Catalytic partial oxidation of methane to synthesis gas over a ruthenium catalyst: the role of the oxidation state

Ligand effect on Ru-centered species toward methane activation

Ligands have been known to profoundly affect the chemical transformations of methane, yet significant challenges remain in shedding light on the underlying mechanisms. Here, we demonstrate that the conversion of methane can be regulated by Ru centered cations with a series of ligands (C, CH, CNH, CHCNH). Gas-phase experiments complemented by theoretical dynamic analysis were performed to explore the essences and principles governing the ligand effect. In contrast to the inert Ru+, [RuC]+, and [RuCNH]+ toward CH4, the dehydrogenation dominates the reaction of ligand-regulated systems [RuCH]+/CH4 and [RuCHCNH]+/CH4. In active cases, CH acts as active sites, and regulates the activation of CH4 assisted by the "seemingly inert" CNH ligand.

Toxicity profiling of metallosurfactant based ruthenium and ruthenium oxide nanoparticles towards the eukaryotic model organism Saccharomyces cerevisiae

In the present study, a facile method was used to synthesize the ruthenium and ruthenium oxide (RuO₂) nanoparticles (NPs) derived from three different metallosurfactants. Firstly, three metallosurfactants were fabricated i.e. RuCTAC (Bishexadecyltrimethylammonium ruthenium tetrachloride), RuDDA (Bisdodecylamine ruthenium dichloride), and RuHEXA (Bishexadecylamine ruthenium dichloride) and characterized by CHN, FTIR, and ¹HNMR. These metallosurfactants were further utilized to fabricate the mixed type of NPs (Ru and RuO₂ NPs) using the biocompatible microemulsion technique and NPs were then characterized. Subsequently, the nanotoxicity of mixed NPs (Ru & RuO₂) was studied towards Saccharomyces cerevisiae. The detailed study of nanotoxicity against the S. cerevisiae cells was done by employing optical microscopy, FESEM, anti-yeast activity assay, circular dichroism, and gel electrophoresis techniques. FESEM and optical microscopy analyses indicated that RuCTAC nanosuspension (Ns) has the most toxic effect on the S. cerevisiae cells. FESEM analysis confirmed the harmful impact of Ru and RuO₂ NPs on the S. cerevisiae cells. From the FESEM analysis, complete alteration in the morphology, cell membrane breakage, and formation of the holes on the cell wall of S. cerevisiae was affirmed in presence of all three types of Ns i.e. RuCTAC, RuDDA, and RuHEXA Ns. Genotoxicity of the NPs was confirmed by circular dichroism and gel electrophoresis and it was found that RuCTAC and RuHEXA Ns have the most damaging influence on the yeast genomic DNA.

Formation of microns long thin wire networks with a controlled spatial distribution of elements

By controlling the spatial distribution of elements using a simple self-assembly process, the catalytic performance can be enhanced.

In Situ Encapsulated Pt Nanoparticles Dispersed in Low Temperature Oxygen for Partial Oxidation of Methane to Syngas

Highly dispersed ultra-small Pt nanoparticles limited in nanosized silicalite-1 zeolite were prepared by in situ encapsulation strategy using H2PtCl6·6H2O as a precursor and tetrapropylammonium hydroxide as a template. The prepared Pt@S-1 catalyst was characterized by X-ray diffraction (XRD), inductively coupled plasma (ICP), transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM), N2 adsorption-desorption, CO adsorption, and TGA techniques and exhibited unmatched catalytic activity and sintering resistance in the partial oxidation of methane to syngas. Strikingly, Pt@S-1 catalyst with further reduced size and increased dispersibility of Pt nanoparticles showed enhanced catalytic activity after low-temperature oxygen calcination. However, for Pt/S-1 catalyst, low-temperature oxygen calcination did not improve its catalytic activity.

The Role of Active Sites Location in Partial Oxidation of Methane to Syngas for MCM-41 Supported Ni Nanoparticles

