The effect of nickel loading on the catalytic activity of Ni/MgO-ZrO2 catalyst for the dry reforming of methane

Although economically affordable and readily available, metallic nickel-based catalysts are very susceptible to deactivation during catalysis. Previous studies have found that altering the composition of the catalytic material affects the performance and activity of the catalyst. This study aimed to demonstrate the direct effect of nickel loading (5%, 10%, 15% and 20% [w/w]) on the activity of Ni/MgO-ZrO2 catalyst. The nickel metal precursor was impregnated on a mixture of MgO-ZrO2 by dry impregnation, were calcined for 16 hours at 850C and were reduced for 1.5 hours under a stream of 10% H2/He at 500C. Catalyst characterization was done using AAS, XRD, EDX, SEM and BET methods. The acidity and basicity of catalysts were determined using NH3-TPD and CO2-TPD respectively. Results from the study showed that surface area and pore volume decreased as nickel loading increased to 15% but increased slightly when nickel loading was increased to 20%. Results were further confirmed by SEM results and pore size distribution from BET results. Likewise, EDX results confirmed a close to 1:1 mole ratio of MgO/ZrO2. From XRD results, it was observed that solid solutions formed for all catalysts from calcination at 850C, and that the amount of solid-solution formed increased with loading. The results from AAS reported that the catalysts contained Ni loading from 5.56-14.14.27%. Basic sites decreased while acidic sites increased with increasing Ni loading. The time course activity test for methane dry reforming at 850C enabled the determination of catalyst activity through conversion, H2/CO ratio, stability, yield, and the rate of reaction. Actual conversion was greater than equilibrium conversion indicates that other side reactions are also taking place which aids in the further conversion of methane throughout the activity test. Post characterization enabled the determination of the presence of surface carbon that has deposited during reaction. Results obtained from characterization and activity testing showed that 5% Ni loading is the most suitable for the dry reforming of methane