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- Explosion (4)
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- O-xylene oxidation (2)
- Oxidation (2)
- Partial oxidation (2)
Organisationseinheit der BAM
- 1 Analytische Chemie; Referenzmaterialien (2)
- 1.4 Prozessanalytik (2)
- 1.6 Anorganische Referenzmaterialien (2)
- 1.1 Anorganische Spurenanalytik (1)
- 1.2 Biophotonik (1)
- 1.7 Organische Spuren- und Lebensmittelanalytik (1)
- 4 Material und Umwelt (1)
- 4.2 Material-Mikrobiom Wechselwirkungen (1)
- 6 Materialchemie (1)
- 6.1 Oberflächen- und Dünnschichtanalyse (1)
Eingeladener Vortrag
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Es wird eine Methode zur sicherheitstechnischen Untersuchung von Mikroreaktoren und mikrostrukturierten Komponenten, die im Explosionsbereich betrieben werden sollen, vorgestellt. Mikrostrukturierte Reaktoren sind nicht inhärent sicher, wenngleich der Bereich der sicheren Betriebsbedingungen gegenüber konventionellen Reaktoren erweitert ist. Der Explosionsbereich kann durch die Mikrostrukturen eingeengt werden. Am Beispiel von Ethylen/Sauerstoff-Gemischen und Ethylen/N2O-Gemischen wird hinsichtlich der Ausbreitung von Detonationen durch Kapillarrohre gezeigt, dass die sogenannte λ/3-Regel angewandt werden kann. Darüber hinaus werden erste Ergebnisse der Untersuchung der Ausbreitung von Explosionen durch einen Mikroreaktor mit rechteckigem Strömungskanal vorgestellt.
The heterogeneously catalyzed selective gas phase oxidation of o-xylene was investigated, using a
microstructured fixed bed reactor, inside of the explosion regime. The reaction was carried out with high
amounts of o-xylene in air and stoichiometric with oxygen using a V2O5/TiO2-catalyst prepared through
grafting. There were no significant losses in the selectivity to phthalic anhydride observable, during the
measurements in the explosion regime, with feed compositions of up to 7 vol% o-xylene. Also the
space-time yield was up to 2.3 times higher in comparison to conventional reaction conditions. An
increase of the selectivity to total oxidation products was observed at higher o-xylene concentrations
between 10 and 25 vol% o-xylene, which possibly was caused by the formation of a hotspot. The
investigation of the used catalyst revealed a thermally induced deactivation due to phase transition of
anatase into rutil and formation of crystalline vanadium oxide. Despite that expected hotspot at high oxylene
concentrations, there was no ignition or explosion of the gas mixture observable.
Two types of copper samples, compact certified copper reference materials and calibration samples prepared from liquid doped, pressed copper powders, were studied in terms of accuracy of obtained calibration functions originating from infrared spark ablation. Additionally, corresponding particle size distributions of the aerosols from infrared spark ablation were recorded. It is shown that the differences in quantification results, originating from the two sets of calibration functions, could not mainly be ascribed to different particle size distributions of the two copper sample types. Possible other causes, as different ablation rates, parts of melting and differences of the chemical constitutions of the two sample types were explored.
A method for the determination of safety properties for micro reactors and micro structured components is presented.
Micro structured reactors are not inherently safe but the range of safe operating conditions of micro reactors are
extended since the explosion region is reduced. The λ/3 rule was demonstrated to be applicable to micro scale
tubes for stoichiometric mixtures of ethane–oxygen and ethane–nitrous oxide. Furthermore first results from an investigation concerning detonation propagation through a micro reactor of non-ideal geometry are shown. Initial
pressure investigated is ranging from low pressure up to 100 kPa.
The present contribution reports on specific aspects of safety engineering in heterogeneously catalysed oxidation reactions. Results for ethene-oxygen-mixtures in a continuous-flow micro reactor are reported related to the safety issues of the ethylene oxide process. Initial pressure is ranging from below 1 bar up to 10 bar at initial temperatures ranging from room temperature up to 673 K. Micro structured reactors offer an extended range of operating conditions. The key issue to be discussed in the present contribution is how to safely operate a micro reactor at conditions in conventional devices to be characterised as inside the explosion region. Within certain limits suppression of explosion inside a micro reactor can be achieved.
This holds true for chain reactions as well as runaway reactions. Nevertheless it is not possible to safely operate micro structured reactors at any condition. Therefore, explosion propagation through a Micro structured reactor and initiation of gas phase explosions by hot spots inside the reactor were investigated.
The investigation methods applied are subject to actual standardization.
The interaction of TS-1 with gaseous hydrogen peroxide at temperatures above 373 K has been investigated by in situ EPR measurements. Treatment of TS-1 with hydrogen peroxide in the gas phase leads to a strong EPR signal, assigned to the Ti(IV)-superoxide species. In contrast to investigations with liquid hydrogen peroxide,
here only one Ti(IV)-superoxide species could be detected in the EPR spectrum. The time constant of the reaction of the Ti(IV)-superoxide species detected by in situ EPR measurements was much larger than that observed for the rate of consumption of propane or propene via gas chromatographic analysis. Thus, we conclude that the Superoxide species may take part in the oxidation reaction (via side reactions or the formation of unselective products), but is probably not the main responsible species in the oxidation of propane or propene.
The traceabiiity requirements for certification analyses of reference materials are much more stringent than for routine analysis, where certified matrix reference materials (CRM) can be used for calibration and to establish traceabiiity. Although the ISO-Guides related to CRM production and certification are not fully clear concerning calibration, many established CRM-producers do not accept matrix-CRMs for calibration in case of certification analyses, e.g. to avoid circular reasoning. These requirements limit the methods used for certification to those that can be calibrated using Standards of known high purity and stoichiometry or mixtures of such Standards. Powerful solid sampling techniques such as glow discharge mass spectrometry (GD-MS) or spark-optical emission spectrometry (SOES), where usually compact CRMs are used for calibration, seem not be applicable for certification analyses. Especially GD-MS is a powerful tool for trace element determination of solid samples. Beside metallic impurities the use of specific gas mixtures enables also the determination of interesting nonmetallic impurities such as sulfur and phosphorus. Within BAM a calibration approach, was developed which enables to use mixtures of Standards of known high purity and stoichiometry also for GD-MS. Analogue to matrix adaption in solution based techniques, the calibration approach is based on doped pressed powder pellets.
Approach and application on the certification analyses of copper and Steel CRMs are presented.
For more than 110 years, BAM has been producing reference materials for a wide range of application fields. With the development of new analytical methods and new applications as well as continuously emerging more stringent requirements of laboratory accreditation with regard to quality control and metrological traceability, the demand and requirements for reference materials are increasing. This trend article gives an overview of general developments in the field of reference materials as well as developments in selected fields of application in which BAM is active. This includes inorganic and metal analysis, gas analysis, food and consumer products, and geological samples. In addition to these more traditional fields of application, developments in the areas of optical spectroscopy, particulary fluorescence methods, and nanomaterials are considered.