Iron and copper nanoparticles inside and outside carbon nanotubes: Nanoconfinement, migration, interaction and catalytic performance in Fischer-Tropsch synthesis

Abstract

Carbon materials have attracted increasing attention as supports for metal catalysts. Ironcontaining carbon nanotubes often promoted with copper have found application in Fischer-Tropsch synthesis, which provides an alternative way for conversion of renewable feedstocks to chemicals and fuels. In carbon nanotubes, the active phase can be nanoconfined inside the channels or localized on the outer surface. In most of previous work, the distribution of metal nanoparticles inside or outside carbon nanotubes is considered to be immobile during the catalyst activation or catalytic reaction.In this paper, we uncovered remarkable mobility of both iron and copper species in the bimetallic catalysts between inner carbon nanotube channels and outer surface, which occurs in carbon monoxide and syngas, while almost no migration of iron species proceeds in the monometallic catalysts. This mobility is enhanced by noticeable fragility and defects in carbon nanotubes, which appear on their impregnation with the acid solutions of metal precursors and precursor decomposition. Remarkable mobility of iron and copper species in bimetallic catalysts affects the genesis of iron active sites, and enhances interaction of iron with the promoter. In the bimetallic iron-copper catalysts, the major increase in the activity was attributed to higher reaction turnover frequency over iron surface sites located in a close proximity with copper.

Efficient Promoters and Reaction Paths in the CO2 Hydrogenation to Light Olefins over Zirconia-Supported Iron Catalysts

“…Finally, the H 2 -TPR profile of FeKCu/ZrO 2 displays two reduction peaks at ∼250 and 298 °C, which shift to lower temperatures as compared to the reference Fe/ZrO 2 sample, in agreement with the literature . The intensity of the peak at 250 °C can also contribute from the reduction of copper . Indeed, the presence of copper in the catalyst may facilitate iron oxide reduction.…”

“…75 The intensity of the peak at 250 °C can also contribute from the reduction of copper. 80 Indeed, the presence of copper in the catalyst may facilitate iron oxide reduction. Remarkably, the addition of promoters results in a higher amount of consumed hydrogen (Table 1).…”

Advances in Selectivity Control for Fischer–Tropsch Synthesis to Fuels and Chemicals with High Carbon Efficiency

“…A newly emerging mobile metal (also denoted as liquid metal) promoter such as Bi, Pb, Sn, and Sb has gained growing attention due to its significant effect on catalytic activity and stability. ,− The mobile metal with a relatively lower melting point can migrate over the Co/Fe surface with the formation of larger spherical metal droplets encapsulating the FT metal during the reaction process. It is proposed that the metallic Bi, in close contact with FT metal, can timely scavenge the O atoms dissociated from CO, and the as-obtained oxidized Bi species are easily again reduced to the metallic state during the syngas conversion process.…”

Advancing Green Nanotechnology: Harnessing the Bio-reducing Properties of Musa paradisiaca Peel Extract for Sustainable Synthesis of Iron Oxide Nanoparticles

“…The presence of clustered nanoparticles suggests the existence of interparticle interactions. Van der Waals forces, magnetic interactions, or electrostatic forces may be responsible for holding the nanoparticles together within the clusters [54]. Understanding these interactions is crucial for controlling aggregation behavior and achieving desired dispersibility.…”