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

Regulating the dispersion of CuO over SiO2 surface for selective oxidation of isobutane to tert-butanol

Controlling the highly selective oxidation of CH bonds in alkanes was still a challenge in the oxidation process, especially in oxygen atmospheres. Herein, three CuO/SiO2 catalysts were designed and prepared by regulating the introduction of copper species to achieve the selective oxidation of tertiary C-H of isobutane (i-C4H10) to tert-butanol (TBA). Under the condition of 130 °C and 1.5 h, CuO/SiO2-DP catalyst could achieve 92.7 % O2 conversion and 85.1 % TBA selectivity, and the cycle stability could be maintained. The improvement of catalytic performance could be attributed to the efficient utilization of Cu atoms, which was related to the regulating the formation of copper phyllosilicate and the full utilization of Si-OH on the surface of SiO2 during the catalyst synthesis process. Copper phyllosilicate formed a rich Si-O-Cu unit, enhanced the metal oxide-support interaction, inhibited the growth of copper species, improved the anchoring and dispersion of CuO, and ultimately improved the accessibility of substrate molecules on active CuO (111). In addition, the adsorption configuration of i-C4H10 and O2 on CuO (111) was determined by in-situ FT-IR and DFT, and the existence form of O2 after charge transfer was discussed. The reaction mechanism of i-C4H10 oxidation to TBA was revealed, which provided theoretical guidance for the selective preparation of TBA from i-C4H10 over metal oxides.

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.