Catalytic decomposition of toxic chemicals over metal-promoted carbon nanotubes

Highly active Ni/Fe3O4/TiO2 nanocatalysts with tunable interfacial interactions for PH3 decomposition

The mixed-metal oxide Ni/Fe₃O₄/TiO₂ with two metal-oxide interfaces to catalyze sequential chemical reactions was first applied in the decomposition of phosphine gas for yellow phosphorus (P₄) production. The catalyst was prepared with tunable Ni-Fe₃O₄ and Ni-TiO₂ interactions via annealing and subsequent reduction. Ni/Fe₃O₄/TiO₂ exhibited significantly effective activity and good stability in the PH₃ decomposition, which were achieved by modulating the metal-support interaction. The characterizations by scanning electron microscopy(SEM), X-ray diffraction analysis(XRD), BET surface area measurement and X-ray photoelectron spectroscopy(XPS) were carried out. The enhancements of the Ni-Fe₃O₄ and Ni-TiO₂ dual interactions by annealing and reduction were verified and the mechanism of PH₃ decomposition over the modulated Ni/Fe₃O₄/TiO₂ catalyst was investigated. NiOOH as an active catalytic intermediate species is produced by the synergistic catalytical dual interfaces. The catalytic reaction pathways of PH₃ decomposition by the dual interfaces were firstly revealed. The results provide underlying insights in the way to promote the catalytic performance for synergistic catalysis in PH₃ decomposition.

Support Effect on the Performance of Ni2P Catalysts in the Hydrodeoxygenation of Methyl Palmitate

The effect of support nature, SiO2 and γ-Al2O3, on physicochemical and catalytic properties of nickel phosphide catalysts in methyl palmitate hydrodeoxygenation (HDO) has been considered. Firstly, alumina-supported nickel phosphide catalysts prepared by temperature-programmed reduction method starting from different precursors (phosphate–Ni(NO3)2 and (NH4)2HPO4 or phosphite–Ni(OH)2 and H3PO3) were compared using elemental analysis, N2 physisorption, H2-TPR, XRD, TEM, NH3-TPD, 27Al and 31P MAS NMR techniques and catalytic experiments. The mixture of nickel phosphide phases was produced from phosphate precursor on alumina while using of phosphite precursor provides Ni2P formation with the higher activity in methyl palmitate HDO. Besides, the comparative study of the performances of Ni2P/SiO2 and Ni2P/Al2O3 catalysts demonstrates the apparent superiority of alumina-supported Ni2P in the methyl palmitate hydrodeoxygenation. Considering the tentative scheme of methyl palmitate transformation, we proposed that cooperation of Ni2P and acid sites on the surface of alumina provides the enhanced activity of alumina-supported Ni2P through the acceleration of acid-catalysed hydrolysis.

Reduction of Bromate by Cobalt-Impregnated Biochar Fabricated via Pyrolysis of Lignin Using CO2 as a Reaction Medium

In this study, pyrolysis of lignin impregnated with cobalt (Co) was conducted to fabricate a Co-biochar (i.e., Co/lignin biochar) for use as a catalyst for bromate (BrO₃^-) reduction. Carbon dioxide (CO₂) was employed as a reaction medium in the pyrolysis to induce desired effects associated with CO₂; (1) the enhanced thermal cracking of volatile organic compounds (VOCs) evolved from the thermal degradation of biomass, and (2) the direct reaction between CO₂ and VOCs, which resulted in the enhanced generation of syngas (i.e., H₂ and CO). This study placed main emphases on three parts: (1) the role of impregnated Co in pyrolysis of lignin in the presence of CO₂, (2) the characterization of Co/lignin biochar, and (3) evaluation of catalytic capability of Co-lignin biochar in BrO₃^- reduction. The findings from the pyrolysis experiments strongly evidenced that the desired CO₂ effects were strengthened due to catalytic effect of impregnated Co in lignin. For example, the enhanced generation of syngas from pyrolysis of Coimpregnated lignin in CO₂ was more significant than the case without Co impregnation. Moreover, pyrolysis of Coimpregnated lignin in CO₂ led to production of biochar of which surface area (599 m² g^-1) is nearly 100 times greater than the biochar produced in N₂ (6.6 m² g^-1). Co/lignin biochar produced in CO₂ also showed a great performance in catalyzing BrO₃^- reduction as compared to the biochar produced in N₂.

Effect of precursor on the catalytic properties of Ni2P/SiO2 in methyl palmitate hydrodeoxygenation

The effect of phosphorus precursor on the physicochemical and catalytic properties of silica-supported nickel phosphide catalysts in the hydrodeoxygenation (HDO) of aliphatic model compound methyl palmitate (C₁₅H₃₁COOCH₃) has been considered.

Catalytic decomposition of toxic chemicals over iron group metals supported on carbon nanotubes

This study explores catalytic decomposition of phosphine (PH3) using iron group metals (Co, Ni) and metal oxides (Fe2O3, Co(3)O4, NiO) supported on carbon nanotubes (CNTs). The catalysts are synthesized by means of a deposition-precipitation method. The morphology, structure, and composition of the catalysts are characterized using a number of analytical instrumentations, including high-resolution transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, BET surface area measurement, and inductively coupled plasma. The activity of the catalysts in the PH3 decomposition reaction is measured and correlated with their surface and structural properties. The characterization results show that phosphidation occurs on the catalyst surface, and the resulting metal phosphides act as an active phase in the PH3 decomposition reaction. Cobalt phosphide, CoP, is formed on Co/CNTs and Co(3)O4/CNTs, whereas iron phosphide, FeP, is formed on Fe2O3/CNTs. In contrast, phosphorus-rich phosphide NiP2 is formed on Ni/CNTs and NiO/CNTs. The initial activities of the catalysts are shown in the following sequence: Ni/CNTs > Co/CNTs > Co(3)O4/CNTs >NiO/CNTs > Fe2O3/CNTs, whereas activities of metal phosphides are shown in the following order: CoP > NiP2 > FeP. The catalytic activity of metal phosphides is attributed to their electronic properties. Cobalt phosphide formed on Co/CNTs and Co(3)O4/CNTs exhibits not only the highest activity, but also long-term stability in the PH3 decomposition reaction.

Halloysite-nanotubes supported FeNi alloy nanoparticles for catalytic decomposition of toxic phosphine gas into yellow phosphorus and hydrogen

The FeNi alloy nanoparticles (FeNi and BFeNi) supported on natural halloysite nanotubes (HNTs) were prepared for catalytic decomposition of toxic phosphine (PH₃) to yellow phosphorus and hydrogen. The Fourier transform infrared spectroscopy, X-ray diffraction, inductively coupled plasma, scanning electron microscope, and hydrogen temperature-programmed reduction tests were carried out to characterize the physicochemical properties of HNTs and the prepared nano-catalysts. Nearly 100% PH₃ was decomposed into yellow phosphorus and hydrogen at 420 °C with prepared FeNi/HNTs catalysts. Metallic Ni and Fe₃O₄ could be the catalytic active sites in FeNi/HNTs for PH₃ decomposition under the low temperature. The boron (B) additives decrease the catalytic activity of FeNi/HNTs for PH₃ decomposition due to the formation of the spinal NiFe₂O₄ and Fe₂B which replace the active Fe₃O₄ and metallic Ni in catalysts. The developed FeNi/HNTs are low-cost and effective catalysts for air-pollution control and recycle of the hazardous waste PH₃ gas in industry.