Upgrading of lignocellulose-derived sugars to value-added chemicals via heterogeneously catalyzed continuous-flow processes

In the present work, a methodology is proposed for the synthesis of metal-based hydrogenation catalysts supported on hierarchically porous carbon pellets, which are suitable for industrial flow processes. For the preparation of the carbon support, durum semolina is used as the carbon source, in addition to ZnO nanopowder as the porogenic templating agent. Owing to their large surface area of 756 m²/g and mesopore volume of 0.49 cm³/g (QSDFT N₂ adsorption), the extruded cylindrical pellets (2.4 × 3.5 mm) offer excellent properties as a support material for highly active catalyst pellets, tailored to the use in large packed bed reactors. The performance of the Ni/C and Pt/C catalysts, prepared with several metal loadings from the support pellets, is investigated in packed-bed flow reactors for two important applications of biomass valorization: the hydrogenation of the bioderived platform molecules 5-hydroxymethylfurfural (HMF) and levulinic acid (LA) to the value-added chemicals 2,5-dimethylfuran (DMF) and γ-valerolactone (GVL), respectively. Aiming at the development of sustainable processes, only water and ethanol are used as green solvents in these processes. In the selective hydrogenation of HMF in ethanol over the synthesized 21wt Ni/C catalyst, a DMF yield of 80.5 (99.0 conversion) is obtained at 150 °C. High catalytic stability is observed during the whole operation period of 33 h. For the hydrogenation of LA to GVL in water at 160 °C, the prepared 2.7wt Pt/C catalyst provides excellent GVL yield of 96.4 (98.9 conversion) and a Pt time yield of 54.7 molGVL/h/molPt (66.2 conversion). With formic acid (FA) as an alternative and renewable hydrogen source, the GVL selectivity was further enhanced to 98.7 (65.3 LA conversion) and a 92.6 GVL yield (97.7 LA conversion) was obtained, using the same type of 2.7wt Pt/C catalyst at 220 °C. The high activity and remarkable selectivity of the FA-assisted hydrogenation demonstrates its potential for a sustainable and self-sufficient integrated refining strategy of sugars to GVL, in which in situ formed FA can be employed as a bioderived reducing agent

Nickel on nitrogen doped carbon pellets for continuous flow hydrogenation of biomass derived compounds in water

Hydrogenation reactions in water at elevated temperatures are challenging for heterogeneous catalyst. Thus, we present a simple, cheap, scalable, and sustainable approach for synthesizing an efficient and water-tolerant Ni catalyst supported on highly porous nitrogen-doped carbon (NDC) in pellet shape. The performance of this catalyst was evaluated in the aqueous-phase hydrogenation of lignocellulosic biomass-derived compounds, i.e., glucose (Glu), xylose (Xyl) and vanillin (V), using a continuous-flow system. The prepared 35 wt.- Ni on NDC catalyst exhibited a high catalytic performance in all three different aqueous-phase hydrogenation reactions, i.e., conversion of Glu, Xyl and V was 96.3 mol, 85 mol and 100 mol and yield of sorbitol (Sor), xylitol (Xyt) and 2-methoxy-4-methylphenol (MMP) was 82 mol, 62 mol and 100 mol, respectively. This high activity was attributed to heterojunction effects stabilizing and adjusting the homogenously dispersed Ni nanoparticles on the surface of NDC. Changing the electron density in the Nickel nanoparticle allows high performance of the catalyst under long time of stream (7 to 30 h) with minimized Ni leaching

