Comparison of Ag/Al— and Ag/α-AI2O3 Catalytic Surfaces for the Partial Oxidation of Ethene in MicroChannel Reactors

Kursawe, Ansgar; Hönicke, Dieter

doi:10.1007/978-3-642-56763-6_25

Cited by 13 publications

(4 citation statements)

References 11 publications

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“…Similar to the oxi-hydrogen reaction case, safe microreactor operation under (conventionally) explosive conditions was established for the partial oxidation of ethylene to give ethylene oxide, even using undiluted reactant mixtures [133][134][135], Scheme 38.…”

Section: Oxidation Of Ethylene Oxide and Maleic Anhydridementioning

confidence: 99%

Novel Process Windows – Gate to Maximizing Process Intensification via Flow Chemistry

2009

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Driven by the economics of scale, the size of reaction vessels as the major processing apparatus of the chemical industry has became bigger and bigger [1,2]. Consequently, the efforts for ensuring mixing and heat transfer have also increased, as these are scale dependent. This has brought vessel operation to (partly severe) technical limits, especially when controlling harsh conditions, e.g., due to large heat releases. Accordingly, processing at a very large scale has resulted in taming of the chemistry involved in order to slow it down to a technically controllable level. Therefore, reaction paths that already turned out too aggressive at the laboratory scale are automatically excluded for later scale-up, which constitutes a common everyday confinement in exploiting chemical transformations. Organic chemists are barely conscious that even the small-scale laboratory protocols in their textbooks contain many slow, disciplined chemical reactions. Operations such as adding a reactant drop by drop in a large diluted solvent volume have become second nature, but are not intrinsic to the good engineering of chemical reactions. These are intrinsic to the chemical apparatus used in the past. In contrast, today's process intensification [3][4][5][6][7][8][9][10][11][12] and the new flow-chemistry reactors on the micro-and milli-scale allow such limitations to be overcome, and thus, enable a complete, ab-initio type rethinking of the processes themselves. In this way, space-time yields and the productivity of the reactor can be increased by orders of magnitude and other dramatic performance step changes can be achieved. A hand-in-hand design of the reactors and process re-thinking is required to enable chemistry rather than subduing chemistry around the reactor [40]. This often leads to making use of process conditions far from conventional practice, under harsh environments, a procedure named here as Novel Process Windows. Starting Point: Novel Process WindowsIntensify Rather than OptimizeThe aim of the following introductory remarks, and the paper as whole, is to make sensible -while everyone in the field would agree that microstructured reactors and micro-process technology [3-12] form a major direction within process intensification -that the exploitation of such innovation can still profit considerably by joining both concepts. It is frequently thought that the use of a microstructured reactor automatically and implicitly results in process intensification; simply because this is a major direction within process intensification and since the latter is also concerned with apparatus developments. This is only partly true and actually ignores significant chances for process breakthrough. In many investigations, the use of a microstructured reactor is still more concerned with process optimization, which is involves a slight to moderate improvement of processes using classical paths, in particular with the same or similar chemical and processing protocol. Often, the most radical and innovative step is the

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Section: Oxidation Of Ethylene Oxide and Maleic Anhydridementioning

confidence: 99%

Novel Process Windows – Gate to Maximizing Process Intensification via Flow Chemistry

2009

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“…The functionality of both the silver and alumina sites is very different in these applications. For epoxidation large silver particles on a low surface area alumina is required, while in the case of lean NO x reduction a highly dispersed silver phase on a high surface area alumina is beneficial or even needed. − …”

