Cobalt–Nickel Nanoparticles Supported on Reducible Oxides as Fischer–Tropsch Catalysts

Abstract

Efficient and more sustainable production of transportation fuels is key to fulfill the ever-increasing global demand. In order to achieve this, progress in the development of highly active and selective catalysts is fundamental. The combination of bimetallic nanoparticles and reactive support materials offers unique and complex interactions that can be exploited for improved catalyst performance. Here, we report on cobalt−nickel nanoparticles on reducible metal oxides as support material for enhanced performance in the Fischer−Tropsch synthesis. For this, different cobalt to nickel ratios (Ni/(Ni + Co): 0.0, 0.25, 0.50, 0.75, or 1.0 atom/atom) supported on reducible (TiO 2 and Nb 2 O 5 ) or nonreducible (α-Al 2 O 3 ) oxides were studied. At 1 bar, Co−Ni nanoparticles supported on TiO 2 and Nb 2 O 5 showed stable catalytic performance, high activities and remarkably high selectivities for long-chain hydrocarbons (C 5+ , ∼80 wt %). In contrast, catalysts supported on α-Al 2 O 3 independently of the metal composition showed lower activities, high methane production, and considerable deactivation throughout the experiment. At 20 bar, the combination of cobalt and nickel supported on reducible oxides allowed for 25−50% cobalt substitution by nickel with increased Fischer−Tropsch activity and without sacrificing much C 5+ selectivity. STEM-EDX and IR of adsorbed CO pointed to a cobalt enrichment of the nanoparticle's surface and a weaker adsorption of CO in Co−Ni supported on TiO 2 and Nb 2 O 5 and not on α-Al 2 O 3 , modifying the rate-determining step and the catalytic performance. Overall, we show the strong effect and potential of reducible metal oxides as support materials for bimetallic nanoparticles for enhanced catalytic performance.

Tuning the Catalytic Performance of Cobalt Nanoparticles by Tungsten Doping for Efficient and Selective Hydrogenation of Quinolines under Mild Conditions

“…These reduction events are associated with the sequential reduction of Co 3 O 4 (a phase also detected by Raman spectroscopy, as shown in Figure S6 ) to CoO, and to metallic Co, respectively. 106 Interestingly, the reduction profile of the catalyst containing tungsten doping species (CoW@C-0.05) is slightly shifted to lower temperatures, thus indicating that their presence influences the cobalt oxide reduction. Moreover, both catalysts display a broad H 2 -uptake peak centered at temperatures around 550–625 °C, which is typically associated with the gasification of carbon and the reduction of surface oxygenated groups present on the carbon surface.…”

Boosting the performance of Ni/Al2O3 for the reverse water gas shift reaction through formation of CuNi nanoalloys

“…The reducibility of supported metal catalysts strongly depends on the particle size, oxidation state, metal-support and metalmetal interaction [62][63][64][65] . Figure 2 (Ni 2+ in an octahedral geometry, defined as Ni 2+ ions that are not completely integrated as a spinel-type structure but in strong interaction with the support).…”

Supported Metal Oxide Catalysts for CO2 Fischer–Tropsch Conversion to Liquid Fuels─A Review

“…This acidic property is known to increase turnover frequency (TOF) and C 5+ selectivity as a result of intrinsic surface-specific catalytic activity. 80 The addition of potassium as a promoter enhances the Fe dispersion of TiO 2 , increasing accessibility to the metal sites. 77 As demonstrated by Co supported on a TiO 2 catalyst, the substantial interaction increased Co dispersion, relating to a highly active catalyst, especially for the CO FTS reaction.…”

“…There is speculation that, upon thermal application, titania sub-oxides partially cover active catalyst particles, reducing the active metallic sites. 80 TiO 2 has also shown incredible success in the FT photocatalytic process. The structural defects inside and on the surface of titania particles are enhanced with photon-excited electrons, capable of high surface activity.…”

“…Owing to the hydrogen-donating ability of TiO 2 , the Cu/TiO 2 catalyst support under a pressurized system increased hydrogenation activity compared to Cu/SiO 2 and Cu/Al 2 O 3 . , The interaction with a TiO 2 reducible oxide support generates mild Lewis acid sub-oxides with strong SMSI. This acidic property is known to increase turnover frequency (TOF) and C 5+ selectivity as a result of intrinsic surface-specific catalytic activity . The addition of potassium as a promoter enhances the Fe dispersion of TiO 2 , increasing accessibility to the metal sites …”