DECHEMA

About: DECHEMA is a nonprofit organization based out in Frankfurt am Main, Germany. It is known for research contribution in the topics: Corrosion & Oxide. The organization has 756 authors who have published 1307 publications receiving 25693 citations.

Refractory metals and nickel in high temperature chlorine-containing environments - thermodynamic prediction of volatile corrosion products and surface reaction mechanisms: a review

Abstract: Thermodynamic calculations are an important tool for prediction of chemical reactions. In many cases the results help to understand and describe the experimental observations. In others, especially if reaction kinetics play a major role, their predictive value can be rather limited and the projected results have to be treated with care. One such case are high temperature chlorine corrosion conditions. For example, thermodynamically a similar corrosion behavior of nickel and molybdenum is predicted in chlorine-containing atmospheres at low oxygen partial pressures. In contrast to their calculated similarity, experimental results showed much higher resistance of molybdenum against the chlorinating attack. Above 800 °C nickel is rapidly consumed, whereas molybdenum remains almost inert. This paper reviews the literature on the corrosion mechanisms and kinetics of nickel and molybdenum in chlorine-containing environments as well as in mixed oxygen-chlorine-containing atmospheres. Based on the literature review, differences in their reaction kinetics are discussed, taking into account the deviation from an ideal thermodynamic correlation between the partial pressure and the reaction kinetics via the often used Hertz-Langmuir equation. Finally it is shown that the findings concerning the special characteristics of molybdenum and nickel and the conclusions drawn from experimental observations on high temperature chlorine corrosion can also be transferred to other metals.

A recombinant α-dioxygenase from rice to produce fatty aldehydes using E. coli

Abstract: Fatty aldehydes are an important group of fragrance and flavor compounds that are found in different fruits and flowers A biotechnological synthesis of fatty aldehydes based on Escherichia coli cells expressing an α-dioxygenase (αDOX) from Oryza sativa (rice) is presented α-Dioxygenases are the initial enzymes of α-oxidation in plants and oxidize long and medium-chain Cn fatty acids to 2-hydroperoxy fatty acids The latter are converted to Cn − 1 fatty aldehydes by spontaneous decarboxylation Successful expression of αDOX in E coli was proven by an in vitro luciferase assay Using resting cells of this recombinant E coli strain, conversion of different fatty acids to the respective fatty aldehydes shortened by one carbon atom was demonstrated The usage of Triton X 100 improves the conversion rate up to 1 g aldehyde per liter per hour Easy reuse of the cells was demonstrated by performing a second biotransformation without any loss of biocatalytic activity

Solution Nitriding of Stainless Steels for Process Engineering

Abstract: Solution nitriding is a controlled heat treatment of stainless steels carried out at 1100 ± 50 °C in N2 gas. Depending on the alloy content a hard martensitic or a ductile austenitic high nitrogen case of about 2 mm in depth is formed, which reduces wear by sliding, fretting, erosion and cavitation. In contrast to carbon dissolved nitrogen does not impair the resistance to superimposed corrosion, so that solution nitriding is suitable for components subjected to the flow of aggressive fluids containing suspended particles which is often encountered in chemical and process engineering. Randaufsticken nichtrostender Stahle fur die Verfahrenstechnik Randaufsticken ist eine kontrollierte Warmebehandlung fur nichtrostende Stahle, die bei 1100 ± 50 °C in N2 Gas durchgefuhrt wird. In Abhangigkeit von der Legierungszusammensetzung ergibt sich eine hochstickstoffhaltige harte martensitische oder duktile austenitische Randschicht von etwa 2 mm Dicke, die Verschleis durch Gleiten, Fressen, Erosion und Kavitation reduziert. Im Gegensatz zu Kohlenstoff beintrachtigt Stickstoff nicht den Widerstand gegenuber einer uberlagerten Korrosionsbeanspruchung, so das das Randaufsticken fur Komponenten geeignet ist, die der Stromung aggressiver Medien mit gelosten Partikeln ausgesetzt sind, was oft in der Verfahrenstechnik der Fall ist.