Pd-containing catalysts (1%Pd/Al2O3 and 5%Pd/Al2O3) deposited on aluminum oxide were studied in the decomposition reaction of hydrazine monohydrate. According to in situ IR spectroscopy, it was found that hydrazine monohydrate is adsorbed on the coordination unsaturated centers of the catalyst surface in a linear form. When the temperature rises, the adsorbed hydrazine monohydrate loses a water molecule, which is accompanied by a change in the geometry of the molecular complex. Adsorption of hydrazine on a support and its diffusion onto palladium clusters is a more advantageous process than direct adsorption on active centers. This circumstance shows that the hydrazine adsorbed on the support can be an intermediate of its decomposition process. The studied catalysts have a maximum activity in the temperature range of 100–120°C, while the ratio of hydrogen and nitrogen concentrations in the reaction products was equal to 2, which corresponds to 100% selectivity for hydrogen. As the reaction temperature increases, the selectivity decreases significantly. The explanation of the high selectivity for hydrogen at low temperatures is due to the fact that the adsorption of N2H4 is carried out through the formation of hydrogen–metal bonds. The hydrogen–metal bond strength in such a complex is higher than the nitrogen–metal bond strength, hence the barrier for breaking the N–H bond is lower than the barrier for breaking N–N bond, which leads to breaking N–H bond and preserving the N–N bond. At elevated temperatures, some of the hydrogen atoms formed recombine, the other reacts with the surface complexes of hydrazine to form the intermediate NH3–NH3, the breaking of the bond in which leads to the formation of ammonia molecules in the gas phase.

Samples of (0.5–15)%CoO/CeO2, Co3O4, and CeO2 have been studied in the oxidation of CO to CO2 in a CO+O2+H2 mixture in a range of 40–340°C. The highest activity in CO oxidation is exhibited by 10%CoO/CeO2 with a characteristic conversion of CO to CO2 of γ50 = 50% at Т50 ≈ 140°С and γ ≈ 100% at Т = 180–220°С. The СО2 yield decreases at 220–240°C due to competition for oxygen in the CO and H2 oxidation reactions; at Т > 240°C, it decreases due to the consumption of CO in the methanation reaction. According to XRD and H2-TPR, cobalt oxide in the 10%CoO/CeO2 sample is present in two forms of a highly dispersed Co3O4 oxide (CoxOy clusters) interacting with the support and in the form of a Co3O4 phase. Carbon monoxide oxidation in a range of 60–180°C occurs on CoxOy clusters. Under these conditions, the activity of particles of the Co3O4 phase in pure oxide and the 10%CoO/CeO2 catalyst is lower than that of the clusters. The effect of the properties of adsorption complexes formed involving the oxygen contained in the clusters and in the gas phase on the temperature dependence of CO conversion has been studied.

The 5% CuO/Ce1 – xPrxOy catalysts were synthesized on the basis of CeO2 and PrO2 oxides and Ce1 – xPrxOy solid solutions with x = 0.2, 0.5, and 0.8. Highly dispersed copper oxide was present in the 5%CuO/Ce1 – xPrxOy catalysts. Upon interaction with the support, it formed active oxygen, which participated in CO chemisorption and a low-temperature reaction of CO oxidation in the presence of hydrogen. The highest conversion of CO in an excess of H2 (γmах(Т)), which was close to 100%, was obtained at temperatures of 120–160°C on a 5% CuO/CeO2 catalyst. Upon the modification of CeO2 with Pr cations, 5% Ce0.2Pr0.8Oy sample, it decreased to 65% at 220°C due to an increase in the bond strength of oxygen in copper-containing centers. A maximum conversion of CO (93%) on a sample of 5% CuO/PrOy was detected at 200°C. Upon the modification of PrO2 with Ce cations, the activity of 5% CuO/Ce0.5Pr0.5Oy and 5% CuO/Ce0.2Pr0.8Oy catalysts did not exceed that of 5% CuO/PrOy. The forms of CO and CO2 adsorption on 5% CuO/Ce1 – xPrxOy samples were studied using the TPD method. In a range of 170–500°C, the desorption of oxygen from the supports of 5% CuO/Ce0.5Pr0.5Oy and 5% CuO/PrOy samples was observed. The occurrence of the reaction on 5% CuO/Ce1 – xPrxOy catalysts was discussed. With consideration for the properties of CO complexes formed on copper-containing oxidation and adsorption centers, their participation in the reaction of low-temperature oxidation in hydrogen was examined.

