Andrey Simakov

Investigation of the state of copper in supported copper–titanium oxide catalysts

Supported copper–titanium oxide catalysts have been studied by IR spectroscopy, XRD, UV–VIS diffuse reflectance spectroscopy, ESR, TPR with hydrogen and EXAFS. Different states of Cu2+ ions have been found on the surface of TiO2. The ratio between these states depends on the copper concentration and catalyst preparation method. Chain structures are formed due to the interaction of Cu2+ ions with TiO2. Their concentration and geometry of their nearest oxygen environment are determined by the structure of anatase faces. Some of these surface-stabilized Cu2+ ions are nucleation centers of oxide clusters. A noticeable growth of bulk CuO phase is observed after the completion of the formation of chain structures and oxide clusters. A quantitative estimation of the concentration of these copper forms in the catalysts is reported. For supported copper–titanium oxide catalysts, chain forms of Cu2+ ions are shown to be the most active forms of copper in NO SCR with ammonia and methane oxidation.

Selective catalytic oxidation of ammonia to nitrogen

The activity of catalysts of different nature in ammonia partial oxidation has been studied. Vanadium-titanium, copper-titanium catalysts and copper-substituted zeolites are the most active in the reaction. These catalysts are promising if used as honeycomb monoliths.

Relationship between sulfur dioxide oxidation and selective catalytic NO reduction by ammonia on V2O5−TiO2 catalysts doped with WO3 and Nb2O5

The performance of V2O5−TiO2 catalysts doped by WO3 and Nb2O5 in sulfur dioxide oxidation, and in selective catalytic reduction (SCR) of NO by ammonia has been studied. Addition of tungsten and niobium oxides was found to suppresses sulfur dioxide oxidation thus increasing the catalysts resistance to SO2 poisoning and their activity in SCR.

Propane and oxygen action on NOx adspecies on low-exchanged Cu-ZSM-5

A surface intermediate with a C/N ratio close to 3 has been shown by TPD to form at co-adsorption of NO and propane as well as NO, propane and O2 on low-exchanged Cu-ZSM-5. The adsorption of NO, propane and oxygen has been studied to evaluate their effect on the formation of this complex. Its formation is accompanied by a decrease in the concentration of surface nitrite–nitrate. The kinetics of nitrite–nitrate adspecies formation as a function of the reagents concentration and temperature has been investigated. Some NO adspecies have been found to decompose yielding N2O.

Effect of the nature of titania on the activity of Cu−Ti−O catalysts for selective catalytic reduction of nitrogen oxides with ammonia

The activity of Cu−Ti oxide catalysts has been studied in the selective catalytic reduction of NO with ammonia. We have elucidated how the nature ofstarting titania affects the catalyst activity in this reaction.

Support effect for nanosized Au catalysts in hydrogen production from formic acid decomposition

Catalysts with about 2.5 wt% of gold supported on Al2O3, ZrO2, CeO2, La2O3 and MgO oxides and with the same mean metal particle sizes of 2.4–3.0 nm have been studied in hydrogen production via formic acid decomposition. A strong volcano-type relation of the catalytic activity on the electronegativity of the supports cation was demonstrated with the Au/Al2O3 catalyst on the top. This indicated that the activity is affected by the acid–base properties of the support. A study of the most active Au/Al2O3 catalyst with aberration-corrected HAADF/STEM, XPS and EXAFS proved that gold is in metallic state. The content of single supported gold atoms/cations was negligible. Therefore, the mechanism of the reaction was related to the activation of formic acid on the catalysts support followed by further decomposition of the formed reaction intermediate on the Au/support interface.

Effect of parent titanium oxide on the physico-chemical properties of Cu−Ti oxide catalysts

Physico-chemical properties of Cu−Ti oxide catalysts have been studied. The effect of parent titanium dioxide properties (specific surface, preparation procedures) on the state of Cu ions on the anatase surfaces has been revealed.

Dinitrogen formation over low-exchanged Cu-ZSM-5 in the selective reduction of NO by propane

The role of gaseous NO and C3H8 has been studied over low-exchanged Cu-ZSM-5 zeolite employing TPD, FTIR and pulse technique with the alternate introduction of NO or C3H8 onto the catalyst surface. The rate of the N2 formation is directly proportional to the content of gaseous NO and the surface coverage with 2-nitrosopropane. There was no formation of N2 during interaction of gaseous C3H8 with NO adsorbates. However, 2-nitrosopropane and its isomer acetone oxime were also formed in this reaction.

Aerobic Oxidative Esterification of Benzyl Alcohol and Acetaldehyde over Gold Supported on Nanostructured Ceria–Alumina Mixed Oxides

Au nanoparticles supported on nanostructured ceria‐alumina mixed oxides (10 and 30 wt % ceria) were prepared by a deposition–precipitation method. Their properties were studied by N2 adsorption, XRD, TEM, X‐ray photoelectron spectroscopy, and UV/Vis spectroscopy under temperature‐programmed reduction or oxidation. The materials catalyzed the liquid‐phase aerobic oxidative esterification of benzyl alcohol and benzaldehyde effectively and showed a much better performance than Au supported on the individual oxides. The reactions occurred with high turnover numbers (up to 19 000) in methanol solutions in the absence of any auxiliary base and gave mainly methyl benzoate. The strong synergetic effect of ceria and alumina can be explained by the enhanced oxygen storage capacity of the materials prepared from mixed oxides compared to that of pure alumina and ceria. The order of the catalytic activity (Au/Al2O3

Rate-determining stage in NO SCR with propane on low-exchanged Cu-ZSM-5 catalyst

The kinetics of the NO SCR with propane has been studied on a low‐exchanged Cu‐ZSM‐5 catalyst. The study of the kinetics of individual reaction stages (2‐nitrosopropane isomerization to acetone oxime and reaction of adsorbed acetone oxime with gaseous NO) has shown that the NO reaction with acetone oxime is the rate‐determining stage in the whole chain of transformations leading to the formation of molecular nitrogen in the low‐temperature region below 300 °C. The kinetic analysis of the reaction has revealed that at the temperatures above 300 °C propane plays a more important role.