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.

Activity of La0.75Sr0.25Cr0.5Mn0.5O3−δ, Ni3Sn2 and Gd-doped CeO2 towards the reverse water-gas shift reaction and carburisation for a high-temperature H2O/CO2 co-electrolysis

Abstract: The syngas mixture of CO and H2, e.g. from natural gas reforming, is currently an important feedstock supplier for the synthesis of numerous chemicals. In order to minimize fossil source dependency and reduce global warming, alternative processes to produce syngas, such as high-temperature co-electrolysis of H2O and CO2 via the internal reverse water-gas shift (RWGS) reaction, may be meaningful. In this study, the influence of the H2 : CO2 ratio on the activity, selectivity and stability of the as-prepared La0.75Sr0.25Cr0.5Mn0.5O3−δ (LSCrM) and Ni3Sn2 as well as commercial Ni and Gd-doped CeO2 (GDC20) powder materials for the reverse RWGS reaction was investigated in a tubular quartz glass reactor at 700 °C and 800 °C and ambient pressure. The highest conversion factor close to the maximum value of 50% for CO was yielded for the LSCrM, Ni and GDC20 samples by applying a 0.5 : 0.5 H2 : CO2 feed ratio at 800 °C. Similar activity was calculated for the Ni3Sn2 alloy after normalization to the Ni mass content. Moreover, all the investigated catalysts exhibited higher selectivity for CO and H2O products than Ni, with which CH4 molar concentrations up to 0.9% and 2.4% were collected at 800 °C and 700 °C, respectively. The influence of feed pressure on the carburisation process was inspected in a tubular Ni–Cr reactor. Under a carbon-rich gas mixture at 3 bar and 700 °C, large amounts of graphitic carbon were deposited solely on the Ni sample after 100 h of exposure time. After the exposure of the powder materials to 0.5 : 0.5 and 0.9 : 0.1 H2 : CO2 atmospheres for 300 h at 700 °C and 10 bar, traces of amorphous carbon were surprisingly detected only on Ni3Sn2 powder via Raman microscopy. Thus, because GDC20 ist not active for electrochemical H2 production, LSCrM or a mixture of both LSCrM and GDC20 materials appears to be the most promising candidate for Ni substitution in high-temperature H2O/CO2 co-electrolysis.

Aufkohlung von Hochtemperaturwerkstoffen – Teil II: Experimentelle Überprüfung der rechnergestützten Beschreibung von Eindiffusion und Ausscheidung

Abstract: Mit Hilfe thermogravimetrischer Untersuchungen der Aufkohlungskinetik der beiden Modellegierungen Ni 10 Cr und Ni 25 Cr wird die Anwendbarkeit der in Teil I entwickelten Rechenmethode zur Beschreibung der Aufkohlung bei gleichzeitiger Ausscheidung von Karbiden bestatigt. Die Versuche erfolgen im Temperaturbereich von 850°C bis 950°C in H2 + 1,14 Vol.-% CH4. Die Temperaturabhangigkeit der maximalen Loslichkeit und des Diffusionskoeffizienten des Kohlenstoffs in diesen Legierungen werden ermittelt, die Stabilitaten der auftretenden Karbide angepast. Die Ubereinstimmung von Rechnung und Experiment wird anhand des metallographisch ermittelten Volumenbruchteils, der Lage der Ausscheidungsfronten der Karbide, des Restgehaltes an Chrom in der Legierungsmatrix und der flachennormierten Gewichtszunahme uberpruft. Carburization of high-temperature materials – Part II: Experimental testing of the computer aided description of inward diffusion and precipitation In part I of this study a calculation method was presented which permits the computation of carburization processes which involve simultaneous precipitation of carbides. In the present study, this model is confirmed by measurements of carburization kinetics of two model alloys Ni 10 Cr and Ni 25 Cr with the help of thermogravimetric methods. The experiments were carried out in the temperature range from 850°C to 950°C in an atmosphere of H2 with 1.14 Vol.% CH4. The dependence of the solubility and the carbon diffusion coefficient on temperature in the above alloys were determined and the stabilities of the forming carbides adapted. Satisfactory agreement between calculation and experiment is found on the basis of metallographically determined volume fraction, the progress of the precipitation front of the carbides, the remaining chrome concentration of the alloy matrix and the weight gain per unit surface area.

Lilac aldehydes and lilac alcohols as metabolic by-products of fungal linalool biotransformation

Abstract: Nineteen different fungi were screened to test their capability to convert (±)-linalool into lilac aldehydes and lilac alcohols. Solid phase microextraction (SPME) in combination with GC-MS was used to identify the target compounds by comparing retention times and mass spectra with chemically synthesised standards. Most of the strains showed specific and complex product spectra, often with linalool oxides and dihydrolinalool as major metabolites. Aspergillus niger DSM 821, Botrytis cinerea 5901/02 and Botrytis cinerea 02/FB II/2.1 generated the desired lilac fragrance compounds as metabolic by-products.

Diffusion coatings for aggressive high temperature process environments

Abstract: Diffusion coatings can provide an excellent corrosion protection in aggressive high temperature environments due to the enrichment of thermodynamically stable oxide formers at the alloy surface. Besides conventional monoelement diffusion coatings (e.g. al diffusion), multielement coatings can be produced in a single process step. The production of al diffusion and Al–Si, Al–Ti and Al–Si–Ti codiffusion coatings on ferritic and austenitic steels and Ni base alloys, and their performance under high temperature chloridising, sulfidising and metal dusting environments are described.