Effect of H2O vapor on plasma-assisted partial oxidation of CH4 over PtOx/BN nanoribbon aerogel catalysts

Abstract

Ultralight BN nanoribbon aerogels confined highly dispersed PtOx nanoparticles (NPs) catalysts (PtOx/BN-na) were prepared and utilized for plasma-assisted partial oxidation of CH4 (POM) in a CH4−O2 flow system with H2O vapor cofeed at low temperature. The synergistic effect of H2O vapor and Pt2/BN-na catalyst overcomes a tradeoff problem between CH4 conversion and oxygenate selectivity, achieving 95% selectivity towards incomplete oxidation products at a 13% CH4 conversion. The total oxygenate productivity reached 106.5 mmoloxy gcat−1 h−1, which is one of the best results among the state-of-the-art catalysts for gas and liquid POM reaction. Based on experimental results of D and O18 isotope labelling, in situ OES, and in situ DRIFTS, the surface reactive hydroxyl groups or/and •OH radical, generated from the plasma-activated reaction of H2O + O2 on PtOx NPs active sites, are suggested as key factors to promote the POM reaction. The results of the Catalyst Surface Plasma-Assisted Oxidation Reaction (CSPOR) demonstrate that H2O not only promotes the selective oxidation of chemisorbed hydrocarbon species to oxygenate species, but also facilitates the desorption of oxygenates from the catalysts.