Synthesis of MgAl2O4 supported catalysts for partial oxidation and dry reforming of methane

Today, the majority of methane, which is the main component of natural gas, is used for home heating or as fuel in industry. Natural gas found in oil and coal deposits is usually burned or released into the air, causing environmental pollution. However, instead of being wasted, these natural resources can be transformed into a more valuable product or products through on-site reforming. In order to obtain valuable products, the industry first synthesizes synthesis gas and then synthesizes the product. Steam reforming of methane is the most preferred process. The disadvantages of this method are its high energy requirement and slow rate as a result of being endothermic. Partial oxidation of methane, on the other hand, is a method where research is concentrated because it is partially exothermic and much faster. Research has also focused on dry reforming to utilize CO2, a major greenhouse gas. One of the biggest problems of these reactions is the rapid deactivation of the catalysts used due to sintering or coking. For this reason, research in the processes has focused more on the synthesis of suitable catalysts. In this thesis, synthesis and characterization of catalysts with high activity and selectivity that can be used in both partial oxidation and dry reforming of methane were carried out. For this purpose, MgAl2O4 supported catalysts containing 5 wt% or 10 wt% Ni doped with 5 wt%, 10 wt% or 15 wt% CaO, MgO, SrO, CeO2, Sm2O3 or La2O3 were obtained. These catalysts were characterized using XRD, TPR, specific surface area and TPO analyses and then subjected to activity tests for partial oxidation and dry reforming of methane in the range of 500-800°C. Among a number of methods for synthesizing high surface area MgAl2O4 support structure, the most suitable method was found to be co-precipitation method. MgAl2O4 with high crystallinity and specific surface area (136 m2/g) was obtained by this method. Strongly interacting NiO and NiO from NiAl2O4 formation were detected on the surface of the obtained catalysts. It was found that the reducibility of the catalyst increased with the increase in the amount of Ni. The highest methane conversion and H2 yield for POM was obtained with 10Ni/2Mg catalyst when the reaction conditions were CH4/O2/N2:2/1/4, GHSV=78750 L kg-1 h-1 and temperature was 800°C. At CH4/CO2/N2:11/11/3, GHSV=18750 L kg-1 h-1 and reaction conditions of 800°C, the highest methane conversion and H2 yields for DMR were obtained with 10Ni/2Ce catalyst. These catalysts did not show any signs of deactivation in the stability tests performed for 50 h and under activity test conditions. They showed lower carbonization and sintering rates than the reference catalyst without metal oxide doping. The obtained catalysts were found to outperform many catalysts in the literature.