Valerii A. Matyshak

Cu, Co, Ag-Containing Pillared Clays as Catalysts for the Selective Reduction of NOx by Hydrocarbons in an Excess of Oxygen

Thermally stable Al- and Zr-PILC loaded with copper and cobalt cations and silver nanoparticles were synthesized. The structural and surface features of these nanosystems were studied and compared with those of bulk analogs – partially stabilized ZrO2 loaded with the same active components. Specificity of the catalytic properties of nanocomposites in SCR of NOx by propane, propylene and decane in the excess of oxygen appears to be determined both by distribution of active components on the catalytic surface and degree of their interaction with supports. Formation of ads.-NOx, nitroxyl-hydrocarbon CxHyNO2⋅ and isocyanate NCO intermediates was observed by ESR and IR spectroscopy in situ.

IR studies of the transformations of nitrogen-containing organic intermediates during selective reduction of nitrogen oxides by hydrocarbons

Thermal transformations of nitromethane and deuterated acetonitrile adsorbed on the surface of H-ZSM-5, Cu-ZSM-5, Co-ZSM-5 has been studied by IR spectroscopy. The nature of cation has been found to greatly affect the transformation pathways of these species as possible intermediates in the NOx selective reduction by hydrocarbons, thus explaining the different selectivities of these catalysts.

Nanocomposites Based Upon Alumina and Zirconia Pillared Clays Loaded with Transition Metal Cations and Clusters of Precious Metals: Synthesis, Properties and Catalysis of NO x Selective Reduction by Hydrocarbons

Thermally stable alumina and zirconia pillared clays loaded with copper and cobalt cations and silver nanoparticles were synthesized. The structural and surface features of these nanosystems were studied and compared with those of bulk analogs -partially stabilized zirconias and γ-alumina loaded with the same active components. Specificity of the catalytic properties of nanocomposites in the reactions of nitrogen oxides reduction by propane, propylene and decane in the excess of oxygen appears to be determined both by the degree of interaction between pillars and active components and the type of reducing agent.

Reaction paths of the formation and consumption of nitroorganic complex intermediates in the selective catalytic reduction of nitrogen oxides with propylene on zirconium dioxide according to in situ fourier transform IR spectroscopic data

Nitrate, acetate, and nitroorganic complexes were detected on the surface of ZrO2 under the reaction conditions of nitrogen oxide reduction with propylene using Fourier transform IR spectroscopy. The nitroorganic complex was formed in the reaction between acetate and nitrate complexes by the replacement of the carboxyl group in the acetate complex by the nitro group. Monodentate nitrate was the most reactive species in this process. The adsorption of various nitroorganic substances was studied. It was found that the nitroorganic complex was structurally analogous to the nitromethane molecule bound to the surface through the nitro group. The experimental data led us to a conclusion that nitroorganic compounds were subsequently consumed in reactions with nitrate complexes. In this surface reaction, monodentate nitrate was also the most reactive species. The presence of oxygen had no effect on the consumption of the nitroorganic complex.

Reaction paths of the formation and consumption of nitroorganic complex intermediates in the selective catalytic reduction of nitrogen oxides with propylene on zirconia-pillared clays according to in situ spectroscopic data

It was found that the adsorption and catalytic properties of nanosized ZrO2 particles as the pillar constituents of ZrO2-pillared clay and bulk ZrO2 are essentially different. The interaction of NO with the surface of bulk ZrO2 resulted in the formation of three types of nitrate complexes. Only two nitrate species were formed on ZrO2-pillared clay (the monodentate species was absent). Only an acetate complex was formed in the interaction of a mixture of propylene and oxygen with the surface of bulk ZrO2, whereas an isopropoxide complex was the main propylene activation species on ZrO2-pillared clay. On the surface of ZrO2-pillared clay, isopropoxide and nitrate intermediates formed a complex structurally similar to adsorbed dinitropropane. On the surface of bulk ZrO2, acetate and monodentate nitrate complexes formed a complex structurally similar to adsorbed nitromethane. The dinitropropane complex on ZrO2-pillared clay was consumed in reactions with surface nitrates. The decomposition reaction of a dinitropropane compound with the formation of acetate complexes and ammonia predominated on the surface containing no nitrate complexes in the absence of NO + O2 from a gas phase. The found differences in reactant activation species and their thermal stabilities explained differences in the activities of bulk ZrO2 and nanosized ZrO2 particles as pillars in pillared clay in the course of the selective catalytic reduction of nitrogen oxides with propylene in an excess of oxygen.

