季铵盐固相催化使聚氯乙烯脱HCl

通过将季铵盐与聚氯乙烯(PVC)混溶成膜,使其在固相脱HCl,研究了催化剂对PVC脱HCl反应速度和产物结构的影响以及固相反应与温度、时间的关系.发现在催化性能上下基铵盐比乙基铵盐好得多,根据实验结果提出了季铵盐通过分解成叔胺实现催化的机理.     

Controlled synthesis of stable poly(vinyl formamide-co-vinyl amine)/silica hybrid particles by interfacial post-cross-linking reactions

 The chemical synthesis and the physicochemical properties of stable poly(vinyl formamide-co-vinyl amine)/silica hybrid particles are presented. Copolymers of poly(vinyl formamide) (PVFA) and poly(vinyl amine) (PVAm) and their protonated forms were adsorbed onto silica from aqueous solutions. The influences of the pH strength and the ion concentration of the aqueous solution as well as the copolymer composition (degree of hydrolyzation of PVFA), and the molecular mass on the adsorption process were investigated by electrokinetic measurements, potentiometric titration, and quantitative elemental analyses. Silica surface-charge neutralization is achieved at a pH strength above 10 for highly hydrolyzed (95%) PVFA polymers. Decreasing the amino content in the PVAm chain shifts successively both the point of zero charge and the isoelectric point to lower pH values. PVFA-co-PVAm layers onto silica are adsorbed weakly. To fix these layers irreversibly, cross-linking reactions with (4,4′-diisocyanate)diphenyl methane were carried out on the surface of solid PVFA-co-PVAm/silica hybrid particles suspended in acetone. The cross-linking reaction, which is connected with the conversion of amino groups, is also a tool to control the surface charge of the PVFA-co-PVAm/silica hybrids. X-ray photoelectron spectroscopy and solid-state ¹³C cross-polarization magic-angle spinning NMR spectroscopy were used to obtain information on the number of and the structure of the functionalized polyelectrolyte layers on silica. The success of cross-linking was also shown by the results of these spectroscopic methods. Received: 28 June 1999 /Accepted: 27 August 1999     

Effects of the Calcination and Reduction Conditions on a Cu/ZnO Methanol Synthesis Catalyst

The CuO crystallite size of the catalysts obtained from aurichalcite greatly depends on the heating rate of calcination for highly active and selective Cu/ZnO catalyst was prepared by reduction with methanol at 443 K for 17 h.     

Electron density distribution in the crystal of the Meisenheimer complex of potassium 3-methyl-5′, 7′-dinitro-5′, 8′-dihydrospiro(1,3-oxazolidine-2,8′-quinolinide) based on X-ray diffraction data at 153 K

The electron density distribution in the crystal of the Meisenheimer complex of potassium 3-methyl-5′, 7′-dinitro-5′, 8′-dihydrospiro(1,3-oxazolidine-2,8′- quinolinide) (1) was studied based on the data of precision X-ray diffraction study. The experimental data were compared with the results of quantum-mechanical calculations. The electron density distributions in the regions of the nitro groups are substantially different in spite of the similarity in the geometric parameters of these groups. In addition, there is a discrepancy between the exprimental and theoretical data on this distribution. The effect of the cation on the electronic strucure of the anion in the crystalline phase is the most probable cause of the differences observed. To reveal this effect.ab initio calculations of different anion1-K⁺ systems were performed and a topological analysis of the electron density distributions was carried out. Depending on the mode of coordination of the cation to the anion, the former determines the contribution of alternative resonance forms to the structure of the anion. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 451–458, March, 2000.     

Electrodialytic separation of potassium ions from sodium ions in the presence of crown ether using a cation-exchange membrane

The separation of potassium and sodium ions from their mixture was performed by electrodialyzing a mixed solution of potassium chloride and sodium chloride in the presence of 18-crown-6 using a commercial cation-exchange membrane. After 18-crown-6 had been impregnated in the membrane, the mixed solution containing 18-crown-6 was electrodialyzed as the desalting-side solution. The permeation of potassium ions through the membrane decreased remarkably and the electrical resistance of the membrane increased during electrodialysis with increasing concentration of 18-crown-6 in the solution. Because potassium ions form a more stable complex with 18-crown-6 than sodium ions and because the complex permeated through the membrane with difficulty, sodium ions are thought to selectively permeate through the membrane. The current efficiency in electrodialysis was greater than 97.0%. Received: 1 June 1999/Accepted in revised form: 13 August 1999     

Separation of alkylbenzyl quaternary ammonium compounds by capillary zone electrophoresis with sample stacking injection

Summary A systematic investigation of operational buffer systems, sample preparation and instrument parameters for achieving the best possible performance for determinating an homologous series of N-benzyl-N-alkyl-N,N-dimethylammonium chloride compounds by capillary zone electrophoresis with direct UV detection. The most effective separation was achieved within 3.5 min with the addition of acetonitrile (40%) in a phosphate buffer (20 mM pH 5.2) using a 40 cm fused-silica capillary operating at 25 KV and 20°C. Degassing of all electrolyte solutions and samples was very important. The linearity and repeatability for each compounds were satisfactory. To improve detection limits, on-column sample preconcentration, sample stacking, was investigated achieving a tenfold enrichment factor and quantitation limits about 10⁻⁷M.     

Chemistry of 2-substituted benzimidazoles. 1. 5-Amino-2-methyl(aryl, arylalkyl, pyridyl)benzimidazoles

A series of 2-substituted benzimidazoles was synthesized. These products were consecutively converted into 5-nitro- and 5-amino-2-substituted benzimidazoles.Russian People's Friendship University, 117198 Moscow. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 493–500, April, 200.     

Diagramme Polythermique Du Systeme Ternaire KCl–FeCl2–H2O Entre 0 Et 70°C

Polytherm diagram of the ternary system KCl–FeCl₂ –H₂ O between 0 and 70°C. Phase equilibria in the KCl–FeCl₂ –H₂ O system were studied over the temperature range 0–70°C by conductimetric and analytical methods. A solubility polytherm of the system was constructed. We have observed the crystallization fields of the KCl and FeCl₂ 6H₂ O (at 0°C), KCl and FeCl₂ 4H₂ O (at 15, 30 and 40°C) and KCl, FeCl₂ 4H₂ O and of a double salt KClFeCl₂ 2H₂ O are obtained at 70°C. This revised version was published online in July 2006 with corrections to the Cover Date.     

Estimation of diffusion coefficient of Ba++ ions in silica gel from periodic precipitation of BaMoO4

Formation of Liesegang rings on the growth of BaMoO₄ crystals in silica gel by single diffusion is discussed. The rhythmic precipitation is found to be influenced profoundly by (a) the molarity of inner and outerelectrolytes (b) the age of gel and (c) the pH of the gel medium. The time law, spacing law and the law relating diffusion depth and width are verified. A method to estimate the diffusion coefficient of the outer electrolyte in the gel medium is developed and calculated for Ba⁺⁺ions.     

Immobilized plant cells

Plant cells have been immobilized in alginate, where they have been shown to retain their biological activity. Such systems can be utilized for bioconversions.