Microkinetic modelling of site synergy in supported nanoparticle Fischer-Tropsch catalysts
Heterogeneous catalysts based on metal nanoparticles supported on oxides exhibit a rich variety of active sites. In cobalt-catalyzed Fischer-Tropsch synthesis (FTS), atoms located on flat terraces, low-coordinated step edges, and at the metal-support interface can all participate in the reaction network. These sites do not operate independently: species formed near the nanoparticle perimeter may diffuse to other regions, and the presence of the support can modify the chemistry of nearby metal atoms. Understanding this interplay is essential when designing catalysts for renewable FTS, where H2 is derived from renewable resources and CO/CO2 originate from point sources.
Microkinetic modelling provides a powerful framework to describe such complex catalytic systems by combining elementary reaction steps, site balances, and transport between different site types into a consistent kinetic description. In this project, you will construct and analyze a three-site microkinetic model that distinguishes terrace sites, step-edge sites, and interfacial sites at the metal-support perimeter. The central goal is to quantify the synergy between the interfacial perimeter and sites located further away on the nanoparticle, and to understand how this cooperation influences overall activity and selectivity in FTS.
Figure 1: Hypothetical metal nanoparticle illustrating the coexistence of terrace and step-edge sites, which differ in atomic coordination and therefore exhibit distinct chemical reactivity.
Project outline
- Review the elementary reaction network of cobalt-catalyzed FTS and identify key intermediates and rate-controlling steps.
- Define a three-site model (terrace, step-edge, interfacial) with separate site balances and reaction pathways where appropriate.
- Implement the reaction network in microkinetic modelling software and assign kinetic/thermodynamic parameters from literature or provided datasets.
- Include surface diffusion or inter-site transfer steps to couple chemistry at the perimeter with more distant sites.
- Simulate reaction rates and selectivities as a function of operating conditions (temperature, pressure, H2/CO/CO2 ratio) relevant to renewable FTS feeds.
- Analyze how changes in nanoparticle size (via varying the relative fraction of interfacial vs non-interfacial sites) influence performance and identify signatures of site synergy.
Expected outcome
A MSc-level report presenting a functioning three-site microkinetic model, sensitivity and degree-of-rate-control analyses, and a clear interpretation of how terrace, step-edge, and interfacial sites cooperate during FTS. The work should highlight how the metal-support perimeter contributes to overall catalytic behavior under renewable FTS conditions and discuss the assumptions and limitations of the kinetic description.