration of PM1 showed an overall increasing trend, but decreased at 20%. And ammonia co-firing will have an effect on the content of Si, Al, S and trace elements (As, Pb) in submicron particles. The content of water vapor, NOx in flue gas and combustion temperature have changed and affected the formation of SO3 and the gasification of silica and trace elements.

Multiple oxyanions modification on nickel–iron layered double hydroxides for enhanced oxygen evolution reaction

The electrochemical oxygen evolution reaction (OER) holds paramount significance as a pivotal stage within electrochemical water-splitting processes, particularly in hydrogen production. Highly efficient OER electrocatalysts with inherent capability to effectively lower the energy barrier and promote fast kinetics are in high demand. In this research, we have introduced a novel strategy of modifying the non-precious metal benchmark catalyst, NiFe layered double hydroxide (LDH), through multiple oxyanions. Our approach involved incorporating MoS42− as a source of modified anions to enhance the performance of LDH in OER. Under specific conditions of the hydrothermal reaction, a majority of the sulfur (S) within the MoS42− anions underwent oxidization, resulting in the formation of SO42− and MoOxS4-x2- groups. As a result, NiFe LDH composites that were modified with multiple oxyanionic moieties, were successfully fabricated. Thanks to the synergistic effects of these oxyanions, which accelerate the generation of active NiOOH species, the optimized NiFe LDH-MoS4-0.1/NF sample exhibited a significantly low overpotential of 228 and 270 mV at current densities of 10 and 100 mA cm−2, respectively, along with a low Tafel slope of 35.5 mVdec−1 in 1 M KOH electrolyte solution. Our study underscored the importance of embracing diverse oxyanions modification strategy to amplify the performance of OER, opening up numerous opportunities for energy conversion and storage applications.

Bimolecular Reaction of Methyl-Ethyl-Substituted Criegee Intermediate with SO2.

Methyl-ethyl-substituted Criegee intermediate (MECI) is a four-carbon carbonyl oxide that is formed in the ozonolysis of some asymmetric alkenes. MECI is structurally similar to the isoprene-derived methyl vinyl ketone oxide (MVK-oxide) but lacks resonance stabilization, making it a promising candidate to help us unravel the effects of size, structure, and resonance stabilization that influence the reactivity of atmospherically important, highly functionalized Criegee intermediates. We present experimental and theoretical results from the first bimolecular study of MECI in its reaction with SO2, a reaction that shows significant sensitivity to the Criegee intermediate structure. Using multiplexed photoionization mass spectrometry, we obtain a rate coefficient of (1.3 ± 0.3) × 10-10 cm3 s-1 (95% confidence limits, 298 K, 10 Torr) and demonstrate the formation of SO3 under our experimental conditions. Through high-level theory, we explore the effect of Criegee intermediate structure on the minimum energy pathways for their reactions with SO2 and obtain modified Arrhenius fits to our predictions for the reaction of both syn and anti conformers of MECI with SO2 (ksyn = 4.42 × 1011 T-7.80exp(-1401/T) cm3 s-1 and kanti = 1.26 × 1011 T-7.55exp(-1397/T) cm3 s-1). Our experimental and theoretical rate coefficients (which are in reasonable agreement at 298 K) show that the reaction of MECI with SO2 is significantly faster than MVK-oxide + SO2, demonstrating the substantial effect of resonance stabilization on Criegee intermediate reactivity.