Hydrogen production by glycerol steam reforming over SBA-15-supported nickel catalysts: Effect of alkaline earth promoters on activity and stability

•Valorization of glycerol by steam reforming for hydrogen production.•Ni/SBA-15 catalyst is active in glycerol steam reforming but deactivates.•Smaller Ni particles size and stronger Ni-support interaction by Mg or Ca addition.•Improved catalytic activity and stability by addition of Mg or Ca to Ni/SBA-15.•Best catalytic behaviour and coke resistance with Ni/Ca/SBA-15.

Mg- and Ca-modified Ni/SBA-15 catalysts were prepared by incipient wetness impregnation (7 wt% Ni) to be studied for catalytic glycerol steam reforming at 600 °C. High space velocities were selected in order to highlight differences in activity between catalysts and deactivation effects at relatively short time. Characterization of the calcined, reduced and used samples was carried out by XRD, ICP-AES, N2-physisorption, TGA, H2-TPR, TEM and HCNS elemental analysis. XRD and TEM demonstrated dispersing effect of Mg and Ca on the Ni phase, while TPR evidenced strengthening of the Ni-support interaction by Mg and Ca incorporation to the Ni/SBA-15 catalyst. These effects were significantly noticeable in the Ni/Ca/SBA-15 sample. As a consequence, the Ni/Ca/SBA-15 catalyst achieved the highest glycerol conversion (98.4%) and yield to gases formation (69.9 wt%) with a hydrogen content of 53 vol%. Additionally, this catalyst was stable with time on stream under glycerol steam reforming and showed the lowest coke deposition. This was ascribed to the formation of highly defective carbon deposits, easier to be gasified under reaction conditions, mainly in the form of non-encapsulating carbon nanofibres formed on the small and strongly-supported Ni particles.

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