Umsatz- und Selektivitätsverhalten von Dicobaltoctacarbonyl und Cyclopentadienylcobaltdicarbonyl auf Silicagel-, Alumosilicagel- und Aluminiumoxid-Trägern bei der Hydroformylierung von Hex-1-en

Conversion and Selectivity in Hydroformylation of Hex-1-en with Silica-Gel-, Silica-Alumina-Gel and Alumina-Oxide- Supported Dicobalt Octacarbonyl and Cyclopentadienylcobalt Dicarbonyl The catalytic influence of silica-gel-, silica-alumina-gel- and alumina-oxide-supported Co₂(CO)₈ and CpCo(CO)₂ on the conversion and selectivity in hydroformylation of hex-1-en has been studied at 353 K under 120 bar syngas pressure in acetonitrile. The support systems were prepared by impregnation of SiO₂ (Grace), SiO₂/4% Al₂O₃ (Kali Chemie), SiO₂/11% Al₂O₃ (Kali Chemie) and Al₂O₃ (Kali Chemie) using Co₂(CO)₈ and CpCo(CO)₂ solutions in pentane, dichlormethane and 2-chlorpropane. The results are discussed with regard to some measured relevant support characteristics. The turn over numbers especially those of silica-gel- and silica-alumina-gel supported Co₂(CO)₈ and CpCo(CO)₂ show positive effects in relation to a heterogeneous catalytic process within these reactions.     

Charakterisierung und Störstoffanalyse von rückgewonnenen Stoffströmen aus Wärmedämmverbundsystemen

Due to the growing energy requirements, the proportion of external thermal insulation composite systems (ETICS) installed has increased significantly during the past 50 years. Due to the longevity of these systems, ETICS waste is currently accumulating. Owing to the complex construction as well as a multitude of differently installed materials and substances of the past generations, there are many uncertainties and problems with the clean and low-pollutant processing of such systems. In the frame of this work, the ETICS were processed and sorted before being screened for ingredients or pollutants as well as for the purity of the recovered material fractions.     

Elektrochemische abscheidung von sauerstoff und ozon an bleidioxid und platin-anoden in wässrigen elektrolyten mit 18O-markiertem wasser

During the electrolysis of water, especially on lead dioxide anodes, a considerable amount of ozone is evolved. It has been proposed by several authors, that a significant contribution to the oxygen atoms of molecular oxygen and ozone originates from the anions of the electrolyte. We have used marked water containing ¹⁸O isotopic tracer for solvent, with some of the important oxo-acids and phosphate buffer as electrolytes. On both platinum and lead dioxide anodes we have shown that under the conditions of our experiments at relatively low current densities (200 mA cm²) all oxygen atoms originate from water only. This applies too for simultaneous reactions as in the case of chlorate oxidation.     

Ausgleich der Volatilität der Erneuerbaren Energien mittels Wärmespeichern auf Salzbasis

To compensate for the volatility of renewable energies, solutions beyond fossil reserve power plants are needed. One approach is salt-based heat storage with phase change materials (PCM). In order to achieve economic efficiency, ambitious targets are required. A sensible and latent heat storage system for the temperature range around 400 °C based on salts and thermal oils with high development potential is presented.     

Klärschlammverbrennung in einer stationären Wirbelschicht mit integrierter Phosphor-Rückgewinnung

Currently, wet-chemical and thermochemical processes in particular are being discussed for the future obligatory recovery of phosphorus from sewage sludge. The coupling of phosphorus recovery with incineration in stationary fluidized bed incinerators, the dominant mono-incineration technology, offers potential advantages in terms of aftertreatment costs and economic efficiency. Tests have shown that by adjusting the incineration conditions and adding additives, an ash could be produced that corresponds to the fertilizer ordinance (DüMV) and can, therefore, potentially be used as phosphorus recyclate.     

