Catalyst design and kinetic modeling often start from molecular-scale hypotheses about the reaction mechanism, the structure of the active sites and the nature of the rate and selectivity determining steps. Computational catalysis has become a crucial tool to analyze molecular-scale concepts and elucidate their electronic origin. In combination with characterization and experimental kinetic validation, insights gained from computational catalysis can be translated all the way to the industrial scale. This pas-de-deux between experiment and theory is becoming the new paradigm in catalyst design and kinetic modeling, both in academia and in industry.<br/><br/>In this presentation, I will illustrate how this approach can shed light on the main questions in Fischer Tropsch synthesis, such as, the shape and surface structure of the Cobalt catalyst under reaction conditions, [1] and the discrimination of potential reaction mechanisms [2]. In collaboration with operando TEM, we find that Co particles are surprisingly robust under a CO atmosphere. Different from Pt, CO adsorption does not stabilize more open Co facets. At the next scale, we find that Co terraces undergo a reconstruction to form triangular nano-islands. This reconstruction is driven by strong and synergistic CO and C adsorption. Again, this reconstruction is seen experimentally by reactive STM. Based on this structural model, and incorporating realistic CO coverages, we can describe the activity and selectivity of Co FTS using a dual-site microkinetic model. Interestingly, the model shows that both CO insertion and CH insertion are kinetically competitive.<br/><br/>

Computational catalysis for Fischer-Tropsch synthesis: Shape, structure, sctivity and selectivity of cobalt catalysts

2019 Fall National Meeting

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