The (5–15)%CoO/ZrO2(T + M) catalysts were studied by XRD and TPR-H2. In the oxidized samples, 80–90% of cobalt oxide is present in the form of finely dispersed Co3O4, which interacts with the support ( $${\text{Co}}_{x}^{{3 + }}{\text{Co}}_{y}^{{2 + }}{\text{O}}_{z}^{{2 - }}$$ clusters), and the rest of it (10–20%) are the Co3O4 phase and dispersed CoO. In the CO oxidation to CO2, the most active samples were CoO/ZrO2(T + M) containing 10 and 15% cobalt at T50 = 120°C. Nearly 100% conversion of CO to CO2 was observed on 10%CoO/ZrO2(T + M) at 160–200°C. The conversion decreases at 220–260°C as a result of competition for oxygen in the oxidations of CO and H2, and at 280–360°C, as a result of increased consumption of CO in the methanation reaction. The CO oxidation in the range 50–200°C occurs on the clusters localized on the ZrO2(T) particles. The Co3O4 phase in pure oxide and in the 5%CoO/(SiO2, ZrO2(M)) catalysts has low activity under these conditions. The temperature dependence of CO conversion was discussed based on the data on the properties of adsorption complexes formed with participation of oxygen clusters and the gas phase.

We theoretically and experimentally examined the assumption that the lifetime excited state of Fe2+ in ZnSe:Fe crystal is quenched by free electrons. The effect of the electron beam current value on the temporal characteristics of the luminescence was studied. Three variants, including a sample in the electronic circuit in the case of Fe2+ ions luminescence excitation in a ZnSe:Fe crystal by a beam of accelerated electrons, were first considered theoretically. These variants differ in external electric field magnitude in the sample, which affects the concentration of free electrons in the excited region of the sample. Equations describing the time dependence of the sample's electron density were derived. The luminescence decay kinetics of Fe2+ ions in ZnSe:Fe crystal excited by electron pulse with different electron beam current values and short-pulse optical radiation were obtained. The values of the quantities that determine the temporal characteristics of the luminescence decay depending on the electron beam current were found.

The article reports the synthesis of 5%CuO/Ce1– xZrxO2 catalysts based on CeO2, ZrO2 oxides and Ce1– xZrxO2 solid solutions with х = 0.2, 0.5, and 0.8. It is found that copper oxide is present in the catalysts in a highly dispersed form. In strong interaction with supports, it forms active oxygen, which participates in CO chemisorption and low-temperature oxidation of CO in the presence of hydrogen. In selective CO oxidation, the highest conversion (γmах = 100%) was obtained at temperatures of 120–160°С in the presence of 5%CuO/CeO2. In the modification of CeO2 by zirconium cations, the conversion on 5%Ce0.5Zr0.5O2 decreases to 92% at 160°С because oxygen binding strengthens on copper-containing sites. On the 5%CuO/ZrO2 sample, the maximum conversion is 67% at 180°С. The modification of ZrO2 by cerium cations leads to an increase in the conversion to 87% at 160°С on the 5%CuO/Ce0.2Zr0.8O2 sample as a result of increasing the amount of oxygen vacancies in the support. Taking into account the properties of CO complexes formed on copper-containing oxidation and adsorption sites, and the interaction of these complexes with adsorbed oxygen, their participation in the reaction of low-temperature CO oxidation by oxygen in excess of hydrogen on 5%CuO/CeO2 and 5%CuO/ZrO2 catalysts is considered.

