Roles of Ruthenium–Support Interactions of Size-Controlled Ruthenium Nanoparticles for the Product Distribution of Fischer–Tropsch Synthesis

Ruthenium-Loaded Halloysite Nanotubes as Mesocatalysts for Fischer-Tropsch Synthesis

Halloysite aluminosilicate nanotubes loaded with ruthenium particles were used as reactors for Fischer–Tropsch synthesis. To load ruthenium inside clay, selective modification of the external surface with ethylenediaminetetraacetic acid, urea, or acetone azine was performed. Reduction of materials in a flow of hydrogen at 400 °C resulted in catalysts loaded with 2 wt.% of 3.5 nm Ru particles, densely packed inside the tubes. Catalysts were characterized by N₂-adsorption, temperature-programmed desorption of ammonia, transmission electron microscopy, X-ray fluorescence, and X-ray diffraction analysis. We concluded that the total acidity and specific morphology of reactors were the major factors influencing activity and selectivity toward CH₄, C_2–4, and C₅₊ hydrocarbons in the Fischer–Tropsch process. Use of ethylenediaminetetraacetic acid for ruthenium binding gave a methanation catalyst with ca. 50% selectivity to methane and C_2–4. Urea-modified halloysite resulted in the Ru-nanoreactors with high selectivity to valuable C₅₊ hydrocarbons containing few olefins and a high number of heavy fractions (α = 0.87). Modification with acetone azine gave the slightly higher CO conversion rate close to 19% and highest selectivity in C₅₊ products. Using a halloysite tube with a 10–20-nm lumen decreased the diffusion limitation and helped to produce high-molecular-weight hydrocarbons. The extremely small C₂–C₄ fraction obtained from the urea- and azine-modified sample was not reachable for non-templated Ru-nanoparticles. Dense packing of Ru nanoparticles increased the contact time of olefins and their reabsorption, producing higher amounts of C₅₊ hydrocarbons. Loading of Ru inside the nanoclay increased the particle stability and prevented their aggregation under reaction conditions.

Partial oxidation of methane to methanol by isolated Pt catalyst supported on a CeO2 nanoparticle

Catalytic transformation of methane (CH₄) into methanol in a single step is a challenging issue for the utilization of CH₄. We present a direct method for converting CH₄ into methanol with high selectivity over a Pt/CeO₂ catalyst which contains ionic Pt²⁺ species supported on a CeO₂ nanoparticle. The Pt/CeO₂ catalyst reproducibly yielded 6.27 mmol/g of Pt with a selectivity of over 95% at 300 °C when CH₄ and CO are used as reactants, while the catalyst had a lower activity when using only CH₄ without CO. Active lattice oxygen created on the Pt and CeO₂ interface provides selective reaction pathways for the conversion of CH₄ to methanol. Based on high-angle annular dark-field scanning transmission electron microscopy, x-ray photoelectron spectroscopy, x-ray absorption near-edge structure, extended x-ray absorption fine structure, catalytic studies, and density functional theory calculations, we propose a mechanistic pathway involving CH₄ activation at the active site in the vicinity of Pt²⁺ species.

Size and shape-controlled synthesis of Ru nanocrystals

Mastery over the size/shape of nanocrystals (NCs) enables control of their properties and enhancement of their usefulness for a given application. Within the past decades, the development of wet-chemistry methods leads to the blossom of research in noble metal nanomaterials with tunable sizes and shapes. We herein would prefer to devote this chapter to introduce the solution-based methods for size and shape-controlled synthesis of ruthenium (Ru) NCs, which can be summarized into five categories: (i) Synthesis of spherical Ru NCs; (ii) synthesis of one-dimensional (1D) Ru NCs, e.g. wires and rods; (iii) synthesis of two-dimensional (2D) Ru NCs, e.g. nanoplates; (iv) synthesis of Ru NCs with hollow interiors and (v) synthesis of Ru NCs with other morphologies, e.g. chains, dendrites and branches. We aim at highlighting the synthetic approaches and growth mechanisms of these types of Ru NCs. We also introduce the detailed characterization tools for analysis of Ru NCs with different sizes/shapes. With respect to the creation of great opportunities and tremendous challenges due to the accumulation in noble metal nanomaterials, we briefly make some perspectives for the future development of Ru NCs so as to provide the readers a systematic and coherent picture of this promising field. We hope this reviewing effort can provide for technical bases for effectively designing and producing Ru NCs with enhanced physical/chemical properties.

