The continuous effort of the nations both the developed as well as the developing countries to preserve or to establish the prosperity for their population results in an increasing global need for primary energy; however, this energy request is in particular responsible for the increasing concentration of carbon dioxide in our atmosphere. As a result, we have to face the problem of climate change and the associated change of the environment in the near future. Hence, leading scientists call for a rigorous reduction of anthropogenic CO2 emission to avoid most of the negative consequences for life on earth. To achieve this target, the shift from fossil fuels to renewables or, alternatively, sequestration of carbon dioxide (carbon capture and storage, CCS) seems to be the obvious solution; that is the injection of CO2 into geological formations. However, renewable power generation is prone to strong fluctuations and incapable to provide the base load. In addition, a possible CO2-leakage and its unknown environmental consequences are the big issue accompanied with CCS. Therefore, the utilization of CO2 (e.g. captured from flue gas of gas- or coal-fired power plants) and renewable H2 in the power to liquid process (PTL) are a promising way to get elegantly rid of the large amounts of otherwise emitted carbon dioxide. This three-step process consists of (i) water electrolysis, (ii) reverse water-gas shift (RWGS), and (iii) Fischer-Tropsch synthesis (FTS). Here, the syngas entering the FTS unit always contains carbon dioxide because the CO2-conversion in the RWGS reactor is incomplete due to thermodynamic constraints. Thus, it is of interest if carbon dioxide influences the kinetics of the cobalt catalyzed FTS. Moreover, under effective reaction conditions (i.e. millimeter sized catalyst particles for industrial application), internal mass transport limitations affect the FT reaction; this leads to a rising H2-to-CO ratio inside the particle which is reflected in the local reaction rate and selectivity. Hence, the interplay between the reaction and the pore diffusion during the heterogeneously catalyzed Fischer-Tropsch synthesis has to be investigated to optimize the PTL process and minimize the CO2 emission.
|School:||Universitaet Bayreuth (Germany)|
|Source:||DAI-C 81/4(E), Dissertation Abstracts International|
|Subjects:||Environmental engineering, Climate Change, Alternative Energy|
|Keywords:||Carbon dioxide capture|
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