Preparation of nickel and cobalt based catalysts with urea-nitrate combustion technique for partial oxidation of methane

The evaluation of methane, the main component of natural gas, and its transformation into valuable products is still one of the important issues both in academia and industry fields. Industrially, indirect methods play a major role in converting methane into valuable products and chemicals. The intermediate and most important step in these methods is to obtain synthesis gas (H2 + CO). Although there are many methods in the literature to obtain synthesis gas, the main method for high amounts of production is steam reforming of methane. The biggest disadvantage of this method is the high energy requirement since the reaction is endothermic. Partial oxidation of methane stands out as a good alternative because it is exothermic and reaction rates are 100-1000 times higher. However, the catalysts developed for this method have problems such as Coking and deactivation due to sintering. Researchs have focused on solving these problems. Within the scope of this study, catalysts showing high performance, selectivity and durability for obtaining synthesis gas were synthesized and characterized. For that, catalysts supported by (Al₂O₃, MgAl₂,₅O, Mg₂,₅AlO, MgO) containing 10 wt% Ni or 10 wt% Co were synthesized in a single step using the urea-nitrate combustion technique. The aim here is to prepare the active metals together with the support structure homogeneously without sintering. For this purpose, calculated amounts of Ni or Co nitrate salts and Al, Mg-Al or Mg nitrate salts were mixed with urea dissolved in ultrapure water calculated to be fuel-low and subjected to self-combustion in a 500 °C oven for 15 minutes. The prepared catalysts were then investigated for the partial oxidation of methane at different temperatures (500-800 °C) with a CH₄/O₂ ratio of 2, under high space velocities (GHSV=80,000 L/kg·h). The synthesized catalysts were characterized using X-ray diffraction (XRD), temperature-programmed reduction (TPR), and Brunauer-Emmett-Teller (BET) surface area methods. Based on the results obtained, the highest catalytic activity and selectivity for H2 and CO, respectively 90.2%, 96.5%, and 97.4%, were achieved using the 10Ni/Mg2,5AlO catalyst at 800 °C. It has also been determined that nickel exhibits higher activity and selectivity than cobalt. The results have shown that the urea-nitrate combustion technique could be a good alternative to traditional methods.