Reactor 9 Interdigital Micro Mixer

The interdigital feed can be fed in a counter-flow or co-flow orientation the first principle is realized in metal/stainless steel or silicon/stainless steel devices [39, 41], the latter in glass chip devices [40, 44 6]. 

Right cut through the top part of the housing of the slit interdigital 3-D micro mixer comprising the slit-type focusing zone and the subsequent small channel to the outlet [40, 41). 

This chip version is typically made in glass and has the great advantage that the flow can be directly visualized [40,44—46]. Fabrication is achieved by photolithography and wet-chemical etching followed by thermal bonding of the plates covered with a thin layer of solder [47]. 

For the application referred to, the interdgital micro mixers were used on their own, without tubing attached, as reactors. Especially at low flow rates, the internal flow-through chamber acts as delay loop for providing a sufficient residence time. 

Mixer material Metal/stainless steel silicon /stainless steel glass Slit-type chamber 4.30 mm 500 pm initial width 150 pm 300 pm focused width depth 2.8 mm, 24 mm focusing length 126.7° expansion width expansion length expansion angle 

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Molar ratios of bromine to m-nitrotoluene ranging from 0.25 to 1.00 were applied. The reactants were contacted in an interdigital micro mixer followed by a capillary reactor. At temperatures of about 200°C nearly complete conversion is achieved (see Fig. 6). The selectivity to the target product benzyl bromide is reasonably high (at best being 85% at 200°C and higher being 80%). The main sideproduct formed is the nitro-substituted benzal bromide, i.e. the two-fold brominated side-chain product. 

Reactor 9 [R 9] Chip System with Triangular Interdigital Micro Mixer-Reaction Channel... 

This system is a chip version of three dimensional micro mixer-tube reactor setups [21]. It comprises a triangular interdigital micro mixer with a focusing zone that thins the multi-lamellae and a subsequent reaction channel that is surrounded... 

Figure4.9 Chip system with triangular interdigital micro mixer-reaction channel. First- (top) and second- (bottom) generation reactor designs [22],...

Reactor 19 [R 19] Slit-Type Interdigital Micro Mixer-Tube Reactor... 

Figure 4.21 Flow sheet of a laboratory triangular interdigital micro mixer-tube reactor set-up, used for an industrial application, the so-called Clariant process [4Xj.

Reactor type Triangular interdigital micro Mixer material Specialty glass (Foturan )... 

OS 1] [R 20] [P 1] A comparison of the selectivity/conversion behavior of an interdigital micro mixer-tube reactor with that of a mixing tee of about 1.5 mm inner diameter (and thus of larger internal dimensions) was made (Figure 4.39). For all data gathered, the performance of the micro mixer was much better, e.g. about 30% more selectivity at a given conversion [46]. 

OS 41a] [R 19] ]P 30] A study was undertaken to compare extended (1 h) processing in small vials (2 cm ) with short-time (100 s) continuous micro reactor and mini-batch (10 cm ) operation for 10 different substrates (C4-C8 alcohols) which were reacted with rhodium(I)-tris(m-sulfophenyl)phosphane [111]. The vials were either directly filled with the two phases yielding a bilayered fluid system with small specific interfaces or by interdigital micro mixer action yielding an emulsion with large specific interfaces. 

OS 63] [R 27] [R 18] [P 46] Using a slit-type interdigital micro mixer prior to a liquid/liquid reaction system improves the conversion to 80%, hence close to the kinetic limits [117]. This is an improvement over using a microgrid in front of the reactor (see the Section Conversion/selectivity/yield - benchmarking to batch processing/kinetics, above). 

OS 89] [R 19] [P 69] Using a special reactor configuration with an interdigital micro-mixer array with pre-reactor, subsequent tubing and a quench, a yield of 95% at 0 °C was obtained [127]. The industrial semi-batch process had the same yield at -70 °C. 

The authors applied this concept to both gas/liquid (see Figure 3.75) and liquid/ liquid systems (see Figure 3.76). This set-up consisted in the core of a tubular reactor with an interdigital micro mixer as dispersion unit (compare Figure 3.77). The peripheral equipment consisted of an automated pipetting robot, a fraction collector and a gas-chromatograph equipped with an automatic injector. 

One version of this reactor concept is the combination of the triangular interdigital metal/steel micro mixer (for a detailed description, see [R 18]) vhth conventional PTFE tubing (Figure 4.21) [46, 48]. 

M 39] [P 37] Using an azo-type competitive reaction, the selectivities were compared for the P- and V-type micro mixers having straight and oblique fluid injection, respectively [41]. In this way, laminar- and turbulent-flow mixing achieved by vertical interdigital microstructured mixers can be compared. The selectivities of the turbulent V-type mixer are better to some extent as compared with the P-type device however, neither approaches the characteristics of the ideal tubular reactor. The micro devices, however, are better than a conventional jet mixer. 

Figure 5.29 Special-type multi-purpose micro devices and mixing tee used for investigation of CO2 absorption. Comparison of their reactor performance as a function of the residence time. Micro bubble columns ( ) 1100 pm x 170 pm, (A) 300 pm x 100 pm and (T) 50 pm x 50 pm Interdigital mixer ( ) (40 pm) caterpillar mixer (A) (850 pm ramp) mixing tee (0) (1 mm) [5],...

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