Search results for "Alkali metal"

The Influence of Alkali Metal Ions in the Chemisorption of CO and CO2on Supported Palladium Catalysts: A Fourier Transform Infrared Spectroscopic Stu…

1996

Two series of palladium-based catalysts were compared on the basis of the adsorption of CO and CO2, monitored by Fourier transform infrared spectroscopy. The first series is represented by a silica-supported palladium catalyst and by some catalysts derived from it by addition of different amounts of sodium ion, 0 ≤ R ≤ 25.6, whereRis the atomic ratio Na/Pd. The second series consists of palladium catalysts supported on “model” and natural pumices. The model pumices, obtained by sol-gel techniques, are silico-aluminates containing variable amounts of sodium so that the corresponding Pd catalysts have anRvalue in the range 0 ≤ R ≤ 6.1. In the Pd/natural pumice catalysts, changes of the atomic…

Sodium-mediated manganation: direct mono- and dimanganation of benzene and synthesis of a transition-metal inverse-crown complex.

2007

Inside out approach: Twofold deprotonation of benzene by a sodium monoalkyl bisamido manganate(II) reagent derived from BuNa, 2,2,6,6-tetramethylpiperidine, and Mn(CH2SiMe3)2 has produced the first inverse-crown complex in which the transition-metal atoms are incorporated in the host (see X-ray structure, blue N, green Na, purple Mn). Variable-temperature magnetization measurements show that the complex is antiferromagnetic.

An Inorganic Double Helix Sheathing Alkali Metal Cations: ANb2P2S12(A=K, Rb, Cs), A Series of Thiophosphates Close to the Metal-Nonmetal Boundary-Cha…

2004

The new quaternary niobium thiophosphates ANb 2 P 2 S 1 2 (A=K, Rb, Cs) have been prepared and characterized. The title compounds were synthesized by reacting Nb metal, A 2 S, P 2 S 5 , and S at 600-700°C in evacuated silica tubes. They crystallize as "stuffed" variants of the tetragonal TaPS 6 structure type in the tetragonal space group I42d with eight formula units per unit cell and lattice constants a=15.923(2) and c=13.238(3) A for CsNb 2 P 2 S 1 2 , a= 15.887(3) and c=13.132(3) A for RbNb 2 P 2 S 1 2 , and a=15.850(2) and c= 13.119(3) A for KNb 2 P 2 S 1 2 . Their structures are based on double helices formed from interpenetrating, noninteracting spiral chains of binuclear [Nb 2 S 1 2…

1982

The polyamides 3–5 were synthesized from α,ω-diamino-substituted oligo(oxyethylene)s (1) and bis-chlorides of dicarboxylic acids (2). As copolymers with defined sequences they contain up to five oxyethylene units per repeating unit. Hereby properties like solubility, thermal stability and complexing ability towards alkali metal cations are influenced.

ChemInform Abstract: Modular Metal Chalcogenide Chemistry: Secondary Building Blocks as a Basis of the Silicate-Type Framework Structure of CsLiU(PS4…

2012

The new title compound is synthesized from a mixture of U, P2S5, Li2S, Cs2S, and S in the molar ratio 2:2:1:1:4 (sealed silica tube, 700 °C, 3 d).

Sodium Congener of the Classical Lithium Methylchromate Dimer: Synthetic, X-ray Crystallographic, and Magnetic Studies of Me8Cr2[Na(OEt2)]4

2011

One of the milestone structures in the development of transition-metal complexes with metal metal bonds of multiple bond order was the lithium methylchromate dimer Me8Cr2[Li(donor)](4) (donor = THF or Et2O). Using a simple salt metathesis reaction mixing this compound with sodium tert-butoxide, the sodium congener Me8Cr2-[Na(OEt2)]4 has been synthesized as a green crystalline compound and isolated in 51% yield. Its solid-state structure was determined by single-crystal X-ray diffraction. Exhibiting exact crystallographic C-4h symmetry, this heavier alkali-metal chromate structure is also dimeric, formally comprising a (Me8Cr4)(4-) tetranionic core with four peripheral Na+ cations carrying s…

Self-trapped exciton formation through photo-induced recombination of F and H centers in alkali iodides

1997

The photo-induced conversion of the primary F, H center pairs into self-trapped excitons have been proposed and studied in alkali iodides.

Trapping of laser-vaporized alkali metal atoms in rare-gas matrices

1999

Abstract Alkali metal atoms prepared by laser ablation of solid Li and Na are trapped in Ar, Kr, and Xe matrices and studied by electron paramagnetic resonance spectroscopy (EPR) at 15 K. Evidence for tight trapping sites, not observed for atoms generated by conventional Knudsen oven techniques, is presented. The novel tight trapping sites are characterized by a large increase in the isotropic hyperfine coupling constant and a simultaneous decrease in the isotropic g -value. Based on the EPR data, it is suggested that the observed tight trapping corresponds to single substitution of lattice atoms in Ar, Kr, and Xe matrices.

Formation of self-trapped excitons through stimulated recombination of radiation-induced primary defects in alkali halides

1998

Abstract A self-trapped exciton formation through photostimulated recombination of an F and an H center — the exciton-created primary defect pair, is proposed and experimentally examined in alkali halides at low temperatures.

Alkali consumption of aliphatic carboxylic acids during alkaline pulping of wood and nonwood feedstocks

2013

Abstract The carbohydrate degradation products have been examined, which are formed during the conventional kraft pulping of a softwood, hardwoods, bamboo, and wheat straw as well as soda and soda-anthraquinone pulping of wheat straw. The focus was on “volatile” acids such as formic and acetic acids and “nonvolatile” hydroxy monocarboxylic and dicarboxylic acids. The different consumption profiles were obtained for the charged alkali required for the neutralization of these aliphatic acids depending on the feedstock and the cooking method. The relative composition of the acid fraction in the black liquors of softwood and hardwood and nonwood feedstocks showed characteristic variations. Howe…