MULTISCALE MODELING OF CONFINEMENT AND DYNAMICS IN HETEROGENEOUS, MULTIPHASE CATALYTIC SYSTEMS
| Author(s) | Chen, Tso-Hsuan | |
| Date Accessioned | 2024-01-24T15:09:30Z | |
| Date Available | 2024-01-24T15:09:30Z | |
| SWORD Update | 2024-01-22T20:11:08Z | |
| Abstract | Catalysis plays a pivotal role in various industrial processes, enabling the efficient conversion of feedstocks into valuable fuels, chemicals, and products. While insights from computations have increased over the past two decade, most computational studies employ static density functional theory (DFT) and microkinetic modeling, focusing on understanding reaction mechanisms. Dynamics, confinement, and entropic effects, stemming from catalyst mobility, solvent reorganization, and micropores as examples, demand different multiscale models, including classical and ab initio molecular dynamics (AIMD), and enhanced sampling approaches for free energy calculations. This thesis focuses on such phenomena and involves four core chapters, each contributing valuable insights into different catalytic systems. Chapter 2 investigates Brønsted acid catalysis in the direct acylation of 2-methyl furan (2-MF) with acetic acid. Utilizing DFT and microkinetic modeling, the role of Brønsted acidity and confinement in the mechanism and kinetics is examined. Surprisingly, stronger Brønsted catalysts do not consistently result in faster reaction rates, and the proposed rate-determining step does not hold for all catalysts. The study emphasizes the profound impact of stabilizing transition states through confinement and co-adsorption of 2-MF on the direct acylation rate. In Chapter 3, ab Initio molecular dynamics (AIMD) free energy simulations are conducted to investigate the stability and dynamics of dispersed Pd atoms and subnanometer clusters on γ-Al2O3. We explore temperature and entropic effects on Pd nucleation on dry γ-Al2O3(100), dry γ-Al2O3(110), and hydrous γ-Al2O3(110) under diverse water coverages and Pd loadings. This research enriches the understanding of static DFT calculations, providing a dynamic perspective. Continuing the exploration of metal clustering on γ-Al2O3, Chapter 4 focuses on Pt clustering on γ-Al2O3 and Sn-modified γ-Al2O3 surfaces. By employing AIMD free energy simulations, the influence of temperature, surface termination, Pt oxidation, and Pt and Sn loading, on Pt clustering is elucidated. Remarkably, the degree of hydration and Sn:Pt ratio significantly impact the Pt dispersion. The findings offer valuable insights into the dynamics and time scales of Pt nucleation or dispersion, guiding the design of dispersed metal catalysts. Lastly, Chapter 5 investigates unexpected kinetic solvent effects on the activity and selectivity of the fructose to HMF reaction within biphasic catalytic systems. By combining fast experimental reaction kinetics, multiscale modeling, in-situ sampling, IR, and 13C-NMR spectroscopy, we find that fructose reacts faster and more selectively in the organic-rich phase due to increased relative abundance of the reactive furanose isomer, the enhanced water-catalyst-substrate interactions driven by nanophase separation, and the higher product stability stemming from preferential solvation. Our findings suggest that the choice of an acid catalyst and the polarity and hydrophobicity of organic solvents can be tailored to fine-tune reactivity and selectivity in the process. | |
| DOI | https://doi.org/10.58088/h3ve-rz43 | |
| URL | https://udspace.udel.edu/handle/19716/33896 | |
| Language | en | |
| Title | MULTISCALE MODELING OF CONFINEMENT AND DYNAMICS IN HETEROGENEOUS, MULTIPHASE CATALYTIC SYSTEMS |