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Different carbon nanomaterials are considered as promising supports for Fischer-Tropsch synthesis (FTS) catalysts of syngas transformation into hydrocarbons. At the same time, consolidation of carbon nanoparticles into a dense bulk material is one of the most important challenges faced by the catalytic industry. In this work consolidated Co and Fe catalysts supported on graphene nanoflakes (GNFs) were for the first time synthesized by spark plasma sintering (SPS). The synthesized catalysts contained reduced carbon-encapsulated metal nanoparticles embedded into the GNF framework, which ensured their activity in FTS without pre-activation. SPS significantly increased both the activity (from 77 to 91 µmolCO×gCo−1 ×s−1) and TOF (from 0.024 to 0.073 s−1) of the Co/GNF catalyst compared to the unsintered sample. In contrast, the activity of the Fe catalysts decreased after SPS, but their C5+ selectivity and olefins to paraffins ratio increased. These enhancements were attributed to the unique core-shell structure of the nanoparticles, highly active surface cobalt atoms, and close contact between carbon support and iron particles. SPS was proved to be a powerful approach to activate carbon-supported FTS catalysts, increase their density and modify their catalytic performance.

The tribological and rheological characteristics of three industrially produced greases and a model lubricant (medical vaseline) doped with new carbon nanoflakes additives (few layer graphite nanof...

The effect of synthesis conditions and incorporation of heteroatoms on the structure and morphology of few-layer graphene nanoflakes is investigated using Raman spectroscopy, X-ray photoelectron spectroscopy, and electron microscopy. It is found that doping with nitrogen forms defects inside graphene layers, while incorporation of silicon in contrast results in their bending and the formation of interlayer defects. Increasing the synthesis temperature reduces the number of defects in the material via graphitization and increase in the number of layers.

Nitrogen-doped carbon nanomaterials show unique properties in catalysis both as an active component and as a support. The oxidized and N-doped graphene nanoflakes (GNFs) of low domain size (10–30 nm) have been studied in present work as supports for cobalt-based Fischer-Tropsch catalysts. Three supports with different types of dominating nitrogen species were synthesized and the effect of both the nature and localization of nitrogen species in the support on the structure and performance of 10 wt.% Co catalysts was investigated. Varying the synthesis technique and post-synthesis treatment, the cobalt particle size and hence the activity of catalyst can be tuned. The catalysts supported on oxidized pristine and N-doped GNFs were found to be the most active. Transformations of N-groups during catalyst preparation and reduction were observed. In the case of edge localization of N-groups the cross-linking of support particles was detected that led to the diffusion hindering and low CO conversion over corresponding catalyst.

Because of its contribution to greenhouse effect, carbon dioxide conversion to valuable chemicals is one of the most challenging issues facing the modern world. A new type of iron catalysts of CO2 hydrogenation into hydrocarbons was synthesized by spark plasma sintering of carbon nanotubes decorated with iron oxide nanoparticles. This treatment produced carbon-encapsulated iron nanocrystals embedded in a dense framework of CNTs. The sintered catalysts were tested without pre-reduction in CO2 hydrogenation under supercritical conditions (350 °C, 8.5 MPa) and showed high specific activities of 5.4–12.2 molCO2gFe−1s−1 and promising C2+ selectivities of 40–50 mol.% at rather low H2:CO2 ratios of 1 and 2. The high efficiency of the catalysts was attributed to the stabilization of metal nanoparticles by carbon shells and increased density of CNT support, which led to higher degree of metal – support interaction and intensified carbidization and CO activation.

Doping of graphene-based nanomaterials is one of the most effective approaches for the modification of their physicochemical properties [...]