Adjusted interactions of nickel nanoparticles with cobalt-modified MgAl₂O₄-SiC for an enhanced catalytic stability during steam reforming of propane

Steam reforming of propane (SRP) for the stable production of hydrogen-rich reformates was investigated using the Ni-supported on the cobalt-modified SiC-embedded MgAl₂O₄ support (denoted as NCMAS). The adjusted interactions of the Ni nanoparticles with the cobalt-modified SiC-embedded MgAl₂O₄ (MgAl₂O₄-SiC) and its crystallite size distributions largely altered the catalytic activity and stability of NCMAS. The introductions of SiC on the NCMAS, where SiC has a higher thermal conductivity, also increased the dispersion of smaller MgAl₂O₄ grains with the less formations of inactive NiAl₂O₄ species, which resulted in the higher catalytic activity with smaller formations of unreformed light hydrocarbons. The positive roles of cobalt promoter on the MgAl₂O₄-SiC matrices were mainly attributed to the suppressed aggregation of nickel nanoparticles by their strong and intimate interactions with the cobalt-modified MgAl₂O₄. The effects of cobalt promoter at an optimal 5wt%Co in the MgAl₂O₄-SiC (NCMAS(5)) enhanced the oxidation-resistance of the nickel nanoparticles with less formations of inactive metal aluminates by being reversibly re-reduced under the SRP reaction conditions. These phenomena further lessen coke depositions by intimately interacting with highly dispersed oxophilic cobalt or cobalt aluminate species. The optimal NCMAS(5) was applied to derive kinetic parameters using Langmuir-Hinshelwood-Hougen-Watson (LHHW) mechanisms, and the reasonable activation energy of 73 kJ/mol and optimal operating parameters to maximize hydrogen production by SRP reaction was estimated in terms of the reaction conditions such as space velocity, feed ratio and reaction temperature.