Catalytic upgrading of refinery cracked products by trans-hydrogenation: a review

The production of high premium fuel is an issue of priority to every refinery. The trans-hydrogenation process is devised to convert two low valued refinery cracked products to premium products; the conversion processes involve the combination of dehydrogenation and hydrogenation reaction as a single step process. The paper reviews the recent literature on the use of catalysts to convert low value refinery products (i.e. alkanes and alkynes or alkadienes) to alkenes (olefins) by trans-hydrogenation. Catalysts based on VOx, CrOx and Pt all supported on alumina have been used for the process. However, further studies are still required to ascertain the actual reaction mechanism, mitigating carbon deposition and catalyst deactivation, and the role of different catalysts to optimize the reaction desired products

Thermische Behandlung von CFK-Abfällen

Carbonfaser verstärkte Kunststoffe (CFK) sind aus dem Leichtbau nicht mehr wegzudenken. Da die Produktion der Fasern viel Energie benötigt ist deren Recycling anzustreben. Durch Bearbeitung und Handling während des Recyclings verkürzen sich die Carbonfasern (CF) analog zur Papierfaser. Zu kurze Fasern können nicht mehr in eine Flächenstruktur eingebracht werden und müssen daher aus dem Kreislauf ausgeschleust und einer Verwertung zugeführt werden. Untersuchungen des Lehr- und Forschungsgebiets Technologie der Energierohstoffe (TEER) der RWTH Aachen University haben gezeigt, dass die Bedingungen für eine energetische Nutzung von CF-Abfällen in Abfallverbrennungsanlagen nicht geeignet sind. Zudem können CF Betriebsprobleme verursachen. Des Weiteren können bei einer unzureichenden thermischen Behandlung sogenannte WHO-Fasern entstehen, die als gesundheitsschädlich einzustufen sind. Eine Alternative können Hochtemperaturverfahren mit höheren Verweilzeiten sein. Es kommt die Herstellung von Calciumcarbid in Frage, bei der CF als Kohlenstoffträger und der Kunststoff als Energieträger genutzt werden. Eine weitere Verwertungsoption stellt die Stahlproduktionsroute dar. Erste Untersuchungen der Bundesanstalt für Materialforschung und -prüfung (BAM) und TEER am kleintechnischen Lichtbogen der BAM zeigen, dass CF-Abfälle potentiell als Reduktionsmittel und Energieträger eingesetzt werden können

Persistent Photoconductivity, the Staebler-Wronski Effect, and Long-Range Disorder in a-Si:H

ABSTRACTWe report measurements of the conductivity, thermopower, and conductance fluctuations before and after light exposure for a-Si:H samples that show either persistent photoconductivity (PPC) or a Staebler-Wronski effect. Both the conductivity and thermopower are changed by light exposure, but no change is observed in the difference between the conductivity and thermopower activation energies for any of the samples studied here. This suggests that the long-range disorder is unaffected by light exposure. For some samples, the magnitude or statistical properties of the conductance fluctuations are affected by light exposure. We compare these results to previous studies of the Staebler-Wronski effect and discuss their implications for models of the light-induced changes and the 1/f noise in a-Si:H.</jats:p

An Alternative Approach for the Estimation of Biochar Yields

In this study, a novel approach for the determination of the solid mass yield from slow pyrolysis based on a comparison of the volatile matter contents of feedstock and char is presented. The approach was tested with experimental data from literature and own measurements. For these experiments, gravimetric data is available to determine the mass yield. The proposed method was compared with conventional ash-based calculations and the gravimetric determination of the yield. It was shown that the new approach does not only perform significantly better than ash-based methods, it also approximates the real mass yield of slow pyrolysis under atmospheric pressure quite accurately. These findings may indicate that secondary char formation does not contribute significantly to the mass yield of biomass pyrolysis under conditions found in practical production processes (low heating rates, atmospheric pressure and medium temperatures).acceptedVersion© 2018 American Chemical Society. This is the authors’ accepted and refereed manuscript to the article locked until 2019-08-10

Influence of Deposition Conditions on the 1/f Noise in Hydrogenated Amorphous Silicon

ABSTRACTThe electronic properties of a series of n-type doped hydrogenated amorphous silicon (a-Si:H) films grown with deposition rates ranging from 2 Å/s to 33 Å/s have been studied. Infrared absorption spectroscopy shows an increase in S1-H2 content with deposition rate, concurrent with a decreasing conductivity, increasing thermal equilibration relaxation time, and increasing disorder at the mobility edge as measured by the difference in thermopower and dark conductivity activation energies. The current 1/f noise properties become highly nonstationary, with increased variability and inapplicability of statistical analysis as the deposition rate increases.</jats:p