Roles of alkali/alkaline earth metals in steam reforming of biomass tar for hydrogen production over perovskite supported Ni catalysts.

• Alkali/alkaline earth metals promote catalytic performance of Ni/LSAO. • Coking resistance is improved by the increased surface-absorbed oxygen. • Superior anti-coking performance of K-loading catalysts below 600 °C. • 0.3 wt% loading of K/Ca/Mg has the best promotion in toluene steam reforming. Biomass steam gasification has a large potential to produce high-purity hydrogen, and perovskites are good candidates to act as catalyst supports in eliminating the biomass tar produced during reforming. However, various alkali and alkaline earth metals are contained in actual biomass, which would be released during reactions and could affect the catalytic performance of perovskite-supported catalysts. To explore potential roles of alkali and alkaline earth metals in the catalysis process, in this work, typical K, Ca and Mg were added into Ni/La 0.7 Sr 0.3 AlO 3−x catalysts, and their performance in steam reforming of toluene as a model of biomass tar for hydrogen production were investigated comprehensively. Catalytic performance shows that the presence of K, Ca, and Mg leads to a better resistance to coking (a reduction of over 60%) and sintering of the Ni/perovskite catalysts utilized, and this trend becomes more pronounced as the decrease of reaction temperature. Furthermore, a series of catalyst characterizations, including XRF, XRD, SEM, TPR, TPD, and XPS were conducted to understand the action mechanism. And results reveal that the presence of K, Ca, and Mg in catalysts promotes the absorption ability of surface oxygen, which could oxidize reaction intermediates or the carbon deposited, thus enabling good reforming properties of the perovskite-supported Ni catalysts in the reforming of biomass tar. [ABSTRACT FROM AUTHOR]