Conversion of biomass tar containing sulphur to syngas by GdCeO2 coated NiFe bimetallic-based catalysts

• GdCeO2 coating promote sulfur tolerant and carbon deposition resistance of NiFe/MgOAl2O3.
• Ce(SO4)2, Ce2(SO4)3 and Ce2O2S are formed during the steam reforming of naphthalene in the presence of H2S.
• Ce(SO4)2 and Ce2(SO4)3 help NiFe/MgOAl2O3 promote high tar reforming activity.
• Activity of CGO-coated NiFe/MgOAl2O3 can be regenerated by oxidation at 800 °C.

Catalytic activities of pellet-shape NiFe/MgOAl2O3 with and without GdCeO2 (CGO) coating toward steam reforming of naphthalene (as tar model compound) and biomass tar from pyrolysis of eucalyptus in the presence of H2S was studied under various conditions including different temperatures (between 700 and 900 °C), inlet H2S (from 100 to 1000 ppm) and inlet H2O concentrations. It was found that under sufficient conditions CGO coating can efficiently promote sulfur tolerant and resistance toward carbon deposition of NiFe/MgOAl2O3, from which less deactivation occurs after prolong testing (18 h) compared to the catalyst without CGO coating. In addition, the catalyst activity can be completely regenerated by purging air at 800 °C, from which almost the same level of H2 yield can be enhanced after regeneration. It was revealed from the study that in the presence of sufficient H2O concentration, the phase of CeO2 potentially transforms to Ce(SO4)2, which helps NiFe/MgOAl2O3 promote high tar reforming activity. In contrast, with less H2O presenting, Ce2O2S is formed and consequently results in low sulfur tolerant activity. Nevertheless, by purging Ce2O2S with air, the phases of CeO2 and Ce(SO4)2 can be effectively recovered. This study therefore highlights the great benefit of CGO coating over NiFe/MgOAl2O3 for tar reforming in terms of sulphur tolerant promotion and achievable catalyst regeneration.

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