Neues Verfahren zur Methanol- und Ammoniak-Synthese. Der Gas/Feststoff/Feststoff-Rieselströmungsreaktor – ein neuer Reaktortyp zur Führung chemischer Gleichgewichtsprozesse

New process for the production of methanol and ammonia. The gas/solids/solids thrickle flow reactor – a new kind of reactor for chemical equilibrium processes . A new process for the production of ammonia or methanol has been developed in the high pressure laboratory of Twente Technical University. The reactants can be made to react completely in a single reactor pass, thus avoiding expensive recirculation. Complete reaction without recirculation is accomplished by a combination of two reversible processes: a chemical reaction and a selective adsorption of the reaction product on a solid in constant flow. On introduction of an inert-gas free stoichiometric mixture of reactants into the reactor, the exhaust gas outlet can be closed. If there is an excess of one of the reactants or of inert gas, it can leave from the top of the reactor. Such a process has been accomplished in a new gas/solids/solids trickle flow reactor in which a granulated adsorbent ?rains”? through a fixed bed of catalyst. The present article describes the use of this kind of reactor for methanol synthesis. Considerable savings in production costs are expected relative to the modern Lurgi low pressure process. A pilot plant is to be built to characterize and evaluate the new process. Royal Dutch Shell has registered a patent application.     

The kinetics of carbide precipitation in silicon-aluminum steels

The kinetics of carbide precipitation in a fully processed 2.3 wt Pct silicon, 0.66 wt Pct aluminum electrical steel with carbon contents of 0.005 to 0.016 wt Pct were investigated over the temperature range from 150 to 760 °C and times from 30 seconds to 240 hours. The size, morphology, and distribution of the carbide phases, as functions of aging time and temperature, were determined by optical and transmission electron microscopy. The 1.5T core loss was also evaluated and correlated with the changes in precipitation. Distinct C curves were observed for the formation of grain-boundary cementite at temperatures above 350 °C and a transition carbide ({100} _α habit plane) at temperatures below 350 °C. Grain-boundary cementite had a relatively small effect on core loss. The large increases in core loss that accompanied transition carbide precipitation peaked at specific aging temperatures depending on the carbon content of the steel. Once a transition carbide dispersion was initially established at a given aging temperature, particle coarsening and core loss changes were generally insensitive to aging time. The influence of a combined addition of silicon and aluminum on the solubility of cementite and the transition carbide in iron was estimated and discussed. This paper is based on a presentation made at the symposium “Physical Metallurgy of Electrical Steels” held at the 1985 annual AIME meeting in New York on February 24–28, 1985, under the auspices of the TMS Ferrous Metallurgy Committee.     

Precontact 50-kHz vocalizations in male rats during acquisition of sexual experience.

50-kHz ultrasonic vocalizations emitted by male rats during a 5-min period before introduction of a female (precontact vocalizations [PVs]) were analyzed in the context of acquisition of sexual experience. Changes in the main copulatory parameters and their N-methyl-D-aspartate (NMDA) receptor dependence, the role of contact with either anestrous or estrous females, and conditioning to odor and background cues were also investigated. Mount latency (ML) and intromission latency (IL) decreased after the 1st copulatory session, but ejaculation latency (EL) changed significantly only starting from the 4th session onward. The number of PVs gradually increased during the first 3–4 sessions. Blocking of NMDA receptors affected PVs and EL but not ML or IL. After a 5-month break in copulatory sessions, ML remained unchanged, whereas EL increased and the number of PVs decreased significantly. PVs were most robustly elevated by contact with estrous females. Exposure to background cues resulted in a linear decrease in number of PVs during 10 subsequent sessions without exposure to a female. The results suggest that, in the course of acquisition of a sexual experience, PVs reflect a learning process that depends on a rewarding value of sociosexual contact. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Electrochemical behaviour of palladium electrode: Oxidation, electrodissolution and ionic adsorption

