Pavel Krystynik

Interactions of the (R) Ru-BINAP catalytic complex with an inorganic matrix in stereoselective hydrogenation of methylacetoacetate: kinetic, XPS and DRIFT studies

Stereoselective hydrogenation of methyl acetoacetate to optical isomers of methyl-3-hydroxybutanoate over various forms of supported [RuCl((R)-BINAP)(p-cymene)]Cl is reported. The catalysts were prepared via two alternative methods: direct immobilization, and surface anchorage with heteropolyacids. The kinetic data (rate constants, optical yields, overall selectivity to methyl-3-hydroxybutanoate) were discussed and interpreted with help of XPS and DRIFT to assess bonding surface interactions. In all cases montmorillonite as a model support was employed. It was shown that the stereoselective course was dependent on the mode of [RuCl((R)-BINAP)(p-cymene)]Cl immobilization. The procedure based on the commonly used impregnation did not provide a catalyst with a stable anchorage of the active complex. Strong surface anchorage was found for a catalystproduced with help of H4SiMo12O40 heteropolyacid, but due to structural changes upon the reaction the catalyst performance in the reaction was poor. When H3PW12O40 was employed, the immobilization provided a catalyst with a very good performance. The two-step immobilization via the dimer [RuCl2(p-cymene)]2 instead of the one-step with [RuCl((R)-BINAP)(p-cymene)]Cl yielded a catalyst with the performance parameters comparable to the homogeneous experiments with [RuCl((R)-BINAP)(p-cymene)]Cl dissolved in the reaction mixture. It was due to breaking up the original dimer structure and accomplishing the surface interaction through the adsorbed monomeric units.

Elimination of dissolved Fe3+ ions from water by electrocoagulation

AbstractElectrocoagulation (EC) was applied for elimination of dissolved Fe3+ ions from model contaminated water. Electrochemical experiments were performed using a coagulation set-up with the volume of storage tank of 50 L. To represent inorganic contamination, FeCl3·6H2O was chosen as a model pollutant; its concentration was equal to 50 mg/L. Experiments were carried out by circulating model effluent (1 pass) through the cell at a flow rate (40 L/h) whilst operating the power supply in galvanostatic mode. Dosing concentration was varying by changing the input current between set points and holding for sufficient time for steady state to be reached and for a sample to be collected. The process using the steel electrode reached removal efficiency up to 99%, depending on pH, and proved to be very suitable for elimination of dissolved Fe3+ ions from water. However, electrochemical experiments using the aluminum electrode reached removal efficiency only up to 25%. The different efficiency of two anodes is probably due to lower adsorption capacity of hydrous aluminum oxide for iron ions in comparison to hydrous ferric oxides. Produced nanostructured flocs were subsequently filtered, dried, and characterized by N2 physisorption, X-ray photoelectron spectroscopy, and scanning electron microscopy. Obtained characteristics synchronously demonstrate different tendencies of Al and Fe nanostructured flocs.