Acetonitrile - 2-Methyl-Propan-1-ol and Acetonitrile - 2-Methyl-Propan-2-ol Binary Mixtures and their Physicochemical Properties

The 1 H-NMR spectra of liquid binary mixtures of acetonitrile with 2-methyl-propan-1-ol (i-BtOH) and 2-methyl-propan-2-ol (t-BtOH), were recorded at 298 K over almost the whole range of mixed solvent compositions. From these data the values of spectral parameters, j i (ACN-i-BtOH) and j i (ACN-t-BtOH) were found. The relative permittivities ( k 12 ) and the densities ( d 12 ) of the mixed solvents were measured at 288.15 K, 293.15 K, 298.15 K, 303.15 K and 308.15 K. The experimental data were used to test some empirical equations of the type: y 12 = y 12 ( t ) and y 12 = y 12 ( X 1 ) [where: y 12 = d 12 or k 12 ]. From all these data, the deviations from ideality molar volumes , temperature coefficients of relative permittivities ( f 12 ) and the excess extrathermodynamic parameters were calculated. The values of these structural parameters are discussed in terms of interactions of acetonitrile with both alcohols.     

Physicochemical Methods Used to Study Internal Structures of Liquid Binary Mixtures

Abstract

Different methods, based on application of studies of intensive physicochemical properties of liquid binary mixtures and ¹H-NMR spectral measurements, used in the analysis of intermolecular interactions and estimation of the internal structure of these mixtures and here reviewed.     

New hydrofluoropolyethers II: Physico-chemical characterization

We obtained, through an original multi step synthetic approach with 60-80% selectivity, a novel family of hydrofluoropolyethers (HFPEs) characterized by a macromeric perfluoropolyether (PFPE) body end-capped, on one or both sides, by a 1,1-difluoroethoxy group. We synthesized these HFPEs trough an apparently conventional hydrogenation of PFPE precursors end-capped by reducible acyl halide groups and subsequent Cl cleavage by hydrogen, promoted by UV light in presence of hydrogen radical donor or by a metal catalytic system in presence of H₂. The physico-chemical properties of these HFPEs were described and compared to those of similar perfluorinated or partially hydrogenated molecules, obtaining master curves of general validity when temperature dependent properties, like viscosity, were compared under temperature reduced condition. The contribution of the end-groups to the specific property, vanishing at a sufficient high molecular weight, was demonstrated more and more important at the lowest oligomerization degrees.     

Inverse gas chromatography applications: A review

Inverse gas chromatography (IGC) is a versatile, powerful, sensitive and relatively fast technique for characterizing the physicochemical properties of materials. Due to its applicability in determining surface properties of solids in any form such as films, fibres and powders of both crystalline and amorphous structures, IGC became a popular technique for surface characterization, used extensively soon after its development. One of the most appealing features of IGC that led to its popularity among analytical scientists in early years was its similarity in principle to analytical gas chromatography (GC). The main aspect which distinguishes IGC experiments from conventional GC is the role of mobile and stationary phases. Contrary to conventional GC, the material under investigation is placed in the chromatographic column and a known probe vapour is used to provide information on the surface.     

Tailoring materials by high-energy ball milling: TiO2 mixtures for catalyst support application

We carried out a rational design of catalyst supports by high-energy ball milling. Tailored mixtures of TiO₂ crystalline phases were obtained using rotational speed and milling time as variable parameters. Polymorphic transformation from anatase to rutile through high-pressure TiO₂ (II) as intermediate was confirmed by X-ray Diffraction (XRD), Raman Spectroscopy and Transmission Electron Microscopy (TEM). Also, starting material doubled its specific surface area due to particle fragmentation, as confirmed by surface area of Brunauer-Emmet-Teller (S_BET) and Scanning Electron Microscopy (SEM). Defects introduced during milling process generated oxygen vacancies in the surface and bulk of supports, as evidenced by X-ray Photoelectron Spectroscopy (XPS) and Electron Paramagnetic Resonance (EPR). Furthermore, longer milling time increased reducibility and oxygen mobility of supports, as observed by H₂ Temperature Programmed Reduction (H₂-TPR) and O₂ Temperature Programmed Desorption (O₂-TPD). Phase composition remained unchanged even under extreme conditions, highlighting the stability of unusual TiO₂ (II) phase. Properties achieved in present materials could benefit metal-support interactions and play a major role in supported catalysts.     

The Effect of Styrene-Butadiene-Styrene Modification on the Characteristics and Performance of Bitumen

Summary. In order to cover the effect of styrene-butadiene-styrene (SBS) modification on the characteristics of bitumen, two types of bitumen, one plain bitumen, and one polymer modified bitumen produced with the plain bitumen as base material were characterized in terms of chemical composition, microstructure, micromechanical properties, and thermoanalytical behavior. In order to determine the complex chemical composition of bitumen, elemental analysis, gel permeation chromatography, and the Iatroscan method were employed. Microstructure and micromechanical properties were determined using an environmental scanning electron microscope and the nanoindentation technique. Modulated differential scanning calorimetry was used to determine phase-change temperatures and endo/exotherms associated with molecular movement. The addition of SBS leads to different rheological behavior over the whole service temperature range. This is reflected in bitumen chemistry by differences in elemental composition and molecular weight distribution with much higher M _w values for the modified bitumen. Accordingly, the polymer leads to a shift in molecular fractions. Electron microscopy reveals two distinct phases building up the bitumen microstructure. The chosen mode of quantification leads to similar material parameters for both bitumens, which is explained by the use of the same base material. In contrast, nanoindentation delivers viscosities in the micro-range corresponding to large-scale rheological properties. Modulated differential scanning calorimetry indicates two glass transitions corresponding with two material phases also confirmed by other experiments. Due to modification, these glass transitions depart from each other and the amount of the two material phases changes, correlating with the shift in molecular fractions observed in Iatroscan analyses.     

Structure and surface properties of praseodymium modified alumina

Mixed PrO₂-Al₂O₃ oxides with different PrO₂ content (1-20 wt.%) were prepared by wetness impregnation of γ-alumina with aqueous solution of praseodymium nitrate. The samples were characterized by different techniques, using surface adsorption-desorption of N₂ (S_BET), thermogravimetric analysis (TGA), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectroscopy (DRS), temperature-programmed reduction (TPR) and temperature-programmed desorption of CO₂ (TPD-CO₂). TGA and XRD showed the presence of small praseodymium oxide species on the alumina surface. XPS and DRS detected electron deficient interaction between deposited praseodymium oxide and alumina. It was observed a lower reduction temperature for supported Pr oxide species compared to that of the bulk Pr₆O₁₁. TPD-CO₂ studies suggested that the deposition of Pr oxide on alumina leaded to increase of the basicity of mixed oxides.