In situ XAS study of an improved natural phosphate catalyst for hydrogen production by reforming of methane

• The mechano-chemical treatment of natural phosphate improves the catalytic properties.
• Nickel on the modified phosphate yields a very active and stable catalyst.
• The interaction of nickel with the support is stronger after ball-milling, yielding a surface nickel–calcium mixed phosphate phase.
• After reduction, in situ XAS shows very tiny Ni particles stabilized on the surface of the phosphate support.

Some nickel catalysts supported on natural phosphate (NP) have been tested for the dry methane reforming reaction. Although the original impregnated 15%Ni/NP catalyst has no activity at all, the modification of the support by mechano-chemical and/or acid treatment strongly improved the catalytic performance, yielding a series of very active and stable catalysts. The chemical and physical characterization by X-ray diffraction (XRD), temperature programmed reduction (TPR), in situ X-ray absorption spectroscopy (XAS) and other techniques have shown that these treatments mainly modify the interaction between the nickel phase and the support surface. The nickel ions occupy calcium position in the surface of the phosphate phase, which stabilizes and improves the dispersion of nickel species. The final reduced catalysts present a much better dispersed metallic phase interacting with the NP surface, which has been identified as responsible for the observed outstanding catalytic performances.

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