Host institution: University of Antwerp
Supervisor: Annemie Bogaerts
Start date: June 2019
Gross salary: ~27 000 € /year (may vary according to institution).

Title: Improving the energy efficiency of CO2 conversion and activation in a microwave plasma by a combination of experiments and modeling


Plasma-based CO2 conversion is worldwide gaining increasing interest. The aim of this project is to improve the energy efficiency of CO2 conversion in a microwave plasma (MW) beyond what is feasible in thermodynamic equilibrium. It has been demonstrated that microwave plasmas can yield very high energy efficiency for CO2 conversion, but typically only at reduced pressure. For industrial application, it will be important to realize such good energy efficiency at atmospheric pressure as well. However, current experiments at NWO-I illustrate that the microwave plasma at atmospheric pressure is too close to thermal conditions to achieve a high energy efficiency. In this project we will use a combination of modeling and experiments to better understand the underlying mechanisms of CO2 conversion in MW, in a wide range of conditions. This should allow us to predict how the conditions can be tuned to optimize the energy efficiency, in combination with a good conversion. The modeling will be based on both a 0D chemical kinetics model and a 2D plasma fluid dynamics model. The 0D model will describe the detailed plasma chemistry, with special focus on the vibrational kinetics of CO2, as the latter is known to play a crucial role in the energy efficient CO2 conversion. The model will also be extended to CO2 mixtures with H-source, such as CH4, H2O and H2, which is of great importance for the production of value-added chemicals out of CO2. The 2D plasma model will use simplified plasma chemistry, as obtained from the 0D model, and give information on the effect of various microwave plasma reactor designs and gas flow patterns, as well as on pulsed operation, on the CO2 conversion and energy efficiency. The experimental part will connect to the modeling by combining a study of the factors that deteriorate the non-thermal regime and mixtures with the same H-sources. Essential ingredients in unraveling the transition are pulsed operation in which response of gas temperature and plasma volume are recorded. The application of a comprehensive set of advanced diagnostics will allow comparison with and ultimately validation of the model predictions. In particular, laser scattering will be used for gas temperature profiles in time and space, as well as Fourier Transform Infrared Spectroscopy to monitor in and ex situ species evolution. The link to catalysis will be implemented in the afterglow of the plasma. In this region, Resonance Enhanced Multi-Photon Ionization will be employed to characterize species activation prior to interaction with the catalytic surfaces. Emphasis here will be on proving the possibility to separate species activation in the plasma phase from the reactivity (and selectivity) at the catalyst surface.

Links with other ESRs: Comparison of model approaches for optimization of vibrational kinetic description

Expected Results:

  • Understanding of the role of the vibrational kinetics of CO2 on the CO2 conversion and energy efficiency in a microwave plasma in a wide range of conditions
  • Prediction of the most suitable conditions for the most energy efficient CO2 conversion, in pure CO2 and in mixtures with a H-source
  • Determination of most suitable condition for high vibrational excitation that could be used in combination with catalyst

Co-supervisor: Gerard Van Rooij (FOM-NWO), 18 months, The ESR will be trained in both 0D chemical kinetics and 2D plasma fluid dynamics modelling at UAntwerp, as well as in the use of plasma diagnostics equipment at DIFFER NWO in Eindhoven, The Netherlands

Additional Secondments: A secondment is planned at IST-IPFN for comparison of modeling approaches and numerical techniques (2 months)