The supporting modes of active metal over mesoporous materials play an important role in catalytic performance. The location of Ni nanoparticles inside or outside the mesoporous channel of MCM-41 has a significant influence on the reactivity in partial oxidation of methane to syngas reaction. The characterization data using different techniques (Transmission Electron Microscope (TEM), X-Ray Diffraction (XRD), N2 adsorption-desorption, H2 Temperature-Programmed Reduction (H2-TPR), and Inductively Coupled Plasma (ICP)) indicated that nickel was located outside the mesoporous channels for the impregnation method (Ni/MCM-41), while nickel was encapsulated within MCM-41 via the one-step hydrothermal crystallization method (Ni-MCM-41). The nickel atoms were mainly dispersed predominantly inside the skeleton of zeolite. When the load amount of Ni increased, both of Ni species inside the skeleton or pore channel of zeolite increased, and the ordered structure of MCM-41 was destroyed gradually. Contributed by the strong interaction with MCM-41, the Ni particles of Ni-MCM-41 were highly dispersed with smaller particle size compared with supported Ni/MCM-41 catalyst. The Ni-MCM-41 displayed higher catalytic performance than Ni/MCM-41, especially 10% Ni-MCM-41 due to high dispersity of Ni. The confinement effect of MCM-41 zeolite also afforded high resistance of sintering and coking for 10% Ni-MCM-41 catalyst. Especially, 10% Ni-MCM-41 catalyst showed outstanding catalytic stability.

Thermal Activation of CH4 and H2 as Mediated by the Ruthenium Oxide Cluster Ions [RuOx ]+ (x=1-3): On the Influence of Oxidation States

Thermal gas-phase reactions of the ruthenium-oxide clusters [RuO_x ]⁺ (x=1-3) with methane and dihydrogen have been explored by using FT-ICR mass spectrometry complemented by high-level quantum chemical calculations. For methane activation, as compared to the previously studied [RuO]⁺ /CH₄ couple, the higher oxidized Ru systems give rise to completely different product distributions. [RuO₂ ]⁺ brings about the generations of [Ru,O,C,H₂ ]⁺ /H₂ O, [Ru,O,C]⁺ /H₂ /H₂ O, and [Ru,O,H₂ ]⁺ /CH₂ O, whereas [RuO₃ ]⁺ exhibits a higher selectivity and efficiency in producing formaldehyde and syngas (CO+H₂ ). Regarding the reactions with H₂ , as compared to CH₄ , both [RuO]⁺ and [RuO₂ ]⁺ react similarly inefficiently with oxygen-atom transfer being the main reaction channel; in contrast, [RuO₃ ]⁺ is inert toward dihydrogen. Theoretical analysis reveals that the reduction of the metal center drives the overall oxidation of methane, whereas the back-bonding orbital interactions between the cluster ions and dihydrogen control the H-H bond activation. Furthermore, the reactivity patterns of [RuO_x ]⁺ (x=1-3) with CH₄ and H₂ have been compared with the previously reported results of Group 8 analogues [OsO_x ]⁺ /CH₄ /H₂ (x=1-3) and the [FeO]⁺ /H₂ system. The electronic origins for their distinctly different reaction behaviors have been addressed.

Effect of cobalt addition on the structure and properties of Ni–MCM-41 for the partial oxidation of methane to syngas

A one-step hydrothermal crystallization method was used to synthesize Co–Ni–MCM-41 catalysts for the partial oxidation of methane to syngas reaction. Co was added as an assistant in the synthesis process. The formation of a Ni–Co alloy decreased the damage of Ni ions to the framework of MCM-41. The Ni–Co alloy introduced more Ni into the channel exposing more active sites. The properties of the synthesized catalysts were characterized by XRD, N₂ adsorption–desorption, TEM, ICP, FT-IR, H₂-TPR, XPS and TGA techniques. Co–Ni–MCM-41 catalysts showed superior catalytic performance and sintering resistance than Ni–MCM-41 catalyst without Co. The Ni–Co alloy inhibited the formation of the NiO, thus reducing the sintering of the catalyst. The result was attributed to higher metal dispersion and more regular pore structure of the Co–Ni–MCM-41 catalysts. When the Co content was 1%, a conversion of 88% and selectivity of 87% was achieved.

The Ni–Co alloy confined within MCM-41 improved dispersibility and the stability of Ni.

Insights into the effect of the catalytic functions on selective production of ethylene glycol from lignocellulosic biomass over carbon supported ruthenium and tungsten catalysts

The one-pot conversion of cellulose to ethylene glycol (EG) was investigated using a combination of a ruthenium catalyst supported on carbon nanotubes modified with nitric acid (Ru/CNT₁) and a tungsten catalyst supported on commercial non-treated carbon nanotubes (W/CNT₀). This physical mixture allowed to obtain an EG yield of 41% in just 5 h at 205 °C and 50 bar of H₂, which overcame the result obtained using a Ru-W bimetallic catalyst supported on commercial carbon nanotubes (35%) under the same conditions. Tissue paper, a potential waste cellulosic material, and eucalyptus were also tested under the same conditions and EG yields of 34 and 36%, respectively, were attained over the aforementioned catalytic physical mixture. To the best of our knowledge, this work presents for the first time the catalytic conversion of lignocellulosic materials, namely tissue paper and eucalyptus, directly into EG by an environmentally friendly process.