Understanding the fate of nitrogen during catalytic hydrothermal liquefaction of sewage sludge

In this study, the fate of nitrogen during catalytic hydrothermal liquefaction (HTL) of sewage sludge (SS) is investigated using three different catalysts (CuNi/SiO$_2$, HCOOH, CuSO$_4$) with 5 wt% loading. The bio-crude yields obtained from HTL experiments catalyzed with CuNi/SiO$_2$ are similar to those obtained through non-catalyzed experiments. HCOOH slightly increases the bio-crude yields, while maximum yields of 24.5 wt% is obtained in the presence of CuSO$_4$, which also reduces the nitrogen content by 15 % and enhances the hydrocarbons compared to the non-catalyzed HTL. Mechanistic investigations regarding the interaction of amino acids and carbohydrates by Maillard reactions are carried out using model compounds, namely lysine and lactose. CuSO$_4$ effectively increases the yield with 50 % and reduces the nitrogen content by 24 % in the bio-crude during HTL of lysine alone. In the case of the model mixtures, bio-crude yields, nitrogen content, and Maillard reactions products behaved similarly both for catalytic and non-catalytic HTL, a slight reduction of amines was found in the presence of CuSO$_4$. Hydro-char and some organic compounds are assumed to act highly reductant during catalytic HTL. Coke deposition and adsorbed poisoning by Maillard reaction products are proposed as the main reasons for the deactivation of catalysts

Hydrotreatment of Fast Pyrolysis Bio-oil Fractions Over Nickel-Based Catalyst

Residual biomass shows potential to be used as a feedstock for fast pyrolysis bio-oil production for energetic and chemical use. Although environmentally advantageous, further catalytic upgrading is required in order to increase the bio-oil stability, by reducing reactive compounds, functional oxygen-containing groups and water content. However, bio-oils may separate in fractions either spontaneously after ageing or by fractionated condensation. Therefore the effects of upgrading on different fast pyrolysis bio-oil (FPBO) fractions obtained from a commercially available FPBO were studied by elemental analysis, GC-MS and 1H-NMR. Not only the FPBO was upgraded by catalytic hydrotreatment, but also the heavy phase fraction formed after intentional aging and phase separation. The reactions were conducted between 175 and 325 °C and 80–100 bar by using a nickel–chromium catalyst in batch experiments. The influence of the hydrotreatment conditions correlated with the composition of the upgraded products. Higher oxygen removal was obtained at higher temperatures, whereas higher pressures resulted in higher hydrogen consumption with no significant influence on deoxygenation. At 325 °C and 80 bar 42% of the oxygen content was removed from the FPBO. Compounds attributed to pyrolysis oil instability, such as ketones and furfural were completely converted while the number of alcohols detected in the upgraded products increased. Coke formation was observed after all reactions, especially for the reaction with the fraction rich in lignin derivatives, likely formed by polymerization of phenolic compounds mainly concentrated in this phase. Independently of the feedstock used, the upgraded bio-oils were very similar in composition, with reduced oxygen and water content, higher energy density and higher carbon content

In situ and real-time monitoring of structure formation during non-reactive sputter deposition of lanthanum and reactive sputter deposition of lanthanum nitride

Lanthanum and lanthanum nitride thin films were deposited by magnetron sputtering onto silicon wafers covered by natural oxide. In situ and real-time synchrotron radiation experiments during deposition reveal that lanthanum crystallizes in the face-centred cubic bulk phase. Lanthanum nitride, however, does not form the expected NaCl structure but crystallizes in the theoretically predicted metastable wurtzite and zincblende phases, whereas post-growth nitridation results in zincblende LaN. During deposition of the initial 2-3 nm, amorphous or disordered films with very small crystallites form, while the surface becomes smoother. At larger thicknesses, the La and LaN crystallites are preferentially oriented with the close-packed lattice planes parallel to the substrate surface. For LaN, the onset of texture formation coincides with a sudden increase in roughness. For La, the smoothing process continues even during crystal formation, up to a thickness of about 6 nm. This different growth behaviour is probably related to the lower mobility of the nitride compared with the metal. It is likely that the characteristic void structure of nitride thin films, and the similarity between the crystal structures of wurtzite LaN and La2O3, evoke the different degradation behaviours of La/B and LaN/B multilayer mirrors for off-normal incidence at 6.x nm wavelength

