Short contact time CH4 partial oxidation over Ni based catalyst at 1.5 MPa

Abstract

Abstract Gas-to-liquid technologies to produce Fischer–Tropsch fuels are economically sustainable at very large scales— 30\u2008000\xa0bbl\xa0d−1. To achieve a viable process at a scale less than 100\xa0bbl\xa0d−1 requires a compact design, like a short contact time reactor and mass manufacturing to reduce capital cost. We tested the activity of 2.25\xa0%Ni/0.1\xa0%Ru/CeO2 supported on FeCrAl gauze (Ni2510) to partially oxide methane at a contact time less than 0.050\xa0s. Besides, the very short contact time, an additional feature of this work is that the catalyst activated on-stream without a hydrogen pretreatment step. The reactor operated at 1.5\xa0MPa, 800\xa0 ° C \xa0to\xa0950\xa0 ° C , and a CH4/O2 ratio varying from 1.6 to 1.8 v/v. Methane partially oxidized carbon monoxide (direct mechanism) rather than combusting to CO2 followed by steam reforming to CO (indirect mechanism). The following phenomena support the direct mechanism hypothesis: (i) the selectivity improved when reducing residence time, (ii) the mass spectrometer detected both O2 and CO at the effluent (simultaneously), (iii) metallic Ni clusters on the Ni2510 were absent under reaction conditions based on in situ X-ray absorption spectroscopy. Loading Ni/Al2O3 powder downstream of the Ni2510 increased syngas yield, as this catalyst promoted steam and dry reforming. Soot forms upstream of the Ni2510 catalyst via a retro-propagation mechanism in which methyl radicals produced on the catalyst surface react with the incoming feed gas.