Glycerol steam reforming over layered double hydroxide-supported Pt catalysts

• Glycerol reforming on catalysts obtained from MgAl layered double hydroxides.
• Weak to moderate basic sites render catalysts more selective to hydrogen.
• More stable carbon deposits play major role in catalyst deactivation.
• Highly dispersed metal sites are important for in situ catalyst surface cleanness.

Layered double hydroxides containing Mg and Al (Mg/Al ratios of 3 and 5) were used as support for Pt-based catalysts for glycerol steam reforming. Additionally, catalysts supported on the parent MgAl mixed oxides were also evaluated. Fresh catalyst samples were characterized by XRD, BET, TPD-CO2 and XRF whilst the spent catalysts were examined by TEM and TPO/TGA-MS. All catalysts revealed to be active, leading to a hydrogen-rich gas stream but with distinct resistance to deactivation. The catalyst synthesized directly from the layered double hydroxide precursors with Mg/Al ratio of 3 was shown to be more effective since global and gas conversion are similar, varying within 60–25%. Major incidence of weak to moderate basic surface centers rendered catalysts more selective, reaching up to 68% selectivity to hydrogen. However, they were not enough to suppress deactivation. It was found that the formation of more stable carbon deposits play a key role on deactivation and only a minor contribution from the carbonaceous material formed from the intermediate organic liquid compounds was proposed. Highly dispersed metal centers were suggested to be important for in situ catalyst surface cleanness.

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