Nano-engineered materials for Fischer-Tropsch catalysis

Abstract

Pure and bimetallic nanoclusters containing Ru, Fe, Ni, Co, Pd, and Mn have been explored for Fischer-Tropsch activity. Using Density Functional Theory, nanoclusters of approximately 0.5, 0.8, and 1.5 nm in diameter respectively were found to have particular structural stability. Classical Molecular Dynamics simulations have been conducted to investigate the thermal stability of the nanoclusters of about 1.2 to 1.5 nm in diameter, as those are typically the smallest sizes that can be achieved experimentally. These cluster sizes showed thermal stability at the typical temperature of the FT process (200 – 250°C range). CO adsorption energies on several nanocatalysts were calculated for adsorption on all different possible sites. Using CO adsorption energy results in combination with CO dissociation energies, a smaller list of nanoclusters were identified as potentially effective catalysts for FT catalysis, and selected for further reactivity testing. Particularly, Fe4Co10 seems to be a promising candidate, as both CO adsorption and dissociation energies are favorable. The effectiveness of Fe4Co10 upon Fischer-Tropsch activity has been explored and results obtained at the LDA/VWN theory level are in good agreement with the literature, as the formation of adsorbed HCOH species on the catalyst surface was found to be one of the rate determining steps, as expected, with an energy barrier of 0.14 eV/atom.