Unraveling the Role of Metal–Support Interactions on the Structure Sensitivity of Fischer–Tropsch Synthesis
Michel P. C. van Etten, Michelle E. De Laat, Emiel J. M. Hensen, Ivo A. W. Filot
Abstract
High Resolution Image Download MS PowerPoint Slide Structure sensitivity plays a pivotal role in heterogeneous catalysis and the Fischer–Tropsch reaction is one of the prime examples of such a structure-sensitive reaction. The activity and selectivity of this reaction depend on the size of the nanoparticle and this trend is observed for a whole range of support materials. To understand why metal–support interactions do not affect this trend, a ReaxFF force field is developed that effectively mimics the broad variety of support materials and captures the metal–support interaction strength into a single structural parameter. Particles of 1–9 nm embedded on support materials are sampled using simulated annealing molecular dynamics and the effect of the metal–support interaction on the active site distribution is studied. It is found that although the size-dependency profile of various active site topologies depends on the interaction strength of the nanoparticle with the support, step-edge sites with an FCC(110) motif remain insensitive to the type of support. Based on microkinetic simulations, it is established that these sites are predominantly responsible for the observed atom-based FTS activity rationalizing why Fischer–Tropsch synthesis is structure-sensitive but support-insensitive.