In electrochemistry, Pourbaix diagrams also known as potential-pH diagrams map out the regions of stability of metals as well as the regions of possible existence of stable compounds. The stable states other than the metallic one are macroscopic compounds, typically oxides and hydroxides, or their hydrated forms. Yet, several noble metals possess the ability to form thin surface oxides, to adsorb anions, and to adsorb or to absorb hydrogen in the potential range of water stability. Palladium is a unique noble metal owing to its ability to adsorbed and to absorb H, as well as to form compact and stable surface oxides. Anodic polarization of Pd results in the formation of a surface oxide. Thus, a great majority of anodic electrode processes takes place not at a metallic surface but at a surface covered with an oxide layer. Although thin surface oxides reveal metallic conductivity, the presence of O-containing species affects the electron transfer kinetics and the adsorption behaviour of reactants, intermediates, and products. Thus, the electrocatalytic properties of Pd electrodes, and the mechanism and kinetics of the reaction under consideration are strongly affected by the oxide layer, its thickness, chemical composition (Pd oxidation state and nature of O-containing species) and 3D structure, degree of oxide hydration, and electronic properties. This contribution presents an overview of the current understanding of electro-oxidation of Pd in aqueous acidic and basic electrolytes. In particular, it describes the formation of Pd oxides under various experimental conditions and discusses their chemical and physical nature. It examines the reduction of O-containing species present on Pd electrodes as well as the adsorption of anions and cations. Since Pd can undergo electrodissolution that results in material loss, the process is analyzed in relation to experimental parameters. Recent developments in the electrochemical behaviour of single-crystal Pd electrodes are discussed. Electrochemical parameters such as the potential of zero charge, potential of zero total charge and potential of zero free charge are of importance to the structure of the electric double layer; thus, their values are discussed in relation to the absence/presence of Pd surface oxides. Finally, various experimental procedures commonly used to determine the real surface area of Pd electrodes are outlined and compared.     

Aluminium and fluoride in hospital daily diets and in teas

The levels of aluminium and fluoride have been determined in hospital daily diets including breakfast, dinner and supper, as well as in black teas and herbal teas purchased from the local market. In tea, aluminium was determined directly in a sample solution by atomic absorption spectroscopy using nitrous oxide and an acetylene flame. For analysis of the hospital diet, samples containing lower levels of aluminium were analysed using a spectrophotometric method which measured aluminium in the form of a 8-hydroxyquinoline complex. Decomposition of the samples was achieved using a mixture of concentrated acids [nitric (HNO₃), perchloric (HClO₄) and sulphuric (H₂SO₄)] in platinum dishes. Fluoride was assayed by spectrophotometry using a microdiffusion procedure with a mixture of concentrated HClO₄ and silver sulphate, trace amounts of the released fluoride [as hydrogen fluoride (HF)] were trapped on the alkaline surface of a Petri dish and then determined in the form of an alizarin-fluoride complex. The mean level of aluminium found in hospital daily diets amounted to 21.3±12.3 mg and the mean level of fluoride was 1.38±1.12 mg per adult person. In the 16 samples of commercially available brands of black teas, the levels of aluminium and fluroide ranged from 445 to 1552 ppm (mean=897±264 ppm) and from 30 to 340 ppm (mean 141±85 ppm), respectively. In six herbal teas, the mean levels of aluminium and fluoride were lower, and amounted to 218.9±150.7 ppm and 6.0±6.9 ppm, respectively. This study has shown that concern about a high intake of aluminium and fluoride from these foods is unfounded.     

太阳能级硅电沉积用冰晶石熔盐的电导率和黏度

以热解碳化硼管作电导池,用固定电导池常数法研究由Na F-Al F3-Si O2构成的二元系和三元系熔盐的电导率;用扭摆法测定Na3Al F6-Si O2二元系的黏度。研究发现,所研究熔盐体系的电导率和黏度均与温度呈直线关系。Na3Al F6-Si O2二元系的电导率与Si O2含量关系曲线可分为0-10%和10%-40%（摩尔分数）两段,当SiO 2含量超过10%之后,电导率随着Si O2含量的增加而快速下降,而当Si O2含量小于10%时,电导率随着Si O2含量的增加而缓慢增加。在Si O2含量大于10%的冰晶石熔盐中添加少量的SiO 2,熔盐的黏度增加,但增加的趋势基本相同,这与熔盐中形成玻璃网状结构的离子团有关。当在冰晶石熔盐中继续增大Si O2含量到50%时,黏度发生急剧变化。     

Influence of alkali metal counterions on the charging behavior of poly(acrylic acid)

Charging of poly(acrylic acid) (PAA) in the presence of different alkali metal counterions was studied by precision potentiometric titration. The charging behavior can be described with a novel cylinder Stern model quantitatively. This model is based on the Poisson-Boltzmann equation in the cylinder geometry and a constant Stern capacitance. One finds an increasing cylinder radius with increasing mass of the alkali metal ion and a correspondingly decreasing Stern capacitance. The intrinsic ionization constants for the uncharged polymer are found to decrease with ionic strength, similarly to weak acids of low molecular mass.     

Determination of AKR-2 leakage beam and verification at iron and water arrangements

In this paper computational procedures and the experimental determination of the AKR-2 (Technical University Dresden) beam parameters are described. The calculations were performed using the MCNPX code (Pelowitz, 2002) and the nuclear data libraries ENDF/B VI.2., ENDF/B VII.0., JEFF 3.1., JENDL 3.3 and BROND 3. The nuclear data were processed using the NJOY code (MacFarlane and Muir, 1994). The measurements were performed with a two-parameter stilbene spectrometer (Bures et al., 2002).