Hydrogen production over Fe enriched porous clay-based nanocomposites and mesoporous silica in bio-ethanol reforming – The role of the clay component

Abstract

Embedded catalysts, featuring Fe species on the surface of Porous Clay derived Heterostructures (PCH) and mesoporous silica (SBA-15 or MMS type) were developed. Two different methods of iron deposition were applied, affecting different activity in steam reforming of ethanol. The nature and distribution of nanostructured Fe-O moieties formed on the surface of porous supports and the role of clay component in H2 production were investigated by X-ray diffraction (XRD) method, scanning electron microscopy (SEM), temperature-programmed reduction with the hydrogen (H2-TPR), CO2 temperature-programmed desorption (CO2-TPD), and advanced X-ray photoelectron spectroscopy (XPS) and 57Fe Mössbauer spectroscopy (MS). The speciation of Fe moieties in the function of Fe interaction with the support entailed the creation of nanostructured catalysts active in H2 production. Dispersion of the Fe species on the surface of mesoporous silica promoted the dehydration of ethanol to ethylene occurring on the developed acidic sites. The formation of iron oxide nanocrystals was beneficial for H2 production. The introduction of amorphous silica between the layers of Laponite (Lap) in PCH composite resulted in the developing of a flexible base for the embedding of active centres, available to reagents and highly selective to H2. The composition and the basic nature of the Lap in Fe-PCH composites contributed to the increase of H2 content in the reaction products. The applied treatment forced the migration of MgII from the octahedral sheet of Laponite to the PCH surface. The developed Mg entities influenced the basicity of the PCH surface shifting the reaction balance towards hydrogen formation, limiting the dehydration of ethanol to ethylene – the precursor of coke deposits.