Section: Introductionmentioning

confidence: 99%

Influence of the Carbon–Carbon Bond Order and Silver Loading on the Formation of Surface Species and Gas Phase Oxidation Products in Absence and Presence of NO_x over Silver-Alumina Catalysts

et al. 2012

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The influence of carbon-carbon bond order, here systematically represented by prototypical C2H6, C2H4 and C2H2, on the formation of oxidation products and surface species in the absence and presence of NO has been studied for silver-alumina catalysts with different silver loadings (2 and 6 wt%). The catalysts were prepared with a sol-gel method including freeze-drying, which results in small silver species uniformly distributed throughout the alumina matrix. The performance of the catalysts was investigated by temperature programmed extinction-ignition experiments using a continuous gas flow reactor. The evolution of surface species during reactant step-response experiments was studied in situ by diffuse reflection Fourier transform infrared spectroscopy. The results show that activation for oxidation generally proceeds more easily with increasing bond order of the hydrocarbon. For example, C2H2 shows the highest conversion at low temperatures. Furthermore, the use of hydrocarbons with high bond order, i.e., C2H2, as reductant for lean NOx reduction results not only in the highest peak activity but also in considerable high activity in a wide temperature range mainly thanks to high activity at low temperature. With increasing silver loading, the oxidation reactions are favored such that both the hydrocarbon and NO activation occur at lower temperatures. Several types of adsorbates, e.g., carbonate, acetate, formate, enolic and isocyanate/cyanide surface species, are present on the catalyst during reaction. Generally the nature of the surface species and likely also the surface processes are more influenced by the carbon-carbon bond order than the silver loading. 3 This needs to be considered when designing catalysts for emission control systems. Especially for applications using homogeneous fuels with short hydrocarbons, this may provide opportunities to tailor the catalyst functionality for the needs at hand.

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“…The performance of different microreactors for ethylene oxide synthesis is reported in Table 2 ), Kursawe and Honicke [80] reported safe working within the explosion regime for ethylene oxide synthesis. It was reported that the thickness of the Ag coating on Al had a strong infl uence on the conversion and selectivity behavior ( Figure 14 ).…”

Section: Microreactor Technologymentioning

confidence: 99%

Process intensification in green synthesis

Kumar

Nigam

2012

Green Processing and Synthesis

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In the past few decades there has been an extensive increase in the research for green synthesis processes due to environmental concerns, industrial safety and sustainable development, which makes it an attractive alternative to the conventional synthesis processes. The interest of researchers in the green synthesis processes highlights the importance of understanding the mechanism and the fundamental differences between the different processes. The number of publications in the fi eld of " Green Synthesis " in journals, proceedings, patents, etc. has increased by almost 20 times from 2001 to 2010. The published reports are mainly concerned with green synthesis with catalytic processes, less harmful solvents and process intensifi ed techniques. In the present article, the technological development efforts in the area of green synthesis are summarized. Various techniques for green synthesis process intensifi cation are discussed, e.g., mixers, microreactors, spin disc reactor, oscillated fl ow reactors, microwave irradiation, ultrasonication, multifunctional membranes and coiled fl ow inverter. The applications of green synthesis processes for biofuel, nanoparticle, ionic liquids and pharmaceutical production are also discussed.

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Comparison of Ag/Al— and Ag/α-AI2O3 Catalytic Surfaces for the Partial Oxidation of Ethene in MicroChannel Reactors

Cited by 13 publications

References 11 publications

Novel Process Windows – Gate to Maximizing Process Intensification via Flow Chemistry

Novel Process Windows – Gate to Maximizing Process Intensification via Flow Chemistry

Influence of the Carbon–Carbon Bond Order and Silver Loading on the Formation of Surface Species and Gas Phase Oxidation Products in Absence and Presence of NO_x over Silver-Alumina Catalysts

Process intensification in green synthesis

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Comparison of Ag/Al— and Ag/α-AI2O3 Catalytic Surfaces for the Partial Oxidation of Ethene in MicroChannel Reactors

Cited by 13 publications

References 11 publications

Novel Process Windows – Gate to Maximizing Process Intensification via Flow Chemistry

Novel Process Windows – Gate to Maximizing Process Intensification via Flow Chemistry

Influence of the Carbon–Carbon Bond Order and Silver Loading on the Formation of Surface Species and Gas Phase Oxidation Products in Absence and Presence of NOx over Silver-Alumina Catalysts

Process intensification in green synthesis

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Product

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Influence of the Carbon–Carbon Bond Order and Silver Loading on the Formation of Surface Species and Gas Phase Oxidation Products in Absence and Presence of NO_x over Silver-Alumina Catalysts