Nanoscale Structural Features of Ultra-fine Zirconia Powders Obtained Via Precipitation-hydrothermal Treatment Route

Genesis of the structure of zirconia fine particles prepared by precipitation of amorphous hydrated zirconia by ammonia from the ZrO(NO 3 ) 2 solution followed by a mild hydrothermal treatment (HTT) of precipitate, washing and calcination under air up to 1000 °C has been studied by HRTEM, X-ray diffraction, Raman and FTIRS. HTT rearranges the structure of amorphous zirconia, which helps to obtain nearly single-phase monoclinic nanozirconia (particle size 5-15 nm) after a mild calcination at 500 °C. Dehydroxilation and sintering of these nanoparticles at higher (600-650 °C) temperatures generate polysynthetic (001) twins. Modeling revealed that reappearance of the (111) “cubic” reflex in XRD patterns of samples calcined at 600-650 °C can be due to these extended defects. In their vicinity, the seven-fold Zr-O coordination sphere is retained, while packing of ZrO 7 polyhedra is varied towards more symmetric structures, thus causing disappearance of the Raman spectra.

HYDROCARBON SPECIFICITY IN THE SELECTIVE CATALYTIC REDUCTION OF NOX OVER CU-ZSM-5 AND CO-ZSM-5 CATALYSTS

Transformation of surface nitrates under CH4 (CH4+O2) was found to ensure steady-state activity of Co-ZSM-5 in the selective catalytic reduction of nitrogen oxides by methane (CH4-SCR). For Cu-ZSM-5, such species are mainly converted into NO. Relaxation of the coordination sphere due to oxygen and NO adsorption, stability of C,N-containing intermediates and activation routes of hydrocarbons (methane, propane) were analyzed as factors determining catalytic properties of Cu and Co cations.

Effect of the modification of ZrO2-containing pillared clay with Pt and Cu atoms on the properties of inorganic complex intermediates in the selective catalytic reduction of nitrogen oxides with propylene according to in situ IR-spectroscopic data

It was found that only bridging and bidentate nitrate complexes were formed on the surface of Pt,Cu/ZrO2-pillared interlayered clay (ZrO2-PILC) upon the interaction with a flow of the (0.2% NO + 2.5% O2)/N2 mixture, whereas monodentate and nitrosyl complexes were not detected. The concentration of nitrate complexes on Pt,CU/ZrO2-PILC was higher and the strength of their bond to the surface was weaker than those on unmodified ZrO2-PILC. Isopropoxide and acetate complexes and coordinatively bound acetone were formed on the surface in the interaction of Pt,Cu/ZrO2-PILC with a flow of the (0.2% C3H6 + 2.5% O2)/N2 mixture. The supporting of Pt and Cu onto zirconium dioxide pillars resulted in considerable changes in the concentration and the temperature region of the existence of hydrocarbon surface compounds, as compared with ZrO2-PILC. Under reaction conditions at relatively low temperatures, isopropoxide and nitrate intermediates on the surface of Pt,Cu/ZrO2-PILC formed a complex structurally similar to adsorbed dinitropropane. At elevated temperatures, a surface nitromethane complex was formed in the interaction of the acetate complex with nitrate species. The spectrokinetic measurements demonstrated that the apparent rate constants of consumption of nitrate and nitroorganic complexes considerably increased on going from ZrO2-PILC to Pt,Cu/ZrO2-PILC. Moreover, the constants of consumption of nitroorganic and nitrate complexes were similar for both of the catalysts. This fact suggests that, on the test catalysts, nitroorganic complexes were reaction intermediates in the selective catalytic reduction of NOx (NOx SCR) with hydrocarbons. The found differences in the activation species and thermal stabilities of reactants can explain different activities of ZrO2-PILC and Pt,Cu/ZrO2-PILC in the SCR reaction of NOx with propylene in an excess of oxygen.

Reactivity and transformation routes of surface nitrates in the reaction of NOx reduction by C3H8 over cation-exchanged zeolites

FITRS combined with15N and18O isotope substitution and TPD have revealed that nitrates are the most abundant ad-NOx species on over-exchanged Cu- and Co-ZSM-5 zeolites. the transformation rates of such species under the action of a propane—oxygen mixture were found to be comparable and sufficiently high to afford steady-state catalytic activities. A scheme of the reaction mechanism including C, N-containing intermediates detected in work is suggested.

Synergistic Effect in Selective Reduction of NO by Alkanes over Mechanically Mixed Oxide Catalysts

The process of selective catalytic reduction of nitrogen oxides by propane in the presence of O2, as well as in the presence or absence of CO, was studied over series of commercial oxide catalysts used in petrochemical processes. For the first time synergistic effect was observed for catalytic systems consisting of mechanical mixtures of Cu–Zn–Ni–Al (catalyst I) + Fe–Cr (catalyst II) and Cu–Zn–Ni–Al (catalyst I) + Ni–Cr (catalyst III). The activity of these mixtures in nitrogen oxides reduction by propane was greater than that of individual components in each case. The worked-out catalytical systems showed high effectivity in the process of simultaneous removal of several toxic components: NOx, CO, hydrocarbons – from model gas mixtures, as well as from real exhausts of automotive transport.