V. F. Anufrienko

Properties and deactivation of the active sites of an MoZSM-5 catalyst for methane dehydroaromatization : Electron microscopic and EPR studies

The MoZSM-5 (4.0 wt % Mo) catalyst has been characterized by high-resolution transmission electron microscopy, EDXA, and EPR. Two types of molybdenum-containing particles are stabilized in the catalyst in the course of nonoxidative methane conversion at 750°C. These are 2-to 10-nm molybdenum carbide particles on the zeolite surface and clusters smaller than 1 nm in zeolite channels. According to EPR data, these clusters contain the oxidized molybdenum form Mo5+. The surface Mo2C particles are deactivated at the early stages of the reaction because of graphite condensation on their surface. Methane is mainly activated on oxidized molybdenum clusters located in the open molecular pores of the zeolite. The catalyst is deactivated after the 420-min-long operation because of coke buildup on the zeolite surface and in the zeolite pores.

Electron spectroscopic studies of copper in catalysts for methanol synthesis

The state of Cu2+ ions in Cu−Zn−Al catalysts for methanol synthesis has been studied by electron spectroscopy (5000–50000 cm−1). It has been established that low-temperature ZnO stabilizes copper in a distorted octahedral coordination as cluster structures resembling (but not similar to) CuO. The presence of Al promotes the formation of these clusters and inhibits the formation of CuO.AbstractВ работе методом электронной спектроскопии (5000–50000 см−1) изучено состояние ионов Cu2+ в Cu−Zn−Al катализаторе синтеэа метанола. Показано, что низкотемпературный ZnO стабилизирует медь в искаженно октаэдрической координации в виде кластерных структур, приближающихся (но не равных) к CuO. Присутствие алюминия способствует образованию таких кластеров, и препятствует образованию CuO.

Diffuse reflectance electron spectroscopic study of the state of silver clusters on SiO2

After treating supported, highly dispersed silver catalysts with a solution of HNO3, silver particles characterized by a band at 320 nm have been isolated. These particles are presamably <1 nm silver clusters, which are insoluble in HNO3 but are oxidized in air.AbstractС помощью обработки раствором HNO3 нанесенных высокодисперсных серебряных катализаторов выделены частицы серебра, характеризующиеся полосой поглощения 320 нм. По мнению авторов, этими частицами являются серебряные кластеры размером менее 1 нм, обладающие свойством не растворяться в HNO3, но окисляться на воздухе.

The state of Cu2+ ions in concentrated aqueous ammonia solutions of copper nitrate

Stabilization of Cu2+ ions in concentrated aqueous ammonia solutions of copper nitrate in a wide range of ammonium ion concentrations has been studied by EPR and electronic absorption spectroscopy. Three types of Cu2+ associates with different types of orbital ordering have been identified. The ammonium ion concentration in a solution has a decisive effect on the type of orbital ordering of Cu2+ ions in associates. In all cases, Cu2+ ordering in associates is caused by the existence of bridging OH groups in the axial and equatorial positions of [Cu(NH3)n(H2O)6 − n]2+ complexes (n < 6). At a high concentration of ammonium ions, weakly bound associates of tetramminecopper with the

The Structure of Oxide Ga–Sb–Ni–P–W–O/SiO2 Catalyst and Its Catalytic Properties in Propane Ammoxidation

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Structure peculiarities of reduced vanadium-titanium oxide catalysts

ground state are formed. In solutions with low ammonium concentrations, bulky associates with the

ESR study of ordered Ti(III) clusters in frozen solutions

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