Role of filamentous coke in deactivation of Ni/bio-char catalyst during dry reforming of non-oxygenates tar

Abstract

During tar reforming process, the coke deposition limits the catalyst activity. The encapsulating coke has been confirmed to be responsible for catalyst deactivation in steam reforming of oxygenates tar, while the role of filamentous coke in catalyst deactivation in dry reforming of non-oxygenates tar remains unclear. In this work, the conventional impregnation method and one-pot hydrothermal carbonization method were used to synthesize Ni/bio-char. The catalyst activity and coke deposition on catalysts in dry reforming of toluene were explored. The characteristics of fresh catalysts revealed that the high pressure and temperature in one-pot synthesis method improved the nickel content (6.72–55.20 %), promoting the catalyst activity in tar conversion. However, due to the coke accumulation on Ni/bio-char, the hydrogen conversion declined with the reaction proceeding. The characterizations of spent catalysts indicated that the dominant coke deposition on Ni/bio-char was filamentous coke in dry reforming of tar, which accounted for 7.35–36.16 %. The filamentous coke produced by the Boudouard reaction consumed the CO in gaseous products, which reduced the syngas quality. Overall, large amounts of filamentous coke deposition can result in the deactivation of Ni/bio-char in dry reforming of non-oxygenates tar.