Beiträge zur Geschichte des Landkreises Regensburg 30

Marginalien von 14 Autoren; darin: Hecht, Otto: Die Altstraße Regensburg-Landshut (auf dem Gebiet des Landkreises ) (S.2); Hecht, Otto: Die erste urkundliche Erwähnung des Bäumel-Hofes in Obertraubling (S. 5); Böck, Emmi / Herzog, Hans / Doerfler, Heinrich: Drei Sagen bzw. Sagengestalten aus dem Regensburger Süden (S. 6); Motyka, Gustl: Mittelalterliches Geleit von Hemau nach Regensburg (S. 9); Strehler, Heinz: Haus Nr. 21 in Matting - eines der ältesten Häuser Bayerns (S. 10); Zink, Wendelin: Die Wasserburg Haidau vor 200 Jahren (S. 11); Färber, Konrad M.: Ein Augenblick europäischer Geschichte (S. 12); Fendl, Josef: Fünf Säcke Brot für Tegernheim (S. 14); Bäumel, Xaver: Ein Lehrer der "schlechtesten Schule im ganzen Königreich" (S. 18); Rösch, Georg: 600 Jahre Hofgeschichte Kleinkiefenholz (S. 22); Deininger, Leonhard: Mit 3,3 Millionen nachts unterwegs (S. 24); Zausinger, Ludwig: Ein Nachtrag zum Heimatbuch "Thalmassing" (S. 26); Forster, Fritz: Beim Korea-Wirt (S. 28); Fendl, Josef: Neutraubling - Choppertown (S. 20

The steel–concrete interface

Although the steel–concrete interface (SCI) is widely recognized to influence the durability of reinforced concrete, a systematic overview and detailed documentation of the various aspects of the SCI are lacking. In this paper, we compiled a comprehensive list of possible local characteristics at the SCI and reviewed available information regarding their properties as well as their occurrence in engineering structures and in the laboratory. Given the complexity of the SCI, we suggested a systematic approach to describe it in terms of local characteristics and their physical and chemical properties. It was found that the SCI exhibits significant spatial inhomogeneity along and around as well as perpendicular to the reinforcing steel. The SCI can differ strongly between different engineering structures and also between different members within a structure; particular differences are expected between structures built before and after the 1970/1980s. A single SCI representing all on-site conditions does not exist. Additionally, SCIs in common laboratory-made specimens exhibit significant differences compared to engineering structures. Thus, results from laboratory studies and from practical experience should be applied to engineering structures with caution. Finally, recommendations for further research are made

5-Hydroxymethylfurfural hydrodeoxygenation to 2,5-dimethylfuran in continuous-flow system over Ni on nitrogen-doped carbon

Waste lignocellulosic biomass is sustainable and an alternative feedstock to fossil resources. Among the lignocellulosic derived compounds, 2,5-dimethylfuran (DMF) is a promising building block for chemicals, e.g., p-xylene, and a valuable biofuel. DMF can be obtained from 5-hydroxymethylfurfural (HMF) via catalytic deoxygenation using non-noble metals such as Ni in the presence of H2. Herein, we present the synthesis of DMF from HMF using 35 wt. Ni on nitrogen-doped carbon pellets (35Ni/NDC) as a catalyst in a continuous flow system. The conversion of HMF to DMF was studied at different hydrogen pressures, reaction temperatures, and space times. At the best reaction conditions, i.e., 423 K, 8.0 MPa, and space time 6.4 kgNi h kgHMF-1, the 35Ni/NDC catalyst exhibited high catalytic activity with HMF conversion of 99 mol and 80 mol of DMF. These findings can potentially contribute to the transition toward the production of sustainable fine chemicals and liquid transportation fuels

Two-dimensional correlation measurements of electron cyclotron emission fluctuations on the stellarator Wendelstein 7-AS

The miniaturization of receiver arrays permits the arrangement of numerous poloidally staggered radial sightlines of an electron cyclotron emission (ECE) diagnostic for the measurement of the electron temperature and its fluctuations, making two-dimensional (2D) imaging of the electron temperature and its fluctuations caused by plasma turbulence possible. For the stellarator W7-AS, the development of a fully monolithic microwave integrated circuit 150 GHz subharmonic mixer array is under development. As a first step, a 2D ECE system for the measurement of electron temperature fluctuations using four individual horn-reflector arrangements in conjunction with multichannel heterodyne radiometers was installed and set into operation. With Gaussian beam optics and four poloidally staggered sightlines, electron temperature fluctuations could be characterized in radial and poloidal directions simultaneously. First observations in purely electron cyclotron resonance heated stellarator plasmas reveal a broadband drift-wave feature. Earlier experiments showing a decrease of the electron temperature fluctuation level with increasing heating power were confirmed. Additionally, it was revealed, using the 2D ECE correlation radiometer, that an increased velocity shear might account for the decrease of the coherence length and thus for the reduction of the electron temperature fluctuation level