Barbara Kucharczyk

Activity of monolithic Pd/Al2O3 catalysts in the combustion of mine ventilation air methane

Activity of monolithic Pd/Al2O3 catalysts in the combustion of mine ventilation air methane The activity of Pd/Al2O3 catalysts increases when Pd content is increased from 1% to 2%. Among these catalysts, 2%Pd/Al2O3 shows the highest methane combustion activity. In a reduced form, the catalyst displays a higher activity than in the oxidized form. 24-hour ageing at 600°C to 800°C lowers the catalytic activity of 2%Pd/Al2O3 due to Pd crystallite sintering. After 110-hour oxidation of 1% methane in air over 2%Pd/Al2O3, conversion decreases from 100% to 88%. Upon reduction with hydrogen (performed after 24-hour ageing at 700°C and 110-hour methane oxidation), the 2%Pd/Al2O3 catalyst regains its initial activity. The high activity of Pd catalysts renders them suitable for methane removal from coal mine ventilation air at high gas flow velocities and temperatures lower than 600°C.

The effect of catalyst precursors and conditions of preparing Pt and Pd-Pt catalysts on their activity in the oxidation of hexane

Abstract The effectiveness of under-air n-hexane oxidation over monolithic catalysts made of heat-resistant foil, containing Pt, Pd or Pt-Pd, was compared. Pt and Pd precursors, either containing chlorine or devoid of chlorine, were used to prepare the catalysts. The chlorine- containing Pt (H2PtCl6) and Pd (PdCl2) precursors were found to lower the activity of the catalysts in hexane oxidation. Studies of the effect of 0.15% Pt/Al2O3 catalyst (using H2PtCl6 as the precursor) calcination conditions on catalyst activity showed the catalyst calcined in static air at 500°C to be the most active. Airflow calcination of the catalyst does not change its catalytic properties. In comparison with the 0.5% Pd/Al2O3 catalyst obtained from Pd(NO3)2, the use of a bimetallic 0.5% Pd/0.1% Pt/Al2O3 catalyst, in which the precursors were Pd(NO3)2 and Pt(NO3)4, resulted in the lowering of 10% and 50% n-hexane temperature by 15°C and 10°C.

Solid State NMR and EIS Examination of SiO2-Epoxy Hybrid Coatings on Stainless Steel

Sol-gel SiO2 and hybrid films were deposited on 316L stainless steel by the dip process. Epoxy bisglycidyl hydroquinone (EBH) was used as an organic component in hybrid films. Both coatings were uniform and homogeneous and displayed good adhesion to the substrates. The thickness of hybrid coatings was greater than that of SiO2 coatings. Thermal condition preparation has significant influence on spectroscopic properties of samples. These features are due to changes of morphology of epoxy-silica hybrid compared to unmodified silica-gels and are related to decomposition at higher temperature. The corrosion behaviour of 316L stainless steel samples coated with SiO2 and hybrid films was studied in Ringer’s solution by electrochemical impedance spectroscopy. SiO2 and silica-based hybrid coatings produced by the sol-gel method offers a good protection against corrosion of stainless steel in Ringer’s solution. In contrast to the SiO2-coated samples and the hybrid coating heated to 200°C, the behaviour of the hybrid coating heated to 300°C changed from resistive to a barrier-like one during exposure to the solution. This change was found to be a transient effect only. During 1-month exposure to Ringer’s solution the coating lost its barrier properties.