Reduced reaction kinetics model for CO2 dissociation in non-thermal microwave discharges

Abstract

In the context of CO2 utilization, the electricity surplus from renewable energies can be used in a non-thermal microwave plasma reactor to reduce CO2 and produce chemical fuels. The chemical processes in non-thermal plasma are extremely complex due to the large number of excited species, radicals and ions that are present. Energy stored inside these energetic species can initiate reactions that in thermal chemistry are difficult to achieve. In the case of non-thermal CO2 microwave plasma, the energy stored in the vibrational modes can effectively stimulate dissociation reactions. Numeric models are being developed to get insights into this process and predict the performance of reactors under different conditions. However, the most recent kinetic model for CO2 dissociation in this type of plasma is highly complex and not suitable for multidimensional simulations. It considers +100 species and +10000 reactions. A reduced kinetic model is developed by only including dominant reactions and by grouping the asymmetric vibrationally excited states of CO2 into a fictitious species. The kinetic model is then reduced to 44 reactions and 13 species. Its validation is done in a 2D reactor model with computation times lower than 25 minutes. The results are in good agreement with those reported in the detailed kinetic model. Furthermore, it is shown that the reduced kinetic model can be adjusted to experimental results. Prospectives are given regarding the next steps in the development of self-consistent multidimensional models. The proposed kinetic model is intended for multidimensional simulations of non-thermal plasma reactors and facilitate the design and operation of these in industrial applications.