Measurement of Micro Kinetics of Hydrogenation in Liquid Phase Using Raman Spectroscopy

Hydrogenation of liquid organic hydrogen carriers is usually carried out in liquid phase. To measure the kinetics of this hydrogenation, an experimental setup using in situ Raman spectroscopy for analysis of the reaction mixture is proposed. With this setup it is possible to perform hydrogenation reactions at temperatures of up to 573 K and pressures up to 25 MPa. For validation of the experimental setup the hydrogenation of 1‐octene was measured in liquid phase. The reaction progress can be monitored in detail by Raman spectroscopy. To determine kinetic parameters from the experimental data, two modeling approaches were applied: a classic kinetic model and a thermodynamic kinetic model. The results were compared to literature data.     

Ionic Liquids for Chloromethane/Isobutane Distillative Separation: Express Screening

The present study centres on room‐temperature ionic liquids (ILs) as entrainers in extractive distillation of chloromethane/isobutane mixtures. The binary system, chloromethane/isobutene, is an azeotropic system. In this study, IL entrainers are shown to be able to break the azeotrope and, thus, assure the separation in the whole range of chloromethane/isobutane ratios. ILs formed from different cations and anions are considered and their influence on chloromethane/isobutane separation is explored. Among the ILs studied, those containing the trifluoromethanesulfonate ([CF₃SO₃]^–) or tricyanomethanide ([C(CN)₃]^–) anion are demonstrated to exhibit an enhanced potential for chloromethane/isobutane separation compared to the corresponding ILs based on the bis(trifluoromethylsulfonyl)imide ([Tf₂N]^–) anion. Moreover, the ILs enclosing these anions are cheaper than those with the [Tf₂N]^– anion. Thus, the separation ability, solubility of chloromethane/isobutane mixtures, and costs of IL entrainers can be adjusted by the right choice of cations and anions.     

Invited review: Systematic review of diagnostic tests for reproductive-tract infection and inflammation in dairy cows

The objective of this study was to conduct a systematic and critical appraisal of the quality of previous publications and describe diagnostic methods, diagnostic criteria and definitions, repeatability, and agreement among methods for diagnosis of vaginitis, cervicitis, endometritis, salpingitis, and oophoritis in dairy cows. Publications (n = 1,600) that included the words “dairy,” “cows,” and at least one disease of interest were located with online search engines. In total, 51 papers were selected for comprehensive review by pairs of the authors. Only 61% (n = 31) of the 51 reviewed papers provided a definition or citation for the disease or diagnostic methods studied, and only 49% (n = 25) of the papers provided the data or a citation to support the test cut point used for diagnosing disease. Furthermore, a large proportion of the papers did not provide sufficient detail to allow critical assessment of the quality of design or reporting. Of 11 described diagnostic methods, only one complete methodology, i.e., vaginoscopy, was assessed for both within- and between-operator repeatability (κ = 0.55–0.60 and 0.44, respectively). In the absence of a gold standard, comparisons between different tests have been undertaken. Agreement between the various diagnostic methods is at a low level. These discrepancies may indicate that these diagnostic methods assess different aspects of reproductive health and underline the importance of tying diagnostic criteria to objective measures of reproductive performance. Those studies that used a reproductive outcome to select cut points and tests have the greatest clinical utility. This approach has demonstrated, for example, that presence of (muco)purulent discharge in the vagina and an increased proportion of leukocytes in cytological preparations following uterine lavage or cytobrush sampling are associated with poorer reproductive outcomes. The lack of validated, consistent definitions and outcome variables makes comparisons of the different tests difficult. The quality of design and reporting in future publications could be improved by using checklists as a guideline. Further high-quality research based on published standards to improve study design and reporting should improve cow-side diagnostic tests. Specifically, more data on intra- and interobserver agreement are needed to evaluate test variability. Also, more studies are necessary to determine optimal cut points and time postpartum of examination.     

Effect of fluid–particle-interactions on dispersing nano-particles in epoxy resins using stirred-media-mills and three-roll-mills

Fibre reinforced composites are indispensable in the field of modern lightweight structures, such as used in aerospace, automotive industry or in wind power plants. Those materials provide high weight savings and increase the efficiency of a structure significantly. Therefore, various efforts are made to continuously improve the quality of the matrix and the fibres. By embedding nano-particles into the epoxy matrix, the mechanical properties as well as the electrical and thermal characteristics can significantly be improved [1]. In most cases these nano-sized particles are produced as dry powders not as single primary particles but rather as particle collectives consisting out of several primary particles. For the application in reinforced composites the particles must be suspended in epoxy resin as separately dispersed primary particles or in a certain aggregate size. Generally, the influencing parameters to break up the aggregates in a dispersion process can be divided into the stress mechanism, the intensity and the frequency of the dispersing machine itself, the properties of the dispersed particles (e.g. the particle–particle interactions) the properties of the homogenous phase and the particle–resin-interactions. Besides the effect of the chosen dispersing machine the optimization of the dispersing process was investigated by applying modified particle surfaces and varying the fluid properties. The results show that the surface properties of the particles must fit to the epoxy resin properties and the attractive forces between the primary particles must be reduced or the stabilization improved, respectively. An indication for an improved stabilization and adjustment of the particles surface properties to the fluid properties can be obtained by measurements of the contact angle and the rheological properties. Generally, an increase of viscosity and mass fraction of the product leads to a higher energetic efficiency of the dispersion process in the stirred media mill and three-roll-mill.     

