THESIS
2019
xiii, 64 pages : illustrations ; 30 cm
Abstract
Carbon plays an important role on Earth. It is integral to the formation of life, the origin
and storage of fossil fuel, and the global climate. Therefore, it is necessary to study
its distribution, long-term cycle, and evolution. The cycle of carbon from Earth’s surface
is of great importance to solve the energy problem and climate change on the geological
time scale. Both the energy problem and global warming are severely threatening human
development. Because this field of research can help to better understand the structure of
the Earth, understanding the behaviour of carbon on Earth is fast becoming an important
topic. For example, the Deep Carbon Observatory (DCO) is a global research programme
aimed at transforming the understanding of carbon’s role in Earth. This thesis...[
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Carbon plays an important role on Earth. It is integral to the formation of life, the origin
and storage of fossil fuel, and the global climate. Therefore, it is necessary to study
its distribution, long-term cycle, and evolution. The cycle of carbon from Earth’s surface
is of great importance to solve the energy problem and climate change on the geological
time scale. Both the energy problem and global warming are severely threatening human
development. Because this field of research can help to better understand the structure of
the Earth, understanding the behaviour of carbon on Earth is fast becoming an important
topic. For example, the Deep Carbon Observatory (DCO) is a global research programme
aimed at transforming the understanding of carbon’s role in Earth. This thesis mainly
focuses on the hydrocarbon reaction in the mantle. During the research, it was noticed
that the results of the water-gas shift reaction at high temperatures and pressures, which
generate formic acid as the final product, was totally different from the findings of previous
studies close to ambient conditions. As such, detailed research was performed on
the mechanism and kinetic thermodynamic properties. This thesis contains six chapters.
Chapter 1 briefly introduces the hydrocarbon reactions and some of the relevant research from recent years, together with a selection of studies on water-gas shift reactions. It also
outlines the objectives of the thesis. Chapter 2 details the techniques that were used to
perform the ab initio molecular dynamics (MD) simulations. Chapter 3 focuses on the
most important part of the research: the water gas shift reaction. First, a series of ab initio
molecular dynamic simulations were conducted on this type of reaction, where it was
found that carbon monoxide has relatively high chemical reactibility. It is able to quickly
react with water at 1400 K and at pressures greater than 10 GPa. Furthermore, the reaction
generates formic acid as a stable final product, while in previous studies, research
mainly focused on industrial conditions (200-450 °C and ambient pressure). These studies
reached the conclusion that the water-gas shift reaction will produce carbon dioxide
and hydrogen from the reactants. It is hoped that this present study will provide further
inspiration for future research in this field. Chapter 4 details other types of hydrocarbon
reactions among H
2O, CO
2, CO, CH
4, H
2, and sodium acetate (CH3COONa). By conducting
similar ab initio MD simulations, some interesting results were found. Hydrocarbon
reactions all tend to form heavier molecules when the temperature and pressure are above
2500 K, 15 GPa. To further study the mechanism, the characteristics of the reaction process
were analysed. Chapter 5 provides theoretical calculations regarding the free energy and
entropy of the water-gas shift reaction. Due to simulation time limits, the formic acid may
be at the metastable state. Hence, this study compares the free energy between the two
sides of the water gas shift reaction. The results indicate that formic acid is stable under
such conditions. Chapter 6 concludes the findings of the study. In addition, an outlook
for future study into hydrocarbon reactions in the deep Earth is also discussed.
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