K niektorým otázkám štandardov učiteľského vzdelávania v SR

V príspevku sú analyzované niektoré dôsledky transformačných a integračných procesov na učiteľské vzdelávanie v Slovenskej republike. Ťažisková pozornosť je upriamená na štandardy učiteľského vzdelávania v zmysle bolonského procesu a nových požiadaviek na akreditáciu študijných odborov

Deactivation of palladium catalyst supported on functionalized resins in the reduction of aromatic nitrocompounds

We report on the liquid phase hydrogenation (1 M solution in methanol) of 4-nitrotoluene and 4-nitrophenol over Pd catalysts supported on anionic resins (sulphonated 4% crosslinked poly {styrene-divinylbenzene}, 5 meq./g ion exchange capacity, particles size 0.16\u20130.32 mm) at room temperature and pressure 0.25\u20131 MPa. The initial reaction rate in the hydrogenation of 4-nitrotoluene was more than ten times higher than that of 4-nitrophenol. Recycled catalysts were strongly deactivated: whereas in the hydrogenation of 4-nitrotoluene the extent of deactivation was proportional to leaching of palladium, it was not so in the case of 4-nitrophenol. Hence, the structure of the palladium crystallites surface is likely to play an important role. The stability of palladium catalysts was improved by addition of cobalt, which not only suppresses the leaching of palladium, but in proper amount also enhances the rate of hydrogenation of 4-nitrotoluene

GEO - an application software for the presentation of zircon morphometry data

Zirkóny sú jedným z najzaujímavejích indikaèných minerálov. Vyskytujú sa vo vulkanických, plutonických, sedimentárnych aj metamofovaných horninách. V r.1976 J.P. Pupin vyvinul systém interpretácie dát o morfometrii zirkónov, ktorý sa uíva pri výskume procesov zmien podmienok krytalizácie èi premien hornín. Morfometrické a mikrochemické údaje o zirkónoch boli uloené do databáz geografického informaèného systému (GIS) v rámci GIS projektu Zirkón, pre zabezpeèenie efektívnej práce na regionálných a nadregionálnych koreláciách. GIS bol realizovaný v prostredí Intergraph MicroStation PC (verzia 5). Príspevok popisuje jeden z aplikaèných programov pre toto prostredie - GEO, ktorý umoòuje poèítaèovú prezentáciu a interpretáciu rozloenia morfometrických priemerov zirkónových vzoriek. Polia morfometrických priemerov sú kontúrovate¾né a sú na pozadí vektorovej ablóny Pupinovho typogramu s vyznaèenými typologickými evoluènými trendmi

Reduction of nitrates dissolved in water over palladium-copper catalysts supported on a strong cationic resin

Catalysts containing 4 and 1 wt.% of palladium and copper, respectively, supported on cationic resin (DOWEX I x 4, gel type poly(styrene-co-divinylbenzene) with -N(CH3)(3)Cl-+(-) groups, particle size 100-200 mesh) were prepared and tested in the liquid-phase hydrogenation of nitrates in water. The catalyst was prepared by reduction of anionic chloro complexes of palladium(II) and copper(II) immobilized in the resin. Different reduction agents were employed, namely sodium borohydride in ethanol, or in water, and dihydrogen in either water (0.1-0.5 MPa) or methanol (0.5 MPa) solution of Na2CO3 (2.5%, w/w). The characterisation by means of X-ray microprobe analysis (XRMA), X-ray powder diffraction (XRPD) and transmission electron microscopy (TEM) revealed the presence of palladium metal nanoclusters and copper compounds. A cationic resin as the support was expected to facilitate the transport of the nitrate anions into the catalyst in comparison to previously employed anionic resins. This was fully proved by the generally higher specific activity of Pd-Cu catalyst supported on cationic resin. The most active and relatively stable catalyst was obtained by reduction of the immobilized metal precursors with H-2 in aqueous Na2CO3 at 0.5 MPa. The catalysts exhibited different stability with respect to leaching of metals under duty. Owing to the mechanical stirring of the reaction mixture, the catalytic particles were gradually ground and handling the reaction mixture with the suspended catalyst became rather problematic

Relationships Between Physicochemical Properties and Catalytic Activity of Polymer-supported Palladium Catalysts .1. Experimental Investigations

Polymer-supported palladium catalysts based on microporous polydimethylacrylamide-p-styrylsulphonate-methylenebis (acrylamide) with 4 and 8% m/m crosslinking degree and various metal contents were prepared, The influence of the crosslinking degree on the metal distribution and on the final activity of the catalyst was studied by a combination of diverse physico-chemical techniques like X-ray microprobe analysis, inverse steric exclusion chromatography, powder X-ray diffraction, electron spin resonance, and catalytic tests

Relationships between physico-chemical properties and catalytic activity of polymer-supported palladium catalysts .2. Mathematical model

A mathematical model including external mass transport, diffusion in the particle and chemical reaction inside the particle was developed to describe a hydrogenation process in an isothermal batchwise system with a polymer-supported metal catalyst. Various types of reaction kinetics were implemented into the model, e.g., the power law or the Langmuir-Hinshelwood type. The validity of the model was tested on data obtained from the hydrogenation of a 1 M methanol solution of cyclohexene at 25 degrees C and 0.5-1.5 MPa. Diffusional coefficients inside the catalyst, the hydrogenation rate constant and the adsorption constant of hydrogen were estimated. The best model proved to be the model considering the dissociation of hydrogen and neglecting the adsorption terms in the denominator of the Langmuir-Hinshelwood kinetics. Using polymer supports of different swellability, a linear correlation between the logarithm of the diffusional coefficient of a solute inside the polymer and the reciprocal of the swelling volume of the polymer support was derived from ESR measurements. A comparison with values of diffusional coefficients obtained from catalytic tests confirmed the validity of this correlation