Microreactor microtube

A microstructured fluidic device that is used for conducting chemical reactions is called a microreactor. A microreactor is a reactor containing microstructures for chemical reactions. The size of the microstructure inside a microreactor usually ranges from several micrometers to several hundred micrometers. Various types of microstructured fluidic devices, such as microchip reactors and microtube reactors, have been developed for chemical reactions. Micromixers often serve as microreactors because reactions take place immediately after mixing. In some cases, external energies, such as thermal, photo, and electric energies, are provided in the microspace to promote the chemical reactions. For such purposes, special microreactors have been developed. 

Microreactors containing a solid-supported organic catalyst have also been developed. For example, solid-supported l,5,7-triazabicyclo-[4.4.0] undec-3-ene is introduced to a microtube reactor (Figure 7.26).This packed-bed microreactor has been used for Knoevenagel condensation... 

The shell and tube microreactor shown in Figure 10.10 has been developed to increase the throughput. This is an internal numbering-up approach because the reactor is composed of 94 microtubes (stainless steel, inner diameter 510/zm, length 600 mm) in a shell (inner diameter 60 mm, length 600 mm). The total volume of all the microtubes is 9.6 ml. The shell is divided into two sections. Hot oil is introduced into the first part of the shell (length 500 mm), and a coolant is introduced into the second part (length 100 mm). 

Fig. 4 Flow microreactor system for controlledAiving cationic polymerization of vinyl ether initiated by SnCL. M interdigital multilamination micromixer, R microtube reactor...

Fig. 5 Flow microreactor system for polymerization of vinyl ether initiated by Af-acyliminium ion (cation pool). Ml, M2 micromixers Rl, R2 microtube reactors...

Fig. 8 Flow microreactor system for cationic polymerization of 1,4-diisopropenylbenzene initiated by TfOH. M T-shaped micromixer, /f microtube reactor...

Fig. 14 Flow microreactor system for anionic polymerization of styrene in cyclohexane at 80°C initiated by s-BuLi. M T-shaped micromixer R microtube reactor...

The livingness of the reactive carbanionic polymer end is important for producing end-functionalized polymers and block copolymers. The livingness of the polymer end in a flow microreactor system can be verified as shown in Fig. 17. Solutions of an aUcyl methacrylate and of 1,1-diphenylhexyllithium are mixed in the first micromixer (Ml in Fig. 17) and the polymerization is carried out in the first microtube reactor (Rl in Fig. 17). Then, a solution of the same monomer is introduced at the second micromixer (M2), which is connected to the second micrombe reactor (R2) where the sequential polymerization takes place. By changing the length of Rl with a fixed flow rate, the effect of the residence time in Rl can be examined. The M increases by the addition of the second monomer solution. However, an increase in the residence time in Rl causes an increase in the MJM, presumably because of decomposition of the polymer end (Fig. 18). By choosing an appropriate residence time in Rl (2.95 s for MMA 0.825 s for BuMA), the sequential polymerization can be... 

Fig. 27 Continuous flow microreactor system for nitroxide-mediated radical polymerization (NMP) of poly(styrene) or poly(n-butyl acrylate). R microtube reactor...

Fig. 32 Flow microreactor system consisting of a polydimethylsiloxane (PDMS) multilayered laminar micromixer and PTFE microtubes for polymerization of amino acid A-carboxyanhydride (NCA) initiated by triethylamine...

Ziegler-Natta polymerization [241,242] is an important method of vinyl polymerization because it allows synthesis of polymers of specific tacticity. As reported by Santos and Metzger, Ziegler-Natta polymerization can be carried out in a flow microreactor system coupled directly to the electrospray ionization (ESI) source of a quadrapole time-of-flight (Q-TOF) mass spectrometer (Fig. 37) [243]. In the first micromixer (Ml), a catalyst (CP2Z1O2/MAO) and a mmiomer solution are mixed continuously to iiutiate the polymerization. The polymerization occurs in a microtube reactor. The solution thus obtained is introduced to the second micromixer (M2), where the polymerization is quenched by acetonitrile. The quenched solution is fed directly into the ESI source. The transient cationic species... 

For butyl acrylate (BA), the molecular weight distribution was found to be narrower than that for the batch reactor, as can be seen in Figure 12.5. The PDI for this polymer is then lower in the microreactor system (Table 12.1). The difference was smaller but still noticeable for benzyl methacrylate (BMA) and methyl methacrylate (MMA) and almost zero for vinyl benzoate (VBz) and styrene (St) (Table 12.2). The authors claimed that the observed results are directly related to the superior heat transfer ability of the microtube reactor. The more exothermic the polymerization reaction. 

Micromrxers in conjunction with serial microreactors can also be used effectively for LRP reactions, particularly for mixing viscous living polymer melts with non-viscous monomer for block copolymer production. For example, poly(n-butyl acrylate) can be synthesized in a microtube reactor via an N M P reaction, then the viscous homopolymer melt can be efficiently mixed with low-viscosity styrene monomer via a micromixer [90]. This can then be followed by N M P of the styrene on to the poly (w-butyl acrylate) chains in a second microtube reactor, thus creating a block copolymer. This technique gives a narrower molecular weight distribution product than comparable batch reactions. 

A microreactor that contains a number of different catalysts fixed in different compartments connected via a microfluidic network or reactor modules connected by microtubing may well be the optimal chemical production unit. Each compartment may operate simultaneously, which leads to efficient use of the microreactor. Different combinations of steps in cascade reactions may give a whole range of products (Fletcher et al., 2002 Song et al., 2003). 

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