Reactor micromixer-tube

Lob P, Lowe H, Hessel V, Hubbard SM, Menges G, Balon-Burger M (2006b) Determination of temperature profile within continuous micromixer-tube reactor used for the exothermic addition of dimethyl amine to acrylonitrile and an exothermic ionic liquid synthesis. In Proceedings of AIChE Spring National Meeting, Orlando, 23-27 April, 2006... 

Axiva in Frankfurt, Germany (now Siemens-Axiva), performed the radical solution polymerization of acrylate resins using micromixer-tube reactors [42]. 

The corresponding semibatch process is a rather slow reaction at 90 °C with simultaneous exothermic decomposition of DAST. Thus, the processed volume is restricted to laboratory scale (< 11) [ 50]. The transfer to production in a stirred tank is prohibited because of these safety reasons. A micromixer-tube reactor approach was chosen using the convective-flow-driven bas-relief caterpillar micromixer and tubes with diameters of 1-5 mm and lengths up to 20 m, respectively, and tube reactor volumes up to 500 ml (see Figure 5.16). 

Micromixer-tube reactor plants have been employed both at laboratory and pilot-scale [30]. For initial process development, a triangular ( focusing ) interdigital micromixer was used (Fig. 6.18), while for the pilot scale-out a caterpillar mixer was connected to four tubes of different hydraulic diameter by a five-port valve. 

A triangular interdigital or a caterpillar micromixer followed by a tube were used (Fig. 6.30) [45]. The micromixer-tube reactor was submersed into a thermostat bath for temperature setting. The temperature was set to -10 °C to room temperature. Piston and HPLC pumps fed the bromine and aromatic flows, respectively. The use of bromine demands special materials that are stable under such harsh conditions. Fluorinated reactor materials like PVDF or glass turned out to be suitable. 

Fork-like chip micromixer - tube reactor and other micromixers This split-recombine type of reactor has fork-like segments which are machined on a silicon plate by micromachining. As in other micromixers. this mixing unit is coimected to conventional tube for residence time enhancement reasons... 

In Fig. 7, the mixture fractions in each environment and l2 are shown. By definition of the inlet conditions, in the inlet tubes — 0 and 2 = 1. The variations away from the inlet values represent the effect of micromixing. For example, if we set y — 0 in Eqs. (36) and (37) to eliminate micromixing, then and 2 would remain at their inlet values at all points in the reactor. Note that the spatial distributions of 1 and %2 are antisymmetric with respect to the vertical axis (as would be expected from the initial conditions.) In the outlet tube, and 2 are very near the perfectly micromixed value of 1/2. Finally, by comparing Fig. 6 and Fig. 7, we can observe that macromixing occurs slightly faster than micromixing in this reactor (i.e.,pn are closer to their outlet values than are .)... 

Stainless steel is the material of choice for process chemistry. Consequently, stainless steel microreactors have been developed that include complete reactor process plants and modular systems. Reactor configurations have been tailored from a set of micromixers, heat exchangers, and tube reactors. The dimensions of these reactor systems are generally larger than those of glass and silicon reactors. These meso-scale reactors are primarily of interest for pilot-plant and fine-chemical applications, but are rather large for synthetic laboratories interested in reaction screening. The commercially available CYTOS Lab system (CPC 2007), offers reactor sizes with an internal volume of 1.1 ml and 0.1 ml, and modular microreactor systems (internal reactor volumes 0.5 ml to... 

Following similar trials with the formation of diarylbenzenes [63-65], the same research group has reported a multistep synthesis of photochromic diarylethenes using a microflow system that contained two linked micromixers and microreactors (MRi 2) [66]. Similarly to the previously reported linked microreactors, the reactors used in this setup were made of stainless steel tubes and T-shaped micromixers. Initial experiments were conducted in two steps in a continuous sequence to afford symmetrical octasubstitued diaryUiexafluoro cyclopentene (Scheme 29). 

With the use of a micromixer/commercial tube reactor, the synthesis of a thiourea from phenyl isothiocyanate and cyclohexylamine at 0 °C was carried out [25]. 

In a detailed process optimization study, the impact of the type of micromixers and process parameters was determined [56]. As a result, a pilot with a Toray Hi-mixer connected to a shell and tube microheat exchanger was constructed. Continuous operation for 24 h was carried out to obtain pentafluorobenzene (PFB) after protonation (92% yield). In this time, 14.7 kg of the product was produced, that is, about 5 t/a. Thus, the industrial-scale production carried out using a batch reactor (10 m3) can be replaced by adding only four microflow systems of the scale investigated. The pilot plant produces 0.5 kg in 6h continuous operation, thus about 730kg/a (see Figure 5.19). The name of the industrial company was not disclosed. 

In a microscale tubular reactor, Swern oxidations were performed between —20 and 20 °C. Mixing was performed stagewise with a series of rapid mixing functions (see Figure 5.22) [57,58]. First, dimethyl sulfoxide and trifluoroacetic anhydride were contacted in an interdigital micromixer followed by a stainless steel tube reactor Rl. After addition of the alcohol and reaction in reactor R2, the mixture was then contacted with a triethylamine solution and passed through two more reactors (R3 and R4) to complete the reaction. 

A scale-up preparation of ionic liquids is illustrative. Here the reaction of 1-methylimidazole with n-butyl bromide under solvent-free conditions is highly exothermic and prone to runaway in a batch reaction of any significant scale. However, using a flow reactor with reaction tubes between 2 mm and 6 mm diameter, fed by a micromixer with 0.45 mm channels, a continuous flow reaction at 85 °C was able to produce over... 

A numerical study of the free-radical polymerization of styrene (Scheme 6.15) compared the behavior of an interdigital micromixer with a T-junction and a straight tube [37, 48], The diffusion coefficient of the reactive species was varied to simulate the viscosity increase during a polymerization. The performance of the polymerization turned out to be largely dependent on the radial Peclet number. This dimensionless number is defined as the ratio of the characteristic time of diffusion in the direction perpendicular to the main flow to the characteristic time of convection in the flow direction (i.e., the mean residence time) and, therefore, is directly proportional to the characteristic length of the reactor. 

Fig. 6.32 Comparison of the polydispersity index (DPI) obtained in a multilamination micromixer (open symbols) and in a tube reactor (filled symbols) as a function of the radial Peclet number. (Courtesy of the Royal Society of Chemistry [48].)...

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