Hermetic Gas‐tight Ceramic Microreactors

Meschke, Frank; Riebler, Gunter; Hessel, Volker; Schürer, Jochen; Baier, Tobias

doi:10.1002/ceat.200500004

Cited by 50 publications

(30 citation statements)

References 7 publications

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“…[3] This is the reason why SiC is used for many key components in chemical plants and has recently also been employed for the fabrication of gas-tight microreactors operating at high temperatures (700 8C) and harsh environments. [24] The corrosion resistance of sintered SiC is, like most ceramics, far better than of metals and even aggressive media such as concentrated acids or bases, HF, or chlorine gas have a negligible impact in terms of corrosion. [24] Based on these facts we have employed SiC vials for conducting microwave-assisted, aliphatic fluorine-chlorine exchange reactions using triethylamine trihydrofluoride (TREAT-HF, Et 3 N·3 HF) as a reagent.…”

Section: Controlling Thermal Runaways and Temperature Overshootsmentioning

confidence: 99%

“…[24] The corrosion resistance of sintered SiC is, like most ceramics, far better than of metals and even aggressive media such as concentrated acids or bases, HF, or chlorine gas have a negligible impact in terms of corrosion. [24] Based on these facts we have employed SiC vials for conducting microwave-assisted, aliphatic fluorine-chlorine exchange reactions using triethylamine trihydrofluoride (TREAT-HF, Et 3 N·3 HF) as a reagent. [36] TREAT-HF is a commercially available, colorless, hygroscopic liquid with a shelf life of at least one year and has been reported not to corrode borosilicate glassware at ambient conditions.…”

Section: Controlling Thermal Runaways and Temperature Overshootsmentioning

confidence: 99%

“…[16,18] Perhaps not surprisingly in this context, SiC ceramics have also been employed in the construction of microreactors for continuous-flow processing of strongly exothermic reactions, since the thermal effusivity of SiC is even higher than that of stainless steel. [24,25] Microwave field strength inside the SiC vials: A prime motivation for the development of the SiC vial was the attempt to shield the contents inside the vial from microwave irradiation, and therefore to be able to separate thermal from specific/nonthermal microwave effects (see below). [16] The fact that the electric field strength and the power density inside the SiC vial must be comparatively low can be derived from the following set of experiments.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Sintered Silicon Carbide: A New Ceramic Vessel Material for Microwave Chemistry in Single‐Mode Reactors

Gutmann

Obermayer

Reichart

et al. 2010

Chemistry A European J

104

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Silicon carbide (SiC) is a strongly microwave absorbing chemically inert ceramic material that can be utilized at extremely high temperatures due to its high melting point and very low thermal expansion coefficient. Microwave irradiation induces a flow of electrons in the semiconducting ceramic that heats the material very efficiently through resistance heating mechanisms. The use of SiC carbide reaction vessels in combination with a single-mode microwave reactor provides an almost complete shielding of the contents inside from the electromagnetic field. Therefore, such experiments do not involve electromagnetic field effects on the chemistry, since the semiconducting ceramic vial effectively prevents microwave irradiation from penetrating the reaction mixture. The involvement of electromagnetic field effects (specific/nonthermal microwave effects) on 21 selected chemical transformations was evaluated by comparing the results obtained in microwave-transparent Pyrex vials with experiments performed in SiC vials at the same reaction temperature. For most of the 21 reactions, the outcome in terms of conversion/purity/product yields using the two different vial types was virtually identical, indicating that the electromagnetic field had no direct influence on the reaction pathway. Due to the high chemical resistance of SiC, reactions involving corrosive reagents can be performed without degradation of the vessel material. Examples include high-temperature fluorine-chlorine exchange reactions using triethylamine trihydrofluoride, and the hydrolysis of nitriles with aqueous potassium hydroxide. The unique combination of high microwave absorptivity, thermal conductivity, and effusivity on the one hand, and excellent temperature, pressure and corrosion resistance on the other hand, makes this material ideal for the fabrication of reaction vessels for use in microwave reactors.

