Cobalt–Nickel Nanoparticles Supported on Reducible\nOxides as Fischer–Tropsch Catalysts

Abstract

Efficient and more\nsustainable production of transportation fuels\nis key to fulfill the ever-increasing global demand. In order to achieve\nthis, progress in the development of highly active and selective catalysts\nis fundamental. The combination of bimetallic nanoparticles and reactive\nsupport materials offers unique and complex interactions that can\nbe exploited for improved catalyst performance. Here, we report on\ncobalt–nickel nanoparticles on reducible metal oxides as support\nmaterial for enhanced performance in the Fischer–Tropsch synthesis.\nFor this, different cobalt to nickel ratios (Ni/(Ni + Co): 0.0, 0.25,\n0.50, 0.75, or 1.0 atom/atom) supported on reducible (TiO₂ and Nb₂O₅) or nonreducible (α-Al₂O₃) oxides were studied. At 1 bar, Co–Ni\nnanoparticles supported on TiO₂ and Nb₂O₅ showed stable catalytic performance, high activities and\nremarkably high selectivities for long-chain hydrocarbons (C₅₊, ∼80 wt %). In contrast, catalysts supported on α-Al₂O₃ independently of the metal composition showed\nlower activities, high methane production, and considerable deactivation\nthroughout the experiment. At 20 bar, the combination of cobalt and\nnickel supported on reducible oxides allowed for 25–50% cobalt\nsubstitution by nickel with increased Fischer–Tropsch activity\nand without sacrificing much C₅₊ selectivity. STEM-EDX\nand IR of adsorbed CO pointed to a cobalt enrichment of the nanoparticle’s\nsurface and a weaker adsorption of CO in Co–Ni supported on\nTiO₂ and Nb₂O₅ and not on α-Al₂O₃, modifying the rate-determining step and the\ncatalytic performance. Overall, we show the strong effect and potential\nof reducible metal oxides as support materials for bimetallic nanoparticles\nfor enhanced catalytic performance.