Promoting effect of MgO addition to Pt/Ni/CeO2/Al2O3 in the steam gasification of biomass

概要

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Pt/Ni/CeO2/Al2O3 catalyst showed the high performance in the steam gasification of cedar wood at the initial stage, however, the catalyst was deactivated within 2 h. According to the catalyst characterization by means of XRD and Ni K-edge EXAFS, it is found that aggregation of Ni metal particles causes the deactivation. In contrast, the Pt/Ni/CeO2/MgO/Al2O3 showed the high catalytic activity and stability. The addition of MgO to Pt/Ni/CeO2/Al2O3 decreased the reduction degree of Ni, but increased the dispersion of the Ni metal particles. As a result, the activity of Pt/Ni/CeO2/MgO/Al2O3 was comparable to that of Pt/Ni/CeO2/Al2O3. The Pt/Ni/CeO2/MgO/Al2O3 had high resistance to the aggregation, which can be related to high stability. Another important point is that the aggregated Ni particles on the Pt/Ni/CeO2/MgO/Al2O3 became re-dispersed by the catalyst regeneration (oxidation and reduction). The re-dispersion can proceed via the formation of the NiO–MgO solid solution by oxidation and the reduction of the NiO–MgO from the results of XRD and Ni K-edge EXAFS.