Yu. P. Tyulenin

The Mechanism of Methane Reforming with Carbon Dioxide: Comparison of Supported Pt and Ni (Co) Catalysts

The interaction of the catalyst 5.16 wt % Pt/α-Al2O3 with СН4, СО2, О2, and СН4 + СО2 pulses is studied using a setup involving the differential scanning calorimeter DSC–111 and a system for chromatographic analysis. Comparison of the results obtained with analogous data on Ni/Al2O3 and Co/Al2O3 suggests that methane activation occurs via a common pathway via dissociative chemisorption on the metal surface with the formation of Н2 and carbon on all the catalysts studied. Carbon dioxide activation on Pt/Al2O3 differs from its activation on Ni(Со)/Al2O3. It follows from the enthalpy of formation that carbon on Pt/Al2O3 is graphite-like in contrast to carbide carbon on Ni(Co)/Al2O3. This graphite carbon is more stable and less reactive.

Methane Reforming with Carbon Dioxide on the Co/α-Al2O3 Catalyst: The Formation, State, and Transformations of Surface Carbon

The interactions of oxidized and reduced Co/α-Al2O3 (4 wt % CoO) with H2, CH4, CO2, and O2 and their mixtures are studied in flow and pulse regimes using a setup involving a DSC-111 differential scanning calorimeter and a system for chromatographic analyses. It is shown that treatment with hydrogen at 700°C results in the partial reduction of cobalt oxide to Co. Methane poorly reacts with the oxidized catalyst but readily reacts with the reduced catalyst to form H2 and surface carbon. The initial surface carbon transforms into other forms, which block the cobalt surface to different extents and differ in the heats of reaction with CO2. Carbon dioxide may react with the surface carbon to form CO (rapidly) and with metallic Co to form CO and CoO (slowly). Thus, the main route of methane reforming with carbon dioxide on Co/α-Al2O3 is the dissociative adsorption of CH4 to form surface carbon and H2 and the reaction of surface carbon with CO2 to form CO via the reverse Boudouard reaction.

Methane Reforming with Carbon Dioxide on Cobalt-Containing Catalysts

Cobalt- and iron-containing catalysts supported on MgO, ZrO2, γ-, θ-, and α-Al2O3 were synthesized and studied in the CO2 reforming of methane. The CoO/α-Al2O3 systems are the most active and stable. The dependence of the catalytic activity and the degree of reduction on the amount of supported CoO was studied. In the active catalysts, CoO is weakly bound to the support and can readily be reduced to metal cobalt. Coke formed in the course of the reaction does not affect the activity of the CoO/α-Al2O3 catalyst.

The order of product formation in the partial oxidation of methane to syngas

The partial oxidation of methane to syngas is studied in the presence of Pt- and Ni-containing catalysts. The process kinetics does not provide unequivocal information on the order of formation of products (including carbon oxides) when either methane–oxygen or methane–oxygen–CO2 mixtures are used. Experiments with 13C-labeled carbon dioxide added show the difference in the behavior of the catalysts. In the presence of Pt/ZrO2, there is no noticeable transfer of the isotopic label to the CO molecules. On the nickel catalyst, 13CO is formed in substantial amounts, which can probably be explained by the redox reaction of 13CO2 with metallic nickel under oxygen-free conditions behind the zone of the main reaction of methane oxidation.

Formation and Conversion of Surface Compounds upon Interaction of Ethanol with Cu/CeO2 Catalyst According to in situ IR Spectroscopy

In the conditions of ethanol conversion on the surface of a 5%Cu/CeO2 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 CO2 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 CO2 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.