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Accueil > A propos du LPP > Communication > Actualités archivées > 2016 > SYCAMORE project Kick off : how to recycle CO2 in a clean and useful way

SYCAMORE project Kick off : how to recycle CO2 in a clean and useful way

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Dispositif de mesure par diffusion Raman de la température du gaz dans une décharge de CO2 : détail.CO2 recycling is a major environmental, economical and societal priority. Carbon capture technologies have improved significantly and instead of being a waste, CO2 could become a raw material for a “green” organic chemistry or fuel production. Many techniques are investigated to achieve an efficient conversion of CO2 and a lot of efforts are especially made in the development of new catalysts. However the difficulty to dissociate CO2 which is a strongly endothermic process still remains. Like any other molecular chemical reaction, the reactivity of CO2 in gas phase and on surfaces could be strongly enhanced if the CO2 molecule is vibrationally excited.
Low Temperature Plasmas can excite molecules very efficiently with high vibrational levels. For pressures favorable to energy transfer between vibrational levels, typically between 10 to 300 mbar, up to 90% of the energy injected into LTP can be stored into vibrational excitation of molecules. Therefore an efficient coupling of highly vibrationally excited molecular plasmas with a catalyst surface is a promising approach for CO2 conversion or any other molecule conversion process.
Plasma/catalysis coupling is usually studied at atmospheric pressure with non homogeneous filamentary plasmas and high collision rate converting vibrational energy into gas heating. On the contrary, the coupling of mid range pressure low temperature plasma (MP-LTP) with catalytic materials is an original approach that can advance the understanding of plasma kinetic and plasma/surface interaction in several respects. First, the vibrational kinetic of molecular plasmas, especially with CO2 and its three vibrational modes, still needs both experimental and modelisation works for an accurate description. Second, the possible role of vibrationally excited molecules on surface mechanisms (adsorption, reactivity, desorption) is still to a large extent unknown. Third, the enhanced reactivity of a population of molecules with a given vibrational distribution needs to be clarified. SYCAMORE aims to address these questions by using a combination of well controlled plasma sources and a set of time resolved is situ diagnostics, both in gas phase and on surfaces to achieve a deep understanding of plasma surface interaction at mid range pressures. Vibrational excitation of molecules is often seen in plasma physic as a loss of energy for sustaining the plasma. The vision behind this project is on the contrary that LTP have the appropriate mean electron energy to build up a large energy reservoir into vibrationally excited molecules that should be used for efficient chemical reactions. The little use made of highly vibrationally excited plasmas for chemical reactions certainly come from the complexity of vibrational kinetic in plasmas. SYCAMORE aims to know if reactions occurring on a surface exposed to plasma can take advantage of vibrationally excited molecules or not. Therefore the first plasma source will not be designed to optimize the vibrational excitation, but to make diagnostics (electric field, gas and vibrational temperatures, radicals and molecule densities) and modelisation easier in order to build an accurate kinetic model of pure CO2 plasmas. When a precise description of this source will be achieved, the influence of model surfaces such as porous SiO2, CaO or MgO will be evidence and quantify with both gas phase and surface in situ diagnostics, before suing these materials in combination with more efficient plasma sources. The results are expected to be generally useful to any CO2 conversion by plasma in pure CO2, or with CH4 and H2 for instance. The methods developed in SYCAMORE would also give an efficient way to investigate other molecule synthesis by plasma such as NO or NH3 for instance.

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CNRS Ecole Polytechnique Sorbonne Université Université Paris-Saclay Observatoire de Paris
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Hébergeur : Laboratoire de Physique des Plasmas, Ecole Polytechnique route de Saclay F-91128 PALAISEAU CEDEX
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