The kinetics of N 2 O decomposition over a commercial iron zeolite catalyst was determined in an integral laboratory reactor.The formal kinetic equation developed permits a very good description of the observed rate as a function of temperature and the concentrations of N 2 O, NO and H 2 O. The influence of mass transfer phenomena on the reaction rate was investigated experimentally by using different catalyst particle sizes. A reactor model taking into account internal and external mass transfer resistances, axial dispersion and pressure drop was developed. Reactor simulations for different configurations revealed that random packings of catalyst extrudates must be placed in radial-flow reactors to limit the pressure drop.Honeycomb monolith catalysts are attractive alternative geometries because they allow both better utilization of active material and the design of more compact reactors. Figure 6. Specific gas inlet cross-sectional area as a function of reactor temperature for catalyst extrudates and honeycomb monoliths. N 2 O conversion: 90 %; pressure drop: 40 mbar.
Nitric acid is a key chemical for many industries. Some 60 million tons are produced annually, of which 80% goes into nitrate production for fertilizers and explosives, the latter principally for mining. Other significant uses include the manufacture of intermediates for polyurethane and polyamide production. This article covers the birth and development of the Ostwald nitric acid manufacturing process and describes the modern commercial production methods for both “weak” (≤68 wt%) and “strong” (∼69–99 wt%) nitric acid. An overview of the present state of knowledge is given about the main chemical process steps of ammonia oxidation and nitrogen oxide absorption. Nitric acid plants are emitters of NO x and N 2 O, and the currently available technologies to limit these to their permitted levels are discussed. Further information includes health and safety aspects, shipping and handling regulations, and economics. The article concludes with a description of alternative production technologies and a brief outlook on the future of nitric acid.
ter sind für die Reaktionskinetik von entscheidender Bedeutung.Die Messungen dienten als Validierungsgrundlage für detaillierte Reaktionsmechanismen der einzelnen Precursoren aus der Literatur. Auf Basis von Sensitivitätsanalysen wurden die Mechanismen unter Verwendung neuerer kinetischer Daten verbessert. Im Falle des Caprolactams wurde ein neuer Mechanismus abgeleitet. Mit dem Gesamtmodell, das alle Teilmechanismen beinhaltet, war es möglich die Charakteristika der Messungen sehr gut wiederzugeben. Der Gesamtmechanismus steht in detaillierter bzw. reduzierter Form zur numerischen Simulation der Abfallverbrennung zur Verfügung. Mit der Simulation können gezielt Reduktionsstrategien für die NO x -Bildung im Feuerraum erarbeitet werden.
mining of accumulated data, preferably in the direction of predictive or focusing models (the Model stage). While various computational approaches to each of these two stages are already in routine use, there remain substantial opportunities for innovation.To illustrate the necessary coupling between the four high-throughput experimentation stages, we illustrate interrelationships between catalyst synthesis and processing approaches (the Make stage) and catalyst testing (the Test stage) for a small number of examples from our own development programs. Our emphasis is often on automating or parallelizing techniques, for example, for catalyst synthesis that are comparable with those applied to produce catalysts on much larger scales. Similarly, catalytic testing conditions and reactor geometries are often designed to be informative of catalyst properties that are relevant to the envisaged end-use application.The need for new catalysts and materials has never been satisfied by conventional methods. Chemical diversity is much too large to be explored systematically. In order to provide the expected results, combinatorial chemistry requires the combination of library preparation, characterization, identification of the desired properties and retrievable collection of the accumulated data in an intelligent data base. We have been engaged in the preparation and testing of catalyst libraries by liquid phase techniques for a variety of applications. Several techniques for the identification of catalytic properties have been developed in our laboratory. Emissivity corrected IR thermography is used to identify catalytic activity of library components through the heat of reaction with high efficiency. Although slower, but more detailed information is obtained with spatially resolved mass spectrometry and spatially resolved gas chromatography. Combinatorial chemistry applied to the discovery of new catalysts and materials can provide new lead structures demonstrated on examples of new CO-oxidation cataysts and new hydroisomerization catalysts. Bei der Herstellung von Salpetersäure resultiert ein mit Stickoxiden beladenes Abgas, welches neben Stickstoffmonoxid NO und Stickstoffdioxid NO 2 (zusammen bezeichnet als NO x ) nicht unerhebliche Mengen an Lachgas N 2 O enthält. Seitdem jedoch Lachgas als relevantes Treibhausgas (Wirkung auf den Treibhauseffekt ca. 300-mal stärker als die von CO 2 ) erkannt wurde und auch im Kyoto-Protokoll als solches benannt ist, wurden in Deutschland nun erstmalig Grenzwerte für Lachgasemissionen von Salpetersäure-Anlagen in der TA-Luft festgeschrieben. Die Uhde GmbH, als ein weltweit führendes Unternehmen in der Salpetersäure-Technologie, stellte sich daher die Aufgabe, ein Verfahren zur Beseitigung von N 2 O im Salpetersäure-Prozess zu entwickeln, welches nicht nur hohe Abbauraten für N 2 O erzielt, sondern darüber hinaus in einfacher Weise ohne Beeinträchtigung des Produktionsprozesses in diesen integriert werden kann. Insbesondere sollte die Entfernung des N 2 O mit der ebenfalls notwendigen De...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.