A cooling process for an NaA type zeolite used in systems to purify argon of oxygen

Translated from Khimicheskoe i Neftyanoe Mashinostroenie, No. 11, pp. 16–17, November, 1992.     

Mathematical modeling of the motion of an air suspension taking into account nonequilibrium melting (crystallization)

Within the framework of the mechanics of heterogeneous media undergoing phase transformations, we propose a mathematical model for describing the flow of a mixture of gas and liquid (solid) metal particles. We consider the difference between the velocities and temperatures of the phases and the nonequilibrium nature of the phase transition. As an example, we solve the problem of the structure of a shock wave in an air suspension of melting particles. We isolate the conditions determining the monotonic and nonmonotonic temperature behavior of the mixture. We present numerical data illustrating the determined types of motion of the gas suspension.Institute of Theoretical and Applied Mechanics, Siberian Branch, Russian Academy of Sciences, Novosibirsk 630090. Translated from Fizika Goreniya i Vzryva, Vol. 30, No. 4, pp. 91–99, July–August, 1994.     

Phase relations in the HgCr2Se4-CdCl2 system

The phase relations in the HgCr₂Se₄-CdCl₂ system have been investigated using differential thermal analysis and x-ray diffraction, and the primary crystallization field of the spinel phase in this system has been located: 560–750°C, 84–97 mol % CdCl₂. By optimizing growth conditions and using CdCl₂ as a flux, single crystals of Hg_1?x Cd_xCr₂Se₄ solid solutions containing up to 5 wt % Cd have been grown.     

Thermally Stable, Latent Olefin Metathesis Catalysts

Highly thermally stable N-aryl,N-alkyl N-heterocyclic carbene (NHC) ruthenium catalysts were designed and synthesized for latent olefin metathesis. These catalysts showed excellent latent behavior toward metathesis reactions, whereby the complexes were inactive at ambient temperature and initiated at elevated temperatures, a challenging property to achieve with second generation catalysts. A sterically hindered N-tert-butyl substituent on the NHC ligand of the ruthenium complex was found to induce latent behavior toward cross-metathesis reactions, and exchange of the chloride ligands for iodide ligands was necessary to attain latent behavior during ring-opening metathesis polymerization (ROMP). Iodide-based catalysts showed no reactivity toward ROMP of norbornene-derived monomers at 25 °C, and upon heating to 85 °C gave complete conversion of monomer to polymer in less than 2 hours. All of the complexes were very stable to air, moisture, and elevated temperatures up to at least 90 °C, and exhibited a long catalyst lifetime in solution at elevated temperatures.