First-Principles Based Heterogeneous Catalyst Design for Energy Conversion and Plastics Upcycling Processes

Author

Kyung-Eun You

Date of Award

Spring 2022

Document Type

Open Access Dissertation

Department

Chemical Engineering

First Advisor

Andreas Heyden

Abstract

Replacing scarce and expensive Pt-group metals (Pt, Pd, Ir, Rh, and Ru) commonly used in heterogeneous catalysis with earth-abundant and inexpensive materials is an important challenge to achieve sustainability

The main focus of the first project is to develop highly selective non-precious metal catalysts for the hydrodeoxygenation (HDO) of biomass-derived polyols and we chose to examine the HDO of glycerol and its deoxygenated reaction products (1,2- and 1,3- propanediol) over Cu modified Mo₂C (Cu/Mo₂C) catalysts. In this study, we combined experimental and density functional theory (DFT) results to reveal that the Cu modifier can significantly reduce the oxophilicity of the Mo2C surface and change the product distribution. The Mo₂C support effect was examined by investigating the glycerol HDO reaction on a Cu/Mo2C surface and a Cu(111) surface using DFT and microkinetic modeling techniques. It is shown that the Cu/Mo₂C catalyst is more active for glycerol conversion with high selectivity to HDO products, and the stability of the surface was preserved by excess hydrogen.

Next, we examined the HDO reaction mechanism of 1,2- and 1,3-propanediols over a Cu/Mo₂C catalyst. The purpose of this study is to understand the effect of hydroxyl group position on the HDO activity of these diols and also to determine if these smaller diols can act as model molecules for glycerol and complex polyols. Here, a microkinetic model was developed under two experimental reaction environments, i.e., the UHV conditions used during temperature programmed desorption (TPD), and high pressure conditions typical for reactor scale experiments. The multi-scale simulations bridge the pressure gap between surface science and reactor studies and thus, provide a mechanistic understanding of the HDO of polyols.

In the final section, the studies of selective deconstruction of polyethylene by ultrasmall catalytic ZrO₂ nanoparticles localized in m-SiO₂ will be elaborated which was performed by a multidisciplinary research collaboration. This study aims at identifying suitable catalysts using non-precious elements and approaches for selective deconstruction of polyethylene into valuable products which is otherwise known as plastic waste upcycling. Using a first-principles approach, we identified meaningful active site models and reaction mechanisms and correlated model results to experimental observations to suggest procedures for further optimizing ZrO₂-based catalysts for polyethylene upcycling.

Rights

© 2022, Kyung-Eun You

Recommended Citation

You, K.(2022). First-Principles Based Heterogeneous Catalyst Design for Energy Conversion and Plastics Upcycling Processes. (Doctoral dissertation). Retrieved from https://scholarcommons.sc.edu/etd/6556