Plasma-assisted conversion of carbon dioxide
16 October 2017
Campus Drie Eiken, R.003 - Universiteitsplein 1 - 2610 Antwerpen-Wilrijk (route: UAntwerpen, Campus Drie Eiken
Organization / co-organization:
Department of Chemistry
Annemie Bogaerts, Sabine Paulussen
PhD defence Igor Belov - Faculty of Science, Department of Chemistry
The general acceptance of global warming stimulates the scientific community to work on novel and efficient technologies for CO2 utilization. Conversion of CO2 by means of non-thermal plasmas is one of the most promising current developments on this topic. Plasmachemical processes are very versatile, utilize electrical energy and reactor designs based on abundant construction materials. However, the energy efficiencies achieved in those systems so far, limit up to now the potential scale-up of a plasma-based CO2 conversion technology. Besides that, control over the plasma process is not trivial, as the plasma chemistry is often governed by plasma parameters which cannot be directly determined by external settings.
In this thesis we explore novel mechanisms to control and improve CO2 decomposition in Dielectric Barrier Discharge (DBD) and Microwave (MW) plasma systems. In case of a DBD it is accomplished by finding ways to tune the properties of transient microdischarges (also referred as filaments) that make up this type of plasma and define the overall efficiency of the process. It is demonstrated that a higher microdischarge current is beneficial for CO2 conversion in a DBD. This effect can be induced by having a conductive surface on one of the DBD electrodes or via increasing the pressure. Interestingly, upon increase of the microdischarge current a process of metal electrode evaporation can also be triggered. This erosion process results in the re-deposition on the reactor walls, which significantly modifies the electrical properties of the CO2 DBD and can potentially be used to introduce catalyst material into gas-phase.
In contrary to DBD reactors, operating at atmospheric pressure, MW discharges have the highest energy efficiency of CO2 decomposition at lower pressure (~200 mbar). In this thesis it is demonstrated that a pressure increase induces a drop of energy efficiency of the MW reactor due to thermalisation of the MW plasma at near-atmospheric conditions. The properties of the MW discharge can be tuned, however, by adjusting the gas flow regime. It is demonstrated that the vortex gas flow allows the most stable discharge operation and the highest achieved energy efficiency at atmospheric pressure. The obtained information can be useful for further MW plasma reactor scale-up.