Structure and Surface Properties of Zirconia-Supported Molybdena Obtained by Slurry Deposition

A series of MoO₃/t-ZrO₂ catalysts was prepared by slurry deposition. Structural studies revealed that the presence of MoO₃ had no influence on the phase composition of zirconia support. IR/RS and EPR results confirmed that both isolated and polymeric (2D) oxomolybdenum species occurred on catalysts surface. Adsorption of NO resulted in the reduction of molybdenum centers with simultaneous formation of surface nitrates.     

Thermal decomposition of polyurethane pressure-sensitive adhesives dispersions

The thermal degradation of polyurethane pressure-sensitive adhesives (PSAs) at temperature 600 °C was investigated by the application of pyrolysis-gas chromatography technique. The present study was undertaken in order to determine the key thermal degradation products of polyurethane PSA based on isophorone diisocyanate (IPDI), polypropylene glycol (PPG), hydroxylated polybutadiene (HTPB), dimethylolpropionic acid (DMPA) and to elucidate the mechanism of the polyurethane PSAs pyrolysis.     

Application of nitroso-R-salt in modification of strongly basic anion-exchangers Amberlite IRA-402 and Amberlite IRA-958

The batch method was applied in order to determine the influence of phase contact time, solution pH and temperature as well as HCl concentration on nitroso-R-salt (NRS) deposition on the strongly basic anion-exchangers Amberlite IRA-402 and Amberlite IRA-958. The equilibrium sorption of NRS from 1 × 10^− 4 mol/dm³ solution was achieved after 60 min. The amount of NRS adsorbed decreased with increasing hydrochloric acid concentration. A significant increase of NRS uptake is observed with the increase of initial solution pH up to 3 for Amberlite IRA-402. Amberlite IRA-402 and Amberlite IRA-958 in chloride form as well as modified by means of NRS were used for recovery of Pd(II) ions from 0.1, 0.5 and 1.0 mol/dm³ HCl solutions.The studied anion-exchangers in NRS form as far as their application in removal of Pd(II) chlorocomplexes is concerned can be presented in the order: Amberlite IRA-402 > Amberlite IRA-958.     

Effect of liquid circulation in the draft-tube reactor on precipitation of calcium carbonate via carbonation

Precipitation of calcium carbonate was carried out in a draft-tube reactor by mechanical agitation of calcium hydroxide solution with carbon dioxide. The circulation of a reactive mixture was created by gas flow and a stirrer. It was observed that a higher circulation decreased the precipitation time and improved CO₂ consumption. A higher circulation velocity of liquid contributed to smaller calcium carbonate particles at the end of precipitation.     

Potassium Promotion of Cobalt Spinel Catalyst for N2O Decomposition—Accounted by Work Function Measurements and DFT Modelling

The beneficial effect (decrease of the half conversion temperature by 100 °C) of potassium doping, in the range of 0–5 atoms/nm², on N₂O decomposition over Co₃O₄ was analyzed by work function measurements and DFT calculations. The optimal potassium surface loading was found to be 1.8 atoms/nm². The effect was explained in terms of electronic promotion gauged by lowering of the catalyst work function by 0.48 eV (for K₂CO₃ precursor) and 0.44 eV (for KOH). The promotional effect is discussed in relation to the theoretical and experimental surface dipoles determined from Hirshfeld atomic charges and geometry of the postulated potassium adspecies and from the Topping model, respectively.     

Surface chemical composition of SiC-cored nanowires investigated at room and elevated temperatures in ultra-high vacuum

Nanowires with SiC core were produced via Si/PTFE combustion synthesis in air and deposited from 1,2-dichloroethane suspension on an Au (111) surface. The dependence of the chemical bonding states on temperature (300-673 K) between different elements being a building material of nanowires' sidewalls was investigated by X-ray photoelectron spectroscopy (XPS) in ultra-high vacuum (UHV) conditions. Apart from silicon and carbon, the presence of oxygen and nitrogen was observed. Moreover, Si₃N₄ seems to be the second most important compound (after SiC) forming the amorphous outer shell of SiC nanowires. It is shown that carbon-containing compounds (oxides, nitrides, hydrocarbons) are substantially removed under annealing. It is also reported that a noticeable part of subsurface oxygen in the outer shell reacts with nitrogen at 473-573 K forming stable N-O bonds on nanowires' surface.     

Magnetic Mixed Matrix Membranes Consisting of PPO Matrix and Magnetic Filler in Gas Separation

Poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) and magnetic neodymium powder particles MQP-14-12 have been used for the preparation of magnetic mixed matrix membranes. Permeability diffusion and sorption coefficients of O₂, N₂, and synthetic air components were estimated for homogeneous and heterogeneous membranes using the Time Lag method based on dynamic experiments in a constant pressure system. The influence of magnetic field and magnetic powder particles on the gas transport properties of MMMs was studied. The results showed that the membrane permeation properties were improved with the magnetic neodymium particle filling. It was observed that the magnetic ethylcellulose and poly(2,6-dimethyl-1,4-phenylene oxide) membranes showed higher gas permeability, while their permselectivity and solubility were rather maintained or slightly increased. The results also showed that the magnetic powder addition enhanced gas diffusivity significantly in EC and PPO membranes.     

Electrode processes of bismuth in weakly acidic,neutral and alkaline solutions

The electrode process Bi(III)+ 3e = Bi(Hg) has been investigated in weakly acidic, neutral and alkaline solutions by means of amalgam polarography and cyclic voltammetry and chronopotentiometry with the use of hanging amalgam drop electrode. It has been found that in weakly acidic and neutral solutions, oxidation of bismuth amalgam goes through aquocomplexes of bismuth. In the cathodic step on cyclic voltammetry curves four peaks of reduction are observed, with magnitude and shape strongly dependent on pH of the solution. These peaks have been ascribed to the reduction of Bi³⁺, Bi(OH)⁺₂, Bi(OH)⁺² and Bi(OH)₃.In alkaline solutions, oxidation of bismuth amalgam leads to Bi(OH)₃. In cathodic scan on cyclic voltammetry curves only one peak is observed, which corresponds to Bi(OH)₃ reduction. Formal potentials of electrode process and solubility product of Bi(OH)₃ have been calculated and discussed. The step-wise nature of the overall electrode reaction has been ascertained and discussed. At higher concentrations of OH^? ions, Bi(OH)₃ dissolves.