Study of the selective catalytic reduction of NOx on an efficient Fe/HBEA zeolite catalyst for heavy duty diesel engines

The present paper addresses the removal of NO_x from the exhaust of heavy duty vehicles using the SCR technique. The studies were conducted with a highly active H-BEA zeolite exhibiting a molar Si/Al ratio of 12.5 and a Fe load of 1.0 wt.% (1Fe/HBEA). The pronounced efficiency of 1Fe/HBEA is reflected by the apparent turnover frequency being superior to traditional V₂O₅/WO₃/TiO₂. The nature of the Fe sites was investigated with high resolution transmission electron microscopy (HRTEM), ⁵⁷Fe Mössbauer spectroscopy and powder X-ray diffraction (PXRD). In connection with previous examinations it is deduced that the iron sites represent octahedrally coordinated high spin Fe³⁺ cations. Furthermore, highly dispersed species, which are the most active sites, are supposed to be paramagnetic, while oligomeric and particulate structures indicate superparamagnetic behaviour.The practical evaluation of the 1Fe/HBEA catalyst was systematically carried out including laboratory studies of granulated powder and honeycomb samples as well as engine bench tests. For the latter studies a coated honeycomb prototype was employed showing very similar efficiency as referred to a commercial V₂O₅/WO₃/TiO₂ pattern.Furthermore, 1Fe/HBEA exhibits pronounced hydrothermal stability after aging at 550 °C which represents an elevated exhaust temperature of heavy duty vehicles. The aging caused no change in fast SCR, i.e. when a c(NO₂)/c(NO_x) ratio of 0.5 was used, and only minor decline in standard SCR. The slight aging effect is mainly referred to little decrease in BET surface area and NH₃ uptake, respectively. PXRD indicated maintenance of the BEA structure, whereas ²⁷Al nuclear magnetic resonance spectroscopy showed removal of some Al from the zeolite framework. Contrary, UV–vis spectroscopy evidenced no effect of hydrothermal aging on the composition of the Fe sites. Finally, the catalyst also maintained its efficiency after SO₂ aging at 300 °C. Diffuse reflectance infrared Fourier transform spectroscopic studies showed adsorption of molecular SO₂ on the zeolite substrate releasing already at about 400 °C.     

Network central: regional positioning for innovative advantage

This paper investigates the characteristics of regions that contribute to their positioning within the emerging innovative networks supported by the European Union’s Framework Program using a spatial-network approach. Although the importance of research collaborations in network formation has been generally recognized, relatively little research has investigated why some regions are able to attain prominent network positions, while others do not. We analyze a spatially detailed data base of EU Framework Program-supported research ventures in Austria to understand how specific geographical nodes come to occupy important positions within key research networks. The paper deploys what is termed here a network positioning function to investigate the question of network centrality and at the same time to illustrate the possibilities of combining network and spatial analysis to examine this or other research questions where similar approaches might be applicable. Findings reveal the factors important for understanding advantageous positions enjoyed by regional districts as measured by alternative centrality concepts. Concepts that distinguish innovation exploitation from exploration were used to interpret network positions, which further clarify positioning in highly localized versus distant member networks.     

Synthesis of Bicyclic N‐Arylmethyl‐Substituted Iminoribitol Derivatives as Selective Nucleoside Hydrolase Inhibitors

A series of bicyclic N ‐arylmethyl‐substituted iminoribitols were synthesised and evaluated in vitro against T. vivax nucleoside hydrolase. The importance of the N–Asp40 interaction was confirmed and depends on an optimal pK_a value, which can be influenced by substituents. The compounds were active inhibitors of nucleoside hydrolase (IAG‐NH) and are inactive against human purine nucleoside phosphorylase.

     

Vakuumerzeugung durch Produktdampf-betriebene Strahlpumpen in der Kunstfaserindustrie

Vacuum generation by product vapour driven jet pumps in the plastic fibre production For industrial application in the fiber industry product vapour driven jet pumps in combination with liquid ring pumps for generation of vacuum have proved and succeeded. The most important advantages of such vacuum systems are the high operational reliability, small wear and tear, customized design, low environmental impact, reasonable investment costs and simple operation.     

Hall sensor response to an inhomogeneous magnetic field

The response of a Hall-effect sensor to a spatially dependent magnetic field is of importance for many applications such as magnetic microscopy and nondestructive testing. Using the analytical expression of the response of a Greek cross Hall sensor response to an ideal field dot published a few years ago, we have calculated its sensitivity and its full width at half maximum for the field produced by a magnetic dipole and by two coplanar lines. The experimental results are in good agreement with theory. They show that the spatial resolution is roughly equal to the dimension of the central part of the Greek cross and that a flux-meter approximation is not appropriate for modeling such Hall-effect sensors for very close field sources.     

Photoelectrochemical kinetics of Eosin Y-sensitized zinc oxide films investigated by scanning electrochemical microscopy under illumination with different LED

The overall efficiency of the light-induced charge separation in dye-sensitized solar cells depends on the kinetic competition between back electron transfer and dye regeneration processes by a redox electrolyte. In a previous study, the reduction of the intermittently formed photo-oxidized dye molecules by iodide ions in the electrolyte phase was investigated using the feedback mode of a scanning electrochemical microscope (SECM) and a quantitative model had been derived. Here we provide a more thorough experimental verification of this model by variation of the excitation wavelength, light intensities and mediator concentrations. Nanoporous ZnO/Eosin Y films prepared by self-assembly were used as model electrodes and were used with an iodide/triiodide electrolyte. The experimentally found effective rate constants could be related to the rate constant for the reaction of the dissolved donor with photo-oxidized Eosin Y bound to ZnO and the absorption spectrum of the dye and confirmed the assumption made in the derivation of the model. For the regeneration process of Eosin Y, a rate constant of k_ox with different light emitting diodes and light intensities is determined.     

Lean management in indirect business areas: modeling,analysis, and evaluation of waste

Because of the rising complexity of indirect business areas, processes become less transparent and it is therefore more difficult to distinguish between value-adding activities and waste. As an essential requirement for purposeful optimization, all existing types of waste in a process must be identified and quantified in terms of their negative impacts on the process productivity and the customer’s wishes. Hence, this article proposes an approach that increases the transparency and ensures objectivity by concentrating on the value stream, revealing weaknesses, detecting their causes, and evaluating the impact on the process according to the philosophy of Lean Management. The methodology is separated into three main steps: process modeling, analysis, and the evaluation of waste in indirect business areas. This results in an effect-orientated classification of potential waste in the process and yields a priority list of fields of action. The basis for the implementation of process optimization is thus developed.