Novel boehmite transformation into γ-alumina and preparation of efficient nickel base alumina porous extrudates for plasma-assisted CO2 methanation

Homogeneous low pressure cold plasma glow discharge was used for both boehmite to gamma alumina transformation as well as for catalytic CO2 conversion into methane. Novel plasma-assisted boehmite transformation into alumina was successfully achieved at lower temperature (80 °C less) and shorter period of time (1 h less) than the classical transformation. The final alumina structure properties were improved. The mechanism of the novel plasma-assisted boehmite transformation was addressed. Nickel alumina porous extrudate preparation was optimized and fully characterized. The amounts of binder and nitric acid used during the preparation of extrudates were studied. The concentration of nitric acid presented a major role in the catalytic properties of these catalysts leading to the improvement of the active phase dispersion and reducibility. As a result, methane yield was also improved with support acidity. A simulation study was performed in order to evaluate the influence of the extrudates dimensions on the pressure developed inside the reactor and on the glow discharge stability. It was demonstrated by simulation the need of shaping the nickel alumina catalysts for allowing the generation of a stable plasma discharge through the catalytic bed. Plasma-assisted CO2 hydrogenation under partial vacuum was carried out using the optimized nickel alumina extrudates. Formulation of efficient nickel alumina porous extrudates is provided for plasma or even industrial CO2 methanation reactors.