N. Ya. Usachev

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.

Partial oxidation of lower alkanes by active lattice oxygen of metal oxide systems: 1. Experimental methods and equipment

Processes for manufacturing synthesis gas, one of the most important high-volume products of gas chemistry, have been briefly surveyed. Trends in the development of catalysts and technologies used in the process have been shown. One of the most promising in terms of engineering design, cost, and safety is that based on the oxidative conversion of lower alkanes into synthesis gas with a circulating microspherical heterogeneous metal oxide contact. Experimental methods and devices for studying heterogeneous contacts and designing the process technology have been proposed. By the example of microspherical Ni-Co metal oxide heterogeneous contact, it has been shown that the proposed methods and setups provide extensive information and are useful for studying synthesis gas manufacturing in a system with separate feedstock and oxidant supply to the reaction and regeneration zones, respectively.

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.

Partial oxidation of lower alkanes by active lattice oxygen of metal oxide systems: 2. Synthesis of solid contacts and syngas production in a pilot plant with a riser reactor

Metal oxide systems with a high lattice-oxygen content, which exhibit reversibility of oxidationreduction transitions, have been synthesized and characterized. Oxidant Solid Contacts have been prepared using these systems as active components. The features of methane interaction with a circulating microspherical solid contact in a flow-through riser reactor have been revealed. The effect of temperature and hydrocarbon residence time in the reactor on the performance of the process has been examined. Optimal conditions for the manufacturing of synthesis gas have been determined, at which the methane conversion reaches 95–99% and the H2/CO ratio in the product is in the range of 2.0–2.2.

Manganese catalysts for the oxidative condensation of methane with alkali and alkaline-earth metal salt additives

Conclusions1.The addition of acetates of alkali (Li, Na, K, and Cs) and alkaline-earth (Mg and Ca) metals affects the catalytic properties of Mn/SiO2 catalysts in the oxidation condensation of methane to give C2-hydrocarbons.2.The promotion effect of sodium salts depends on the nature of the salt anion. Greatest efficiency is found for the (Mn + NaCl)/SiO2 catalyst. At 800°C and methane/air mole ratio equal to 0.55, C2-hydrocarbons are formed on this catalyst with 25.8% yield and 77.5% selectivity; the ethylene content in the methane condensation products is 95%.

Oxidative condensation of methane into ethane and ethylene on manganese catalysts

Conclusions1.Manganese catalysts based on zeolites and silica gel are efficient in oxidative condensation of methane into ethylene and ethane.2.Conversion of CH4 attains 25.6% with 51.9% selectivity for C2 hydrocarbons on the most active catalyst, 10% Mn/HNaHSZ at 750°C.

A study of polyfunctional zeolite catalysts. Communication 7. Catalytic properties of metal-M1+NaX zeolite systems in the hydrocondensation of butyraldehyde

Conclusions1.Butyraldehyde and hydrogen are converted to 2-ethylhexanal and 2-ethyl-1-hexanol on systems containing and metal (Pt, Pd, Rh, Ni, and Co) and zeolite M1+NaX (M1+=Na+, K+, and Rb+) at atmospheric pressure and 100–200°C. This finding confirms the bifunctional catalytic effect of these systems.2.The Pd/M1+NaX systems displays the greatest selectivity of the catalysts studied in the one-step synthesis of 2-ethylhexanal from butyraldehyde and H2.