Micro-mixers

By the use of microstructured mixers, pigment and other particulate syntheses can be improved. In this way, finer particles with more uniform size distribution were yielded for the commercial azo pigment Yellow 12 (see Fig. 2) [11]. The particles formed in the microstructured mixer have better optical properties such as the glossiness or transparency at similar tinctorial power. Since the micro-mixer made pigments have more intense colour, lower contents of the costly raw material in the commercial dye products can now be employed which increases the profitability of the pigment manufacture. 

Fig. 2 Particle size distributions, (by volume) of the impeller-batch (top) and the micro-mixer-continuous-flow (bottom) processes when manufacturing the pigment Yellow 12. The cumulative distributions are given as well [11]...

Fig. 6 High p,T operation for the radical side-chain bromination of m-nitro toluene in a micro-mixer-reactor setup. The large increase in operational temperature increases conversion at good selectivities, which tend to decline slightly with temperature. The two-fold substituted product, m-nitro toluene benzal bromide, is formed in larger amounts at temperatures above 200°C (IMM, unpublished results)...

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. 

Figure 1.5 Photograph of the liquid-flow splitting unit for liquid/liquid processing with three tanks and six separation-layer micro mixers [8].

Figure 1.19 Semi-analytical calculation of the speed of mixing in an advanced interdigital micro mixer, named SuperFocus, and comparison with previously developed interdigital micro mixers [120],...

Figure 1.20 Periodic concentration profile of a regular multi-lamellar pattern in a rectangular interdigital micro mixer, determined by photometric-type analysis [119].

As a kind of specialty solutions for the real hard cases where fouling is intense and unavoidable, IMM first proposed ideas to develop special micro mixers for fouling-intense reactions and conducted feasibility tests, among them very fast organic reactions with spontaneous precipitation such as the amidation of acetyl chloride in THF [134]. The Forschimgszentrum Karlsruhe developed special anti-foul-ing coatings in cooperation with partners [135]. 

Finally, yield improvements were also reported for industrial process developments. For the Merck Grignard process, a yield of 95% was obtained by a micro mixer-based process, while the industrial batch process (6 m stirred vessel) had only a 72% yield (5 h, at -20 °C) [11]. The laboratory-scale batch process (0.5 1 flask ... 

Figure 2.40 Zigzag micro mixer with concentration field (left) and flow stream lines (right) obtained from a CFD simulation for a Reynolds number of 38. In [135] a sawtooth geometry of larger amplitude was considered and distinctive recirculation zones were found only at Reynolds numbers larger than 80.

Figure 2.42 Micro mixer geometry with staggered groove structures on the bottom wall, as considered in [137], The top of the figure shows a schematic view of the channel cross-section with the vortices induced by the grooves. At the bottom, confocal micrographs showing the distribution of two liquids over the cross-section are displayed.

Figure 2.47 Micro mixer based on the excitation of an electro-osmotic flow around a cylinder by an oscillatory electric field (top). The bottom of the figure shows particle traces on both sides of the liquid/liquid interface with no electric field (above) and with the electric field switched on (below), as described in [145].

Figure 2.61 Formation of water droplets in silicone oil in a multilamination micro mixer.

Figure 2.63 Droplet formation in a micro mixer for a wall contact angle of 40° (left) and 90° (right), with silicone oil being the continuous and water the disperse phase.

Reactor 2 [R 2] Steel Multi-plate-stack Reactor with Micro Mixer... 

The whole set-up for partial oxidation comprises a micro mixer for safe handling of explosive mixtures downstream (flame-arrestor effect), a micro heat exchanger for pre-heating reactant gases, the pressure vessel with the monolith reactor, a double-pipe heat exchanger for product gas cooling and a pneumatic pressure control valve to allow operation at elevated pressure [3]. 

Pre-heater (with micro mixer) material Stainless steel Operating pressure 1 har... 

This class is the simplest of all micro reactors and certainly the most convenient one to purchase, but not necessarily one with compromises or reduced fimction. HPLC or other tubing of small internal dimensions is used for performing reactions. There are many proofs in the literature for process intensification by this simple concept. As a micro mixer is missing, mixing either has to be carried out externally by conventional mini-equipment or may not be needed at all. The latter holds for reactions with one reactant only or with a pre-mixed reactant solution, which does not react before entering the tube. 

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 11 [R 11] Bifurcation-distributive Chip Micro Mixer... 

Reactor type Bifurcation-distributive chip micro mixer ... 

Figure 4.12 On-line coupling of the bifur-cation-distributive chip micro mixer to a Perseptive Biosystems Mariner TOF-MS [25],...

Reactor 17 [R 17] Fork-like Chip Micro Mixer-Tube Reactor... 

Central part of this reaction unit is a split-recombine chip micro mixer made of silicon based on a series of fork-like channel segments [32-36]. Standard silicon micro machining was applied to machine these segments into a silicon plate which was irreversibly joined to a silicon top plate by anodic bonding (Figure 4.16). 

Reactor type Fork-like chip micro mixer-tube reactor Characteristic structure of the mixing stage G structure ... 

Micro mixer material Silicon Outer device dimensions 40 X 25 X 1.3 mm ... 

Channel width depth of micro mixer 360 pm 250 pm (triangular-shaped) ... 

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