Microreactors

Ehrfeld, W.; Hessel, Volker; Löwe, Holger

doi:10.1002/3527601953

Cited by 853 publications

(348 citation statements)

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“…A feature of microreactors that is currently exploited is the presumption that "smaller is safer" [7], i.e. chemical processes at extreme pressure and temperature conditions and with toxic or explosive species can be studied without the safety issues associated with larger scale systems [8][9][10]. In this paper we focus on chemistry under high-pressure conditions, using a reaction system based on a microfluidic glass chip with a volume in the hundreds of nanoliter range.…”

Section: Introductionmentioning

confidence: 99%

Fabrication, mechanical testing and application of high-pressure glass microreactor chips

Tiggelaar¹,

Benito‐Lopez²,

Hermes³

et al. 2007

Chemical Engineering Journal

115

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The design, fabrication and high-pressure performance of several in-plane fiber-based interface geometries to microreactor chips for highpressure chemistry are discussed, and an application is presented. The main investigated design parameters are the geometry of the inlet/outlet structure, the manner in which top and bottom wafer are bonded and the way the inlets/outlets turn over into the microfluidic channels.Destructive pressure experiments with H 2 O and liquid CO 2 showed that the maximum pressure that the proposed inlet/outlet structures can withstand is in the range of 180-690 bar. The optimal geometry for high-pressure microreactor chips is a tubular structure that is etched with hydrofluoric acid (HF) and suitable for fibers with a diameter of 110 m. These inlets/outlets can withstand pressures up to 690 bar. On the other hand, small powderblasted inlets/outlets that are smoothened with HF and with a sharp transition towards the flow channels are adequate for working pressures up to 300 bar.Microreactor chips with tubular inlet/outlet geometries were used for studying the formation of the carbamic acid of N-benzylmethylamine and CO 2 . These chips could be used for pressures up to 400 bar without problems/failure, thereby showing that these micromachined microreactor chips are attractive tools for performing high-pressure chemistry in a fast and safe way.

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Section: Introductionmentioning

confidence: 99%

Fabrication, mechanical testing and application of high-pressure glass microreactor chips

Tiggelaar¹,

Benito‐Lopez²,

Hermes³

et al. 2007

Chemical Engineering Journal

115

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“…They also bring an increased surface area-to-volume ratio that is useful if the particles within the bed are to act as an adsorbent or catalyst (Kiwi-Minsker andRenken, 2005, Oleschuk et al, 2000). The small test volumes and short residence times also make µPBs ideal for rapid, highthroughput catalyst screening (Cao et al, 2007, Ehrfeld et al, 2000, and in the liquid chromatography context in the pharmaceutical sector (Jung et al, 2009). They are also of relevance to micro-fluidized beds (Zivkovic et al, 2013a, Zivkovic et al, 2013b, Doroodchi et al, 2012, Doroodchi et al, 2013 in that they are clearly formed from packed beds.…”

Section: Introductionmentioning

confidence: 99%

A new method for reconstruction of the structure of micro-packed beds of spherical particles from desktop X-ray microtomography images. Part A. Initial structure generation and porosity determination

Kashani

Živković

Elekaei

et al. 2016

Chemical Engineering Science

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Citation: NAVVAB KASHANI, M. ...et al., 2016. A new method for reconstruction of the structure of micro-packed beds of spherical particles from desktop X-ray microtomography images. Part A. Initial structure generation and porosity determination. Chemical Engineering Science, 146, Additional Information:• This paper was accepted for publication in the journal Chemical En- AbstractMicro-packed beds (µPBs) are seeing increasing use in the process intensification context (e.g. micro-reactors), in separation and purification, particularly in the pharmaceutical and bio-products sectors, and in analytical chemistry. The structure of the stationary phase and of the void space it defines in such columns is of interest because it strongly influences performance. However, instrumental limitations -in particular the limited resolution of various imaging techniques relative to the particle and void space dimensions -have impeded experimental study of the structure of µPBs. We report here a new method that obviates this issue when the µPBs are composed of particles that may be approximated by monodisperse spheres. It achieves this by identifying in successive cross-sectional images of the bed the approximate centre and diameter of the particle cross-sections, replacing them with circles, and then assembling them to form the particles by identifying correlations between the successive images. Two important novel aspects of the method proposed here are it does not require specification of a threshold for binarizing the images, and it preserves the underlying spherical geometry of the packing. The new method is demonstrated through its application to a packing of a near-monodispersed 30.5 µm particles of high sphericity within a 200 µm square cross-section column imaged using a machine capable of 2.28 µm resolution. The porosity obtained was, within statistical uncertainty, the same as that determined via a direct method whilst use of a commonly used automatic thresholding technique yielded a result that was nearly 10% adrift, well beyond the experimental uncertainty. Extension of the method to packings of spherical particles that are less monodisperse or of different regular shapes (e.g. ellipsoids) is also discussed.

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“…11,12 Despite enormous progress in using microfluidic reactors for the synthesis of nanoparticles, crystallinity of metal oxide nanoparticles has only been demonstrated in systems where the reactants are maintained at high temperatures for at least 1 to 30 minutes. This 45 can be accomplished through the use of a resistive heater, oil bath or oven, which heats either the entire device, or just the collection tube.…”

Section: Introductionmentioning

confidence: 99%

Microwave dielectric heating of non-aqueous droplets in a microfluidic device for nanoparticle synthesis

et al. 2013

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We describe a microfluidic device with an integrated microwave heater specifically designed to dielectrically heat non-aqueous droplets using time-varying electrical fields with the frequency range between 700 and 900 MHz. The precise control of frequency, power, temperature and duration of the applied field opens up new vistas for experiments not attainable by conventional microwave heating. We 10 use a non-contact temperature measurement system based on fluorescence to directly determine the temperature inside a single droplet. The maximum temperature achieved of the droplets is 50°C in 15 ms which represents an increase of about 25°C above the base temperature of the continuous phase. In addition we use an infrared camera to monitor the thermal characteristics of the device allowing us to ensure that heating is exclusively due to the dielectric heating and not to other effects like non-dielectric 15 losses due to electrodes or contacts imperfection. This is crucial for illustrating the potential of dielectric heating of benzyl alcohol droplets for the synthesis of metal oxides. We demonstrate the utility of this technology for metal oxide nanoparticle synthesis, achieving crystallization of tungsten oxide nanoparticles and remarkable microstructure, with a reaction time of 64 ms a substantial improvement over conventional heating methods.

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Microreactors

Cited by 853 publications

References 0 publications

Fabrication, mechanical testing and application of high-pressure glass microreactor chips

Fabrication, mechanical testing and application of high-pressure glass microreactor chips

A new method for reconstruction of the structure of micro-packed beds of spherical particles from desktop X-ray microtomography images. Part A. Initial structure generation and porosity determination

Microwave dielectric heating of non-aqueous droplets in a microfluidic device for nanoparticle synthesis

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