Laws of selective CO oxidation over a Ru/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalyst in the surface ignition regime: II. Transition states

The kinetics of selective CO oxidation (or individual CO or H₂ oxidation) over ruthenium catalysts are considerably as affected by the heat released by the reaction and specifics of the interaction of ruthenium with feed oxygen. In a reactor with reduced heat removal (a quartz reactor) under loads of ∼701 g_Cat⁻¹ h⁻¹ and reagent percentages of ∼1 vol % CO, ∼1 vol % O₂, ∼60 vol % H₂, and N₂ to the balance, the reaction can be carried out in the catalyst surface ignition regime. When catalyst temperatures are below ∼200°C, feed oxygen deactivates metallic ruthenium, the degree of deactivation being a function of temperature and treatment time. Accordingly, depending on the parameters of the experiment and the properties of the ruthenium catalyst, various scenarios of the behavior of the catalyst in selective CO oxidation are realized, including both steady and transition states: in a non-isothermal regime, a slow deactivation of the catalyst accompanied by a travel of the reaction zone through the catalyst bed along the reagent flow; activation of the catalyst; or the oscillation regime. The results of this study demonstrate that, for a strongly exothermic reaction (selective CO oxidation, or CO, or H₂ oxidation) occurring inside the catalyst bed, the specifics of the entrance of the reaction into the surface ignition regime and the effects of feed components on the catalyst activity should be taken into account.     

Synthesis and some properties of sulfur-containing iron tricarbonyl complexes

Synthesis of S₂Fe₂(CO)₆ and S₂Fe₃(CO)₉ by direct substitution of the carbonyl ligands in iron carbonyls with sulfur is described. The relative reactivities were determined for both iron carbonyls and organosulfur compounds in reactions of R₂S, R₂S₂ and RSH (R = alkyl, aryl) with Fe(CO)₅, Fe₂(CO)₉ and Fe₃(CO)₁₂. The properties of the [RSFe(CO)₃]₂ obtained are studied. New methods are found for their regeneration in the form of sulfides, disulfides and thiols.     

Polyprenols and triterpenoids from leaves of <Emphasis Type="Italic">Alcea nudiflora</Emphasis>

Polyprenols and triterpenoids from leaves of Alcea nudiflora were studied for the first time. It was shown that the principal components of the unsaponified fraction were polyprenols, sterols, a phytol, and tocopherols. The composition of the polyprenols from Alcea nudiflora was established. Minor components of polyprenols with chain lengths 8, 9, and 14 isoprene units were observed for the first time in plants of the genus Alcea. A total of 28 terpene components of the unsaponified fraction, 26 of which were not previously observed in this species, were determined by GC–MS.