Observation of surface species in plasma-catalytic dry reforming of methane in a novel atmospheric pressure dielectric barrier discharge in situ IR cell

• Published in: Catalysis science & technology Vol. 12; no. 22; pp. 6676 - 6686
• Main Authors: Van Turnhout, Joran, Aceto, Domenico, Travert, Arnaud, Bazin, Philippe, Thibault-Starzyk, Frédéric, Bogaerts, Annemie, Azzolina-Jury, Federico
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 14.11.2022
• Subjects: Atmospheric pressure; Catalysis; Catalysts; Catalytic converters; Chemical Sciences; Dielectric barrier discharge; Discharge cells; Engineering Sciences; Formic acid; Heating; Methane; Plasma; Plasmas; Reaction mechanisms; Reforming; Silicon dioxide; Surface reactions
• ISSN: 2044-4753; 2044-4761
• DOI: 10.1039/D2CY00311B

We developed a novel in situ ( i.e. inside plasma and during operation) IR dielectric barrier discharge cell allowing investigation of plasma catalysis in transmission mode, atmospheric pressure, flow conditions (WHSV ∼0–50 000 mL g −1 h −1 ), at relevant discharge voltages (∼0–50 kV) and frequencies (∼0–5 kHz). We applied it to study the IR-active surface species formed on a SiO 2 support and on a 3 wt% Ru/SiO 2 catalyst, which can help to reveal the important surface reaction mechanisms during the plasma-catalytic dry reforming of methane (DRM). Moreover, we present a technique for the challenging task of estimating the temperature of a catalyst sample in a plasma-catalytic system in situ and during plasma operation. We found that during the reaction, water is immediately formed at the SiO 2 surface, and physisorbed formic acid is formed with a delay. As Ru/SiO 2 is subject to greater plasma-induced heating than SiO 2 (with a surface temperature increase in the range of 70–120 °C, with peaks up to 150 °C), we observe lower amounts of physisorbed water on Ru/SiO 2 , and less physisorbed formic acid formation. Importantly, the formation of surface species on the catalyst sample in our plasma-catalytic setup, as well as the observed conversions and selectivities in plasma conditions, can not be explained by plasma-induced heating of the catalyst surface, but must be attributed to other plasma effects, such as the adsorption of plasma-generated radicals and molecules, or the occurrence of Eley–Rideal reactions.