Wachstum und Struktur des organischen Moleküls PTCDA auf Ag(111)

Thin 3,4,9,10-perylene-tetracarboxylic dianhydride (PTCDA) films with the average thickness d between 50 and 200 Å, and the deposition rate F between 1 and 10 Å/min, have been deposited by molecular beam epitaxy on Ag(111). The films have been studied by atomic force microscopy and X-ray diffraction. It has been found that their structural and morphological properties vary significantly with the growth conditions. A transition from relatively smooth films to island growth on top of 2 wetting monolayers has been observed as a function of the growth temperature. The morphology change takes place at around 350 K and is accompanied by a change in the epitaxial relationship between film and substrate. The growth mode of the initial monolayers has been studied by in situ and in real-time X-ray diffraction as a function of the growth temperature. PTCDA grows in Stransky-Krastanov growth mode (layer-by-layer growth followed by islanding on top of the wetting layer). The transition between layer by layer growth and islanding is smeared out for low growth temperatures. This experimental observation has been reproduced by kinetic Monte Carlo simulations. While the PTCDA films with island morphology seem to be thermally stable, the relatively smooth PTCDA films grown at temperatures below 350 K show partial dewetting if they are annealed at temperatures higher than 350 K. Many aspects of the system PTCDA on Ag(111), including the epitaxial and the the morphological transition as a function or the growth temperature and the partial dewetting of smooth films upon annealing, seem to be related to the growth of fcc(111) on bcc(110) metal-on-metal epitaxial thin films.Diese Arbeit beschäftigt sich mit der Struktur und dem Wachstum von dünnen Filmen aus 3,4,9,10-Perylen-Tetracarboxyl-Dianhydrid (PTCDA), einem organischen molekularen Halbleiter. Schichten mit mittleren Dicken d zwischen 50 und 200 Å und Wachstumsraten zwischen 1 und 10 Å/min wurden mittels Molekularstrahlepitaxie unter UHV-Bedingungen hergestellt und mittels Rasterkraftmikroskopie und Röntgenstreuexperimenten untersucht. Die Struktur und die Morphologie der Schichten hängt stark von den Wachstumsbedingungen ab. Als Funktion der Wachstumstemperature wurde ein Übergang von relativ glatten Schichten zu Inseln auf einer 2 Monolagen dicken benetzenden Schicht beobachtet. Die Änderung der Morphologie bei etwa 350 K ist von einer Änderung der epitaktischen Relation zwischen Substrat und Film begleitet. In situ Röntgenstreuexperimente während des Wachstums der ersten Monolagen eines PTCDA-Films haben gezeigt, daß PTCDA im Stransky-Krastanov Wachstumsmodus wächst (Inselwachstum auf einer benetzenden Schicht). Der Übergang zwischen dem Lage-für-Lage Wachstum der benetzenden Schicht und dem Inselwachstum schmiert mit sinkender Wachstumstemperatur mehr und mehr aus. Diese Beobachtung ist mit kinetischen Monte Carlo Simulationen reproduziert worden. PTCDA-Filme mit Inselmorphologie scheinen thermisch stabil zu sein, während die relativ glatten Filme, die bei Temperaturen unter 350 K hergestellt wurden, partiell entnetzen, wenn sie auf mehr als 350 K erhitzt werden. Es hat sich herausgestellt, daß viele der Eigenschaften des organisch/inorganischen Systems PTCDA/Ag(111), z.B. die Änderung der Morphologie und der Struktur als Funktion der Wachstumstemperatur, aber auch das partielle Entnetzen der relativ glatten Schichten, Ähnlichkeiten zu den Eigenschaften des rein metallischen epitaktischen Systems fcc(111)/bcc(110) zeigen

EEG and MEG synchronisation phenomena during cognitive processes.

Schack B, Krause W, Weiss S, Rappelsberger P. EEG and MEG synchronisation phenomena during cognitive processes. INTERNATIONAL JOURNAL OF PSYCHOPHYSIOLOGY. 1998;30:50-51