(406h) Automated Microscopic Reaction Path Analysis of Methane Dehydrogenation on Ptsn Catalysts

Authors: 
Szilvási, T., University of Wisconsin-Madison
Gerceker, D., Abbvie
Chen, B. W. J., University of Wisconsin-Madison
Mavrikakis, M., University of Wisconsin-Madison
Non-oxidative coupling of methane to ethylene and aromatics is a promising strategy for converting methane into more valuable chemicals; however, this process suffers from significant coke deposition and catalyst deactivation.1 In our recent study, we found experimental evidence that, especially when smaller metal nanoparticles (1−2nm) are present, PtSn catalysts supported on SiO­2 or H-ZSM-5 are more active and less prone to coke formation than pure Pt catalysts.2 This is counter-intuitive as one would expect that smaller nanoparticles are more prone to coke formation due to stronger binding of intermediates, including carbon (coke).

In this work, we developed an automated method to probe all relevant adsorption sites, diffusion paths, and reaction barriers for methane dehydrogenation to carbon on the surfaces of a variety of PtSn nanocatalysts. Combined with microkinetic modeling, we reveal the catalytic activity of different nanoparticles and show that there are PtSn nanoclusters of special size and shape that destabilize the binding of carbon, and are thus less prone to coke formation compared to Pt(111). These results could explain previous experimental outcomes and may help guiding the development of strategies for improved catalysts.

(1) Xu, Y.; Lin, L. Appl. Catal., A 1999, 188, 53−67.

(2) Gerceker, D.; Motagamwala, A. H.; Rivera-Dones, K. R.; Miller, J. B.; Huber, G. W.; Mavrikakis, M.; Dumesic, J. A. ACS Catal. 2017, 7 (3), 2088–2100.