E. P. Belanova

Oxidative processing of light alkanes: State-of-the-art and prospects

Recent literature data on partial oxidation of light alkanes into syngas and oxidative coupling of methane into C2 hydrocarbons are reviewed. The problems of these processes (high cost of pure oxygen; safety; activity, selectivity and stability of catalysts; temperature regime; coke formation and other by-products; insufficient level of methane transformation into ethane and ethylene) are considered. Possible solutions of these problems and prospects of practical use of light alkanes processing are discussed.

Conversion of hydrocarbons to synthesis gas: Problems and prospects

The problems of synthesis gas manufacture in relation to the thermochemical characteristics of the interaction of hydrocarbons with various oxidants (H2O, CO2, O2), coke formation, and catalyst deactivation are considered. Prospects for the partial oxidation of hydrocarbons have been discussed in light of recent developments in the field of oxygen-permeable membrane materials. Data on oxide systems containing active lattice oxygen are presented, which opens the possibility of manufacturing synthesis gas from hydrocarbon mixtures, in particular, from associated gas.

Oxidative dehydrogenation of ethane to ethylene in a system with circulating microspherical metal oxide oxygen carrier: 1. Synthesis and study of the catalytic system

By screening a large series of oxide systems, the most effective modified Mo catalysts for oxidative dehydrogenation of ethane to ethylene with selectivity for the desired product of more than 90% have been found. Using TG–DTA and XRD techniques, it has been shown that the state of the support (Al2O3) determines the formation of active sites. The procedure for preparing microspherical Mo catalysts is characterized by simplicity and complete reproducibility of their properties. Further investigation in this line is associated with testing a pilot batch of the Mo catalyst on a pilot unit with a riser reactor.

Ethane conversion involving lattice oxygen of oxide systems

A large set (60 samples) of oxide systems containing Mo, V, Ti, Zr, Fe, Ni, Co, La, Ce, Al, Si, Sb, Bi, Nb, Sn, and Pb oxides has been obtained by synthesis. It has been found that using Al(OH)3 (instead of Al2O3) makes it possible to prepare a modified Mo system that ensures a 93–95% selectivity of ethane dehydrogenation to ethylene with a C2H6 conversion as high as 40%. These results open the possibility of purposeful and technologically easy manufacturing of molded systems containing active lattice oxygen, which is able to mediate the oxidative dehydrogenation of ethane to ethylene.

Thermal transformations in systems based on zeolites Y, X, and A containing zinc and sodium nitrates

Thermal transformations in systems formed by interaction of Zn and Na nitrates with Y, X, and A zeolites were studied by TG—DTA technique. Temperature regions of existence of adsorbed water, water of crystallization, and decomposition of NO3– anion were determined. These intervals depend on the composition, structure, method of preparation, and pre-treatment conditions of zeolite systems. The extent of NO3– decomposition depends not only on the zinc and sodium content but also on the presence of ammonia involved in NO3– reduction. The zeolite matrix strongly stabilizes the occluded NO3– anions. A portion of zinc oxide formed by zinc nitrate decomposition is probably localized inside the zeolite cavities as the [Zn—O—(ZnO)n—Zn]2+ particles. The latter compensate charges of the isolated [AlO4]– tetrahedra.

Thermal and structural properties of molybdenum systems modified with aluminum, gallium, or yttrium oxide

Oxide systems prepared by thermal decomposition of mixtures of ammonium heptamolybdate with varying amounts of aluminum, gallium, and yttrium nitrates have been studied by thermal analysis, X-ray powder diffraction, and scanning electron microscopy. The formation processes, the nature of interaction between the components, and the states of these systems have been determined. It was shown that the nature of oxides in the molybdenum systems have a significant effect on their physicochemical properties.

Oxidative conversion of ethane involving lattice oxygen of molybdenum systems modified with aluminum, gallium, or yttrium oxide

Oxidative conversion of ethane on the molybdenum oxide MoO3 mixed with 0–95% Al2O3, Ga2O3, or Y2O3 has been studied in the pulse mode at 600°C. It has been revealed that the components of these systems undergo strong interaction, which leads to enhanced ethane conversion and an increased selectivity for ethylene with a decrease in the MoO3 content. The 5%MoO3–95%Al2O3 system has proved the most effective in the oxidative dehydrogenation of ethane, with the selectivity for ethylene reaching 90% at an ethane conversion of 30 wt %.

Catalytic transformations of mixtures of ethers with aliphatic and aromatic nitriles on solid acids under supercritical conditions

The catalytic conversion of mixtures of ethers with aliphatic and aromatic nitriles in supercritical conditions on zeolites (HY, HCaREEY), individual oxides (Al2O3, SiO2, MoO3, WO3, TiO2), and oxide systems (Al2O3-SiO2, H8[Si(Mo2O7)5], Al2(WO4)3) has been studied. It has been found that acid catalysts, such as zeolites, mixed oxides, and TiO2 (anatase), are active at 350°C in the direct synthesis of N-acylpyrrolidines from tetrahydrofuran and nitriles (CH3CN, n-C4H9CN, C6H5CN): the product yield reaches 40% and the selectivity is 65–94%. The activity and selectivity of TiO2 samples increase with an increase in the specific surface area (from 37 to 139 m2/g) or with a decrease in the particle size of anatase (from 43 to 13 nm according to XRD data). The character of interaction of the components of the reaction mixture with the TiO2 surface has been studied by the TG-DTA technique. After oxidative regeneration, TiO2 exhibits the initial catalytic properties, suggesting the possibility of its repeated use in the direct synthesis of acylpyrrolidines. Replacing THF by other compounds (diethyl ether, 1,4-dioxane, tetrahydropyran) drastically reduces the yield of respective alkylamides.