Regeneration of Adsorbent Materials under Plasma Exposure – RAMPE

Indoor air pollution has recently become a major concern and new regulations have been published in western countries to drastically reduce the amount of Volatile Organic Compounds (VOCs) and odors present in confined environments. The technological issue is to remove diluted pollutant at a low energy cost, which excludes any heating like in conventional catalysis. Nowadays market technologies are based on filtration/adsorption or photocatalysis. Drawbacks are the maintenance due to the change of filters for filtration/adsorption technique, and the slow removal rate and poisoning of the photocatalyst. The past 15 years, the coupling of non thermal plasma with catalyst has proven to be efficient for VOCs removal at room temperature. The main drawback is that the plasma has to be switched on continuously. A new approach consists in adsorbing the pollutant on a highly porous adsorbent which is sequentially regenerated by plasma; the main advantage of the proposed technique is that the plasma is switched for a limited time and this reduces significantly the power consumption. It is worth noticing that, although such researches started in Japan, France is now a leading country for studying plasma-catalyst coupling. One of the technical issues is the generation of non-thermal plasma in contact with the catalytic material. Recently, LPTP & Ecole Polytechnique have patented an innovative way, based on surface Dielectric Barrier Discharge sDBD, to couple plasma and catalytic material at a low excitation voltage. In spite of a fact that sDBD discharges have been intensively investigated for nearly 10 years for air flow control, there are only a few papers that analyze air treatment and VOCs decrease under the action of sDBD. Studies of DBD performed at Ecole Polytechnique the past 3 years have shown that their oxidative efficiency is much higher than gas gap DBD [1]. The three groups involved in the RAMPE project have addressed a number of scientific issues: i) The morphology of the discharge and the streamer localization depend drastically on the properties of dielectric [2-4]; ii) most of the oxidative properties of the plasma comes from short live species: this means that the contact between the discharge area and adsorbent/catalytic surface is critical, iii) oxidative intermediates are adsorbed by the surface and they are extremely important species in completing oxidation (mineralization) of VOCs; iv) plasma treatment enhances dramatically adsorption properties of the surface. The three teams are expert in the physics of DBD, in plasma/catalyst coupling, in in situ diagnostic and analysis of the gas phase 'even ppb trace of pollutants- and of the surface. The RAMPE project objective is to understand basic phenomena involved in the generation of a surface discharge in contact to a porous material leading to the oxidative regeneration of the porous adsorbent. The research strategy is to: i) understand the influence of the porous adsorbent and adsorbed VOCs on the power deposition by the discharge, plasma characteristics and spatial structure of the discharge, ii) identify oxidative molecules adsorbed by the adsorbent/catalytic surface, iii) analyze in situ the gas phase chemical composition to estimate the carbon balance and perform a simple kinetic modeling of the discharge. Partners of the project have a lasting experience of mutual collaboration and have already published 7 full shared papers in international journals, 2 patents and more than 35 shared contributions in international conferences.