The dependence of the activity of СuO/ZrO2 catalysts in the CO oxidation reaction with oxygen in the presence of an excess of hydrogen and adsorption of СО over them on the CuO content (0.5 to 15%) and the structure of the support ZrO2, monoclinic (М), tetragonal (Т), or mixed (М + Т) has been studied. It has been found that the activity of CuO/ZrO2 is associated with the adsorption capacity of the samples for СО at 20°С. Thus, 5%CuO/ZrO2(Т + М) and 5% CuO/ZrO2(Т) samples, which exhibit the maximum activity (the СО conversion over them is 80–85% at 160°С), also possess a high chemisorption capacity towards CO (~2.2 × 1020 molecules/g). At the same time, CuO/ZrO2(М) samples with the CuO contents of 1 and 5% do not chemisorb СО and are inactive in the reaction at 160°С. The СО conversion over them does not exceed 32–36% at 250°С. On the basis of the data obtained by X-ray phase analysis, temperature-programmed reduction with Н2, temperature-programmed СО desorption, and electron paramagnetic resonance, a conclusion has been made that at low temperatures СО oxidation proceeds over CunOm clusters that are located on ZrO2(Т) crystallites. With the increase in the copper oxide content from 0.5 to 5%, the activity of the clusters increases, while the reaction temperature decreases. CuOm oxo complexes and particles of the СuO phase do not exhibit catalytic activity. The reasons for the low activity of the CuO/ZrO2(М) samples with the CuO contents of 1 and 5% in the СО oxidation and adsorption processes are discussed. The mechanism of the low-temperature СО oxidation with oxygen in an excess of hydrogen over a 5% CuO/ZrO2(Т + М) catalyst is considered.

It has been demonstrated by quantitative spectrokinetic measurements that, on the surface of zirconia stabilized as a tetragonal phase, the rate-limiting step of the selective catalytic reduction of nitrogen oxides (SCR of NO x ) with propylene is the interaction of surface nitrates with C3H6 yielding organic nitro compounds. It is hypothesized that propylene reacts not with the nitrates themselves but with the activated complex NO2 ads whose structure is intermediate between the structures of the monodentate NO3 − and NO2 species. Deep C3H6 oxidation exerts an adverse effect on the rate of the SCR of NO x with propylene, and the interaction between O2 and NO, which yields NO2 and NO3 − stimulates further nitrogen reduction to N2. The effect of the reaction between oxygen and O2N−C n H m on the NO x reduction rate is variable and is determined by the C3H6/NO x ratio. A generalized scheme of the SCR of NO x with propylene on the surface of ZrO2 partially stabilized as a tetragonal phase has been developed by comparing experimental data of this study and data available from the literature.

CO adsorption on (0.5–15)%CoO/ZrО 2 catalysts has been investigated by temperature-programmed desorption and IR spectroscopy. At 20°С, carbon monoxide forms carbonyl and monodentate carbonate complexes on Co m 2+ O n 2- clusters located on the surface of crystallites of tetragonal ZrO 2 . With an increasing CoO content of the clusters, the amount of these complexes increases and the temperature of carbonate decomposition, accompanied by CO 2 desorption, decreases from 400 to 304°С. On the 5%CoO/ZrО 2 sample, the carbonyls formed on the Со 2+ and Со + cations and Со 0 atoms decompose at 20, 90, and 200–220°С, respectively, releasing CO. At 20°С, they are oxidized by oxygen to monodentate carbonates, which decompose at 180°С. Adsorbed oxygen decreases the temperature of their decomposition on oxidation sites by ~40°C, and the sample remains in an oxidized state ensuring the possibility of subsequent CO adsorption and oxidation. The rate of the oxidation of 5%CoO/ZrО 2 containing adsorbed CO by oxygen is higher than the rate of the oxidation of the same sample reduced by carbon monoxide, because the latter reaction is an activated one. In view of the properties of the complexes, it can be concluded that the carbonates decomposing at 180°С are involved in CO oxidation by oxygen from the gas phase in the presence of hydrogen, a process occurring at 50–200°С. The rate-limiting step of this process the decomposition of the carbonates, which is characterized by an activation energy of 77–94 kJ/mol.

