A review on dry-based and wet-based catalytic sulphur dioxide (SO2) reduction technologies

Triple Templates Directed Synthesis of Nitrogen-Doped Hierarchically Porous Carbons from Pyridine Rich Monomer as Efficient and Reversible SO2 Adsorbents

Herein, a variety of 2,6-diaminopyridine (DAP) derived nitrogen-doped hierarchically porous carbon (DAP-NHPC-T) prepared from carbonization-induced structure transformation of DAP-Zn-SiO2-P123 nanocomposites are reported, which are facilely prepared from solvent-free co-assembly of block copolymer templates P123 with pyridine-rich monomer of DAP, Zn(NO3)2 and tetramethoxysilane. In the pyrolysis process, P123 and SiO2 templates promote the formation of mesoporous and supermicroporous structures in the DAP-NHPC-T, while high-temperature volatilization of Zn contributed to generation of micropores. The DAP-NHPC-T possess large BET surface areas (≈956-1126 m2 g-1), hierarchical porosity with micro-supermicro-mesoporous feature and high nitrogen contents (≈10.44-5.99 at%) with tunable density of pyridine-based nitrogen sites (≈5.99-3.32 at%), exhibiting good accessibility and reinforced interaction with SO2. Consequently, the DAP-NHPC-T show high SO2 capacity (14.7 mmol g-1, 25 °C and 1.0 bar) and SO2/CO2/N2 IAST selectivities, extraordinary dynamic breakthrough separation efficiency and cycling stability, far beyond any other reported nitrogen-doped metal-free carbon. As verified by in situ spectroscopy and theoretical calculations, the pyridine-based nitrogen sites of the DAP-NHPC-T boost SO2 adsorption via the unique charge transfer, the adsorption mechanism and reaction model have been finally clarified.

Insight into the interaction between amino acids and SO2: Detailed bonding modes

CONTEXT

Amino acids are a highly effective and environmentally friendly adsorbent for SO2. However, there has been no comprehensive study of the binding modes between amino acids and SO2 at the molecular level. In this paper, the binding modes of three amino acids (Asp, Lys, and Val) with SO2 are studied comprehensively and in detail using quantum chemical calculations. The results indicate that each amino acid has multiple binding modes: 22 for Asp, 49 for Lys, and 10 for Val. Both the amino and carboxyl groups in amino acids, as well as those in side chains, can serve as binding sites for chalcogen bonds. The binding energies range from - 6.42 to - 1.06 kcal/mol for Asp, - 12.43 to - 1.63 kcal/mol for Lys, and - 7.42 to - 0.60 kcal/mol for Val. Chalcogen and hydrogen bonds play a crucial role in the stronger binding modes. The chalcogen bond is the strongest when interacting with an amino group, with an adiabatic force constant of 0.475 mDyn/Å. Energy decomposition analysis indicates that the interaction is primarily electrostatic attraction, with the orbital and dispersive interactions dependent on the binding mode.

METHODS

Amino acids and complexes of amino acids with SO2 were used to do semi-empirical MD using Molclus combined with xtb at the GFN2 level. Optimization and frequency calculations of the structures were conducted using density-functional theory (DFT) B3LYP/6-311G* (with DFT-D3 correction). Single-point energy calculations were performed for all structures using DLPNO-CCSD(T)/aug-cc-pVTZ with tightPNO. Further analysis of the structures was conducted using ESP, AIM, IGMH, and sob-EDA to gain a deeper understanding of the interactions between amino acids and SO2.

A novel colorimetric fluorescent probe for sensing bisulfite detection in plant and zebrafish

Sulfur dioxide (SO2) and its derivatives (SO32- and HSO3-), are important active sulfur species that play significant roles in physiological processes. Fluorescence probe imaging technology, due to its high temporal and spatial resolution, real-time non-invasive and non-destructive detection, has emerged as a valuable tool for studying SO2 in biological systems. In this study, we presented a colorimetric fluorescent probe for the detection of HSO3-. The structure of probe TPN-BP consists of a triphenylamine group and a benzopyrylium group that are connected by a vinyl double bond. The benzopyrylium group in probe TPN-BP, which carries a positive charge, serves two important functions: enhancing water solubility, allowing for its effective use in fully aqueous environments, and acting as a fluorescence quencher for the triphenylamine group. Upon interaction with HSO3-, probe TPN-BP exhibited significantly increase in fluorescence at 480 nm, causing the solution to change from blue to colorless. Spectral experiments showed that probe TPN-BP showed quick response time (10 s), high sensitivity (12.7 nM), and excellent selectivity towards HSO3-. It is worth noting that probe TPN-BP has been successfully used for fluorescence imaging and detection of HSO3- in plants and zebrafish. The results of this study indicated that probe TPN-BP can be used as a promising tool for the research and monitoring of SO2 in living organisms.

