The paper compares the properties and activity of palladium clusters deposited on aluminum oxides of different phase compositions obtained by different methods. The numbers of palladium atoms available for the adsorption of hydrazine were determined for each catalyst. A correlation was found between the number of such atoms and the rate of hydrogen formation in the decomposition reaction of hydrazine monohydrate. It was concluded that an active palladium catalyst for the decomposition of hydrazine can be obtained using a modified support with a large specific surface area. The specific surface area and its modification determined the surface coverage with the active reagent. Obviously, the study of the role of various properties of supports in the formation of the active phase should be continued.

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.

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.

Pd-containing catalysts (1% Pd/Al 2 O 3 and 5% Pd/Al 2 O 3 ) supported on aluminum oxide were studied in the decomposition reaction of hydrazine monohydrate. According to in situ IR-spectroscopic data, hydrazine monohydrate was adsorbed in a linear form on the coordinatively unsaturated sites of the catalyst surface. As the temperature was increased, the adsorbed hydrazine monohydrate lost a water molecule with a change in the geometry of the molecular complex. The adsorption of hydrazine on a support and its diffusion onto palladium clusters is a more advantageous process than direct adsorption on active sites. This circumstance shows that the hydrazine adsorbed on the support can be an intermediate in the process of its decomposition. The test catalysts had a maximum activity at a temperature of about 100°C. At temperatures in a range of 100−120°C, the ratio between hydrogen and nitrogen concentrations in the reaction products was 2, which corresponds to 100% selectivity for hydrogen. The selectivity decreased significantly with the reaction temperature. The high selectivity for hydrogen at low temperatures was explained by the fact that N 2 H 4 was chemisorbed 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 N−H bond breaking barrier is lower than the N−N bond breaking barrier, and this fact led to the breaking of an N–H bond and the preservation of an N–N bond. At elevated temperatures, some of the formed hydrogen atoms recombined, and the other reacted with the surface complexes of hydrazine to form the intermediate NH 3 −NH 3 , in which N–N bond breaking led to the appearance 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.

Oxidation of dibenzothiophene (DBT) is used as the model reaction in studying the process of catalytic oxidative desulfurization of diesel fuel. The method of oxidative desulfurization includes the stage of oxidation of thiophene compounds contained in the fuel into the corresponding thiophenesulfones, followed by their extraction from the reaction mixture with a polar liquid. In this paper, we study the oxidation reaction of DBT into DBT sulfone in a solution in octane, with atmospheric oxygen in the presence of benzaldehyde at room temperature and irradiation of the reaction mixture with ultraviolet (UV) light. It is shown that in this case a DBT conversion of 97 to 98% can be achieved without using a catalyst. It is also found that UV irradiation of the reaction mixture can be carried out periodically (in pulses of a duration of 1 min), which makes it possible to exclude overhearing reaction mixture.

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.