Ionic Liquids as Operating Fluids in High Pressure Applications

During the past years a growing number of scientists and engineers have investigated ionic liquids because of their outstanding advantages in several areas. Their unique physical properties and specific chemical behavior make these liquids very interesting for new and innovative applications. For commercial implementation ionic liquids have to meet a number of requirements. For use in high pressure applications they should have a low compressibility, an adjustable gas solubility and a superior lubricating ability. A screening of the relevant parameters was conducted in several experimental setups built for these purposes. Most of these parameters were also examined under long term conditions with regard to real process conditions and safety guarantee in possible high pressure applications. A major application is the compression of oxygen using ionic liquid as operating fluid. Besides, there are many more applications where the superior chemical and physical properties of ionic liquids are of high potential benefit.     

A transient Poole-Frenkel effect at the semiconductor surface of MAOS devices

The generation of the inversion layer in MOS and MAOS structures shows remarkable differences. Whereas for MOS samples free minority carriers build up the inversion layer, the positive layer in n-type silicon MAOS devices is mainly caused by a trap charging process. This trap charging shows peculiar properties. After a voltage step which depletes the semiconductor surface from majority carriers the gate current has a maximum at a time of about 10⁻⁴s after the step. This current which is proved to be related to the increase of the trap charge is strongly temperature and field dependent. It is shown that the time dependent maximum in the current is caused by a transient Poole-Frenkel effect at the semiconductor surface.     

Imaging of Fluid Dynamics in a Structured Packing Using X‐ray Computed Tomography

For the investigation of fluid dynamics from computed tomography (CT) images, an evaluation method was developed that enables data acquisition directly from the recorded CT images. A segmentation algorithm was implemented in Matlab to assign every component a specific gray value. A comparison of weight experiments with CT scans and following segmentation demonstrates the good accuracy of this method. The liquid holdup in different Mellapak 500.Y packings was determined through CT measurements and compared to predictive correlations from the literature. Three‐dimensional visualizations of short packing sections enable an evaluation of the liquid distribution and the flow morphology of the liquid in the packing. The common assumption of an evenly wetted packing surface with a constant liquid film thickness could not be proved.     

Ionic Liquids for Propene‐Propane Separation

This paper presents an extensive study on the feasibility of ionic liquids (IL) for the extractive distillation of propene‐propane mixtures. A new experimental method for express screening of non‐volatile entrainers was elaborated. A series of ILs and their mixtures were screened at ambient temperature and low pressures. The screening results show that every tested IL turns a low boiler propene into a high boiler and the alkene‐to‐alkane separation factor can be as low as 0.28. The solubility and separation efficiency can be tuned by adjusting the chemical structures of the ions forming the IL. It was found that shortening of the alkyl substituents of the imidazolium ions leads to a decrease in capacity and to an increase in the separation factor. Interestingly, ILs containing nitrile functionalities in either the cation or the anion showed, in our experiments, enhanced separation ability combined with still good capacities. From our thermodynamic measurements, [EMIM][[B(CN)₄] was proved to be the most promising candidate. Binary mixtures of ILs were also tested and resulted in separation factors and capacities between the values for the individual ILs. For the most promising candidates, also autoclave measurements at elevated temperatures and pressures were carried out. These experiments indicate that the separation ability decreases with growing temperature and loading. In general, our study definitely proves the high potential of ILs to act as entrainers in the extractive distillation of propene‐propane mixtures or for the separation of any other low‐boiling alkene‐alkane mixture.     

3D Visualisation of PEMFC Electrode Structures Using FIB Nanotomography

It is well known that the electrode structure of a PEMFC has a huge influence on the water management and thereby on the cell performance. In this work, two MEAs – one prepared by an airbrushing technique and the other by a novel fast spray coating technique (multilayered MEA) – were analysed with respect to porosity, pore size distribution, tortuosity and their electrochemical performance. FIB nanotomography with following 3D reconstruction, SEM investigation on ultramicrotomic thin‐sections, and single cell tests were performed on these MEAs. The results show a higher porosity and lower pore size for the multilayered MEA. The multilayered MEA reaches a Pt utilisation of 1,962 mW mg^–1 and a peak power density of 210 mW cm^–2, whereas the airbrushed MEA only provides a Pt utilisation of 879 mW mg^–1 and a peak power density of 218 mW cm^–2. The Pt utilisation calculations showed in combination with the structural characterisations that a homogeneous pore structure and Pt distribution provide an advantage with regard to performance and efficiency of the PEMFC. Furthermore, the multilayered MEA may offer an advantage over the airbrushed MEA in its long term stability, which was observed in preliminary tests.     

Nanoparticles with various surface modifications as functionalized cross-linking agents for composite resin materials

The performance of epoxy resins used for carbon fibre reinforced plastics can be significantly improved by the incorporation of nanoparticles. It is well known that the effect of material altering depends on many factors as filler material, particle distribution, particle size and shape. This paper investigates the hypothesis that particle surface modifications lead to a further improvement of the mechanical properties. Results of nanocomposites filled with four different surface modified boehmite particles are presented. The material was tested with different filler contents and analysed for chemical bonding, viscosity, thermal properties and bending performance. Surprising results show a strong influence of the surface modification on the viscosity, but no significant changes in the other material characteristics. The change of filler content in contrast has an influence on all tested performances of the nanocomposites. The results show a contrary effect of network interruption due to sterical hindrance by the particles and reinforcement due to the stiff ceramic fillers. For different filler contents these two effects have a varying influence on the material characteristics. From these results a model for the mechanism of the particle reinforcement in thermosets is concluded, which helps to understand the effectiveness of nanoparticles as reinforcement of epoxy resins.