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.

Oxalic acid prodn. - by electro-chemical reductive dimerisation of carbon dioxide

Abstract: is electrochemically reduced, using an electrolytic cel contng. a stable aprotic solvent (e.g. propylene carbonate) and at least 1 stable conducting salt (e.g. a tetra-1-4C-alkyl-ammonium carbonate) dissolved therein, the cell comprising a cathode (e.g. a Cr-Ni-steel) which consists of an electrical conductor that does not chemisorb the CO2, and of an anode (e.g. a noble metal such as Pt). The cathode is kept free of reducible cpds. and the anode is kept free of oxalate-anions formed at the cathode. This may be achieved by interposing ion exchange membranes. Electro-chemical reduction of CO2 in protic solvents (water) has in the past resulted in the formation of formic acid. The prodn. of oxalic acid by the claimed process has been made possible by using suitable aprotic solvents, conducting salt and material for the electrodes.

Oxidation behaviour of particle reinforced MoSi2 composites at temperatures up to 1700 °C: Part I: Literature review

Abstract: In the first part of this paper the results of a literature review are presented. An overview of the oxidation behaviour in air and in combustion environments of both pure MoSi 2 and MoSi 2 composites in the temperature range from 400 to 1650 °C is given. The second part of this paper reports about our results from oxidation tests with selected MoSi 2 composites (containing 15 vol.-% Al 2 O 3 , Y 2 O 3 , ZrO 2 , HfO 2 , SiC, TiB 2 , ZrB 2 , or HfB 2 , respectively) from different development stages at temperatures in the pest region as well as up to 1700 °C. The third part describes the oxidation behaviour of the optimised MoSi 2 composites developed on the basis of the results from part II.

Expanding the Isoprenoid Building Block Repertoire with an IPP Methyltransferase from Streptomyces monomycini.

Abstract: Many synthetic biology approaches aim at expanding the product diversity of enzymes or whole biosynthetic pathways. However, the chemical structure space of natural product forming routes is often restricted by the limited cellular availability of different starting intermediates. Although the terpene biosynthesis pathways are highly modular, their starting intermediates are almost exclusively the C5 units IPP and DMAPP. To amplify the possibilities of terpene biosynthesis through the modification of its building blocks, we identified and characterized a SAM-dependent methyltransferase converting IPP into a variety of C6 and C7 prenyl pyrophosphates. Heterologous expression in Escherichia coli not only extended the intracellular prenyl pyrophosphate spectrum with mono- or dimethylated IPP and DMAPP, but also enabled the biosynthesis of C11, C12, C16, and C17 prenyl pyrophosphates. We furthermore demonstrated the general high promiscuity of terpenoid biosynthesis pathways toward uncommon building blocks by the E. coli-based production of polymethylated C41, C42, and C43 carotenoids. Integration of the IPP methyltransferase in terpene synthesis pathways enables an expansion of the terpenoid structure space beyond the borders predetermined by the isoprene rule which indicates a restricted synthesis by condensation of C5 units.

High temperature corrosion in molten solar salt: The role of chloride impurities

Abstract: The role of chloride impurities in molten NaNO3-KNO3 (solar salt) mixture on corrosion behavior of low-chromium ferritic-martensitic X20CrMoV11-1 steel (X20) and stainless steel 316 (SS316) was studied at 600 °C. Gravimetric and metallographic methods were employed to characterize the kinetics of oxidation and the resulting corrosion products. Steel X20 showed non-protective character in both low- (up to 0.02 wt% Cl−) and high- (up to 0.25 wt% Cl−) chloride salts by forming a thick and non-compact oxide scale. A significant increase in weight gain was observed when X20 steel was immersed in the high-chloride-containing salt. Furthermore, the scale underwent severe deformation. SS316 showed superior corrosion resistance in both low- and high-chloride salts. Oxide scales formed on both steels included two zones: an outer Na-rich oxide and an inner mixed oxide based on Fe2O3 and Fe3O4 structures. The morphology and composition of these zones were significantly different on X20 and SS316 steels. A passive Cr-rich oxide layer at the metal/oxide interface was characterized as a protective layer. In the case of stainless steel 316 this layer showed even higher continuity when tested in the high-chloride salt resulting in better protection during the isothermal test.