Popovych N. Effect of the composition of metal-oxide Ag/Al2O3/cordierite and zeolite Ag/BEA catalysts on their activity and selectivity in the process of nitrogen oxides reduction with C2, C4 alcohols

The thesis is devoted to studying the influence of the composition of metal-oxide Ag/Al2O3/cordierite and zeolite Ag/BEA catalysts on their physicochemical characteristics (surface morphology, oxidation state of active components, redox and acid-base surface properties) and catalytic properties in selective reduction of NO with C2,C4-alcohols and to development of highly active and selective structured catalysts for this process. It is shown that higher activity of silver-alumina catalysts in selective reduction of NO with C2,C4-alcohols in oxygen excess is achieved at silver loading of 0.06-0.22 mg/m2 and caused by silver localization mainly in the state of cations and subnanoclusters - the active sites of the studied process. Amount of silver nanoparticles (Ag0) increases at higher silver loading in the catalyst (above 0.22 mg/m2), which leads to the deep oxidation of reductant by oxygen without NO reduction. Increasing of alumina loading up to 45-50 wt.% in Ag/Al2O3/cordierite leads to higher catalytic activity (lower temperature of 95-100% NO conversion) due to the increase in the total concentration of Lewis acid sites - centers of reagents activation in SCR-process. Developed method for deposition of mesoporous Al2O3 on the surface of cordierite honeycomb matrix allows the preparation of highly active and selective to N2 structured Ag/Al2O3/cordierite catalysts. Selective reduction of NO with C2,C4-alcohols in oxygen excess on zeolite Ag/BEA catalysts occurs in wider temperature range compared to dealuminated zeolites, due to the higher concentration of strong Lewis acid sites, on which stabilized nitrite-nitrate adducts react with reductant activated on silver active sites. Promotion effect of hydrogen in SCR of NO with C2,C4-alcohols on Ag-containing catalysts is caused by the presence of strong Lewis acid sites and silver subnanoclusters on the catalyst surface.