Effect of lattice oxygen in Ni-Fe/Bio-char on filamentous coke resistance during CO2 reforming of tar

Abstract

The catalyst deactivation resulted from filamentous coke deposition limits the application of CO2 reforming technology in solid waste gasification process. The bimetallic Ni-Fe catalysts have excellent encapsulating coke resistance in steam reforming of oxygenates tar, but the filamentous coke resistance of Ni-Fe/Bio-char in CO2 reforming of non-oxygenates tar remains unclear. To investigate the filamentous coke during CO2 reforming process, a non-oxygenates tar, toluene was select as filamentous coke precursor in CO2 reforming experiment. Based on the comparison between Ni/Bio-char and Ni-Fe/Bio-char, the effect of lattice oxygen in on filamentous coke resistance was explored. During CO2 reforming experiment, Ni-Fe/Bio-char showed higher hydrogen conversion (48.90–56.33%) and carbon conversion (53.57–62.94%) than Ni/Bio-char. Besides, the iron sites in the Ni-Fe oxide can be converted to iron oxide under CO2 atmosphere, providing more lattice oxygen to oxidize the filamentous coke deposition on catalysts surface. However, the lattice oxygen in Ni-Fe/Bio-char was rapidly consumed by the oxidation of massive filamentous coke, resulting in 21% of filamentous coke still accumulated on Ni-Fe/Bio-char. Overall, in addition to the oxidation capacity of filamentous coke, the inhibition ability to filamentous coke formation is critical to the filamentous coke resistance of catalyst in CO2 reforming of tar. The obtained results can provide a reference for the design of catalyst applied in CO2 reforming.