Enhancing AsH3 Detoxification via Electron-Deficient [NiIII-OH (μ-O)] in a Nickel-Modified NaY Zeolite: A Pathway toward As0 Products

The transformation of toxic arsine (AsH3) gas into valuable elemental arsenic (As0) from industrial exhaust gases is important for achieving sustainable development goals. Although advanced arsenic removal catalysts can improve the removal efficiency of AsH3, toxic arsenic oxides generated during this process have not received adequate attention. In light of this, a novel approach for obtaining stable As0 products was proposed by performing controlled moderate oxidation. We designed a tailored Ni-based catalyst through an acid etching approach to alter interactions between Ni and NaY. As a result, the 1Ni/NaY-H catalyst yielded an unprecedented proportion of As0 as the major product (65%), which is superior to those of other reported catalysts that only produced arsenic oxides. Density functional theory calculations clarified that Ni species changed the electronic structure of oxygen atoms, and the formed [NiIII-OH (μ-O)] active centers facilitated the adsorption of AsH2*, AsH*, and As* reaction intermediates for As-H bond cleavage, thereby decreasing the direct reactivity of oxygen with the arsenic intermediates. This work presents pioneering insights into inhibiting excessive oxidation during AsH3 removal, demonstrating potential environmental applications for recovery of As0 from toxic AsH3.

Defect-Confinement Strategy for Constructing CuO Clusters on Carbon Nanotubes for Catalytic Oxidation of AsH3 at Room Temperature

The efficient removal of the highly toxic arsine gas (AsH3) from industrial tail gases under mild conditions remains a formidable challenge. In this study, we utilized the confinement effect of defective carbon nanotubes to fabricate a CuO cluster catalyst (CuO/ACNT), which exhibited a capacity much higher than that of CuO supported on pristine multiwalled carbon nanotubes (MWCNT) (CuO/PCNT) for catalytically oxidizing AsH3 under ambient conditions. The experimental and theoretical results show that nitric acid steam treatment could induce MWCNT surface structural defects, which facilitated more stable anchoring of CuO and then improved the oxygen activation ability, therefore leading to excellent catalytic performance. Density functional theory (DFT) calculations revealed that the catalytic oxidation of AsH3 proceeded through stepwise dehydrogenation and subsequent recombination with oxygen to form As2O3 as the final product.

Decomposition of Thermally Stable Fuel Using a Cerium-Modified Zeolite Catalyst and Endothermic Characteristics

The increase in the speed of aircraft causes a thermal load in the system. A cooling system is needed to solve this. Proactively, research is being conducted to cool the thermal load through the endothermic reaction of aircraft fuel. The decomposition of thermally stable fuel was performed using a lanthanide-modified zeolite as a catalyst, which was coated onto metal foam and the inner wall of a tube reactor to confirm the endothermic characteristics of the catalytic decomposition reaction. When a cerium-modified zeolite was used, the heat sink was increased to 1100Btu/lb and showed excellent performance for the cracking reaction.

Catalytic oxidation mechanism of AsH3 over CuO@SiO2 core-shell catalysts via experimental and theoretical studies

In this study, CuO@SiO₂ core-shell catalysts were successfully synthesized and applied to efficiently remove hazardous gaseous pollutant arsine (AsH₃) by catalytic oxidation under low-temperature and low-oxygen conditions for the first time. In typical experiments, the CuO@SiO₂ catalysts showed excellent AsH₃ removal activity and stability under low-temperature and low-oxygen conditions. The duration of the AsH₃ conversion rate above 90 % for the CuO@SiO₂ catalysts was 39 h, which was markedly higher than that of other catalysts previously reported in the literature. The considerable catalytic activity and stability were attributed to the protection and confinement effects of the SiO₂ shell, which resulted in highly dispersed CuO nanoparticles. Meanwhile, the strong interaction between the CuO core and SiO₂ shell further facilitated the formation of active species such as coordinatively unsaturated Cu²⁺ and chemisorbed oxygen. The accumulation of oxidation products (As₂O₃ and As₂O₅) on the interface between the CuO core and SiO₂ shell and the pore channels of the SiO₂ shell is the main cause of catalysts deactivation. Furthermore, through combined density functional theory (DFT) calculations and characterization methods, a reaction pathway including gradual dehydrogenation (AsH₃*→AsH₂*→AsH*→As*) and gradual oxidation (2As*→As*+AsO*→2AsO*→As₂O₃) for the catalytic oxidation of AsH₃ on CuO (111) surface was constructed to clarify the detailed reaction mechanism. The CuO@SiO₂ core-shell catalysts applied in this study could provide a powerful method for developing AsH₃ catalysts from multiple know AsH₃ removal systems.