Untersuchung von Polymerablagerungen während der Synthese in einem Wärmeübertrager

To investigate the unwanted deposition of polymers on heat transfer surfaces (polymerization fouling) the deposition of a vinyl acetate/vinyl ester copolymer during emulsion polymerization is investigated. The aim is to identify fundamental differences to the fouling behavior of an already reacted vinyl acetate/ethylene copolymer. For a qualitative comparison the surface coverage is observed using a digital microscope. For the quantitative examination the fouling resistance is calculated from the mass and the layer height of the deposited material. The degree of polymerization has a significant influence on the deposition behavior. The already reacted material system shows a larger fouling mass and a more pronounced, crater-shaped surface coverage, whereas during polymerization fouling a clearly optically different drop-shaped surface coverage was formed.     

Darstellung und Charakterisierung oligomeree und polymerer Ethinylsilane mit Si2?Si4-Einheiten

Preparation and Characterization of Oligomeric as well as Polymeric Ethynylsilanes Containing Si₂ Si₄ Units The treatment of methylchlorodisilanes with ethynyldigrignard (BrMgCCMgBr) resulted in oligomeric as well as polymeric ethynyldisilanes. The kind of this products is related to the chloro functionality of the starting disilane. The reaction of SiClMe(SiCl₂Me)₂ as well as SiMe(SiCl₂Me)₃ yielded polymers beside small amounts of the monomeric products (HCC)MeSi[SiMe(CCH)₂]₂ and MeSi[SiMe(CCH)₂]₃.     

The structure of Stoehr's Glycerinäther

Stoehr's Glycerinäther has been shown to be the ether ofcis 2,6-bis(hydroxymethyl) dioxane.     

Synthese von Dithiocarbamidsäureestern des Pyrazols

Synthesis of Pyrazolyldithiocarbonates The reaction of 3-amino-pyrazole 1 with carbondisulfide and alkylating agents in basic conditions to yield different dithiocarbonates 2 – 8 was studied. The dithiocarbonates 2a react with isocyanates to form 1-acyl-5-acylamino-pyrazoles 9 – 10 . Acyl migrations were observed depending on the reaction temperature and the isocyanates. The results obtained enable us to correct some confusions in the literature about thioureas of pyrazoles.     

Geschützte Aminooxazoline der Arabinose und Ribose

Protected Aminooxazolines of Arabinose and Ribose The reaction of D-arabinose or D-ribose with cyanamide afforded 2-amino-1,2-oxazolines 1 which were treated with dihydropyran or ethylvinylether. In the presence of PTS the 3′,5′-di-THP- or 3′,5′-di-O-ethoxyethyl-D-arabino-(ribo)-furo-[1′,2′:4,5]-2-oxazolines 2 and 3 could be isolated as useful intermediates for the preparation of nucleosides. When the 2-aminooxazolines are treated with benzyloxycarbonylchloride or its p-substituted derivatives the N-3 atom of the oxazoline ring is preferentially substituted. Under these conditions the exocyclic amino function is always replaced and 2-oxo-3-benzyloxycarbonylderivatives 4 are obtained; only traces of the corresponding 2-aminoderivatives 5 are formed. Treatment of 4 with acetic anhydride, benzoylchloride, and benzoylcyanide, respectively, results in the 3′-, 5′-di-O-acyl derivatives 6 . Mild hydrolysis of the benzyloxycarbonyl group with trifluoroacetic acid yields the 3′,5′-di-O-acyl-D-arabino-(ribo)-furo-[1′,2′:4,5]-2-oxooxazolidines as further intermediates for the synthesis of nucleosides.     