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Fe3O4 nanocubes assembled on RGO nanosheets: Ultrasound induced in-situ and eco-friendly synthesis, characterization and their excellent catalytic performance for the production of liquid fuel in Fischer-tropsch synthesis

In this study, Fe₃O₄ nanocubes (NCs) decorated on RGO nanosheets (NSs) structures were successfully synthesized through an innovative and environmentally-friendly rapid sonochemical method. More importantly, iron(II) sulfate heptahydrate and GO were employed as precursors and water as reaction medium, meanwhile, NaOH within the generated free radicals from the high intensity ultrasound were sufficient as reducing and base agent in our clean synthesis. Moreover, the hydrothermal method as a conventional approach was employed to synthesize the same catalysts for the comparison with the ultrasonocation technique. The as-synthesized Fe₃O₄ and RGO/Fe₃O₄ NSs catalysts were exposed to industrially relevant Fischer-tropsch synthesis (FTS) conditions at various reaction temperatures (250-290 °C), and they subjected to fully characterization before and after FTS reaction using XRD, TEM, HRTEM, EDS mapping, XPS, FTIR, BET, H₂-TPR, H₂-TPD and CO-TPD to understand the structure-performance relationships. Notably, the catalysts produced using the sonochemical method had a better CO conversion rate [Fe₃O₄ (80%), RGO/Fe₃O₄ (82%)] than the hydrothermally synthesized catalysts. However, compared to the naked-Fe₃O₄ catalysts, the sonochemically and hydrothermally synthesized RGO-supported Fe₃O₄ catalysts had higher long chain hydrocarbon (C5+) selectivity values (72% and 67%) and C₂-C₄ olefin/paraffin selectivity ratio (3.2 and 2) and low CH4 selectivity values (6% and 8.5%), respectively. This can be attributed to their high surface area, the degree of reducibility, and content of Hägg iron carbide (χ-Fe₅C₂) as the most active phase of the FTS reaction. Proposed reaction mechanisms for the sonochemical and hydrothermal reaction synthesis of Fe₃O₄ and RGO/Fe₃O₄ nanoparticles are discussed. In conclusion, our developed surfactantless-sonochemical method holds promise for the eco-friendly synthesis of highly efficient catalysts materials for FTS reaction.

The influence of catalyst factors for sustainable production of hydrocarbons via Fischer-Tropsch synthesis

Fischer-Tropsch synthesis (FTS) is a process which catalytically converts syngas (H

Effects of CO2 on the deactivation behaviors of Co/Al2O3 and Co/SiO2 in CO hydrogenation to hydrocarbons

Different deactivation behaviors of the prototype Co/γ-Al₂O₃ (CoAl) and Co/SiO₂ (CoSi) catalysts under an excess CO₂ environment were investigated in terms of the surface oxidation and aggregation of cobalt crystallites for the Fischer–Tropsch Synthesis (FTS) reaction.

Effect of the ordered meso–macroporous structure of Co/SiO2 on the enhanced activity of hydrogenation of CO to hydrocarbons

Ordered meso–macroporous silica (MMS) was applied for the cobalt-based FTS reaction, and the enhanced activity on the Co/MMS was mainly due to the larger macropore cavity by enhancing the mass transfer rate which can be easily regenerated by in situ feeding of liquid hydrocarbons.

Ruthenium nanoclusters dispersed on titania nanorods and nanoparticles as high-performance catalysts for aqueous-phase Fischer–Tropsch synthesis

The high AFTS activity and C₅₊ selectivity of the serial Ru/TiO₂ nanocatalysts were favoured by the increasing metallic Ru sites due to H₂ reduction pretreatment and weak metal–support interaction.

Synthesis of highly dispersed Pd nanoparticles supported on multi-walled carbon nanotubes and their excellent catalytic performance for oxidation of benzyl alcohol

A simple approach to synthesize highly dispersed Pd nanoparticles on CNTs without a capping agent is presented which exhibits high activity and selectivity for selective oxidation of benzyl alcohol.

Fischer–Tropsch synthesis on Co/AlSBA-15: effects of hydrophilicity of supports on cobalt dispersion and product distributions

The increased C₂–C₄selectivity on the Co/AlSBA-15 was mainly attributed to the formation of small cobalt particles with a stronger metal–support interaction on the outer surface acid sites of the AlSBA-15 due to a higher hydrophilicity of the Al-incorporated SBA-15.