Gubareni I. Tri-reforming of methane with involving carbon dioxyde, steam and oxygen over metal-oxide nickel-alumina catalysts

The thesis is devoted to development of structured nickel-alumina catalysts, promoted with rare-earth (Ce, La), alkaline (K, Na) and alkaline-earth (Ca, Mg) elements for tri-reforming of methane, to studying of influence of catalytic composition on it activity and selectivity and influence of reactive gas composition on processes of oxidative conversion of methane into synthesis-gas. Nickel-alumina catalysts supported on cordierite monoliths of honeycomb structure surpass essentially the conventional granulated ones with respect to the output in carbon dioxide reforming of methane. Adjusting the surface acid-base properties of catalysts by introduction of alkali metal (Na, K) oxides inhibits the carbonization and as a result, improves the operational stability of these catalysts. An effect of promotion of nickel-alumina based composite doped by lanthanum oxide is found. This effect, caused by an additional route for the CO2 activation on Ni-La2O3/Al2O3/cordierite catalyst, is displayed in increase of methane conversion under conditions of an oxidant excess. It has been established that oxides of the rare-earth elements with moderate redox potentials (La2O3, CeO2) increased the activity and working stability of Ni-Al2O3/cordierite catalysts in the reactions of deep and partial oxidation of methane. In the presence of the (NiO + La2O3 + Al2O3)/cordierite catalyst the process of carbon dioxide conversion of methane can be intensified by introduction of oxygen into the reaction gas mixture which decreases the temperature to achieve high conversion to 75-100 °C and has practically no effect on selectivity with respect to H2.