Catalytic H2 production from wastes and biomass is a technology to deliver H2 for the carbon-constrained future. However, these resources often contain high concentrations of sulfur. Gasified gas of tires and biogas contains more than 1000 ppm of H2S. Such H2S deactivates catalysts and causes carbon deposition on them. Herein, we demonstrate that CeO2 based catalysts exhibit stable activity for the dry reforming reaction of CH4 in the presence of H2S. Pure CeO2 improved its catalytic activity for CH4 reforming reaction in the presence of 2000 ppm H2S. In situ S K-edge X-ray absorption spectroscopy and infrared spectroscopy clarified that sulfur contributes to higher activity by accelerating oxygen mobility on the catalysts. The catalyst also retained its activity for an 8-h reaction. No carbon deposition or impurity phases formed after the reaction. These results suggest that pure CeO2 is tolerant against H2S and carbon deposition. Further, to suppress the usage of rare earth metal oxide, CeO2 nanoparticles were deposited on MgO. The CeO2/MgO exhibited comparable activity to pure CeO2 despite its low content, 5 mol%, of CeO2. The high activity of the CeO2/MgO catalyst is investigated using in situ measurement techniques. CO2 preferentially adsorbed at the CeO2-MgO interface as evidenced by infrared spectroscopy. Isotope labeling study showed that this interfacial CO2 behaved as a reservoir of oxygen to accelerate the reaction of CH4.

CeO2 and CeO2/MgO catalysts for H2 production from sulfur-rich wastes and biomass

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