The occurrence of dry reforming of methane (DRM) in a steady-state mode and partial oxidation of methane (POM) in a self-oscillating mode over a nickel foil sample and the simultaneous occurrence of these two reactions have been studied. It has been shown that during the cooccurrence of the DRM and POM reactions, a kinetic coupling of these reactions takes place; it is evident as a change in the self-oscillation period and a significant acceleration of the DRM reaction in certain phases of the self-oscillation cycle compared with the DRM rate over this Ni sample in a steady-state mode. The DRM acceleration effect is observed in a temperature range of 600–750°C. The maximum increase in the CO2 conversion value averaged over the oscillation period is a factor of 2.6 at a temperature of 700°C for a feed gas mixture composition of CH4 : CO2 = 1 : 1 + 3.5

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.

Copper-containing catalysts based on CeO2–ZrO2 solid solutions were prepared by the Pecini method and studied using a set of physicochemical methods. It was found that the bond strength of oxygen on the catalyst surface, which depends on the properties of supported copper oxide clusters and a ratio between CeO2 and ZrO2 in the support, plays a main role in ethanol conversion. Ethoxy groups, acetate and formate complexes, and condensation products were detected as main surface intermediates formed in the course of ethanol conversion on the catalysts. The decomposition of the formate complexes was the key stage in the formation of hydrogen. Its appearance on the surface of the catalysts was due to the competition between the reactions of formate and acetate complex formation for oxygen with suitable properties.

To determine the mechanism of a heterogeneous catalytic reaction, a spectrokinetic method was used based on the comparison of simultaneously measured rates of transformation of surface complexes using in situ IR spectroscopy and the rate of formation of reaction products. Based on the of systemic studies of intermediates of heterogeneous catalytic reactions by this method, general patterns are found that shed light on the essence of the catalytic action. It is found that the main function of the catalyst is the preparation of a new reagent from the molecule in the gas phase (during adsorption). The transformation of this regent into the products on the surface occurs via a route that is fundamentally different from the route of transformation of the initial molecule in a gas-phase reaction. It was also found that, if the initial adsorption forms of the reactants in the reaction under study are the same for a certain group of catalysts, then the mechanism (as a sequence of steps) of this reaction on these catalysts is the same. The individual properties of different catalysts within such a group are manifested in the difference in the ratio of the rates of steps, i.e. in determining the limiting step.

In the conditions of ethanol conversion on the surface of a 5%Cu/CeO 2 catalyst, the method of in situ IR spectroscopy reveals ethoxy groups, acetate and formiate complexes, and consolidation products. Acetaldehyde, acetone, croton aldehyde, butadiene, hydrogen, CO, and CO 2 are observed in the reaction products. As the temperature of the experiment increases, the concentration of acetaldehyde passes through a maximum at T = 250°C. This product is formed due to the interaction of ethoxy and hydroxyl surface groups. The concentration of acetone, croton aldehyde, and butadiene also passes through a maximum in the 350–400°C range. These products are associated with the decomposition of the consolidation products. The concentration of hydrogen, CO and CO 2 steadily increases with temperature and only these reaction products are left at T > 400°C. A mechanism of hydrogen formation based on the conversion of the highest temperature formiate surface complex is discussed.

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.

The IR spectra of surface compounds observed in the course of the temperature-programmed desorption (TPD) of NO x and the TPD spectra are compared. The high-temperature peaks of desorption are related to the decomposition of surface nitrites and nitrates. The low-temperature peaks of NO x desorption with maximums below 140°C are caused by the decomposition of surface nitrosyls. On the heating of surface nitrosyls, the following two reaction paths are possible: desorption at low temperatures and conversion into nitrates. The shape of the TPD spectra of NO depends on the phase composition of test samples. The transition of a tetragonal phase into a monoclinic one occurred upon the surface dehydroxylation of polycrystalline particles with the formation of particles with a tetragonal nucleus and a monoclinic crust. This transition is reversible. The cooling of a sample in a moist atmosphere leads to the transition of the monoclinic crust to the tetragonal phase.

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.

Поверхность диоксида циркония характеризуется широким набором разных по природе адсорбционных центров, соотношение между которыми можно менять в зависимости от условий приготовления и предварительной обработки образца. Отражением этого факта служит большое разнообразие поверхностных структур, образующихся при адсорбции NO и O2. В условиях протекания селективного каталитического восстановления (СКВ) NOx наиболее стабильной формой существования оксидов азота являются нитраты – продукт взаимодействия NOx с поверхностью ZrO2. Концентрации всех остальных поверхностных азот-кислородных соединений на два порядка меньше. Обсуждаются маршруты образования и разложения NO на поверхности ZrO2, в которых монодентантные нитраты (1550–1555 см-1) рассматриваются в качестве интермедиатов образования и разложения бидентантных NO .

The zirconium dioxide surface has a wide variety of adsorption sites differing in their nature. The proportions of these sites can be changed by varying the oxide preparation and pretreatment conditions. This fact shows itself as a wide diversity of surface structures resulting from NO and O2 adsorption. Under conditions of the selective catalytic reduction of NO x , the most stable nitrogen oxide species are nitrates that result from the interaction between NO x and the ZrO2 surface. The concentrations of the other nitrogen-oxygen surface compounds are two orders of magnitude lower. The routes of NO 3 − formation and decomposition on the ZrO2 surface are discussed. In these routes, monodentate nitrates (which show themselves at 1550–1555 cm−1) are considered as intermediates in the formation and decomposition of bidentate NO 3 − .

Методом ИК-спектроскопии in situ изучена реакционная способность поверхностных комплексов в условиях селективного каталитического восстановления NOх на нанесенных гетерополисоединениях. Показано, что наилучшими свойствами обладают катализаторы, носителем которых является CeO2. Обнаружено, что скорость превращения нитратных комплексов описывается уравнением нулевого порядка, как и скорость образования продуктов активации пропилена – поверхностных ацетатных и формиатных комплексов. Скорость превращения поверхностных нитратных комплексов определяется селективностью процесса окисления пропилена, которая, в свою очередь, связана с составом гетерополисоединения. Наилучшими среди изученных являются гетерополисоединения с ионами ванадия, находящимися в анионной и катионной позициях. На таких парных центрах происходит активация пропилена, продукт которой эффективно взаимодействует с нитратными комплексами.