The CO adsorption species on Co 3 O 4 and (0.5-15%)CoO/CeO 2 catalysts have been investigated by temperature-programmed desorption and IR spectroscopy. At 20°C, the largest amount of CO is adsorbed on the 5%CoO/CeO 2 sample to form, on Co m 2+ O n 2+ clusters, hydrogen-containing, bidentate, and monodentate carbonate complexes, whose decomposition is accompanied by CO 2 desorption at 300 and 450°C (1.1 × 10 20 g –1 ). The formation of the carbonates is accompanied by the formation of Co + cations and Co 0 , on which carbonyls form. The latter decompose at 20, 90, and 170°C to release CO (2.7 × 10 19 g –1 ). Part of the carbonyls oxidizes to CO 2 upon oxygen adsorption, and the CO 2 undergoes desorption at 20°C. Adsorbed oxygen decreases the decomposition temperature of the H-containing and bidentate carbonates from 300 to 100-170°C and maintains the sample in the oxidized state, which is active in subsequent CO adsorption and oxidation. CO oxidation by oxygen of the catalyst diminishes the activity of the sample in these processes and increases the decomposition temperature of the carbonate complexes. Taking into account the properties of the adsorption complexes, we concluded that the H-containing and bidentate carbonates are involved in CO oxidation by oxygen of the catalyst at ~170°C under isothermal conditions. The rate limiting step is the decomposition of the carbonates, a process whose activation energy is 65-74 kJ/mol.

The adsorption of reactant mixtures is quantitatively and qualitatively different from the adsorption of the individual reactants. Thus, O 2 is almost not adsorbed on ZrO 2 ; however, a considerable concentration of molecular oxygen was detected among the products of desorption after the adsorption of a mixture of NO + O 2 and the total amount of desorbed molecules was greater by a factor of 10 than their total amount after the individual adsorption of NO and O 2 . Among the qualitative differences is the formation of the O 2 - radical anion on the surface only upon the adsorption of the mixture of NO + O 2 . Similarly, the number of desorbed molecules upon the simultaneous adsorption of C 3 H 6 , NO, and O 2 was much greater than that upon their individual adsorption; this is related to the formation of paramagnetic and nonparamagnetic NO 2 –hydrocarbon complexes on the surface, which contained the NO 2 group and a hydrocarbon fragment.

With the use of the temperature-programmed desorption of CO and IR spectroscopy, it was found that, after the adsorption of carbon monoxide on the oxidized 5% CuO/CeO2, 5% CuO/ZrO2, 5% CuO/Al2O3, and 5% CuO/SiO2 samples at 20°C, the greatest amount of adsorbed molecules (2.5 × 1020 g−1) was present on 5% CuO/ZrO2. Of these molecules, 1.0 × 1020 and 1.4 × 1020 g−1 formed carbonyl and carbonate adsorption complexes with the participation of copper-containing sites, respectively. The oxidized sample of 5% CuO/ZrO2 contained only the oxidation sites Cu2+O2−, which participated in the formation of carbonates upon the adsorption of CO. A portion of Cu2+ cations was reduced to Cu+ in the course of reaction, and two types of the carbonyl complexes Cu+CO were formed on them. They were characterized by the presence of absorption bands at 2110 and 2107 cm−1 in the IR spectrum and decomposed with the desorption of CO at 100 and 170°C. Carbonyls were oxidized by adsorbed oxygen at 20°C to carbonates. The temperature of their decomposition accompanied by the desorption of CO2 (T max = 170°C) was lower than that of carbonates (240 and 350°C) formed upon the adsorption of CO on the oxidized surface in the absence of oxygen from a gas phase. The properties of adsorption complexes and their participation in the reaction CO + O2 → CO2 at low temperatures, in particular, with the use of a hydrogen-containing mixture, were considered. The oxidation of CO on CuO clusters in 5% CuO/CeO2 and 5% CuO/ZrO2 were discussed.