Mixing multilamination

Details on microfabrication and on the internals in the stacked plates have not been substantially disclosed so far. Accordingly, no information on the mechanisms of mass and heat transfer was reported. In one version, geometrically focused multilamination is used for mixing liquid streams [55]. 

As industrial relevant Friedel-Crafts reaction, the synthesis of Bisphenol-F, a material for epoxy resin, from phenol and formaldehyde was chosen [57]. This reaction involves formation of higher order condensates such as tris-phenols. To minimize the latter, the molar ratio of phenol to formaldehyde is set to a very high value (30-40), which is more than 15 times larger than the amount theoretically necessary. Three types of micromixers were used. These are a T-shaped mixer with 500 pm inner diameter, a multilaminating interdigital micromixer with 40 pm channels and a so-called self-made K-M micromixer with center collision mixing. 

The main use of PVC is for intravenous bags. However, PVC has been used in the controlled release of volatile insecticides, herbicides, pheromones, and perfumes by diffusion through a PVC membrane of multilaminated stripes. A monolithic matrix device of PVC can be prepared by mixing PVC particles with a suitable plasticizer and an active agent, followed by heating of the mixture in a mold. A solid PVC matrix is obtained from the subsequent cooling. 

When a T-shaped mixer is used, the product selectivity is essentially the same as for the macrobatch reactor (Scheme 6.4). The use of the YM-1 mixer, a splitting-and-recombination-type micromixer (see Chapter 7), increases the selectivity, however, a significant amount of dialkylation product is still produced. The use of the IMM multilamination-type micromixer results in excellent selectivity of the monoalkylation product. The amount of dialkylation product is very small. Therefore, the product selectivity strongly depends on the manner of mixing. 

In the case of Y- or T-shaped micromixers, a decrease in the channel width to shorten mixing time leads to a decrease of production volume per unit time. To solve this problem interdigital multilamination micromixers have been developed. In this type of micromixer, two fluids are separated into many small narrow streams, which are arranged to contact each other alternately. The mixing takes place at interfaces of such sub-streams by molecular diffusion. The IMM (Institute of Microtechnik Mainz) single... 

In interdigital multilamination micromixers, the small thickness of the lamellae leads to short diffusion paths, resulting in fast mixing. Further thinning of the liquid lamellae should lead to shorter diffusion paths and faster mixing. The IMM single mixer applied this concept by shrinking the channel width in the slit. A further extension of this concept leads to the... 

Figure 7.9 Principle of a multilamination micromixer with triangular-shaped mixing...

Therefore, the observed selectivity is the disguised chemical selectivity caused by an extremely fast reaction. The reaction using a microflow system, however, gives rise to a dramatic increase in the product selectivity. The monoalkylation product was obtained in excellent selectivity and the amount of dialkylation product was very small. In this case, a solution of the N-acyliminium ion and that of trimethoxy-benzene are introduced to a multilamination-type micromixer at —78°C and the product solution leaving the device was immediately quenched with triethylamine in order to avoid the consecutive reactions. Extremely fast 1 1 mixing using the micromixer and efficient heat transfer in the microflow system seem to be responsible for the dramatic increase in the product selectivity. 

However, the use of a microflow system composed of a multilamination micromixer and a microtube reactor gives rise to a significant increase in the yield of the cycloadduct (79%) at the expense of the amount of the polymer (ca. 20 % based on styrene). The fast and efficient 1 1 mixing by a micromixer seems to be responsible. The extremely fast mixing might cause the cationic product to be formed at a very low concentration of styrene, which leads to the effective formation of the neutral cycloadduct. Similar mixing effects have also been observed for p-chloro- and p-methylstyrenes. 

Cha et al. [68] presented a novel micromixer design relying on a concept not far from that of the multilamination mixer, named a chessboard mixer. The mixer was able to complete the mixing in only 1.400 mm and the author claimed that the flow rate can be increased easily by using different arrays without affecting the performance (Fig. 3c). 

A further interesting concept for the creation of multilaminated streams is that applied in circular micromixers [69, 80, 81]. Circular micromixers rely on the formation of a vortex due to the self-rotation of the fluid stream injected in a quasitangential orientation to the circular mixing chamber (Fig. 3d). Excellent... 

Lastly, StarLaminators are devices based on a multilamination concept and are capable of high liquid throughput up to 1,000 Lh [56, 82, 83], The mixing is provided by a stack of plates with star-like openings that leads to turbulent flow, which causes mixing by formation of eddies. 

The effects of mixing in radical polymerization of MMA are interesting [168]. The use of a 5 mm static mixer leads to fouling in the reactor. In contrast, the use of an interdigital multilamination micromixer with 36 lamellae of 25 pm thickness results in a reduction in fouling. This numbering-up approach enables production of 2,000 tons per year without the fouling problem [169]. 

Continuous nitroxide-mediated block copolymerization of n-butyl acrylate (first monomer) and styrene (second monomer) can be performed using two serial 900-p m inner diameter stainless steel microtube reactors (Fig. 29) [215]. For the second polymerization process, the influence of mixing was examined by changing micromixers. The use of a high-pressure interdigital multilamination micromixer (HPIMM) provided by the Institut fiir Mikrotechnik Mainz (Mainz, Germany), can significantly reduce the polydispersity index = 1.36, 120°C) compared... 

Figure 3.18 Multilamination mixer focusing a multitude of fluid streams through an inlet chamber into a narrow mixing channel. Alternating fluid inlets are distributed over a circular-arc-shaped manifold.

Yoshida et al. also demonstrated the effect of mixing on alkylation yields and selectivity by using an efficient multilamination micromixer (supplied by IMM channel width = 25 pm) and a T-mixer (500 pm). 

Adeosun J, Lawal A (2010) Residence-time distribution as a measure of mixing in T-junction and multilaminated/elongational flow micromixers. Chem Eng Sci 65(5) 1865-1874... 

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