(Invited) Atmospheric Pressure Plasmas for Gas Processing : N2 Fixation and CO2 Conversion into Value-Added Compounds

Abstract

Plasma-based N2 fixation into NH3 or NOx (for fertilizer applications) and plasma-based CO2 conversion into value-added compounds are gaining increasing interest [1-4]. However, for real implementation, these applications need to be further improved, in terms of conversion, energy efficiency and product formation. We perform experiments in different types of plasma reactors (i.e., gliding arc (GA) plasmas in various configurations, dielectric barrier discharges (DBDs), microwave (MW) plasmas and atmospheric pressure glow discharges (APGD)), as well as plasma-liquid interactions, to investigate their performance. This is supported by computer modelling, to obtain a better insight in the underlying mechanisms.We will first provide a brief overview of the state-of-the-art in plasma-based CO2 (and CH4) conversion and N2 fixation, with different types of plasma reactors, and explain the benefits and limitations compared to other technologies. Subsequently, we will present some recent results obtained in our group. This includes experiments in the various plasma reactors, as well as modeling. We use 2D or 3D computational fluid dynamics modelling for improving the plasma reactor design. This is complemented with 0D (or quasi-1D) chemical kinetics modeling, which solves continuity equations for the various plasma species, based on production and loss terms, as defined by the chemical reactions.We will show the role of vibrationally excited CO2 or N2 levels for energy-efficient CO2 or N2 conversion, as well as the role of thermal conversion in warm plasmas (such as GA and MW plasmas) and quenching after the plasma.[1] R. Snoeckx and A. Bogaerts, Plasma technology – a novel solution for CO2 conversion ? Chem. Soc. Rev. 46, 5805-5863 (2017).[2] A. Bogaerts and E. Neyts, Plasma technology: An emerging technology for energy storage, ACS Energy Lett. 3, 1013-1027 (2018).[3] K.H.R. Rouwenhorst, Y. Engelmann, K. van ‘t Veer, R.S. Postma, A. Bogaerts and L. Lefferts, Plasma-driven catalysis: green ammonia synthesis with intermittent electricity, Green Chemistry, 22, 6258-6287 (2020).[4] K. H. R. Rouwenhorst, F. Jardali, A. Bogaerts and L. Lefferts, Plasma-based NOX synthesis: From the Birkeland-Eyde process towards energy-efficient plasma technology, Energy Envir. Sci. (2021). (DOI: 10.1039/D0EE03763J)