Simultaneous catalytic oxidation of Hg0 and AsH3 over Fe-Ce co-doped TiO2 catalyst under low temperature and reducing atmosphere

The Fe-Ce bimetal oxide-doped titanium dioxide composite was synthesized by the sol-gel method and the performance of the catalyst was investigated for the removal of Hg⁰ and AsH₃ from yellow phosphorus flue gas under different conditions. Brunauer-Emmett-Teller (BET) analysis, high-resolution transmission electron microscopy (HR-TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) were used to characterize the crystal structure and morphology of the structure, and the mechanisms for removing Hg⁰ and AsH₃ from flue gas by catalytic oxidation were deduced. The results showed that the optimal calcination temperature of the Fe₅Ce₅Ti catalyst was 500 °C, and the optimal pH of the sol was 6. Under these conditions, the penetration adsorption capacity of the Fe₅Ce₅Ti catalyst for the removal of AsH₃ and Hg⁰ was 385.5 mg g^-1 and 2.178 mg g^-1, respectively. According to characterization analysis, Fe and Ce are the main active components in the removal of Hg⁰ and AsH₃, and the mixed oxides of Fe and Ce have a synergistic effect on the surface of the mixed oxide-doped catalyst, which can improve the dispersion of the active component on the surface of the catalyst, and then improve the removal efficiency of Hg⁰ and AsH₃.

Investigation of the Role of Copper Species-Modified Active Carbon by Low-Temperature Roasting on the Improvement of Arsine Adsorption

Traditional adsorbents undershot the expectations for arsine (AsH₃) removal under low-temperature operation conditions in the industry. In this study, the copper (Cu) precursor was used to modify activated carbon and yield novel adsorbents by low-temperature roasting for high-efficiency removal of AsH₃. The best conditions were determined as impregnation with 2 mol/L Cu(NO₃)₂ adsorbent and roasting at 180 °C. At a reaction temperature of 40 °C and an oxygen content of 1%, the AsH₃ removal efficiency reached over 90% and lasted for 40 h and the best capacity of 369.6 mg/g was obtained with the Cu/Ac adsorbent. The characterization results showed the decomposition of Cu(NO₃)₂ during the low-temperature roasting process to form surface functional groups. The formation of the important intermediate Cu₂(NO₃)(OH)₃ in the decomposition of Cu(NO₃)₂ into CuO plays a role in the good regeneration performance of the Cu/Ac adsorbent using water washing and the gas regeneration method. The results of in situ diffuse reflectance infrared Fourier transform spectroscopy combined with X-ray photoelectron spectroscopy demonstrated that the interaction of trace oxygen with Lewis (L) acid sites increased chemisorbed oxygen by 17.34%, significantly promoting the spontaneity of AsH₃ oxidation reaction. These results provide a friendly economic method with industrial processes practical for AsH₃ removal.

Simultaneous catalytic oxidation of elemental mercury and arsine over CeO2(111) surface: a density functional theory study

Ceria (CeO₂)-based materials are potential catalysts for the removal of the Hg⁰ and AsH₃ present in reducing atmospheres. However, theoretical studies investigating the Hg⁰ and AsH₃ removal capacity of ceria remain limited. In this study, the adsorption behavior and mechanistic pathways for the catalytic oxidation of Hg⁰ and AsH₃ on the CeO₂(111) surface, including the calculation of optimized adsorption configurations and energies, were investigated using density functional theory calculations. The results suggest that Hg⁰ and AsH₃ are favorably adsorbed on the CeO₂(111) surface, whereas CO is not, which is crucial for selective removal when CO is a desirable gas component. Furthermore, AsH₃ is adsorbed more favorably than Hg⁰. In addition, the calculations revealed that the Hg atom is initially adsorbed on the surface and then oxidized by lattice oxygen to form HgO. Concerning AsH₃ decomposition, the stepwise dehydrogenation of AsH₃ followed by bonding with lattice O atoms to form the As-O bond seems the most plausible. Finally, the adsorbed As-O bond is further forms elemental As and As₂O₃. Therefore, CeO₂ can adsorb and remove Hg⁰ and AsH₃, making it a promising catalyst for the simultaneous catalytic oxidation of Hg⁰ and AsH₃ in strongly reducing off-gas.