Experimentelle Untersuchung einer Dampfstrahlkälteanlage mit einem alternativen Treibmedium

In order to determine the increase in efficiency of n‐octane compared to water as a propellant in ejector refrigeration systems, a pilot plant with a cooling capacity of up to 1.5 kW was set up. In both cases, water was used as the suction medium, the so‐called cooling medium. From the pressure and temperature measurement data, the two mass flows, the so‐called motive and suction flow, and from this the mass flow ratios could be obtained. Subsequently, a comparison of the theoretical coefficient of performance for the two propellants was carried out in the case of closed‐loop operation.     

Occurrence and mass balance of isoflavones on an experimental grassland field

Isoflavones and coumestrol (COU) are estrogenic compounds that are naturally produced by plants (e.g., red clover, soybeans). Although these compounds have been extensively studied in food and feed, only little is known about their environmental fate. Therefore, we investigated the occurrence of isoflavones (formononetin, daidzein, equol, biochanin A, and genistein) and COU over 3.5 years in red clover, manure, and soil of a grassland field with and without manure application, as well as their emission via drainage water. Isoflavones were regularly quantified in plant (≤ 15 × 10(6) ng/g(dry weight (dw))), manure (≤ 230 × 10(3) ng/g(dw)), soil (≤ 3.4 × 10(3) ng/g(dw)), and drainage water samples (≤ 3.6 × 10(3) ng/L). In contrast, COU was observed only in manure and soil. Cumulative isoflavone loads emitted via drainage water were around 0.2 × 10(-3) kg/ha/y, which is very little compared to the amounts present in red clover (105-220 kg/ha/y), manure (0.5-1.0 kg/ha/y), and soil (0.1-5.1 kg/ha/y). Under good agricultural practice, no additional emission of isoflavones into drainage water was observed after manure application. With calculated 17β-estradiol equivalents up to 0.46 ng/L in drainage water, isoflavones can constitute a dominant and ecotoxicological relevant portion of the total estrogenicity in small rural river catchments.     

KnowVolution of a Fungal Laccase toward Alkaline pH

To date, commercial laccase preparations are used in the food, textile, and paper and pulp industries (mild pH). Laccases are attractive in the synthesis of dye molecules or oxidative lignin treatment, which take place at high pH (≥8.0). So far, one fungal laccase has been reported to be active at alkaline pH. Herein, engineering of the fungal laccase from Melanocarpus albomyces (MaL) for increased activity toward the substrate 2,6-dimethoxyphenol at pH (≥9.0) is reported. Through a knowledge-gaining directed evolution (KnowVolution) campaign, the key positions Leu365 and Leu513 were identified to increase alkaline tolerance. Both positions are located in close proximity of the T1Cu site. Molecular docking and simulations studies reveal that both substitutions act in a synergic way to stabilize and improve laccase activity at higher pH. Kinetic characterization of the final variant MaL-M1 (L365E/L513M) revealed at pH 9.8 a threefold improved k_cat (k_cat=(6.0±0.2) s⁻¹) compared with that of wild-type M. albomyces laccase (k_cat=(2.11±0.07) s⁻¹).     

Non‐isothermal crystallization of polypropylene with sorbitol‐type nucleating agents at cooling rates used in processing

Sorbitol‐type nucleating agents used as clarifiers for polypropylene (PP) show a complex interplay of phase and crystallization behavior. To study the crystallization behavior, cooling measurements were performed by fast scanning calorimetry using rates between 10 and 4000 K s^?1. These rates correspond to cooling rates used in processing. These measurements were combined with conventional differential scanning calorimetry (DSC) measurements at 10 K min^?1. The optical properties were characterized by haze measurements. For this investigation the commercially available clarifiers 1,3:2,4‐bis(3,4‐dimethylbenzylidene)sorbitol and 1,2,3‐tridesoxy‐4,6:5,7‐bis‐O‐[(4‐propylphenyl)methylene]nonitol were added to PP in various amounts up to 0.6 wt%. At relatively slow cooling rates only a single crystallization process was observed. In contrast, fast cooling leads to a complex crystallization behavior with up to four different crystallization processes. It was found that the temperature of the main crystallization process during fast cooling correlates with the optical properties from haze measurements. Finally, the cooling rate dependence of the different crystallization processes is discussed in terms of nucleating efficiency of the clarifiers. We conclude that the results of conventional DSC measurements cannot be extrapolated in a simple way to describe the nucleation activity of nucleating agents at cooling conditions relevant during processing. © 2018 Society of Chemical Industry     

Enhancement of the analytical solution for double torsion test using extended finite element techniques

The double torsion (DT) testing technique is not yet standardized for fracture mechanics characterization of brittle materials because previous analytical solutions are insufficient to represent accurate load-displacement (P-h) relationship and stress intensity factor (SIF) in experiments. Therefore, we attempt at enhancing the analytical solutions based on three-dimensional extended finite element (XFE) analysis to obtain reproducible results from DT tests. As a result, the P-h relationship in DT test can be efficiently described by combining the bending deformation of a DT specimen with torsional deformation. Weighting factors are proposed as functions of thickness, moment arm and crack length. DT experiments are conducted with sodalime glass specimens to further validate the proposed weighting factors. Finally, correction terms are provided for SIF and fracturs toughness evaluation in DT specimen with straight and curved crack fronts. Fracturs toughness values of sodalime glass specimens with various thickness are consistent, and in good agreement with literature values.     

Equipment and Separation Units for Flow Chemistry Applications and Process Development

Process development and small‐scale production gets more and more important in fine chemistry and pharmaceutical production. An equipment toolbox assists process synthesis presented in this contribution. A microfluidic calorimeter can measure kinetic and thermodynamic reaction data with commercial plate reactors. A tubular reactor coiled with 90° bends allows for long residence time with low axial dispersion, also known as coiled flow inverter (CFI). A similar setup is used for continuous‐flow cooling crystallization. Small‐scale columns with rotating internals are employed for distillation and liquid‐liquid extraction. Main emphasis will be put on automation and scale‐up in future steps.