(118h) Preparation of Ni-Based Core-Shell Catalysts and Their Application In Steam Reforming of Ethanol for Hydrogen-Rich Gas Production

Hydrogen production through steam reforming of ethanol (SRE) is an attractive technology since ethanol is a renewable raw material obtained from fermentation of various agricultural products (e.g., energy crops, forestry residue, organic waste). Although steam reforming (SR) has been extensively studied in the literature, the development of suitable catalysts is still a significant challenge from the standpoint of catalyst deactivation.

It is known that a good dispersion of the different components favors the final catalyst behavior. The use of precursors in which the metal is homogeneously distributed throughout the catalytic structure, may results, after calcinations and reduction, in the formation of highly-dispersed and stable metal particles on the surface. Starting from hydrotalcite-like precursors, Ni/Mg-Al catalysts have been prepared and were successfully applied in partial oxidation, steam reforming, and dry reforming of methane, ethanol and propane. However, conventional hydrotalcite-derived Ni/Mg-Al catalyst contains uniformly distributed Ni species from the catalyst surface to the bulk by forming Mg-Ni-O solid solutions. As a result, a considerable amount of Ni included in the catalyst bulk becomes irreducible and therefore ineffective for the reaction. It is desirable to prepare supported metal catalysts loaded in core-shell type, i.e., active metal species are concentrated in the surface layer of the catalyst particles where the reforming reaction preferentially proceeds in the micro- and meso-porous space.

This work presents some results for optimization of the synthesis of Ni-based catalysts with a core-shell structure by adopting the “memory effect” of Mg-Al hydrotalcite and for their catalytic application in SRE. The performance of such catalyst is compared with the conventional hydrotalcite-derived Ni/Mg-Al catalyst. The amount of Ni and the depth of Ni layer are significantly affected by the calcinations temperature of Mg-Al mixed oxide, the pH and the concentration of Ni²⁺ nitrate aqueous solution, and the dipping time and dipping temperature of the mixed oxide particle in the aqueous solution. The core-shell type Ni catalyst showed an enhanced activity per unit amount of Ni due to the highly dispersed and surface enrichment of active Ni species.