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Section: Controlling Thermal Runaways and Temperature Overshootsmentioning

confidence: 99%

Section: Controlling Thermal Runaways and Temperature Overshootsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Sintered Silicon Carbide: A New Ceramic Vessel Material for Microwave Chemistry in Single‐Mode Reactors

Gutmann

Obermayer

Reichart

et al. 2010

Chemistry A European J

104

View full text Add to dashboard Cite

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“…Yang et al (Yang et al, 2012a) summarized the existing literature references. The literature references assume isothermal behavior due to strong longitudinal conduction along the solid walls (Bier et al, 1993;Kee et al, 2011;Koyama and Asako, 2010a, b;Meschke et al, 2005). The influence of longitudinal conduction has been previously investigated by Yang et al (Yang et al, 2012b).…”

Section: Theoretical Backgroundmentioning

confidence: 99%

Heat transfer enhancement with gas-to-gas micro heat exchangers

Gerken

Brandner

Dittmeyer

2016

Applied Thermal Engineering

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A characterization of gas-to-gas micro heat exchangers has been performed in terms of pressure drop behavior and heat transfer performance. The gas-to-gas micro heat exchangers differ by partition wall material, partition wall thickness and flow arrangement. The pressure drop behavior has been analyzed due to the pressure losses in different sections of the gas-to-gas micro heat exchangers. Increased pressure losses in front of and behind the micro channels have been detected due to modified geometries in the inlet and outlet distribution chambers. The heat transfer performance has been determined in terms of thermal effectiveness. The comparison among different partition wall materials and partition wall thicknesses showed no significant criteria of the influence of thermal conductivity on the thermal effectiveness. An assessment due to an overall heat exchanger effectiveness has been performed to compare the gas-to-gas micro heat exchangers. For this purpose, the overall exergy loss has been calculated by combination of thermal effectiveness and pressure losses. A strong impact of the exergy loss due to pressure drop has been detected which influences the overall exergy loss of the gas-to-gas micro heat exchangers.

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“…Although these materials can reach the requirement of high heat flux, the manufacturing capability of these materials still needs to be investigated to yield the desired plate (and later the desired annulus) size which can be used in the CAEC system. Both glass and SiC are used for special microreactors and micro heat exchangers, e.g., for handling corrosive media [28], as the conductive plate in the last section of this paper.…”

Section: Material Systemic Boundary Conditions and New Design Approachmentioning

confidence: 99%

3D Analysis of Heat Transfer Intensification by Re‐Entrance Flow Pin‐Fins Microstructures with a Highly Thermal‐Conductive Plate

et al. 2011

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Joule heat-induced hot-spot formation sets severe limits in the operation of continuous annular electrochromatography (CAEC), a new concept for preparative separation as an analog to analytical capillary electrochromatography (CEC). This may lead to eluent flow perturbance, even to boiling, which would massively weaken separation efficiency and may even hamper the stationary phase used for separation. For reasons of system integration and high-efficiency heat transfer, micro flow heat exchangers are considered with a separate coolant flow. A 3D numerical analysis of the heat transfer of water single-phase laminar flow in a square microchannel and different arrays of micro pin-fins was carried out using COMSOL Multiphysics. Several advanced materials with low electric conductivity and at the same time with high heat conductivity were put forward to be used in the CAEC system. As essential design point, it is proposed to constitute the micro heat exchanger from two different parts of the CAEC system, namely a microstructured pin-fins plate and a so-called conductive plate.

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Hermetic Gas‐tight Ceramic Microreactors

Cited by 50 publications

References 7 publications

Sintered Silicon Carbide: A New Ceramic Vessel Material for Microwave Chemistry in Single‐Mode Reactors

Sintered Silicon Carbide: A New Ceramic Vessel Material for Microwave Chemistry in Single‐Mode Reactors

Heat transfer enhancement with gas-to-gas micro heat exchangers

3D Analysis of Heat Transfer Intensification by Re‐Entrance Flow Pin‐Fins Microstructures with a Highly Thermal‐Conductive Plate

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