Date of Award
Summer 2024
Document Type
Open Access Thesis
Department
Chemical Engineering
First Advisor
Andreas Heyden
Abstract
Computational investigations of heterogeneously catalyzed reactions using density functional theory (DFT) are often inaccurate, largely due to uncertainties in the choice of DFT functional (enthalpic uncertainty) and approximations for modeling adsorbate movement along the catalyst surface (entropic uncertainty). This work illustrates that both uncertainties are significant in the investigation of the ethane dehydrogenation (EDH) and hydrogenolysis on Pt catalysts by considering the complete deconstruction of ethane on Pt(111), Pt(211), and Pt(100) using microkinetic modeling (MKM). Hence, this work uses both non-calibrated and Bayesian calibrated MKMs to quantify and correct inaccuracies in macroscopic properties due to both uncertainties. A Bayesian approach to the correction of entropic errors was introduced using a ‘Modified Fermi Function (MFF)’ to calibrate in-between the two bounds of entropy represented by the harmonic oscillator (HO) and free translator (FT) approximations. Regardless of enthalpic and entropic uncertainties, all three surfaces are capable of ethane activation, however, Pt(211) was found to be the most active and is largely responsible for methane production. Next, Pt(111) is largely responsible for acetylene production, and Pt(100) has the highest ethylene selectivity but is most susceptible to coking. By comparing different calibrated models, the FT entropy approximation was found to better describe EDH at typical experimental conditions. Statistical evidence was found supporting Pt(111) as the active site for EDH, assuming one single site is responsible for the chemistry. On the three surfaces, competing second dehydrogenations to CH2CH2 and CH3CH were observed as well as isomerization of CH3CH back to CH2CH2 and deeper dehydrogenation of CH3CH. C-C cleavage was found to largely proceed via the CH3C intermediate on Pt(100) and Pt(111), while on Pt(211), via both CHC and CH3C.
Rights
© 2024, Mubarak Bello
Recommended Citation
Bello, M.(2024). Investigation of Ethane Dehydrogenation and Hydrogenolysis on Pt(111), Pt(211) and Pt(100): Bayesian Quantification and Correction of Dft-Based Enthalpic and Entropic Uncertainties. (Master's thesis). Retrieved from https://scholarcommons.sc.edu/etd/8042