Pavel G. Tsyrulnikov

Nanocomposites on the basis of layered silicates as the catalysts for the dehydrogenation of methanol

The methanol dehydrogenation reaction has been studied over impregnated copper-containing catalysts. A silica-montmorillonite nanocomposite has been used as the support for these systems. The catalyst’s features were found to depend strongly on the distance of the interlayer spacing within the structure of montmorillonite. The textural changes taking place in the support affect the accessibility of the active sites of the catalyst for methanol. The optimal temperature of the reductive pretreatment in hydrogen atmosphere required for the preparation of an active and durable enough nanocomposite-based catalyst was found to be 300°C.

Enhanced Adsorption Properties of Ag-Loaded β-Zeolite towards Toluene

Two series of Ag-loaded β-zeolites with silica/alumina ratio of 25 and 36 were prepared by ion exchange technique. The silver loading was varied in a range of 2-10 wt%. The samples were characterized by low-temperature nitrogen adsorption, Infrared and UV-vis spectroscopy, and transmission electron microscopy. Adsorption/desorption properties of zeolites were examined using a specially designed setup. Toluene was used as a model hydrocarbon. It was found that adsorption capacity of zeolites grows up along with silver content increase till 8%, and reduces then. According to data of physicochemical methods, at low loading the silver exists in cluster and ionic forms, while at high loading agglomerated particles predominate, which worsens the adsorption properties.

High-Temperature X-Ray Diffraction Investigation of the Decomposition Process in Manganese-Gallium Spinel Mn1.5Ga1.5O4

The stability of spinel-type mixed Mn1.5Ga1.5O4 oxide prepared in an inert medium (1000 °C, Ar) is studied by thermogravimetry and high-temperature X-ray diffraction in air in a wide temperature range 30–1000 °C. On heating, reversible decomposition processes of initial spinel are observed. From 30 °C to 600 °C oxygen atoms attach to the surface layer of initial Mn1.5Ga1.5O4 spinel to form a new phase distinct from parent oxide by the oxygen stoichiometry (cation vacancies are formed). The product of decomposition is two oxides: Mn1.5Ga1.5O4 and Mn1.5–xGa1.5–x[·]xO4. On the contrary, above 600 °C a loss of oxygen occurs, the concentration of cation vacancies decreases in Mn1.5–xGa1.5–x[·]xO4, and the reverse process of single phase oxide crystallization takes place. At 1000 °C the spinel phase forms again whose composition is similar to that of the initial parent phase Mn1.5Ga1.5O4. On cooling the decomposition of this phase is again observed due to oxygen attachment.