Synthesis of Coke-Resistant Catalyst Using NiAl₂O₄ Support for Hydrogen Production via Autothermal Dry Reforming of Methane

A highly porous NiAl₂O₄ spinel structure was synthesized and employed as a support for catalysts in the autothermal dry reforming of methane (ATDRM) in a monolithic-type reactor. A series of catalysts with various metal species, X/NiAl₂O₄@monolith (X: Ni, Co, Pt, Rh, and Ru), was prepared. NiAl₂O₄ support provides a high dispersion of active metal species with a uniform size distribution, due to its high surface area, and large pore volume. These features enable catalysts to maximize catalytic performance by improving the adsorption and reaction rates of reactants. More notably, the use of NiAl₂O₄ support enhanced catalyst longevity by retarding coke formation during the ATDRM, due to its improved catalyst acidity compared to conventional alumina support. The conversion of feed, CH₄ and CO₂ on X/NiAl₂O₄ catalysts increases in the order of Rh > Ni > Ru > Co > Pt. Notably, the inexpensive Ni catalyst exhibits slightly lower but comparable CH₄ conversion to the expensive noble metal Rh when using NiAl₂O₄ as a supporting material: 93.7% for Ni versus 95.2% for Rh. Moreover, applying monolithic reactors considerably increased methane conversion compared with fixed bed reactors due to the better distribution of active metal, increased activity per unit volume, and high mass/heat transfer.