The thesis is devoted to the scientific basis development of the creation of effective catalysts for the heterogeneous catalytic processes of oxidative conversion of CO and methane, based on the representation of the catalyst structure, as a summation of its components with a certain relationship and spatial location. An example of CO oxidation reaction, deep oxidation of methane, oxidative methane carbonylation to acetic acid and its derivatives, and preferential oxidation of CO in hydrogen is shown that the main factor determined the selective action of catalysts in the direction of deep, selective, and preferential oxidation is the structure of the active site.
For each reaction type, regardless of the chemical nature of the catalyst components, the structure of the active site has certain common features. It has been shown that the stabilization of the active site under reaction conditions, in particular at high temperatures of deep oxidation and oxidative methane carbonylation reactions, and the reducing medium of the preferential CO oxidation is ensured by creating a certain structure of nano-phase catalyst related to its structural- dimensional characteristics and spatial location of components. The dependences of the activity in the CO oxidation of binary oxide catalysts from the size of the nanoparticles of the components are determined due to the peculiarities of their structural organization arising from different contents of the crystalline phase (Cr2O3-Al2O3); agglomeration of nanoparticles (CuO-MgO, Y2O3/ZrO2, Fe2O3-Al2O3, WOx/SiO2), phase transformations γ-Fe2O3 → α-Fe2O3 (Fe2O3-Al2O3); formation of grain boundaries (Y2O3/ZrO2).
Based on the catalytic properties study of the ferrite structure spinels MeFe2O4 (Ме = Co, Ni) in the methane deep oxidation, the influence of the preparation method on their activity is established. The effect of the size factor on the reaction rate, consisting of increasing the specific activity of ferrites when the size of their particles decreases. As a result, a decrease of the total methane conversion temperature on 100–150 °С, has been achieved.
It has been shown that the addition of structural and textural modifiers (oxides La, Ba, Sr) to aluminum manganese oxide catalysts leads to stabilization of nano-disperse components - manganese oxides and metastable modifications of the support (γ-, χ-, θ- і ϰ-Al2O3). This improves the thermal stability of catalysts after high-temperature treatment. The efficiency of a method for producing multi-component nanophase aluminum manganese oxide catalysts under nonequilibrium conditions with supersaturated solutions is substantiated. As a result, 100% methane conversion at temperatures of 550-600ºC has been achieved.
At first, the methane oxidative carbonylation in the gas phase has been carried out to produce acetic acid and its derivatives, using as an oxidant of molecular oxygen in the presence of catalysts, the active phase of which are the products of thermal decomposition of rhodium selenochlorides of on carbon and silica-based supports.
The influence of structural-dimensional characteristics of the components of oxide copper-ceria systems and the chemical nature of the support (alumina, titania, zirconia, and manganese oxide) on the formation of active sites of catalysts for preferential CO oxidation (PROX) is established. A method for obtaining selective catalysts for preferential CO oxidation by integrating nanoparticles of copper, ceria, and zirconia of a certain size in a spatial-organized system, with the formation of active sites - zones of interphase interaction of copper and ceria on the surface of zirconia.
By using proposed approaches, catalysts for industrial processes of methane deep oxidation and preferential CO oxidation have been developed.
Keywords: nanophase catalyst, CO oxidation, deep methane oxidation, oxidative carbonylation of methane to acetic acid, preferential CO oxidation in hydrogen, structure, activity, selectivity, active sites.
