Filtern
Erscheinungsjahr
Dokumenttyp
- Zeitschriftenartikel (19)
- Beitrag zu einem Tagungsband (8)
- Beitrag zu einem Sammelband (5)
- Posterpräsentation (5)
- Vortrag (4)
- Sonstiges (1)
- Forschungsbericht (1)
Schlagworte
- Verwertung (4)
- Enzymatische Alkoholyse (3)
- Lichtbogenofen (3)
- Recycling (3)
- Rückgewinnung (3)
- Altspeisefett (2)
- Candida antarctica lipase A (2)
- Chrom (2)
- Edelstahl (2)
- Enzymatic alcoholysis (2)
Eingeladener Vortrag
- nein (4)
The feasibility of using native lipase A from Candida antarctica (CAL-A) to esterify fatty acids with water-insoluble alcohols in the presence of excess water was investigated in stirred-tank reactors. For high reaction rates, a ratio of water:substrates of 0.61.4:1 (v/v) was required. CAL-A showed higher substrate selectivity for the esterification of saturated palmitic acid with branched-chain 2-ethyl-1-hexanol than for unsaturated oleic acid with linear alcohol (1-decanol). After 18 h at 70 °C in a 1.5 l bulk stirredtank reactor, an 2-ethyl-1-hexyl palmitic acid ester was obtained near 100 % yield [molar ratio palmitic acid:2-ethyl-1-hexanol ~1:1.25, with 1.11 % (w/w) Novocor ADL (based on palmitic acid weight)].
Slags from the production of high-alloyed steel contain both chemically bound chromium (mainly as Cr2O3) in the mineral fraction and elemental chromium in the metallic remainders. Thermochemical post treatment of the slag in an electric arc furnace under reducing conditions enables the nearly complete recovery of the total amount of chromium in form of a metallic alloy. The best results were achieved by resistance melting (submerged electrodes) with addition of a reducing agent into the melt. The efficiencies of the reducing agents carbon, aluminium, silicon (as ferrosilicon) and silicon carbide were investigated and compared. As aluminium is the strongest reducing agent, it is less selective and reduces much more SiO2 than Cr2O3. While SiC shows only low reactivity because of its high thermal resistance, carbon and silicon had the highest reducing potentials: More than 97% of the chemically bound chromium can be recovered by application of these reducing agents. Due to the high temperature required for the reduction of the chromium compounds, the reduction of SiO2 as an undesired side reaction cannot be avoided. However, compared with mechanical procedures that are limited to the recovery of the metallic remainders, the total chromium recovery can be significantly increased by the described reductive melting procedure.
Für die vollständige Rückgewinnung des in Edelstahlschlacken enthaltenen Chroms wird eine reduzierende Schmelzbehandlung im Elektro-Lichtbogenofen vorgeschlagen. Dabei wird das in der Schlacke enthaltene Cr2O3 zum Metall reduziert und in der schmelzflüssigen Phase separiert. Die Effektivität der Reduktion wird entscheidend durch die Fahrweise des Lichtbogenofens bestimmt. Mit optimalen Bedingungen lassen sich mehr als 90 % des enthaltenen Chroms als metallische Legierung zurückgewinnen
Zn-K transmission EXAFS measurements were performed on vitrified ashes from municipal waste incinerator facilities, which contain low amounts of Zn (up to 3 wt%) and sulphur (up to 0.5 wt%) in a ZnS phase. From the Fourier transform it can be concluded that the zinc ions are fourfold co-ordinated by oxygen or sulphur ions. The amount of zinc ions of sulphur environment, e.g. the concentration of ZnS, was determined by Fourier filtering and subsequent parameter fitting. A quantitative analysis of low ZnS concentrations up to 1 wt% has been performed for samples with a molar ratio Zn/S < 5.