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

Methane dry reforming is one of the important catalytic processes used in the conversion of CH4 and CO2 to synthesis gas which later can be used as feedstock for the processing of other uNful chemicals such es methanol and oxygenated compounds. The dry reforming of methane uses catalysts, often nickel-based, to increase the reaction rate. At present, methane dry reforming has limited commercial application due to the rapid deactivation of the catalysts. Both of the reactants contain carbon species that has a high potential of blocking active sites on the surface of the catalysts causing deactivation. Past researches have shown that the type of support material is critical in controlling the amount of carbon deposited on the surface of the catalyst during methane dry reforming. A support material like MgO-ZrO2 is predominantly basic and is preferred since it discourages the formation of inactive carbon deposits. In addition, ZrO2 has been shown to provide mobile oxygen species that can also minimize carbon deposition. However, little has been done to understand the effect of nickel loading on the catalytic activity of the Ni/MgO­ZrO2 catalyst. This study investigated the effect of varying levels of nickel loading, (5% to 20% mass fraction) on the surface area, pore width, pore volume, surface morphology, the number of acidic sites and basic sites on the surface, and the catalytic activity of the Ni/MgO-ZrO2 catalysts. For catalyst performance, HzfCO ratio, CH4 conversion, yield, and stability were investigated. The catwsts were prepared, using the dry impregnation method where MgO and ZrO2 were thoroughly mixed to achieve a 1:1 mole ratio iri the dual support. Ni(N03)i-6H2O was used as the catalyst precursor and was impregnated onto the surface of the support materials. The catalysts were calcined in air at 850°C for 16 hours. They were pelletized, crushed, and sieved until the desired particle size of + 20 mesh and - 40 mesh was achieved. They were then reduced under a 100mL/min stream of 10% H2/He at 500°C for 1.5 hours. Catalytic activity was tested under a l00mL/min stream of 10/90 (1:1 CH4-CO2)/N2. Catalyst characterization was conducted using the AAS, Autosorb-I, SEM-EDX, XRD, and TPD. Key results indicated marked differences in the surface characteristics of the catalysts depending on the amount of nickel impregnated. Results from activity tests have been found to be consistent with surface data. It appeared that 5% Ni/Mg0-ZrO2 may be the best nickel loading among those tested