Atomistic multiscale modeling of char combustion reactions

Um die anthropogenen CO2-Emissionen zu verringern, werden Technologien zur CO2-Abscheidung und -Speicherung benötigt. Das Oxyfuel-Verfahren ist eine dieser Technologien zur Stromerzeugung. Diese Dissertation konzentriert sich auf die atomistische Modellierung von Koksverbrennungsreaktionen. In den Abschnitten II und III wird gezeigt, dass die Reaktions- und Aktivierungsenergien elementarer Reaktionsschritte abgeschätzt werden können, indem die Reaktionsstellen von Polyaromaten untersucht werden, die sich in Größe und Positionstyp unterscheiden. Namentlich wurden die Oxidation von Polyaromaten mit einem O-Atom zu CO und die Abstraktion eines H-Atoms aus Polyaromaten untersucht. In den Abschnitten IV und V geht es um die Automatisierung von reaktiven Kraftfeld-ReaxFF-Simulationen, die Analyse der Trajektorien und die Verfeinerung der nachgewiesenen Bindungsbruch- und Bildungs-Ereignisse durch Dichtefunktional- und Coupled-Cluster-Theorie.Carbon capture utilization and storage technologies will be needed to decrease anthropogenic carbon dioxide emissions. Oxyfuel combustion is one of these technologies used in power generation. This dissertation focuses on atomistic modeling of char combustion reactions. In sections II and III, it has been shown that the reaction and activation energies of elementary reaction steps can be predicted by studying sets of polyaromatics varying in their size and site types. These sections study the elementary reaction steps of oxidation of polyaromatics with an oxygen atom to form carbon monoxide, and hydrogen abstraction from polyaromatics with an hydrogen atom. The sections IV and V are about the automation of the reactive force field ReaxFF simulations, the analysis of these trajectories, and the refinement of the detected bond breaking and formation events by density functional theory and coupled cluster theory, in order to explore elementary steps of combustion reactions

Terahertz VRT Spectroscopy of the Water Hexamer-h12 Cage: Dramatic Libration-Induced Enhancement of Hydrogen Bond Tunneling Dynamics.

We report the assignment and analysis of 176 transitions belonging to a librational band of the (H2O)6 cage isomer near 525 cm-1(15 THz). From a fit of the transitions to an asymmetric top model, we observe both dramatic changes in the rotational constants relative to the ground state, indicating significant nonrigidity, and striking enhancement in the tunneling motions that break and reform the hydrogen bonds in the cluster. This is the fifth water cluster system to display such an enhancement in the 15 THz librational region, the details of which may help to elucidate the hydrogen bond dynamics occurring in bulk liquid water

Terahertz VRT Spectroscopy of the Water Hexamer-h12 Cage: Dramatic Libration-Induced Enhancement of Hydrogen Bond Tunneling Dynamics.

We report the assignment and analysis of 176 transitions belonging to a librational band of the (H2O)6 cage isomer near 525 cm-1(15 THz). From a fit of the transitions to an asymmetric top model, we observe both dramatic changes in the rotational constants relative to the ground state, indicating significant nonrigidity, and striking enhancement in the tunneling motions that break and reform the hydrogen bonds in the cluster. This is the fifth water cluster system to display such an enhancement in the 15 THz librational region, the details of which may help to elucidate the hydrogen bond dynamics occurring in bulk liquid water