Activity and selectivity loss modelling on Co based Fischer-Tropsch catalysts

Cobalt based catalysts for the Fischer-Trospch (FT) synthesis reaction suffer from a selectivity and activity decay during long time runs. This seriously undermines the economic viability of the catalytic process. Moreover, since the characterization of FT catalysts is a challenge, particularly in reaction conditions, it remains extremely difficult to determine the reasons behind this performance degradation. Therefore, there are contradicting views about the origin of this phenomenon within the scientific community. Amongst them, we can quote the sintering of the active phase, the oxidation of Co particles and the formation of carbonaceous species.

According to our theoretical considerations and other works in the literature, the catalyst degradation should be a trade-off between all these effects. Hence, in this PhD we propose a multi-scale approach, combining state-of-the-art ab initio calculations and microkinetic modeling in order to assess all these different hypothesis on the deactivation and selectivity loss of Co based FT catalysts. Moreover, we expect to gather information from this research in order to optimize the catalytic process.

The work consists on using a microkinetic model developed by Pr. Tronconi’s research group at the Instituto Politechnico di Milano. This model allows the catalyst selectivity to be predicted in combination with ab initio calculations from the literature and in-house calculations. We propose to develop Brønsted-Evans-Polany relationships in order to predict the activation barriers of the different elementary reactions as a function of the carbon and oxygen surface coverages. This should allow us to establish a more precise link between the reaction conditions and some of the most common deactivation causes put forward in the literature.

Keywords:Fischer-Tropsch, ab-initio calculations, microkinetic modeling, catalysis

Candidates willing to apply to this position are requested to send a CV, a motivation letter (or email), a list of their examination marks and two reccomendation letters from relevant lecturers at University.