Roles of the Comproportionation Reaction in SO2 Reduction Using Methane for the Flexible Recovery of Elemental Sulfur or Sulfides

SO2 reduction with CH4 to produce elemental sulfur (S8) or other sulfides is typically challenging due to high energy barriers and catalyst poisoning by SO2. Herein, we report that a comproportionation reaction (CR) induced by H2S recirculating significantly accelerates the reactions, altering reaction pathways and enabling flexible adjustment of the products from S8 to sulfides. Results show that SO2 can be fully reduced to H2S at a lower temperature of 650 °C, compared to the 800 °C required for the direct reduction (DR), effectively eliminating catalyst poisoning. The kinetic rate constant is significantly improved, with CR at 650 °C exhibiting about 3-fold higher value than DR at 750 °C. Additionally, the apparent activation energy decreases from 128 to 37 kJ/mol with H2S, altering the reaction route. This CR resolves the challenges related to robust sulfur-oxygen bond activation and enhances CH4 dissociation. During the process, the well-dispersed lamellar MoS2 crystallites with Co promoters (CoMoS) act as active species. H2S facilitates the comproportionation reaction, reducing SO2 to a nascent sulfur (Sx*). Subsequently, CH4 efficiently activates CoMoS in the absence of SO2, forming H2S. This shifts the mechanism from Mars-van Krevelen (MvK) in DR to sequential Langmuir-Hinshelwood (L-H) and MvK in CR. Additionally, it mitigates sulfation poisoning through this rapid activation reaction pathway. This unique comproportionation reaction provides a novel strategy for efficient sulfur resource utilization.

Effect of temperature on the reaction path of pyrite (FeS2)-based catalyst catalyzed CO reduction of SO2 to sulfur

To understand the physical phase structural variation and activation pathway of the active component during the catalytic reduction of pyrite (FeS2)-based catalysts, multiple methods, including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and high-temperature in situ XRD, were applied to characterize the catalyst and reaction process. The reaction mechanism was simulated and verified using density functional theory. The results indicated that pyrite-based catalysts promote the CO reduction of SO2 to S through the dynamic transformation of three phases (FeS2, Fe7S8, and FeS), in which S-vacancy formation is the most important step. As the critical temperature for the reaction of FeS2 and CO was initiated at approximately 525 °C, the active component's physical phase structure and activation pathway could be controlled by adjusting the temperature.

Metal-Redox Bicatalysis Batteries for Energy Storage and Chemical Production

New types of electrochemical energy conversion and storage devices based on redox electrocatalytic reactions possess great potential in renewable energy to maximize energy utilization and balance environmental issues. The typical device is the metal-redox bicatalysis battery, where the cathode is redox bifunctional catalyst (named as redox bicatalyst) with gas, solid, liquid as active reactants while anode is metal, driven by cathodic redox electrocatalytic reactions during charge/discharge processes, which promotes the energy storage and chemical production. In this system, the metal anode, redox-bicatalyst cathode, electrolytes, and the redox electrochemical reactions can be modified and adjusted to achieve the optimal energy conversion and utilization. Therefore, the deep understanding of the electrochemical system is conducive to designing new devices to meet the demand among various applications, including energy storage and conversion. In this review, the authors clarify the fundamentals and design principles of the rechargeable/reversible metal-redox bicatalysis batteries and how each part affects the devices in energy conversion and chemical production. The authors summarize the electrocatalytic reduction/oxidation reactions, the reported systems relied on redox reactions, and the corresponding redox bicatalysts. Finally, a perspective of the key challenges and the possible new types of metal-redox bicatalysis batteries for efficient energy utilization and chemical production are given.

Valorization of lignocellulosic biomass into sustainable materials for adsorption and photocatalytic applications in water and air remediation

An exponential rise in global pollution and industrialization has led to significant economic and environmental problems due to the insufficient application of green technology for the chemical industry and energy production. Nowadays, the scientific and environmental/industrial communities push to apply new sustainable ways and/or materials for energy/environmental applications through the so-called circular (bio)economy. One of today's hottest topics is primarily valorizing available lignocellulosic biomass wastes into valuable materials for energy or environmentally related applications. This review aims to discuss, from both the chemistry and mechanistic points of view, the recent finding reported on the valorization of biomass wastes into valuable carbon materials. The sorption mechanisms using carbon materials prepared from biomass wastes by emphasizing the relationship between the synthesis route or/and surface modification and the retention performance were discussed towards the removal of organic and heavy metal pollutants from water or air (NO_x, CO₂, VOCs, SO₂, and Hg⁰). Photocatalytic nanoparticle-coated biomass-based carbon materials have proved to be successful composites for water remediation. The review discusses and simplifies the most raised interfacial, photonic, and physical mechanisms that might take place on the surface of these composites under light irradiation. Finally, the review examines the economic benefits and circular bioeconomy and the challenges of transferring this technology to more comprehensive applications.