Investigation of support effects during ethanol steam reforming over a Ni/sepiolite catalyst

Sustainable hydrogen production can be achieved efficiently by steam reforming of bio-ethanol. The use of low-cost and abundant minerals as catalyst supports can further improve the sustainability of the process. In this work, a kinetic study of ethanol steam reforming is presented using a Ni catalyst supported on natural sepiolite. Focus is placed on probing the effect of the support on the reaction mechanism, which is found to depend on the catalyst calcination temperature and degree of hydration of the sepiolite. Results suggest the presence of more than one adsorption sites where both oxygenates and water can competitively adsorb, when the catalyst has not been exposed to temperatures higher than 500 °C. This bifunctional mechanism is further found to be affected by the feed steam/carbon ratio. Thermally pre-treating the catalyst at 550 °C leads to an irreversible removal of support silanol groups that hinders the adsorption of reactants on sepiolite. Hydrating the non-thermally treated catalyst prior to experiments through steam exposure enhances the density of support adsorption sites leading to kinetic performances in line with those over inert supports such as SiO2. Steam reforming of acetaldehyde, a major product of ethanol steam reforming, is also carried out leading to similar observations, building a consistent kinetic picture of the reaction over Ni/sepiolite.