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The paper presents the results on biofilm formation induced by pure Desulfovibrio desulfuricans strains and its effect on corrosion behaviour of 2205 duplex stainless steel (DSS). Biofilm formation and damage process stimulated by D. desulfuricans strains are analysed with reference to their metabolic activity and to the surface characterisation of structure and configuration of the biofilm. Electrochemical techniques are applied to monitor bacterial attachment to the steel surface and to determine the influence of bacteria on the passivity and corrosion resistance of 2205 DSS. The obtained results prove that 2205 DSS is rapidly colonised by D. desulfuricans and that the biofilms formed affect its corrosion resistance. Bacterial activity leads to the more noble corrosion potential values and to the increased current densities on the potentiodynamic polarisation curves. SEM observations reveal micropits as well as signs of crevice attack on the steel surface. [ABSTRACT FROM AUTHOR]

The electrochemical behavior of the weld metal, heat-affected zone (HAZ), and base material of super duplex stainless steel (SDSS) welded joints, made with the application of flux-cored arc welding (FCAW) and submerged arc welding (SAW), were investigated with the use of metallographic examinations (optical microscopy and scanning electron microscopy), potentiodynamic polarization measurements and total hydrogen content determination in the initial state and after hydrogen charging. The obtained results revealed that the effect of hydrogen depended on the microstructure and type of the region of a welded joint. The highest amount of hydrogen penetrated the welded joint charged at 1 mA cm−2. It was observed in case of the FCAW-welded joint, made with lower heat input. The electrochemical measurements showed that the base material was the most corrosion resistant part of the welded joint while the hydrogen charging strongly changed pitting and general corrosion susceptibility of HAZ and weld metal of both welded joints. [ABSTRACT FROM AUTHOR]

A series of titania-supported ruthenium and platinum catalysts was investigated in the levulinic acid hydrogenation towards γ-valerolactone, a key reaction for the catalytic transformation of biomass. It was shown that various morphologies and phases of titania strongly influence the physicochemical and catalytic properties of supported Ru and Pt catalysts in different ways. In the case of the catalyst supported on mixed TiO2 phases, Ru particles are exclusively located on the minority rutile crystallites, whereas such an effect was not observed for platinum. The platinum catalyst activity could be increased when the metal was dispersed on the large surface-area anatase, which was not the case for ruthenium as a result of its agglomeration on this support. The activity of ruthenium on anatase could be increased in two ways: a) when RuO2 formation during catalyst preparation was avoided; b) when pure anatase support material was modified so that it exhibited no microporosity. The obtained results allow a better understanding of the role of the support for Ru and Pt catalysts. [ABSTRACT FROM AUTHOR]

Hydrolytic hydrogenation of cellulose toward fuel additive - γ-valerolactone (GVL) - has been studied, and the catalytic performance of Pt/TiO2 and Ru/TiO2 and reaction conditions were optimized. Additionally, new information about the changes of catalyst surface after the reactions of lignocelulose toward GVL was obtained. Two procedures were investigated: one-pot hydrolysis-hydrogenation and hydrolysis of cellulose followed by hydrogenation in two separate reactions. Spent catalysts were tested by time-of-flight SIMS (ToF-SIMS). Reaction conditions strongly influence the GVL yield, which was much lower during one-pot procedure where much higher carbon deposit and catalyst deactivation was observed by ToF-SIMS and temperature-programmed reduction. Ruthenium catalysts were more active than platinum ones in liquid phase reactions toward GVL, independently of the feedstock. [ABSTRACT FROM AUTHOR]