Band 60, Heft 5

The effect of γ-irradiation on the structure and oxidation of cis-1,4-polyisoprene is investigated by ATR-FTIR technique. This method provides the valuable insight into the type of oxidation products produced and the extent and nature of intramolecular cyclization and chain scission reactions. The formation of ketones, alcohols and/or ethers, and hydroperoxides is apparent already at small doses of γ-radiation and it increases with the exposure time significantly. At the highest dose of 309 kGy a decrease in the intensity of C=O stretching mode of ketones (1717 cm−1) was observed while the overall area of the band remained the same as in the case of 188 kGy dose. The shoulders observed at 1740 cm−1 and 1772 cm−1 could be assigned to C=O stretching frequency of esters and five-membered-ring lactones, respectively. Higher doses of γ-radiation also cause the formation of two relatively strong bands in the region of conjugated double bonds. These could origin from the aromatic products or cycloenes with one double bond formed by cyclization and chain scission processes.

Betaine and l-stachydrine have been tested as phase-transfer catalysts in Michael and Darzens reactions. The catalytic effect of l-stachydrine was found comparable to that of betaine in Michael addition and even higher when considering Darzens reaction. The desired products have been obtained in higher yields in solid-liquid system than under liquid-liquid bi-phase conditions. The influence of microwave irradiation and ultrasound on the reaction rate has been studied.

5-Acetyl-4,5-dihydro-1-phenylpyrazolo[3,4-d]pyrimidin-4-one was prepared and subjected to various chemical transformations to give novel 5-heterocyclic pyrazolopyrimidinone derivatives of expected important biological activity. Then, the latter compounds were used to obtain β-keto ester and α,β-unsaturated carbonylpyrazolopyrimidinones which were used as alternate precursors to produce new pyrazolopyrimidinones substituted with five-membered heterocycles such as pyrazole and isoxazole. The structure of these compounds was identified on the basis of their chemical behaviour as well as elemental and spectral analysis.

A new type of carbon paste electrode modified with clay mineral and covered with a mercury film is presented in this work. Electrodeposition of the mercury film was performed on the carbon paste electrode modified with montmorillonite. The mercury film was deposited by both electrodeposition in situ and a preliminary electrodeposition. The pre-deposited film of mercury showed to be suitable for anodic stripping voltammetry. An open-circuit sorption of Cd, Pb, and Cu with subsequent anodic stripping voltammetry exhibited higher current responses of metals. Besides the enhanced sensitivity superior separation of the current responses during a simultaneous stripping of metals is expected to be achieved by means of the newly prepared electrode.

Ni-W alloy coatings were prepared on the steel substrate at the temperature of 60°C. The content of tungsten in coatings was increased with the growing cathodic current density. The increase of the corrosion resistance of Ni-W alloy coatings with the rising content of tungsten was confirmed by the measurement of anodic polarization curves. Annealed coatings showed better antioorrosion properties than the non-annealed ones. The properties of annealed coatings including their corrosion resistance depend on the tungsten content, too.

The effect of different chloride ions concentrations on the reactivity of iron particles was studied using chronopotentiometry. It was found that the increase of Cl− ions concentration accelerated anodic dissolution of iron, thus enhancing its surface reactivity. This fact was confirmed also by the rate of nitrobenzene reduction by iron particles. The reactivity of powder particles of various sizes, hence of different specific surface, was investigated in chloride-free and chloride-containing acetate buffer electrolytes. Experimental results indicated that the rate of nitrobenzene reduction in the presence of chloride ions in the reaction system is faster in comparison with the rate in chloride-free medium for each studied grain fraction of particulate material.

Two basic mechanisms of displacement washing of pulp fibres were investigated. Experiments were carried out in a laboratory washing cell that simulated a single stage of displacement washing. The step-change method has been employed in investigation of alkali lignin profile in outlet stream of washing effluents. The addition of urea to wash water resulted in a decrease of the liquid layer immobilized on the fibre surface. It had a positive effect on the washing efficiency expressed in terms of the void local efficiency.

The reactions taking place during methane esterification in oleum were investigated. It was found that the primary products were methyl bisulphate and formaldehyde, which was subsequently oxidized to carbon dioxide. The catalyst, Pd or PtCl4, was needed to activate methane and for its oxidation to the primary products. The formation of CO2 was not a catalytic process. It was found that the addition of either carbon dioxide or ester into the reaction mixture did not slow down the reactions. Methane oxidation in oleum is an irreversible process, during which water is produced and subsequently consumed to give sulphuric acid by the reaction with sulphur trioxide.

Momentum transfer was investigated in an unbaffled agitated vessel of inner diameter 0.3 m equipped with different off-centred impellers. The distribution of the shear rate on the tank wall as a function of the impeller type and Reynolds number was studied in the turbulent regime of the Newtonian liquid flow. The dependences of the averaged dimensionless shear rate, friction coefficient, and dissipated energy on the Reynolds number and eccentricity ratio were approximated using four-parameter equations.

Optimal operation policies were investigated for a batch reactor system with two different operation stages. At the end of the first nonisothermal stage one of the reactants was added. Since that moment the reactor was operated isothermally. In each stage behavior of the reactor was described by a set of differential equations. The maximum conversion problem was investigated subject to various operating constraints. Dynamic optimization based on the control vector parametrization was used to find the optimal control profile. Gradients of the resulting nonlinear programming problem were obtained by adjoint method based on the optimal control theory.

Submerged fermentation experiments were carried out to study the stimulating effects of the surfactant Span 20 on the growth of Aspergillus niger XP mutant and oxalic acid production from the post-refining fatty acids. Span 20 concentration of 0.75 g dm−3 was found to be the most suitable for oxalic acid production from fatty acids. Using this dose and a fermentation medium containing 30 g dm−3 of post-refining fatty acids, the oxalic acid production, oxalate yield, and overall oxalate productivity were the highest.

Three acetate mutants of the yeast species Yarrowia lipolytica were screened using batch cultivation. The strain Y. lipolytica 1.31 was found to be the most suitable for citric acid production from raw glycerol, a by-product of biodiesel production from rapeseed oil. At the initial concentration of glycerol of 200 g dm−3, the citric acid production of 124.5 g dm−3, yield of 0.62 g g−1, and productivity of 0.88 g dm−3 h−1 were achieved.

Solvent properties of ionic liquids with trihexyltetradecylphosphonium cation and bis(2,4,4-trimethylpentyl)phosphinate anion (Cyphos IL-104) or chloride anion (Cyphos IL-101) were studied. IL-104 effectively extracted lactic acid (LA) with distribution coefficients above 40 at low acid concentrations. IL-104 extracted only undissociated acid (LAH) what supported the coordination mechanism of lactic acid extraction via H-bonding. In the extraction of lactic acid by phosphonium chloride (IL-101) an ion-exchange mechanism contributed remarkably to the extraction especially at basic pH where anionic form of this acid predominated. A high solubility of water in hydrophobic IL-104 up to 14.4 mass % was connected with the formation of reverse micelles. A dual mechanism of water extraction to phosphonium ionic liquids was identified, which consisted of water incorporation into reverse micelles and the inclusion of water into the hydrated complex of lactic acid with ionic liquid (IL). The extraction of lactic acid caused splitting of reverse micelles with liberation of water from the solvent. In the saturated solvent only hydration water remained in the complex of lactic acid with phosphonium ionic liquid, with the suggested structure (LAH)p(IL)(H2O)2, where the value of p ranged from 1 to 3.