Some Thermoelectric Phenomena in Copper Chalcogenides Replaced by Lithium and Sodium Alkaline Metals

This review presents thermoelectric phenomena in copper chalcogenides substituted with sodium and lithium alkali metals. The results for other modern thermoelectric materials are presented for comparison. The results of the study of the crystal structure and phase transitions in the ternary systems Na-Cu-S and Li-Cu-S are presented. The main synthesis methods of nanocrystalline copper chalcogenides and its alloys are presented, as well as electrical, thermodynamic, thermal, and thermoelectric properties and practical application. The features of mixed electron–ionic conductors are discussed. In particular, in semiconductor superionic copper chalcogenides, the presence of a “liquid-like phase” inside a “solid” lattice interferes with the normal propagation of phonons; therefore, superionic copper chalcogenides have low lattice thermal conductivity, and this is a favorable factor for the formation of high thermoelectric efficiency in them.

Efficient Adsorbent-Desiccant Based on Aluminium Oxide

The review describes the main methods of obtaining hydroxides and aluminium oxides (AO) of various structures from gibbsite. The promising techniques of obtaining AO adsorbents are discussed, namely the technique of thermal activation in the mode of pneumatic transport with gibbsite by heated air (TCA Gb) and the technique of thermal activation of gibbsite in centrifugal flash reactors (CTA Gb). The main methods of improving the adsorbent properties of AO, such as the optimisation of texture characteristics and phase composition, as well as the influence of the modification of aluminium oxide adsorbents, obtained using CTA and TCA technologies with cations of alkaline metals, are considered. It is shown that the modification allows a controlled variation of the characteristics of donor and acceptor active sites on the surface of adsorbents and, thus, a substantial increase in their adsorption activity, in particular, with respect to water vapour.

Current Aspects of Prevention of Coal Freezing by Means of Inorganic and Organic Reagents

In the cold season, irregular coal supplies to coke plants are aggravated by the need to heat the coal cars. Thawing of rail cars in garages (enclosures) is the least efficient and most expensive approach. Treatment of the coal concentrates with chemical additives reliably prevents freezing in winter during transit from suppliers to consumers. With a view to finding new reagents for preventing the freezing of coal in winter, the lime, the acetates and chlorides of alkaline-earth and alkaline metals are studied. Attention focuses on their physicochemical characteristics, methods of preparation and of introduction in coal concentrate, and their influence on freezing. The results of studies have shown that the use of organosilicon is more effective use of acetates and chlorides of metals. The high activity of organosilicon substances is explained by their elemental composition and structure of molecules.

New Dimensions of Brønsted Base Catalyzed Carbon–Carbon Bond-Forming Reactions

Catalytic carbon–carbon bond-forming reactions of weakly acidic carbon pronucleophiles (pK a in DMSO ≥30) were developed using strong alkaline metal Brønsted bases as catalysts. Not only weakly acidic amides, esters, nitriles, sulfonamides without any activating group, and alkyl azaarenes, but also alkyl arenes such as toluene, were applicable for the reactions, which are difficult to be applied in typical Brønsted base catalyzed reactions. Expansion to enantioselective reactions was also revealed to be possible. The reactions are atom economical and require only inexpensive alkaline metals rather than precious transition metals.1 Introduction2 Catalytic Direct-Type Addition Reactions of Weakly Acidic Carbonyl and Related Pronucleophiles3 Catalytic Direct-Type Addition Reactions of Alkyl Azaarenes4 Catalytic Direct-Type Addition Reactions of Alkyl Arenes5 Conclusion

Basicity determination of SBA-15 doped with different alkaline metals through CO2 adsorption and isopropanol decomposition

In order to increase the activity and selectivity towards to light olefins in the Fischer-Tropsch synthesis, new support for the role of iron (Fe) are presented. Thus, SBA-15 was synthetized and doped with different alkaline metals preserving the structural characteristics of the mesoporous solid. The samples were characterized by X-ray diffraction at low angles, N2 adsorption, atomic absorption spectroscopy, CO2 desorption at programmed temperature and isopropanol test. The alkaline metals (Li, K and Cs) introduction into the channels of the solid, generate basic sites of different strength that are not present in the SBA-15 without doping and do not produce significant changes in the structural and textural properties of the SBA-15, only a densification in the walls of the channels is evidenced. According to the alkaline metal used and through CO2 adsorption and isopropanol decomposition, it was possible to established the order by the total number of sites: Li >> K » Cs, and the force order for both types of sites (weak and intermediate): Li > Cs > K.