Zeolites Promoting Quinoline Synthesis via Friedländer Reaction

Catalytic performance of zeolites H-BEA, H-MFI, H-FAU and H-MOR, exhibiting textural differences and with different Brønsted and Lewis acid sites concentration, have been studied in the synthesis of quinolines via Friedländer reaction. H-BEA and H-FAU efficiently promoted the condensation of 2-aminoaryl ketones 3 with ethyl acetoacetate (4a) or acetylacetone (4b) under mild reaction conditions, those being the first examples of zeolites as catalysts for this transformation. While H-FAU showed similar catalytic behaviour than that reported for (Al)SBA-15 affording mixtures of quinolines 5 and quinolones 6, H-BEA mainly led to quinolines 5 in almost total selectivity and good yields. However, H-MFI and H-MOR zeolites afforded quinolones 6 as the major reaction product. Methodology reported here was found to be useful for the synthesis of biologically active compounds with excellent yields avoiding unnecessary purifications protocols and tedious work-up procedures.     

Stromdichteverteilung auf einer mit gasblasen bedeckten elektrodenoberfläche

With the help of a mathematical model the local and integral current distribution for different degrees of bubble coverage at a gas evolving electrode were calculated. On this basis the influence of the adhering gas bubbles on the position of the current-potential curve for a bubble coverage (Θ) of Θ = 0.14 is obtained.The i/u curve is shifted by only a few millivolts in the negative direction. This results agrees well with experimental findings.     

Rücklaufmengen und Verwertungswege von Altbatterien aus Elektromobilen in Deutschland

Electro-mobility is considered a key technology for reducing CO₂ emissions in road traffic. However, an aspect that is little addressed in the discussion about the advantages of electro-mobility for the reduction of greenhouse gas emission is the high ecological footprint of the manufacturing of electric vehicles, especially due to the resource-intensive traction battery. In addition to the provision of renewable electricity for vehicle charging, efficient recycling of the battery materials and the longest possible use of the battery systems and components are prerequisites for the sustainable design of electro-mobility. This article provides an overview of the circular value chain of obsolete traction batteries from electric vehicles. Based on a system-dynamics and a discrete-event simulation approach, future return quantities of obsolete traction batteries are estimated on the basis of current diffusion scenarios, and various utilization options from 2nd-life concepts to alternative recycling processes are presented and discussed.     

Absorption of CO2 and H2S in aqueous alkanolamine solutions using a fixed-bed reactor with cocurrent downflow operation in the pulsing flow regime: Absorption von CO2 und H2S in wäßrigen alkanolamin-lösungen in einem Festbettreaktor bei abwärtsfließendem Gleichstrombetrieb und pulsierendem Arbeiten

Absorption rates of H₂S and CO₂ in several aqueous alkanolamines in a cocurrent downflow fixed-bed reactor operated in the pulse flow regime have been measured in order to obtain information on the potential selectivity and on the mass transfer parameters. From these experiments it can be concluded that this type of reactor seems to be very suitable for the selective removal of H₂S from acid gases.It was not possible to derive correlations which are always valid for the calculation of the mass transfer parameters in laboratory-scale contactors. The results of the present study in combination with the data published in the literature were correlated with only one unknown parameter in which the influence of the physical properties of the system and the shape and material of the packing were combined. This parameter has to be determined empirically.Small amounts of acid gases in aqueous alkanolamine solutions have a pronounced effect on the properties, such as the foaming behaviour, of the liquid phase. The pressure drops measured in the cocurrently operated fixed-bed reactor were affected substantially by small amounts of acid gases present in the aqueous alkanolamine solutions and up to now this effect could not be explained satisfactorily.For the design of contactors for industrial purposes, detailed scale-up rules are required. In the present study this aspect is not investigated.     

Acylierung von tautomeriefähigen C-Amino-azolen mit Amidin- bzw. Guanidinstruktur

Acylation of Tautomerizable C-Amino-Azoles with Amidine or Guanidine Structure Amino-azoles can react with electrophiles to give different regioisomers. Stable ringacylated isomers were isolated at low temperatures and under neutral conditions. Acyl migrations are obtained at higher temperatures and under basic conditions to form the thermodynamic stable isomers. The different isomers can be characterized by mean of ¹H-NMR, ¹³C-NMR, IR and mass spectrometry. The results obtained enable us to correct some confusions in the literature about the regioselectivity of the acylation of amino-azoles.